Chandra and HESS observations of the supernova remnant CTB 37B

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 Centre, 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, Ecole Polytechnique, CNRS/IN2P3, 91128 Palaiseau, France
¹⁶ Laboratoire d'Annecy-le-Vieux de Physique des Particules, CNRS/IN2P3, 9 Chemin de Bellevue, BP 110, 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, Université Paris 7 Denis Diderot, 10, rue Alice Domon et Leonie Duquet, 75205 Paris Cedex 13, France (UMR 7164 (CNRS, Université Paris VII, CEA, Observatoire de Paris))
¹⁹ Laboratoire de Physique Théorique et Astroparticules, CNRS/IN2P3, Université Montpellier II, CC 70, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
²⁰ Kavli Institute for Particle Astrophysics, SLAC, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
²¹ School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK e-mail: phy3j2ls@ast.leeds.ac.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 Institute of Particle and Nuclear Physics, Charles University, V Holesovickach 2, 180 00 Prague 8, Czech Republic
²⁷ Obserwatorium Astronomiczne, Uniwersytet Jagielloński, Kraków, Poland
²⁸ Stanford University, HEPL & KIPAC, Stanford, CA 94305-4085, USA
²⁹ School of Chemistry and 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: 25 February 2008
Accepted: 11 May 2008

Abstract

We discovered the >100 GeV γ-ray source, HESS J1713-381, apparently associated with the shell-type supernova remnant (SNR) CTB 37B, using HESS in 2006. In 2007 we performed X-ray follow-up observations with Chandra with the aim of identifying a synchrotron counterpart to the TeV source and/or thermal emission from the SNR shell. These new Chandra data, together with additional TeV data, allow us to investigate the nature of this object in much greater detail than was previously possible. The new X-ray data reveal thermal emission from a ~4' region in close proximity to the radio shell of CTB 37B. The temperature of this emission implies an age for the remnant of ~5000 years and an ambient gas density of ~0.5 cm^-3. Both these estimates are considerably uncertain due to the asymmetry of the SNR and possible modifications of the kinematics due to efficient cosmic ray (CR) acceleration. A bright (≈ 7 10^-13 erg cm^-2 s^-1) and unresolved (<1″) source (CXOU J171405.7-381031), with a soft (Γ≈3.3) non-thermal spectrum is also detected in coincidence with the radio shell. Absorption indicates a column density consistent with the thermal emission from the shell, suggesting a genuine association rather than a chance alignment. The observed TeV morphology is consistent with an origin in the complete shell of CTB 37B. The lack of diffuse non-thermal X-ray emission suggests an origin of the γ-ray emission via the decay of neutral pions produced in interactions of protons and nuclei, rather than inverse Compton (IC) emission from relativistic electrons.