H.E.S.S. reveals a lack of TeV emission from the supernova remnant Puppis A

Collaboration, H.E.S.S.; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A.G.; Angüner, E.; Backes, M.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Birsin, E.; Biteau, J.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bulik, T.; Carrigan, S.; Casanova, S.; Chadwick, P.M.; Chakraborty, M.; Chalme-Calvet, R.; Chaves, R.C.G.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Cui, Y.; Davids, I.D.; Degrange, B.; Deil, C.; deWilt, P.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L.O'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M.V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y.A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J.F.; Gottschall, D.; Grondin, M.-H.; Grudzińska,...

Abstract

Context. Puppis A is an interesting ~4 kyr-old supernova remnant (SNR) that shows strong evidence of interaction between the forward shock and a molecular cloud. It has been studied in detail from radio frequencies to high-energy (HE, 0.1−100 GeV) γ-rays. An analysis of the Fermi-LAT data has shown extended HE γ-ray emission with a 0.2−100 GeV spectrum exhibiting no significant deviation from a power law, unlike most of the GeV-emitting SNRs known to be interacting with molecular clouds. This makes it a promising target for imaging atmospheric Cherenkov telescopes (IACTs) to probe the γ-ray emission above 100 GeV. Aims. Very-high-energy (VHE, E ≥ 0.1 TeV) γ-ray emission from Puppis A has been, for the first time, searched for with the High Energy Stereoscopic System (H.E.S.S.). Methods. Stereoscopic imaging of Cherenkov radiation from extensive air showers is used to reconstruct the direction and energy of the incident γ-rays in order to produce sky images and source spectra. The profile likelihood method is applied to find constraints on the existence of a potential break or cutoff in the photon spectrum. Results. The analysis of the H.E.S.S. data does not reveal any significant emission towards Puppis A. The derived upper limits on the differential photon flux imply that its broadband γ-ray spectrum must exhibit a spectral break or cutoff. By combining Fermi-LAT and H.E.S.S. measurements, the 99% confidence-level upper limits on such a cutoff are found to be 450 and 280 GeV, assuming a power law with a simple exponential and a sub-exponential cutoff, respectively. It is concluded that none of the standard limitations (age, size, radiative losses) on the particle acceleration mechanism, assumed to be continuing at present, can explain the lack of VHE signal. The scenario in which particle acceleration has ceased some time ago is considered as an alternative explanation. The HE/VHE spectrum of Puppis A could then exhibit a break of non-radiative origin (as observed in several other interacting SNRs, albeit at somewhat higher energies), owing to the interaction with dense and neutral material, in particular towards the NE region.

Citation

Collaboration, H., Abramowski, A., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., …Zechlin, H. (2015). H.E.S.S. reveals a lack of TeV emission from the supernova remnant Puppis A. Astronomy & Astrophysics, 575, https://doi.org/10.1051/0004-6361/201424805

• Journal Article Type: Article
• Acceptance Date: Dec 20, 2014
• Publication Date: Mar 1, 2015
• Deposit Date: Apr 15, 2015
• Publicly Available Date: Apr 22, 2015
• Journal: Astronomy and astrophysics.
• Print ISSN: 0004-6361
• Electronic ISSN: 1432-0746
• Publisher: EDP Sciences
• Peer Reviewed: Peer Reviewed
• Volume: 575
• DOI: https://doi.org/10.1051/0004-6361/201424805
• Keywords: Gamma rays: ISM, ISM: individual objects: Puppis A, Radiation mechanisms: non-thermal, Cosmic rays, Acceleration of particles.
• Public URL: https://durham-repository.worktribe.com/output/1409356
• Related Public URLs: http://adsabs.harvard.edu/abs/2015A%26A...575A..81H