Fermi-LAT detection of renewed gamma-ray activity from the blazar PKS 1313-333
ATel #14672; F. D'Ammando (INAF-IRA Bologna), S. Garrappa (DESY-Zeuthen) on behalf of the Fermi Large Area Telescope Collaboration
on 1 Jun 2021; 07:42 UT
Credential Certification: Filippo D'Ammando (dammando@ira.inaf.it)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Black Hole, 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 1313-333, also known as TXS 1313-333, OP -322 (4FGL J1316.1-3338; Abdollahi et al. 2020, ApJS, 247, 33), with radio counterpart position R.A.: 199.033275 deg, Dec.: -33.64977 deg, (J2000.0; Johnston et al. 1995, AJ, 110, 880) and with redshift z = 1.210 (Jauncey et al. 1982, AJ, 87, 763).
Preliminary analysis indicates that on 2021 May 30, PKS 1313-333 was in an active state, reaching a daily averaged gamma-ray flux (E>100 MeV) of (1.4+/-0.3) x10^-6 photons cm^-2 s^-1 (statistical uncertainty only), a factor more than 30 times greater than its ten-year average flux reported in the fourth Fermi-LAT source catalog data release 2 (4FGL-DR2; Ballet et al. 2020, arXiv:2005.11208). The corresponding photon index is 1.87+/-0.12, harder than the 4FGL-DR2 value of 2.33+/-0.03. Flaring gamma-ray activity of PKS 1313-333 has been previously announced by the LAT Collaboration on 2016 January 10 (ATel #8533).
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 is publicly available ( http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/ ). In consideration of the ongoing activity of this source, we encourage multi-wavelength 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.
