Astronomy and Astrophysics, volume 631A, 150-150 (2019/11-1)
The γ-ray sky seen at X-ray energies. I. Searching for the connection between X-rays and γ-rays in Fermi BL Lac objects.
MARCHESINI E.J., PAGGI A., MASSARO F., MASETTI N., D'ABRUSCO R., ANDRUCHOW I. and DE MENEZES R.
Abstract (from CDS):
Context. BL Lac objects are an extreme type of active galactic nuclei (AGNs) that belong to the largest population of γ-ray sources: blazars. This class of AGNs shows a double-bumped spectral energy distribution that is commonly described in terms of a synchrotron self-Compton (SSC) emission process, whereas the low-energy component that dominates their emission between the infrared and the X-ray band is tightly connected to the high-energy component that peaks in the γ-rays. Two strong connections that link radio and mid-infrared emission of blazars to the emission in the γ-ray band are well established. They constitute the basis for associating γ-ray sources with their low-energy counterparts.
Aims. We searched for a possible link between X-ray and γ-ray emissions for the subclass of BL Lacs using all archival Swift/XRT observations combined with Fermi data for a selected sample of 351 sources.
Methods. Analyzing ∼2400ks of Swift/XRT observations that were carried out until December 2018, we discovered that above the γ-ray flux threshold Fγ~=3x10–12erg/cm2/s, 96% of all Fermi BL Lacs have an X-ray counterpart that is detected with signal-to-noise ratio >3.
Results. We did not find any correlation or clear trend between X-ray and γ-ray fluxes and/or spectral shapes, but we discovered a correlation between the X-ray flux and the mid-infrared color. Finally, we discuss on a possible interpretation of our results in the SSC framework.
© ESO 2019
galaxies: active - galaxies: nuclei - galaxies: jets - BL Lacertae objects: general - X-rays: galaxies - gamma rays: galaxies
VizieR on-line data:
<Available at CDS (J/A+A/631/A150): table1.dat>
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