Fermi-LAT detection of hard spectrum and highest-level gamma-ray outburst from the distant blazar PKS 1502+106
ATel #7801; Stefano Ciprini (ASDC Rome & INFN Perugia, Italy), on behalf of the Fermi Large Area Telescope Collaboration.
on 14 Jul 2015; 21:55 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 two instruments on the Fermi Gamma-ray Space Telescope, has observed flaring gamma rays from a source positionally consistent with the flat spectrum radio quasar PKS 1502+106 (also known as OR 103, S3 1502+10 and 3FGL J1504.4+1029, Acero et al. 2015, ApJS 218, 23), with radio coordinates, (J2000.0), R.A.: 226.10408 deg, Dec: 10.49422 deg (Johnston et al. 1995, AJ, 110, 880). This blazar has a redshift of z=1.8383 (Hewett & Wild 2010, MNRAS, 405, 2302).
Preliminary analysis indicates that on 13 July 2015 the source was in the highest-flux state observed by the LAT since the Fermi launch, with a daily gamma-ray flux (E>100MeV) of (3.4+/-0.3) X 10^-6 photons cm^-2 s^-1, and a 6-hour (12:00-18:00 UT) interval gamma-ray flux of (5.2+/-0.8) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). The corresponding spectral photon index (E>100MeV) of respectively (1.7+/-0.1) and (1.8+/-0.2) are smaller than the average index of 2.075+/-0.014 in the 3FGL catalog.
This is the fourth time that Fermi is announcing increased gamma-ray activity from this blazar (after August 2008, ATel#1650, January 2009, ATel#1905, and the renewed activity reported in June 2015, ATel #7592). Follow-up Fermi-Swift results about the renewed phase of increased activity are recently reported in ATel#7783.
This source is one of the "LAT Monitored Sources" and consequently a preliminary estimation of the daily gamma-ray flux observed by Fermi LAT is publicly available (http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/source/PKS_1502p106).
Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. In consideration of the ongoing activity and hard-state of this source, we encourage multiwavelength observations. For this source the Fermi LAT contact person is S. 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.