60 research outputs found
Study of the Spectral and Temporal Characteristics of X-Ray Emission of the Gamma-Ray Binary LS 5039 with Suzaku
We report on the results from Suzaku broadband X-ray observations of the
galactic binary source LS5039. The Suzaku data, which have continuous coverage
of more than one orbital period, show strong modulation of the X-ray emission
at the orbital period of this TeV gamma-ray emitting system.The X-ray emission
shows a minimum at orbital phase ~ 0.1, close to the so-called superior
conjunction of the compact object, and a maximum at phase ~0.7, very close to
the inferior conjunction of the compact object. The X-ray spectral data up to
70 keV are described by a hard power-law with a phase-dependent photon index
which varies within Gamma ~1.45 - 1.61. The amplitude of the flux variation is
a factor of 2.5, but is significantly less than that of the factor ~8 variation
in the TeV flux. Otherwise the two light curves are similar, but not identical.
Although periodic X-ray emission has been found from many galactic binary
systems, the Suzaku result implies a phenomenon different from the "standard"
origin of X-rays related to the emission of the hot accretion plasma formed
around the compact companion object. The X-ray radiation of LS5039is likely to
be linked to very-high-energy electrons which are also responsible for the TeV
gamma-ray emission. While the gamma-rays are the result of inverse Compton
scattering by electrons on optical stellar photons, X-rays are produced via
synchrotron radiation. Yet, while the modulation of the TeV gamma-ray signal
can be naturally explained by the photon-photon pair production and anisotropic
inverse Compton scattering, the observed modulation of synchrotron X-rays
requires an additional process, the most natural one being adiabatic expansion
in the radiation production region.Comment: 9 pages, 7 figures, Accepted for publication in ApJ, references
fixed, a few typos correcte
Soft Gamma-ray Detector for the ASTRO-H Mission
ASTRO-H is the next generation JAXA X-ray satellite, intended to carry
instruments with broad energy coverage and exquisite energy resolution. The
Soft Gamma-ray Detector (SGD) is one of ASTRO-H instruments and will feature
wide energy band (40-600 keV) at a background level 10 times better than the
current instruments on orbit. SGD is complimentary to ASTRO-H's Hard X-ray
Imager covering the energy range of 5-80 keV. The SGD achieves low background
by combining a Compton camera scheme with a narrow field-of-view active shield
where Compton kinematics is utilized to reject backgrounds. The Compton camera
in the SGD is realized as a hybrid semiconductor detector system which consists
of silicon and CdTe (cadmium telluride) sensors. Good energy resolution is
afforded by semiconductor sensors, and it results in good background rejection
capability due to better constraints on Compton kinematics. Utilization of
Compton kinematics also makes the SGD sensitive to the gamma-ray polarization,
opening up a new window to study properties of gamma-ray emission processes.
The ASTRO-H mission is approved by ISAS/JAXA to proceed to a detailed design
phase with an expected launch in 2014. In this paper, we present science
drivers and concept of the SGD instrument followed by detailed description of
the instrument and expected performance.Comment: 17 pages, 15 figures, Proceedings of the SPIE Astronomical
Instrumentation "Space Telescopes and Instrumentation 2010: Ultraviolet to
Gamma Ray
Serum Antibody Against NY-ESO-1 and XAGE1 Antigens Potentially Predicts Clinical Responses to Anti–Programmed Cell Death-1 Therapy in NSCLC
Introduction: Programmed cell death-1 (PD-1) inhibitors effectively treat NSCLC and prolong survival. Robust biomarkers for predicting clinical benefits of good response and long survival with anti-PD-1 therapy have yet to be identified; therefore, predictive biomarkers are needed to select patients with benefits.
Methods: We conducted a prospective study to explore whether serum antibody against NY-ESO-1 and/or XAGE1 cancer-testis antigens predicted primarily good clinical response and secondarily long survival with anti-PD-1 therapy for NSCLC. The serum antibody was detected by enzyme-linked immunosorbent assay, and tumor immune microenvironment and mutation burden were analyzed by immunohistochemistry and next-generation sequencing.
