141 research outputs found
OVA特異的CD8陽性T細胞の移入によるinvolucrin-mOVAマウスの表現型解析
京都大学新制・論文博士博士(医学)乙第13516号論医博第2266号新制||医||1061(附属図書館)京都大学大学院医学研究科医学専攻(主査)教授 河本 宏, 教授 濵﨑 洋子, 教授 森本 尚樹学位規則第4条第2項該当Doctor of Medical ScienceKyoto UniversityDFA
Uniting the Quiescent Emission and Burst Spectra of Magnetar Candidates
Spectral studies of quiescent emission and bursts of magnetar candidates
using XMM-Newton, Chandra and Swift data are presented. Spectra of both the
quiescent emission and the bursts for most magnetar candidates are reproduced
by a photoelectrically absorbed two blackbody function (2BB). There is a strong
correlation between lower and higher temperatures of 2BB (kT_LT and kT_HT) for
the magnetar candidates of which the spectra are well reproduced by 2BB. In
addition, a square of radius for kT_T (R_LT^2) is well correlated with a square
of radius for kT_HT (R_HT^2). A ratio kT_LT/kT_HT ~ 0.4 is nearly constant
irrespective of objects and/or emission types (i.e., the quiescent emission and
the bursts). This would imply a common emission mechanism among the magnetar
candidates. The relation between the quiescent emission and the bursts might be
analogous to a relation between microflares and solar flares of the sun. Three
AXPs (4U 0142+614, 1RXS J170849.0-400910 and 1E 2259+586) seem to have an
excess above ~7 keV which well agrees with a non-thermal hard component
discovered by INTEGRAL.Comment: 17 pages, 5 figures, 12 tables, Accepted for publication in PAS
Spectral Comparison of Weak Short Bursts to the Persistent X-rays from the Magnetar 1E 1547.0-5408 in its 2009 Outburst
In January 2009, the 2.1-sec anomalous X-ray pulsar 1E 1547.0-5408 evoked
intense burst activity. A follow-up Suzaku observation on January 28 recorded
enhanced persistent emission both in soft and hard X-rays (Enoto et al. 2010b).
Through re-analysis of the same Suzaku data, 18 short bursts were identified in
the X-ray events recorded by the Hard X-ray Detector (HXD) and the X-ray
Imaging Spectrometer (XIS). Their spectral peaks appear in the HXD-PIN band,
and their 10-70 keV X-ray fluences range from ~2e-9 erg cm-2 to 1e-7 erg cm-2.
Thus, the 18 events define a significantly weaker burst sample than was ever
obtained, ~1e-8-1e-4 erg cm-2. In the ~0.8 to ~300 keV band, the spectra of the
three brightest bursts can be represented successfully by a two-blackbody
model, or a few alternative ones. A spectrum constructed by stacking 13 weaker
short bursts with fluences in the range (0.2-2)e-8 erg s-1 is less curved, and
its ratio to the persistent emission spectrum becomes constant at ~170 above ~8
keV. As a result, the two-blackbody model was able to reproduce the stacked
weaker-burst spectrum only after adding a power-law model, of which the photon
index is fixed at 1.54 as measured is the persistent spectrum. These results
imply a possibility that the spectrum composition employing an optically-thick
component and a hard power-law component can describe wide-band spectra of both
the persistent and weak-burst emissions, despite a difference of their fluxes
by two orders of magnitude. Based on the spectral similarity, a possible
connection between the unresolved short bursts and the persistent emission is
discussed.Comment: 21 pages, 18 figures and 3 tables. Accepted for publication in
Monthly Notices of the Royal Astronomical Society Main Journa
The Suzaku Discovery of A Hard Power-Law Component in the Spectra of Short Bursts from SGR 0501+4516
Using data with the Suzaku XIS and HXD, spectral studies of short bursts from
the soft gamma repeater SGR 0501+4516 were performed. In total, 32 bursts were
detected during the ~60 ks of observation conducted in the 2008 August
activity. Excluding the strongest one, the remaining 31 bursts showed an
average 2--40 keV fluence of 1.0(-0.5,+0.3)*10^-9 erg cm^-2. A 1--40 keV
spectrum summed over them leaves significant positive residuals in the HXD-PIN
band with chi^2/d.o.f. = 74/50, when fitted with a two-blackbody function. By
adding a power law model, the fit became acceptable with chi^2/d.o.f. = 56/48,
yielding a photon index of Gamma=1.0(-0.3,+0.4). This photon index is
comparable to Gamma=1.33(-0.16,+0.23) (Enoto et al. 2010a) for the persistent
emission of the same object obtained with Suzaku. The two-blackbody components
showed very similar ratios, both in the temperature and the emission radii, to
those comprising the persistent emission. However, the power-law to
two-blackbody flux ratio was possibly higher than that of the persistent
