{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0000", "content": "Astronomy &Astrophysics A&A 658, A135 (2022)\nhttps://doi.org/10.1051/0004-6361/202141662\n\u00a9 J. M. Winters et al. 2022\nMolecules, shocks, and disk in the axi-symmetric wind of the\nMS-type AGB star RS Cancri?\nJ. M. Winters1\n, D. T. Hoai2\n, K. T. Wong1\n, W.-J. Kim3,4\n, P. T. Nhung2\n, P. Tuan-Anh2\n, P. Lesaffre5\n,\nP. Darriulat2, and T. Le Bertre6\n1Institut de Radioastronomie Millim\u00e9trique (IRAM), 300 rue de la Piscine, Domaine Universitaire, 38406 St. Martin d\u2019H\u00e8res, France\ne-mail: winters@iram.fr\n2Department of Astrophysics, Vietnam National Space Center (VNSC), Vietnam Academy of Science and Technology (VAST),\n18 Hoang Quoc Viet, Cau Giay, Ha Noi, Vietnam\n3Instituto de Radioastronom\u00eda Milim\u00e9trica (IRAM), Av. Divina Pastora 7, N\u00facleo Central, 18012, Granada, Spain\n4I. Physikalisches Institut, Universit\u00e4t zu K\u00f6ln, Z\u00fclpicher Str. 77, 50937 K\u00f6ln, Germany\n5Laboratoire de Physique de l\u2019\u00c9cole Normale Sup\u00e9rieure, 24 rue Lhomond, 75231 Paris, France\n6LERMA, UMR 8112, CNRS and Observatoire de Paris, PSL Research University, 61 av. de l\u2019Observatoire, 75014 Paris, France\nReceived 29 June 2021 / Accepted 29 November 2021\nABSTRACT\nContext. The latest evolutionary phases of low- and intermediate-mass stars are characterized by complex physical processes like\nturbulence, convection, stellar pulsations, magnetic \ufb01elds, condensation of solid particles, and the formation of massive out\ufb02ows that\ninject freshly produced heavy elements and dust particles into the interstellar medium.\nAims. By investigating individual objects in detail, we wish to analyze and disentangle the effects of the interrelated physical processes\non the structure of the wind-forming regions around them.\nMethods. We use the Northern Extended Millimeter Array to obtain spatially and spectrally resolved observations of the semi-\nregular asymptotic giant branch (AGB) star RS Cancri and apply detailed 3D reconstruction modeling and local thermodynamic\nequilibrium radiative transfer calculations in order to shed light on the morpho-kinematic structure of its inner, wind-forming\nenvironment.\nResults. We detect 32 lines of 13 molecules and isotopologs (CO, SiO, SO, SO 2, H2O, HCN, PN), including several transitions from\nvibrationally excited states. HCN, H13CN, and millimeter vibrationally excited H 2O, SO,34SO, SO 2, and PN are detected for the \ufb01rst\ntime in RS Cnc. Evidence for rotation is seen in HCN, SO, SO 2, and SiO(v=1). From CO and SiO channel maps, we \ufb01nd an inner,\nequatorial density enhancement, and a bipolar out\ufb02ow structure with a mass-loss rate of 1\u000210\u00007M\fyr\u00001for the equatorial region and\nof2\u000210\u00007M\fyr\u00001for the polar out\ufb02ows. The12CO/13CO ratio is measured to be \u001820on average, 24\u00062in the polar out\ufb02ows and\n19\u00063in the equatorial region. We do not \ufb01nd direct evidence of a companion that might explain this kind of kinematic structure, and\nexplore the possibility that a magnetic \ufb01eld might be the cause of it. The innermost molecular gas is in\ufb02uenced by stellar pulsation and\npossibly by convective cells that leave their imprint on broad wings of certain molecular lines, such as SiO and SO.\nConclusions. RS Cnc is one of the few nearby, low-mass-loss-rate, oxygen-rich AGB stars with a wind displaying both an equatorial\ndisk and bipolar out\ufb02ows. Its orientation with respect to the line of sight is particularly favorable for a reliable study of its morpho-\nkinematics. Nevertheless, the mechanism causing early spherical symmetry breaking remains uncertain, calling for additional high\nspatial- and spectral-resolution observations of the emission of different molecules in different transitions, along with more thorough\ninvestigation of the coupling among the different physical processes at play.\nKey words. stars: AGB and post-AGB \u2013 circumstellar matter \u2013 stars: mass-loss \u2013 stars: winds, out\ufb02ows \u2013\nstars: individual: RS Cnc \u2013 radio lines: stars\n1. Introduction\nMass-loss in red giants is due to a combination of stellar\npulsations and radiation pressure on dust forming in dense\nshocked regions in the outer stellar atmosphere (e.g., H\u00f6fner &\nOlofsson 2018). Even if the basic principles are understood, a\nfully consistent picture \u2013 including the role of convection, the\ntime-dependent chemistry, and a consistent description of dust\nformation \u2013 still needs to be developed. In particular, the contri-\nbution of transparent grains to the acceleration of matter close\n?NOEMA data (FITS format) are only available at the CDS via anony-\nmous ftp to cdsarc.u-strasbg.fr (130.79.128.5 ) or via http:\n//cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/658/A135to the stellar photosphere (Norris et al. 2012) still needs to be\nassessed.\nThe mechanisms shaping circumstellar environments around\nasymptotic giant branch (AGB) stars are vividly debated. Among\nthem, magnetic \ufb01elds (Matt et al. 2000; Duthu et al. 2017), bina-\nrity (Theuns & Jorissen 1993; Mastrodemos & Morris 1999;\nDecin et al. 2020), stellar rotation (Dor\ufb01 & H\u00f6fner 1996), and\ncommon-envelope evolution (Olofsson et al. 2015; Glanz &\nPerets 2018) have been considered.\nA major dif\ufb01culty is to explain the observed velocity \ufb01eld\nin axi-symmetrical sources, with larger velocities at high lati-\ntudes than at low latitudes (Hoai et al. 2014; Nhung et al. 2015b).\nAlso, recent observations of rotating structures and streams bring\nadditional conundrums (Tuan-Anh et al. 2019; Hoai et al. 2019).\nA135, page 1 of 27\nOpen Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License ( https://creativecommons.org/licenses/by/4.0 ),\nwhich permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited."}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0001", "content": "A&A 658, A135 (2022)\nWe have concentrated our efforts on two relatively close\n(d\u0018150pc) sources that show composite pro\ufb01les in CO rota-\ntional lines (Winters et al. 2003): EP Aqr (Winters et al. 2007,\nhereafter referred to as W2007), and RS Cnc (Libert et al. 2010).\nData obtained at IRAM show that these two sources have an\naxi-symmetrical structure with a low-velocity ( \u00182 km s\u00001) wind\nclose to the equatorial plane, and faster ( \u00188 km s\u00001) out\ufb02ows\naround the polar axes (Hoai et al. 2014; Nhung et al. 2015b). For\nEP Aqr, W2007 \ufb01nd a radial dependence of the density show-\ning intermediate maxima. Additional data obtained with ALMA\n(Nhung et al. 2019b; Homan et al. 2018b) reveal a spiral structure\nexplaining the earlier W2007 results.\nRS Cnc is one of the best examples of the interaction between\nthe stellar wind from an AGB star and the surrounding interstel-\nlar medium (Hoai et al. 2014). Its high declination makes RS\nCnc an ideal target for the Northern Extended Millimeter Array\n(NOEMA). Previous studies based on IRAM data show that it is\na twin of EP Aqr, but observed at a different angle, with a polar\naxis inclined at about 30\u000ewith respect to the line of sight (Libert\net al. 2010; Hoai et al. 2014; Nhung et al. 2015b). This is favor-\nable for studying polar and equatorial structures simultaneously,\nwhereas the different viewing angle between EP Aqr and RS Cnc\ncan be exploited to discriminate between different models in\nexplaining the observed composite CO line pro\ufb01les (Le Bertre\net al. 2016). In contrast to EP Aqr, technetium is detected in the\natmosphere of RS Cnc (Lebzelter & Hron 1999), proving that it\nis evolving along the thermal pulsing asymptotic giant branch\n(TP-AGB) in the Hertzsprung-Russell (HR) diagram. From a\nchemical point of view, RS Cnc is in a slightly more advanced\nevolutionary stage on the AGB, as indicated by its spectral clas-\nsi\ufb01cation as an MS star (see below) and by a higher photospheric\nratio of12C/13C (\u001835; Smith & Lambert (1986), but see Sect. 4.1\nfor an improved evaluation based on CO rotational lines from the\ncircumstellar environment).\nRS Cnc is a semi-regular variable star with periods of \u0019122 d\nand\u0019248 days (Adelman & Dennis 2005), located at a distance\nof\u0019150pc (Gaia Collaboration 2021; Bailer-Jones et al. 2021).\nIt is listed as S-star CSS 589 in Stephenson (1984) based on\nits spectral classi\ufb01cation M6S given in Keenan (1954). With\nits weak ZrO bands, its chemical type is intermediate between\nM and S (Keenan 1954). The stellar temperature is estimated\ntoT\u0003\u00193200 K and its luminosity is L\u0003\u00194950 L\f(Dumm &\nSchild 1998). From CO rotational line observations, two circum-\nstellar wind components were identi\ufb01ed: an equatorial structure\nexpanding at about 2 km s\u00001and a bipolar out\ufb02ow reaching a\nterminal velocity of vexp\u00198km s\u00001(Libert et al. 2010; Hoai\net al. 2014), carrying mass-loss rates of 4\u000210\u00008M\fyr\u00001and\n8\u000210\u00008M\fyr\u00001, respectively (see Sect. 4.1 for an improved\nvalue of the mass-loss rate derived here). Lines of12CO,\n13CO, SiO, and HI were detected from previous observations\nat millimeter (mm) and radio wavelengths (Nyman et al. 1992;\nDanilovich et al. 2015; de Vicente et al. 2016; G\u00e9rard & Le Bertre\n2003; Matthews & Reid 2007).\nNOEMA was recently equipped with the wide band cor-\nrelator PolyFiX, covering a total bandwidth of 15.6 GHz and\ntherefore offering the potential to observe several lines from\ndifferent species simultaneously. In this paper we present new\ndata obtained with NOEMA in D- and A-con\ufb01guration, com-\nplemented by short spacing observations obtained at the IRAM\n30m telescope. Observational details are summarized in Sect. 2\nand our results are presented in Sect. 3. Section 4 contains a\ndiscussion of the morphological structures and compares them\nto similar structures found in EP Aqr. Our conclusions are\nsummarized in Sect. 5.2. Observations\nNew observations of RS Cnc have been obtained in CO(2\u20131)\nwith NOEMA/WideX in the (extended) nine-antenna A-\ncon\ufb01guration in December 2016 (Nhung et al. 2018) and\nwith NOEMA/PolyFiX in the (compact) nine-antenna D-\ncon\ufb01guration during the science veri\ufb01cation phase of PolyFiX\nin December 2017 and in the ten-antenna A-con\ufb01guration in\nFebruary 2020. The WideX correlator covered an instanta-\nneous bandwidth of 3.8 GHz in two orthogonal polarizations\nwith a channel spacing of 2 MHz. Additionally, up to eight\nhigh-spectral resolution units could be placed on spectral lines,\nproviding channel spacings down to 39 kHz. WideX was decom-\nmissioned in September 2017 and replaced in December 2017 by\nthe new correlator PolyFiX. This new correlator simultaneously\ncovers 7.8 GHz in two sidebands and for both polarizations, and\nprovides a channel spacing of 2 MHz throughout the 15.6 GHz\ntotal bandwidth. In addition, up to 128 high-spectral-resolution\n\u201cchunks\u201d can be placed in the 15.6 GHz-wide frequency range\ncovered by PolyFiX for both polarizations, each providing a \ufb01xed\nchannel spacing of 62.5 kHz over their 64 MHz bandwidth.\nRS Cnc was observed with two individual frequency setups\ncovering a total frequency range of \u001932 GHz in the 1.3 mm atmo-\nspheric window (see Fig. 1). We used the two quasars J0923+282\nand 0923+392 as phase and amplitude calibrators; these were\nobserved every\u001920 min. Pointing and focus of the telescopes\nwas checked about every hour, and corrected when necessary.\nThe bandpass was calibrated on the strong quasars 3C84 and\n3C273, and the absolute \ufb02ux scale was \ufb01xed on MWC349\nand LkHa101, respectively. The accuracy of the absolute \ufb02ux\ncalibration at 1.3 mm is estimated to be better than 20%.\nIn order to add the short spacing information \ufb01ltered out by\nthe interferometer, in May and July 2020 we observed at the\nIRAM 30m telescope maps of 10by 10using the On-The-Fly\n(OTF) mode. This turned out to be necessary for the12CO(2\u2013\n1) and13CO(2\u20131) lines but was not needed for the SiO lines,\nwhose emitting region was found to be smaller than \u0018300. In the\ncase of the12CO(2\u20131) and13CO(2\u20131) lines, the interferometer\n\ufb01lters out large-scale structures that account for about two-thirds\nand three-quarters, respectively, of the total line \ufb02ux, informa-\ntion that is recovered by adding the short spacing data from the\nOTF map. A comparison of the respective line pro\ufb01les is shown\nin Fig. A.1.\nThe data were calibrated and imaged within the GILDAS1\nsuite of software packages using CLIC for the NOEMA data\ncalibration and the uvtable creation, CLASS for calibrating the\nOTF maps, and the MAPPING package for merging and subse-\nquent uv\ufb01tting, imaging, and self-calibration of the combined\ndata sets. Continuum data were extracted for each sideband of\nthe two frequency setups individually by \ufb01ltering out spectral\nlines, and then averaging over 400 MHz bins to properly rescale\ntheuvcoordinates to the mean frequency of each bin. Phase\nself-calibration was performed on the corresponding continuum\ndata. The gain table containing the self-calibration solutions was\nthen applied to the spectral line uvtables using the SELFCAL\nprocedures provided in MAPPING.\nThe resulting data sets were imaged applying either natu-\nral weighting, or, on the high-signal-to-noise (S/N) cubes, by\napplying robust weighting with a threshold of 0.1 to increase\nthe spatial resolution by typically a factor 2. The resulting\ndirty maps were then CLEANed using the Hogbom algorithm\n(H\u00f6gbom 1974).\n1https://www.iram.fr/IRAMFR/GILDAS\nA135, page 2 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0002", "content": "J. M. Winters et al.: Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri\nTable 1. Properties of the combined data sets for all detected lines.\nLine Frequency Eu=k Peak \ufb02ux FWHP beam size PA 1 \u001bnoise vel.res Comments(a)\n(GHz) (K) (Jy) (arcsec) (arcsec2) (deg) (mJy beam\u00001) ( km s\u00001)\n12CO(2\u20131) 230.538000 16.6 53.971 \u000610.841 6.16\u00060.01 0.48\u00020.30 36 2.88 0.5 A+D+30m, rw\n13CO(2\u20131) 220.398684 15.9 4.693 \u00060.948 7.20\u00060.01 0.50\u00020.31 35 2.79 0.5 A+D+30m, rw\nSiO(v=0,5\u20134) 217.104919 31.3 17.464 \u00063.523 1.71\u00060.01 0.51\u00020.32 36 3.38 0.5 A+D, rw, sc\nSiO(v=1,5\u20134) 215.596018 1800.2 0.105 \u00060.025 0.19\u00060.02 0.58\u00020.43 38 1.71 1.0 A, nw, sc, Feb 2020: no maser\nSiO(v=1,5\u20134) 215.596018 1800.2 0.105 \u00060.025 0.19\u00060.02 2.10\u00021.80 0 2.71 0.5 D, nw, sc, Dec 2017: maser\nSiO(v=2,5\u20134) 214.088575 3552.1 0.013 \u00060.005 0.35\u00060.09 1.00\u00020.74 35 1.03 3.0 A+D, nw, double peak pro\ufb01le (?)