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A luminous and isolated gamma-ray flare from the blazar b2 1215+30 (2018)

Abeysekara, A. U.; Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Buchovecky, M.; B...

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A search for brief optical flashes associated with the seti target kic 8462852 (2018)

Abeysekara, A. U.; Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Buchovecky, M.; B...

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A search for enhanced very high energy gamma-ray emission from the 2013 march crab nebula flare (2018)

Aliu, E.; Archambault, S.; Aune, T.; Benbow, W.; Berger, K.; Bird, R.; Bouvier, A.; Buc...

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A search for spectral hysteresis and energy-dependent time lags from x-ray and tev gamma-ray observations of mrk 421 (2018)

Abeysekara, A. U.; Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Buchovecky, M.; B...

A search for spectral hysteresis and energy-dependent time lags from x-ray and tev gamma-ray observations of mrk 421 (2018)

Abeysekara, A. U.; Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Cardenzana, J. V; Cerruti, M.; Chen, X.; Ciupik, L.; Connolly, M. P.; Cui, W.; Eisch, J. D.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Flinders, A.

Abstract:

Blazars are variable emitters across all wavelengths over a wide range of timescales, from months down to minutes. It is therefore essential to observe blazars simultaneously at different wavelengths, especially in the X-ray and gamma-ray bands, where the broadband spectral energy distributions usually peak. In this work, we report on three &quot; target-of-opportunity&quot; observations of Mrk 421, one of the brightest TeV blazars, triggered by a strong flaring event at TeV energies in 2014. These observations feature long, continuous, and simultaneous exposures with XMM-Newton (covering the X-ray and optical/ultraviolet bands) and VERITAS (covering the TeV gamma-ray band), along with contemporaneous observations from other gamma-ray facilities (MAGIC and Fermi-Large Area Telescope) and a number of radio and optical facilities. Although neither rapid flares nor significant X-ray/TeV correlation are detected, these observations reveal subtle changes in the X-ray spec...

http://hdl.handle.net/10379/10074

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A search for very high energy gamma rays from the missing link binary pulsar j1023+0038 with veritas (2018)

Aliu, E.; Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Biteau, J.; Buchovecky, M....

A search for very high energy gamma rays from the missing link binary pulsar j1023+0038 with veritas (2018)

Aliu, E.; Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Biteau, J.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cardenzana, J. V; Cerruti, M.; Chen, X.; Ciupik, L.; Connolly, M. P.; Cui, W.; Dickinson, H. J.; Eisch, J. D.; Falcone, A.; Feng, Q.

Abstract:

The binary millisecond radio pulsar PSR J1023+0038 exhibits many characteristics similar to the gamma-ray binary system PSR B1259-63/LS 2883, making it an ideal candidate for the study of high-energy nonthermal emission. It has been the subject of multiwavelength campaigns following the disappearance of the pulsed radio emission in 2013 June, which revealed the appearance of an accretion disk around the neutron star. We present the results of very high energy (VHE) gamma-ray observations carried out by the Very Energetic Radiation Imaging Telescope Array System before and after this change of state. Searches for steady and pulsed emission of both data sets yield no significant gamma-ray signal above 100 GeV, and upper limits are given for both a steady and pulsed gamma-ray flux. These upper limits are used to constrain the magnetic field strength in the shock region of the PSR J1023+0038 system. Assuming that VHE gamma rays are produced via an inverse Compton mechanism in the shock ...

http://hdl.handle.net/10379/10195

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A strong limit on the very-high-energy emission from grb 150323a (2018)

Abeysekara, A. U.; Archer, A.; Benbow, W.; Bird, R.; Brose, R.; Buchovecky, M.; Bugaev,...

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Constraints on cosmic rays, magnetic fields, and dark matter from gamma-ray observations of the coma cluster of galaxies with veritas andfermi (2018)

Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bouvier, A.; Buckley, J. H.; Bugaev, V.;...

Constraints on cosmic rays, magnetic fields, and dark matter from gamma-ray observations of the coma cluster of galaxies with veritas andfermi (2018)

Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bouvier, A.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cannon, A.; Cesarini, A.; Ciupik, L.; Collins-Hughes, E.; Connolly, M. P.; Cui, W.; Dickherber, R.; Dumm, J.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.

