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VERITAS Observations of LS I +61 303 in the Fermi Era |
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Conference Proceedings
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Written by Jamie Holder, for the VERITAS Collaboration
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Wednesday, 22 July 2009 |
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arXiv:0907.3921 The high-mass X-ray binary system LS I +61 303 is well known as a rare example of a variable Galactic GeV and TeV gamma-ray emitter. Despite years of study, many aspects of the system remain unclear; the nature of the compact object, the particle acceleration mechanisms and the gamma-ray emission and absorption processes can all be modelled in a variety of different scenarios. Here we report on a deep exposure of LS I +61 303 made with the VERITAS array during the 2008-2009 observing season. These are the first TeV observations made with contemporaneous coverage at lower energies by the LAT onboard Fermi, and as such provide a new set of constraints for system models. |
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Last Updated ( Friday, 31 July 2009 )
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A first joint M87 campaign in 2008 from radio to TeV gamma-rays |
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Conference Proceedings
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Written by R. M. Wagner et. al.
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Thursday, 09 July 2009 |
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arXiv:0907.1465 M87, the central galaxy of the Virgo cluster, is the first radio galaxy detected in the TeV regime. The structure of its jet, which is not pointing toward the line of sight, is spatially resolved in X-ray (by Chandra), in optical and in radio observations. Time correlation between the TeV flux and emission at other wavelengths provides a unique opportunity to localize the very high energy gamma-ray emission process occurring in AGN. For 10 years, M87 has been monitored in the TeV band by atmospheric Cherenkov telescopes. In 2008, the three main atmospheric Cherenkov telescope observatories (H.E.S.S., MAGIC and VERITAS) coordinated their observations in a joint campaign from January to May with a total observation time of approx. 120 hours. The campaign largely overlapped with an intensive VLBA project monitoring the core of M87 at 43 GHz every 5 days. In February, high TeV activities with rapid flares have been detected. Contemporaneously, M87 was observed with high spatial resolution instruments in X-rays (Chandra). We discuss the results of the joint observation campaign in 2008. |
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Observation of Extended Very High Energy Emission from the Supernova Remnant IC 443 with VERITAS |
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Evidence for Long-Term Gamma-Ray and X-Ray Variability from the Unidentified TeV Source HESS J0632+0 |
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Science Publications
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Written by V. A. Acciari et al
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Thursday, 28 May 2009 |
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The Astrophysical Journal Letters, Volume 698, Issue 2, pp. L94-L97 (2009). arxiv.org/0905.3139 HESS J0632+057 is one of only two unidentified very-high-energy gamma-ray sources which appear to be point-like within experimental resolution. It is possibly associated with the massive Be star MWC 148 and has been suggested to resemble known TeV binary systems like LS I +61 303 or LS 5039. HESS J0632+057 was observed by VERITAS for 31 hours in 2006, 2008 and 2009. During these observations, no significant signal in gamma rays with energies above 1 TeV was detected from the direction of HESS J0632+057. A flux upper limit corresponding to 1.1% of the flux of the Crab Nebula has been derived from the VERITAS data. The non-detection by VERITAS excludes with a probability of 99.993% that HESS J0632+057 is a steady gamma-ray emitter. Contemporaneous X-ray observations with Swift XRT reveal a factor of 1.8+-0.4 higher flux in the 1-10 keV range than earlier X-ray observations of HESS J0632+057. The variability in the gamma-ray and X-ray fluxes supports interpretation of the ob ject as a gamma-ray emitting binary. |
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