Sj. Xue et al., ROSAT/ASCA observations of a serendipitous BL Lacertae object PKS 2316-423: The variable high-energy tail of synchrotron radiation, ASTROPHYS J, 538(1), 2000, pp. 121-126
We present the analysis of archival data from ROSAT and ASCA of a serendipi
tous BL Lac object PKS 2316-423. Because of its featureless nonthermal radi
o/optical continuum, PKS 2316-423 has been called a BL Lac candidate in the
literature. PKS 2316-423 was evidently variable over the multiple X-ray ob
servations; in particular, a variable high-energy tail of the synchrotron r
adiation is revealed. The X-ray spectral analysis provides further evidence
of the synchrotron nature of its broadband spectrum: a steep and downward-
curving spectrum between 0.1 and 10 keV, typical of high-energy peaked BL L
ac objects (HBLs). The spectral energy distribution (SED) through radio to
X-ray yields the synchrotron radiation peak at frequency v(p) = 7.3 x 10(15
) Hz, with integrated luminosity of L-syn = 2.1 x 10(44) ergs s(-1). The av
eraged SED properties of PKS 2316-423 are very similar to those "intermedia
te" BL Lac objects (IBLs) found recently in several deep surveys, such as D
eep X-ray Radio Blazar, Radio-Emitting X-ray, and ROSAT-Green Bank surveys.
We suggest that PKS 2316-423 is an IBL though it also shows some general f
eatures of an HBL. Actually, this double attribute of PKS 2316-423 provides
a good test of the prediction that an IBL object can show either synchrotr
on or inverse Compton characteristics in different variability states.