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Durham University

Department of Physics

Staff profile

Publication details for Dr Anthony Brown

Brown, Anthony M. (2014). Very high energy γ -ray emission from RBS 0970. Monthly Notices of the Royal Astronomical Society: Letters 442(1): L56-L60.

Author(s) from Durham


In this Letter I report the Fermi Large Area Telescope (LAT) detection of very high energy (VHE; E > 100 GeV) γ -ray emission from the BL Lac object RBS 0970. 5.3 years of LAT observations revealed the presence of three VHE photon events within 0.◦1 of RBS 0970, with a subsequent unbinned likelihood analysis finding RBS 0970 to be a source of VHE photons at the 6.5σ level of confidence. The ≥1 GeV flux, binned in monthly periods, did not indicate
any flux brightening of RBS 0970 accompanying the emission of the VHE photons. However, a likelihood analysis of the 0.1−100 GeV flux, binned in 28 d periods centred on detection
of the VHE photons, revealed that the emission of the lowest energy VHE photons coincided with a hardening of the γ -ray spectrum. Interestingly, the same analysis did not find any
significant γ -ray emission from RBS 0970 during the emission of the highest energy VHE event. The discovery of RBS 0970 as a VHE emitter, combined with the spectral variability, suggest RBS 0970 to be a good candidate for follow-up observations with ground-based γ -ray