Abstract:

Observations of radio halos and relics in galaxy clusters indicate efficient electron acceleration. Protons should likewise be accelerated and, on account of weak energy losses, can accumulate, suggesting that clusters may also be sources of very high energy (VHE; E &gt; 100 GeV) gamma-ray emission. We report here on VHE gamma-ray observations of the Coma galaxy cluster with the VERITAS array of imaging Cerenkov telescopes, with complementing Fermi Large Area Telescope observations at GeV energies. No significant gamma-ray emission from the Coma Cluster was detected. Integral flux upper limits at the 99% confidence level were measured to be on the order of (2-5) x 10(-8) photonsm(-2) s(-1) (VERITAS, &gt;220 GeV) and similar to 2 x 10(-6) photonsm(-2) s(-1) (Fermi, 1-3GeV), respectively. We use the gamma-ray upper limits to constrain cosmic rays (CRs) and magnetic fields in Coma. Using an analytical approach, the CR-to-thermal pressure ratio is constrained to be &...

http://hdl.handle.net/10379/10292

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Dark matter constraints from a joint analysis of dwarf spheroidal galaxy observations with veritas (2018)

Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Bourbeau, E.; Brantseg, T.; Buchovec...

Dark matter constraints from a joint analysis of dwarf spheroidal galaxy observations with veritas (2018)

Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Bourbeau, E.; Brantseg, T.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cerruti, M.; Christiansen, J. L.; Connolly, M. P.; Cui, W.; Daniel, M. K.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortson, L.; Furniss, A.

Abstract:

We present constraints on the annihilation cross section of weakly interacting massive particles dark matter based on the joint statistical analysis of four dwarf galaxies with VERITAS. These results are derived from an optimized photon weighting statistical technique that improves on standard imaging atmospheric Cherenkov telescope (IACT) analyses by utilizing the spectral and spatial properties of individual photon events. We report on the results of similar to 230 hours of observations of five dwarf galaxies and the joint statistical analysis of four of the dwarf galaxies. We find no evidence of gamma-ray emission from any individual dwarf nor in the joint analysis. The derived upper limit on the dark matter annihilation cross section from the joint analysis is 1.35 x 10(-23) cm(3) s(-1) at 1 TeV for the bottom quark (b (b) over bar) final state, 2.85 x 10(-24) cm(3) s(-1) at 1 TeV for the tau lepton (tau+tau(-)) final state and 1.32 x 10-25 cm(3) s(-1) at 1 TeV for the gauge bos...

http://hdl.handle.net/10379/10281

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Discovery of a new tev gamma-ray source: ver j0521+211 (2018)

Archambault, S.; Arlen, T.; Aune, T.; Behera, B.; Beilicke, M.; Benbow, W.; Bird, R.; B...

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Discovery of very-high-energy emission from rgb j2243+203 and derivation of its redshift upper limit (2018)

Abeysekara, A. U.; Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Brose, R.; Buchov...

Discovery of very-high-energy emission from rgb j2243+203 and derivation of its redshift upper limit (2018)

Abeysekara, A. U.; Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Brose, R.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Cerruti, M.; Connolly, M. P.; Cui, W.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Griffin, S.

Abstract:

Very-high-energy (VHE; &gt; 100 GeV) gamma-ray emission from the blazar RGB J2243+203 was discovered with the VERITAS Cherenkov telescope array, during the period between 2014 December 21 and 24. The VERITAS energy spectrum from this source can be fitted by a power law with a photon index of 4.6 +/- 0.5, and a flux normalization at 0.15 TeV of (6.3 +/- 1.1) x 10(-10) cm(-2) s(-1) TeV-1. The integrated Fermi-LAT flux from 1 to 100 GeV during the VERITAS detection is (4.1 +/- 0.8) x 10(-8) cm(-2) s(-1), which is an order of magnitude larger than the four-year-averaged flux in the same energy range reported in the 3FGL catalog, (4.0 +/- 0.1 x 10(-9) cm(-2) s(-1)). The detection with VERITAS triggered observations in the X-ray band with the Swift-XRT. However, due to scheduling constraints Swift-XRT observations were performed 67 hr after the VERITAS detection, rather than simultaneously with the VERITAS observations. The observed X-ray energy spectrum between 2 and 10 keV can b...

http://hdl.handle.net/10379/10072

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Gamma-ray observations of tycho’s supernova remnant with veritas andfermi (2018)

Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Bourbeau, E.; Buchovecky, M.; Buckle...

