Fermi-LAT detection of enhanced gamma-ray activity from the blazar PKS 1716-771
ATel #15336; C. C. Cheung (NRL), G. La Mura (LIP, Portugal), on behalf of the Fermi Large Area Telescope Collaboration
on 18 Apr 2022; 21:07 UT
Credential Certification: Teddy Cheung (Teddy.Cheung@nrl.navy.mil)
Subjects: Gamma Ray, >GeV, Blazar
Referred to by ATel #: 15381
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed enhanced gamma-ray activity from a source positionally consistent with the blazar PKS 1716-771, also known as 4FGL J1723.6-7714 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 260.961855 deg, Decl. = -77.230706 deg (J2000; Petrov et al. 2011, MNRAS, 414, 2528), and without a spectroscopic redshift (see Kaur et al. 2018, ApJ, 859, 80).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on 2022 April 17, with a daily averaged gamma-ray flux (E>100MeV) of (5.8+/-1.7) X 10^-7 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of about 15 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL). This is the highest daily flux ever observed for this source by the LAT. The measured photon index is 2.1+/-0.2, consistent with its average spectrum (4FGL value of 2.29+/-0.02). Recent optical activity was reported from this blazar by Gaia on 2022 April 03.471 (Gaia22bll = AT2022hfb).
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. A preliminary light curve can be accessed via the Fermi-LAT Light-Curve Repository at https://fermi.gsfc.nasa.gov/ssc/data/access/lat/LightCurveRepository/source.html?source_name=4FGL_J1723.6-7714 . We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Teddy Cheung (Teddy.Cheung at nrl.navy.mil).
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.
