Discovery of variable VHE gamma-ray emission from the binary system 1FGL J1018.6-5856
Creators: name: Collaboration, H. E. S. S.
name: :
name: Abramowski, A.
name: Aharonian, F.
name: Benkhali, F. Ait
name: Akhperjanian, A. G.
name: Angüner, E. O.
name: Backes, M.
name: Balzer, A.
name: Becherini, Y.
name: Tjus, J. Becker
name: Berge, D.
name: Bernhard, S.
name: Bernlöhr, K.
name: Birsin, E.
name: Blackwell, R.
name: Böttcher, M.
name: Boisson, C.
name: Bolmont, J.
name: Bordas, P.
name: Bregeon, J.
name: Brun, F.
name: Brun, P.
name: Bryan, M.
name: Bulik, T.
name: Carr, J.
name: Casanova, S.
name: Chakraborty, N.
name: Chalme-Calvet, R.
name: Chaves, R. C. G.
name: Chen, A.
name: Chrétien, M.
name: Colafrancesco, S.
name: Cologna, G.
name: Conrad, J.
name: Couturier, C.
name: Cui, Y.
name: Davids, I. D.
name: Degrange, B.
name: Deil, C.
name: deWilt, P.
name: Djannati-Ataï, A.
name: Domainko, W.
name: Donath, A.
name: Drury, L. O'C.
name: Dubus, G.
name: Dutson, K.
name: Dyks, J.
name: Dyrda, M.
name: Edwards, T.
name: Egberts, K.
name: Eger, P.
name: Ernenwein, J. -P.
name: Espigat, P.
name: Farnier, C.
name: Fegan, S.
name: Feinstein, F.
name: Fernandes, M. V.
name: Fernandez, D.
name: Fiasson, A.
name: Fontaine, G.
name: Förster, A.
name: Füßling, M.
name: Gabici, S.
name: Gajdus, M.
name: Gallant, Y. A.
name: Garrigoux, T.
name: Giavitto, G.
name: Giebels, B.
name: Glicenstein, J. F.
name: Gottschall, D.
name: Goyal, A.
name: Grondin, M. -H.
name: Grudzińska, M.
name: Hadasch, D.
name: Häffner, S.
name: Hahn, J.
name: Hawkes, J.
name: Heinzelmann, G.
name: Henri, G.
name: Hermann, G.
name: Hervet, O.
name: Hillert, A.
name: Hinton, J. A.
name: Hofmann, W.
name: Hofverberg, P.
name: Hoischen, C.
name: Holler, M.
name: Horns, D.
name: Ivascenko, A.
name: Jacholkowska, A.
name: Jahn, C.
name: Jamrozy, M.
name: Janiak, M.
name: Jankowsky, F.
name: Jung-Richardt, I.
name: Kastendieck, M. A.
name: Katarzyński, K.
name: Katz, U.
name: Kerszberg, D.
name: Khélifi, B.
name: Kieffer, M.
name: Klepser, S.
name: Klochkov, D.
name: Kluźniak, W.
name: Kolitzus, D.
name: Komin, Nu.
name: Kosack, K.
name: Krakau, S.
name: Krayzel, F.
name: Krüger, P. P.
name: Laffon, H.
name: Lamanna, G.
name: Lau, J.
name: Lefaucheur, J.
name: Lefranc, V.
name: Lemière, A.
name: Lemoine-Goumard, M.
name: Lenain, J. -P.
name: Lohse, T.
name: Lopatin, A.
name: Lu, C. -C.
name: Lui, R.
name: Marandon, V.
name: Marcowith, A.
name: Mariaud, C.
name: Marx, R.
name: Maurin, G.
name: Maxted, N.
name: Mayer, M.
name: Meintjes, P. J.
name: Menzler, U.
name: Meyer, M.
name: Mitchell, A. M. W.
name: Moderski, R.
name: Mohamed, M.
name: Morå, K.
name: Moulin, E.
name: Murach, T.
name: de Naurois, M.
name: Niemiec, J.
name: Oakes, L.
name: Odaka, H.
name: Öttl, S.
