Discovery of a high state AM CVn binary in the Galactic Bulge Survey

T. Wevers, M. A.P. Torres, P. G. Jonker, J. D. Wetuski, G. Nelemans, D. Steeghs, T. J. Maccarone, C. Heinke, R. I. Hynes, A. Udalski, Z. Kostrzewa-Rutkowska, P. J. Groot, R. Gazer, M. K. Szymański, C. T. Britt, L. Wyrzykowski, R. Poleski

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We report on the discovery of a hydrogen-deficient compact binary (CXOGBS J175107.6- 294037) belonging to the AM CVn class in the Galactic Bulge Survey. Deep archival X-ray observations constrain the X-ray positional uncertainty of the source to 0.57 arcsec, and allow us to uniquely identify the optical and UV counterpart. Optical spectroscopic observations reveal the presence of broad, shallow He I absorption lines while no sign of hydrogen is present, consistent with a high state system. We present the optical light curve from Optical Gravitational Lensing Experiment monitoring, spanning 15 yr. It shows no evidence for outbursts; variability is present at the 0.2 mag level on time-scales ranging from hours to weeks. A modulation on a time-scale of years is also observed. A Lomb-Scargle analysis of the optical light curves shows two significant periodicities at 22.90 and 23.22 min. Although the physical interpretation is uncertain, such time-scales are in line with expectations for the orbital and superhump periods. We estimate the distance to the source to be between 0.5 and 1.1 kpc. Spectroscopic follow-up observations are required to establish the orbital period, and to determine whether this source can serve as a verification binary for the eLISA gravitational wave mission.

Original languageEnglish
Pages (from-to)L106-L110
JournalMonthly Notices of the Royal Astronomical Society: Letters
Issue number1
StatePublished - Oct 11 2016


  • Accretion, accretion discs
  • Binaries: close
  • CXOGBS J175107.6-294037
  • Stars: evolution
  • White dwarfs
  • X-rays: binaries


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