2010A&A...521L...7M


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.05CEST10:01:45

2010A&A...521L...7M - Astronomy and Astrophysics, volume 521, L7-7 (2010/10-1)

Herschel/HIFI deepens the circumstellar NH3 enigma.

MENTEN K.M., WYROWSKI F., ALCOLEA J., DE BECK E., DECIN L., MARSTON A.P., BUJARRABAL V., CERNICHARO J., DOMINIK C., JUSTTANONT K., DE KOTER A., MELNICK G., NEUFELD D.A., OLOFSSON H., PLANESAS P., SCHMIDT M., SCHOEIER F.L., SZCZERBA R., TEYSSIER D., WATERS L.B.F.M., EDWARDS K., OLBERG M., PHILLIPS T.G., MORRIS P., SALEZ M. and CAUX E.

Abstract (from CDS):

Circumstellar envelopes (CSEs) of a variety of evolved stars have been found to contain ammonia (NH3) in amounts that exceed predictions from conventional chemical models by many orders of magnitude. The observations reported here were performed in order to better constrain the NH3 abundance in the CSEs of four, quite diverse, oxygen-rich stars using the NH3 ortho JK=10-00 ground-state line. We used the Heterodyne Instrument for the Far Infrared aboard Herschel to observe the NH3 JK=10-00 transition near 572.5GHz, simultaneously with the ortho-H2O JKa,Kc=11,0-10,1 transition, toward VY CMa, OH 26.5+0.6, IRC+10420, and IK Tau. We conducted non-LTE radiative transfer modeling with the goal to derive the NH3 abundance in these objects' CSEs. For the last two stars, Very Large Array imaging of NH3 radio-wavelength inversion lines were used to provide further constraints, particularly on the spatial extent of the NH3-emitting regions. We find remarkably strong NH3 emission in all of our objects with the NH3 line intensities rivaling those of the ground state H2O line. The NH3 abundances relative to H2 are very high and range from 2x10–7 to 3x10–6 for the objects we have studied. Our observations confirm and even deepen the circumstellar NH3 enigma. While our radiative transfer modeling does not yield satisfactory fits to the observed line profiles, it does lead to abundance estimates that confirm the very high values found in earlier studies. New ways to tackle this mystery will include further Herschel observations of more NH3 lines and imaging with the Expanded Very Large Array.

Abstract Copyright:

Journal keyword(s): stars: AGB and post-AGB - supergiants - circumstellar matter

Simbad objects: 9

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Number of rows : 9

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 * omi Cet Mi* 02 19 20.79210 -02 58 39.4956   7.63 6.53 5.03   M5-9IIIe+DA 1434 0
2 V* IK Tau Mi* 03 53 28.8884898148 +11 24 21.865959095 16.99 17.03 13.39 7.29 3.20 M7-11 570 0
3 RAFGL 618 pA* 04 42 53.6245215366 +36 06 53.397219192   16.32   12.59   C-rich 954 0
4 V* VY CMa s*r 07 22 58.32877 -25 46 03.2355 12.01 10.19 7.95     M5Iae 995 0
5 OH 231.8 +4.2 OH* 07 42 16.947 -14 42 50.20           M10III+A 503 1
6 IRC +10216 C* 09 47 57.40632 +13 16 43.5648     10.96     C9,5e 2133 0
7 OH 26.5 +0.6 OH* 18 37 32.50920 -05 23 59.1936           ~ 284 0
8 IRC +10420 pA* 19 26 48.0981288433 +11 21 16.756524951   13.98 11.66     F8Ia+e 452 0
9 V* V1610 Cyg pA* 21 02 18.27 +36 41 37.0           F5Iae 830 1

    Equat.    Gal    SGal    Ecl

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2020.07.05-10:01:46

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