Volume 552, April 2013
|Number of page(s)||5|
|Published online||17 April 2013|
Discovery of transient high-energy γ-ray emission from the BL Lacertae object 5C 3.178
1 Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, 10691 Stockholm, Sweden
2 Department of Physics, Stockholm University, AlbaNova, 10691 Stockholm, Sweden
Received: 13 February 2013
Accepted: 13 March 2013
We report the serendipitous discovery of transient, point-like high energy γ-ray emission coincident with the position of the suspected BL Lac object 5C 3.178. The source was detected using the Fermi Large Area Telescope (LAT) at a significance level of ~8σ during a 200 day period which began on November 17th 2011 (MJD 55 882). The observed γ-ray emission is characterised by a moderate 0.2–300 GeV flux F0.2−300 GeV = (8.22 ± 2.04) × 10-9 ph cm-2 s-1 and a hard power law spectrum with spectral index Γ = 1.76 ± 0.09. These properties appear consistent with the known sub-population of TeV γ-ray-emitting BL Lac objects, implying that the source may be detectable using atmospheric Cherenkov telescope arrays. Moreover, the temporal variability of the source suggests that real-time searches of the Fermi-LAT all-sky dataset for weak emission on ~200 day timescales may represent a rewarding strategy.
Key words: astroparticle physics / BL Lacertae objects: individual: 5C 3.178 / gamma rays: galaxies
© ESO, 2013
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.