Fermi-LAT detection of renewed gamma-ray activity from a source associated with PMN J1717-5155
ATel #15519; C. C. Cheung (NRL), on behalf of the Fermi Large Area Telescope Collaboration
on 19 Jul 2022; 19:04 UT
Credential Certification: Teddy Cheung (Teddy.Cheung@nrl.navy.mil)
Subjects: Gamma Ray, >GeV, Blazar
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 PMN J1717-5155 (redshift z=1.158; ATel #4777), also known as 4FGL J1717.6-5154 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 17:17:34.6918, Decl. = -51:55:31.925 (J2000; Petrov & Kovalev 2017, MNRAS, 467, L71). Previous gamma-ray flaring activity for this source was reported in 2012 (ATel #4023).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on July 18, 2022 with a daily averaged gamma-ray flux (E>100MeV) of (1.9 +/-0.3) X 10^-6 photons cm^-2 s^-1 (statistical uncertainties only). This corresponds to a flux increase of a factor of about 100 relative to the average flux reported in the incremental version (4FGL-DR3) of the fourth Fermi-LAT catalog (Abdollahi et al. 2022, ApJS, 260, 53). This is the highest daily flux ever observed for this source by the LAT. The measured photon index is 2.7 +/- 0.2, consistent with its average spectrum (4FGL-DR3 value of 2.58 +/- 0.06).
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_J1717.6-5154 . We encourage multifrequency observations of this source. For this source the Fermi LAT contact person is Frank Schinzel (fsch@unm.edu).
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.
