Issue |
A&A
Volume 542, June 2012
|
|
---|---|---|
Article Number | A94 | |
Number of page(s) | 10 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/201218910 | |
Published online | 13 June 2012 |
Discovery of VHE γ-ray emission and multi-wavelength observations of the BL Lacertae object 1RXS J101015.9 − 311909⋆
1 Universität Hamburg, Institut für Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg, Germany
2 Laboratoire Univers et Particules de Montpellier, Université Montpellier 2, CNRS/IN2P3, CC 72, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
3 Max-Planck-Institut für Kernphysik, PO Box 103980, 69029 Heidelberg, Germany
4 Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland
5 National Academy of Sciences of the Republic of Armenia, Yerevan, Armenia
6 Yerevan Physics Institute, 2 Alikhanian Brothers St., 375036 Yerevan, Armenia
7 Universität Erlangen-Nürnberg, Physikalisches Institut, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany
8 Nicolaus Copernicus Astronomical Center, ul. Bartycka 18, 00-716 Warsaw, Poland
9 CEA Saclay, DSM/IRFU, 91191 Gif-Sur-Yvette Cedex, France
10 University of Durham, Department of Physics, South Road, Durham DH1 3LE, UK
11 Astroparticule et Cosmologie (APC), CNRS, Université Paris 7 Denis Diderot, 10 rue Alice Domon et Léonie Duquet, 75205 Paris Cedex 13, France
(UMR 7164: CNRS, Université Paris VII, CEA, Observatoire de Paris)
e-mail: Yvonne.Becherini@apc.univ-paris7.fr
12 Laboratoire Leprince-Ringuet, École Polytechnique, CNRS/IN2P3, 91128 Palaiseau, France
13 Institut für Theoretische Physik, Lehrstuhl IV: Weltraum und Astrophysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
14 Landessternwarte, Universität Heidelberg, Königstuhl, 69117 Heidelberg, Germany
e-mail: jean-philippe.lenain@lsw.uni-heidelberg.de
15 Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany
16 LUTH, Observatoire de Paris, CNRS, Université Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France
e-mail: Matteo.Cerruti@obspm.fr
17 LPNHE, Université Pierre et Marie Curie Paris 6, Université Denis Diderot Paris 7, CNRS/IN2P3, 4 place Jussieu, 75252 Paris Cedex 5, France
18 Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
19 Astronomical Observatory, The University of Warsaw, Al. Ujazdowskie 4, 00-478 Warsaw, Poland
20 Unit for Space Physics, North-West University, Potchefstroom 2520, South Africa
21 Laboratoire d’Annecy-le-Vieux de Physique des Particules, Université de Savoie, CNRS/IN2P3, 74941 Annecy-le-Vieux, France
22 Oskar Klein Centre, Department of Physics, Stockholm University, Albanova University Center, 10691 Stockholm, Sweden
23 University of Namibia, Department of Physics, Private Bag 13301, Windhoek, Namibia
24 Laboratoire d’Astrophysique de Grenoble, INSU/CNRS, Université Joseph Fourier, BP 53, 38041 Grenoble Cedex 9, France
25 Department of Physics and Astronomy, The University of Leicester, University Road, Leicester, LE1 7RH, UK
26 Instytut Fizyki Jądrowej PAN, ul. Radzikowskiego 152, 31-342 Kraków, Poland
27 Institut für Astro- und Teilchenphysik, Leopold-Franzens-Universität Innsbruck, 6020 Innsbruck, Austria
28 Obserwatorium Astronomiczne, Uniwersytet Jagielloński, ul. Orla 171, 30-244 Kraków, Poland
29 Toruń Centre for Astronomy, Nicolaus Copernicus University, ul. Gagarina 11, 87-100 Toruń, Poland
30 School of Chemistry & Physics, University of Adelaide, Adelaide 5005, Australia
31 Charles University, Faculty of Mathematics and Physics, Institute of Particle and Nuclear Physics, V Holešovičkách 2, 180 00 Prague 8, Czech Republic
32 School of Physics & Astronomy, University of Leeds, Leeds LS2 9JT, UK
33 European Associated Laboratory for Gamma-Ray Astronomy, jointly supported by CNRS and MPG
Received: 30 January 2012
Accepted: 31 March 2012
1RXS J101015.9 − 311909 is a galaxy located at a redshift of z = 0.14 hosting an active nucleus (called AGN) belonging to the class of bright BL Lac objects. Observations at high (HE, E > 100 MeV) and very high (VHE, E > 100 GeV) energies provide insights into the origin of very energetic particles present in such sources and the radiation processes at work. We report on results from VHE observations performed between 2006 and 2010 with the H.E.S.S. instrument, an array of four imaging atmospheric Cherenkov telescopes. H.E.S.S. data have been analysed with enhanced analysis methods, making the detection of faint sources more significant. VHE emission at a position coincident with 1RXS J101015.9 − 311909 is detected with H.E.S.S. for the first time. In a total good-quality livetime of about 49 h, we measure 263 excess counts, corresponding to a significance of 7.1 standard deviations. The photon spectrum above 0.2 TeV can be described by a power-law with a photon index of Γ = 3.08 ± 0.42stat ± 0.20sys. The integral flux above 0.2 TeV is about 0.8% of the flux of the Crab nebula and shows no significant variability over the time reported. In addition, public Fermi/LAT data are analysed to search for high energy emission from the source. The Fermi/LAT HE emission in the 100 MeV to 200 GeV energy range is significant at 8.3 standard deviations in the chosen 25-month dataset. UV and X-ray contemporaneous observations with the Swift satellite in May 2007 are also reported, together with optical observations performed with the atom telescope located at the H.E.S.S. site. Swift observations reveal an absorbed X-ray flux of F(0.3-7) keV = 1.04+0.04-0.05 × 10-11 erg cm-2 s-1 in the 0.3 − 7 keV range. Finally, all the available data are used to study the multi-wavelength properties of the source. The spectral energy distribution (SED) can be reproduced using a simple one-zone Synchrotron Self Compton (SSC) model with emission from a region with a Doppler factor of 30 and a magnetic field between 0.025 and 0.16 G. These parameters are similar to those obtained for other sources of this type.
Key words: gamma rays: galaxies / galaxies: active / BL Lacertae objects: individual: 1RXS J101015.9-311909
The data points from the light curves and the spectra are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/542/A94
© ESO, 2012
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