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Gamma-ray observations under bright moonlight with veritas (2018)

Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Bourbeau, E.; Bouvier, A.; Buchoveck...

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Long term observations of b2 1215+30 with veritas (2018)

Aliu, E.; Archambault, S.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bird, R.; Bou...

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Multiwavelength observations of the blazar bl lacertae: a new fast tev gamma-ray flare (2018)

Abeysekara, A. U.; Benbow, W.; Bird, R.; Brantseg, T.; Brose, R.; Buchovecky, M.; Buckl...

Multiwavelength observations of the blazar bl lacertae: a new fast tev gamma-ray flare (2018)

Abeysekara, A. U.; Benbow, W.; Bird, R.; Brantseg, T.; Brose, R.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Connolly, M. P.; Cui, W.; Daniel, M. K.; Falcone, A.; Feng, Q.; Finley, J. P.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Gunawardhana, I.; Hütten, M.; Hanna, D.

Abstract:

Combined with measurements made by very-long-baseline interferometry, the observations of fast TeV gamma-ray flares probe the structure and emission mechanism of blazar jets. However, only a handful of such flares have been detected to date, and only within the last few years have these flares been observed from lower-frequency-peaked BL. Lac objects and flat-spectrum radio quasars. We report on a fast TeV gamma-ray flare from the blazar BL. Lacertae observed by the Very Energetic Radiation Imaging Telescope Array System (VERITAS). with a rise time of similar to 2.3 hr and a decay time of similar to 36 min. The peak flux above 200 GeV is (4.2 +/- 0.6) x 10(-6) photon m(-2) s(-1) measured with a 4-minute-binned light curve, corresponding to similar to 180% of the flux that is observed from the Crab Nebula above the same energy threshold. Variability contemporaneous with the TeV gamma-ray flare was observed in GeV gamma-ray, X-ray, and optical flux, as well as in optical and radio pol...

http://hdl.handle.net/10379/10078

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Multiwavelength observations of the previously unidentified blazar rx j0648.7+1516 (2018)

Aliu, E.; Aune, T.; Beilicke, M.; Benbow, W.; Böttcher, M.; Bouvier, A.; Bradbury, S. M...

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Multiwavelength observations of the tev binary ls i +61° 303 with veritas,fermi-lat, andswift/xrt during a tev outburst (2018)

Aliu, E.; Archambault, S.; Behera, B.; Berger, K.; Beilicke, M.; Benbow, W.; Bird, R.; ...

Multiwavelength observations of the tev binary ls i +61° 303 with veritas,fermi-lat, andswift/xrt during a tev outburst (2018)

Aliu, E.; Archambault, S.; Behera, B.; Berger, K.; Beilicke, M.; Benbow, W.; Bird, R.; Bouvier, A.; Bugaev, V.; Cerruti, M.; Chen, X.; Ciupik, L.; Connolly, M. P.; Cui, W.; Dumm, J.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Fortin, P.

Abstract:

We present the results of a multiwavelength observational campaign on the TeV binary system LS I +61 degrees 303 with the VERITAS telescope array (&gt;200 GeV), Fermi-LAT (0.3-300 GeV), and Swift/XRT (2-10 keV). The data were taken from 2011 December through 2012 January and show a strong detection in all three wavebands. During this period VERITAS obtained 24.9 hr of quality selected livetime data in which LS I +61 degrees 303 was detected at a statistical significance of 11.9 sigma. These TeV observations show evidence for nightly variability in the TeV regime at a post-trial significance of 3.6 sigma. The combination of the simultaneously obtained TeV and X-ray fluxes do not demonstrate any evidence for a correlation between emission in the two bands. For the first time since the launch of the Fermi satellite in 2008, this TeV detection allows the construction of a detailed MeV-TeV spectral energy distribution from LS I +61 degrees 303. This spectrum shows a distinct cuto...

http://hdl.handle.net/10379/10210

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Rapid tev gamma-ray flaring of bl lacertae (2018)

Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bouvier, A.; Buckley, J. H.; Bugaev, V.;...

