3,921 research outputs found
Astrophysics with High Energy Gamma Rays
Recent results, the present status and the perspectives of high energy
gamma-ray astronomy are described. Since the satellite observations by the
Compton Gamma Ray Observatory and its precursor missions have been reviewed
extensively, emphasis is on the results from the ground-based gamma-ray
telescopes. They concern the physics of Pulsar Nebulae, Supernova Remnants in
their assumed role as the Galactic sources of Cosmic Rays, Jets from Active
Galactic Nuclei, and the Extragalactic Background radiation field due to stars
and dust in galaxies. Since the gamma-ray emission is nonthermal, this kind of
astronomy deals with the pervasive high-energy nonequilibrium states in the
Universe. The present build-up of larger and more sensitive instruments, both
on the ground and in space, gives fascinating prospects also for observational
cosmology and astroparticle physics. Through realistically possible further
observational developments at high mountain altitudes a rapid extension of the
field is to be expected.Comment: 23 pages, 11 figures. To appear in "Astronomy, Cosmology and
Fundamental Physics", ed. P. A. Shaver, L. Di Lella, and A. Gimenez, Proc.
ESA-CERN-ESO Symposium, Garching, March 2002. Springer-Verlag, Berlin,
Heidelberg, series "ESO Astrophysics Symposia
TeV Gamma-ray Astronomy: A Summary
The field of TeV gamma-ray astronomy has produced many exciting results over
the last decade. Both the source catalogue, and the range of astrophysical
questions which can be addressed, continue to expand. This article presents a
topical review of the field, with a focus on the observational results of the
imaging atmospheric Cherenkov telescope arrays. The results encompass pulsars
and their nebulae, supernova remnants, gamma-ray binary systems, star forming
regions and starburst and active galaxies.Comment: 19 pages. Astroparticle Physics, in press. See published article for
higher resolution figures. Cite as: J. Holder, TeV gamma-ray astronomy: A
summary, Astropart. Phys. (2012),
http://dx.doi.org/10.1016/j.astropartphys.2012.02.01
NELIOTA: The wide-field, high-cadence lunar monitoring system at the prime focus of the Kryoneri telescope
We present the technical specifications and first results of the ESA-funded,
lunar monitoring project "NELIOTA" (NEO Lunar Impacts and Optical TrAnsients)
at the National Observatory of Athens, which aims to determine the
size-frequency distribution of small Near-Earth Objects (NEOs) via detection of
impact flashes on the surface of the Moon. For the purposes of this project a
twin camera instrument was specially designed and installed at the 1.2 m
Kryoneri telescope utilizing the fast-frame capabilities of scientific
Complementary Metal-Oxide Semiconductor detectors (sCMOS). The system provides
a wide field-of-view (17.0' 14.4') and simultaneous observations in
two photometric bands (R and I), reaching limiting magnitudes of 18.7 mag in 10
sec in both bands at a 2.5 signal-to-noise level. This makes it a unique
instrument that can be used for the detection of NEO impacts on the Moon, as
well as for any astronomy projects that demand high-cadence multicolor
observations. The wide field-of-view ensures that a large portion of the Moon
is observed, while the simultaneous, high-cadence, monitoring in two
photometric bands makes possible, for the first time, the determination of the
temperatures of the impacts on the Moon's surface and the validation of the
impact flashes from a single site. Considering the varying background level on
the Moon's surface we demonstrate that the NELIOTA system can detect NEO impact
flashes at a 2.5 signal-to-noise level of ~12.4 mag in the I-band and R-band
for observations made at low lunar phases ~0.1. We report 31 NEO impact flashes
detected during the first year of the NELIOTA campaign. The faintest flash was
at 11.24 mag in the R-band (about two magnitudes fainter than ever observed
before) at lunar phase 0.32. Our observations suggest a detection rate of events .Comment: Accepted for publication in A&
The ASTRO-H X-ray Observatory
The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly
successful X-ray missions initiated by the Institute of Space and Astronautical
Science (ISAS). ASTRO-H will investigate the physics of the high-energy
universe via a suite of four instruments, covering a very wide energy range,
from 0.3 keV to 600 keV. These instruments include a high-resolution,
high-throughput spectrometer sensitive over 0.3-2 keV with high spectral
resolution of Delta E < 7 eV, enabled by a micro-calorimeter array located in
the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers
covering 5-80 keV, located in the focal plane of multilayer-coated, focusing
hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4-12
keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and
a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the
40-600 keV band. The simultaneous broad bandpass, coupled with high spectral
resolution, will enable the pursuit of a wide variety of important science
themes.Comment: 22 pages, 17 figures, Proceedings of the SPIE Astronomical
Instrumentation "Space Telescopes and Instrumentation 2012: Ultraviolet to
Gamma Ray
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