2,865 research outputs found
Cylindrical shock model of the plasma pinch
Plasma pinch model representing imploding current sheet as impermeable cylindrical piston driving gasdynamic shock wav
Ground-Based Gamma-Ray Astronomy at Energies Above 10 TeV: Searching for Galactic PeV Cosmic-Ray Accelerators
The origin of Galactic CRs up the knee energy remains unanswered and provides
strong motivation for the study of gamma-ray sources at energies above 10 TeV.
We discuss recent results from ground-based gamma-ray Cherenkov imaging systems
at these energies as well as future observational efforts in this direction.
The exciting results of H.E.S.S. give clues as to the nature of Galactic CR
accelerators, and suggest that there is a population of Galactic gamma-ray
sources with emission extending beyond 10 TeV. A dedicated system of Cherenkov
imaging telescopes optimised for higher energies appears to be a promising way
to study the multi-TeV gamma-ray sky.Comment: Presented at the conference 'Physics At The End Of The Galactic
Cosmic Ray Spectrum' Aspen (April 2005) see
http://www.cosmic-ray.org/conf/index.html (8 pages, 6 figures
Experimental approaches for 100 TeV gamma-ray astronomy
The high energy end of gamma-ray source spectra might provide important clues
regarding the nature of the processes involved in gamma-ray emission. Several
galactic sources with hard emission spectra extending up to more than 30TeV
have already been reported. Measurements around 100TeV and above should be an
important goal for the next generation of high energy gamma-ray astronomy
experiments. Here we present several techniques providing the required exposure
(100 km^2.h). We focus our study on three Imaging Atmospheric Cherenkov
Technique (IACT) based approaches: low elevation observations, large field of
view telescopes, and large telescope arrays. We comment on the advantages and
disadvantages of each approach and report simulation based estimates of their
energy ranges and sensitivities.Comment: 3 pages 1 figure. Proceedings of TeV particle astrophysics 2,
Madison, August 2006.
http://www.icecube.wisc.edu/TeV/presentations/colin_poster.pd
Constraints on the cosmic ray diffusion coefficient in the W28 region from gamma-ray observations
GeV and TeV gamma rays have been detected from the supernova remnant W28 and
its surroundings. Such emission correlates quite well with the position of
dense and massive molecular clouds and thus it is often interpreted as the
result of hadronic cosmic ray interactions in the dense gas. Constraints on the
cosmic ray diffusion coefficient in the region can be obtained, under the
assumption that the cosmic rays responsible for the gamma ray emission have
been accelerated in the past at the supernova remnant shock, and subsequently
escaped in the surrounding medium. In this scenario, gamma ray observations can
be explained only if the diffusion coefficient in the region surrounding the
supernova remnant is significantly suppressed with respect to the average
galactic one.Comment: To appear in the proceedings of "Journ\'ees de la SF2A 2010"
Marseille 21-24 June 2010, 4 pages, 4 figure
The Monoceros very-high-energy gamma-ray source
The H.E.S.S. telescope array has observed the complex Monoceros Loop
SNR/Rosette Nebula region which contains unidentified high energy EGRET sources
and potential very-high-energy (VHE) gamma-ray source. We announce the
discovery of a new point-like VHE gamma-ray sources, HESS J0632+057. It is
located close to the rim of the Monoceros SNR and has no clear counterpart at
other wavelengths. Data from the NANTEN telescope have been used to investigate
hadronic interactions with nearby molecular clouds. We found no evidence for a
clear association. The VHE gamma-ray emission is possibly associated with the
lower energy gamma-ray source 3EG J0634+0521, a weak X-ray source 1RXS
J063258.3+054857 and the Be-star MWC 148.Comment: 4 pages, 4 figures, Contribution to the 30th ICRC, Merida Mexico,
July 200
ISM gas studies towards the TeV PWN HESS J1825-137 and northern region
HESS J1825-137 is a pulsar wind nebula (PWN) whose TeV emission extends
across ~1 deg. Its large asymmetric shape indicates that its progenitor
supernova interacted with a molecular cloud located in the north of the PWN as
detected by previous CO Galactic survey (e.g Lemiere, Terrier &
Djannati-Ata\"i 2006). Here we provide a detailed picture of the ISM towards
the region north of HESS J1825-137, with the analysis of the dense molecular
gas from our 7mm and 12mm Mopra survey and the more diffuse molecular gas from
the Nanten CO(1-0) and GRS CO(1-0) surveys. Our focus is the possible
association between HESS J1825-137 and the unidentified TeV source to the
north, HESS J1826-130. We report several dense molecular regions whose
kinematic distance matched the dispersion measured distance of the pulsar.