\nSiO(v=0,6\u20135) 260.518009 43.8 23.906 \u00064.817 1.62\u00060.01 0.43\u00020.26 32 3.39 0.5 A+D, rw, sc\nSiO(v=1,6\u20135) 258.707324 1812.7 0.168 \u00060.038 0.11\u00060.01 0.60\u00020.42 26 1.96 1.0 A+D, nw, sc\n29SiO(v=0,5\u20134) 214.385752 30.9 5.372 \u00061.083 1.19\u00060.01 0.52\u00020.32 37 1.12 3.0 A+D, rw, sc\nSi17O(v=0,6\u20135) 250.744695 42.1 0.340 \u00060.076 0.88\u00060.04 1.90\u00021.50 36 4.15(b)3.0 D, nw, sc tentative identi\ufb01cation\n29Si17O(v=0,6\u20135) 247.481525 41.6 0.020 \u00060.008 0.73\u00060.44 1.90\u00021.50 26 2.10 3.0 D, nw, sc, tentative detection\nSO(5(5)\u20134(4)) 215.220653 44.1 0.455 \u00060.093 0.79\u00060.01 0.51\u00020.32 36 1.16 3.0 A+D, rw, sc\nSO(6(5)\u20135(4)) 219.949442 35.0 0.634 \u00060.130 0.80\u00060.01 0.50\u00020.31 36 1.17 3.0 A+D, rw, sc\nSO(6(6)\u20135(5)) 258.255826 56.5 0.870 \u00060.178 0.74\u00060.01 0.43\u00020.27 32 1.59 3.0 A+D, rw, sc\nSO(7(6)\u20136(5)) 261.843721 47.6 1.168 \u00060.238 0.78\u00060.01 0.43\u00020.26 32 1.38 3.0 A+D, rw, sc\n34SO(6(5)\u20135(4)) 215.839920 34.4 0.030 \u00060.009 0.92\u00060.11 0.91\u00020.80 69 0.86 3.0 A+D, nw\n34SO(5(6)\u20134(5)) 246.663470 49.9 0.026 \u00060.009 0.93\u00060.14 0.69\u00020.48 26 0.99 3.0 A+D, nw\nSO2(16(3,13)\u201316(2,14)) 214.689394 147.8 0.021 \u00060.006 0.50\u00060.06 0.90\u00020.68 37 1.06 3.0 A+D, nw, sc\nSO2(22(2,20)\u201322(1,21)) 216.643304 248.4 0.023 \u00060.007 0.38\u00060.05 0.89\u00020.67 36 1.11 3.0 A+D, nw, sc\nSO2(28(3,25)\u201328(2,26)) 234.187057 403.0 0.022 \u00060.006 0.19\u00060.05 0.71\u00020.56 46 1.28 3.0 A+D, nw, sc\nSO2(14(0,14)\u201313(1,13)) 244.254218 93.9 0.043 \u00060.011 0.43\u00060.03 0.69\u00020.49 27 1.00 3.0 A+D, nw, sc\nSO2(10(3, 7)\u201310(2, 8)) 245.563422 72.7 0.025 \u00060.007 0.36\u00060.04 0.69\u00020.49 28 1.00 3.0 A+D, nw, sc\nSO2(15(2,14)\u201315(1,15)) 248.057402 119.3 0.015 \u00060.005 0.26\u00060.06 0.69\u00020.48 27 1.07 3.0 A+D, nw, sc\nSO2(32(4,28)\u201332(3,29)) 258.388716 531.1 0.020 \u00060.006 0.21\u00060.04 0.63\u00020.45 25 1.10 3.0 A+D, nw, sc\nSO2( 9(3, 7)\u2013 9(2, 8)) 258.942199 63.5 0.026 \u00060.008 0.49\u00060.05 0.64\u00020.45 26 1.08 3.0 A+D, nw, sc\nSO2(30(4,26)\u201330(3,27)) 259.599448 471.5 0.022 \u00060.005 0.12\u00060.03 0.63\u00020.45 25 1.03 3.0 A+D, nw, sc\nSO2(30(3,27)\u201330(2,28)) 263.543953 459.0 0.019 \u00060.006 0.16\u00060.04 0.61\u00020.42 26 1.25 3.0 A+D, nw, sc\nSO2(34(4,30)\u201334(3,31)) 265.481972 594.7 0.020 \u00060.006 0.19\u00060.04 0.61\u00020.42 26 1.27 3.0 A+D, nw, sc\nH2O(v2=1,5(5,0)\u20136(4,3)) 232.686700(c)3462.0 0.029\u00060.007 unresolved 0.71 \u00020.57 47 1.17 3.0 A+D, nw, sc, JPL\nH2O(v2=1,7(7,0)\u20138(6,3)) 263.451357(d)4474.7 0.021\u00060.005 unresolved 0.61 \u00020.42 26 1.17 3.0 A+D, nw, sc, JPL\nHCN(3\u20132) 265.886434 25.5 1.116 \u00060.234 0.76\u00060.01 0.42\u00020.26 32 4.80 0.5 A+D, rw, sc\nH13CN(3\u20132) 259.011798 24.9 0.041 \u00060.011 0.71\u00060.05 0.64\u00020.45 26 0.95 3.0 A+D, nw, sc\nPN(N=5\u20134,J=6\u20135) 234.935694 33.8 0.028 \u00060.009 0.80\u00060.10 0.70\u00020.56 47 1.00 3.0 A+D, nw, sc\nNotes. Line frequencies and upper level energies are from the CDMS (M\u00fcller et al. 2005), unless otherwise stated. The quoted \ufb02ux uncertainties\ninclude the rms of the \ufb01ts and the absolute \ufb02ux calibration accuracy of 20%, the uncertainties quoted for the source sizes refer to the rms errors\nof the Gaussian \ufb01ts (see text).(a)A: NOEMA A-con\ufb01guration, D: NOEMA D-con\ufb01guration, 30 m: short spacing data, rw: robust weighting, nw:\nnatural weighting, sc: self-calibrated, JPL: Spectral line catalog by NASA/JPL (Pickett et al. 1998).(b)Increased noise at band edge.(c)Belov et al.\n(1987).(d)Pearson et al. (1991).\nThe beam characteristics and sensitivities of the individual\ncombined data sets from A- and D-con\ufb01guration (and including\nthe pseudo-visibilities from the OTF maps, where appropriate)\nare listed in Table 1 for all detected lines.\n3. Results\nThe PolyFiX data, covering the frequency ranges 213\u2013221 GHz\n(setup1, LSB), 228-236 GHz (setup1, USB), 243\u2013251 GHz\n(setup2, LSB), and 258\u2013266 GHz (setup2, USB) with two setups\n(see Fig. 1), showed different lines of CO and SiO, and, for the\n\ufb01rst time, many lines of species like SO, SO 2, HCN, and PN and\nsome of their isotopologs. Furthermore, the data con\ufb01rmed the\nH2O line at 232.687 GHz already detected serendipitously withWideX in 2016, with a second H 2O line at 263.451 GHz seen for\nthe \ufb01rst time in RS Cnc.\nAll lines covered by the same setup (1 or 2, see Fig. 1) share\nthe same phase-, amplitude-, and \ufb02ux calibration. All 32 detected\nlines are listed in Table 1.\n3.1. Continuum\nFigure 2 shows the continuum map from A-con\ufb01guration only,\nusing robust weighting to increase the spatial resolution to\n0:3900\u00020:2200at PA 28\u000e. After self-calibration, S/N = 492 is\nobtained. The continuum source is unresolved, a point source\n\ufb01t results in a \ufb02ux at \u0019247 GHz of 23.65 \u00064.7 mJy (where the\nquoted error accounts for the accuracy of the absolute \ufb02ux cali-\nbration of 20%) and a source position at RA = 09:10:38.780 and\nA135, page 3 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0003", "content": "A&A 658, A135 (2022)\nFig. 1. Overview of the frequency ranges observed with PolyFiX using two spectral setups (setup1: red and setup2: blue, respectively). Lower\ndiagrams : zoom onto the individual spectra covering 7.8 GHz each. Upper row : setup1, lower row : setup2. The central 20 MHz at the border\nbetween inner and outer baseband are blanked out, i.e., set to zero, as this region is contaminated by the LO2 separation of the 8 GHz-wide IF in\nthe IF processor (\u201cLO2 zone\u201d).\nDec = 30:57:46.62 in February 2020. All line data cubes dis-\ncussed in the remainder of this paper are re-centered on this\ncontinuum position.\nThe source position is offset from the J2000 coordinates by\n\u00000.2600in RA and by\u00000.6800in Dec, consistent with the proper\nmotion of RS Cnc ( \u000010.72 mas yr\u00001in RA and\u000033.82 mas yr\u00001\nin Dec, Gaia Collaboration 2021; Bailer-Jones et al. 2021). From\nthe PolyFiX data, spanning a total frequency range of about\n53 GHz, we determine a spectral index of 1.99 \u00060.09 for RS Cnc\nin the 1 mm range, which is fully consistent with a black body\nspectrum of the continuum (see also Libert et al. 2010).\n3.2. Detected molecules and lines\nWithin the total frequency coverage of about 32 GHz, we detect\n32 lines of 13 molecules and isotopologs, including several tran-\nsitions from vibrationally excited states. All these lines are listed\nin Table 1 and are presented in the following sections. The peak\n\ufb02ux and FWHP of the line-emitting regions, as listed in Table 1,are determined by circular Gaussian \ufb01ts in the uv-plane to the\ncentral channel (if the source is (partially) spatially resolved) or\nby point-source \ufb01ts to the central channel (if the source is unre-\nsolved). All line pro\ufb01les shown in the following sections in Fig. 3\nand Figs. 5 through 14 are integrated over square apertures whose\nsizes are given in each \ufb01gure caption. Two-component pro\ufb01les\nare seen in CO and13CO only, and not in any other of the lines\ndetected here.\nWe looked for but did not detect the vibrationally excited\n12CO(v=1, 2\u20131) line, nor do we detect C18O(2\u20131), result-\ning in 3\u001bupper limits for the line peaks of 6 mJy beam\u00001and\n3 mJy beam\u00001, respectively (the12CO(v=1, 2\u20131) line was not\ncovered in our A-con\ufb01guration data).\n3.2.1. CO\nThe pro\ufb01les of12CO(2\u20131),13CO(2\u20131) (see Fig. 3), and12CO(1\u2013\n0) (see Libert et al. 2010) show a very distinct shape composed\nof a broad component that extends out to vlsr;\u0003\u00068 km s\u00001and\nA135, page 4 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0004", "content": "J. M. Winters et al.: Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri\nFig. 2. Continuum map around 247 GHz from A-con\ufb01guration. Con-\ntours are plotted in 100 \u001bsteps, where 1 \u001bis 47.6 \u0016Jy beam\u00001. The\nsynthesized beam is indicated in the lower left corner.\nFig. 3. CO line pro\ufb01les, showing a two-component structure. Left:\n12CO(2\u20131). Right :13CO(2\u20131). A-con\ufb01guration and D-con\ufb01guration are\nmerged, OTF data are added, and the spectral resolution is 0.5 km s\u00001.\nThe CO emission is integrated over the central 2200\u00022200, i.e., over the\nfull \ufb01eld of view of the NOEMA antennas at 230 GHz.\nFig. 4. Sketch of the geometrical structure of the wind components as\ninferred from the current data (see Sect. 4.1). The sketch is not to scale:\nthere is a smooth transition between the equatorial enhancement and the\npolar out\ufb02ows.\na narrow component indicating velocities of \u00062 km s\u00001with\nrespect tovlsr;\u0003=7km s\u00001. Velocity-integrated intensity maps of\nCO are shown in Fig. 18, indicating a clear kinematic structure\nin the north\u2013south direction. In Fig. 4, we present a schematic\nrepresentation of the geometrical structure of RS Cnc as implied\nby the data; see Sect. 4.1. The CO emitting region is spatially\nextended, consisting of a dense equatorial structure that corre-\nsponds to the low-velocity expansion and an inclined, bipolar\nFig. 5. Pro\ufb01les of SiO ground-state and \ufb01rst vibrationally excited state\nlines. Left: SiO(6\u20135): upper :v=1,lower :v=0. A-con\ufb01guration and D-\ncon\ufb01guration merged. Right : SiO(5\u20134): upper :v=1, D-con\ufb01guration\n(black) and A-con\ufb01guration (red), lower :v=0, A-con\ufb01guration and D-\ncon\ufb01guration merged. The spectral resolution is 1 km s\u00001for (v=1) and\n0.5 km s\u00001for the (v=0) lines, respectively. The emission is integrated\nover the central 500\u0002500aperture.\nstructure corresponding to an out\ufb02ow at a projected velocity\nof 8 km s\u00001. These structures were discussed in Hoai et al.\n(2014) based on Plateau de Bure data obtained on12CO(2\u20131)\nand12CO(1\u20130) that had a spatial resolution of about 100. The\nmodel built by these latter authors was later re\ufb01ned by Nhung\net al. (2018) based on12CO(2\u20131) data obtained with the WideX\ncorrelator in NOEMA\u2019s A-con\ufb01guration, providing a spatial res-\nolution of 0:4400\u00020:2800. Nhung et al. (2018) \ufb01nd a position\nangle of the projected bipolar out\ufb02ow axis of !=7\u000e(measured\ncounter-clockwise from north) and an inclination angle of the\nout\ufb02ow axis with respect to the line of sight of i=30\u000e. The CO\ndistribution is further investigated in Sect. 4.1 below.\nSuch a structure had already been found in the S-type star \u00191\nGru (Sahai 1992), which was later con\ufb01rmed by higher spatial\nresolution observations using ALMA (Doan et al. 2017). This\nobject has a G0V companion (Feast 1953) and possibly a sec-\nond, much closer companion (Homan et al. 2020). In Hoai et al.\n(2014), we reported for RS Cnc the possible presence of a com-\npanion seen in the12CO(1\u20130) channel maps at velocities around\n6.6 km s\u00001and located about 100west-northwest of the contin-\nuum source. The new data allow for a more detailed study of this\nfeature, which is presented in Sect. 4.1.\n3.2.2. SiO\nWe detect a suite of28Si16O (henceforth SiO) transitions, includ-\ning the vibrational ground-state lines of SiO(5\u20134) and SiO(6\u20135),\nthe \ufb01rst and second vibrationally excited state of SiO(5\u20134), and\nthe \ufb01rst vibrationally excited state of SiO(6\u20135). All SiO pro-\n\ufb01les are shown in Figs. 5 and 6. The spatial region emitting the\nvibrational ground-state lines extends out to about 200from the\ncontinuum peak (see Table 1, Fig. 18, and Sect. 4.2). Interest-\ningly, we detect a strong maser component on the SiO( v=1,\nJ=5\u20134) line at vlsr\u001914km s\u00001in the data obtained in\nDecember 2017, which had completely disappeared when we\nre-observed RS Cnc in February 2020 (see Fig. 5). Such behav-\nior is well known for pulsating AGB stars, and lends support to\nA135, page 5 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0005", "content": "A&A 658, A135 (2022)\nFig. 6. Pro\ufb01le around the SiO( v=2,J=5\u20134) line frequency. A-\ncon\ufb01guration and D-con\ufb01guration merged. The spectral resolution is\n1 km s\u00001and the emission is integrated over the central 100\u0002100aperture.\nthe idea that the SiO masers are excited by infrared pumping as\nopposed to collisional pumping (see, e.g., Pardo et al. 2004).\nThe SiO(v=2,J=5\u20134) line is detected above the 3 \u001blevel\nof 3 mJy beam\u00001over a broad range of Doppler velocities from\nat least\u00005 to 18 km s\u00001(Fig. 6). Given its high excitation energy\n(\u00183500 K), we expect this line to trace exclusively the inner-\nmost region around RS Cnc, as was the case in oCet, where\nSiO(v=2) absorption and emission was spatially resolved by\nALMA (Wong et al. 2016). Its broad line width suggests that\nit may trace the same high-velocity wings seen in other detected\nSiO lines (Sect. 3.3). However, our detection is too weak to allow\nfor a detailed study of the morpho-kinematics of the emission.\nAt the upper edge of the LSB of setup 2 at 250.744 GHz,\nwe serendipitously detect a strong line that we identify as\nground-state Si17O(6\u20135) at 250.7446954 GHz (M\u00fcller et al.\n2013) from the Cologne Database of Molecular Spectroscopy\n(CDMS2, M\u00fcller et al. 2005); the pro\ufb01le is shown in Fig. 7. This\nline and other transitions of Si17O have already been detected\nin a number of well-studied objects, such as the S-type star\nW Aql (De Beck & Olofsson 2020), the M-type star R Dor\n(De Beck & Olofsson 2018), and the evolved, high-mass-loss-\nrate oxygen-rich star IK Tau (Velilla Prieto et al. 2017). No\nother Si17O transitions are covered in our setups, but there is a\nhighly excited H 2O line at 250.7517934 GHz ( v2=2,J(Ka;Kc)=\n9(2,8)\u20138(3,5); Eu=k=6141 K) listed in the JPL catalog3and pre-\ndicted by Yu et al. (2012) from the Bending-Rotation approach\nanalysis. If the detected line was H 2O emission, it would be\nredshifted from the systemic velocity by about 9 km s\u00001. As indi-\ncated by the modeling of Gray et al. (2016), the 250.752 GHz\nline may exhibit strong maser action in regions of hot gas\n(Tkin=1500 K) with cool dust ( Td\u00141000 K). While we can-\nnot unequivocally exclude some contamination from a potential\nnew, redshifted H 2O maser, we consider Si17O a more likely\nidenti\ufb01cation of the 250.744 GHz emission. From the respective\nintegrated line intensities of Si16O(6\u20135) and Si17O(6\u20135), which\nare\u0018163 Jy km s\u00001and\u00183 Jy km s\u00001, and taking the difference\nof the Einstein coef\ufb01cients of the transitions into account, we\nestimate the isotopolog ratio16O/17O\u001850, assuming equal exci-\ntation conditions for both transitions and optically thin emission\nof both lines. This value is much lower than the solar isotopic\nratio of\u00182700 (Lodders et al. 2009) due to dredge-up events\n(Karakas & Lattanzio 2014; Hinkle et al. 2016) and is broadly\nconsistent with those obtained in the M-type star R Dor and the\nS-type star W Aql (61\u201374; De Beck & Olofsson 2018, 2020).