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Full-Text Articles in Physical Sciences and Mathematics
The June 2008 Flare Of Markarian 421 From Optical To Tev Energies, P. T. Reynolds, Et Al
The June 2008 Flare Of Markarian 421 From Optical To Tev Energies, P. T. Reynolds, Et Al
Physical Sciences Publications
We present optical, X-ray, high-energy (30 GeV) and very high energy (100 GeV; VHE) observations of the high-frequency peaked blazar Mrk 421 taken between 2008 May 24 and June 23. A high-energy γ-ray signal was detected by AGILE with between June 9 and 15, with F(E>100 MeV) = 42+14 –12 × 10–8 photons cm–2 s–1. This flaring state is brighter than the average flux observed by EGRET by a factor of ~3, but still consistent with the highest EGRET flux. In hard X-rays (20-60 keV) SuperAGILE resolved a five-day flare (June 9-15) peaking at ~55 mCrab. SuperAGILE, …
Discovery Of Very High-Energy Gamma-Ray Radiation From The Bl Lac 1es 0806+524, P. T. Reynolds, Et Al
Discovery Of Very High-Energy Gamma-Ray Radiation From The Bl Lac 1es 0806+524, P. T. Reynolds, Et Al
Physical Sciences Publications
The high-frequency-peaked BL Lacertae object 1ES 0806+524, at redshift z = 0.138, was observed in the very high energy (VHE) gamma-ray regime by VERITAS between 2006 November and 2008 April. These data encompass the two- and three-telescope commissioning phases, as well as observations with the full four-telescope array. 1ES 0806+524 is detected with a statistical significance of 6.3 standard deviations from 245 excess events. Little or no measurable variability on monthly timescales is found. The photon spectrum for the period 2007 November to 2008 April can be characterized by a power law with photon index 3.6 ± 1.0stat ± 0.3sys …
Veritas Discovery Of > 200 Gev Gamma-Ray Emission From The Intermediate-Frequency-Peaked Bl Lacertae Object W Comae, P. T. Reynolds, Et Al
Veritas Discovery Of > 200 Gev Gamma-Ray Emission From The Intermediate-Frequency-Peaked Bl Lacertae Object W Comae, P. T. Reynolds, Et Al
Physical Sciences Publications
We report the detection of very high energy γ-ray emission from the intermediate-frequency-peaked BL Lacertae object W Comae (z = 0.102) by VERITAS. The source was observed between 2008 January and April. A strong outburst of γ-ray emission was measured in the middle of March, lasting for only 4 days. The energy spectrum measured during the two highest flare nights is fit by a power law and is found to be very steep, with a differential photon spectral index of Γ = 3.81 ± 0.35stat± 0.34syst. The integral photon flux above 200 GeV during those two nights corresponds to …
Observation Of Gamma-Ray Emission From The Galaxy M87 Above 250 Gev With Veritas, P. T. Reynolds, Et. Al.
Observation Of Gamma-Ray Emission From The Galaxy M87 Above 250 Gev With Veritas, P. T. Reynolds, Et. Al.
Physical Sciences Publications
The multiwavelength observation of the nearby radio galaxy M87 provides a unique opportunity to study in detail processes occurring in active galactic nuclei from radio waves to TeV γ-rays. Here we report the detection of γ-ray emission above 250 GeV from M87 in spring 2007 with the VERITAS atmospheric Cerenkov telescope array and discuss its correlation with the X-ray emission. The γ-ray emission is measured to be pointlike with an intrinsic source radius less than 4.5'. The differential energy spectrum is fitted well by a power-law function: dΦ/dE = (7.4 ± 1.3stat ± 1.5sys)(E/TeV)(− 2.31 ± 0.17stat ± 0.2sys) 10−9 …