Results: In the discovery cohort (n = 13), six antibody-positive NSCLC cases responded to anti-PD-1 therapy (two complete and four partial responses), whereas seven antibody-negative NSCLC cases did not. Antibody positivity was associated with good response and survival, regardless of tumor programmed death ligand 1 (PD-L1) expression, mutation burden, and CD8+ T-cell infiltration. In the validation cohort (n = 75), 17 antibody-positive NSCLC cases responded well to anti-PD-1 therapy as compared with 58 negative NSCLC cases (objective response rate 65% versus 19%, p = 0.0006) and showed significantly prolonged progression-free survival and overall survival. Antibody titers highly correlated with tumor reduction rates. In the multivariate analysis, response biomarkers were tumor programmed death ligand 1 expression and antibody positivity, and only antibody positivity was a significantly better predictive biomarker of progression-free survival (hazard ratio = 0.4, p = 0.01) and overall survival (hazard ratio = 0.2, p = 0.004).
Conclusions: Our results suggest that NY-ESO-1 and/or XAGE1 serum antibodies are useful biomarkers for predicting clinical benefits in anti-PD-1 therapy for NSCLC and probably for other cancers
Hitomi (ASTRO-H) X-ray Astronomy Satellite
The Hitomi (ASTRO-H) mission is the sixth Japanese x-ray astronomy satellite developed by a large international collaboration, including Japan, USA, Canada, and Europe. The mission aimed to provide the highest energy resolution ever achieved at E > 2 keV, using a microcalorimeter instrument, and to cover a wide energy range spanning four decades in energy from soft x-rays to gamma rays. After a successful launch on February 17, 2016, the spacecraft lost its function on March 26, 2016, but the commissioning phase for about a month provided valuable information on the onboard instruments and the spacecraft system, including astrophysical results obtained from first light observations. The paper describes the Hitomi (ASTRO-H) mission, its capabilities, the initial operation, and the instruments/spacecraft performances confirmed during the commissioning operations for about a month
Hitomi X-Ray Studies of Giant Radio Pulses from the Crab Pulsar
To search for giant X-ray pulses correlated with the giant radio pulses (GRPs) from the Crab pulsar, we performed a simultaneous observation of the Crab pulsar with the X-ray satellite Hitomi in the 2300 keV band and the Kashima NICT radio telescope in the 1.41.7 GHz band with a net exposure of about 2 ks on 2016 March 25, just before the loss of the Hitomi mission. The timing performance of the Hitomi instruments was confirmed to meet the timing requirement and about 1000 and 100 GRPs were simultaneously observed at the main pulse and inter-pulse phases, respectively, and we found no apparent correlation between the giant radio pulses and the X-ray emission in either the main pulse or inter-pulse phase. All variations are within the 2 fluctuations of the X-ray fluxes at the pulse peaks, and the 3 upper limits of variations of main pulse or inter-pulse GRPs are 22% or 80% of the peak flux in a 0.20 phase width, respectively, in the 2300 keV band. The values for main pulse or inter-pulse GRPs become 25% or 110%, respectively, when the phase width is restricted to the 0.03 phase. Among the upper limits from the Hitomi satellite, those in the 4.510 keV and 70300 keV bands are obtained for the first time, and those in other bands are consistent with previous reports. Numerically, the upper limits of the main pulse and inter-pulse GRPs in the 0.20 phase width are about (2.4 and 9.3) 10(exp 11) erg cm(exp 2), respectively. No significant variability in pulse profiles implies that the GRPs originated from a local place within the magnetosphere. Although the number of photon-emitting particles should temporarily increase to account for the brightening of the radio emission, the results do not statistically rule out variations correlated with the GRPs, because the possible X-ray enhancement may appear due to a >0.02% brightening of the pulse-peak flux under such conditions
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