\nThe initial mass of RS Cnc is about 1:5M\f(Libert et al. 2010)4,\n2https://cdms.astro.uni-koeln.de\n3https://spec.jpl.nasa.gov/ftp/pub/catalog/catform.\nhtml\n4As quoted in Libert et al. (2010), the value of 1:5M\fwas esti-\nmated by Busso & Palmerini (their priv. comm.) using the FRANEC\n).Fig. 7. Line pro\ufb01les of SiO isotopologs. Upper left : pro\ufb01le of the\n247.482 GHz line, possibly29Si17O(6\u20135); D-con\ufb01guration, only. Lower\nleft: Si17O(6\u20135): D-con\ufb01guration, only (line was not covered in A-\ncon\ufb01guration). Right :29SiO(5\u20134); A-con\ufb01guration and D-con\ufb01guration\nmerged. The spectral resolution in all cases is 3 km s\u00001and the emission\nis integrated over the central 500\u0002500aperture.\nwhich is in the same range as R Dor ( 1:4M\f; De Beck &\nOlofsson 2018) and W Aql ( 1:6M\f; De Nutte et al. 2017) that\ngives a16O/17O ratio of<1000 (Hinkle et al. 2016). However,\nwe note that the oxygen isotopic ratio (16O/17O) derived from\nthe line intensity ratio is likely underestimated if the Si16O line\nis not optically thin, as has been shown in De Beck & Olofsson\n(2018), who obtained a value of \u0018400in R Dor with radiative\ntransfer modeling. Indeed, we demonstrate in Sect. 4.2 that the\nSi16O emission in RS Cnc is optically thick, especially within a\nprojected radius of \u0018100. A photospheric16O/17O ratio of 710 in\nRS Cnc (=HR 3639) was estimated by Smith & Lambert (1990)\nfrom the spectra of near-infrared overtone band transitions of\nC16O and C17O, which is probably a more realistic ratio. We\ndo not cover C17O(2\u20131) in our setups and therefore cannot give\nan independent estimate of the16O/17O ratio. As Si18O(6\u20135) and\nC18O(2\u20131) are either not covered or not detected, there is not\nenough information from our data to obtain a meaningful con-\nstraint on the initial stellar mass from oxygen isotopic ratios (e.g.\nfrom the17O/18O ratio; De Nutte et al. 2017).\nWe detect a line at 247.482 GHz at low S/N that might be\nidenti\ufb01ed as29Si17O(v=0,J=6\u20135) at 247.4815250 GHz based\non the line list by M\u00fcller et al. (2013) and used in the CDMS\n(see Fig. 7). However, in contrast to Si17O(6\u20135),29Si17O(6\u20135)\nhas never been detected; only higher-J lines of29Si17O have\nbeen tentatively detected in R Dor ( J=7\u20136 and J=8\u20137, De\nBeck & Olofsson 2018). More speci\ufb01cally, the 247.482 GHz line\nis seen with an integrated line intensity of \u00180:08Jy km s\u00001in\nour D-con\ufb01guration data only, observed in December 2017, but it\ndoes not show up in the A-con\ufb01guration data, taken in February\n2020. This may largely be due to the much reduced brightness\nstellar evolution code (Cristallo et al. 2011) and the molecular abun-\ndances determined by Smith & Lambert. Smith & Lambert (1990)\nreported oxygen isotopic ratios of16O/17O=710 and16O/18O=440 in RS\nCnc (their Table 9). The17O/18O ratio of 0.62 corresponds to an initial\nmass of 1.4\u20131.5 M\fin the comparative study of De Nutte et al. (2017),\nwho investigated the17O/18O isotopic ratio as a sensitive function of\ninitial mass of low-mass stars based on the models of Stancliffe et al.\n(2004), Karakas & Lattanzio (2014), and the FRANEC model.\nA135, page 6 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0006", "content": "J. M. Winters et al.: Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri\n).\nFig. 8. HCN line pro\ufb01les. Left: HCN(3\u20132); A-con\ufb01guration and D-\ncon\ufb01guration merged with a spectral resolution of 0.5 km s\u00001.Right :\nH13CN(3\u20132); A-con\ufb01guration and D-con\ufb01guration merged with a spec-\ntral resolution of 3 km s\u00001. The emission of both lines is integrated over\nthe central 200\u0002200.\nsensitivity in the A-con\ufb01guration, which is a factor of approxi-\nmately 15 smaller because of the smaller synthesized beam area\nrather than some variable maser action in this line. Based on\nthe D-con\ufb01guration data, the source position of the 247.482 GHz\nemission appears slightly offset toward the northwest direction\nfrom the Si17O(6\u20135) emission. Further data on29Si17O, possibly\ncovering the J=6\u20135,J=7\u20136, and J=8\u20137 transitions, would\nbe needed to draw any \ufb01rm conclusion.\n3.2.3. HCN\nWe clearly detect the HCN(3\u20132) and H13CN(3\u20132) lines; the\npro\ufb01les are displayed in Fig. 8, and velocity-integrated inten-\nsity maps of both species are shown in Fig. B.1. Both lines\nare slightly spatially resolved and a circular Gaussian \ufb01t to\nHCN(3\u20132) gives a peak \ufb02ux of 1.12 Jy and a FWHP size of 0.7600\non the merged data. To our knowledge, this is the \ufb01rst detection\nof HCN and H13CN in RS Cnc (see Sect. 4.4). From the \ufb01rst-\nmoment map (shown in Fig. 17, left), a clear velocity pattern\nis evident that indicates possible rotation in the HCN-emitting\nregion (see Sect. 3.4). Also, the velocity-integrated intensity\nmaps presented in Fig. B.1 show a clear kinematic structure in\nthe east\u2013west direction.\nFormation of the HCN molecule in oxygen-rich environ-\nments is further discussed in Sect. 4.4. A modeling using the 1D\nlocal thermodynamic equilibrium (LTE) radiative transfer code\nXCLASS (M\u00f6ller et al. 2017, see Appendix D) gives a column\ndensity for HCN in RS Cnc of N HCN=1:6\u00021015cm\u00002, cor-\nresponding to an abundance of X(HCN/H 2)=6:6\u000210\u00007. This\nvalue is well within the range found for other M- and S-type\nstars as modeled by Sch\u00f6ier et al. (2013), who \ufb01nd X(HCN/H 2)\nequal to a few times 10\u00007(for more details see Sect. 4.4 and\nAppendix D).\n3.2.4. H 2O\nThe WideX spectrum obtained in A-con\ufb01guration in Decem-\nber 2016 serendipitously revealed a line at 232.687 GHz that we\nascribe to the J(Ka,Kc)=5(5,0)\u20136(4,3) transition of o-H 2O in\nthev2=1vibrational state. The H 2O source is weak and seems\nstill unresolved within the synthesized beam of 0:500\u00020:3400\nobtained in the A-con\ufb01guration in February 2020, consistent\nwith its high upper-state energy of 3462 K. The line pro\ufb01le is\nshown in Fig. 9. With the follow-up observations employing\nPolyFiX in D-con\ufb01guration and A-con\ufb01guration we also cov-\nered and detected the 263.451 GHz o-H 2Ov2=1,J(Ka,Kc)=\n7(7,0)\u20138(6,3) line (Fig. 9, right; Eu=k=4475 K). Both lines\nare resampled to a resolution of 3 km s\u00001, data are merged\nfrom A-con\ufb01guration and D-con\ufb01guration, and the emission is\nFig. 9. H2O line pro\ufb01les. Left: H 2O line at 232.687 GHz. Right : H 2O\nline at 263.451 GHz. Data are merged from A-con\ufb01guration and D-\ncon\ufb01guration, the spectral resolution is 3 km s\u00001, and the emission of\nboth lines is integrated over the central 100\u0002100aperture.\nintegrated over an aperture of 100\u0002100. Intensity maps of both\nlines are shown in Fig. B.2, testifying to the compactness of the\nH2O-emitting region.\nThese are the \ufb01rst detections of millimeter vibrationally\nexcited H 2O emission in RS Cnc. We note that the 22 GHz\nH2O maser in the ground state was tentatively detected by\nSzymczak & Engels (1995) in one of the two epochs they cov-\nered, but the 22 GHz line is not detected in other observations\n(Dickinson et al. 1973; Lewis 1997; Han et al. 1995; Yoon et al.\n2014). RS Cnc also shows clear photospheric H 2O absorption at\n2:7\u0016m (Merrill & Stein 1976; Noguchi & Kobayashi 1993), and\nat1:3\u0016m (7500 cm\u00001; Joyce et al. 1998), although the H 2O band\nnear 900 nm is not detected (Spinrad et al. 1966).\nBoth the 232 and 263 GHz water lines have upper levels\nbelonging to the so-called transposed backbone in the v2=1\nvibrationally excited state of H 2O, that is Ka=JandKc=0or\n1 (see Fig. 1 of Alcolea & Menten 1993). The 232 GHz line was\n\ufb01rst detected in evolved stars together with the 96 GHz line from\nanother transposed backbone upper level by Menten & Melnick\n(1989) toward the red supergiant VY CMa and the AGB star\nW Hya. The latter is an M-type star with a similar mass-loss\nrate to RS Cnc. The authors \ufb01nd that the 232 GHz line emission\nin both stars may be of (quasi-)thermal nature while the 96 GHz\nline clearly showed maser action. The (unpublished) detection of\nthe 263 GHz line was mentioned in Alcolea & Menten (1993),\nwho also described a mechanism that may lead to a system-\natic overpopulation of the transposed backbone upper levels in\nthev2=1state of H 2O in the inner region of circumstellar\nenvelopes. If the vibrational decay routes (to the ground state)\nof the transposed backbone upper levels become more optically\nthick than the lower levels in the v2=1state, then differential\nradiative trapping may cause population inversion of these lines.\nAdditional vibrationally excited H 2O emission lines from trans-\nposed backbone upper levels were predicted and later detected in\nVY CMa by Menten et al. (2006) and Kami \u00b4nski et al. (2013). We\nobserved the 232 GHz line in RS Cnc at three epochs (December\n2016, December 2017, and February 2020) and the 263 GHz line\nat the latter two epochs, and the emission appears to be stable in\ntime for both lines. The pro\ufb01les appear to be very similar, both\nare broad, even broader than the (ground-state) lines of other\nspecies reported here, and there is no sign for any narrow com-\nponent in either of the two pro\ufb01les at any of the epochs. As the\nlines should arise from a region very close to the star \u2013 compat-\nible with their broad widths; see Sect. 3.3 \u2013 one might expect\nto see time variations due to the varying density and radiation\n\ufb01eld caused by the stellar pulsation, in particular if the emission\nwere caused by maser action, as seen on the SiO( v=1;5\u20134)\nline observed in December 2017 (see Fig. 5). Also, the model-\ning of Gray et al. (2016) shows only very little inversion of the\nA135, page 7 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0007", "content": "A&A 658, A135 (2022)\nFig. 10. Pro\ufb01les of the four detected SO lines, with A-con\ufb01guration\nand D-con\ufb01guration merged. The spectral resolution is 3 km s\u00001and the\nemission is integrated over the central 200\u0002200aperture.\nFig. 11. Pro\ufb01les of the two34SO lines detected here, with A-\ncon\ufb01guration and D-con\ufb01guration merged. The spectral resolution is\n3 km s\u00001and the emission is integrated over the central 200\u0002200aperture.\ninvolved level populations for the 263 GHz H 2O transition. We\ntherefore think that both lines could be thermally excited. A def-\ninite assessment of the nature of the vibrationally excited H 2O\nemission would however require some detailed modeling of the\nemission, together with high-sensitivity monitoring of the line\npro\ufb01les with high spectral resolution, possibly including other\nH2O lines from transposed backbone upper levels and/or known\nmaser lines for comparison, which is beyond the scope of the\npresent paper.\n3.2.5. SO\nFour lines of SO are detected (see Fig. 10) along with two lines of\nthe isotopolog34SO (Fig. 11). These represent the \ufb01rst detections\nof SO and34SO in RS Cnc. SO has been observed in several M-\ntype stars, including R Dor and W Hya, (Danilovich et al. 2016)),\nbut remains undetected in S-type stars (e.g., W Aql, Decin et al.\n2008; De Beck & Olofsson 2020). All SO lines detected here\nare slightly spatially resolved with a FWHP around 0:800and\ntherefore seem to be emitted from the same region as HCN.\nVelocity-integrated intensity maps of SO are shown in Fig. B.3.\nThe SO lines show the same velocity pattern (indicating rota-\ntion) as HCN, although the velocity resolution of the SO lines is\nonly 3 km s\u00001; see Fig. B.3 and the \ufb01rst-moment map in the right\npanel of Fig. 17.\nUsing the integrated line strengths of SO(6(5)\u20135(4))\nand34SO(6(5)\u20135(4)) found here ( \u00184.69 Jy km s\u00001and\n\u00180.20 Jy km s\u00001, respectively) and taking the difference of\nthe Einstein coef\ufb01cients of the transitions into account, weestimate the isotopolog ratio32SO/34SO\u001823, assuming equal\nexcitation conditions for both transitions and optically thin\nemission of both lines. This value is in good agreement with\nthe values of 21.6\u00068:5and 18.5\u00065:8derived from the radiative\ntransfer models for M-type stars by Danilovich et al. (2016,\n2020), respectively. We note that, for the S-type star W Aql,\nan Si32S/Si34S isotopolog ratio of 10.6 \u00062:6was derived by\nDe Beck & Olofsson (2020). As32S is mainly produced by\noxygen burning in massive stars and, to a lesser extent, in type\nIa supernovae, and as34S is formed by subsequent neutron\ncapture (e.g., Nomoto et al. 1984; Wilson & Matteucci 1992;\nTimmes et al. 1995; Hughes et al. 2008), the32S/34S isotopic\nratio remains virtually unaltered during AGB evolution (see, e.g.\ntables in the FRUITY5database, Cristallo et al. 2011) and there-\nfore should re\ufb02ect the chemical initial conditions of the natal\ncloud from which the star has formed. The spread in the isotopic\nratio seen among the different AGB stars mentioned above\nwould then rather be indicative of the Galactic environment in\nwhich the star has formed (see, e.g., Chin et al. 1996; Humire\net al. 2020) instead of re\ufb02ecting any evolutionary effect. For the\nlow-mass-loss-rate M-type stars R Dor and W Hya, Danilovich\net al. (2016) reproduce their observed line pro\ufb01les best with\ncentrally peaked SO (and SO 2) distributions, consistent with the\nmaps presented in Fig. B.3.\n3.2.6. SO 2\nIn SO 2, 11 lines are detected; their parameters are summarized\nin Table 2, and all pro\ufb01les are shown in Fig. C.1. These are the\n\ufb01rst detections of SO 2in RS Cnc. A previous survey with the\nIRAM 30 m telescope by Omont et al. (1993) did not detect\nSO2in RS Cnc with an rms noise of 0.052 K (or \u00180:25Jy\nat 160.8 GHz). As an example, we show the SO 2(14(0,14)\u2013\n13(1,13)) line at 244.3 GHz, only in Fig. 12. A \ufb01rst-moment\nmap of the SO 2(14(0,14)\u201313(1,13)) line is shown in Fig. 17\nin the middle left panel. Although the source remains barely\nresolved (source size \u00180:4300) by the beam ( 0:6900\u00020:4900), there\nis a signature of a rotating structure in SO 2, as was also seen\nin EP Aqr (Homan et al. 2018b; Tuan-Anh et al. 2019). Inte-\ngrated intensity maps of three SO 2lines (SO 2(9(3, 7)\u20139(2, 8)),\nwhich has the lowest upper level energy of the SO 2lines detected\nhere ( Eu=64K); SO 2(14(0,14)\u201313(1,13)), the strongest line,\nand SO 2(34(4,30)\u201334(3,31)), which has the highest upper level\nenergy of the detected lines, Eu=595K) are shown in Fig. B.4.