Discovery of a Radio Supernova Remnant and Nonthermal X-Rays Coincident with the TeV Source HESS J1813-178

Abstract

We present the discovery of nonthermal radio and X-ray emission positionally coincident with the TeV gammaray source HESS J1813Ϫ178. We demonstrate that the nonthermal radio emission is due to a young shell-type supernova remnant (SNR), G12.8Ϫ0.0, and constrain its distance to be greater than 4 kpc. The X-ray emission is primarily nonthermal and is consistent with either an SNR shell or unidentified pulsar or pulsar wind nebula origin; pulsed emission is not detected in archival ASCA data. A simple synchrotron plus inverse Compton model for the broadband emission assuming that all of the emission arises from the SNR shell implies maximum energies of [B/(10 mG)] Ϫ0.5 TeV. Further observations are needed in order to confirm that the broadband emission has a common origin and to better constrain the X-ray spectrum.

The INTEGRAL – HESS/MAGIC connection: A new class of cosmic high energy accelerators from keV to TeV

“…Independently, and at the same time, INTEGRAL discovered a new soft gammaray source, namely IGR J18135-1751, identified as the counterpart of HESS J1813-178. This high energy emitter, whose nature was still mysterious at the time of the discovery was then associated with the supernova remnant (SNR) G12.82 0.02 [18,6,10]. Even if a chance coincidence cannot be completely ruled out in view of the 2 arcmin INTEGRAL error box and the possible angular extension in the high energy, the overall characteristics of this star forming region [7] comprising SNR G12.82 0.02 are consistent with supernova/plerion origin.…”

“…Details are given in [3]. Radio data are from the VLA, Bonn, Parkes, and Nobeyama observatories [6]; X-ray and hard X-ray data are from ASCA [6] and INTEGRAL [18] out the need of any normalisation, confirm that HESS J1813-178 has a point like X-ray counterpart with a power law emission from 2 to 100 keV and an associated radio counterpart. The data set is strongly suggesting that it is a non-thermal source, possibly accelerating electrons and positrons which radiate through synchrotron and inverse Compton mechanism.…”

“…(2005) have provided a possible interpretation of the HESS/ASCA spectrum by fitting the broadband emission assuming that all the flux originates from the shell of SNR G12.8 (see Fig. 5 and [6], for a detailed description). The two proposed models (corresponding to two different Nh absorption values) are shown by the red and blue lines that provide the best fit to the data.…”

Using X‐ray observations to identify the particle acceleration mechanisms in VHE SNRs and “dark” VHE sources

“…For those, a unique identification with the shells is however not possible based on the VHE and radio data alone. For HESS J1813-178 and HESS J1640-465, the SNR shells G12.8-0.0 (Brogan et al 2005) and G338.3-0.0 (Whiteoak & Green 1996) are too compact to be resolved in the VHE band. Those remnants were however easily investigated in single XMM-Newton pointings (Funk et al 2007b(Funk et al , 2007a.…”

Associations of very high energy gamma-ray sources discovered by H.E.S.S. with pulsar wind nebulae

“…Another possible such association is with HESS J1813-178; this relatively compact VHE source was discovered in the Galactic plane survey [13], and was subsequently found to be coincident with a shell-type radio SNR, G 12.82-0.02 [23,24], and a bright, non-thermal, hard X-ray source [23,25]. The angular resolution of H.E.S.S.…”