Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ CTS 0490
ATel #16618; Samantha Lopez (LLR, Ecole Polytechnique & CNRS / IN2P3), Denis Bernard (LLR, Ecole Polytechnique & CNRS / IN2P3), on behalf of the Fermi Large Area Telescope Collaboration
on 8 May 2024; 19:01 UT
Credential Certification: Denis Bernard (Denis.bernard@in2p3.fr)
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 enhanced gamma-ray activity from a source positionally consistent with the flat-spectrum radio quasar CTS 0490, also known as NVSS J232528-355755, 2MASS J23252861-3557543 and 4FGL J2325.4-3559 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 351.369 deg, Decl. = -35.965 deg (J2000; W. Barkhouse et al. 2001, AJ, 121, 2843), and redshift z=0.36 (J. Maza et al. 1995, RMxAA, 31, 119).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on May 7, 2024, with a daily averaged gamma-ray flux (E>100MeV) of (0.31 +/- 0.09) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 15 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL). This is the highest LAT daily flux ever observed for this source. The corresponding photon index is 1.83 +/- 0.16, indicating a significantly harder spectrum than the 4FGL value of 2.31 +/- 0.024.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. A preliminary light curve for CTS 0490 can be accessed via the Fermi-LAT Light-Curve Repository at LCR. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Samantha Lopez (lopez@llr.in2p3.fr).
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.
