Fermi-LAT detection of increased gamma-ray activity from the FSRQ PKS 1004-217

ATel #11378; Michael Kreter (University of Wuerzburg) on behalf of the Fermi LAT Collaboration
on 6 Mar 2018; 01:45 UT
Credential Certification: David J. Thompson (David.J.Thompson@nasa.gov)

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The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed an increasing gamma-ray flux from a source positionally consistent with the flat spectrum radio quasar (FSRQ) PKS 1004-217 (3FGL J1006.7-2159) with coordinates RA: 10h06m46.4136s, DEC: -21d59m20.410s, J2000 (Beasley et al. 2002, ApJS, 141, 13) and redshift z=0.331 (Hewitt & Burbidge 1989, ApJS, 69, 1).

Preliminary analysis indicates that on 4 March 2018, this source was in a high-flux state with a daily averaged gamma-ray flux (E>100MeV) of (0.84+/-0.08) X 10^-6 photons cm^-2 s^-1 (statistical uncertainties only). This value is about a factor of 19 greater than the average flux reported in the third Fermi LAT catalog (3FGL; Acero et al. 2015, ApJS, 218, 23) and about twice as large as our last reported flare in ATel #10952. The corresponding photon spectral index of 2.33+/-0.07 is in the typical range for a Fermi blazar. On 4 March 2018, between 00:00:00 / 06:00:00 UTC, this source underwent a flare with a six-hour averaged gamma-ray flux (E>100MeV) of (1.2+/-0.3) X 10^-6 photons cm^-2 s^-1 (statistical uncertainties only) and a spectral index of 1.94+/-0.18. Within this time, the six-hour averaged gamma-ray flux was about a factor of 33 greater than the average flux reported in the 3FGL.

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. This source is being added to 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/). In consideration of the ongoing activity of this source we strongly encourage multiwavelength observations. For this source the Fermi LAT contact person is Janeth Valverde (valverde@llr.in2p3.fr).

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.