Two More Candidate AM Canum Venaticorum (AM CVn) Binaries from the Sloan Digital Sky Survey

Astron.J.135:2108-2113,2008 AM CVn systems are a select group of ultracompact binaries with the shortest orbital periods of any known binary subclass; mass-transfer is likely from a low-mass (partially-)degenerate secondary onto a white dwarf primary, driven by gravitational radiation. In the past f...

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Main Authors:	Anderson, S. F, Becker, A. C, Haggard, D, Prieto, J. L, Knapp, G. R, Sako, M, Halford, K. B, Jha, S, Martin, B, Holtzman, J, Frieman, J. A, Garnavich, P. M, Hayward, S, Ivezic, Z, Mukadam, A. S, Sesar, B, Szkody, P, Malanushenko, V, Richmond, M. W, Schneider, D. P, York, D. G
Format:	Journal Article
Language:	English
Published:	15-02-2008
Subjects:	Physics - Astrophysics of Galaxies Physics - Cosmology and Nongalactic Astrophysics Physics - Earth and Planetary Astrophysics Physics - High Energy Astrophysical Phenomena Physics - Instrumentation and Methods for Astrophysics Physics - Solar and Stellar Astrophysics
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Summary:	Astron.J.135:2108-2113,2008 AM CVn systems are a select group of ultracompact binaries with the shortest orbital periods of any known binary subclass; mass-transfer is likely from a low-mass (partially-)degenerate secondary onto a white dwarf primary, driven by gravitational radiation. In the past few years, the Sloan Digital Sky Survey (SDSS) has provided five new AM CVns. Here we report on two further candidates selected from more recent SDSS data. SDSS J1208+3550 is similar to the earlier SDSS discoveries, recognized as an AM CVn via its distinctive spectrum which is dominated by helium emission. From the expanded SDSS Data Release 6 (DR6) spectroscopic area, we provide an updated surface density estimate for such AM CVns of order 10^{-3.1} to 10^{-2.5} per deg^2 for 15<g<20.5. In addition, we present another new candidate AM CVn, SDSS J2047+0008, that was discovered in the course of followup of SDSS-II supernova candidates. It shows nova-like outbursts in multi-epoch imaging data; in contrast to the other SDSS AM CVn discoveries, its (outburst) spectrum is dominated by helium absorption lines, reminiscent of KL Dra and 2003aw. The variability selection of SDSS J2047+0008 from the 300 deg^2 of SDSS Stripe 82 presages further AM CVn discoveries in future deep, multicolor, and time-domain surveys such as LSST. The new additions bring the total SDSS yield to seven AM CVns thus far, a substantial contribution to this rare subclass, versus the dozen previously known.
DOI:	10.48550/arxiv.0802.2240