\nAll lines show kinematic structure in the E\u2013W direction, approx-\nimately orthogonal to the out\ufb02ow structure seen in CO and SiO,\ncf. Fig. 18.\nWe derive the rotational temperature and column density\nof the SO 2-emitting region with a population diagram analysis\n(Sect. 3.6) and by an XCLASS modeling (Appendix D). Both\nmethods give a similar rotational temperature of \u0018320\u0000350K\nand a column density of \u00183:5\u00021015cm\u00002.\n3.2.7. PN\nWe detect a line at 234.936 GHz that we ascribe to the PN\nmolecule, which would be the \ufb01rst detection of PN in RS Cnc.\nPN has been detected in several M-type stars (e.g., De Beck\net al. 2013; Ziurys et al. 2018), and in the C-rich envelopes of\nIRC +10216 and CRL 2688 (Gu\u00e9lin et al. 2000; Cernicharo et al.\n2000; Milam et al. 2008). The presence of PN in an MS-type star\ntherefore does not seem to come as a surprise. However, RS Cnc\n5http://fruity.oa-teramo.inaf.it/\nA135, page 8 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0008", "content": "J. M. Winters et al.: Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri\nTable 2. Parameters of the detected SO 2lines used for the population diagram analysis.\nFrequency WI=R\nS(v)dv g ulog10(Aul) Eu=k\u0012a\u0002\u0012b\n(GHz) (Jy km s\u00001) (s\u00001) (K) (arcsec2)\n214.6894 0.141\u00060.0385 33 \u20134.0043 147.843 0.90 \u00020.68\n216.6433 0.166 \u00060.0434 45 \u20134.0329 248.442 0.89 \u00020.67\n234.1871 0.160\u00060.0439 57 \u20133.8401 403.033 0.71 \u00020.56\n244.2542 0.293 \u00060.0698 29 \u20133.7855 93.901 0.69 \u00020.49\n245.5634 0.170 \u00060.0451 21 \u20133.9240 72.713 0.69 \u00020.49\n248.0574 0.119 \u00060.0333 31 \u20134.0939 119.328 0.69 \u00020.48\n258.3887 0.153 \u00060.0396 65 \u20133.6773 531.100 0.63 \u00020.45\n258.9422 0.192 \u00060.0524 19 \u20133.8800 63.472 0.64 \u00020.45\n259.5994 0.182 \u00060.0448 61 \u20133.6835 471.496 0.63 \u00020.45\n263.5440 0.152 \u00060.0448 61 \u20133.7227 459.038 0.61 \u00020.42\n265.4820 0.168 \u00060.0448 69 \u20133.6426 594.661 0.61 \u00020.42\nNotes. Data are merged from A-con\ufb01guration and D-con\ufb01guration. Quoted errors include the rms errors of the Gaussian \ufb01ts in the uvplane and\nthe absolute \ufb02ux calibration accuracy of 20%. The SO 2line parameters are retrieved from the CDMS and are based on the calculations by Lovas\n(1985) and M\u00fcller & Br\u00fcnken (2005).\nFig. 12. Pro\ufb01le of SO 2(14(0,14)\u201313(1,13)) with A-con\ufb01guration and D-\ncon\ufb01guration merged, a spectral resolution of 3 km s\u00001, and emission\nintegrated over the central 200\u0002200aperture.\nFig. 13. Pro\ufb01le of PN( N=5\u20134,J=6\u20135) with A-con\ufb01guration and D-\ncon\ufb01guration merged, a spectral resolution of 3 km s\u00001, and emission\nintegrated over the central 200\u0002200aperture.\nappears to be the source with lowest mass-loss rate in which this\nmolecule has been reported so far. The PN line pro\ufb01le is shown\nin Fig. 13. The line is spatially resolved at 0:800, which places it\nin about the same region as HCN and SO. The \ufb01rst-moment map\nof this line also shows signatures of rotation but due to the weak-\nness of the line, the evidence is low. An integrated intensity map\nof PN is presented in Fig. B.5, showing that the line-emitting\nregion is slightly spatially resolved. The 3\u001bfeature seen about\n1:500south of the phase center should not be considered as a\ndetection but rather as a noise peak, as long as this structure is\nnot con\ufb01rmed by higher sensitivity observations.\nFig. 14. Line wings in SiO(5\u20134) and SiO(6\u20135) compared to CO(2\u20131).\nThe emission is integrated over the central 500\u0002500aperture.\nFig. 15. High velocities close to the line of sight as seen in SiO. PV\nmaps are shown in the Vzvs.Rplane for SiO(5\u20134) ( left) and SiO(6\u20135)\n(right ). The horizontal black line indicates the wind terminal velocity\nas traced in CO and the white scale bar indicates the spatial resolution.\nR=p\n(\u000eDec)2+(\u000eRA)2,jVzj=jvlsr\u0000vlsr;\u0003j:\n3.3. High-velocity wings in SiO, and in other molecules\nIn SiO, \ufb01ve lines in three different vibrational states ( v=0,1,2)\nare detected (see Figs. 5 and 6). The vibrational ground-state\nlines clearly indicate the presence of material at velocities much\nhigher than the wind terminal velocity of \u00188 km s\u00001as traced by\nCO lines at this stellar latitude (see Sect. 4.1). This is illustrated\nin Fig. 14, and in Fig. 15 where we de\ufb01ne vz=vlsr\u0000vlsr;\u0003, the\nDoppler velocity relative to the star. The high-velocity region\nis centered on the line of sight and is con\ufb01ned to the inner\n\u00190:300; see Fig. 15. A similar feature was seen in high-spatial-\nresolution observations of other oxygen-rich, low-mass-loss-rate\nA135, page 9 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0009", "content": "A&A 658, A135 (2022)\nAGB stars, such as W Hya (Vlemmings et al. 2017), EP Aqr\n(Tuan-Anh et al. 2019), oCet (Hoai et al. 2020), R Dor (Decin\net al. 2018; Nhung et al. 2019a, 2021), and in 15 out of 17 sources\nobserved in the ALMA Large Program ATOMIUM (Decin et al.\n2020; Gottlieb et al. 2022), calling for a common mechanism\ncausing high-velocity wings in this type of object. In the case\nof EP Aqr, where the bipolar out\ufb02ow axis almost coincides with\nthe line of sight (with an inclination angle of i\u001910\u000e), the high-\nvelocity wings were interpreted in terms of narrow polar jets.\nFor R Dor and oCet, which do not show obvious signs of axial\nsymmetry in their winds, such an interpretation could not be\nretained and it was argued instead that the high-velocity wings\nwere caused by (a mixture of) turbulence, thermal broadening,\nand some effect of shocks, acting at distances below some 10 to\n15 AU from the central star. The presence of broad wings in the\nSiO lines emitted from RS Cnc, whose symmetry axis is inclined\nby\u001930\u000ewith respect to the line of sight (see Sect. 4.1), lends sup-\nport to the latter type of interpretation and casts serious doubts\non the polar jet interpretation proposed earlier for EP Aqr, which\nshows a morpho-kinematics similar to that of RS Cnc (Nhung\net al. 2015b). Indeed, if the broad line widths are present regard-\nless of the orientation of a possible symmetry axis with the line\nof sight, they must be caused by a mechanism of nondirectional\n(accounting for the resolving beam) nature. A possible candi-\ndate, whose action is limited to the close vicinity of the star,\nis pulsation-driven shocks that dissipate their energy relatively\nclose to the star and imply positive and negative velocities in the\nshocked region that can be much higher than the terminal out-\n\ufb02ow velocity of the wind. Such structures could be explained\nby the B-type models discussed in Winters et al. (2000b) as\npresented in Winters et al. (2002); see their Fig. 3. Recent 3D\nmodel calculations that self-consistently describe convection and\nfundamental-mode radial pulsations in the stellar mantle would\nprovide the physical mechanism that leads to the development of\nsuch shocks close to the star surface (e.g., Freytag et al. 2017)\nand could therefore replace the simpli\ufb01ed inner boundary condi-\ntion (the so-called \u201cpiston approximation\u201d) that was used in the\nearlier 1D models mentioned above.\nIn the data presented here, wings at high Doppler velocity\nare seen in nearly all lines detected with suf\ufb01cient sensitivity\nto probe the pro\ufb01le over at least vlsr;\u0003\u000610km s\u00001. This is illus-\ntrated in Fig. 16, where vzpro\ufb01les are integrated over a circle\nof radius 0:200centered on the star. Gaussian pro\ufb01les centered\nat the origin are shown as visual references (not \ufb01ts), showing\nhow absorption produces asymmetric pro\ufb01les. A major differ-\nence is seen between vibrational ground-state lines, which have\na Gaussian FWHM of \u001810km s\u00001, and vibrationally excited-\nstate lines, which have a Gaussian FWHM of \u001814km s\u00001.\nSuch a difference is not surprising, assuming that the high-\nvelocity wings are formed in the inner layer of the circumstellar\nenvelope (CSE), which is preferentially probed by the ( v=1)\nlines. In this context, we note that Rizzo et al. (2021) recently\nreported the detection of a narrow SiO( v=1, 1\u20130) maser line\nin RS Cnc at a velocity of +14 km s\u00001with respect to the\nstar\u2019s lsr velocity. The effect of shocks on line pro\ufb01les was \ufb01rst\nobserved in the near-infrared range on CO ro-vibrational lines,\nprobing the stellar photosphere and the innermost circumstellar\nregion within\u001810R\u0003(e.g.,\u001fCyg, an S-type star, Hinkle et al.\n1982). Very-high-angular-resolution observations obtained over\nthe past decade using VLT, VLTI, and ALMA show that the\neffect of shocks from pulsations and convection cell ejections\nis con\ufb01ned within some 10 AU from the star (see, e.g., Khouri\net al. 2018; H\u00f6fner & Olofsson 2018; Ohnaka et al. 2019, and\nreferences therein). Rotation, when observed, is instead found\nFig. 16. Line pro\ufb01les of different molecules on a logarithmic intensity\nscale. Gaussian pro\ufb01les are shown for comparison, FWHM =10km s\u00001\nfor the ground-state lines of all molecules, and FWHM =14km s\u00001\nfor the (v=1) lines of SiO. All observed pro\ufb01les are integrated over\nR<0:200.\nto extend beyond this distance, typically up to \u001820 AU (e.g.,\nVlemmings et al. 2018; Homan et al. 2018a; Nhung et al. 2021).\nThe angular resolution of the present data is insuf\ufb01cient to detect\nsuch differences directly; however, the effect of rotation and\nshocks on lines of sight contained within a beam centered on the\nstar depends on the region probed by each speci\ufb01c line: lines that\nprobe the inner layers exclusively, such as the ( v=1) lines, are\nmostly affected by shocks, and somewhat by rotation; CO lines,\nfor which the probed region extends very far out, see little effects\nof rotation and even less effects of shocks because the emission\nfrom the inner envelope provides too small a fraction of the total\nemission. Between these two extremes, the relative importance\nof the contributions of shocks and rotation depends on the radial\nextent of the region probed by the line. Such an interpretation is\nconsistent with the data displayed in Fig. 16.\n3.4. Rotation\nIn Fig. 17, we present \ufb01rst-moment maps of HCN(3\u20132) (left),\nSO2(14(0,14)\u201313(1,13)) (middle left), SiO( v=1, 6\u20135) (middle\nright), and SO(7(6)\u20136(5)) (right). At projected distances from\nthe star not exceeding 0:500, all four tracers display approximate\nanti-symmetry with respect to a line at PA\u001810\u000e. This is sugges-\ntive of the presence of rotation in the inner CSE layer around\nan axis that projects on this line in the plane of the sky. Such\na morpho-kinematic structure has also been observed in other\nstars, notably R Dor (Vlemmings et al. 2018; Homan et al. 2018a;\nNhung et al. 2021). The angular resolution of the present data\ndoes not allow for a detailed exploration of this region, which\nprevents us from commenting on its possible cause. Neverthe-\nless, the anti-symmetry axis of the velocity pattern projected on\nthe plane of the sky at a PA that approximately coincides with\nthe projected symmetry axis of the polar out\ufb02ows (see Sect. 4.1)\nA135, page 10 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0010", "content": "J. M. Winters et al.: Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri\nFig. 17. First-moment maps of different lines, indicating a possibly rotating structure (see Sect. 3.4). Left: HCN(3\u20132), middle left : SO 2(14(0,14)\u2013\n13(1,13)), middle right : SiO(v=1,6\u20135), right : SO(7(6)\u20136(5)). The black ellipses indicate the synthesized beam.\nis remarkable and suggests that rotation is taking place about this\nsame polar axis in the inner CSE layer.\nThe line-of-sight velocities of these structures are small, on\nthe order of the velocities derived from CO for the equatorial\nregion, and we interpret them here as possible signs of rotation\n(rather than indicating another bipolar out\ufb02ow oriented perpen-\ndicular to the larger scale out\ufb02ow traced in CO and SiO ( v=0)\nlines). We note that out of these four lines, the HCN(3\u20132) line\nis detected with the highest S/N (S/N =233in the line peak, cf.\nTable 1).\nThe mean Doppler velocity hvzi, averaged over the inner\n0:500, of the HCN line can be \ufb01t in position angle !, measured\ncounter-clockwise from north, by\nhvziHCN=\u00000:19 km s\u00001+1:0 km s\u00001sin(!\u000019\u000e); (1)\nwhereas the SiO( v=1, 6\u20135) velocity is well \ufb01t by\nhvziSiO (v=1;6\u00005)=\u00000:37 km s\u00001+0:46 km s\u00001sin(!\u000026\u000e):(2)\nThe small offsets of \u0018\u00000:3km s\u00001on average are within\nthe uncertainty attached to the measurement of the star\u2019s LSR\nvelocity. The coef\ufb01cients of the sine terms measure the pro-\njected rotation velocity, namely the rotation velocity divided by\nthe sine of the angle made by the rotation axis with the line of\nsight. Assuming that the rotation axis is the axi-symmetry axis of\nthe CSE, this angle is i\u001830\u000e(see Sect. 4.1), meaning rotation\nvelocities of\u00182and\u00181km s\u00001for HCN and SiO respectively.\nObservations of higher angular resolution are needed to con\ufb01rm\nthe presence of rotation within a projected distance of 0:500from\nthe star and we prefer to summarize the results presented in this\nsection in the form of an upper limit to the mean rotation velocity\nof a few km s\u00001.\n3.5. Global out\ufb02ow structure traced by CO and SiO\nThe detailed structure of the morpho-kinematics of the CSE has\nbeen studied using observations of the12CO(1\u20130) and12CO(2\u20131)\nmolecular line emission. The analyses of Hoai et al. (2014) and\nNhung et al. (2015b) con\ufb01rmed the interpretation of the two-\ncomponent nature of the Doppler velocity spectrum originally\ngiven by Libert et al. (2010). The CSE is axi-symmetric about\nan axis making an angle of i\u001830\u000ewith the line of sight and\nprojecting on the plane of the sky at a position angle !