VERITAS Observations of the BL Lac Object PG 1553+113 Between May 2010 and May 2011

摘要

VERITAS, an array of imaging atmospheric-Cherenkov telescopes, studies blazars in the energy range between 100 GeV and 30 TeV. With its excellent sensitivity at these energies, and ever-deepening source exposures, VERITAS is in a position to probe distant blazars for clear absorption signatures in their very-high-energy gamma-ray spectra due to interactions with the extragalactic background light (EBL). We discuss results from recent VERITAS observations of PG 1553+113 (z>0.4) which have resulted in the most significant very-high-energy detection ever obtained for this source. The most recent VERITAS spectral measurements are used to place an upper limit on the source redshift of z < 0.5 at the 95% confidence level. Also discussed are the prospects of using these observations, along with those of other hardspectrum blazars, to place constraints on the EBL.