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Test of models of the cosmic infrared background with multiwavelength observations of the blazar 1es 1218+30.4 in 2009 (2018)

Archambault, S.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bird, R.; Böttcher, M.;...

Test of models of the cosmic infrared background with multiwavelength observations of the blazar 1es 1218+30.4 in 2009 (2018)

Archambault, S.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bird, R.; Böttcher, M.; Bouvier, A.; Buckley, J. H.; Bugaev, V.; Ciupik, L.; Collins-Hughes, E.; Connolly, M. P.; Cui, W.; Dickherber, R.; Dumm, J.; Errando, M.; Falcone, A.; Federici, S.; Feng, Q.

Abstract:

We present the results of a multi-wavelength campaign targeting the blazar 1ES 1218+30.4 with observations with the 1.3 m McGraw-Hill optical telescope, the Rossi X-ray Timing Explorer (RXTE), the Fermi Gamma-Ray Space Telescope, and the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The RXTE and VERITAS observations were spread over a 13 day period and revealed clear evidence for flux variability, and a strong X-ray and gamma-ray flare on 2009 February 26 (MJD 54888). The campaign delivered a well-sampled broadband energy spectrum with simultaneous RXTE and VERITAS very high energy (VHE, &gt; 100 GeV) observations, as well as contemporaneous optical and Fermi observations. The 1ES 1218+30.4 broadband energy spectrum-the first with simultaneous X-ray and VHE gamma-ray energy spectra-is of particular interest as the source is located at a high cosmological redshift for a VHE source (z = 0.182), leading to strong absorption of VHE gamma rays by photons from...

http://hdl.handle.net/10379/10285

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Tev gamma-ray observations of the galactic center ridge by veritas (2018)

Archer, A.; Benbow, W.; Bird, R.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Byrum, K....

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Upper limits from five years of blazar observations with the veritas cherenkov telescopes (2018)

Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Biteau, J.; Buchovecky, M.; Buckley,...

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Veritas observations of the bl lac object txs 0506+056 (2018)

Abeysekara, A. U.; Archer, A.; Benbow, W.; Bird, R.; Brill, A.; Brose, R.; Buckley, J. ...

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Veritas observations of the microquasar cygnus x-3 (2018)

Archambault, S.; Beilicke, M.; Benbow, W.; Berger, K.; Bird, R.; Bouvier, A.; Buckley, ...

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Very high energy observations of the binaries v 404 cyg and 4u 0115+634 during giant x-ray outbursts (2018)

Archer, A.; Benbow, W.; Bird, R.; Bourbeau, E.; Buchovecky, M.; Buckley, J. H.; Bugaev,...

Very high energy observations of the binaries v 404 cyg and 4u 0115+634 during giant x-ray outbursts (2018)

Archer, A.; Benbow, W.; Bird, R.; Bourbeau, E.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cerruti, M.; Connolly, M. P.; Cui, W.; Errando, M.; Falcone, A.; Feng, Q.; Fernandez-Alonso, M.; Finley, J. P.; Fleischhack, H.; Flinders, A.; Fortson, L.; Furniss, A.

Abstract:

Transient X-ray binaries produce major outbursts in which the X-ray flux can increase over the quiescent level by factors as large as 10(7). The low-mass X-ray binary V 404 Cyg and the high-mass system 4U 0115+634 underwent such major outbursts in 2015 June and October, respectively. We present here observations at energies above hundreds of GeV with the VERITAS observatory taken during some of the brightest X-ray activity ever observed from these systems. No gamma-ray emission has been detected by VERITAS in 2.5 hr of observations of the microquasar V 404 Cyg from 2015, June 20-21. The upper flux limits derived from these observations on the gamma-ray flux above 200 GeV of F &lt; 4.4 x 10(-12) cm(-2) s(-1) correspond to a tiny fraction (about 10(-6)) of the Eddington luminosity of the system, in stark contrast to that seen in the X-ray band. No gamma-rays have been detected during observations of 4U 0115+634 in the period of major X-ray activity in 2015 October. The flux up...

http://hdl.handle.net/10379/10289