Discovery of very high-energy γ-ray emission from the LBL object BL Lacertae
نویسندگان
چکیده
The low-frequency peaked BL Lac (LBL) object BL Lacertae was observed with the MAGIC telescope from 2005 August to December (22.2 hr), and from 2006 July to September (26.0 hr). A very high energy (VHE) γ-ray signal was discovered with a 5.1 σ excess in the 2005 data. Above 200 GeV, an integral flux of (0.6± 0.2) × 10 cm s was measured, corresponding to approximately 3% of the Crab flux. The differential spectrum between 150 and 900 GeV is rather steep, with a photon index of −3.6± 0.5. The light curve shows no significant variability during the observations in 2005. For the first time a clear detection of VHE γ-ray emission from an LBL object was obtained. The 2006 data show no significant excess. This drop in flux follows the observed trend in optical activity.
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