Fermi LAT detection of the first GeV gamma-ray flare from the FSRQ TXS 2358+209
ATel #8659; Sara Cutini (ASDC/INFN) on behalf of Fermi Large Area Telescope Collaboration.
on 9 Feb 2016; 16:47 UT
Credential Certification: Stefano Ciprini (stefano.ciprini@asdc.asi.it)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar
Referred to by ATel #: 8709
The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope, has observed for the first time gamma-ray outburst activity from a source positionally consistent with the FSRQ TXS 2358+209 (a.k.a. CRATES J0001+2113, 3FGL J0001.4+2120, Acero et al. 2015, ApJS, 218, 23) at R.A. = 0.38487 deg, Dec. = 21.22674 deg (J2000, Jackson et al. 2007, MNRAS, 376, 371) with redshift z=1.106 (Falco et al. 1998, ApJ, 494, 47).
Preliminary analysis indicates that TXS 2358+209 was in a high state on 5, 6, and 7 February. Integrating these three days (from 05-02-2016 00:00:00 to 08-02-2016 00:00:00 UTC), it was detected with an average flux (E>100 MeV) of (1.3 +/- 0.1)X10^-6 ph cm^-2 s^-1 and photon power-law index of 2.4+/-0.1 (errors are statistical only). This corresponds to a flux increase of about a factor of 65 compared with the baseline flux reported in the Third Fermi-LAT Catalog (3FGL). The photon power-law index in the 3FGL catalog is 2.8 with no reported uncertainty; the spectral model for the source in 3FGL was LogParabola and the index for a power-law fit was reported just for reference. The EGRET source 3EG J2359+2041 (Hartman et al. 1999, ApJS, 123, 79) was associated in the past with a different source, PKS 2356+196. The improved Fermi-LAT position shows that the most probable counterpart for the 3EG source is TXS 2358+209.
Since Fermi operates in all-sky survey mode, gamma-ray monitoring of this source will continue. In consideration of the activity of this source we strongly encourage multi-wavelength observations. The Fermi LAT contact person for this source is S. Cutini (sara.cutini@asdc.asi.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.
