Fermi LAT detection of renewed high gamma ray activity from FSRQs 4C+27.50 and PKS 0131-522
ATel #16718; Fausto Casaburo (INFN Roma Tor Vergata & SSDC ASI), Federica Giacchino (INFN Roma Tor Vergata & SSDC ASI), Stefano Ciprini (INFN Roma Tor Vergata & SSDC ASI) and Giovanni La Mura (INAF â OAC), on behalf of the Fermi Large Area Telescope Collaboration
on 19 Jul 2024; 08:08 UT
Credential Certification: Federica Giacchino (federica.giacchino@roma2.infn.it)
Subjects: Gamma Ray, 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 (FSRQ) 4C +27.50, also known as 4FGL J2321.9+273 in the 14-year fourth Fermi-LAT catalog Data Release 4 (4FGL-DR4) (Ballet et al. 2024, arXiv:2307.12546). This source has coordinates RA = 350.49943 deg, Dec = 27.54623 deg (J2000; Johnson et al. 1995, AJ, 110, p.880, p.915 ) and redshift z=1.26 (Sexton R. O, A.J.S.S., vol. 260, issue 2, 2022). Preliminary analysis indicates that 4C +27.50 was flaring on July 15, 2024 reaching a daily averaged gamma-ray flux (E>100MeV) of (1.2+/-0.2) x 10^-6 photons cm^-2 s^-1 (statistical uncertainty only), that is approximately 60 times higher than 4FGL-DR4. The corresponding spectral index was 2.2+/-0.1, that is compatible with the 4FGL-DR4 value 2.28+/-0.32. For this source, the Fermi-LAT contact person is Giovanni La Mura (giovanni.lamura@inaf.it).
The Fermi LAT has also observed enhanced gamma-ray activity from a source positionally consistent with the FSRQ PKS 0131-522, also known as 4FGL J0133.1-5201 in 4FGL-DR4. This source has coordinates RA = 23.27401 deg, Dec = -52.00110 deg (J2000; Johnson et al. 1995, AJ, 110, p.880, p.915 ) and uncertain redshift. Preliminary analysis indicates that PKS 0131-522 was in an elevated and hard gamma-ray emission state on July 15, 2024 reaching a daily averaged gamma-ray flux (E>100MeV) of (0.7+/-0.1) x 10^-6 photons cm^-2 s^-1 (statistical uncertainty only), that is approximately 25 times higher than 4FGL-DR4. The corresponding spectral index was 1.8+/-0.1, which indicates a harder spectrum than the 4FGL-DR4 value 2.35+/-0.02. For this source, the Fermi-LAT contact persons are Giacomo Principe (giacomo.principe@ts.infn.it) and Josefa Becerra (josefa.becerra@nasa.gov).
Due to the enhanced gamma-ray activity of these sources, we encourage multifrequency observations of both of them.
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.
