Discovery of a VHE gamma-ray source coincident with the supernova remnant CTB 37A

¹ Max-Planck-Institut für Kernphysik, PO Box 103980, 69029 Heidelberg, Germany
² Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin 2, Ireland
³ Yerevan Physics Institute, 2 Alikhanian Brothers St., 375036 Yerevan, Armenia
⁴ University of Durham, Department of Physics, South Road, Durham DH1 3LE, UK
⁵ Centre d'Étude Spatiale des Rayonnements, CNRS/UPS, 9 Av. du Colonel Roche, BP 4346, 31029 Toulouse Cedex 4, France
⁶ Landessternwarte, Universität Heidelberg, Königstuhl, 69117 Heidelberg, Germany
⁷ Universität Hamburg, Institut für Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg, Germany
⁸ Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany
⁹ LUTH, Observatoire de Paris, CNRS, Université Paris Diderot, 5 Place Jules Janssen, 92190 Meudon, France
¹⁰ IRFU/DSM/CEA, CE Saclay, 91191 Gif-sur-Yvette Cedex, France
¹¹ Universität Erlangen-Nürnberg, Physikalisches Institut, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany
¹² Nicolaus Copernicus Astronomical Center, Warsaw, Poland
¹³ Unit for Space Physics, North-West University, Potchefstroom 2520, South Africa
¹⁴ Laboratoire d'Astrophysique de Grenoble, INSU/CNRS, Université Joseph Fourier, BP 53, 38041 Grenoble Cedex 9, France
¹⁵ Laboratoire Leprince-Ringuet, École Polytechnique, CNRS/IN2P3, 91128 Palaiseau, France
¹⁶ Laboratoire d'Annecy-le-Vieux de Physique des Particules, CNRS/IN2P3, 9 Chemin de Bellevue, BP 11,0 74941 Annecy-le-Vieux Cedex, France
¹⁷ European Associated Laboratory for Gamma-Ray Astronomy, jointly supported by CNRS and MPG
¹⁸ Astroparticule et Cosmologie (APC), CNRS, UMR 7164, (CNRS, Université Paris VII, CEA, Observatoire de Paris) Université Paris 7 Denis Diderot, 10 rue Alice Domon et Leonie Duquet, 75205 Paris Cedex 13, France
¹⁹ Laboratoire de Physique Théorique et Astroparticules, CNRS/IN2P3, Université Montpellier II, CC 70, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France e-mail: Armand.Fiasson@lpta.in2p3.fr
²⁰ Kavli Institute for Particle Astrophysics and Cosmology, Menlo Park, CA 94025, USA
²¹ School of Physics & Astronomy, University of Leeds, Leeds LS2 9JT, UK
²² Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
²³ Toruń Centre for Astronomy, Nicolaus Copernicus University, Toruń, Poland
²⁴ Université Bordeaux 1, CNRS/IN2P3, Centre d'Études Nucléaires de Bordeaux Gradignan, UMR 5797, Chemin du Solarium, BP 120, 33175 Gradignan, France
²⁵ LPNHE, Université Pierre et Marie Curie Paris 6, Université Denis Diderot Paris 7, CNRS/IN2P3, 4 Place Jussieu, 75252, Paris Cedex 5, France
²⁶ Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka 560-0043, Japan
²⁷ Institute of Particle and Nuclear Physics, Charles University, V Holesovickach 2, 180 00 Prague 8, Czech Republic
²⁸ Obserwatorium Astronomiczne, Uniwersytet Jagielloński, Kraków, Poland
²⁹ School of Chemistry & Physics, University of Adelaide, Adelaide 5005, Australia
³⁰ Institut für Theoretische Physik, Lehrstuhl IV: Weltraum und Astrophysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
³¹ University of Namibia, Private Bag 13301, Windhoek, Namibia

Received: 5 March 2008
Accepted: 20 August 2008

Abstract

Aims. The supernova remnant (SNR) complex CTB 37 is an interesting candidate for observations with very high energy (VHE) γ-ray telescopes such as HESS. In this region, three SNRs are seen. One of them is potentially associated with several molecular clouds, a circumstance that can be used to probe the acceleration of hadronic cosmic rays.

Methods. This region was observed with the HESS Cherenkov telescopes and the data were analyzed with standard HESS procedures. Recent X-ray observations with Chandra and XMM-Newton were used to search for X-ray counterparts.

Results. The discovery of a new VHE γ-ray source HESS J1714-385 coincident with the remnant CTB 37A is reported. The energy spectrum is well described by a power-law with a photon index of Γ = 2.30 ± 0.13 and a differential flux at 1 TeV of cm^-2 s^-1 TeV^-1. The integrated flux above 1 TeV is equivalent to 3% of the flux of the Crab nebula above the same energy. This VHE γ-ray source is a counterpart candidate for the unidentified EGRET source 3EG J1714-3857. The observed VHE emission is consistent with the molecular gas distribution around CTB 37A; a close match is expected in a hadronic scenario for γ-ray production. The X-ray observations reveal the presence of thermal X-rays from the NE part of the SNR. In the NW part of the remnant, an extended non-thermal X-ray source, CXOU J171419.8-383023, is discovered as well. Possible connections of the X-ray emission to the newly found VHE source are discussed.