Fermi-LAT detection of renewed gamma-ray activity from the FSRQ PKS 0235-618
ATel #17135; Adithiya Dinesh (Universidad Complutense de Madrid), Janeth Valverde (Marquette University), on behalf of the Fermi Large Area Telescope Collaboration
on 7 Apr 2025; 01:04 UT
Credential Certification: Janeth Valverde (valverde@llr.in2p3.fr)
Subjects: Gamma Ray, >GeV, VHE, 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 renewed gamma-ray activity from a source positionally consistent with the flat-spectrum radio quasar PKS 0235-618, also known as 4FGL J0236.8-6136 (4FGL; The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 39.22186 deg, Dec. = -61.60422 deg (J2000; Xu et al., 2019, ApJS, 242, 5), and redshift z=0.465 (Healey, S. et al. 2008, ApJS, 175, 97).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on April 5, 2025, with a daily averaged gamma-ray flux (E>100MeV) of (0.7+/-0.1) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 50 relative to the average flux reported in the 4FGL-DR4 (Ballet, J. et al. 2023). The corresponding photon index is 1.9+/-0.1, indicating a significantly harder spectrum than the 4FGL value of 2.29+/-0.03. We have reported previous flares from this source in ATel #2669 and #16994.
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 0235-618 can be accessed via the Fermi-LAT Light-Curve Repository at LCR, and via the Monitored Source List at MSL. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Sara Cutini (sara.cutini@asdc.asi.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.
