2018A&A...612A..48W


C.D.S. - SIMBAD4 rel 1.7 - 2020.09.28CEST21:57:30

2018A&A...612A..48W - Astronomy and Astrophysics, volume 612A, 48-48 (2018/4-1)

Circumstellar ammonia in oxygen-rich evolved stars.

WONG K.T., MENTEN K.M., KAMINSKI T., WYROWSKI F., LACY J.H. and GREATHOUSE T.K.

Abstract (from CDS):


Context. The circumstellar ammonia (NH3) chemistry in evolved stars is poorly understood. Previous observations and modelling showed that NH3 abundance in oxygen-rich stars is several orders of magnitude above that predicted by equilibrium chemistry.
Aims. We would like to characterise the spatial distribution and excitation of NH3 in the oxygen-rich circumstellar envelopes (CSEs) of four diverse targets: IK Tau, VY CMa, OH 231.8+4.2, and IRC +10420.
Methods. We observed NH3 emission from the ground state in the inversion transitions near 1.3 cm with the Very Large Array (VLA) and submillimetre rotational transitions with the Heterodyne Instrument for the Far-Infrared (HIFI) aboard Herschel Space Observatory from all four targets. For IK Tau and VY CMa, we observed NH3 rovibrational absorption lines in the ν2 band near 10.5µm with the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope Facility (IRTF). We also attempted to search for the rotational transition within the excited vibrational state (v2=1) near 2mm with the IRAM 30m Telescope. Non-LTE radiative transfer modelling, including radiative pumping to the vibrational state, was carried out to derive the radial distribution of NH3 in the CSEs of these targets.
Results. We detected NH3 inversion and rotational emission in all four targets. IK Tau and VY CMa show blueshifted absorption in the rovibrational spectra. We did not detect vibrationally excited rotational transition from IK Tau. Spatially resolved VLA images of IK Tau and IRC +10420 show clumpy emission structures; unresolved images of VY CMa and OH 231.8+4.2 indicate that the spatial-kinematic distribution of NH3 is similar to that of assorted molecules, such as SO and SO2, that exhibit localised and clumpy emission. Our modelling shows that the NH3 abundance relative to molecular hydrogen is generally of the order of 10–7, which is a few times lower than previous estimates that were made without considering radiative pumping and is at least ten times higher than that in the carbon-rich CSE of IRC +10216. NH3 in OH 231.8+4.2 and IRC +10420 is found to emit in gas denser than the ambient medium. Incidentally, we also derived a new period of IK Tau from its V-band light curve.
Conclusions. NH3 is again detected in very high abundance in evolved stars, especially the oxygen-rich ones. Its emission mainly arises from localised spatial-kinematic structures that are probably denser than the ambient gas. Circumstellar shocks in the accelerated wind may contribute to the production of NH3. Future mid-infrared spectroscopy and radio imaging studies are necessary to constrain the radii and physical conditions of the formation regions of NH3.

Abstract Copyright: © ESO 2018

Journal keyword(s): stars: AGB and post-AGB - circumstellar matter - supergiants - stars: winds, outflows - ISM: molecules - stars: mass-loss

VizieR on-line data: <Available at CDS (J/A+A/612/A48): list.dat fits/*>

Simbad objects: 26

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Number of rows : 26

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 3C 48 QSO 01 37 41.2995845985 +33 09 35.079126038   16.62 16.20     ~ 2518 2
2 * omi Cet Mi* 02 19 20.79210 -02 58 39.4956   7.63 6.53 5.03   M5-9IIIe+DA 1444 0
3 4C 06.11 QSO 02 24 28.42819659 +06 59 23.3415393   20.8 20.0 17.78   ~ 146 1
4 QSO B0336-0156 QSO 03 39 30.93778751 -01 46 35.8041062   18.96 18.41 17.33   ~ 510 1
5 V* IK Tau Mi* 03 53 28.8884898148 +11 24 21.865959095 16.99 17.03 13.39 7.29 3.20 M7-11 576 0
6 QSO B0406+121 BLL 04 09 22.00871268 +12 17 39.8477204   20.5   18.27   ~ 99 1
7 RAFGL 618 pA* 04 42 53.6245215366 +36 06 53.397219192   16.32   12.59   C-rich 958 0
8 ICRF J054236.1+495107 Sy1 05 42 36.13789843 +49 51 07.2337251   18.45 17.80 17.210   ~ 1275 1
9 V* VY CMa s*r 07 22 58.32877 -25 46 03.2355 12.01 10.19 7.95     M5Iae 1002 0
10 QSO J0730-116 QSO 07 30 19.11247420 -11 41 12.6005110     20.30 20.3   ~ 264 1
11 ICRF J073106.6-234147 QSO 07 31 06.6679914 -23 41 47.869973   21.60       ~ 20 1
12 PKS 0733-17 Rad 07 35 45.81248037 -17 35 48.5022692           ~ 55 1
13 OH 231.8 +4.2 OH* 07 42 16.947 -14 42 50.20           M10III+A 505 1
14 VCS4 J0748-1639 gam 07 48 03.0838227 -16 39 50.253762           ~ 23 1
15 V* R Leo Mi* 09 47 33.4839808805 +11 25 43.823283729 9.22 8.94 7.53 3.39 0.12 M7-9e 875 1
16 IRC +10216 C* 09 47 57.40632 +13 16 43.5648     10.96     C9,5e 2147 0
17 HD 101584 pA* 11 40 58.8052292556 -55 34 25.813187841 7.80 7.40 7.01     B8/9I/IIe 122 0
18 3C 286 Sy1 13 31 08.2885060664 +30 30 32.960825108   17.51 17.25     ~ 3754 1
19 V* VX Sgr s*r 18 08 04.0431479808 -22 13 26.629744195 11.72 9.41 6.52 3.90 2.11 M8.5Ia 549 0
20 V* W Aql S* 19 15 23.3581458294 -07 02 50.308513461   12.72 10.14     S6/6e 206 0
21 GB6 B1920+1524 Rad 19 22 34.6993758 +15 30 10.032861           ~ 39 0
22 IRC +10420 pA* 19 26 48.0981288433 +11 21 16.756524951   13.98 11.66     F8Ia+e 453 0
23 IRAS 19312+1950 Y*O 19 33 24.24888 +19 56 55.6512           ~ 47 0
24 V* CK Vul CV* 19 47 37.9563868576 +27 18 41.788878128           ~ 108 0
25 NML Cyg s*r 20 46 25.5382179476 +40 06 59.396202678   18.64 16.60     M7/8 483 0
26 V* V1610 Cyg pA* 21 02 18.27 +36 41 37.0           F5Iae 833 1

    Equat.    Gal    SGal    Ecl

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2020.09.28-21:57:30

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