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SDSS J080449.49+161624.8: a peculiar AM CVn star from a colour-selected sample of candidates

Roelofs, G. H. A. and Groot, P. J. and Steeghs, D. and Rau, A. and de Groot, E. and Marsh, T. R. and Nelemans, G. and Liebert, J. and Woudt, P. (2009) SDSS J080449.49+161624.8: a peculiar AM CVn star from a colour-selected sample of candidates. Monthly Notices of the Royal Astronomical Society, 394 (1). pp. 367-374. ISSN 0035-8711.

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We describe a spectroscopic survey designed to uncover an estimated ~40 AM Canum Venaticorum (AM CVn) stars hiding in the photometric data base of the Sloan Digital Sky Survey. We have constructed a relatively small sample of about 1500 candidates based on a colour selection, which should contain the majority of all AM CVn binaries while remaining small enough that spectroscopic identification of the full sample is feasible. We present the first new AM CVn star discovered using this strategy, SDSS J080449.49+161624.8, the ultracompact binary nature of which is demonstrated using high-time-resolution spectroscopy obtained with the Magellan telescopes at Las Campanas Observatory, Chile. A kinematic 'S-wave' feature is observed on a period P_(orb)= 44.5 ± 0.1 min , which we propose is the orbital period, although the present data cannot yet exclude its nearest daily aliases. The new AM CVn star shows a peculiar spectrum of broad, single-peaked helium emission lines with unusually strong series of ionized helium, reminiscent of the (intermediate) polars among the hydrogen-rich cataclysmic variables. We speculate that SDSS J0804+1616 may be the first magnetic AM CVn star. The accreted material appears to be enriched in nitrogen, to N/O ≳ 10 and N/C > 10 by number, indicating CNO cycle hydrogen burning, but no helium burning, in the prior evolution of the donor star.

Item Type:Article
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URLURL TypeDescription
Groot, P. J.0000-0002-4488-726X
Rau, A.0000-0001-5990-6243
Marsh, T. R.0000-0002-2498-7589
Additional Information:No claim to original US government works. Journal compilation © 2009 RAS. Accepted 2008 November 23. Received 2008 November 21; in original form 2008 November 2. GHAR is supported by NWO Rubicon grant 680.50.0610. DS acknowledges a STFC Advanced Fellowship. GN is supported by the Netherlands Organization for Scientific Research. Based on data taken with the Magellan Telescopes at Las Campanas Observatory, Chile, and with the Isaac Newton Telescope in the Observatorio del Roque de los Muchachos of the Instituto de Astrofısica de Canarias, Spain. This study makes use of the SDSS, see for the full acknowledgment. Special thanks to P. Berlind and the 1.5-m telescope crew at F.L. Whipple Observatory (a facility of the Smithsonian Institution) for their valuable contribution and to L. Yungelson for helpful discussion. Fig. 1 makes use of white-dwarf model spectra kindly provided by D. Koester.
Funding AgencyGrant Number
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)680.50.0610
Science and Technology Facilities CouncilUNSPECIFIED
Subject Keywords:accretion, accretion discs; binaries: close; stars: individual: SDSS J080449.49+161624.8; novae, cataclysmic variables; white dwarfs
Issue or Number:1
Record Number:CaltechAUTHORS:20090922-081255823
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15987
Deposited By: Tony Diaz
Deposited On:28 Sep 2009 16:35
Last Modified:22 Nov 2019 05:32

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