The BL Lacertae objects OQ 530 and S5 0716+714

Abstract

Abstract. We present the results of the BeppoSAX observations of two BL Lacs, OQ 530 and S5 0716+714, as part of a ToO program for the simultaneous observation at radio, optical, X-ray and TeV energies. Both sources are detected in the LECS and MECS, with S5 0716+714 visible also in the PDS band, up to about ∼60 keV. The X-ray spectra of both sources are better fitted by a double power-law model, with a steep soft X-ray component flattening at harder energies, with breaks at 0.3 and 1.5 keV, respectively. The concave shape of the spectra in both objects is consistent with soft X-rays being produced by the synchrotron and harder X-rays by the inverse Compton processes. Also the X-ray variability properties confirm this scenario; in particular, for S5 0716+714 our observation shows variations by about a factor of 3 over one hour below ∼3 keV and no variability above. Their simultaneous broad-band energy spectral distributions can be successfully interpreted within the frame of a homogeneous synchrotron and inverse Compton model, including a possible contribution from an external source of seed photons with the different spectral states of S5 0716+714 being reproduced by changing the injected power. The resulting parameters are fully consistent with the two sources being intermediate objects within the "sequence" scenario proposed for blazars.

Signature of inverse Compton emission from blazars

“…Similar spectral upturns are found in previous studies also i.e. 3C 66A (Donato et al 2005, Wierzcholska & Wagner 2016; S5 0716+714 (Giommi et al 1999;Tagliaferri et al2003;Donato et al 2005;Ferrero et al 2006;Wierzcholska & Siejkowski 2015); ON 231 (Tagliaferri et al 2000); BL Lacertae (Tanihata et al 2000;Ravasio et al 2002); AO 0235+164 (Raiteri et al 2006); OQ 530 (Tagliaferri et al 2003); 4C +21.35 (Wierzcholska & Wagner 2016). For the well known HBL Mrk 421, Kataoka & Stawarz (2016) found that the X-ray observations from NuStar Satellite is dominated by the highest-energy tail of the synchrotron continuum till 20 keV and the variable excess hard X-ray emission is related to inverse Compton emission in its very low state.…”

“…In ISP blazars, there is a clear turning point in the SED where synchrotron and inverse Compton components intersect e.g. S5 0716+714 ( Giommi et al 1999;Tagliaferri et al 2003;Donato et al 2005;Ferrero et al 2006;Wierzcholska & Siejkowski 2015); ON 231 (Tagliaferri et al 2000); BL Lacertae (Tanihata et al 2000;Ravasio et al 2002); AO 0235+164 (Raiteri et al 2006); OQ 530 (Tagliaferri et al 2003); 3C 66A (Donato et al 2005;Wierzcholska & Wagner 2016); 4C +21.35 (Wierzcholska & Wagner 2016), amongst others.…”

Synchrotron Self‐Compton Analysis of TeV X‐Ray‐Selected BL Lacertae Objects

“…Blazars vary on timescales from days to months at radio frequencies (e.g., Böttcher et al 2003;Villata et al 2004), and on timescales as short as a few hours or less at X-ray/ -ray energies (e.g., Tagliaferri et al 2003;Foschini et al 2006). Photoabsorption arguments (Maraschi et al 1992) and observations of superluminal motions (Vermeulen & Cohen 1994) show that the emission region is moving with relativistic speeds.…”

The continuum spectral features of blazars in the optical region

“…Shown in the upper part of the plot are the SED of 3C 279 (PKS 1253−05, z = 0.5362) a typical FSRQ (data also from Reuter et al 1997;Wehrle et al 1998), and the SED of OJ 287 (PG 0851+202, z = 0.306), a typical LBL (data also from Idesawa et al 1997;Massaro et al 2003). Shown in the mid part of the plot are the SEDs of three LBL-intermediate blazars: GC 0109+224 (S2 0109+22, z > 0.4, data from Ciprini et al 2004), S5 0716+71 (1H 0717+714, z > 0.3, data also from Tagliaferri et al 2003), and W Comae (ON 231, z = 0.102, data also from Tagliaferri et al 2000). In the lower part of the plot, the SEDs of two typical HBL and TeV-blazars: 1ES 2344+514 (z = 0.044), and Mrk 421 (B2 1101+38, z = 0.03, data also from Takahashi et al 2000;Maraschi et al 1999).…”