emission at 2.6 sigma level. Based on these measurements, average wide-band
properties of these relatively weak bursts are compared with those of the
persistent emission.Comment: 11 pages, 8 figures, 2 tables, Accepted for publication in PASJ
(Suzaku & MAXI special issue
Time-evolution of Peak Energy and Luminosity Relation within Pulses for GRB 061007: Probing Fireball Dynamics
We perform a time-resolved spectral analysis of bright, long Gamma-ray burst
GRB 061007 using Suzaku/WAM and Swift/BAT. Thanks to the large effective area
of the WAM, we can investigate the time evolution of the spectral peak energy,
Et_peak and the luminosity Lt_iso with 1-sec time resolution, and we find that
luminosity Lt_iso with 1-sec time resolution, and we find that the
time-resolved pulses also satisfy the Epeak-Liso relation, which was found for
the time-averaged spectra of other bursts, suggesting the same physical
conditions in each pulse. Furthermore, the initial rising phase of each pulse
could be an outlier of this relation with higher Et_peak value by about factor
2. This difference could suggest that the fireball radius expands by a factor
of 2-4 and/or bulk Lorentz factor of the fireball is decelerated by a factor of
4 during the initial phase, providing a new probe of the fireball dynamics in
real time.Comment: 21 pages, 16 figures, accepted for publication in PAS
Suzaku Discovery of a Hard X-Ray Tail in the Persistent Spectra from the Magnetar 1E 1547.0-5408 during its 2009 Activity
The fastest-rotating magnetar 1E 1547.0-5408 was observed in broad-band
X-rays with Suzaku for 33 ks on 2009 January 28-29, 7 days after the onset of
its latest bursting activity. After removing burst events, the
absorption-uncorrected 2-10 keV flux of the persistent emission was measured
with the XIS as 5.7e-11 ergs cm-2 s-1, which is 1-2 orders of magnitude higher
than was measured in 2006 and 2007 when the source was less active. The
persistent emission was also detected significantly with the HXD in >10 keV up
to at least ~110 keV, with an even higher flux of 1.3e-10 ergs cm-2 s-1 in
20-100 keV. The pulsation was detected at least up to 70 keV at a period of
2.072135+/-0.00005 s, with a deeper modulation than was measured in a fainter
state. The phase-averaged 0.7-114 keV spectrum was reproduced by an absorbed
blackbody emission with a temperature of 0.65+/-0.02 keV, plus a hard power-law
with a photon index of ~1.5. At a distance of 9 kpc, the bolometric luminosity
of the blackbody and the 2-100 keV luminosity of the hard power-law are
estimated as (6.2+/-1.2)e+35 ergs s-1 and 1.9e+36 ergs s-1, respectively, while
the blackbody radius becomes ~5 km. Although the source had not been detected
significantly in hard X-rays during the past fainter states, a comparison of
the present and past spectra in energies below 10 keV suggests that the hard
component is more enhanced than the soft X-ray component during the persistent
activity.Comment: 12 pages, 7 figures, PASJ Vol.62 No.2 accepte
Scaling properties of the chiral phase transition in the low density region of two-flavor QCD with improved Wilson fermions
We study scaling behavior of a chiral order parameter in the low density region, performing a simulation of two-flavor QCD with improved Wilson quarks. The scaling behavior of the chiral order parameter defined by a Ward-Takahashi identity agrees with the scaling function of the three-dimensional O(4) spin model at zero chemical potential. We extend the scaling study to finite density QCD. Applying the reweighting method and calculating derivatives of the chiral order parameter with respect to the chemical potential, the scaling properties of the chiral phase transition are discussed in the low density region. We moreover calculate the curvature of the phase boundary of the chiral phase transition in the temperature and chemical potential plane assuming the O(4) scaling relation.This work is in part supported by Grants-in-Aid of the Japanese Ministry of Education, Culture, Sports, Science and Technology (Nos. 21340049, 22740168, and 23540295) and by the Large Scale Simulation Program No.12/13-14 (FY2012-2013) of High Energy Accelerator Research Organization (KEK). SY is supported by JSPS Strategic Young Researcher Overseas Visits Program for Accelerating Brain Circulation (No. R2411). HS is also supported by JSPS for Young Scientists.The 31st International Symposium on Lattice Field Theory (LATTICE 2013) ; Place : Mainz, Germany ; Date : 29 July - 3 August, 201
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