2015A&A...575A..84V


C.D.S. - SIMBAD4 rel 1.7 - 2020.09.28CEST09:01:41

2015A&A...575A..84V - Astronomy and Astrophysics, volume 575A, 84-84 (2015/3-1)

New N-bearing species towards OH 231.8+4.2. HNCO, HNCS, HC3N, and NO.

VELILLA-PRIETO L., SANCHEZ CONTRERAS C., CERNICHARO J., AGUNDEZ M., QUINTANA-LACACI G., ALCOLEA J., BUJARRABAL V., HERPIN F., MENTEN K.M. and WYROWSKI F.

Abstract (from CDS):

Circumstellar envelopes (CSEs) around asymptotic giant branch (AGB) stars are the main sites of molecular formation. OH231.8+4.2 is a well studied oxygen-rich CSE around an intermediate-mass evolved star that, in dramatic contrast to most AGB CSEs, displays bipolar molecular outflows accelerated up to ∼400km/s. OH231.8+4.2 also presents an exceptional molecular richness probably due to shock-induced chemical processes. We report the first detection in this source of four nitrogen-bearing species, HNCO, HNCS, HC3N, and NO, which have been observed with the IRAM-30m radiotelescope in a sensitive mm-wavelength survey towards this target. HNCO and HNCS are also first detections in CSEs. The observed line profiles show that the emission arises in the massive (∼0.6M) central component of the envelope, expanding with low velocities of Vexp∼15-30km/s, and at the base of the fast lobes. The NO profiles (with FWHM∼40-50km/s) are broader than those of HNCO, HNCS, and HC3N and, most importantly, broader than the line profiles of 13CO, which is a good mass tracer. This indicates that the NO abundance is enhanced in the fast lobes relative to the slow, central parts. From LTE and non-LTE excitation analysis, we estimate beam-average rotational temperatures of Trot∼15-30K (and, maybe, up to ∼55K for HC3N) and fractional abundances relative to H2 of X(HNCO)~[0.8-1]x10–7, X(HNCS)~[0.9-1]x10–8, X(HC3N)~[5-7]x10–9, and X(NO)~[1-2]x10–6. NO is, therefore, amongst the most abundant N-bearing species in OH231.8+4.2. We performed thermodynamical chemical equilibrium and chemical kinetics models to investigate the formation of these N-bearing species in OH231.8+4.2. The model underestimates the observed abundances for HNCO, HNCS, and HC3N by several orders of magnitude, which indicates that these molecules can hardly be products of standard UV-photon and/or cosmic-ray induced chemistry in OH231.8+4.2 and that other processes (e.g.shocks) play a major role in their formation. For NO, the model abundance, ≃10–6, is compatible with the observed average value; however, the model fails to reproduce the NO abundance enhancement in the high-velocity lobes (relative to the slow core) inferred from the broad NO profiles. The new detections presented in this work corroborate the particularly rich chemistry of OH231.8+4.2, which is likely to be profoundly influenced by shock-induced processes, as proposed in earlier works.

Abstract Copyright:

Journal keyword(s): astrochemistry - line: identification - molecular processes - stars: AGB and post-AGB - circumstellar matter

CDS comments: Fig.1 clumps INa not in SIMBAD.

Simbad objects: 13

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Number of rows : 13

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 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
2 NAME Taurus Complex SFR 04 41.0 +25 52           ~ 3532 0
3 TMC-1 MoC 04 41 45.9 +25 41 27           ~ 1372 0
4 RAFGL 618 pA* 04 42 53.6245215366 +36 06 53.397219192   16.32   12.59   C-rich 958 0
5 NAME ORI MOL CLOUD MoC 05 56 -01.8           ~ 862 1
6 V* VY CMa s*r 07 22 58.32877 -25 46 03.2355 12.01 10.19 7.95     M5Iae 1002 0
7 NGC 2437 OpC 07 41 46 -14 48.6           ~ 139 0
8 OH 231.8 +4.2 OH* 07 42 16.947 -14 42 50.20           M10III+A 505 1
9 IRC +10216 C* 09 47 57.40632 +13 16 43.5648     10.96     C9,5e 2147 0
10 HD 99647 * 11 28 02.0642127389 +11 58 23.144733258 10.010 8.120 6.560     K2 15 0
11 NAME Sgr B2 MoC 17 47 20.4 -28 23 07           ~ 1937 1
12 IRC +10420 pA* 19 26 48.0981288433 +11 21 16.756524951   13.98 11.66     F8Ia+e 453 0
13 [DE95] LDN 1157 B2 out 20 39 09.3 +68 00 44           ~ 61 0

    Equat.    Gal    SGal    Ecl

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2020.09.28-09:01:41

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