Fermi-LAT detection of renewed gamma-ray activity from the FSRQ PKS 0405-385
ATel #17448; Adithiya Dinesh (Universidad Complutense de Madrid), P. Monti-Guarnieri (University of Trieste and INFN Trieste), and Giovanni La Mura (INAF - Astronomical Observatory of Cagliari), on behalf of the Fermi Large Area Telescope Collaboration
on 20 Oct 2025; 19:33 UT
Credential Certification: Adithiya Dinesh (adinesh@ucm.es)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN
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 0405-385, also known as 4FGL J0407.0-3826 (Abdollahi et al. 2022, ApJS, 260, 53), with coordinates R.A. = 61.74598 deg, Dec. = -38.44112 deg (J2000; Fey et al., 2004, AJ, 127, 3587), and redshift z=1.285 (Veron et al., 1990, A&AS, 86, 543).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on October 19, 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 about a factor of 20 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). The corresponding photon index is 2.1+/-0.1, indicating a slightly harder spectrum than the 4FGL-DR4 value of 2.38 +/- 0.02. The Fermi LAT Collaboration has previously reported flaring activity from this source in ATel #16183.
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 0405-385 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_J0407.0-3826. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Denis Bernard (denis.bernard@in2p3.fr).
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.
