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Detection of a strong optical and gamma-ray flare from blazar PKS 1424-41

ATel #4714; F. D'Ammando (Univ. Perugia, INFN), M. Orienti (INAF-IRA Bologna, Univ. Bologna), F. Longo (Univ. Trieste, INFN) on behalf of the Fermi Large Area Telescope Collaboration and F. Jankowsky, S. Schwemmer, S. Wagner (LSW Heidelberg) on behalf of the ATOM team
on 8 Jan 2013; 07:20 UT
Credential Certification: Filippo D'Ammando (filippo.dammando@fisica.unipg.it)

Subjects: Optical, Gamma Ray, >GeV, Request for Observations, AGN, Black Hole, Blazar

Referred to by ATel #: 4717, 4770, 4775, 4819

The Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope has observed an increasing gamma-ray flux from a source positionally coincident with PKS 1424-41 (also known as 2FGL J1428.0-4206, Nolan et al. 2012, ApJS, 199, 31; R.A.= 14h27m56.2975s, Dec.= -42d06m19.437s, J2000, Johnston et al. 1995, AJ, 110, 880), a flat spectrum radio quasar with a redshift of 1.522 (White et al. 1988, ApJ, 327, 561).

Preliminary analysis indicates that at the beginning of 2013 January the source was in a flaring state, reaching on 2013 January 6 a gamma-ray flux (E > 100 MeV) of (2.3 +/- 0.4) x10^-6 photons/cm^2/s (statistical uncertainty only). This flux is about 14 times greater than the average flux reported in the second Fermi LAT catalog (Nolan et al. 2012, ApJS, 199, 31) and brighter than previous flares observed by Fermi-LAT in 2009 June (ATel #2104), 2010 April (ATel #2583), 2011 May (ATel #3329), and 2012 October (ATel #4494).

The Automatic Telescope for Optical Monitoring (ATOM), operated at the HESS site, Farm Goellschau, Namibia, recorded a high optical flux simultaneous with the high state in gamma-rays. On 2013 January 7 02:43 (JD 2456299.613) an R-band magnitude of 14.74 (+/-0.04) mag was reached. This is comparable to the flux levels reached during the previous flares in 2009 June (ATel #2103) and 2010 April (ATel #2613), and brighter than flares in 2011 and 2012.

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. Multiwavelength observations during the ongoing activity of this source are strongly encouraged. The Fermi LAT contact person is F. Longo (francesco.longo@ts.infn.it).

The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.