Among them, the dense molecular gas located at (RA,
Dec)=(18.421h,-13.282) shows enhanced turbulence and we suggest that
the velocity structure in this region may be explained by a cloud-cloud
collision scenario. Furthermore, the presence of a H rim may be the
first evidence of the progenitor SNR of the pulsar PSR J1826-1334 as the
distance between the H rim and the TeV source matched with the
predicted SNR radius R~120 pc. From our ISM study, we identify a
few plausible origins of the HESS J1826-130 emission, including the progenitor
SNR of PSR J1826-1334 and the PWN G018.5-0.4 powered by PSR J1826-1256. A
deeper TeV study however, is required to fully identify the origin of this
mysterious TeV source.Comment: 19 figures, 27 pages, accepted by MNRA
Grassland Bird Monitoring at Agate Fossil Beds National Monument, Nebraska and Tallgrass Prairie National Preserve, Kansas
During the breeding seasons of 2001 through 2003, a total of 517 variable circular plots were surveyed for birds and assessed for habitat composition at Agate Fossil Beds National Monument, Nebraska and Tallgrass Prairie National Preserve, Kansas. Systematic 400 x 400 meter grids, originating from random start points, were used to locate 40 permanent variable circular plots in upland habitat at Agate Fossil Beds National Monument and 242 at Tallgrass Prairie National Preserve. An additional 14 permanent plots were established in the less common but important riparian habitat at Agate Fossil Beds National Monument, and 18 plots were added in riparian areas at Tall grass Prairie National Preserve. Variable circular plots in riparian habitat were spaced at 250 meter intervals throughout each area
TenTen: A New Array of Multi-TeV Imaging Cherenkov Telescopes
The exciting results from H.E.S.S. point to a new population of gamma-ray
sources at energies E > 10 TeV, paving the way for future studies and new
discoveries in the multi-TeV energy range. Connected with these energies is the
search for sources of PeV cosmic-rays (CRs) and the study of multi-TeV
gamma-ray production in a growing number of astrophysical environments. TenTen
is a proposed stereoscopic array (with a suggested site in Australia) of
modest-sized (10 to 30m^2) Cherenkov imaging telescopes with a wide field of
view (8 to 10deg diameter) optimised for the E~10 to 100 TeV range. TenTen will
achieve an effective area of ~10 km^2 at energies above 10 TeV. We outline here
the motivation for TenTen and summarise key performance parameters.Comment: 4 pages, 2 figures, proceedings of the 30th ICRC, Merida, Mexico,
200
The H.E.S.S. multi-messenger program
Based on fundamental particle physics processes like the production and
subsequent decay of pions in interactions of high-energy particles, close
connections exist between the acceleration sites of high-energy cosmic rays and
the emission of high-energy gamma rays and high-energy neutrinos. In most cases
these connections provide both spatial and temporal correlations of the
different emitted particles. The combination of the complementary information
provided by these messengers allows to lift ambiguities in the interpretation
of the data and enables novel and highly sensitive analyses. In this
contribution the H.E.S.S. multi-messenger program is introduced and described.
The current core of this newly installed program is the combination of
high-energy neutrinos and high-energy gamma rays. The search for gamma-ray
emission following gravitational wave triggers is also discussed. Furthermore,
the existing program for following triggers in the electromagnetic regime was
extended by the search for gamma-ray emission from Fast Radio Bursts (FRBs). An
overview over current and planned analyses is given and recent results are
presented.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherland
Simulation Study of TenTen: A new Multi-TeV IACT array
TenTen is a proposed array of Imaging Atmospheric Cherenkov Telescopes (IACT)
optimized for the gamma ray energy regime of 10 TeV to 100 TeV, but with a
threshold of ~1 to a few TeV. It will offer a collecting area of 10 km2 above
energies of 10 TeV. In the initial phase, a cell of 3 to 5 modest-sized
telescopes, each with 10-30 m2 mirror area, is suggested for an Australian
site. A possible expansion of the array could comprise many such cells. Here we
present work on configuration and technical issues from our simulation studies
of the array. Working topics include array layout, telescope size and optics,
camera field of view, telescope trigger system, electronics, and site surveys.Comment: 4 pages, 7 figures, submitted to Proceedings of the ICRC 2007, pdf
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