Fermi LAT detection of renewed activity from the FSRQ NRAO 190 and of enhanced high energy emission from the BL Lac PKS 2005-489

ATel #17102; P. Monti-Guarnieri (University of Trieste and INFN Trieste), on behalf of the Fermi Large Area Telescope Collaboration
on 23 Mar 2025; 08:03 UT
Credential Certification: Giovanni La Mura (giovanni.lamura@inaf.it)

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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 NRAO 190 (also known as PKS 0440-00 and 4FGL J0442.6-0017, The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 70.66109 deg, Decl. = -0.29539 deg (J2000; Johnston et al., 1995, AJ, 110, 880), and redshift z=0.844 (Hewitt & Burbidge 1987, ApJS, 63, 1).

Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on March 21, 2025, with a daily averaged gamma-ray flux (E>100MeV) of (1.8 +/- 0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 25 relative to the average flux reported in the fourth release of the Fourth Fermi-LAT catalog (4FGL-DR4, Ballet et al. 2024, arXiv:2307.12546). The corresponding photon index is 2.0 +/- 0.1, indicating a harder spectrum than the 4FGL-DR4 value of 2.45 +/- 0.02. We have previously reported flares from this source in ATels #16563, #16395, #5156 and #2049.

The LAT has also observed renewed gamma-ray activity from a source positionally consistent with the BL Lac source PKS 2005-489, also known as 4FGL J2009.4-4849 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 302.35579 deg, Dec. = -48.83158 deg (J2000; Johnston et al. 1995, AJ, 110, 880), and redshift z=0.071 (Keeney et al, 2018, ApJS, 237, 11).

Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on March 21, 2025, as confirmed by the detection of three high-energy photons associated with the source at a confidence level p > 0.95. The highest energy event was a 291 GeV photon observed at 03:58:47 UTC. A likelihood analysis of the high-energy data over the period from March 13, 00:43:01 UTC to March 22, 05:36:22 UTC revealed a flux above 10 GeV of (3.9 +/- 1.8) X 10^-9 photons cm^-2 s^-1, a 10-fold increase over the 3FHL catalog value of (3.9 +/- 0.4) X 10^-10 photons cm^-2 s^-1 (Ajello et al., 2017, ApJS, 232, 18). The flux above 100 MeV in the same period is (2.9 +/- 1.3) X 10^-8 photons cm^-2 s^-1, statistically compatible with the 4FGL-DR4 catalog value of (1.62 +/- 0.04) X 10^-8 photons cm^-2 s^-1. The corresponding photon index is 1.4 +/- 0.2, indicating a significantly harder spectrum than the 4FGL-DR4 value of 1.84 +/- 0.02.

Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of these sources will continue. A preliminary light curve for NRAO 190 can be accessed via the Fermi-LAT Light-Curve Repository at 4FGL_J0442.6-0017, and via the Monitored Source List at NRAO_190. We encourage multifrequency observations of these sources. For NRAO 190, the Fermi-LAT contact people are S. Ciprini (stefano.ciprini@pg.infn.it) and F. Longo (francesco.longo@ts.infn.it). For PKS 2005-489, the Fermi-LAT contact person is P. Monti-Guarnieri (pietro.monti-guarnieri@phd.units.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.