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Fermi-LAT detection of renewed gamma-ray activity from the FSRQ PKS 0336-01

ATel #11227; R. Angioni (MPIfR-Bonn) on behalf of the Fermi-LAT Collaboration
on 25 Jan 2018; 15:35 UT
Credential Certification: Sara Buson (sara.buson@gmail.com)

Subjects: Gamma Ray, Request for Observations, AGN, Blazar

The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope, has observed enhanced gamma-ray emission from a source positionally consistent with the flat-spectrum radio quasar PKS 0336-01 (CTA 26), also known as 3FGL J0339.5-0146 (Acero et al. 2015, ApJS, 218, 23), with coordinates R.A. = 54.8789071 deg, Decl. = -1.7766119 deg (J2000; Johnston et al. 1995 AJ, 110, 880), and a redshift of 0.850 (Wills & Lynds 1978 ApJS, 36, 317).

Preliminary analysis indicates that this source went into a high-flux state starting on 21 January 2018, and continued to brighten over the following days, reaching a peak daily averaged gamma-ray flux (E>100MeV) of (2.2+/-0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only) on 23 January. The latter corresponds to a flux increase of a factor of about 28 relative to the average flux reported in the third Fermi-LAT catalog (3FGL). This is the highest LAT daily flux ever reported for the source, corresponding to about double the flux observed during a previously reported flaring episode in October 2014 (ATel #6568). The corresponding photon spectral index of 1.96+/-0.08 is significantly harder than the 3FGL value of 2.25+/-0.05. Therefore PKS 0336-01 is another example of the "harder-when-brighter" behavior observed in several flaring FSRQs.

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. This source is included in the "LAT Monitored Sources" and consequently a preliminary estimation of the daily gamma-ray flux observed by Fermi-LAT will be publicly available (http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/). We encourage further multifrequency observations of this source. For this source the Fermi-LAT contact persons are Roopesh Ojha (roopesh.ojha@gmail.com) and Stefano Ciprini (stefano.ciprini@asdc.asi.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.