Issue |
A&A
Volume 655, November 2021
|
|
---|---|---|
Article Number | A7 | |
Number of page(s) | 13 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361/202141486 | |
Published online | 28 October 2021 |
LMC N132D: A mature supernova remnant with a power-law gamma-ray spectrum extending beyond 8 TeV
1
University of Namibia, Department of Physics,
Private Bag 13301,
Windhoek
10005,
Namibia
2
Dublin Institute for Advanced Studies,
31 Fitzwilliam Place,
Dublin 2,
Ireland
3
Max-Planck-Institut für Kernphysik,
PO Box 103980,
69029
Heidelberg,
Germany
4
High Energy Astrophysics Laboratory,
RAU,
123 Hovsep Emin St Yerevan 0051, Armenia
5
Aix Marseille Université, CNRS/IN2P3, CPPM,
Marseille, France
6
Centre for Space Research, North-West University,
Potchefstroom
2520, South Africa
7
Laboratoire d’Annecy de Physique des Particules, Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, LAPP,
74000
Annecy,
France
8
University of Oxford, Department of Physics,
Denys Wilkinson Building, Keble Road,
Oxford
OX1 3RH, UK
9
IRFU, CEA, Université Paris-Saclay,
91191
Gif-sur-Yvette, France
10
Instytut Fizyki Ja̧drowej PAN,
ul. Radzikowskiego 152,
31-342
Kraków,
Poland
11
DESY,
15738
Zeuthen,
Germany
12
Obserwatorium Astronomiczne, Uniwersytet Jagielloński,
ul. Orla 171,
30-244
Kraków, Poland
13
School of Physics, University of the Witwatersrand,
1 Jan Smuts Avenue,
Braamfontein,
Johannesburg
2050, South Africa
14
Department of Physics and Electrical Engineering, Linnaeus University,
351 95
Växjö,
Sweden
15
Institut für Astronomie und Astrophysik, Universität Tübingen,
Sand 1,
72076
Tübingen, Germany
16
Laboratoire Univers et Théories, Observatoire de Paris, Université PSL, CNRS, Université de Paris,
92190
Meudon,
France
17
Sorbonne Université, Université Paris Diderot, Sorbonne Paris Cité, CNRS/IN2P3, Laboratoire de Physique Nucléaire et de Hautes Energies, LPNHE,
4 place Jussieu,
75252
Paris,
France
18
Astronomical Observatory, The University of Warsaw,
Al. Ujazdowskie 4,
00-478
Warsaw,
Poland
19
Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen Centre for Astroparticle Physics,
Erwin-Rommel-Str. 1,
91058
Erlangen, Germany
20
Université Bordeaux, CNRS/IN2P3, Centre d’Études Nucléaires de Bordeaux Gradignan,
33175
Gradignan, France
21
Université de Paris, CNRS, Astroparticule et Cosmologie,
75013
Paris, France
22
Department of Physics and Astronomy, The University of Leicester, University Road,
Leicester,
LE1 7RH, UK
23
Institut für Physik und Astronomie, Universität Potsdam,
Karl-Liebknecht-Strasse 24/25,
14476
Potsdam, Germany
24
School of Physical Sciences, University of Adelaide,
Adelaide
5005, Australia
25
Laboratoire Leprince-Ringuet, École Polytechnique, CNRS, Institut Polytechnique de Paris,
91128
Palaiseau, France
26
Laboratoire Univers et Particules de Montpellier, Université Montpellier, CNRS/IN2P3, CC 72, Place Eugène Bataillon,
34095
Montpellier Cedex 5, France
27
Institut für Astro- und Teilchenphysik, Leopold-Franzens-Universität Innsbruck,
6020
Innsbruck, Austria
28
Universität Hamburg, Institut für Experimentalphysik,
Luruper Chaussee 149,
22761
Hamburg, Germany
29
Landessternwarte, Universität Heidelberg,
Königstuhl,
69117
Heidelberg, Germany
30
Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University,
Grudziadzka 5,
87-100
Torun, Poland
31
Department of Physics, Rikkyo University,
3-34-1 Nishi-Ikebukuro,
Toshima-ku,
Tokyo
171-8501, Japan
32
Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences,
ul. Bartycka 18,
00-716
Warsaw,
