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Vela 5B All-Sky Monitor Lightcurves
Data for these sources were obtained from the Vela 5B all-sky XC detector. The Vela 5B nuclear test detection satellite was part of a program run jointly by the Advanced Research Projects of the U.S. Department of Defense and the U.S.Atomic Energy Commission, managed by the U.S. Air Force. It was placed in a nearly circular orbit at a geocentric distance of ~118,000 km on 23 May 1969; the orbital period was ~112 hours. The satellite rotated about its spin axis with a ~64-sec period. The X-ray detector was located ~90 degrees from the spin axis, and so covered the celestial sphere twice per satellite orbit. Data were telemetered in 1-sec count accumulations. Vela 5B operated until 19 June 1979, although telemetry tracking was poor after mid-1976. The scintillation X-ray detector (XC) aboard Vela 5B consisted of two 1-mm-thick NaI(Tl) crystals mounted on photomultiplier tubes and covered by a 5-mil-thick beryllium window. Electronic thresholds provided two energy channels, 3-12 keV and 6-12 keV. In front of each crystal was a slat collimator providing a FWHM aperture of ~6.1x6.1 degrees. The effective detector area was ~26 sq-cm. Sensitivity to celestial sources was severely limited by the intrinsic detector background of ~36 cts/sec. The Vela 5B X-ray detector yielded ~40 cts/sec for the Crab, so 1 Vela ct/sec ~25 UFU~4.5E-10 ergs/sq-cm/sec in the 3-12 keV response band. This is a service provided by NASA HEASARC .
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VERITAS Source Catalog
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The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is a major ground-based gamma-ray observatory operating at the Fred Lawrence Whipple Observatory (FLWO) in southern Arizona, USA. It is an array of four 12m optical telescopes for gamma-ray astronomy in the GeV - TeV energy range. VERITAS is an imaging air Cerenkov system. Gamma-rays from astrophysical sources create particle showers in the Earth's upper atmosphere that produce Cerenkov photons detected on the ground using the large optical telescopes. These telescopes are deployed such that they have the highest sensitivity in the VHE energy band (50 GeV - 50 TeV), with maximum sensitivity from 100 GeV to 10 TeV. The four telescope array is needed for stereoscopic observations that allow the reconstruction of the particle shower geometry, thus giving precise angular and energy resolution. This very high energy observatory, completed in 2007, effectively complements the Fermi Gamma-ray Space Telescope due to its large collection area as well as its higher energy bound and improved angular resolution. VERITAS started four-telescope operations in 2007 and collects about 1100 hours of good-weather data per year. The VERITAS collaboration has published over 100 journal articles since 2008 reporting on gamma-ray observations of a large variety of objects: Galactic sources like supernova remnants, pulsar wind nebulae, and binary systems; extragalactic sources like star forming galaxies, dwarf-spheroidal galaxies, and highly-variable active galactic nuclei. Additional details are available at the VERITAS website. The catalog lists the sources observed by VERITAS as of April 2022, including cross-matches with other gamma-ray observations and spectral fits. This catalog has associated high-level data products containing data from VERITAS publications. This database table was ingested by the HEASARC in December 2022 and is based upon data files provided by the VERITAS Team. A minor correction to one entry in the catalog was made in April 2024.

High-level data products were collected from VERITAS publications. Data and fit results were extracted from the published papers or from internal VERITAS analysis results used to produce the published figures and tables. In many cases, spectral and light curve data were obtained by digitizing published figures. This process was led by Gernot Maier at DESY with contributions from many members of the VERITAS collaboration. The primary archive can be accessed on GitHub or downloaded via Zenodo (doi:10.5281/zenodo.6163391). Translation to formats suitable for the HEASARC was led by Philip Kaaret with assistance by Sameer Patel at the University of Iowa and by the HEASARC Team. This is a service provided by NASA HEASARC .

CNOFS VEFI 500-msec Optical Lightning Data
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This data set contains the low rate data from the C/NOFS Vector Electric Field Instrument (VEFI) lightning detector during nighttime passes of the satellite along its low inclination (13 degree) orbit and within the altitude domain defined by the satellite's perigee and apogee of 401 km and 867 km, respectively. Two photodiodes measure white light irradiance at 2 Hz in 7 threshold values and in 2 look directions (north and south). Data are at 0.5-sec resolution. The lightning detector data may be used to identify a possible relationship between the occurrence of lightning and the occurrence of Spread-F caused, deep density dropouts in the ionosphere. Reference: Jacobson et al, J Atm Ocean Tech, 2011, doi:10.1175/JTECH-D-11-00047.1