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Full-Text Articles in Physical Sciences and Mathematics
Tev Gamma-Ray Observations Of The Galactic Center Ridge By Veritas, P. T. Reynolds, Et. Al.
Tev Gamma-Ray Observations Of The Galactic Center Ridge By Veritas, P. T. Reynolds, Et. Al.
Physical Sciences Publications
The Galactic Center ridge has been observed extensively in the past by both GeV and TeV gamma-ray instruments revealing a wealth of structure, including a diffuse component and the point sources G0.9+0.1 (a composite supernova remnant) and Sgr A* (believed to be associated with the supermassive black hole located at the center of our Galaxy). Previous very high energy (VHE) gamma-ray observations with the H.E.S.S. experiment have also detected an extended TeV gamma-ray component along the Galactic plane in the >300 GeV gamma-ray regime. Here we report on observations of the Galactic Center ridge from 2010 to 2014 by the …
Multiwavelength Study Of Quiescent States Of Mrk 421 With Unprecedented Hard X-Ray Coverage Provided By Nustar In 2013, P. T. Reynolds, Nustar, Veritas, Magic
Multiwavelength Study Of Quiescent States Of Mrk 421 With Unprecedented Hard X-Ray Coverage Provided By Nustar In 2013, P. T. Reynolds, Nustar, Veritas, Magic
Physical Sciences Publications
We present coordinated multiwavelength observations of the bright, nearby BL Lacertae object Mrk 421 taken in 2013 January–March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations and instruments, providing data from radio to very high energy (VHE) γ-ray bands. NuSTAR yielded previously unattainable sensitivity in the 3–79 keV range, revealing that the spectrum softens when the source is dimmer until the X-ray spectral shape saturates into a steep ${\rm{\Gamma }}\approx 3$ power law, with no evidence for an exponential cutoff or additional hard components up to ~80 keV. For the first time, we observed both the synchrotron and …
Observations Of The Unidentified Gamma-Ray Source Tev J2032+4130 By Veritas, P. T. Reynolds, Et. Al.
Observations Of The Unidentified Gamma-Ray Source Tev J2032+4130 By Veritas, P. T. Reynolds, Et. Al.
Physical Sciences Publications
TeV J2032+4130 was the first unidentified source discovered at very high energies (VHEs; E > 100 GeV), with no obvious counterpart in any other wavelength. It is also the first extended source to be observed in VHE gamma rays. Following its discovery, intensive observational campaigns have been carried out in all wavelengths in order to understand the nature of the object, which have met with limited success. We report here on a deep observation of TeV J2032+4130 based on 48.2 hr of data taken from 2009 to 2012 by the Very Energetic Radiation Imaging Telescope Array System experiment. The source is …
A Three-Year Multi-Wavelength Study Of The Very-High-Energy Gamma-Ray Blazar 1es 0229+200, P. T. Reynolds, Et. Al.
A Three-Year Multi-Wavelength Study Of The Very-High-Energy Gamma-Ray Blazar 1es 0229+200, P. T. Reynolds, Et. Al.
Physical Sciences Publications
The high-frequency-peaked BL Lacertae object 1ES 0229+200 is a relatively distant (z = 0.1396), hard-spectrum (Γ ~ 2.5), very-high-energy (VHE; E > 100 GeV) emitting γ-ray blazar. VHE measurements of this active galactic nucleus have been used to place constraints on the intensity of the extragalactic background light and the intergalactic magnetic field (IGMF). A multi-wavelength study of this object centered around VHE observations by Very Energetic Radiation Imaging Telescope Array System (VERITAS) is presented. This study obtained, over a period of three years, an 11.7 standard deviation detection and an average integral flux F(E > 300 GeV) = (23.3 ± 2.8stat …
Veritas Observations Of The Nova In V407 Cygni, P. T. Reynolds, Et. Al.
Veritas Observations Of The Nova In V407 Cygni, P. T. Reynolds, Et. Al.
Physical Sciences Publications
We report on very high energy (E > 100 GeV) gamma-ray observations of V407 Cygni, a symbiotic binary that underwent a nova outburst producing 0.1-10 GeV gamma rays during 2010 March 10-26. Observations were made with the Very Energetic Radiation Imaging Telescope Array System during 2010 March 19-26 at relatively large zenith angles due to the position of V407 Cyg. An improved reconstruction technique for large zenith angle observations is presented and used to analyze the data. We do not detect V407 Cygni and place a differential upper limit on the flux at 1.6 TeV of 2.3 × 10–12 erg cm–2 …
Discovery Of Tev Gamma-Ray Emission Toward Supernova Remnant Snr G78.2+2.1, P. T. Reynolds, Et. Al.
Discovery Of Tev Gamma-Ray Emission Toward Supernova Remnant Snr G78.2+2.1, P. T. Reynolds, Et. Al.
Physical Sciences Publications
We report the discovery of an unidentified, extended source of very-high-energy gamma-ray emission, VER J2019+407, within the radio shell of the supernova remnant SNR G78.2+2.1, using 21.4 hr of data taken by the VERITAS gamma-ray observatory in 2009. These data confirm the preliminary indications of gamma-ray emission previously seen in a two-year (2007-2009) blind survey of the Cygnus region by VERITAS. VER J2019+407, which is detected at a post-trials significance of 7.5 standard deviations in the 2009 data, is localized to the northwestern rim of the remnant in a region of enhanced radio and X-ray emission. It has an intrinsic …
Veritas Observations Of The Tev Binary Ls I+61 Degrees 303 During 2008-2010, P. T. Reynolds, Et. Al.
Veritas Observations Of The Tev Binary Ls I+61 Degrees 303 During 2008-2010, P. T. Reynolds, Et. Al.
Physical Sciences Publications
We present the results of observations of the TeV binary LS I +61° 303 with the VERITAS telescope array between 2008 and 2010, at energies above 300 GeV. In the past, both ground-based gamma-ray telescopes VERITAS and MAGIC have reported detections of TeV emission near the apastron phases of the binary orbit. The observations presented here show no strong evidence for TeV emission during these orbital phases; however, during observations taken in late 2010, significant emission was detected from the source close to the phase of superior conjunction (much closer to periastron passage) at a 5.6 standard deviation (5.6σ) post-trials …
Insights Into The High-Energy Gamma-Ray Emission Of Markarian 501 From Extensive Multifrequency Observations In The Fermi Era, P. T. Reynolds, Fermi-Lat, Magic, Veritas
Insights Into The High-Energy Gamma-Ray Emission Of Markarian 501 From Extensive Multifrequency Observations In The Fermi Era, P. T. Reynolds, Fermi-Lat, Magic, Veritas
Physical Sciences Publications
We report on the γ-ray activity of the blazar Mrk 501 during the first 480 days of Fermi operation. We find that the average Large Area Telescope (LAT) γ-ray spectrum of Mrk 501 can be well described by a single power-law function with a photon index of 1.78 ± 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of two), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 ± 0.14, and the softest one is 2.51 ± 0.20. These unexpected spectral changes do …