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A Census of AM CVn Stars: Three New Candidates and One Confirmed 48.3-Minute Binary

Rau, A. and Roelofs, G. H. A. and Groot, P. J. and Marsh, T. R. and Nelemans, G. and Steeghs, D. and Salvato, M. and Kasliwal, M. M. (2010) A Census of AM CVn Stars: Three New Candidates and One Confirmed 48.3-Minute Binary. Astrophysical Journal, 708 (1). pp. 456-461. ISSN 0004-637X.

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We present three new candidate AM CVn binaries, and one confirmed new system, from a spectroscopic survey of color-selected objects from the Sloan Digital Sky Survey (SDSS). All four systems were found from their helium emission lines in low-resolution spectra taken on the Hale telescope at Palomar, the Nordic Optical Telescope, and the William Herschel Telescope on La Palma. The ultra-compact binary nature of SDSS J090221.35+381941.9 was confirmed using phase-resolved spectroscopy at the Keck-I telescope. From the characteristic radial velocity "S-wave" observed in the helium emission lines, we measure an orbital period of 48.31 ± 0.08 minutes. The continuum emission can be described with a blackbody or a helium white dwarf atmosphere of T_(eff) ~ 15,000 K, in agreement with theoretical cooling models for relatively massive accretors and/or donors. The absence in the spectrum of broad helium absorption lines from the accreting white dwarf suggests that the accreting white dwarf cannot be much hotter than 15,000 K, or that an additional component such as the accretion disk contributes substantially to the optical flux. Two of the candidate systems, SDSS J152509.57+360054.5 and SDSS J172102.48+273301.2, do show helium absorption in the blue part of their spectra in addition to the characteristic helium emission lines. This in combination with the high effective temperatures of ~18,000 K and ~16,000 K suggests both to be at orbital periods below ≈40 minutes. The third candidate, SDSS J164228.06+193410.0, exhibits remarkably strong helium emission on top of a relatively cool (T_(eff) ~ 12,000 K) continuum, indicating an orbital period above ~50 minutes.

Item Type:Article
Related URLs:
URLURL TypeDescription
Rau, A.0000-0001-5990-6243
Groot, P. J.0000-0002-4488-726X
Marsh, T. R.0000-0002-2498-7589
Salvato, M.0000-0001-7116-9303
Kasliwal, M. M.0000-0002-5619-4938
Additional Information:© 2010 American Astronomical Society. Print publication: Issue 1 (2010 January 1); received 2009 September 23; accepted for publication 2009 November 11; published 2009 December 11. A.R. acknowledges support through NASA grant NNX08AK66G. G.H.A.R. is supported by NWO Rubicon grant 680.50.0610. D.S. acknowledges a STFC Advanced Fellowship. This paper is based on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration (NASA). The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. We also acknowledge use of the Palomar Hale-5 m telescope operated by the California Institute of Technology and Palomar Observatory; the Nordic Optical Telescope and the William Herschel Telescope, La Palma; and the GALEX public archive. We are grateful to D. Koester for kindly making available his white dwarf atmosphere models.
Funding AgencyGrant Number
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)680.50.0610
Science and Technology Facilities Council (STFC)UNSPECIFIED
Subject Keywords:accretion, accretion disks; binaries: close; novae, cataclysmic variables; stars: individual (SDSS J090221.34+381941.9, SDSS J152509.57+360054.5, SDSS J164228.06+193410.0, SDSS J172102.48+273301.2); white dwarfs
Issue or Number:1
Record Number:CaltechAUTHORS:20100120-105330821
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Official Citation:A Census of AM CVn Stars: Three New Candidates and One Confirmed 48.3-Minute Binary A. Rau, G. H. A. Roelofs, P. J. Groot, T. R. Marsh, G. Nelemans, D. Steeghs, M. Salvato, and M. M. Kasliwal 2010 ApJ 708 456-461 doi: 10.1088/0004-637X/708/1/456
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17238
Deposited By: Jason Perez
Deposited On:20 Jan 2010 21:57
Last Modified:22 Nov 2019 00:56

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