As one of the brightest active blazars in both X-ray and very high energy gamma-ray bands, Mrk 501, is very useful for physics associated with jets from active galactic nuclei. The ARGO-YBJ experiment has monitored Mrk 501 for gamma-ray above 0.3 TeV since 2007 November. The largest flare since 2005 was observed from 2011 October and lasted until about 2012 April. In this paper, a detailed analysis of this event is reported. During the brightest gamma-ray flaring episodes from 2011 October 17 to November 22, an excess of the event rate over 6 sigma is detected by ARGO-YBJ in the direction of Mrk 501, corresponding to an increase of the gamma-ray flux above 1 TeV by a factor of 6.6 +/- 2.2 from its steady emission. In particular, the gamma-ray flux above 8 TeV is detected with a significance better than 4 sigma. Based on time-dependent synchrotron self-Compton (SSC) processes, the broadband energy spectrum is interpreted as the emission from an electron energy distribution parameterized with a single power-law function with an exponential cutoff at its high-energy end. The average spectral energy distribution for the steady emission is well described by this simple one-zone SSC model. However, the detection of gamma-ray above 8 TeV during the flare challenges this model due to the hardness of the spectra. Correlations between X-rays and gamma-ray are also investigated.

LONG-TERM MONITORING OF MRK 501 FOR ITS VERY HIGH ENERGY gamma EMISSION AND A FLARE IN 2011 OCTOBER / Iuppa, Roberto; ARGO YBJ, Collaboration. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - 758:1(2012), pp. 0201-0208. [10.1088/0004-637X/758/1/2]

LONG-TERM MONITORING OF MRK 501 FOR ITS VERY HIGH ENERGY gamma EMISSION AND A FLARE IN 2011 OCTOBER

Iuppa, Roberto;
2012

Abstract

As one of the brightest active blazars in both X-ray and very high energy gamma-ray bands, Mrk 501, is very useful for physics associated with jets from active galactic nuclei. The ARGO-YBJ experiment has monitored Mrk 501 for gamma-ray above 0.3 TeV since 2007 November. The largest flare since 2005 was observed from 2011 October and lasted until about 2012 April. In this paper, a detailed analysis of this event is reported. During the brightest gamma-ray flaring episodes from 2011 October 17 to November 22, an excess of the event rate over 6 sigma is detected by ARGO-YBJ in the direction of Mrk 501, corresponding to an increase of the gamma-ray flux above 1 TeV by a factor of 6.6 +/- 2.2 from its steady emission. In particular, the gamma-ray flux above 8 TeV is detected with a significance better than 4 sigma. Based on time-dependent synchrotron self-Compton (SSC) processes, the broadband energy spectrum is interpreted as the emission from an electron energy distribution parameterized with a single power-law function with an exponential cutoff at its high-energy end. The average spectral energy distribution for the steady emission is well described by this simple one-zone SSC model. However, the detection of gamma-ray above 8 TeV during the flare challenges this model due to the hardness of the spectra. Correlations between X-rays and gamma-ray are also investigated.
1
Iuppa, Roberto; ARGO YBJ, Collaboration
LONG-TERM MONITORING OF MRK 501 FOR ITS VERY HIGH ENERGY gamma EMISSION AND A FLARE IN 2011 OCTOBER / Iuppa, Roberto; ARGO YBJ, Collaboration. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - 758:1(2012), pp. 0201-0208. [10.1088/0004-637X/758/1/2]
File in questo prodotto:
File Dimensione Formato  
Bartoli_2012_ApJ_758_2.pdf

Solo gestori archivio

Tipologia: Versione editoriale (Publisher’s layout)
Licenza: Tutti i diritti riservati (All rights reserved)
Dimensione 564.05 kB
Formato Adobe PDF
564.05 kB Adobe PDF   Visualizza/Apri

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione

Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11572/162424
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 54
  • ???jsp.display-item.citation.isi??? 43
social impact