53 research outputs found
MITSuME--Multicolor Imaging Telescopes for Survey and Monstrous Explosions
Development of MITSuME is reported. Two 50-cm optical telescopes have been
built at Akeno in Yamanashi prefecture and at Okayama Astrophysical Observatory
(OAO) in Okayama prefecture. Three CCD cameras for simultaneous g'RcIc
photometry are to be mounted on each focal plane, covering a wide FOV of about
30" x 30". The limiting magnitude at V is fainter than 18. In addition to these
two optical telescopes, a 91-cm IR telescope with a 1 deg x 1 deg field of view
is being built at OAO, which performs photometry in YJHK bands. These robotic
telescopes can start the observation of counterparts of a GRB within a minute
from an alert. We aim to obtain photometric redshifts exceeding 10 with these
telescopes. The performance and the current construction status of the
telescopes are presented.Comment: 4 pages, 3 figures, 4th Workshop on Gamma-Ray Burst in the Afterglow
Era, Roma, October 18-22, 200
Spectral Lag Relations in GRB Pulses Detected with HETE-2
Using a pulse-fit method, we investigate the spectral lags between the
traditional gamma-ray band (50-400 keV) and the X-ray band (6-25 keV) for 8
GRBs with known redshifts (GRB 010921, GRB 020124, GRB 020127, GRB 021211, GRB
030528, GRB 040924, GRB 041006, GRB 050408) detected with the WXM and FREGATE
instruments aboard the HETE-2 satellite. We find several relations for the
individual GRB pulses between the spectral lag and other observables, such as
the luminosity, pulse duration, and peak energy (Epeak). The obtained results
are consistent with those for BATSE, indicating that the BATSE correlations are
still valid at lower energies (6-25 keV). Furthermore, we find that the photon
energy dependence for the spectral lags can reconcile the simple curvature
effect model. We discuss the implication of these results from various points
of view.Comment: 13 pages, 9 figures, accepted for the publication in PASJ (minor
corrections
AN5D: Automated Stencil Framework for High-Degree Temporal Blocking on GPUs
Stencil computation is one of the most widely-used compute patterns in high
performance computing applications. Spatial and temporal blocking have been
proposed to overcome the memory-bound nature of this type of computation by
moving memory pressure from external memory to on-chip memory on GPUs. However,
correctly implementing those optimizations while considering the complexity of
the architecture and memory hierarchy of GPUs to achieve high performance is
difficult. We propose AN5D, an automated stencil framework which is capable of
automatically transforming and optimizing stencil patterns in a given C source
code, and generating corresponding CUDA code. Parameter tuning in our framework
is guided by our performance model. Our novel optimization strategy reduces
shared memory and register pressure in comparison to existing implementations,
allowing performance scaling up to a temporal blocking degree of 10. We achieve
the highest performance reported so far for all evaluated stencil benchmarks on
the state-of-the-art Tesla V100 GPU
Prospects for GRB Science with the Fermi Large Area Telescope
The LAT instrument on the Fermi mission will reveal the rich spectral and
temporal gamma-ray burst phenomena in the > 100 MeV band. The synergy with
Fermi's GBM detectors will link these observations to those in the well
explored 10-1000 keV range; the addition of the > 100 MeV band observations
will resolve theoretical uncertainties about burst emission in both the prompt
and afterglow phases. Trigger algorithms will be applied to the LAT data both
onboard the spacecraft and on the ground. The sensitivity of these triggers
will differ because of the available computing resources onboard and on the
ground. Here we present the LAT's burst detection methodologies and the
instrument's GRB capabilities.Comment: Accepted by Ap
Environmental factors determining the distribution of highland plants at low-altitude algific talus sites
Algific talus is a micro-scale habitat type where highland plants (subalpine and alpine species) are found, disjunct from their typical range, in lowland forests. On algific talus, cold airflows from the interstices between talus fragments create a local microclimate colder than surrounding forests. Despite of the widely-known occurrence of unique vegetation on algific talus, critical environmental factors determining the distribution of highland species in this habitat type are unclear. In order to reveal the environmental factors enabling highland species to inhabit algific talus, we investigated the vegetation and environments of 26 algific talus sites and four reference (non-algific talus) sites in Hokkaido, northern Japan. Several algific talus sites were dominated by highland species, while some algific talus sites and all non-algific talus sites were dominated by lowland species. Community analysis based on detrended correspondence analysis (DCA) and canonical corresponding analysis (CCA) revealed that the algific talus sites dominated by highland species had lower ground temperature, more acidic soil, larger canopy openness, and less diverse vegetation than the sites dominated by lowland species. Highland plants might be maintained under conditions stressful for lowland plants, resulting in less competitive situation. Generalized linear models (GLM), used to evaluate the response of individual highland species to environmental factors, revealed that preferable environmental conditions for highland plants are highly species specific. These results indicate that the maintenance of diverse environments is crucial for the conservation of the unique vegetation and local populations of highland species in algific talus areas
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