Variable very high energy gamma-ray emission from Markarian 501



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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) Variable very high energy gamma-ray emission from Markarian 501. Astrophysical journal, 669 (2 (Par). pp. 862-883. ISSN 0004-637X

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The blazar Mrk 501 was observed at energies above 0.10 TeV with the MAGIC Telescope from 2005 May through July. The high sensitivity of the instrument enabled the determination of the flux and spectrum of the source on a night-by-night basis. Throughout our observational campaign, the flux from Mrk 501 was found to vary by an order of magnitude. Intranight flux variability with flux-doubling times down to 2 minutes was observed during the two most active nights, namely, June 30 and July 9. These are the fastest flux variations ever observed in Mrk 501. The similar to 20 minute long flare of July 9 showed an indication of a 4 +/- 1 minute time delay between the peaks of F(< 0.25 TeV) and F(> 1.2 TeV), which may indicate a progressive acceleration of electrons in the emitting plasma blob. The flux variability was quantified for several energy ranges and found to increase with the energy of the gamma-ray photons. The spectra hardened significantly with increasing flux, and during the two most active nights, a spectral peak was clearly detected at 0.43 +/- 0.06 and 0.25 +/- 0.07 TeV, respectively, for June 30 and July 9. There is no evidence of such a spectral feature for the other nights at energies down to 0.10 TeV, thus suggesting that the spectral peak is correlated with the source luminosity. These observed characteristics could be accommodated in a synchrotron self-Compton framework in which the increase in gamma-ray flux is produced by a freshly injected ( high energy) electron population.

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© The American Astronomical Society. We would like to thank the IAC for the excellent working conditions
on the La Palma Observatory Roque de los Muchachos.
We are grateful to the RXTE ASMteamfor their quick-look results.
The support of the German BMBF andMPG, the Italian INFN,
and the Spanish CICYT is gratefully acknowledged. This work
was also supported by ETH research grant TH-34/04-3 and by
Polish grant MNiI 1P03D01028. In addition, the authors want
to thank Deirdre Horan, Martin Tluczykont, and Fre´de´ric Piron
for providing Mrk 501 data from WHIPPLE, HEGRA CT1,
and HEGRA CT System and CAT, respectively, and for useful

Uncontrolled Keywords:Active Galactic Nuclei, BL-LAC Objects, Cherenkov Telescope System, Log-Parabolic Spectra, 23 Day Periodicity, Black-Hole Models, X-Ray, MKN 501, Multiwavelength Observations, Particle-Acceleration.
Subjects:Sciences > Physics > Electronics
Sciences > Physics > Electricity
Sciences > Physics > Nuclear physics
ID Code:23692
Deposited On:26 Nov 2013 14:42
Last Modified:10 Dec 2018 14:58

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