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Fermi-LAT detection of a GeV gamma-ray flare from blazar PKS B1908-201

ATel #6575; Stefano Ciprini (ASI Science Data Center and INAF Observatory of Rome, Italy), on behalf of the Fermi Large Area Telescope Collaboration.
on 13 Oct 2014; 20:19 UT
Credential Certification: Stefano Ciprini (stefano.ciprini@asdc.asi.it)

Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar, Quasar

The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed increasing gamma-ray flux from a source positionally consistent with the flat spectrum radio quasar PKS B1908-201 (also known as PKS 1908-201, TXS 1908-201, OV -213), with radio coordinates R.A.: 287.79022 deg, Dec: -20.11531 deg (J2000.0, Johnston et al. 1995, AJ, 110, 880). This FSRQ has a redshift of 1.119 (Halpern, Eracleous & Mattox 2003, AJ, 125, 572).

Preliminary analysis indicates that PKS B1908-201 on October 12, 2014, was in a high state with a daily averaged gamma-ray flux (E>100MeV) of (1.3+/-0.3)X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only), about 10 times greater than the average flux reported in the second Fermi-LAT catalog (2FGL J1911.1-2005 , Nolan et al. 2012, ApJS, 199, 31). PKS B1908-201 is a known EGRET blazar (3EG J1911-2000) and is monitored by VLBA (MOJAVE program).

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. The source will be inserted in the "LAT Monitored Source", consequently a quick look estimation of the daily gamma-ray flux observed by Fermi LAT will be publicly available (fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/). In consideration of the ongoing activity of this source, we encourage multiwavelength observations. For this source the Fermi LAT contact person is David J. Thompson (David.J.Thompson@nasa.gov).

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.