Poland
33
Institut für Physik, Humboldt-Universität zu Berlin,
Newtonstr. 15,
12489
Berlin, Germany
34
Department of Physics, University of the Free State,
PO Box 339,
Bloemfontein
9300, South Africa
35
GRAPPA, Anton Pannekoek Institute for Astronomy, University of Amsterdam,
Science Park 904,
1098 XH
Amsterdam, The Netherlands
36
Yerevan Physics Institute,
2 Alikhanian Brothers St.,
375036
Yerevan,
Armenia
37
Department of Physics, The University of Tokyo, 7-3-1 Hongo,
Bunkyo-ku,
Tokyo
113-0033, Japan
38
Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study (UTIAS), The University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa,
Chiba, 277-8583, Japan
39
Department of Physics, Konan University, 8-9-1 Okamoto, Higashinada, Kobe, Hyogo 658-8501, Japan
40
RIKEN, 2-1 Hirosawa, Wako-shi,
Saitama
351-0198, Japan
★ Corresponding authors; e-mail: contact.hess@hess-experiment.eu
Received:
7
June
2021
Accepted:
19
July
2021
Context. Supernova remnants (SNRs) are commonly thought to be the dominant sources of Galactic cosmic rays up to the knee of the cosmic-ray spectrum at a few PeV. Imaging Atmospheric Cherenkov Telescopes have revealed young SNRs as very-high-energy (VHE, >100 GeV) gamma-ray sources, but for only a few SNRs the hadronic cosmic-ray origin of their gamma-ray emission is indisputably established. In all these cases, the gamma-ray spectra exhibit a spectral cutoff at energies much below 100 TeV and thus do not reach the PeVatron regime.
Aims. The aim of this work was to achieve a firm detection for the oxygen-rich SNR LMC N132D in the VHE gamma-ray domain with an extended set of data, and to clarify the spectral characteristics and the localization of the gamma-ray emission from this exceptionally powerful gamma-ray-emitting SNR.
Methods. We analyzed 252 h of High Energy Stereoscopic System (H.E.S.S.) observations towards SNR N132D that were accumulated between December 2004 and March 2016 during a deep survey of the Large Magellanic Cloud, adding 104 h of observations to the previously published data set to ensure a > 5σ detection. To broaden the gamma-ray spectral coverage required for modeling the spectral energy distribution, an analysis of Fermi-LAT Pass 8 data was also included.
Results. We unambiguously detect N132D at VHE with a significance of 5.7σ. We report the results of a detailed analysis of its spectrum and localization based on the extended H.E.S.S. data set. The joint analysis of the extended H.E.S.S and Fermi-LAT data results in a spectral energy distribution in the energy range from 1.7 GeV to 14.8 TeV, which suggests a high luminosity of N132D at GeV and TeV energies. We set a lower limit on a gamma-ray cutoff energy of 8 TeV with a confidence level of 95%. The new gamma-ray spectrum as well as multiwavelength observations of N132D when compared to physical models suggests a hadronic origin of the VHE gamma-ray emission.
Conclusions. SNR N132D is a VHE gamma-ray source that shows a spectrum extending to the VHE domain without a spectral cutoff at a few TeV, unlike the younger oxygen-rich SNR Cassiopeia A. The gamma-ray emission is best explained by a dominant hadronic component formed by diffusive shock acceleration. The gamma-ray properties of N132D may be affected by an interaction with a nearby molecular cloud that partially lies inside the 95% confidence region of the source position.
Key words: gamma rays: general / cosmic rays / ISM: supernova remnants
© ESO 2021
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