Discovery of very high energy gamma rays from PKS 1424+240 and multiwavelength constraints on its redshift

Understand

We report the first detection of very-high-energy (VHE) gamma-ray emission above 140 GeV from PKS 1424+240, a BL Lac object with an unknown redshift.

• The photon spectrum above 140 GeV measured by VERITAS is well described by a power law with a photon index of 3.8 +- 0.5_stat +- 0.3_syst and a flux normalization at 200 GeV of (5.1 +- 0.9_stat +- 0.5_syst) x 10^{-11} TeV^-1 cm^-2 s^-1, where stat and syst denote the statistical and systematical uncertainty, respectively.
• The VHE flux is steady over the observation period between MJD 54881 and 55003 (2009 February 19 to June 21).
• Flux variability is also not observed in contemporaneous high energy observations with the Fermi Large Area Telescope (LAT).