268 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
Chandra Observation of the Interaction between the Hot Plasma Nebula RCW89 and the Pulsar Jet of PSR B1509-58
We present a Chandra observation of the H II region RCW89. The nebula lies on
10' north from the central pulsar PSR B1509-58, and it has been suggested that
the nebula is irradiated by the pulsar jet. We performed a spectral analysis of
the seven brightest emitting regions aligned in a ``horse-shoe'' shape, and
found that the temperature of the knots increases along the ``horse-shoe'' in
the clockwise direction, while, in contrast, the ionization parameter
decreases. This strongly supports a picture of energy transfer via the
precessing pulsar jet. We examined the energy budget assuming that RCW89 is
powered by the pulsar jet, and confirmed that the pulsar rotational energy loss
is sufficient to drive the nebula. The rate of energy injection into RCW89 by
the jet was estimated from the synchrotron radiation flux. We obtained a
heating time-scale of 1400 yr, which is consistent with the pulsar
characteristic age of 1700 yr. To explain the temperature gradient, we discuss
the cooling process for plasma clouds in RCW89. We argue that the plasma clouds
can be cooled down by the adiabatic expansion within 70 yr, and form the
temperature gradient reflecting the sequential heating by the precessing pulsar
jet. We also determined the velocities of the individual plasma clouds by
spectral fitting. The plasma clouds in RCW89 are moving away at 240 ~ 860 km/s,
which constrains the inclination angle of the pulsar spin axis i > 50 degree
and the expanding velocity of the shell as v > 1100 km/s.Comment: 15 pages, 8 figures, accepted in Ap
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
Functional distinctions associated with the diversity of sex steroid hormone receptors ESR and AR
This is the author accepted manuscript. The final version is availablefrom Elsevier via the DOI in this recordSex steroid hormones including estrogens and androgens play fundamental roles in regulating reproductive activities and they act through estrogen and androgen receptors (ESR and AR). These steroid receptors have evolved from a common ancestor in association with several gene duplications. In most vertebrates, this has resulted in two ESR subtypes (ESR1 and ESR2) and one AR, whereas in teleost fish there are at least three ESRs (ESR1, ESR2a and ESR2b) and two ARs (ARα and ARβ) due to a lineage-specific whole genome duplication. Functional distinctions have been suggested among these receptors, but to date their roles have only been characterized in a limited number of species. Sexual differentiation and the development of reproductive organs are indispensable for all animal species and in vertebrates these events depend on the action of sex steroid hormones. Here we review the recent progress in understanding of the functions of the ESRs and ARs in the development and expression of sexually dimorphic characteristics associated with steroid hormone signaling in vertebrates, with representative fish, amphibians, reptiles, birds and mammals.Japan Society for the Promotion of ScienceMinistry of the Environment, JapanDepartment for Environment, Food and Rural Affairs (Defra), UKNational Institute for Basic BiologyKyushu Universit
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