ASCA/ROSAT observations of PKS 2316-423: Spectral properties of a low luminosity intermediate-type BL lac object

Abstract

We present the analysis of archival data from ROSAT and ASCA of a serendipitous source PKS 2316-423. According to its featureless non-thermal radio/optical continuum, the object has been assumed as a BL Lac candidate in the literature. PKS 2316-423 was evident variable over the multiple X-ray observations. Specially, a variable high-energy tail of the synchrotron radiation is revealed. X-ray spectral analysis provided further evidence of its synchrotron-nature broad-band spectrum with steep and down-curved shape in the range of 0.1–10 keV, this is general signature of a HBL. The spectral energy distribution (SED) through radio-to-X-ray yields the synchrotron radiation peak at frequency νp=7.3×1015 Hz, with integrated luminosity of Lsyn=2.1×1044 ergs s−1, this suggest that PKS 2316-423 is a low luminosity BL Lac object with high synchrotron peak frequency. Further SED analysis suggest that PKS 2316-423 is a very low luminosity “intermediate” or high energy peaked BL Lac object. Given the unusual low luminosity, the further studies of PKS 2316-423 might give clues on the evolution properties of BL Lacs.