Discovery of VHE gamma -ray emission and multi-wavelength observations of the BL Lacertae object 1RXS J101015.9-311909

1RXS J101015.9-311909 is a galaxy located at a redshift of z = 0.14 hosting an active nucleus belonging to the class of bright BL Lac objects. The authors report on results from VHE observations performed between 2006 and 2010 with the H.E.S.S. instrument, an array of four imaging atmospheric Cherenkov telescopes. H.E.S.S. data have been analysed with enhanced analysis methods, making the detection of faint sources more significant. VHE emission at a position coincident with 1RXS J101015.9-311909 is detected with H.E.S.S. for the first time. In a total good-quality livetime of about 49 h, the authors measure 263 excess counts, corresponding to a significance of 7.1 standard deviations. The photon spectrum above 0.2 TeV can be described by a power-law with a photon index of ... . The integral flux above 0.2 TeV is about 0.8% of the flux of the Crab nebula and shows no significant variability over the time reported. (ProQuest: ... denotes formulae/symbols omitted.)