Discovery of the hard spectrum VHE gamma-ray source HESS J1641-463
Abstract
This letter reports the discovery of a remarkably hard spectrum source, HESS J1641-463, by the High Energy Stereoscopic System (H.E.S.S.) in the very-high energy (VHE) domain. HESS J1641-463 remained unnoticed by the usual analysis techniques due to confusion with the bright nearby source HESS J1640-465. It emerged at a significance level of 8.5 standard deviations after restricting the analysis to events with energies above 4 TeV. It shows a moderate flux level of F(E > 1 TeV) = (3.64 +/- 0.44_stat +/- 0.73_sys) x 10^-13 cm^-2s-1, corresponding to 1.8% of the Crab Nebula flux above the same energy, and a hard spectrum with a photon index of Gamma = 2.07 +/- 0.11_stat +/- 0.20_sys. It is a point-like source, although an extension up to Gaussian width of sigma = 3 arcmin cannot be discounted due to uncertainties in the H.E.S.S. PSF. The VHE gamma-ray flux of HESS J1641-463 is found to be constant over the observed period when checking time binnings from year-by-year to the 28 min exposures timescales. HESS J1641-463 is positionally coincident with the radio supernova remnant SNR G338.5+0.1. No X-ray candidate stands out as a clear association, however Chandra and XMM-Newton data reveal some potential weak counterparts. Various VHE gamma-ray production scenarios are discussed. If the emission from HESS J1641-463 is produced by cosmic ray protons colliding with the ambient gas, then their spectrum must extend close to 1 PeV. This object may represent a source population contributing significantly to the galactic cosmic ray flux around the knee.
Keywords
Cite
@article{arxiv.1408.5280,
title = {Discovery of the hard spectrum VHE gamma-ray source HESS J1641-463},
author = {H. E. S. S. Collaboration and : and A. Abramowski and F. Aharonian and F. Ait Benkhali and A. G. Akhperjanian and E. O. Angüner and M. Backes and S. Balenderan and A. Balzer and A. Barnacka and Y. Becherini and J. Becker Tjus and D. Berge and S. Bernhard and K. Bernlöhr and E. Birsin and J. Biteau and M. Böttcher and C. Boisson and J. Bolmont and P. Bordas and J. Bregeon and F. Brun and P. Brun and M. Bryan and T. Bulik and S. Carrigan and S. Casanova and P. M. Chadwick and N. Chakraborty and R. Chalme-Calvet and R. C. G. Chaves and M. Chrétien and S. Colafrancesco and G. Cologna and J. Conrad and C. Couturier and Y. Cui and M. Dalton and I. D. Davids and B. Degrange and C. Deil and P. deWilt and A. Djannati-Ataï and W. Domainko and A. Donath and L. O'C. Drury and G. Dubus and K. Dutson and J. Dyks and M. Dyrda and T. Edwards and K. Egberts and P. Eger and P. Espigat and C. Farnier and S. Fegan and F. Feinstein and M. V. Fernandes and D. Fernandez and A. Fiasson and G. Fontaine and A. Förster and M. Füßling and S. Gabici and M. Gajdus and Y. A. Gallant and T. Garrigoux and G. Giavitto and B. Giebels and J. F. Glicenstein and D. Gottschall and M. -H. Grondin and M. Grudzińska and D. Hadasch and S. Häffner and J. Hahn and J. Harris and G. Heinzelmann and G. Henri and G. Hermann and O. Hervet and A. Hillert and J. A. Hinton and W. Hofmann and P. Hofverberg and M. Holler and D. Horns and A. Ivascenko and A. Jacholkowska and C. Jahn and M. Jamrozy and M. Janiak and F. Jankowsky and I. Jung-Richardt and M. A. Kastendieck and K. Katarzyński and U. Katz and S. Kaufmann and B. Khélifi and M. Kieffer and S. Klepser and D. Klochkov and W. Kluźniak and D. Kolitzus and Nu. Komin and K. Kosack and S. Krakau and F. Krayzel and P. P. Krüger and H. Laffon and G. Lamanna and J. Lau and J. Lefaucheur and V. Lefranc and A. Lemière and M. Lemoine-Goumard and J. -P. Lenain and T. Lohse and A. Lopatin and C. -C. Lu and V. Marandon and A. Marcowith and R. Marx and G. Maurin and N. Maxted and M. Mayer and T. J. L. McComb and J. Méhault and P. J. Meintjes and U. Menzler and M. Meyer and A. M. W. Mitchell and R. Moderski and M. Mohamed and K. Morå and E. Moulin and T. Murach and M. de Naurois and J. Niemiec and S. J. Nolan and L. Oakes and H. Odaka and S. Ohm and B. Opitz and M. Ostrowski and I. Oya and M. Panter and R. D. Parsons and M. Paz Arribas and N. W. Pekeur and G. Pelletier and P. -O. Petrucci and B. Peyaud and S. Pita and H. Poon and G. Pühlhofer and M. Punch and A. Quirrenbach and S. Raab and I. Reichardt and A. Reimer and O. Reimer and M. Renaud and R. de los Reyes and F. Rieger and C. Romoli and S. Rosier-Lees and G. Rowell and B. Rudak and C. B. Rulten and V. Sahakian and D. Salek and D. A. Sanchez and A. Santangelo and R. Schlickeiser and F. Schüssler and A. Schulz and U. Schwanke and S. Schwarzburg and S. Schwemmer and H. Sol and F. Spanier and G. Spengler and F. Spies and Ł. Stawarz and R. Steenkamp and C. Stegmann and F. Stinzing and K. Stycz and I. Sushch and J. -P. Tavernet and T. Tavernier and A. M. Taylor and R. Terrier and M. Tluczykont and C. Trichard and K. Valerius and C. van Eldik and B. van Soelen and G. Vasileiadis and J. Veh and C. Venter and A. Viana and P. Vincent and J. Vink and H. J. Völk and F. Volpe and M. Vorster and T. Vuillaume and S. J. Wagner and P. Wagner and R. M. Wagner and M. Ward and M. Weidinger and Q. Weitzel and R. White and A. Wierzcholska and P. Willmann and A. Wörnlein and D. Wouters and R. Yang and V. Zabalza and D. Zaborov and M. Zacharias and A. A. Zdziarski and A. Zech and H. -S. Zechlin and Y. Fukui and H. Sano and T. Fukuda and S. Yoshiike},
journal= {arXiv preprint arXiv:1408.5280},
year = {2014}
}
Comments
24 pages, 4 figures. Published version