Fermi-LAT detection of a new gamma-ray source Fermi J0139.5+2928
ATel #12888; A. Gokus (University of Wuerzburg, Remeis Observatory Bamberg & ECAP), R. Angioni (MPIfR Bonn) on behalf of the Fermi Large Area Telescope Collaboration
on 25 Jun 2019; 22:16 UT
Credential Certification: Roberto Angioni (angioni@mpifr-bonn.mpg.de)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, on 23 June 2019 has observed gamma-ray activity from a previously unidentified transient source, i.e., Fermi J0139.5+2928. The preliminary best-fit location of the gamma-ray source is R.A. = 24.88 deg, Decl. = +29.47 deg (J2000), with a 95% confidence that the source is within 0.30 deg of this position (statistical errors only). This source is not in any published Fermi LAT catalog and there is no previously reported EGRET nor AGILE gamma-ray detection at this location. A search of the NASA Extragalactic Database (NED) reveals several potential counterparts within the LAT localization 95% error circle, among which is the flat-spectrum radio object TXS 0135+291, a.k.a. B2 0135+29 (RA = 24.65, Dec = 29.37 (J2000), redshift unknown).
Preliminary analysis of the LAT data indicates that Fermi J0139.5+2928 was detected on June 23, 2019, with a daily averaged gamma-ray flux (E>100MeV) of (0.4 +/- 0.1) X 10^-6 photons cm^-2 s^-1 and a single power-law photon index of 2.3 +/- 0.3 (statistical uncertainties only). The significance of the source detection for the entire LAT exposure for 23 June 2019 is approximately 6 sigma.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact persons are Andrea Gokus (andrea.gokus@astro.uni-wuerzburg.de) and Roberto Angioni (angioni@mpifr-bonn.mpg.de).
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.
