A1 Refereed original research article in a scientific journal
Search for very high-energy gamma-ray emission from the microquasar Cygnus X-1 with the MAGIC telescopes
Authors: Ahnen ML, Ansoldi S, Antonelli LA, Arcaro C, Babic A, Banerjee B, Bangale P, de Almeida UB, Barrio JA, Gonzalez JB, Bednarek W, Bernardini E, Berti A, Bhattacharyya W, Biasuzzi B, Biland A, Blanch O, Bonnefoy S, Bonnoli G, Carosi R, Carosi A, Chatterjee A, Colin P, Colombo E, Contreras JL, Cortina J, Covino S, Cumani P, Da Vela P, Dazzi F, De Angelis A, De Lotto B, Wilhelmi ED, Di Pierro F, Doert M, Dominguez A, Prester DD, Dorner D, Doro M, Einecke S, Glawion DE, Elsaesser D, Engelkemeier M, Ramazani VF, Fernandez-Barral A, Fidalgo D, Fonseca MV, Font L, Fruck C, Galindo D, Lopez RJG, Garczarczyk M, Gaug M, Giammaria P, Godinovic N, Gora D, Guberman D, Hadasch D, Hahn A, Hassan T, Hayashida M, Herrera J, Hose J, Hrupec D, Ishio K, Konno Y, Kubo H, Kushida J, Kuvezdic D, Lelas D, Lindfors E, Lombardi S, Longo F, Lopez M, Maggio C, Majumdar P, Makariev M, Maneva G, Manganaro M, Mannheim K, Maraschi L, Mariotti M, Martinez M, Mazin D, Menzel U, Minev M, Mirzoyan R, Moralejo A, Moreno V, Moretti E, Neustroev V, Niedzwiecki A, Rosillo MN, Nilsson K, Ninci D, Nishijima K, Noda K, Nogues L, Paiano S, Palacio J, Paneque D, Paoletti R, Paredes JM, Paredes-Fortuny X, Pedaletti G, Peresano M, Perri L, Persic M, Moroni PGP, Prandini E, Puljak I, Garcia JR, Reichardt I, Rhode W, Ribo M, Rico J, Righi C, Saito T, Satalecka K, Schroeder S, Schweizer T, Sitarek J, Snidaric I, Sobczynska D, Stamerra A, Strzys M, Suric T, Takalo L, Tavecchio F, Temnikov P, Terzic T, Tescaro D, Teshima M, Torres DF, Torres-Alba N, Treves A, Vanzo G, Acosta MV, Vovk I, Ward JE, Will M, Zaric D, Bosch-Ramon V, Pooley GG, Trushkin SA, Zanin R
Publisher: OXFORD UNIV PRESS
Publishing place: Oxford
Publication year: 2017
Journal: Monthly Notices of the Royal Astronomical Society
Journal name in source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Journal acronym: MON NOT R ASTRON SOC
Volume: 472
Issue: 3
First page : 3474
Last page: 3485
Number of pages: 12
ISSN: 0035-8711
eISSN: 1365-2966
DOI: https://doi.org/10.1093/mnras/stx2087
Web address : https://academic.oup.com/mnras/article/472/3/3474/4082239
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/27393766
The microquasar Cygnus X-1 displays the two typical soft and hard X-ray states of a black hole transient. During the latter, Cygnus X-1 shows a one-sided relativistic radio-jet. Recent detection of the system in the high energy (HE; E greater than or similar to 60 MeV) gamma-ray range with FermiLAT associates this emission with the outflow. Former MAGIC observations revealed a hint of flaring activity in the very high-energy (VHE; E greater than or similar to 100 GeV) regime during this X-ray state. We analyse similar to 97 h of Cygnus X-1 data taken with the MAGIC telescopes between July 2007 and October 2014. To shed light on the correlation between hard X-ray and VHE gamma rays as previously suggested, we study each main X-ray state separately. We perform an orbital phase-folded analysis to look for variability in the VHE band. Additionally, to place this variability behaviour in a multiwavelength context, we compare our results with Fermi-LAT, AGILE, Swift-BAT, MAXI, RXTE-ASM, AMI and RATAN-600 data. We do not detect Cygnus X-1 in the VHE regime. We establish upper limits for each X-ray state, assuming a power-law distribution with photon index Gamma = 3.2. For steady emission in the hard and soft X-ray states, we set integral upper limits at 95 per cent confidence level for energies above 200 GeV at 2.6 x 10(-12) photons cm(-2) s(-1) and 1.0 x 10(-11) photons cm(-2) s(-1), respectively. We rule out steady VHE gamma-ray emission above this energy range, at the level of theMAGIC sensitivity, originating in the interaction between the relativistic jet and the surrounding medium, while the emission above this flux level produced inside the binary still remains a valid possibility.
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