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Fermi LAT Detection of a Rapid, Powerful Gamma-ray Flare of the FSRQ CTA 102

ATel #8478; Bryce Carpenter (CUA/NASA/GSFC) and Roopesh Ojha (NASA/GSFC/UMBC) on behalf of the Fermi Large Area Telescope Collaboration
on 30 Dec 2015; 19:13 UT
Credential Certification: Roopesh Ojha (Roopesh.Ojha@gmail.com)

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

Referred to by ATel #: 8598, 9869, 9924, 10292

The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope has observed increasing gamma-ray flux from a source positionally consistent with the flat spectrum radio quasar CTA 102 (also known as 3FGL J2232.5+1143, Acero et al. 2015, ApJS, 218, 23) with radio coordinates R.A.: 338.1517038 deg, Dec: 11.7308067 deg (J2000, Johnston et al. 1995, AJ, 110, 880) at redshift z=1.037 (Schmidt 1965, ApJ, 141, 1295).

Preliminary analysis indicates that CTA 102 has been in a flaring state since mid-December and it registered a dramatic increase in flux on 2015 December 28 reaching an averaged daily gamma-ray flux (E>100MeV) of (6.3 +/- 0.4) x 10^-6 photons cm^-2 s^-1 (statistical uncertainty only), about 40 times greater than the average flux reported in the third Fermi-LAT catalog. Its spectral index of 2.1+/-0.1 is harder than its 3FGL value of 2.34+/-0.03. Previous gamma-ray flares have been reported for this source in May 2011 (ATel#3320), Sep 2012 (ATel#4409), and Oct 2014 (ATel#6631).

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. Since CTA 102 is one of the "LAT Monitored Sources", a preliminary, uncalibrated estimation of the daily gamma-ray flux observed by Fermi LAT is publicly available at: http://fermi.gsfc.nasa.gov/FTP/glast/data/lat/catalogs/asp/current/lightcurves/CTA102_86400.png In consideration of the ongoing activity of this source we encourage multiwavelength observations. For this source the Fermi LAT contact person is S. Cutini (sara.cutini@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.