A CENSUS OF AM CVn STARS: THREE NEW CANDIDATES AND ONE CONFIRMED 48.3-MINUTE BINARY

Journal Article · Fri Jan 01 00:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/708/1/456· OSTI ID:21392476

Rau, A ^[1]; Roelofs, G H. A.; Steeghs, D ^[2]; Groot, P J; Nelemans, G ^[3]; Marsh, T R ^[4]; Salvato, M

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1. Max-Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, Garching 85748 (Germany)
2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
3. Department of Astrophysics, IMAPP, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen (Netherlands)
4. Department of Physics, University of Warwick, Coventry CV4 7Al (United Kingdom)

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{sub eff} approx 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 approx18,000 K and approx16,000 K suggests both to be at orbital periods below approx40 minutes. The third candidate, SDSS J164228.06+193410.0, exhibits remarkably strong helium emission on top of a relatively cool (T{sub eff} approx 12,000 K) continuum, indicating an orbital period above approx50 minutes.

• OSTI ID: 21392476
• Journal Information: Astrophysical Journal, Vol. 708, Issue 1; Other Information: DOI: 10.1088/0004-637X/708/1/456; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABSORPTION
ACCRETION DISKS
ATMOSPHERES
COLOR
EMISSION
HELIUM
NOVAE
RADIAL VELOCITY
SPECTRA
SPECTROSCOPY
TELESCOPES
WHITE DWARF STARS
BINARY STARS
DWARF STARS
ELEMENTS
ERUPTIVE VARIABLE STARS
FLUIDS
GASES
NONMETALS
OPTICAL PROPERTIES
ORGANOLEPTIC PROPERTIES
PHYSICAL PROPERTIES
RARE GASES
SORPTION
STARS
VARIABLE STARS
VELOCITY