Fermi-LAT detection of renewed GeV gamma-ray activity from the blazar PKS 0514-459

ATel #13705; Stefano Ciprini (ASI Space Science Data Center, Roma, & INFN Roma Tor Vergata, Italy), on behalf of the the Fermi Large Area Telescope Collaboration
on 3 May 2020; 20:56 UT
Credential Certification: Stefano Ciprini (stefano.ciprini@ssdc.asi.it)

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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 0514-459 (also known as RX J0515.7-4556 and 4FGL J0515.6-4556), with radio counterpart position R.A.: 78.938767 deg, Dec.: -45.945369 deg (J2000.0, Costa & Loyola 1996, A&AS, 115, 75) and with redshift z=0.194 (Stickel, Kuehr, & Fried 1993, A&AS, 97, 483).

Preliminary analysis indicates that on 2020 April 30, PKS 0514-459 was in an active state reaching the highest daily averaged gamma-ray flux (E>100 MeV) ever recorded of (1.3+/-0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only), about 65 times greater than its eight-year average flux reported in the fourth Fermi-LAT source catalog (4FGL, Abdollahi et al. 2020, ApJS, 247, 33). The corresponding daily averaged spectral photon index (E>100 MeV) of 2.3+/-0.1 (statistical uncertainty only) is almost consistent with the 4FGL catalog value of 2.51+/-0.06.

This rapid flare of April 30 triggered the automatic GCN/FERMI NOTICE #1588344339. On April 29, the day before the flare peak, the source showed a daily averaged gamma-ray flux (E>100 MeV) of (0.6+/-0.1) X 10^-6 photons cm^-2 s^-1. In the following days of May 1 and May 2, PKS 0514-459 continued to be active and detected with daily averaged gamma-ray flux (E>100 MeV) of (0.5+/-0.1) X 10^-6 and (0.4+/-0.1) X 10^-6 photons cm^-2 s^-1 respectively.

This is the second time that the LAT collaboration has announced enhanced gamma-ray activity from PKS 0514-459, after ATel#8595. The source is in the "LAT Monitored Sources" table (fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/source/PKS_0514-459) at FSSC, and consequently preliminary estimations of the daily and weekly gamma-ray fluxes observed by Fermi LAT are publicly available.

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. In consideration of the ongoing activity of this source, we encourage multiwavelength observations. For this source the Fermi LAT contact person is S. Ciprini (stefano.ciprini@ssdc.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.