\u00187\u000eeast\nof north (see also the sketch in Fig. 4). The expansion velocity\nreaches\u00188to9km s\u00001along the axis \u2013 we refer to this part of\nthe CSE as bipolar out\ufb02ow \u2013 and \u00183to4km s\u00001in the plane\nperpendicular to the axis \u2013 we refer to this part of the CSE as\nequatorial enhancement. The transition from the equator to thepoles of the CSE is smooth. Section 4.1 below, using observa-\ntions of the12CO(2\u20131) and13CO(2\u20131) molecular lines, con\ufb01rms\nand signi\ufb01cantly re\ufb01nes this picture. The right panels of Fig. 20\nshow projections of the CSE on the plane containing the axis\nand perpendicular to the plane of the sky, which give a good\nqualitative idea of the global structure.\nVelocity-integrated channel maps of the CO(2\u20131) and\nSiO(6\u20135) observations analyzed in the present article are dis-\nplayed in Fig. 18. They clearly show the bipolar out\ufb02ows,\ninclined toward the observer in the north and receding in the\nsouth. We note that the red wings are brighter than the blue\nwings as a result of absorption (see Sects. 4.1 and 4.2) The SiO-\nemitting region is seen to be signi\ufb01cantly more compact than the\nCO-emitting region; this is in conformity with observations of\nmany other oxygen-rich AGB stars and is generally interpreted\nas the result of SiO molecules condensing on dust grains and\nbeing ultimately dissociated by the interstellar radiation at some\n200 AU from the star, well before CO molecules are dissociated\n(see e.g., Sch\u00f6ier et al. 2004).\n3.6. Temperature and SO 2abundance\nIn this section, we use the 11 detected SO 2lines to derive\nan approximate temperature and column density of the SO 2-\nemitting region by means of a population diagram. Following\nGoldsmith & Langer (1999), in the optically thin case, the col-\numn density of the upper level population Nuof a transition u->l\ncan be expressed as\nNu=8\u0019k\u00172\nhc3AulZ\nTbdv: (3)\nNuis the column density of the upper level population of the\ntransition, kandhare the Boltzmann and Planck constant,\nrespectively, \u0017is the line frequency, cthe speed of light, Aulis\nthe Einstein coef\ufb01cient for spontaneous emission of the transi-\ntion, andR\nTbdvis the velocity-integrated main-beam brightness\ntemperature. The latter is converted to the surface brightness\ndistribution of the source S\u0017per beam, measured by the inter-\nferometer, by means of\nTb=\u00152\n2k\nbS\u0017; (4)\nwhere\u0015=c\n\u0017is the observing wavelength, and \nb=\u0019\u0012a\u0012b\n4 ln 2with\u0012a\nand\u0012bbeing the major and minor axis of the synthesized beam.\nWe determineR\nS(v)dv=:WIfrom a circular Gaussian \ufb01t to\nthe velocity-integrated emission in the uv-plane, where the inte-\ngration is taken from (vlsr,*\u00004:5)km s\u00001to(vlsr;\u0003+4:5)km s\u00001,\nthat is over the three central channels of the SO 2lines.\nA135, page 11 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0011", "content": "A&A 658, A135 (2022)\nFig. 18. Velocity-integrated intensity maps of the12CO(2\u20131) line ( upper row ) and the vibrational ground-state line of SiO(6\u20135) ( lower row ),\ncovering three velocity intervals. Left: blue line wing [ vlsr;\u0003\u000010,vlsr;\u0003\u00002] km s\u00001,middle : line center [ vlsr;\u0003\u00002,vlsr;\u0003+2] km s\u00001,right : red line\nwing [vlsr;\u0003+2,vlsr;\u0003+10] km s\u00001. North is up and east is to the left. We note the different color scales. Contours are plotted every 5\u001bfor CO and\nevery 20\u001bfor SiO, where ( from left to right )1\u001b=14:6;22:0;19:2mJy beam\u00001km s\u00001for CO(2\u20131) and 1\u001b=11:1;16:7;16:4mJy beam\u00001km s\u00001\nfor SiO(6\u20135). The black ellipse in the lower left corner indicates the synthesized beam.\nFig. 19. Population diagram for SO 2. The three data points in brackets\ncorrespond to the three lowest frequency SO 2lines observed with setup\n1, which, due to a different uvcoverage, resulted in a comparably larger\nbeam than the setup 2 observations (see Table 2 and Eq. (6)).\nFor the population diagram, we then get\nln Nu\ngu!\n=ln \u0010uWI\ngu!\n=ln NSO2\nQSO2;rot!\n\u0000Eu\nkT; (5)\nwhere we de\ufb01ne \u0010uas\n\u0010u=4:784\u000210\u00007\nhcAul1\n\u0012a\u0012b: (6)\nIn Eq. (5), WIis expressed in Jy\u0002km s\u00001,\u0012aand\u0012bare given\nin arcsec, Euis the upper level energy, guthe statistical weight of\nthe upper level, and Tis the excitation temperature. All relevant\nparameters of the SO 2transitions used here are listed in Table 2.In \ufb01tting a straight line to the population diagram (shown\nin Fig. 19) to determine a rotational temperature according to\nEq. (5), we assume that the SO 2level populations are dominated\nby collisions, i.e., that LTE holds for the rotational excitation\nof SO 2, and that the lines are optically thin. The assumption of\nLTE populations may be questionable for SO 2(see Danilovich\net al. 2016), and essentially could result in underestimation of\nthe kinetic gas temperature in the SO 2-emitting region (cf. the\ndiscussion in Goldsmith & Langer 1999, their Sect. 5). The effect\non the derived column density is more dif\ufb01cult to assess without\na detailed non-LTE modeling. However, we note that our result is\nconsistent with the SO 2abundance derived for similar objects by\nmeans of a comprehensive non-LTE description (see below). On\nthe other hand, the assumption that the lines are optically thin is\njusti\ufb01ed by the results of our XCLASS modeling; see below and\nAppendix D.\nWith the temperature of T\u0019320K resulting from a lin-\near \ufb01t to the population diagram shown in Fig. 19, we get\nthe partition function QSO2;rot(interpolated from values given\nin the CDMS), from which an effective SO 2column density\nofNSO2=3:5\u00021015cm\u00002is determined by means of Eq. (5).\nThe SO 2source is compact (see Table 1 and Fig. B.4, FWHP\n\u00190:500, corresponding to 75 AU, or \u001970R\u0003), which is consistent\nwith the estimated temperature in this inner (possibly rotating)\nregion. Assuming a mass-loss rate of 1\u000210\u00007M\fyr\u00001in the\nequatorial region (cf. Sect. 4.1), an out\ufb02ow velocity of at max-\nimum 8 km s\u00001as indicated by the line widths (but excluding\nthe high-velocity wings discussed in Sect. 3.3), an inner radius\nof\u00191014cm, and an outer radius of that region of \u00191015cm,\ncorresponding to 0:500, we estimate upper limits of the SO 2\nabundance of X(SO 2=<H>) = 7:3\u000210\u00007, or, if hydrogen were\ncompletely bound in H 2,X(SO 2/H2) =1:5\u000210\u00006. For compari-\nson, Danilovich et al. (2016) \ufb01nd an SO 2abundance of\u00185\u000210\u00006\nfor the low-mass-loss-rate ( \u00181\u20132\u000210\u00007M\fyr\u00001) oxygen-rich\nstars R Dor and W Hya, about a factor of approximately 3higher\nthan the value found here for the MS-type star RS Cnc. We note\nA135, page 12 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0012", "content": "J. M. Winters et al.: Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri\nFig. 20. CO data and 3D reconstruction. Left panels : \ufb02ux density averaged over 0:400<R<2:500in thevzvs.!plane for12CO(2\u20131) ( left) and\n13CO(2\u20131) ( center-left ).Right panels : de-projected \ufb02ux density projected on the plane perpendicular to the sky and containing the polar out\ufb02ow\naxis, shown as black lines, for12CO(2\u20131) ( center-right ) and13CO(2\u20131) ( right ).\nthat Decin et al. (2008) and De Beck & Olofsson (2020) do not\ndetect SO 2in the S-type star W Aql. Our result therefore appears\nto be consistent with an intermediate chemical state of RS Cnc.\nIn Appendix D, an XCLASS modeling is presented that\nresults in the same SO 2column density of 3:5\u00021015cm\u00002as\nderived from the population diagram, and in a slightly higher\nrotational temperature of 350 K, still within the uncertainties\nof\u0018\u000650 K derived here (see Fig. 19). The XCLASS modeling\nof the 11 SO 2lines results in an average optical depth of 0.1,\ncon\ufb01rming that the lines are optically thin.\n4. Discussion\n4.1.12CO(2\u20131) and13CO(2\u20131): morpho-kinematics of the\ncircumstellar envelope\nRotational CO lines in the vibrational ground state are known to\nprobe the circumstellar envelope of AGB stars up to distances on\nthe 1000 AU scale, where the CO molecules are dissociated by\nthe interstellar UV radiation (Mamon et al. 1988). In this section,\nwe use observations of the12CO(2\u20131) and13CO(2\u20131) lines to\nprobe the morpho-kinematics of the wind at distances from the\nstar in excess of\u001850AU, in a region where the wind is expected\nto evolve smoothly toward the constant expansion regime.\nBoth12CO(2\u20131) and13CO(2\u20131) data have a Doppler veloc-\nity (vz) spectrum that clearly shows a two-component structure,\nwhere the blueshifted wing of the12CO line is partly absorbed,\nvery similar to the corresponding situation in EP Aqr (Tuan-\nAnh et al. 2019). CO rotational lines from higher J levels (5\u20134\nand 9\u20138) observed with Herschel (Danilovich et al. 2015) show\ntriangular pro\ufb01les consistent with the double-component wind\nstructure that we are proposing.\nIn the spatial distribution of the CO emission, a clear sep-\naration is observed between the equatorial region and the polar\nout\ufb02ows. This is illustrated in Fig. 20, where we show the maps\nof the \ufb02ux density in the Doppler velocity ( vz) versus position\nangle (!) plane. The \ufb02ux density is integrated over an interval of\nprojected distance ( R) from the star between 0.400and 2.500. The\nequatorial region is seen as an intense oscillation at low values\nofjvzjwhile the polar out\ufb02ows are seen as emission at larger jvzj\nvalues, in phase opposition. From these maps, we estimate, in\nagreement with earlier \ufb01ndings, that the out\ufb02ow axis projects on\nthe plane of the sky at a position angle of !=7\u000e\u00065\u000e, at which\nthe equatorial and bipolar out\ufb02ow oscillations are maximal and\nminimal, respectively. Figure 20 also shows de-projections of the\ndata cubes projected on the plane perpendicular to the plane ofthe sky that contains the polar out\ufb02ow axis. These are drawn\nassuming a dependence of the wind velocity on stellar latitude\n\u000bof the form vterm=4+5 sin4\u000bkm s\u00001, increasing from 4 to\n9 km s\u00001from the equator to the poles. The velocity \ufb01eld is\nassumed to be radial and to have reached its terminal value in\ntheRinterval considered here.\nIn order to interpret these observations, in particular possi-\nble differences in the12CO/13CO ratio between the equatorial\nregion and polar out\ufb02ows, we need to take into account the\neffect of absorption. We choose to consider only regions outside\n0.400\u001860 AU from the star, which allows for major simpli\ufb01ca-\ntions: we can ignore the very complex kinematics that governs\nthe inner CSE layers, including shocks and possible rotation. As\nwe cannot expect the data to strongly constrain the temperature\ndistribution, we take it of the form T=T0exp(\u0000r=r0)and \ufb01t the\nobserved data cubes by means of a \u001f2minimization scheme for\ndifferent values of the ( T0;r0) pair consistent with earlier esti-\nmates (Nhung et al. 2015a). We \ufb01nd that the morpho-kinematics\nis best described by modeling the polar out\ufb02ows and equatorial\nregion separately, with a separation at stellar latitude \u000b0\u001830\u000e.\nWe parametrize the radial dependence of the wind velocity as\nv=vtermr=(r+r1=2): it increases from 0 at r=0tovtermatr=1,\nreaching1\n2vtermatr=r1=2. In order to account for different open-\ning angles of the polar out\ufb02ows and different \ufb02aring angles of\nthe equatorial enhancement, we allow, within each region, for\nlatitudinal dependencies of the velocity described as Gaussian\nfunctions in sin\u000bin the equatorial region and in cos\u000bin the\npolar out\ufb02ows with adjustable Gaussian widths \u001b.\nWe do the same for the number densities, which vary radi-\nally as\u001a0(vterm=v)r\u00002with different \u001a0values for the equatorial\nregion and the polar out\ufb02ows, and of course for12CO and13CO.\nThe radiative transfer equation is integrated in a sphere of 1000\nradius and the calculated \ufb02ux densities are then smeared with\nthe synthesized beam of the observations. Reasonably good \ufb01ts\nof the data cubes are obtained given the crudeness of the model\n(see Fig. 21).\nWe \ufb01nd that the best \ufb01ts to the morpho-kinematics of the\ntwo lines are relatively insensitive to the exact form assumed for\nthe temperature structure. For r0=200, we \ufb01nd that values of T0\nbetween 70 K and 170 K in the equatorial region and between\n100 K and 200 K in the polar out\ufb02ows are acceptable. Chang-\ning the value of r0modi\ufb01es the values of T0accordingly but\ndoes not improve the quality of the \ufb01t. Parameters of the best-\ufb01t\nmodel include an angle of the polar out\ufb02ow axis with the line of\nsight i\u001930\u000eas expected, a separation in latitude between polar\nand equatorial regions, \u000b0=29\u00064 deg , terminal velocities of\nA135, page 13 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0013", "content": "A&A 658, A135 (2022)\nFig. 21. Best-\ufb01t results for CO. Left panels : same as in Fig. 20, but for the model best \ufb01t. Right panels : modeledvzspectra (red) compared with\nobservations (black) for12CO(2\u20131) ( center-right ) and13CO(2\u20131) ( right ).\nTable 3. Parameters of the best-\ufb01t model for CO.\nRegion vterm r1=2 T0 r0 Opening angle \u001b(\u001a)\u001b(v)\u001a0(12CO)\u001a0(13CO)\n( km s\u00001) (arcsec) (K) (arcsec) (FWHM) (deg) (cm\u00003) (cm\u00003)\nEquator 3:5\u00060:7 0:6\u00060:2 100 2.0 30 0:21\u00060:03>0:4 86\u000610 4:2\u00060:4\nPoles 8:6\u00060:5 0:29\u00060:10 130 2.0 70 0:50\u00060:02 0:70\u00060:04 70\u00066 2:9\u00060:4\nNotes. The quoted uncertainties correspond to a 10% increase in the best \ufb01t \u001f2, leaving all other parameters \ufb01xed at their best-\ufb01t value: they should\nnot be understood as uncertainties but as indicators of the sensitivity of the quality of the \ufb01t to each separate parameter.\n3\u20134 km s\u00001in the equatorial region, and 8\u20139 km s\u00001in the polar\nout\ufb02ows, out\ufb02ow opening angle and equatorial \ufb02aring angle of\n\u001870\u000eand\u001830\u000e, respectively ( FWHM =2:35\u0002arccos (\u001b(\u001a))and\n2:35\u0002arcsin (\u001b(\u001a)), respectively); these are listed in Table 3.\nThe wind is still being accelerated (the escape velocity of\na1:5M\fstar at a distance of 150 AU ( \u0019100for RS Cnc) is\n4.2 km s\u00001) \u2013 having reached half terminal velocity at the inner\nedge of the observed radial range \u2013 earlier in the poles than in the\nequatorial region. The number densities of CO molecules corre-\nspond to mass-loss rates of 1:0\u000210\u00007M\fyr\u00001in the equatorial\nregion and 2:0\u000210\u00007M\fyr\u00001in the out\ufb02ows6for a CO/H 2ratio\nof2\u000210\u00004. The12CO/13CO ratio is measured to be \u001820on aver-\nage, but larger in the polar out\ufb02ows ( 24\u00062) than in the equatorial\nregion ( 19\u00063). This is a barely signi\ufb01cant difference, but a sim-\nilar asymmetry seems to be present in EP Aqr (Tuan-Anh et al.