33 research outputs found
Accretion Geometry of the Low-Mass X-ray Binary Aquila X-1 in the Soft and Hard States
The neutron-star Low-Mass X-ray Binary Aquila X-1 was observed seven times in
total with the Suzaku X-ray observatory from September 28 to October 30 in
2007, in the decaying phase of an outburst. In order to constrain the
flux-dependent accretion geometry of this source over wider energy bands than
employed in most of previous works, the present study utilized two out of the
seven data sets. The 0.8-31 keV spectrum on September 28, taken with the XIS
and HXD-PIN for an exposure of 13.8 ks, shows an absorbed 0.8-31 keV flux of
erg s cm, together with typical
characteristics of the soft state of this type of objects. The spectrum was
successfully explained by an optically-thick disk emission plus a Comptonized
blackbody component. Although these results are in general agreement with
previous studies, the significance of a hard tail recently reported using the
same data was inconclusive in our analysis. The spectrum acquired on October 9
for an exposure of 19.7 ks was detected over a 0.8-100 keV band with the XIS,
HXD-PIN, and HXD-GSO, at an absorbed flux of erg s
cm (in 0.8-100 keV). It shows characteristics of the hard state, and was
successfully explained by the same two continuum components but with rather
different parameters including much stronger thermal Comptonization, of which
the seed photon source was identified with blackbody emission from the
neutron-star surface. As a result, the accretion flow in the hard state is
inferred to take a form of an optically-thick and geometrically-thin disk down
to a radius of km from the neutron star, and then turn into an
optically-thin nearly-spherical hot flow.Comment: PASJ in publish. 12 pages including 16 figure
SMAP2, a novel ARF GTPase-activating protein, interacts with clathrin and clathrin assembly protein and functions on the AP-1-positive early endosome/trans-Golgi network
The truncated disk from Suzaku data of GX 339-4 in the extreme very high state
We report on the geometry of accretion disk and high energy coronae in the
strong Comptonization state (the very high/steep power law/hard intermediate
state) based on a Suzaku observation of the famous Galactic black hole GX
339-4. These data were taken just before the peak of the 2006-2007 outburst,
and the average X-ray luminosity in the 0.7-200 keV band is estimated to be
2.9E38 erg/s for a distance of 8 kpc. We fit the spectrum with both simple
(independent disk and corona) and sophisticated (energetically coupled disk and
corona) models, but all fits imply that the underlying optically thick disk is
truncated significantly before the innermost stable circular orbit around the
black hole. We show this directly by a comparison with similarly broadband data
from a disk dominated spectrum at almost the same luminosity observed by
XMM-Newton and RXTE 3 days after the Suzaku observation.
During the Suzaku observation, the QPO frequency changes from 4.3 Hz to 5.5
Hz, while the spectrum softens. The energetically coupled model gives a
corresponding 5+/- 8 % decrease in derived inner radius of the disk. While this
is not significant, it is consistent with the predicted change in QPO frequency
from Lense-Thirring precession of the hot flow interior to the disk and/or a
deformation mode of this flow, as a higher QPO frequency implies a smaller size
scale for the corona. This is consistent with the truncated disk extending
further inwards towards the black hole.Comment: Accepted to ApJ, 41 pages, 9 figures, 3 table
Long-term monitoring of the short period SU UMa-type dwarf nova, V844 Herculis
We report on time-resolved CCD photometry of four outbursts of a short-period
SU UMa-type dwarf nova, V844 Herculis. We successfully determined the mean
superhump periods to be 0.05584(64) days, and 0.055883(3) for the 2002 May
superoutburst, and the 2006 April-May superoutburst, respectively. During the
2002 October observations, we confirmed that the outburst is a normal outburst,
which is the first recorded normal outburst in V844 Her. We also examined
superhump period changes during 2002 May and 2006 April-May superoutbursts,
both of which showed increasing superhump period over the course of the plateau
stage. In order to examine the long-term behavior of V844 Her, we analyzed
archival data over the past ten years since the discovery of this binary.
Although photometry is not satisfactory in some superoutbursts, we found that
V844 Her showed no precursors and rebrightenings. Based on the long-term light
curve, we further confirmed V844 Her has shown almost no normal outbursts
despite the fact that the supercycle of the system is estimated to be about 300
days. In order to explain the long-term light curves of V844 Her, evaporation
in the accretion disk may play a role in the avoidance of several normal
outbursts, which does not contradict with the relatively large X-ray luminosity
of V844 Her.Comment: 10 pages, 11 figures, accepted for PAS
Radiation dose during relativistic electron precipitation events at the International Space Station
AbstractWe provide a quantitative estimate of the radiation dose during relativistic electron precipitation (REP) events at the International Space Station (ISS). To this goal, we take advantage of the data collected by the CALorimetric Electron Telescope, the Monitor of Allâsky Xâray Image, and the Space Environment Data Acquisition equipmentâAttached Payload. The three ISS detectors offer complementary REP observations, including energy spectra and flux directional information, during a period of approximately 2.5 years, from November 2015 to March 2018. We have identified 762 REP events during this period from which we obtain the distribution of radiation dose, relevant to extravehicular activities outside the ISS
Detection of the thermal component in GRB 160107A
We present the detection of a blackbody component in gamma-ray burst GRB 160107A emission by using the combined spectral data of the CALET Gamma-ray Burst Monitor (CGBM) and the MAXI Gas Slit Camera (GSC). MAXI/GSC detected the emission âŒ45 s prior to the main burst episode observed by the CGBM. The MAXI/GSC and the CGBM spectrum of this prior emission period is fitted well by a blackbody with temperature 1.0 +0.3-0.2 keV plus a power law with a photon index of -1.6 ± 0.3. We discuss the radius of the photospheric emission and the main burst emission based on the observational properties. We stress the importance of coordinated observations via various instruments collecting high-quality data over a broad energy coverage in order to understand the GRB prompt emission mechanism
Chemical synthesis of the EPF-family of plant cysteine-rich proteins and late-stage dye attachment by chemoselective amide-forming ligations
Chemical protein synthesis can provide well-defined modified proteins. Herein, we report the chemical synthesis of plant-derived cysteine-rich secretory proteins and late-stage derivatization of the synthetic proteins. The syntheses were achieved with distinct chemoselective amide bond forming reactions - EPF2 by native chemical ligation (NCL), epidermal patterning factor (EPF) 1 by the alpha-ketoacid-hydroxylamine (KAHA) ligation, and fluorescent functionalization of their folded variants by potassium acyltrifluoroborate (KAT) ligation. The chemically synthesized EPFs exhibit bioactivity on stomatal development in Arabidopsis thaliana. Comprehensive synthesis of EPF derivatives allowed us to identify suitable fluorescent variants for bioimaging of the subcellar localization of EPFs.ISSN:2633-067