name: Ohm, S.
name: Wilhelmi, E. de Oña
name: Opitz, B.
name: Ostrowski, M.
name: Oya, I.
name: Panter, M.
name: Parsons, R. D.
name: Arribas, M. Paz
name: Pekeur, N. W.
name: Pelletier, G.
name: Petrucci, P. -O.
name: Peyaud, B.
name: Pita, S.
name: Poon, H.
name: Prokoph, H.
name: Pühlhofer, G.
name: Punch, M.
name: Quirrenbach, A.
name: Raab, S.
name: Reichardt, I.
name: Reimer, A.
name: Reimer, O.
name: Renaud, M.
name: Reyes, R. de los
name: Rieger, F.
name: Romoli, C.
name: Rosier-Lees, S.
name: Rowell, G.
name: Rudak, B.
name: Rulten, C. B.
name: Sahakian, V.
name: Salek, D.
name: Sanchez, D. A.
name: Santangelo, A.
name: Sasaki, M.
name: Schlickeiser, R.
name: Schüssler, F.
name: Schulz, A.
name: Schwanke, U.
name: Schwemmer, S.
name: Seyffert, A. S.
name: Simoni, R.
name: Sol, H.
name: Spanier, F.
name: Spengler, G.
name: Spies, F.
name: Stawarz, Ł.
name: Steenkamp, R.
name: Stegmann, C.
name: Stinzing, F.
name: Stycz, K.
name: Sushch, I.
name: Tavernet, J. -P.
name: Tavernier, T.
name: Taylor, A. M.
name: Terrier, R.
name: Tluczykont, M.
name: Trichard, C.
name: Valerius, K.
name: van der Walt, J.
name: van Eldik, C.
name: van Soelen, B.
name: Vasileiadis, G.
name: Veh, J.
name: Venter, C.
name: Viana, A.
name: Vincent, P.
name: Vink, J.
name: Voisin, F.
name: Völk, H. J.
name: Vuillaume, T.
name: Wagner, S. J.
name: Wagner, P.
name: Wagner, R. M.
name: Weidinger, M.
name: Weitzel, Q.
name: White, R.
name: Wierzcholska, A.
name: Willmann, P.
name: Wörnlein, A.
name: Wouters, D.
name: Yang, R.
name: Zabalza, V.
name: Zaborov, D.
name: Zacharias, M.
name: Zdziarski, A. A.
name: Zech, A.
name: Zefi, F.
name: Żywucka, N.
Publisher: name: arXiv
Year: 2015
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Re-observations with the H.E.S.S. telescope array of the very-high-energy (VHE) source HESS J1018-589 A coincident with the Fermi-LAT $γ$-ray binary 1FGL J1018.6-5856 have resulted in a source detection significance of more than 9$σ$, and the detection of variability ($χ^2$/$ν$ of 238.3/155) in the emitted $γ$-ray flux. This variability confirms the association of HESS J1018-589 A with the high-energy $γ$-ray binary detected by Fermi-LAT, and also confirms the point-like source as a new very-high-energy binary system. The spectrum of HESS J1018-589 A is best fit with a power-law function with photon index $Γ= 2.20 \pm 0.14_{\rm stat} \pm 0.2_{\rm sys}$. Emission is detected up to ~20 TeV. The mean differential flux level is $(2.9 \pm 0.4)\times10^{-13}$ TeV$^{-1}$ cm$^{-2}$ s$^{-1}$ at 1 TeV, equivalent to ~1% of the flux from the Crab Nebula at the same energy. Variability is clearly detected in the night-by-night lightcurve. When folded on the orbital period of 16.58 days, the rebinned lightcurve peaks in phase with the observed X-ray and high-energy phaseograms. The fit of the H.E.S.S. phaseogram to a constant flux provides evidence of periodicity at the level of 3$σ$. The shape of the VHE phaseogram and measured spectrum suggest a low inclination, low eccentricity system with a modest impact from VHE $γ$-ray absorption due to pair production ($τ$ &lt; 1 at 300 GeV).
description: Accepted for publication in A&amp;A