Fermi LAT detection of increased gamma-ray activity from the FSRQ PKS 2255-282
ATel #3948; Michael Dutka (Catholic U), Filippo D`Ammando (INAF-IRA Bologna) and Roopesh Ojha (NASA/GSFC) on behalf of the Fermi Large Area Telescope Collaboration
on 1 Mar 2012; 22:20 UT
Credential Certification: Roopesh Ojha (Roopesh.Ojha@gmail.com)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar, Quasar
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed increasing gamma-ray flux from a source positionally consistent with the flat spectrum radio quasar PKS 2255-282 (also known as 2FGL J2258.0-2759, Nolan et al. 2012, ApJ in press; R.A.=22h58m05.962876s, Dec.=-27d58m21.5574s, J2000; Lanyi et. al. 2010 AJ, 139 1695) which has a redshift of 0.925840 (Jones et. al. 2009; MNRAS, 399, 683). VLBI images at 15 GHz (MOJAVE e. g. Lister et. al. 2009 AJ, 137, 3718) as well as 22 and 43 GHz (Charlot et. al. 2010 AJ, 139 1713) reveal a very compact, core dominated structure particularly at the higher radio frequencies.
Preliminary analysis indicates that the source was in a high state on February 26 2012 with a daily averaged gamma-ray flux (E>100MeV) of (1.0 +/- 0.3) x10^-6 photons/cm^2/s (errors are statistical only) which represents an increase of a factor of about 14 with respect to the flux in the 2FGL catalog. This is the first significant daily averaged detection at a flux of 1.0 x10^-6 photons/cm^2/s by Fermi/LAT. However a gamma-ray flare from this source was detected by EGRET in 1997 (Macomb et. al. ApJ 1999 513, 652).
Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. Further multi-wavelength observations are encouraged. For this source the Fermi LAT contact person is Michael Dutka (ditko86@gmail.com).
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.
