Evidence for emission in the MeV band from GRO J1837+59 and QSO 1739+522

Abstract

Emission in the MeV band from the region containing the bright unidentified EGRET source GRO J1837+59 and the steep-spectrum EGRET blazar QSO 1739+522 was first reported by COMPTEL following an observation in November 1992. During this observation the emission was consistent with a single point source, designated GRO J1753+57. However, the location of GRO J1753+57 was not consistent with either GRO J1837+59 or QSO 1739+522 and identifying its counterpart in other wavelengths proved difficult. Moreover, subsequent observations suggested that the source could not in fact be described as a single point source and explanations involving extended or multiple sources were invoked. We present an analysis of recent observations of this region, which confirm that the emission cannot arise from a single source, but can be modelled as a combination of emission from both GRO J1837+59 and QSO 1739+522. The spectrum and time variability derived for these two sources are discussed and compared to observations in neighboring bands.