Chin Ping Hu, Ting Chang Yang, Yi Chou, L. Liu, S. B. Qian, C. Y. Hui, Albert K.H. Kong, L. C.C. Lin, P. H.T. Tam, K. L. Li, Chow Choong Ngeow, W. P. Chen, Wing Huen Ip

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5 Scopus citations


We report the detection of orbital modulation, a model solution, and the X-ray properties of a newly discovered contact binary, Two Micron All Sky Survey (2MASS) J11201034-2201340. We serendipitously found this X-ray point source outside the error ellipse when searching for possible X-ray counterparts of γ-ray millisecond pulsars among the unidentified objects detected by the Fermi Gamma-ray Space Telescope. The optical counterpart of the X-ray source (unrelated to the γ-ray source) was then identified using archival databases. The long-term Catalina Real-Time Transient Survey detected a precise signal with a period of days. A follow-up observation made by the Super Light Telescope of Lulin Observatory revealed the binary nature of the object. Utilizing archived photometric data of multi-band surveys, we construct the spectral energy distribution (SED), which is well fit by a K2V spectral template. The fitting result of the orbital profile using the Wilson-Devinney code suggests that 2MASS J11201034-2201340 is a short-period A-type contact binary and the more massive component has a cool spot. The X-ray emission was first noted in observations made by Swift, and then further confirmed and characterized by an XMM-Newton observation. The X-ray spectrum can be described by a power law or thermal Bremsstrahlung. Unfortunately, we could not observe significant X-ray orbital modulation. Finally, according to the SED, this system is estimated to be 690 pc from Earth with a calculated X-ray intensity of erg s-1, which is in the expected range of an X-ray emitting contact binary.

Original languageEnglish
Article number170
JournalAstronomical Journal
Issue number6
StatePublished - Jun 2016


  • X-rays: stars
  • binaries: close
  • binaries: eclipsing
  • stars: individual (2MASS J11201034-2201340)


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