Tappert, Claus, Gänsicke, B. T. (Boris T.), Schmidtobreick, Linda, Mennickent, Ronald E. and Navarrete, F. P. (2007) K-band spectroscopy of pre-cataclysmic variables. Astronomy & Astrophysics, Vol.475 (No.2). pp. 575-583. doi:10.1051/0004-6361:20077679 ISSN 0004-6361.

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Abstract

Aims. There exists now substantial evidence for abundance anomalies in a number of cataclysmic variables (CVs), indicating that the photosphere of the secondary star incorporates thermonuclear processed material. However, the spectral energy distribution in CVs is usually dominated by the radiation produced by the accretion process, severely hindering an investigation of the stellar components.
On the other hand, depending on how the secondary star has acquired such material, the above mentioned abundance anomalies could also be present in pre-CVs, i.e. detached white/red dwarf binaries that will eventually evolve into CVs, but have not yet started mass transfer, and therefore allow for an unobstructed view on the secondary star at infrared wavelengths.
Methods. We have taken K-band spectroscopy of a sample of 13 pre-CVs in order to examine them for anomalous chemical abundances. In particular, we study the strength of the 12CO and 13CO absorption bands that have been found diminished and enhanced, respectively, in similar studies of CVs.
Results. All our systems show CO abundances that are within the range observed for single stars. The weakest 12CO bands with respect to the spectral type are found in the pre-CV BPM 71214, although on a much smaller scale than observed in CVs. Furthermore there is no evidence for enhanced 13CO. Taking into account that our sample is subject to the present observational bias that favours the discovery of young pre-CVs with secondary stars of late spectral types, we can conclude the following: 1) our study provides
observational proof that the CO anomalies discovered in certain CVs are not due to any material acquired during the common envelope phase, and 2) if the CO anomalies in certain CVs are not due to accretion of processed material during nova outburst, then the progenitors of these CVs are of a significantly different type than the currently known sample of pre-CVs.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science, Engineering and Medicine > Science > Physics
Library of Congress Subject Headings (LCSH):	Cataclysmic variable stars, Stars -- Spectra, Carbon monoxide
Journal or Publication Title:	Astronomy & Astrophysics
Publisher:	EDP Sciences
ISSN:	0004-6361
Official Date:	November 2007
Dates:	Date Event November 2007 Published
Volume:	Vol.475
Number:	No.2
Page Range:	pp. 575-583
DOI:	10.1051/0004-6361:20077679
Status:	Peer Reviewed
Access rights to Published version:	Open Access (Creative Commons)
Funder:	Fondo Nacional de Desarrollo Científico y Tecnológico (Chile) (FONDECYT), Particle Physics and Astronomy Research Council (Great Britain) (PPARC), United States. National Aeronautics and Space Administration (NASA), National Science Foundation (U.S.) (NSF)
Grant number:	1051078 (FONDECYT)

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