Fermi LAT detection of a GeV flare from the high redshift BL Lac object PKS 2131-021
ATel #4333; Stefano Ciprini (ASI ASDC and INAF-OAR Rome, Italy), on behalf of the Fermi Large Area Telescope Collaboration.
on 24 Aug 2012; 12:45 UT
Credential Certification: Stefano Ciprini (stefano.ciprini@asdc.asi.it)
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 gamma-ray flaring activity from a source positionally consistent with the BL Lac object PKS 2131-021 (also known as 2FGL J2133.8-0154, Nolan et al. 2012, ApJS, 199, 31, and 4C -02.81) placed at radio coordinates R.A.: 323.5429567 deg, Dec.: -1.8881217 deg (J2000, Johnston et al. 1995, AJ, 110, 880). The redshift of this highly polarized and microwave-selected BL Lac object is z=1.284 (Drinkwater et al. 1997, MNRAS, 284, 85; Rector & Stocke 2001, AJ, 122, 565; Sbarufatti et al. 2006, AJ, 132, 1).
Preliminary analysis indicates that on 2012 August 21, PKS 2131-021 was in a high state with an average daily gamma-ray flux (E>100MeV) of (0.6 +/- 0.2) x 10^-6 photons cm^-2 s^-1 about 30 times greater than the average flux reported in the second Fermi LAT catalog (2FGL), and with a hard gamma-ray photon spectral index of 1.7 +/- 0.2. Fermi LAT detected increased activity of PKS 2131-021 starting from this 2012 July.
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 persons are Roopesh Ojha (roopesh.ojha@nasa.gov) and Stefano Ciprini (stefano.ciprini@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.
