Fermi-LAT detection of renewed gamma-ray activity from PKS 0235-618

ATel #17766; F. Casaburo (INAF - Astronomical Observatory of Rome, INFN - Rome Tor Vergata, Sapienza University Rome), S. Ciprini (INFN - Rome Tor Vergata, ASI- SSDC) and G. La Mura (INAF-OAC), on behalf of the Fermi Large Area Telescope Collaboration
on 26 Apr 2026; 16:12 UT
Credential Certification: Giovanni La Mura (giovanni.lamura@inaf.it)

Tweet

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 FSRQ PKS 0235-618, also known as 4FGL J0236.8-6136 (The Fermi-LAT collaboration 2020, ApJS, 247, 1), 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 et al. 2008, ApJS, 175, 97).

Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on April 25, 2026, with a daily averaged gamma-ray flux (E>100MeV) of (2.5+/-0.3) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of more than 180 relative to the average flux reported in the fourth data release of the fourth Fermi-LAT catalog (4FGL-DR4, Ballet et al. 2023, arXiv:2307.12546). This is the highest daily flux so far observed by Fermi-LAT from this source. The corresponding photon index is 1.9+/-0.1, indicating a significantly harder spectrum than the 4FGL-DR4 value of 2.29+/-0.03. The spectral hardening led to the detection of an E=14 GeV photon having a probability of being associated with the source of p > 0.99. The Fermi-LAT Collaboration has previously reported flaring activity from this source in ATels #17135, #16994, and #2669.

Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. A preliminary light curve for FSRQ PKS 0235-618 can be accessed via the Fermi-LAT Light-Curve Repository. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Sara Cutini (sara[dot]cutini[at]asdc[dot]asi[dot]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.