Abstract

There are a number of unassociated sources along the Galactic plane among the Fermi-LAT detected gamma-ray sources. They are very interesting since some of them are expected to be gamma-ray binaries or microquasors. The sample of these types of gamma-ray objects is still not rich, and therefore it is important to increase their sample number by multiwavelength observations. We chose three GeV gamma-ray Fermi unassociated sources at low Galactic latitude from the Fermi LAT first year catalog, based on the condition that their ROSAT HRI hardness ratio is large and a radio and optical counterpart has been found. Known gamma-ray binaries, LS I+61 303, LS 5039, and Cyg X-3, also satisfy these properties. We observed these three objects (1RXS J013106.4+612035, J194246.3+103339, J135341.1-664002) with the Suzaku satellite and the Kanata telescope in the X-ray and optical band, respectively. They are detected, and two of them show a time variability in the optical band. Their SED has two components and it is similar to those of BL Lac objects. We discuss these properties and the possible nature of these sources.