Fermi-LAT detection of renewed gamma-ray activity from the FSRQ PKS 1424-41
ATel #16406; Chiara Bartolini (University of Trento and INFN Bari), on behalf of the Fermi Large Area Telescope Collaboration
on 15 Jan 2024; 09:33 UT
Credential Certification: Isabella Mereu (mereuisabella@gmail.com)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar, Quasar
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed renewed gamma-ray activity from a source positionally consistent with the flat-spectrum radio quasar PKS 1424-41, also known as 4FGL J1427.9-4206 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 216.98457 deg, Decl. = -42.10540 deg (J2000; Johnston et al. 1995, AJ, 110, 880), and redshift z = 1.522 (White et al. 1988, ApJ, 327, 561).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on January 12, 2024, with a daily averaged gamma-ray flux (E>100MeV) of (4.2+/-0.8) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 10 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL). The source exhibited increased gamma-ray activity starting from January 9 to January 11, 2024, as seen by AGILE (ATel #16400) and on January 12 as reported by Fermi-LAT Monitor flare alert (GCN/Fermi Notice). The corresponding photon index is 2.07+/-0.08 and is comparable to the 4FGL value of 2.20+/-0.01, with high-energy photons detected up to 11 GeV. The last time that the Fermi-LAT Collaboration announced flaring gamma-ray activity from PKS 1424-41 was December 13, 2022 (ATel #15807).
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. This source is included among the LAT Monitored Sources and consequently, a preliminary estimation of the daily gamma-ray flux observed by Fermi LAT is publicly available at https://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/source/PKS_1424-41. A preliminary light curve is also provided through the Fermi-LAT Light Curve Repository (LCR) at https://fermi.gsfc.nasa.gov/ssc/data/access/lat/LightCurveRepository/source.html?source_name=4FGL_J1427.9-4206. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Francesco Longo (francesco.longo@ts.infn.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.