\n2019): such a result is unexpected and needs to be con\ufb01rmed by\nhigher sensitivity observations before being accepted. Indeed, if\nit were con\ufb01rmed, this might suggest that the polar out\ufb02ows are\nfed in part from material freshly produced in the 3- \u000bprocess\nand mixed into the atmosphere by the third dredge-up follow-\ning a He shell \ufb02ash. This process would not only increase the\n12C abundance in the atmosphere, but also the12C/13C isotope\nratio, as indicated for example by Smith & Lambert (1990); see\nin particular their Fig. 9.\nThe presence of an equatorial density enhancement with a\nrather small \ufb02aring angle, \u001830\u000eFWHM, suggests that it may\nrather be a disk, which might be expected to be rotating and\nto have an inner rim. However, the size of the beam is too\nlarge to study this reliably. From a close inspection of the hvzi\ndistribution near the star, using the method described in Sect. 3.4\n6This is about a factor 2 larger than the values quoted in Hoai et al.\n(2014). Their data were affected by a pointing offset of the old 30m\nOTF maps that lead to an underestimation of the CO line \ufb02ux of about\na factor 2.for HCN and SiO, we infer a rotation velocity at r\u00180:500of\nvrot=jvzj=sini\u00182:5km s\u00001. However, this is a very crude\nestimate given the size of the beam and the lack of precise\nknowledge of the morpho-kinematics in the innermost radial\nrange.\nThe blob of enhanced12CO(2\u20131) line emission that had been\nidenti\ufb01ed in Hoai et al. (2014) as possibly suggesting the pres-\nence of a companion is seen on the channel maps in the vlsr=6\nto 7 km s\u00001range as an elongation in the west\u2013northwest to east\u2013\nsoutheast direction (Fig. 22). Projections of the data cube on\ndifferent planes ( vzvs.!,vzvs.R;and!vs.R) in its neigh-\nborhood show that it can be described as a pair of elongations\nat position angles of \u0018120\u000eand\u0018270\u000e, the latter being signi\ufb01-\ncantly more intense than the former and covering a broad range\nofRbetween 1and200. While these features provide no justi\ufb01ca-\ntion for a possible identi\ufb01cation of a companion, they cannot be\nused either as arguments against the presence of an unobserved\ncompanion.\n4.2. SiO(5\u20134) and SiO(6\u20135): evidence for strong absorption\nIn the present section, we compare the SiO(5\u20134) and SiO(6\u20135)\nline emission with the12CO results described in the previous\nsection. In contrast to CO, the SiO emission does not resolve the\nequatorial region from the polar out\ufb02ows, as illustrated in the\nleftmost panels of Fig. 23. Part of the reason for this is the much\nsmaller radial range being probed, as illustrated in the right panel\nof Fig. 23. As mentioned earlier in Sect. 3.5, the radial extent of\nthe SiO emission is often signi\ufb01cantly smaller than that of the\nCO emission, which is usually interpreted as evidence for the\nprogressive condensation of SiO molecules on dust grains (e.g.,\nSch\u00f6ier et al. 2004). This would cause the progressive decline of\nthe SiO/CO ratio observed in the right panel of Fig. 23 up to\nR\u00181:500, followed by a more abrupt cut-off around R\u0018200\nA135, page 14 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0014", "content": "J. M. Winters et al.: Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri\nFig. 22. Enhanced12CO(2\u20131) emission at vlsr\u00186:75km s\u00001.Upper panels : channel maps of the12CO(2\u20131) line emission between 6.25 and\n7.25 km s\u00001.Lower panels : projection of the \ufb02ux density multiplied by Ron thevlsrvs.Rplane for 250\u000e<!< 330\u000e(left), on thevlsrvs.!plane for\n0.5<R<2 arcsec ( middle ), and on the !vs.Rplane for 5.75 <vlsr<7:25km s\u00001(right ).\nFig. 23.vzvs.!maps for 0:500<R<1:500.Left: SiO(5\u20134), middle : SiO(6\u20135), octant intervals in !as discussed in the text are indicated. Right :\nintensity ratio SiO(5\u20134)/12CO(2\u20131) (black) and SiO(6\u20135)/12CO(2\u20131) (red) as a function of Rforjvzj<8km s\u00001.\ncaused by the dissociation of the SiO molecules by the inter-\nstellar UV radiation.\nAnother striking difference is the presence of high-velocity\nwings in the SiO data close to the star, that are mostly absent\nin the CO data (see Figs. 24 and 16). This may be understood\nas the SiO data probing the close neighborhood of the star much\nmore ef\ufb01ciently, where pulsation shocks and possibly convection\ncells are known to play an important role, as demonstrated by a\nhost of observations at shorter wavelengths, from far-infrared to\nnear-UV, and in agreement with theoretical modeling (see, e.g.,Hinkle et al. 1982; Winters et al. 2000a; Richter et al. 2003;\nNowotny et al. 2005; Freytag et al. 2017; Montez et al. 2017;\nH\u00f6fner & Olofsson 2018, and references therein). Also worth\nnoting in Fig. 24 is the signi\ufb01cant absorption in front of the\nstellar disk seen in the SiO data at \u0018\u00006km s\u00001, reminiscent\nof similar observations in stars such as R Dor (Nhung et al.\n2021), W Hya (Takigawa et al. 2017), and oCeti (Wong et al.\n2016). Of these three stars, two are found to be surrounded by\nan optically thick SiO layer that extends well beyond the stellar\ndisk, while in the third, oCeti, SiO emission decreases abruptly\nA135, page 15 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0015", "content": "A&A 658, A135 (2022)\nFig. 24. Doppler velocity spectra integrated over 0:2<R<2:5arcsec (black) and within R<0:2arcsec (red) for SiO(5\u20134), SiO(6\u20135), and12CO(2\u2013\n1)from left to right .\nbeyond some 10to50AU from the center of the star. In order\nto understand the mechanism of condensation of SiO molecules\non dust grains, it is therefore important to study the SiO emis-\nsion region in oxygen-rich AGB stars. Accordingly, we devote\nthe remainder of the present section to this task. In a \ufb01rst part,\nwe make some qualitative comments that help with unraveling\nthe general picture; in a second part, we account for radiative\ntransfer using the model of the morpho-kinematics developed for\nCO emission in the preceding section. The morpho-kinematics\nof the SiO(5\u20134) and SiO(6\u20135) lines are so similar that we cannot\nexpect their comparison to be very sensitive to temperature. At\ntemperature T, in the optically thin LTE approximation, the ratio\nRTof the SiO(5\u20134)/SiO(6\u20135) line emission depends only on the\nratio of the Einstein coef\ufb01cients, 5:2\u000210\u00004=9:1\u000210\u00004=0:57;\nand the ratio of the level populations, (2J+1)(exp(\u0000Eu=T),\nwhere the upper level energies Euare31:3K and 43:8K,\nrespectively (line parameters from the CDMS, based on\nM\u00fcller et al. 2013).\nHence, we have\nRT=0:48 exp(\u000031:3=T)=exp(\u000043:8=T); (7)\nfrom which we obtain\nT[K]=12:5=(ln(RT)+0:74: (8)\nFigure 25 (left) displays the observed dependence of RTonR.\nIf the SiO layer is optically thin, the value of RTprovides a direct\nmeasure of the temperature; if it is optically thick, the emis-\nsion probes only the outer part of the SiO layer and measures\na temperature that is representative of larger values of r. When\nRincreases, the observed value of RTremains nearly constant at\n\u00180:65up to R\u0018100and then increases to a value of \u00180:8at1:500,\ncorresponding to temperatures of \u001840K and\u001824K, respectively.\nThe value of 40K, associated with R<100, is close to the lower\nvalue of the temperature obtained from the CO model for r=100\n(TCO[K]=70 exp(\u0000r=200)=42K for r=100) in Sect. 4.1. This\nsuggests that for low values of the projected distance from the\nstar,R, the distance in space from the star, r, effectively probed\nby the SiO emission stays approximately constant and of the\norder of 100. Indeed, the strong self-absorption causes the region\nprobed by the SiO emission to be con\ufb01ned beyond r\u0018100(cor-\nresponding to \u001cSiO\u00181), but not to probe the volume beneath this\nsurface. For larger values of the projected distance R>100, we\nexpect the distance in 3D space, r, of the effective SiO-emittingsurface to increase progressively as a result of the elongation of\nthe emission volume along the line of poles, a pure geometrical\neffect (Fig. 20).\nQualitatively, we describe this trend in Fig. 25 (left) by\nassuming that rstays at the 100level for R<100and increases\napproximately from 100to2:500when the projected Rincreases\nfrom 100to200. Such a trend, when translated in terms of tem-\nperatures using the CO model relation TCO[K]=70 exp(\u0000r=200)\ngives a fair description of the observed dependence of RTonR\ngiven the important approximations that have been made (Fig. 25\nleft).\nThe ratio\"=\u001cof the emissivity to optical depth is a measure\nof the lower limit of the emission of a self-absorbing layer. In\nthe LTE approximation and to \ufb01rst order in \u0001E=T, where \u0001E\nis the energy of the transition, (\"=\u001c)=(T\u00172)is a constant, where\n\u0017is the frequency of the emission. Therefore, at the same tem-\nperature, (\"=\u001c)[SiO(5\u20134)] =0:88(\"=\u001c)[12CO(2\u20131)]. The value of\n(\"=\u001c)isT=26:3Jy arcsec\u00002for CO and T=29:5Jy arcsec\u00002for\nSiO. Taking as reference T=100K for SiO and 50 K for CO,\nthe corresponding values of (\"=\u001c)are 1.9 Jy arcsec\u00002for CO\nand 3.4 Jy arcsec\u00002for SiO. The observed values (Fig. 25 center-\nright) are\u00182:5and 6 Jy arcsec\u00002, respectively at R\u00180. This is\nless than a factor 2 above the reference values, showing that the\noptical thickness is close to that of the self-absorption regime. A\nsimilar result has been observed for other AGB stars with mass-\nloss rates on the order of 10\u00007M\fyr\u00001(R Dor, Nhung et al. 2021,\nW Hya, Takigawa et al. 2017).\nTo gain further insight into this issue, having obtained qual-\nitative evidence for strong absorption, we need to properly\naccount for radiative transfer. To do so, we use the model devel-\noped in Sect. 4.1 to describe the morpho-kinematics of the CO\ncomponent of the CSE: in Fig. 26 we compare Doppler veloc-\nity spectra of SiO and CO in octants of position angle (the \ufb01rst\none de\ufb01ned as 7\u000e<!< 52\u000e, then counter-clockwise for increas-\ning numbers, as indicated on Fig. 23) in a ring 100<R<1:500.\nThis range of Ris far enough from the star to be relatively inde-\npendent of modeling the star neighborhood, which contributes\nto the high-velocity wings of SiO spectra but our current data\ndo not offer signi\ufb01cant constraints on this region. We only show\nSiO(5\u20134) but the results are essentially the same for SiO(6\u20135).\nThe CO data are seen to trace the polar out\ufb02ows from the equa-\ntorial region, the SiO data do not. To adapt the CO model to\na description of the SiO data, we keep all parameters as listed\nin Table 3 with the only exception being the radial pro\ufb01le: we\ndivide the CO density parameter \u001a0by three, and we further\nA135, page 16 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0016", "content": "J. M. Winters et al.: Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri\nFig. 25. Analysis of SiO and comparison with CO. Left: ratio RTof SiO(5\u20134) to SiO(6\u20135) line emitted \ufb02uxes as a function of Rforjvzj<8km s\u00001.\nCorresponding temperature values using the relation T[K]=12:5=(ln(RT)+0:74are shown in red on the scale of the ordinate. The red dashed\nline indicates constant RTof 0.64 ( T\u001842K) for R\u0014100and a linear increase of RTto 0.89 ( T\u001820K) from 100to200.Center-left : Doppler\nvelocity spectrum of the SiO(5\u20134) data for R<0:100.Center-right :Rdistribution of the SiO(5\u20134) (red) and12CO(2\u20131) (black) emission averaged\nover position angle !, measured in Jy arcsec\u00002, and averaged over \u00002< v z<6km s\u00001as shown by the arrow in the center-left panel. Right :R\ndependence of the12CO(2\u20131)/13CO(2\u20131) ratio (black) and of the28SiO(5\u20134)/29SiO(5\u20134) ratio (red).\nFig. 26.12CO(2\u20131) and28SiO(5\u20134) Doppler velocity spectra in the ring 100<R<1:500. The data are shown in black and the best-\ufb01t model results\nare shown in red (see text). Octant intervals in position angle !are numbered as 1=[7\u000e;52\u000e];2=[52\u000e;97\u000e];:::8=[322\u000e;7\u000e], these are indicated\non the left and central panels of Fig. 23.\nmultiply it by exp(\u0000r=1:6), and set it to zero beyond r=1:600,\nin qualitative accordance with the distributions displayed in the\nright panel of Fig. 23. These modi\ufb01cations result in a ratio of\nSiO/CO=0:18atr=100, in agreement with the estimate of\nVan de Sande et al. (2018a), who obtain a SiO/CO ratio of\n0.17\u20130.19 for this type of star.\nApart from this major modi\ufb01cation of the radial distribution\nof the density, we use the same morpho-kinematics and same\ntemperature distribution as for the best \ufb01t to the CO data. In\norder to adapt to SiO, we change the parameters de\ufb01ning the\ntransition, in particular with Einstein coef\ufb01cients three orders\nof magnitude larger than for the CO transitions. The result, dis-\nplayed in Fig. 26, describes the data surprisingly well given the\ncrudeness of the exercise; in addition to offering an understand-\ning of the large difference between CO and SiO emission, it\nprovides con\ufb01rmation of the validity of the description of the\nmorpho-kinematics given by the model. What happens is that\nthe SiO emission in the modeled annular ring between 100and\n1:500probes only the outer layer of the (con\ufb01ned) SiO volume\nbecause of the very large absorption, while CO probes the lower\ndensity gas at much larger distances from the star where the\nequatorial region and the polar out\ufb02ows are well separated. We\nrefrain from attempting to adjust parameters to obtain a better\n\ufb01t: modeling the inner region could not be done reliably with the\nlimited angular resolution of the present data.Another illustration of the stronger absorption of the SiO\nline compared to the CO line is displayed in the right panel of\nFig. 25. It compares the (projected) radial distribution of the ratio\n28SiO(5\u20134)/29SiO(5\u20134) with that of the ratio12CO(2\u20131)/13CO(2\u2013\n1). The29SiO data are obtained with a similar beam size to\nthe28SiO and CO data, but with a spectral resolution of only\n3 km s\u00001, preventing us from a detailed study of their Doppler\nvelocity spectra. We expect the28SiO/29SiO isotopic ratio to be\n\u001812or lower (De Beck & Olofsson 2018, 2020), but this line\nratio is reached only at large enough values of R, where the\noptical depth has decreased suf\ufb01ciently for absorption to be less\nimportant. In the limit of complete self-absorption (i.e., emission\nat the\"=\u001clevel), the line ratio is unity. In contrast, the CO ratio is\nmuch less affected by absorption, staying at \u001880% of the value\nevaluated in Sect. 4.1 ( \u001820) over the whole radial range.