1,782 research outputs found
Spectropolarimetric Study on Circumstellar Structure of Microquasar LS I +61deg 303
We present optical linear spectropolarimetry of the microquasar LS I
+61 303. The continuum emission is mildly polarized (up to 1.3 %) and
shows almost no temporal change. We find a distinct change of polarization
across the H emission line, indicating the existence of polarization
component intrinsic to the microquasar. We estimate the interstellar
polarization (ISP) component from polarization of the H line and derive
the intrinsic polarization component. The wavelength dependence of the
intrinsic component is well explained by Thomson scattering in equatorial disk
of the Be-type mass donor. The position angle (PA) of the intrinsic
polarization represents the rotational axis of the Be disk.
This PA is nearly perpendicular to the PA of the radio jet found during
quiescent phases. Assuming an orthogonal disk-jet geometry around the compact
star, the rotational axis of the accretion disk is almost perpendicular to that
of the Be disk. Moreover, according to the orbital parameters of the
microquasar, the compact star is likely to get across the Be disk around their
periastron passage. We discuss the peculiar circumstellar structure of this
microquasar inferred from our observation and possible connection with its
high-energy activities.Comment: 17pages, 7figures; accepted for Publications of the Astronomical
Society of Japa
Dusty ERO Search behind Two Massive Clusters
We performed deep K'-band imaging observations of 2 massive clusters, MS
0451.6-0305 at z = 0.55 and MS 0440.5+0204 at z = 0.19, for searching
counterparts of the faint sub-mm sources behind these clusters, which would
provide one of the deepest extremely red object(ERO) samples. Comparing our
near-infrared images with optical images taken by the Hubble Space Telescope
and by the Subaru Telescope, we identified 13 EROs in these fields. The sky
distributions of EROs are consistent with the previous results, that there is a
sign of strong clustering among detected EROs. Also, the surface density with
corrected lensing amplification factors in both clusters are in good agreement
with that derived from previous surveys. We found 7 EROs and 3 additional very
red objects in a small area (\sim 0.6 arcmin^2) of the MS 0451.6-0305 field
around an extended SCUBA source. Many of their optical and near-infrared colors
are consistent with dusty star-forming galaxies at high redshifts(z \sim
1.0-4.0), and they may be constituting a cluster of dusty starburst galaxies
and/or lensed star-forming galaxies at high redshift. Their red J-K' colors and
faint optical magnitudes suggest they are relatively old massive stellar
systems with ages(>300 Mega years) suffering from dust obscuration. We also
found a surface-density enhancement of EROs around the SCUBA source in the MS
0440.5+0204 field.Comment: 19 pages, 11 figures, Latex(using pasj00.cls). To be published in
PASJ vol 55, No. 4(Aug 2003
Optical and Near-Infrared Photometry of Nova V2362 Cyg : Rebrightening Event and Dust Formation
We present optical and near-infrared (NIR) photometry of a classical nova,
V2362 Cyg (= Nova Cygni 2006). V2362 Cyg experienced a peculiar rebrightening
with a long duration from 100 to 240 d after the maximum of the nova. Our
multicolor observation indicates an emergence of a pseudophotosphere with an
effective temperature of 9000 K at the rebrightening maximum. After the
rebrightening maximum, the object showed a slow fading homogeneously in all of
the used bands for one week. This implies that the fading just after the
rebrightening maximum ( less or equal 1 week ) was caused by a slowly shrinking
pseudophotosphere. Then, the NIR flux drastically increased, while the optical
flux steeply declined. The optical and NIR flux was consistent with blackbody
radiation with a temperature of 1500 K during this NIR rising phase. These
facts are likely to be explained by dust formation in the nova ejecta. Assuming
an optically thin case, we estimate the dust mass of 10^(-8) -- 10^(-10)
M_solar, which is less than those in typical dust-forming novae. These results
support the senario that a second, long-lasting outflow, which caused the
rebrightening, interacted with a fraction of the initial outflow and formed
dust grains.Comment: 6 pages, 4 figures, 2010, PASJ, 62, 1103--1108, in pres
Tohoku-Hiroshima-Nagoya planetary spectra library: A method for characterizing planets in the visible to near infrared
There has not been a comprehensive framework for comparing spectral data from
different planets.Such a framework is needed for the study of extrasolar
planets and objects within the solar system. We have undertaken observations to
compile a library of planet spectra for all planets, some moons, and some dwarf
planets in the solar system to study their general spectroscopic and
photometric natures. During May and November of 2008, we acquired spectra for
the planets using TRISPEC, which is capable of simultaneous three-band
spectroscopy in a wide wavelength range of 0.45 - 2.5 microns with low
resolving power (lambda-over-Delta-lambda is 140 - 360). Patterns emerge from
comparing the spectra. Analyzing their general spectroscopic and photometric
natures, we show that it is possible to distinguish between gas planets, soil
planets and ice planets. These methods can be applied to extrasolar
observations using low resolution spectrography or broad-band filters. The
present planet spectral library is the first library to contain observational
spectra for all of the solar system planets, based on simultaneous observations
in visible and near infrared wavelengths. This library will be a useful
reference for analyzing extrasolar planet spectra, and for calibrating
planetary data sets.Comment: 11 pages, 6 figures, Accepted on 28/08/2009 to appear in Section 10.
Planets and planetary systems of Astronomy and Astrophysic
Homogeneous bubble nucleation limit of mercury under the normal working conditions of the planned European Spallation Source
In spallation neutron sources, liquid mercury is the subject of big thermal
and pressure shocks, upon adsorbing the proton beam. These changes can cause
unstable bubbles in the liquid, which can damage the structural material. While
there are methods to deal with the pressure shock, the local temperature shock
cannot be avoided. In our paper we calculated the work of the critical cluster
formation (i.e. for mercury micro-bubbles) together with the rate of their
formation (nucleation rate). It is shown that the homogeneous nucleation rates
are very low even after adsorbing several proton pulses, therefore the
probability of temperature induced homogeneous bubble nucleation is negligible.Comment: 22 Pages, 11 figures, one of them is colour, we plan to publish it in
Eur. Phys. J.
Efficacy of lamivudine for preventing hepatocellular carcinoma in chronic hepatitis B: A multicenter retrospective study of 2795 patients
ArticleHEPATOLOGY RESEARCH. 32(3): 173-184 (2005)journal articl
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
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