4 research outputs found
A Search for TeV Gamma-Ray Emission from Pulsar Tails by VERITAS
We report on the search for very-high-energy gamma-ray emission from the regions around three nearby supersonic pulsars (PSR B0355+54, PSR J0357+3205, and PSR J1740+1000) that exhibit long X-ray tails. To date there is no clear detection of TeV emission from any pulsar tail that is prominent in X-ray or radio. We provide upper limits on the TeV flux, and luminosity, and also compare these limits with other pulsar wind nebulae detected in X-rays and the tail emission model predictions. We find that at least one of the three tails is likely to be detected in observations that are a factor of 2–3 more sensitive. The analysis presented here also has implications for deriving the properties of pulsar tails, for those pulsars whose tails could be detected in TeV
A VERITAS/Breakthrough Listen Search for Optical Technosignatures
The Breakthrough Listen Initiative is conducting a program using multiple
telescopes around the world to search for "technosignatures": artificial
transmitters of extraterrestrial origin from beyond our solar system. The
VERITAS Collaboration joined this program in 2018, and provides the capability
to search for one particular technosignature: optical pulses of a few
nanoseconds duration detectable over interstellar distances. We report here on
the analysis and results of dedicated VERITAS observations of Breakthrough
Listen targets conducted in 2019 and 2020 and of archival VERITAS data
collected since 2012. Thirty hours of dedicated observations of 136 targets and
249 archival observations of 140 targets were analyzed and did not reveal any
signals consistent with a technosignature. The results are used to place limits
on the fraction of stars hosting transmitting civilizations. We also discuss
the minimum-pulse sensitivity of our observations and present VERITAS
observations of CALIOP: a space-based pulsed laser onboard the CALIPSO
satellite. The detection of these pulses with VERITAS, using the analysis
techniques developed for our technosignature search, allows a test of our
analysis efficiency and serves as an important proof-of-principle.Comment: 15 pages, 7 figure
VERITAS discovery of very high energy gamma-ray emission from S3 1227+25 and multiwavelength observations
We report the detection of very high energy gamma-ray emission from the
blazar S3 1227+25 (VER J1230+253) with the Very Energetic Radiation Imaging
Telescope Array System (VERITAS). VERITAS observations of the source were
triggered by the detection of a hard-spectrum GeV flare on May 15, 2015 with
the Fermi-Large Area Telescope (LAT). A combined five-hour VERITAS exposure on
May 16th and May 18th resulted in a strong 13 detection with a
differential photon spectral index, = 3.8 0.4, and a flux level
at 9% of the Crab Nebula above 120 GeV. This also triggered target of
opportunity observations with Swift, optical photometry, polarimetry and radio
measurements, also presented in this work, in addition to the VERITAS and
Fermi-LAT data. A temporal analysis of the gamma-ray flux during this period
finds evidence of a shortest variability timescale of = 6.2
0.9 hours, indicating emission from compact regions within the jet, and the
combined gamma-ray spectrum shows no strong evidence of a spectral cut-off. An
investigation into correlations between the multiwavelength observations found
evidence of optical and gamma-ray correlations, suggesting a single-zone model
of emission. Finally, the multiwavelength spectral energy distribution is well
described by a simple one-zone leptonic synchrotron self-Compton radiation
model.Comment: 18 pages, 6 figures. Accepted for publication in the Astrophysical
Journal (ApJ