Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ S4 1726+45
ATel #16063; Chiara Bartolini (INFN Bari), on behalf of the Fermi Large Area Telescope Collaboration
on 29 May 2023; 21:33 UT
Credential Certification: Isabella Mereu (mereuisabella@gmail.com)
Subjects: Gamma Ray, 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 enhanced gamma-ray activity from a source positionally consistent with the flat-spectrum radio quasar S4 1726+45, also known as 4FGL J1727.4+4530 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 261.865212 deg, Decl. = 45.511036 (J2000; Johnston et al. 1995, AJ 110, 880), and redshift z = 0.71700 (Henstock et al., 1997, MNRAS 290, 280).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on May 27, 2023, with a daily averaged gamma-ray flux (E>100MeV) of (1.9+/- 1.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of about 40 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL). The corresponding photon index is 2.3 +/- 0.2, which is similar to the 4FGL value of 2.49+/-0.02.
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_J1727.4+4530. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Chiara Bartolini (chiara.bartolini@ba.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.
