|Upper Limits from Five Years of Blazar Observations with the VERITAS Telescopes|
Reference: S. Archambault et al. (The VERITAS Collaboration), Astronomical Journal 151: 142, 2016
Contacts: Matteo Cerruti
Blazars are the most common extragalactic sources of very-high-energy (VHE, E > 100 GeV) photons and VERITAS has already detected emission from 32 of them. However, much larger number of blazars were observed by VERITAS without being detected, and only an upper limit on their VHE flux can be determined. In this work, we present the analysis results from a sample of 114 blazars observed, but non-detected, by VERITAS from 2007 to 2012. The sample corresponds to about 570 hours of observing time, and also includes all the sources from the second Fermi-LAT (2FGL) catalog which fall in the field of view of the VERITAS observations. For every source in our sample, we provide the details of the observations and the upper limit on its VHE flux as measured with the VERITAS telescopes. We performed a variety of stacked analyses of the individual results (e.g. by blazar type). One of these shows evidence for an excess of gamma rays at the 4 sigma level in the overall sample, which can also be seen as a shift in the observed significance distributions (see Figure 1) .
Figures from paper (click to get full size image):
|Last Updated on Sunday, 13 November 2016 17:03|