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Register a new userVery-high energy observations of the Galactic center region by VERITAS in 2010-2012
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The VERITAS Collaboration
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The Galactic center is an interesting region for high-energy (0.1-100 GeV) and very-high-energy (E > 100 GeV) gamma-ray observations. Potential sources of GeV/TeV gamma-ray emission have been suggested, e.g., the accretion of matter onto the supermassive black hole, cosmic rays from a nearby supernova remnant (e.g. SgrA East), particle acceleration in a plerion, or the annihilation of dark matter particles. The Galactic center has been detected by EGRET and by Fermi/LAT in the MeV/GeV energy band. At TeV energies, the Galactic center was detected with moderate significance by the CANGAROO and Whipple 10 m telescopes and with high significance by H.E.S.S., MAGIC, and VERITAS. We present the results from three years of VERITAS observations conducted at large zenith angles resulting in a detection of the Galactic center on the level of 18 standard deviations at energies above ~2.5TeV. The energy spectrum is derived and is found to be compatible with hadronic, leptonic and hybrid emission models discussed in the literature. Future, more detailed measurements of the high-energy cutoff and better constraints on the high-energy flux variability will help to refine and/or disentangle the individual models.
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The galactic center (GC) has long been a region of interest for high-energy and very-high-energy observations. Many potential sources of GeV/TeV gamma-ray emission are located in the GC region, e.g. the accretion of matter onto the central black hole, cosmic rays from a nearby shell-type super nova remnant, or the annihilation of dark matter. The GC has been detected at MeV/GeV energies by EGRET and recently by Fermi/LAT. At TeV energies, the GC was detected at the level of 4 standard deviations with the Whipple 10m telescope and with one order of magnitude better sensitivity by H.E.S.S. and MAGIC. We present the results from 3 years of VERITAS GC observations conducted at large zenith angles. The results are compared to astrophysical models.
The Galactic Center has long been a region of interest for high-energy and very-high-energy observations. Many potential sources of GeV/TeV gamma-ray emission have been suggested, e.g., the accretion of matter onto the black hole, cosmic rays from a nearby supernova remnant, or the annihilation of dark matter particles. The Galactic Center has been detected at MeV/GeV energies by EGRET and recently by Fermi/LAT. At GeV/TeV energies, the Galactic Center was detected by different ground-based Cherenkov telescopes such as CANGAROO, Whipple 10m, H.E.S.S., and MAGIC. We present the results from 15 hrs of VERITAS observations conducted at large zenith angles, resulting in a >10 standard deviation detection and confirmation of the high-energy spectrum observed by H.E.S.S. The combined Fermi/VERITAS results are compared to astrophysical models.
Progress in the Imaging Atmospheric Cherenkov Technique has enabled first sensitive observations of the innermost few 100 pc of the Milky Way in Very High Energy (VHE; >100 GeV) gamma rays. Observations by the H.E.S.S. instrument deliver the at date most precise data on this peculiar region, and provide an interesting view onto the acceleration and propagation of energetic particles near the Galactic Centre. Besides two point-like sources -- one coincident with the supermassive black hole (SMBH) Sgr A* -- diffuse VHE emission has been discovered within a 1 deg region around the centre. The current VHE gamma-ray view of the region is reviewed, and possible counterparts of the gamma-ray sources and the origin of the diffuse emission are discussed.
The Galactic Center Ridge has been observed extensively in the past by both GeV and TeV instruments revealing a wealth of structure, including both a diffuse component, the point sources G0.9+0.1 (a composite supernova remnant) and SgrA* (believed to be associated with the super massive black hole located at the center of our galaxy). Previous observations (> 300 GeV) with the H.E.S.S. array have also detected an extended TeV component along the Galactic plane due to either diffuse emission or a host of unresolved point sources. Here we report on the VERITAS observations of the Galactic Center Ridge from 2010-2014 in the energy range above 2 TeV. From these observations we 1.) Provide improved measurements of the differential energy spectra for SgrA* in the multi-TeV regime, 2.) Provide a detection in the >2 TeV band of the composite SNR G0.9+0.1 and an improvement of its multi-TeV energy spectrum. 3.) Report on the detection of an extended component of emission along the Galactic plane by VERITAS. 4.) Report on the detection of VER J1746-289, a localized enhancement of TeV emission along the Galactic plane.
Due to its extraordinarily high concentration of known relativistic particle accelerators such as pulsar wind nebula, supernova remnants, dense molecular cloud regions, and the supermassive black hole (Sgr A*); the center of the Milky Way galaxy has long been an ideal target for high energy (HE, 0.1-100 GeV) and very high energy ( VHE, 50 GeV-50 TeV) gamma-ray emission. Indeed, detections of Sgr A* and other nearby regions of gamma-ray emission have been reported by EGRET and Fermi-LAT in the HE band, as well as CANGAROO, Whipple, HESS, VERITAS, and MAGIC in the VHE band. Here we report on the results of extended observations of the region with VERITAS between 2010-2014. Due to the visibility of the source for VERITAS in the Northern Hemisphere, these observations provide the most sensitive probe of gamma-ray emission above 2 TeV in one of the most complicated and interesting regions of our home galaxy.
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