Fermi LAT detection of a GeV flare from the BL Lac object PKS 2233-148
ATel #4152; Stefano Ciprini (ASI Science Data Center and INAF Observatory of Rome, Italy), on behalf of the Fermi Large Area
on 5 Jun 2012; 17:12 UT
Credential Certification: Stefano Ciprini (stefano.ciprini@asdc.asi.it)
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, has observed gamma-ray flaring activity from a source positionally consistent with the BL Lac object PKS 2233-148 (also known as 2FGL J2236.5-1431, Nolan et al. 2012, ApJS, 199, 31, and OY -156) placed at R.A.: 339.1420296 deg, Dec.: -14.5561633 (J2000, Petrov et al. 2008, AJ, 136, 580). No redshift for the source has been measured up to now, demonstrating the BL Lac object character type of this source. An upper limit of z>0.65 was estimated by Sbarufatti et al. (2006, AJ, 132, 1) while intervening systems are claimed at z=0.492 and z=0.609 (Sbarufatti et al. 2006, AJ, 132, 1; Drinkwater et al. 1997, MNRAS, 284, 85).
Preliminary analysis indicates that on 2012 June 4, PKS 2233-148 was in a high state with an average daily gamma-ray flux (E>100MeV) of (0.9 +/- 0.2) x 10^-6 photons cm^-2 s^-1 about 14 times greater than the average flux reported in the second Fermi LAT catalog (2FGL), reaching in the next 6-hour bin (00:00-06:00 UTC of 2012 June 5) a flux (E>100MeV) of (2.0 +/- 0.5) x 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). Fermi LAT already reported a high gamma-ray state from this source in April 2010 (ATel#2589).
Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. In consideration of the ongoing activity of this source we encourage multiwavelength observations. For this source the Fermi LAT contact person is K. Sokolovsky (kirx@scan.sai.msu.ru).
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.
