XMM-Newton observations of the first unidentified TeV gamma-ray sourceTeV J2032+4130

• Published in: Astronomy and astrophysics (Berlin) Vol. 469; no. 1; pp. L17 - L21
• Main Authors: Horns, D., Hoffmann, A. I. D., Santangelo, A., Aharonian, F. A., Rowell, G. P.
• Format: Journal Article
• Language: English
• Published: EDP Sciences 01.07.2007
• Subjects: acceleration of particles; gamma rays: observations; gamma rays: theory; X-rays: general
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361:20066836

Context.The first unidentified very high energy gamma ray source (TeV J2032+4130) in the Cygnus region has been the subject of intensive search for a counterpart source at other wavelengths. In particular, observations in radio and X-rays are important to trace a population of non-thermal electrons. Aims.A deep (≈50 ks) exposure of TeV J2032+4130 with XMM-Newton has been obtained. The large collection area and the field of view of the X-ray telescopes on-board of XMM-Newton allow to search for faint extended X-ray emission possibly linked to TeV J2032+4130. Methods.The contribution of point sources to the observed X-ray emission from TeV J2032+4130 is subtracted from the data. The point-source subtracted X-ray data are analyzed using blank sky exposures and regions adjacent to the position of TeV J2032+4130 in the field of view covered by the XMM-Newton telescopes to search for diffuse X-ray emission. Results.An extended X-ray emission region with a full width half maximum (FWHM) size of ≈12 arcmin is found. The centroid of the emission is co-located with the position of TeV J2032+4130. The angular extension of the X-ray emission region is slightly smaller than the angular size of TeV J2032+4130 (FWHM =14 ± 3 arcmin). The energy spectrum of the emission coinciding with the position and extension of TeV J2032+4130 can be modeled by a power-law model with a photon index Γ=1.5 ± 0.2stat ± 0.3sys and an energy flux integrated between 2 and 10 keV of $f_{2-10~{\rm keV}} \approx$ 7$\times$10-13 erg/(cm2 s) which is lower than the very high energy gamma-ray flux observed from TeV J2032+4130. The energy flux detected from the extended emission region is about a factor of two smaller than the summed contribution of the point sources present. The energy spectrum can also be fit with a thermal emission model from an ionized plasma with a temperature $k_{\rm B}T\approx$ 10 keV. Conclusions.We conclude that the faint extended X-ray emission discovered in this observation is the X-ray counterpart of TeV J2032+4130. Formally, it can not be excluded that the extended emission is due to an unrelated population of faint, hot ($k_{\rm B}T\approx$ 10 keV) unresolved point-sources which by chance coincides with the position and extension of TeV J2032+4130. We discuss our findings in the frame of both hadronic and leptonic gamma-ray production scenarios.