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Fermi-LAT Detection of an Unusual Hard Spectrum and Enhanced Gamma-ray Emission from the FSRQ PKS B1035-281

ATel #8740; Bryce Carpenter (CUA/NASA/GSFC) and Roopesh Ojha (NASA/GSFC/UMBC) on behalf of the Fermi Large Area Telescope Collaboration
on 26 Feb 2016; 16:55 UT
Credential Certification: Roopesh Ojha (Roopesh.Ojha@gmail.com)

Subjects: Gamma Ray, >GeV, AGN, Blazar, Quasar

Referred to by ATel #: 8747, 8767, 8773, 8780

The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope has observed increasing gamma-ray flux and an unusually hard spectrum from a source positionally consistent with the flat spectrum radio quasar PKS B1035-281 (also known as 3FGL J1037.5-2821, Acero et al. 2015, ApJS, 218, 23) with radio coordinates R.A.: 159.4269058 deg, Dec: -28.3844750 deg (J2000, Beasley et al. 2002, ApJS, 141, 13) at redshift z=1.066 (Shaw et al. 2012, ApJ, 748, 49).

Preliminary analysis indicates that on 24 February 2016 this source was in a high-flux state, with a daily averaged gamma-ray flux (E>100MeV) of (0.7+/-0.1) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only) corresponding to a flux increase of a factor of about 30 over its four-year average flux (3FGL J1037.5-2821). The corresponding photon spectral index of 1.7+/-0.1 is significantly harder than the 3FGL value 2.5+/-0.1. It is also significantly harder than during previous flares of comparable flux on 6 Dec 2015 and 28 Nov 2015 when the photon spectral index was 2.1+/-0.2 and 2.3+/-0.2, respectively. Thus this flare is a rare example of a 'red turned blue' blazar.

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. In consideration of the ongoing activity of this source we encourage multiwavelength observations. For this source the Fermi LAT contact person is B. Carpenter (carpbr01@gmail.com).

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.