331 research outputs found
Earliest detection of the optical afterglow of GRB 030329 and its variability
We report the earliest detection of an extremely bright optical afterglow of
the gamma-ray burst (GRB) 030329 using a 30cm-telescope at Tokyo Institute of
Technology (Tokyo, JAPAN). Our observation started 67 minutes after the burst,
and continued for succeeding two nights until the afterglow faded below the
sensitivity limit of the telescope (approximately 18 mag). Combining our data
with those reported in GCN Circulars, we find that the early afterglow light
curve of the first half day is described by a broken power-law (t^{- alpha})
function with indices alpha_{1} = 0.88 +/- 0.01 (0.047 < t < t_{b1} days),
alpha_{2} = 1.18 +/- 0.01 (t_{b1} < t < t_{b2} days), and alpha_{3} = 1.81 +/-
0.04 (t_{b2} < t < 1.2 days), where t_{b1} ~ 0.26 days and t_{b2} ~ 0.54 days,
respectively. The change of the power-law index at the first break at t ~ 0.26
days is consistent with that expected from a ``cooling-break'' when the cooling
frequency crossed the optical band. If the interpretation is correct, the decay
index before the cooling-break implies a uniform ISM environment.Comment: 13 pages, 1 table and 2 figures. Accepted to the Astrophysical
Journal Letter
Discovery of an unidentified Fermi object as a black widow-like millisecond pulsar
The Fermi Gamma-ray Space Telescope has revolutionized our knowledge of the
gamma-ray pulsar population, leading to the discovery of almost 100 gamma-ray
pulsars and dozens of gamma-ray millisecond pulsars (MSPs). Although the
outer-gap model predicts different sites of emission for the radio and
gamma-ray pulsars, until now all of the known gamma-ray MSPs have been visible
in the radio. Here we report the discovery of a "radio-quiet" gamma-ray
emitting MSP candidate by using Fermi, Chandra, Swift, and optical
observations. The X-ray and gamma-ray properties of the source are consistent
with known gamma-ray pulsars. We also found a 4.63-hr orbital period in optical
and X-ray data. We suggest that the source is a black widow-like MSP with a
~0.1 solar-mass late-type companion star. Based on the profile of the optical
and X-ray light-curves, the companion star is believed to be heated by the
pulsar while the X-ray emissions originate from pulsar magnetosphere and/or
from intra-binary shock. No radio detection of the source has been reported yet
and although no gamma-ray/radio pulsation has been found, we estimated that the
spin period of the MSP is ~3-5 ms based on the inferred gamma-ray luminosity.Comment: 6 pages, 2 figures; accepted for publication in ApJ
Development of Operational Method for Reducing Adsorbed Gases on the Surface of Carbon Sheet Pump
Surface Analysis of Carbon Samples Exposed to GAMMA 10 Plasmas by the Use of the Monte Carlo Simulation
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