Discovery of High-Energy Gamma-Ray Emission from the BL Lac Object RBS 0413
ATel #2272; Rene A. Ong (UCLA), on behalf of the VERITAS Collaboration; Pascal Fortin (LLR), on behalf of the Fermi Large Area Telescope Collaboration
on 29 Oct 2009; 18:42 UT
Credential Certification: Rene Ong (rene@astro.ucla.edu)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN
The VERITAS and Fermi-LAT Collaborations report the discovery
of gamma-ray emission from the high-frequency-peaked BL Lac
object RBS 0413 (RA: 03h19m51.8s, Dec: +18d45m34s). The redshift
of this blazar is 0.19 (Stocke, J. et al. 1991, ApJS, 76, 813).
Very-high-energy (VHE; >100 GeV) gamma rays were detected in
~16 hours of good-quality observations obtained between
23 September 2008 and 26 October 2009 with the VERITAS
atmospheric-Cherenkov telescope array. Analysis of the VERITAS
data yields a detection of ~270 gamma rays from a source
position that is consistent with RBS 0413, corresponding to a
statistical significance of ~6 standard deviations. The
observed VHE flux is ~2% of the Crab flux above 200 GeV.
The Large Area Telescope (LAT), one of the two instruments
on the Fermi Gamma-ray Space Telescope, detected high-energy
(HE; > 100 MeV) gamma rays from a source positionally consistent
with RBS 0413 with a statistical significance of ~10 standard
deviations. Preliminary analysis of the data taken during the
first 12 months of the mission (4 August 2008 to 4 August 2009)
indicates an average flux above 100 MeV of
(2.4 +/- 1.0) x 10 -9 photons cm -2 s -1, and a very hard
spectral index of (1.42 +/- 0.15). Errors are statistical only.
Multi-wavelength observations of this blazar are encouraged.
The LAT contact person for this blazar is Pascal Fortin
(fortin@poly.in2p3.fr).
Questions regarding the VERITAS observations should be
directed to Rene Ong (rene@astro.ucla.edu).
