A Luminous High-Mass Gamma-ray Binary in the Large Magellanic Cloud
Abstract
We have been undertaking a search for gamma-ray binaries from the detection of periodic modulation in light curves from all sources in the Fermi LAT 3FGL catalog. From this search we identified a 10 day modulation in the direction of the LMC. A localization of the modulation indicates that it arises from a point source identified in a recent Fermi-LAT survey of the LMC. The nature and identification of this source had been uncertain. We find that the counterpart is a previously reported candidate high-mass X-ray binary with an O6III(f) primary located in a supernova remnant. Swift XRT observations of this source show modulation on the 10 day gamma-ray period, but with a different epoch of maximum flux. ATCA radio observations (5.5 and 9 GHz) also reveal variable radio emission from this source. Optical spectroscopy (SAAO and SOAR) show that while there are no large changes in the spectrum, there is apparent radial velocity modulation. At all wavebands this new gamma-ray binary is significantly more luminous than comparable Galactic systems, even though very few of these are known. The discovery of this extragalactic gamma-ray binary may have implications for the overall population of gamma-ray binaries and their evolutionary pathways and lifetimes.
- Publication:
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AAS/High Energy Astrophysics Division #15
- Pub Date:
- April 2016
- Bibcode:
- 2016HEAD...1520706C