Very high energy gamma-ray radiation from the stellar mass black hole binary Cygnus X-1



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Antoranz Canales, Pedro and Barrio Uña, Juan Abel and Contreras González, José Luis and Fonseca González, Mª Victoria and López Moya, Marcos and Miranda Pantoja, José Miguel and Nieto, Daniel (2007) Very high energy gamma-ray radiation from the stellar mass black hole binary Cygnus X-1. Astrophysical journal, 665 (1 (Par). L51-L54. ISSN 0004-637X

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We report on the results from the observations in the very high energy band ( VHE; GeV) of the black E = 100 g hole X- ray binary ( BHXB) Cygnus X- 1. The observations were performed with the MAGIC telescope, for a total of 40 hr during 26 nights, spanning the period between 2006 June and November. Searches for steady gamma - ray signals yielded no positive result, and upper limits to the integral flux ranging between 1% and 2% of the Crab Nebula flux, depending on the energy, have been established. We also analyzed each observation night independently, obtaining evidence of gamma- ray signals at the 4.0 j significance level ( 3.2 j after trial correction) for 154 minutes of effective on- time ( EOT) on September 24 between 20: 58 and 23: 41 UTC, coinciding with an X- ray flare seen by RXTE, Swift, and INTEGRAL. A search for faster- varying signals within a night resulted in an excess with a significance of 4.9 j ( 4.1 j after trial correction) for 79 minutes EOT between 22: 17 and 23: 41 UTC. The measured excess is compatible with a pointlike source at the position of Cygnus X- 1 and excludes the nearby radio nebula powered by its relativistic jet. The differential energy spectrum is well fitted by an unbroken power law described as dN/(dA dt dE) = ( 2.3 +/- 0.6)* 10 ( E/1TeV). This is the first experimental evidence of VHE emission from a stellar mass black hole and therefore from a confirmed accreting X- ray binary.

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© The American Astronomical Society. We thank the IAC for the excellent working conditions at the Observatory del Roque los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, and the Spanish CICYT is gratefully acknowledged. This work was also supported by ETH research grant TH 34/04 3 and the Polish MNiI grant 1P03D01028.

Uncontrolled Keywords:Discovery, JET, Variability, Spectrum, System.
Subjects:Sciences > Physics > Electronics
Sciences > Physics > Electricity
Sciences > Physics > Nuclear physics
ID Code:23791
Deposited On:03 Dec 2013 13:05
Last Modified:10 Dec 2018 14:58

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