Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ 4C +10.45
ATel #16889; Adithiya Dinesh (Universidad Complutense de Madrid), Giovanni La Mura (INAF - O. A. Cagliari), on behalf of the Fermi Large Area Telescope Collaboration
on 31 Oct 2024; 13:00 UT
Credential Certification: Denis Bernard (Denis.bernard@in2p3.fr)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar, Quasar
Referred to by ATel #: 16892
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 4C +10.45, also known as 4FGL J1608.7+1029 (4FGL-DR4; Ballet et al. 2024, arXiv:2307.12546), with coordinates R.A. = 242.19251 deg, Decl. = +10.48549 deg (J2000; Le Bail et al. 2016, AJ, 151, 79L), and redshift z=1.233 (SDSS-DR13, Albareti et al. 2017, ApJS, 233, 25).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on October 29, 2024 , with a daily averaged gamma-ray flux (E>100MeV) of (0.9+/-0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 30 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 2.24+/-0.17, indicating a significantly harder spectrum than the 4FGL value of 2.53+/-0.03.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. A preliminary light curve for 4C +10.45 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_J1608.7+1029. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Adithiya Dinesh (adinesh@ucm.es).
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.
