Discovery Of The New Gamma-ray Binary 1FGL J1018.6-5856
Abstract
We present the discovery of a new gamma-ray binary system from the search for periodic modulation in the 100 MeV to 200 GeV Fermi LAT light curves of all sources in the first Fermi-LAT catalog. 1FGL J1018.6-5856 was found to have a 16.6 day modulation in its gamma-ray light curve that is accompanied by spectral variability. We also identify counterparts in the X-ray, radio and optical wavebands using data from the Swift XRT, ATCA, and telescopes at SAAO and LCO. The X-ray and radio counterparts are highly variable - the X-ray flux is modulated on the orbital period with maximum X-ray flux coinciding with the phase of maximum gamma-ray flux. The optical counterpart has a spectral type of approximately O6V((f)) and shows little variability in a series of Swift UVOT observations. The overall properties of 1FGL J1018.6-5856 indicate that it is a member of the rare gamma-ray binary class of objects, and that it shares several properties with LS 5039. However, there are also several differences from LS 5039, including the relative phasing of the gamma-ray flux and spectral modulation and the shape of the X-ray light curve. The similarities and differences are expected to allow us to more fully develop our understanding of the astrophysics involved in these enigmatic objects.
- Publication:
-
AAS/High Energy Astrophysics Division #12
- Pub Date:
- September 2011
- Bibcode:
- 2011HEAD...12.0307C