15,225 research outputs found
Evidence for gamma-ray emission from the low-mass X-ray binary system FIRST J102347.6+003841
The low-mass X-ray binary (LMXB) system FIRST J102347.6+003841 hosts a newly
born millisecond pulsar (MSP) PSR J1023+0038 that was revealed as the first and
only known rotation-powered MSP in a quiescent LMXB. While the system is shown
to have an accretion disk before 2002, it remains unclear how the accretion
disk has been removed in order to reveal the radio pulsation in 2007. In this
Letter, we report the discovery of gamma-rays spatially consistent with FIRST
J102347.6+003841, at a significance of 7 standard deviations, using data
obtained by the Fermi Gamma-ray Space Telescope. The gamma-ray spectrum can be
described by a power law (PL) with a photon index of 2.9+-0.2, resulting in an
energy flux above 200 MeV of (5.5+-0.9)x10^{-12} erg cm^{-2}s^{-1}. The
gamma-rays likely originate from the MSP PSR J1023+0038, but also possibly from
an intrabinary shock between the pulsar and its companion star. To complement
the gamma-ray study, we also re-investigate the XMM-Newton data taken in 2004
and 2008. Our X-ray spectral analysis suggests that a broken PL with two
distinct photon indices describes the X-ray data significantly better than a
single PL. This indicates that there exists two components and that both
components appear to vary with the orbital phase. The evidence for gamma-ray
emission conforms with a recent suggestion that gamma-rays from PSR J1023+0038
may be responsible for ejecting the disk material out of the system.Comment: 10 pages, 3 figures, 2 tables, ApJ Letters, in press; corrections
made for the gamma flux value
4-D Quantum Dilaton Gravity During Inflation and Renormalization at One loop
We consider 4D quantum-dilaton gravity with the most general coupling in a
homogeneous and isotropic universe, especially an inflationary one, which is
essentially characterized by an exponentially expanding scale factor with time.
We show that on the inflationary background this theory can be miraculously
renormalized, at least at the one-loop level, which must be an effective theory
during the inflation of the un-constructed complete quantum theory of gravity.Comment: 18 pages, latex, no figures. This paper also available at
http://theory.kek.jp/~takata/mypaper/paper.html#mypaper5.p
Three-dimensional Two-Layer Outer Gap Model: Fermi Energy Dependent Light Curves of the Vela Pulsar
We extend the two-dimensional two-layer outer gap model to a
three-dimensional geometry and use it to study the high-energy emission of the
Vela pulsar. In this model, the outer gap is divided into two parts, i.e. the
main acceleration region on the top of last-open field lines and the screening
region around the upper boundary of the gap. In the main acceleration region,
the charge density is much lower than the Goldreich-Julian charge density and
the charged particles are accelerated by the electric field along the magnetic
field to emit multi-GeV photons. In the screening region, the charge density is
larger than the Goldreich-Julian value to close the gap and particles in this
region are responsible for multi-100MeV photon emission. We apply this three
dimensional two-layer model to the Vela pulsar and compare the model light
curves, the phase-averaged spectrum and the phase-resolved spectra with the
recent Fermi observations, which also reveals the existence of the third peak
between two main peaks. The phase position of the third peak moves with the
photon energy, which cannot be explained by the geometry of magnetic field
structure and the caustic effects of the photon propagation. We suggest that
the existence of the third peak and its energy dependent movement results from
the azimuthal structure of the outer gap.Comment: 11 pages, 15 figures, accepted for publication in MNRA
Diagnosis of drug induced liver injury using a lymphocyte blast transformation test based on whole blood culture
Twenty cases of suspected drug induced liver injury (16 cases of which satisfied the criteria for at least a query positive diagnosis as based on the Fourth Congress of "Drugs and the Liver" in Japan) were studied by the whole blood culture technique of lumphocyte blast transformation. The positive rate with this technique was 10%, and no more than 15% even with the addition of one query positive. One reason for the low positive rate was that there was not only an allergic mechanism at work in the study group but that liver injury due to direct cytotoxicity of the drug was involved also. For a drug such as chlorpromazine with strong cytotoxicity for lymphocytes, it was difficult to demonstrate a relationship between allergic mechanisms and the drug with this method.</p
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