XMM-Newton and Chandra X-ray follow-up observations of the VHE gamma-ray source HESS J1507-622

Abstract

The discovery of the unique source HESS J1507-622 in the very high energy (VHE) range (100 GeV-100 TeV) opened newpossibilities to study the parent population of ultra-relativistic particles found in astrophysical sources and underlined the possibilityof new scenarios/mechanisms crucial for understanding the underlying astrophysical processes in nonthermal sources.Aims. The follow-up X-ray (0.2-10 keV) observations on HESS J1507-622 are reported, and possibilities regarding the nature of theVHE source and that of the newly discovered X-ray sources are investigated.Methods. We obtained observations with the X-ray satellites XMM-Newton and Chandra. Background corrections were applied tothe data to search for extended diffuse emission. Since HESS J1507-622 covers a large part of the field of view of these instruments,blank-sky background fields were used.Results. The discovery of several new X-ray sources and a new, faint, extended X-ray source with a flux of ~6×10-14 erg cm-2 s-1 isreported. Interestingly, a new, variable point-like X-ray source with a flux of ~8×10-14 erg cm-2 s-1 appeared in the 2011 observation,which was not detected in the previous X-ray observations.Conclusions. The X-ray observations revealed a faint, extended X-ray source that may be a possible counterpart for HESS J1507-622.This source could be an X-ray pulsar wind nebula (PWN) remnant of the larger gamma-ray PWN, which is still bright in IC emission.Several interpretations are proposed to explain the newly detected variable X-ray source.