\n4.3. MHD wind models\nAn important feature of the morpho-kinematics of RS Cnc is the\nlatitudinal dependence of the velocity, which is larger towards\nthe pole than along the equatorial plane. On the other hand, the\nmodeling of Hoai et al. (2014) leads to an almost spheroidal\ndistribution of matter (their Fig. 6), which implies an isotropic\nradiation \ufb01eld within the circumstellar shell (assuming position\ncoupling between dust and gas). In these conditions, a driver\nA135, page 17 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0017", "content": "A&A 658, A135 (2022)\nother than radiation is needed to accelerate matter preferentially\nalong the polar axis.\nAxi-symmetric models have been developed on the assump-\ntion that a companion disturbs the gravitational \ufb01eld (Theuns\n& Jorissen 1993; Mastrodemos & Morris 1999; Decin et al.\n2020). These models have been successful in explaining sev-\neral observed features, such as the presence of spiral structures,\nalthough the preferential acceleration along the polar axis seems\nmore dif\ufb01cult to reproduce.\nIn RS Cnc, we do not \ufb01nd evidence for the presence of a com-\npanion. While this negative result does not necessarily mean that\nthere is no companion, we are considering here another mecha-\nnism that could play a role: the presence of a magnetic \ufb01eld. In\nthis section, we argue that magnetic \ufb01elds are one possible can-\ndidate to explain a signi\ufb01cant pole-to-equator velocity contrast\nof>1.\nIndeed, magnetic \ufb01elds are an appealing way to explain\nsome of the axi-symmetric shapes of planetary nebulae, such as\npolar jets or equatorial winds. Early simulations of winds with\ndipole \ufb01elds and rotation showed that excess magnetic pressure\ncould be able to repel the wind towards both the equator and/or\nthe poles (Washimi & Shibata 1993). Similar simulations also\nshowed the formation of equatorial disks with enhanced out\ufb02ow\nvelocities in the equatorial region (Matt et al. 2000). In a more\ntoroidal con\ufb01guration, Matt & Balick (2004) showed that both\njets and equatorial disks could be produced depending on the\nmagnitude of the rotation. Finally, Garc\u00eda-Segura et al. (2005)\nshowed that magnetically driven winds yield strongly anisotropic\nout\ufb02ows with highly collimated polar jets.\nObservational polarimetric studies (Greaves 2002) revealed\nordered magnetic \ufb01elds in planetary nebulae, with various\ndegrees of toroidal con\ufb01gurations depending on the target. Using\na handful of SiO masers (Herpin et al. 2006) or CN Zeeman\nmeasurements, Duthu et al. (2017) later attempted to further\ncharacterize the magnitude and the radial dependence of the\nmagnetic \ufb01eld in the winds of AGB stars. These latter authors\nconcluded that the \ufb01eld is on the order of a few Gauss near\nthe stellar surface, and consistent with a 1=rdependence on the\ndistance rfrom the star (see their Fig. 6).\nIn this section, we report results of simplistic calculations\nwhich integrate magnetized \ufb02uid parcel trajectories from the\nsurface of an AGB star up to 10 stellar radii. We integrate\nthe acceleration due to gravitational and Lorentz forces over\ntime (pressure gradients become quickly negligible after the\nsonic point is crossed):\n\u00a8r=(\u0000\u00001)GM\u0003\nr3r+1\n\u001aJ\u0002B; (9)\nwhere ris the position of the \ufb02uid parcel, \u0000is the ratio between\nthe radiative and the gravitational force, Gis the universal grav-\nity constant, M\u0003is the stellar mass, and J=1\n4\u0019r\u0002Bis the\ncurrent vector. The mass density \u001aand the magnetic \ufb01eld Bare\nprescribed, while we solve for the position and velocity of the\n\ufb02uid parcels. We parametrize our equations with (\u0000\u00001)GM\u0003=\nv1R2\n\u0003and\u001a=\u02d9M\n4\u0019r2v1. We assume \u02d9M=1:24\u000210\u00007M\fyr\u00001;and\nR\u0003=1:6\u00021013cm as reasonable values for RS Cnc (Hoai et al.\n2014). Our choice of parametrization allows us to easily explore\nnondimensional values of the parameters independently of the\nabsolute observational constraints. After we obtain a suitable\ncontrast between polar and equatorial velocities, we retrieve the\nphysical value for the velocity scale \u2013 here v1=5:6km s\u00001\u2013\nin order to obtain a given polar out\ufb02ow velocity of 8 km s\u00001at\nr=10R\u0003. The initial velocity vector is set with a small uniform\nFig. 27. Magnetized \ufb02uid parcel trajectories from a simpli\ufb01ed model of\nRS Cnc (see text). Red trajectories meet on the polar axis, where they\nwill likely generate a jet.\nFig. 28. Radial velocity at 10 stellar radii depending on the latitude for\nthe same simpli\ufb01ed model of magnetized wind as shown in Fig. 27.\nradial velocity and we probe starting trajectories at the surface\nwith a uniformly distributed initial latitude.\nThis simple setup allows us to quickly investigate various\nmagnetic \ufb01eld con\ufb01gurations. Figure 27 displays the trajecto-\nries in the meridional plane obtained for a toroidal magnetic\n\ufb01eld with a 1=r1:1decline from B\u0003=0:5G at the stellar surface:\nB\u001e=B\u0003cos(\u0012)=(r=R\u0003)1:1where\u0012is the latitude ( 1=r1:1gives a\nmore pronounced velocity contrast between pole and equator\nthan 1=r). The Lorentz force J\u0002Bin this case is directed toward\nthe symmetry axis and acts as a focusing agent. All trajecto-\nries eventually end up on the axis where they would presumably\nlaunch a jet: this focuses mass loss towards the poles. Figure 28\nshows the resulting \u201cterminal\u201d velocity at 10 stellar radii, where\nwe have separated the latitudinal and the radial components.\nThe \ufb02ow velocities at this radius are dominated by their radial\ncomponent, but with a clearly slower wind at the equator com-\npared to the pole, as indicated by observations of, for instance,\nRS Cnc and EP Aqr. We note that rotation tends to produce\nthe opposite effect (faster radial \ufb02ow at equator compared to\npoles, due to centrifugal acceleration). We \ufb01nd similar behav-\nior for toroidal magnetic \ufb01eld con\ufb01gurations closer to what Matt\n& Balick (2004) found ( B\u001e=3B\u0003cos(\u0012) sin(\u0012)2=(r=R\u0003)2with a\n1=r2dependence and a concentration of Bat intermediate lati-\ntudes). We investigated additional dipolar \ufb01elds which are able\nto generate some amount of rotation in the wind. Thanks to the\nversatility of the present setting, we can quickly explore various\nA135, page 18 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0018", "content": "J. M. Winters et al.: Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri\ncon\ufb01gurations, linear combinations between them, several mag-\nnetic \ufb01eld decay exponents, but have not yet investigated them\nsystematically. The purpose of our investigation here is simply to\nshow that a magnetic \ufb01eld is a valid candidate to produce pole-\nto-equator velocity ratios of signi\ufb01cantly greater than 1. Finally,\nwe note that our termination radius of r=10R\u0003is arbitrary, and\na pertinent match to the observations could be considered at var-\nious distances depending on where the given tracer is expected\nto be concentrated. These crude models are still far from quan-\ntitatively matching the observational constraints from RS Cnc\nor EP Aqr, which require a broader polar out\ufb02ow and a thinner\nand denser equatorial disk. This could be adjusted by providing a\nsharper toroidal magnetic barrier to funnel the wind at the appro-\npriate places. However, such \ufb01ne-tuning would overcome the\nlimits of this crude exercise which still lacks self-consistency as\nthe density pro\ufb01le remains radial and unaffected by the magnetic\nconstraints (themselves blind to the wind), and shocks gener-\nated by the crossings of trajectories at the polar axis are not\naccounted for. We plan to investigate further with such simpli-\n\ufb01ed models in future work as they might provide a useful means\nto constrain the magnetic \ufb01eld con\ufb01guration from the morpho-\nkinetics.\n4.4. HCN in M- to S-type stars\nCherchneff (2006) recognized that the formation of CN/HCN\ndepends on the high activation barrier of the H + C 2!CH + C\nreaction, followed by rapid CN formation via N + CH !CN+H.\nTheir abundance therefore depends on thermal excursions in\nshocks, or inhomogeneities of temperature. In addition, both the\ntotal rate of formation of the pair CN/HCN and the respective\nshare between CN and HCN depend on the H/H 2ratio which\nitself depends on out-of-equilibrium chemistry because of the\nslow conversion between H and H 2. Cherchneff (2006) was thus\nable to show that the shocks produced by the pulsations close to\nthe stellar photosphere could produce highly increased yields of\nthe HCN molecule in M or S-type stars, despite their high O/C\nratio. We note here that magnetic \ufb01elds produce shocks on the\nsymmetry axis which might also help to boost HCN production\nin the polar jet.\nHCN has long been detected and surveyed in M-type and\nS-type stars (e.g., Deguchi & Goldsmith 1985; Lindqvist et al.\n1988; Bujarrabal et al. 1994; Olofsson et al. 1998; Sch\u00f6ier et al.\n2013). RS Cnc on the other hand has never been detected in\nground-state or vibrationally excited HCN despite various obser-\nvational efforts with different telescopes (Lucas et al. 1988;\nSopka et al. 1989; Nercessian et al. 1989; Lindqvist et al. 1992;\nBujarrabal et al. 1994; Bieging & Latter 1994; Olofsson et al.\n1998). Adopting a mass-loss rate of 3\u000210\u00007M\fyr\u00001, Bujarrabal\net al. (1994) estimated an upper limit to the HCN abundance\nin RS Cnc of 4:5\u000210\u00007. This upper limit becomes 1:35\u000210\u00006\nif we adopt \u02d9M=1\u000210\u00007M\fyr\u00001. Sch\u00f6ier et al. (2013) pre-\nsented a comprehensive analysis of the HCN abundance in a\nsample of 59 AGB stars, including 25 carbon-rich, 19 S-type, and\n25 M-type stars, by means of a non-LTE radiative trans-\nfer modeling. For M-type and S-type stars, these authors\nderived a median HCN/H 2abundance of order 1\u000210\u00007and\n7\u000210\u00007, respectively, with a large spread between \u00185\u000210\u00008and\n\u00185\u000210\u00006.\nBy an XCLASS modeling of the HCN(3\u20132) line detected\nhere (see Appendix D), and assuming a rotational temperature of\n350 K, we derive an HCN column density of \u00181:6\u00021015cm\u00002;\nsee Fig. 29. With the same assumptions as those made in\nSect. 3.6, this translates to HCN abundances of X(HCN/hHi)=\n1.0\" 0.5\" 0.0\" -0.5\" -1.0\"1.0\"\n0.5\"\n0.0\"\n-0.5\"\n-1.0\"\nR.A. Offset (arcsec)Dec. Offset (arcsec)HCN (3-2)\n0.20.40.60.81.01.21.4Ntot (cm2)\n1e15Fig. 29. Map of the HCN column density as derived by an XCLASS\nmodeling (see Appendix D). The black ellipse in the lower left corner\nindicates the synthesized beam.\n3:3\u000210\u00007, or, if hydrogen were completely bound in H 2,\nX(HCN/H 2)=6:6\u000210\u00007. This abundance perfectly \ufb01ts in the\nrange found by Sch\u00f6ier et al. (2013) for M- to S-type stars and is\nalso consistent with the upper limit derived by Bujarrabal et al.\n(1994) corrected for the mass-loss rate.\nClumpy and porous winds help UV photons to penetrate\ncloser to the star, thus photodissociating CO and N 2to release\nmore of the C/NO and the N/CS pairs of reactants, which both\nproduce CN: this process was shown to considerably enhance\nthe HCN abundances close to the star (Van de Sande et al. 2018b,\n2020). Rather than uniformly distributed random clumpiness and\nporosity, one can also imagine ordered density distributions in\nthe wind, which could let UV photons penetrate through low-\ndensity channels. These structures could sometimes be hard to\nwitness due to line of sight confusion. In fact, our simpli\ufb01ed\nmagnetized wind models (see Fig. 27 with scarcity of trajec-\ntories around the equator) or more sophisticated magnetized\nwind models (e.g., Matt et al. 2000; Washimi & Shibata 1993)\nallow for lower column-density channels at certain angles. These\nmay result in increased HCN abundance, but chemical post-\nprocessing in magnetized models will be necessary to assess\nwhether this is a viable interpretation of the observations.\n5. Conclusions\nUsing NOEMA equipped with PolyFiX, we obtained high-\nspatial resolution ( \u00180.300) images of RS Cnc in several lines\nof different molecules. We detect, and in most cases are able\nto map, 32 lines of 13 molecules and isotopologs (CO,13CO,\nSiO,29SiO, SO,34SO, SO 2, H 2O, HCN, H13CN, PN), includ-\ning several transitions from vibrationally excited states, and a\ntentative identi\ufb01cation of Si17O and possibly29Si17O. HCN as\nwell as millimeter vibrationally excited H 2O, SO, SO 2, and PN\nand their isotopologs are \ufb01rst detections in RS Cnc. From their\n\ufb01rst-moment maps, some of the lines, SiO( v=1,6\u20135), HCN,\nSO, SO 2, show signs of rotation in the close vicinity of the star.\nA population diagram analysis for the 11 observed SO 2lines\nprovides a rotational temperature of about 320 K in the region\nthat shows signs of rotation. Temperatures of this order are also\nfound from an XCLASS modeling of the SO 2lines. For SO 2\nand HCN, we \ufb01nd column densities from the XCLASS mod-\neling of NSO2\u00183:5\u00021015cm\u00002andNHCN\u00181:6\u00021015cm\u00002,\nA135, page 19 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0019", "content": "A&A 658, A135 (2022)\nwhich translate to abundance ratios of X(SO2=H2)=1:5\u000210\u00006\nandX(HCN/H 2)=6:6\u000210\u00007, respectively, well within the range\nexpected for an MS-type star.\nWe \ufb01nd broad wings in the spectral line pro\ufb01les of vibra-\ntional ground-state transitions of SiO and SO and in \ufb01rst\nvibrationally excited transitions of SiO, which indicate radial\nvelocities of about twice the terminal out\ufb02ow velocity as probed\nby CO. As high velocities very close to the star are also seen in\nsimilar objects, such as EP Aqr, oCet, and R Dor, the presence\nof these broad line wings calls for a mechanism common to the\nclass of pulsating AGB stars. We interpret these high-velocity\nline wings as the imprints of pulsation shocks acting in the very\ninner region around these stars.