Universität zu Köln

Tafoya, D., Toala, J. A., Vlemmings, W. H. T., Guerrero, M. A., De Beck, E., Gonzalez, M., Kimeswenger, S., Zijlstra, A. A., Sanchez-Monge, A. and Trevino-Morales, S. P. (2017). (Sub)millimeter emission lines of molecules in born-again stars. Astron. Astrophys., 600. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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Abstract

Context. Born-again stars provide a unique possibility to study the evolution of the circumstellar envelope of evolved stars in human timescales. Up until now, most of the observations of the circumstellar material in these stars have been limited to studying the relatively hot gas and dust. In other evolved stars, the emission from rotational transitions of molecules, such as CO, is commonly used to study the cool component of their circumstellar envelopes. Thus, the detection and study of molecular gas in born-again stars is of great importance when attempting to understand their composition and chemical evolution. In addition, the molecular emission is an invaluable tool for exploring the physical conditions, kinematics, and formation of asymmetric structures in the circumstellar envelopes of these evolved stars. However, up until now, all attempts to detect molecular emission from the cool material around born-again stars have failed. Aims. We searched for emission from rotational transitions of molecules in the hydrogen-deficient circumstellar envelopes of born-again stars to explore the chemical composition, kinematics, and physical parameters of the relatively cool gas. Methods. We carried out observations using the APEX and IRAM 30 m telescopes to search for molecular emission toward four well-studied born-again stars, V4334 Sgr, V605 Aql, A30, and A78, that are thought to represent an evolutionary sequence. Results. For the first time, we detected emission from HCN and (IICN)-C-13 molecules toward V4334 Sgr, and CO emission in V605 Aql. No molecular emission was detected above the noise level toward A30 and A78. The detected lines exhibit broad linewidths greater than or similar to 150 km s(-1), which indicates that the emission comes from gas ejected during the born-again event, rather than from the old planetary nebula. A first estimate of the (HCN)-C-12/(HCN)-C-13 abundance ratio in the circumstellar environment of V4334 Sgr is approximate to 3, which is similar to the value of the C-12/C-13 ratio measured from other observations. We derived a rotational temperature of T-rot = 13 +/- 1 K, and a total column density of N-HCN = 1.6 +/- 0.1 x 10(16) cm(-2) for V4334 Sgr. This result sets a lower limit on the amount of hydrogen that was ejected into the wind during the born-again event of this source. For V605 Aql, we obtained a lower limit for the integrated line intensities I-12CO/I-13CO > 4.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Tafoya, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Toala, J. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Vlemmings, W. H. T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Guerrero, M. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED De Beck, E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Gonzalez, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kimeswenger, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Zijlstra, A. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Sanchez-Monge, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Trevino-Morales, S. P. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-234684
DOI:	10.1051/0004-6361/201630074
Journal or Publication Title:	Astron. Astrophys.
Volume:	600
Date:	2017
Publisher:	EDP SCIENCES S A
Place of Publication:	LES ULIS CEDEX A
ISSN:	1432-0746
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language V4334-SGR SAKURAIS-OBJECT; HYDROGEN-POOR EJECTA; PLANETARY-NEBULAE A30; V605 AQUILAE; COLOGNE DATABASE; EVOLUTION; SPECTROSCOPY; A78; SAGITTARII; ABELL-30 Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/23468