Fermi-LAT detection of enhanced gamma-ray activity from the flat-spectrum radio source PMN J1830-4441
ATel #17148; Omer Faruk Coban (Institute of Space Sciences, ICE-CSIC), P. Monti-Guarnieri (University of Trieste and INFN Trieste), Giovanni La Mura (INAF-O. A. Cagliari), on behalf of the Fermi Large Area Telescope Collaboration
on 16 Apr 2025; 20:36 UT
Credential Certification: Giovanni La Mura (giovanni.lamura@inaf.it)
Subjects: Gamma Ray, >GeV
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 source PMN J1830-4441, also known as 4FGL J1830.2-4443 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 277.50363 deg, Dec. = -44.68658 deg (J2000; Hunt et al. 2021, AJ, 162, 18).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on April 15, 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 value is about 20 times larger than the average flux reported in the fourth Fermi-LAT catalog (4FGL). The corresponding photon index is 1.9+/-0.2, indicating a significantly harder spectrum than the 4FGL value of 2.6+/-0.1. One high-energy photon with E = 12 GeV was associated with the source on April 15 at 20:28:35 UT with a probability p > 0.8. The Fermi-LAT Collaboration has previously reported flaring activity from this source in ATel #15925.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. A preliminary light curve for PMN J1830-4441 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 Adithiya Dinesh (adinesh@ucm.es).
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.
