Fermi-LAT detection of renewed gamma-ray activity from the high-redshift FSRQ PKS 0601-70
ATel #17359; F. Longo (University of Trieste and INFN Trieste) and A. Holzmann Airasca (University of Trento & INFN Bari), on behalf of the Fermi Large Area Telescope Collaboration
on 26 Aug 2025; 07:06 UT
Credential Certification: Chiara Bartolini (chiara.bartolini-1@unitn.it)
Subjects: Gamma Ray, >GeV, AGN, Blazar
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 PKS 0601-70, also known as 4FGL J0601.1-7035 (Abdollahi et al. 2022, ApJS, 260, 53), with coordinates R.A. = 90.29717 deg, Dec. = -70.60239 deg (J2000; Healey et al. 2007, ApJS, 171, 61), and redshift z=2.409 (Shaw et al. 2012, ApJ, 748, 49).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on August 24, 2025, with a daily averaged gamma-ray flux (E>100MeV) of (0.5+/-0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 10 relative to the average flux reported in the fourth data release of the Fermi-LAT catalog (4FGL-DR4, Ballet et al. 2023, arXiv:2307.12546). The corresponding photon index is 2.3+/-0.3, and is consistent with the 4FGL-DR4 value of 2.37 +/- 0.02 within the uncertainties. The Fermi-LAT Collaboration has previously reported enhanced activity from this source in ATel #13506.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. A preliminary light curve for PKS 0601â70 can be accessed via the Fermi-LAT Light-Curve Repository at 4FGL J0601.1-7035. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is I. Mereu (isabella.mereu@pg.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.
