HESS observations of the Carina nebula and its enigmatic colliding wind binary Eta Carinae
Klochkov, D.; Santangelo, A.; Quirrenbach, A.; Ripken, J.; Carrigan, S.; Conrad, J.; Grondin, M. -H.; Reimer, A.; Reimer, O.; Venter, C.; Schlickeiser, R.; Petrucci, P. -O.; Giebels, B.; Stawarz, Ł.; Fontaine, G.; Daniel, M. K.; Hauser, M.; Boisson, C.; Aharonian, F.; Akhperjanian, A. G.; Bernlöhr, K.; Chadwick, P. M.; Degrange, B.; Djannati-Ataï, A.; Dubus, G.; Espigat, P.; Feinstein, F.; Gallant, Y. A.; Glicenstein, J. F.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hofmann, W.; Horns, D.; Khélifi, B.; Komin, Nu.; Lohse, T.; Marcowith, A.; McComb, T. J. L.; de Naurois, M.; Nolan, S. J.; Panter, M.; Pelletier, G.; Pita, S.; Pühlhofer, G.; Punch, M.; Raue, M.; Rob, L.; Rowell, G.; Sahakian, V.; Schwanke, U.; Sol, H.; Steenkamp, R.; Stegmann, C.; Tavernet, J. -P.; Terrier, R.; Tluczykont, M.; Vasileiadis, G.; Vincent, P.; Völk, H. J.; Wagner, S. J.; Ward, M.; Heinz, S.; Kossakowski, R.; Lamanna, G.; Acero, F.; Chaves, R. C. G.; Mayer, M.; Schulz, A.; Renaud, M.; Montmerle, T.; Cerruti, M.; de Oña Wilhelmi, E.; Anton, G.; Becherini, Y.; Bochow, A.; Bolmont, J.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Büsching, I.; Charbonnier, A.; Cheesebrough, A.; Dalton, M.; Davids, I. D.; Deil, C.; Dickinson, H. J.; Domainko, W.; Dyks, J.; Dyrda, M.; Egberts, K.; Eger, P.; Fallon, L.; Fegan, S.; Fiasson, A.; Förster, A.; Füßling, M.; Gérard, L.; Glück, B.; Göring, D.; Hofverberg, P.; Jacholkowska, A.; Jahn, C.; Jung, I.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Kluźniak, W.; Kneiske, T.; Kosack, K.; Lenain, J. -P.; Marandon, V.; Masbou, J.; Medina, M. C.; Méhault, J.; Moderski, R.; Moulin, E.; Naumann-Godo, M.; Nedbal, D.; Nekrassov, D.; Nicholas, B.; Niemiec, J.; Ohm, S.; Ostrowski, M.; Paz Arribas, M.; Rieger, F.; Rosier-Lees, S.; Rudak, B.; Rulten, C. B.; Schwarzburg, S.; Schwemmer, S.; Sushch, I.; Skilton, J. L.; Stinzing, F.; Szostek, A.; van Eldik, C.; Volpe, F.; Vorobiov, S.; Zdziarski, A. A.; Zech, A.; Abramowski, A.; Balzer, A.; Barnacka, A.; Birsin, E.; Biteau, J.; Bordas, P.; Casanova, S.; Cologna, G.; Dutson, K.; Fernandes, M. V.; Garrigoux, T.; Häffner, S.; Hahn, J.; Harris, J.; Hillert, A.; Holler, M.; Jamrozy, M.; Kastendieck, M. A.; Krayzel, F.; Laffon, H.; Lopatin, A.; Lu, C. -C.; Maurin, G.; Maxted, N.; Mohamed, M.; Opitz, B.; Oya, I.; Pekeur, N. W.; Peyaud, B.; de los Reyes, R.; Sanchez, D. A.; Spengler, G.; Stycz, K.; Valerius, K.; Viana, A.; Vorster, M.; White, R.; Wierzcholska, A.; Zacharias, M.; Zechlin, H. -S.; Becker, J.; Gast, H.; Hague, J. D.; Hampf, D.; Lennarz, D.; Naumann, C. L.; Nguyen, N.; Zajczyk, A.; Drury, L. O'C.; HESS Collaboration; Perez, J.; Sheidaei, F.
Germany, France, Ireland, Armenia, Poland, South Africa, United Kingdom, Sweden, Namibia, Austria, Czech Republic, Australia
Abstract
The massive binary system Eta Carinae and the surrounding H II complex, the Carina nebula, are potential particle acceleration sites from which very high energy (VHE; E≥ 100 GeV) γ-ray emission could be expected. This paper presents data collected during VHE γ-ray observations with the HESS telescope array from 2004 to 2010, which cover a full orbit of Eta Carinae. In the 33.1-h data set no hint of significant γ-ray emission from Eta Carinae has been found and an upper limit on the γ-ray flux of ? (99 per cent confidence level) is derived above the energy threshold of 470 GeV. Together with the detection of high energy (HE; 0.1 ≤E≤ 100 GeV) γ-ray emission by the Fermi Large Area Telescope up to 100 GeV, and assuming a continuation of the average HE spectral index into the VHE domain, these results imply a cut-off in the γ-ray spectrum between the HE and VHE γ-ray range. This could be caused either by a cut-off in the accelerated particle distribution or by severe γ-γ absorption losses in the wind collision region. Furthermore, the search for extended γ-ray emission from the Carina nebula resulted in an upper limit on the γ-ray flux of ? (99 per cent confidence level). The derived upper limit of ∼23 on the cosmic ray enhancement factor is compared with results found for the old-age mixed-morphology supernova remnant W28.