\nThe spatially resolved images allow us to trace the morpho-\nkinematics of the wind around RS Cnc at different scales. In the\ninner part ( <0.500, or 75 AU), we \ufb01nd a rotating structure well\ntraced by the less abundant molecules (HCN, SO, SO 2), and by\nSiO in (v=1) lines. Outside 75 AU, we \ufb01nd an expanding axi-\nsymmetric out\ufb02ow, with velocities \u00184km s\u00001in the equatorial\nplane, and\u00189km s\u00001along the polar axis. This polar axis coin-\ncides with the axis of the internal rotating structure. A model\nthat \ufb01ts the data cubes obtained on the12CO(2\u20131),13CO(2\u20131)\nand SiO(v=0, 5\u20134 and 6\u20135) lines gives a mass-loss rate of\n1\u000210\u00007M\fyr\u00001for the equatorial region (latitude <30\u000e) and\nof2\u000210\u00007M\fyr\u00001for the polar out\ufb02ows (latitude >30\u000e). The\n12CO/13CO ratio is measured to be \u001820on average, 24\u00062in the\npolar out\ufb02ows and 19\u00063in the equatorial region.\nAlthough we cannot exclude the possibility that an unseen\nstellar or substellar companion shapes the circumstellar environ-\nment of RS Cnc, we also consider the possibility of a magnetic\n\ufb01eld playing this role. In particular, a toroidal magnetic \ufb01eld\ncon\ufb01guration would provide a mechanism able to produce the\nsigni\ufb01cant velocity contrast between high polar-out\ufb02ow veloci-\nties and low expansion velocities in the equatorial region that is\nobserved in RS Cnc and other similar stars.\nAcknowledgements. We thank the staff at the NOEMA and Pico Veleta obser-\nvatories for their support of these observations. The authors are grateful to\nthe anonymous referee for a very detailed and valuable report that helped\nimproving the presentation of the material. This work is based on observations\ncarried out under project numbers W16BE, D17AE, W19AX with the IRAM\nNOEMA interferometer and under project ID 136-19 with the IRAM 30m tele-\nscope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN\n(Spain). The Ha Noi team acknowledges \ufb01nancial support from the World Lab-\noratory, the Odon Vallet Foundation and VNSC. This research is funded in\npart by the Vietnam National Foundation for Science and Technology Devel-\nopment (NAFOSTED) under grant number 103.99-2019.368. This work was\nsupported by the Programme National \u201cPhysique et Chimie du Milieu Interstel-\nlaire\u201d (PCMI) of CNRS/INSU with INC/INP co-funded by CEA and CNES. This\nwork has made use of data from the European Space Agency (ESA) mission Gaia\n(https://www.cosmos.esa.int/gaia ), processed by the Gaia Data Process-\ning and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/\ngaia/dpac/consortium ). 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{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0021", "content": "A&A 658, A135 (2022)\nAppendix A: Resolved out \ufb02ux\nFig. A.1. Effect of missing short spacing information on the CO\nlines. Left:12CO(2\u20131). Right:13CO(2-1). A-con\ufb01guration and D-\ncon\ufb01guration are merged, the spectral resolution is 0.5 km s\u00001and the\nCO emission is integrated over the central 2200\u00022200, i.e., over the full\n\ufb01eld of view of the NOEMA antennas at 230 GHz. Black pro\ufb01les: OTF\ndata (i.e., the short-spacing information that is \ufb01ltered out by the inter-\nferometer) are added. Red pro\ufb01les: A+D con\ufb01guration interferometer\ndata, only.\nThe effect on the \ufb02ux of \ufb01ltering out large-scale structure\nwith the interferometer is shown in Fig. A.1 for the CO and13CO\nlines. These two are the only lines discussed in this paper that are\naffected by the short-spacing problem.\nAppendix B: Intensity maps\nHere we present velocity-integrated intensity maps in three\nvelocity ranges for HCN and H13CN (Fig. B.1), the four detected\nSO lines (Fig. B.3), and three out of the 11 SO 2lines (Fig. B.4).\nThese are the SO 2line with the lowest upper level energy, the\nstrongest SO 2line detected here, and the SO 2line with the high-\nest upper level energy, respectively. All these nine lines display\nkinematic structure in east-west direction. Also shown are zeroth\nmoment maps for the (unresolved) H 2O lines (Fig. B.2) and for\nthe (weak) PN line (Fig. B.5).\nAppendix C: SO 2line pro\ufb01les\nIn this section, we present the line pro\ufb01les of all the 11 SO 2lines\ndetected with our setups (see Fig. C.1).\nAppendix D: XCLASS modeling of HCN and SO 2\nThe HCN(3-2) line and the 11 detected SO 2emission lines\nwere modeled using the eXtended CASA Line Analysis Soft-\nware Suite (XCLASS7, M\u00f6ller et al. 2017). XCLASS models and\n\ufb01ts molecular lines by solving the 1D radiative transfer equa-\ntion with the assumption of LTE and of an isothermal source.\nHere, 1D means that the radiative transfer equation is integrated\nalong the line of sight. Spectral lines are \ufb01tted with Gaussian\npro\ufb01les, and optical depth effects and source size are considered\nin the calculations. Molecular properties (e.g., Einstein coef\ufb01-\ncients, partition functions, etc.) are taken from an embedded\nSQLite database containing entries from the Cologne Database\nfor Molecular Spectroscopy (CDMS, M\u00fcller et al. 2001, 2005)\nand from the Jet Propulsion Laboratory database (JPL, Pickett\n7https://xclass.astro.uni-koeln.deet al. (1998)) using the Virtual Atomic and Molecular Data Cen-\nter (VAMDC, Endres et al. 2016). The \ufb01t parameter set for each\nline component consists of the source size \u0012source , the rotation\ntemperature Trot, the total column density Ntot, the line width\n\u0001v, and the velocity offset v o\u000b(given here in the LSR system).\nThe XCLASS package offers various algorithms to \ufb01nd the\nbest-\ufb01t parameters by minimizing the \u001f2value, and here we uti-\nlized the Levenberg-Marquardt (LM) method. To obtain maps\nof the physical parameters, we use the myXCLASSMapFIt func-\ntion to \ufb01t HCN(3-2) and the 11 detected SO 2emission lines (see\nFig. C.1) pixel by pixel.\nFor SO 2, we modeled and \ufb01tted 11 lines simultaneously with\na threshold of 18 \u001band a single Gaussian component. All \ufb01t\nparameters are regarded as free parameters in the \ufb01tting process.\nThe XCLASS models for SO 2result in a temperature of Trot\u0018\n350K (Fig. D.1), somewhat higher than the result from our pop-\nulation diagram analysis, but within the error bars (see Sect. 3.6).\nIt also results in an average line optical depth of 0.1, con\ufb01rming\nthat the assumption of the lines being optically thin is justi-\n\ufb01ed when constructing the population diagram. Assuming LTE,\nthe derived rotation temperature equals the kinetic gas temper-\nature Tkin. For the SO 2column density, the XCLASS modeling\nresults in a value of NSO2\u00183:5\u00021015cm\u00002, almost identical\nto the result from the population diagram analysis presented in\nSect. 3.6, resulting in an abundance X(SO2=H2)=1:5\u000210\u00006.\nThe respective results are shown in Figs. D.1 and D.2.\nFor HCN(3-2), we applied the same threshold of 18 \u001bas for\nSO2and \ufb01tted Gaussian components to the line pro\ufb01les on each\npixel, taking into account the hyper\ufb01ne structure of the line. The\nvelocity map and line widths displayed on Fig. D.3 are due to\nthe intrinsic (thermal and rotational) broadening only, whereas\nthe pro\ufb01le shown in Fig. D.4 represents the sum of the hyper-\n\ufb01ne components of HCN(3-2). As only one HCN rotational line\nis available, the HCN rotational temperature cannot be deter-\nmined. We therefore \ufb01xed the rotation temperature at a value\nof 350 K, the same temperature as we \ufb01nd from the SO 2mod-\neling based on the similar emission region of SO 2and HCN,\nsee Figs. 17, B.1, and B.4. The HCN results are displayed in\nFig. D.3. In particular, we derive an HCN column density of\n\u00181:6\u00021015cm\u00002, which translates to an HCN abundance of\nX(HCN/H 2)=6:6\u000210\u00007.\nA135, page 22 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0022", "content": "J. M. Winters et al.: Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri\nFig. B.1. Velocity-integrated intensity maps of the HCN(3-2) (upper row) and H13CN(3-2) lines (lower row), covering three velocity intervals.\nLeft: Blue line wing [v lsr;\u0003\u000010,vlsr;\u0003\u00002] km s\u00001, Middle: line center [v lsr;\u0003\u00002,vlsr;\u0003+2] km s\u00001, Right: Red line wing [v lsr;\u0003+2,vlsr;\u0003+10] km s\u00001.\nNorth is up and east is to the left. We note the different color scales. Contours are plotted every 10\u001bfor HCN and every 3\u001bfor H13CN, where\n(from left to right) 1\u001b=5:7;7:2;7:2mJy/beam km s\u00001for HCN(3-2) and 1\u001b=5:2;5:0;5:6mJy/beam km s\u00001for H13CN(3-2). The black ellipse\nin the lower left corner indicates the synthesized beam. We note that the HCN maps were produced using robust weighting, whereas for the H13CN\nmaps, we applied natural weighting.\nFig. B.2. Zeroth moment maps of the H 2O 232 GHz (left) and H 2O 263 GHz (right) lines. North is up and east is to the left. We note the different\ncolor scales. Contours are plotted every 5\u001bwhere 1\u001b=13:8mJy/beam\u0001km s\u00001for the 232 GHz line and 1\u001b=13:92mJy/beam\u0001km s\u00001for the\n263 GHz line. The black ellipse in the lower left corner indicates the synthesized beam.\nA135, page 23 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0023", "content": "A&A 658, A135 (2022)\nFig. B.3. Velocity-integrated intensity maps of the SO(6(6)-5(5)) (upper row), SO(5(5)-4(4)) (second row), SO(6(5)-5(4)) (third row) and SO(7(6)-\n6(5)) (lower row) lines covering three velocity intervals. Left: Blue line wing [v lsr;\u0003\u000010,vlsr;\u0003\u00002] km s\u00001, Middle: Line center [v lsr;\u0003\u00002,vlsr;\u0003+2]\nkm s\u00001, Right: Red line wing [v lsr;\u0003+2,vlsr;\u0003+10] km s\u00001. North is up and east is to the left. We note the different color scales. Contours are\nplotted every 10\u001b, where (from left to right) 1\u001b=10:0;10:4;10:3mJy/beam\u0001km s\u00001for SO(6(6)-5(5)), 1\u001b=7:3;7:6;7:4mJy/beam\u0001km s\u00001for\nSO(5(5)-4(4)), 1\u001b=7:6;8:1;7:4mJy/beam\u0001km s\u00001for SO(6(5)-5(4)), and 1\u001b=8:7;9:6;8:7mJy/beam\u0001km s\u00001for SO(7(6)-6(5)). The black ellipse\nin the lower left corner indicates the synthesized beam.\nA135, page 24 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0024", "content": "J. M. Winters et al.: Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri\nFig. B.4. Velocity-integrated intensity maps of SO 2(9(3, 7)-9(2, 8)) (lowest E u, upper row), SO 2(14(0,14)-13(1,13)) (strongest SO 2line, second\nrow), and SO 2(34(4,30)-34(3,31)) (highest E u, lower row), covering three velocity intervals. Left: Blue line wing [v lsr;\u0003\u000010,vlsr;\u0003\u00002] km s\u00001,\nMiddle: line center [v lsr;\u0003\u00002,vlsr;\u0003+2] km s\u00001, Right: Red line wing [v lsr;\u0003+2,vlsr;\u0003+10] km s\u00001. North is up and east is to the left. We note\nthe different color scales. Contours are plotted every 3\u001b, where (from left to right) 1\u001b=6:5;6:7;6:6mJy/beam\u0001km s\u00001for SO 2( 9(3, 7)- 9(2,\n8))1\u001b=5:9;6:2;6:3mJy/beam\u0001km s\u00001for SO 2(14(0,14)-13(1,13)), 1\u001b=7:8;7:8;7:7mJy/beam\u0001km s\u00001for SO 2(34(4,30)-34(3,31)) . The black\nellipse in the lower left corner indicates the synthesized beam.\nFig. B.5. Zeroth moment map of the PN(N=5-4,J=6-5) line. Contours are plotted every 3\u001b, where 1\u001b=9:6mJy/beam\u0001km s\u00001. North is up and\neast is to the left. The black ellipse in the lower left corner indicates the synthesized beam.\nA135, page 25 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0025", "content": "A&A 658, A135 (2022)\nFig. C.1. Pro\ufb01les of all the 11 detected SO 2lines. A-con\ufb01guration and\nD-con\ufb01guration data are merged, the spectral resolution is 3 km s\u00001,\nand the emission is integrated over the central 200\u0002200square aperture.\nThe lines are ordered by decreasing frequency from top to bottom and\nleft to right.\n0.5\" 0.0\" -0.5\"0.6\"\n0.4\"\n0.2\"\n0.0\"\n-0.2\"\n-0.4\"\nR.A. Offset (arcsec)Dec. Offset (arcsec)SO2\n1.01.52.02.53.03.5Ntot (cm2)\n1e15\n0.5\" 0.0\" -0.5\"0.6\"\n0.4\"\n0.2\"\n0.0\"\n-0.2\"\n-0.4\"\nR.A. Offset (arcsec)Dec. Offset (arcsec)SO2\n240260280300320340Trot (K)\n0.5\" 0.0\" -0.5\"0.6\"\n0.4\"\n0.2\"\n0.0\"\n-0.2\"\n-0.4\"\nR.A. Offset (arcsec)Dec. Offset (arcsec)SO2\n6.006.256.506.757.007.257.507.758.00Voff (km s1)\n0.5\" 0.0\" -0.5\"0.6\"\n0.4\"\n0.2\"\n0.0\"\n-0.2\"\n-0.4\"\nR.A. Offset (arcsec)Dec. Offset (arcsec)SO2\n7.07.58.08.59.09.5Line width(km s1)\nFig. D.1. Maps of total column density, rotation temperature, velocity\noffset (in the LSR system), and line width for SO 2are derived with a\nthreshold of 18 \u001band \ufb01tting one Gaussian component to the line pro\ufb01les.\nA135, page 26 of 27"}
{"doi": "10.1051_0004-6361_202141662", "pagenum": "page_0026", "content": "J. M. Winters et al.: Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri\n0.5\" 0.0\" -0.5\"0.6\"\n0.4\"\n0.2\"\n0.0\"\n-0.2\"\n-0.4\"\nR.A. Offset (arcsec)Dec. Offset (arcsec)SO2\n1.01.52.02.53.03.5Ntot (cm2)\n1e15\n20\n 0 200.000.020.04Flux [Jy/pixel]SO2 (16(3,13)16(2,14))\n20\n 0 200.000.010.020.030.04SO2 (22(2,20)22(1,21))\n20\n 0 200.000.010.020.030.04Flux [Jy/pixel]SO2 (28(3,25)28(2,26))\n20\n 0 200.000.020.040.06\nSO2 (14(0,14)13(1,13))\n20\n 0 200.000.010.020.03Flux [Jy/pixel]SO2 (10(3,7)10(2,8))\n20\n 0 200.000.010.020.03SO2 (15(2,14)15(1,15))\n20\n 0 200.000.010.020.03Flux [Jy/pixel]SO2 (32(4,28)32(3,29))\n20\n 0 200.000.010.020.03SO2 (9(3,7)9(2,8))\n20\n 0 200.000.010.020.030.04Flux [Jy/pixel]SO2 (30(4,26)30(3,27))\n20\n 0 20\nLSR velocity (km/s)0.000.010.020.03SO2 (30(3,27)30(2,28))\n20\n 0 20\nLSR velocity (km/s)0.000.010.020.03Flux [Jy/pixel]SO2 (34(4,30)34(3,31))\n \n \n \n \n \nFig. D.2. Pro\ufb01les of the 11 SO 2emission lines (in black) extracted on\nthe central pixel and XCLASS modeled lines (in red) at the position\nof the continuum at RA = 09:10:38.77 and Dec = +30:57:46.68 (see\nSect. 3.1) as marked on the upper diagram.\n1.0\" 0.5\" 0.0\" -0.5\" -1.0\"1.0\"\n0.5\"\n0.0\"\n-0.5\"\n-1.0\"\nR.A. Offset (arcsec)Dec. Offset (arcsec)HCN (3-2)\n0.20.40.60.81.01.21.4Ntot (cm2)\n1e15\n1.0\" 0.5\" 0.0\" -0.5\" -1.0\"1.0\"\n0.5\"\n0.0\"\n-0.5\"\n-1.0\"\nR.A. Offset (arcsec)Dec. Offset (arcsec)HCN (3-2)\n6.256.506.757.007.257.507.758.00Voff (km s1)\n1.0\" 0.5\" 0.0\" -0.5\" -1.0\"1.0\"\n0.5\"\n0.0\"\n-0.5\"\n-1.0\"\nR.A. Offset (arcsec)Dec. Offset (arcsec)HCN (3-2)\n3.03.54.04.55.05.56.0Line width (km s1)\n \n \n \nFig. D.3. Maps of total column density, velocity offset (= v lsr), and line\nwidth of HCN(3-2) (see text for details). The black ellipse in the lower\nleft corner of each map indicates the synthesized beam.\n5\n 0 5 10 15 20\nVLSR [km s1]\n0.00.10.20.30.40.50.60.7Flux [Jy/pixel]HCN (32)\n \n \nFig. D.4. Pro\ufb01le of the HCN(3-2) emission line (in black) extracted\non the central pixel and XCLASS modeled line (in red) at the position\nof the continuum at RA = 09:10:38.77 and Dec = +30:57:46.68 (see\nSect. 3.1) as marked on the upper diagram of Fig. D.3.\nA135, page 27 of 27"}