Highlights of the HETE-2 Mission Lamb, D. Q; Ricker, G. R; Atteia, J. -L ...
arXiv (Cornell University),
10/2003
Journal Article
Odprti dostop
The HETE-2 mission has been highly productive. It has observed more than 250
GRBs so far. It is currently localizing 25 - 30 GRBs per year, and has
localized 43 GRBs to date. Twenty-one of these ...localizations have led to the
detection of X-ray, optical, or radio afterglows, and as of now, 11 of the
bursts with afterglows have redshift determinations. HETE-2 has also observed
more than 45 bursts from soft gamma-ray repeaters, and more than 700 X-ray
bursts. HETE-2 has confirmed the connection between GRBs and Type Ic
supernovae, a singular achievement and certainly one of the scientific
highlights of the mission so far. It has provided evidence that the
isotropic-equivalent energies and luminosities of GRBs may be correlated with
redshift; such a correlation would imply that GRBs and their progenitors evolve
strongly with redshift. Both of these results have profound implications for
the nature of GRB progenitors and for the use of GRBs as a probe of cosmology
and the early universe. HETE-2 has placed severe constraints on any X-ray or
optical afterglow of a short GRB. It has made it possible to explore the
previously unknown behavior optical afterglows at very early times, and has
opened up the era of high-resolution spectroscopy of GRB optical afterglows. It
is also solving the mystery of "optically dark" GRBs, and revealing the nature
of X-ray flashes (XRFs).
New Astron.Rev.48:423-430,2004;
Nucl.Phys.Proc.Suppl.132:279-288,2004 The HETE-2 mission has been highly productive. It has observed more than 250
GRBs so far. It is currently localizing 25 - 30 GRBs ...per year, and has
localized 43 GRBs to date. Twenty-one of these localizations have led to the
detection of X-ray, optical, or radio afterglows, and as of now, 11 of the
bursts with afterglows have known redshifts. HETE-2 has confirmed the
connection between GRBs and Type Ic supernovae, a singular achievement and
certainly one of the scientific highlights of the mission so far. It has
provided evidence that the isotropic-equivalent energies and luminosities of
GRBs are correlated with redshift, implying that GRBs and their progenitors
evolve strongly with redshift. Both of these results have profound implications
for the nature of GRB progenitors and for the use of GRBs as a probe of
cosmology and the early universe. HETE-2 has placed severe constraints on any
X-ray or optical afterglow of a short GRB. It is also solving the mystery of
"optically dark' GRBs, and revealing the nature of X-ray flashes.
AIP Conf.Proc.727:106-110,2004 We report HETE-2 WXM/FREGATE observations of the X-ray flash, XRF 020903.
This event was extremely soft: the ratio log(S_X/S_gamma) = 0.7, where S_X and
S_gamma are the ...fluences in the 2-30 and 30-400 keV energy bands, is the most
extreme value observed so far by HETE-2. In addition, the spectrum has an
observed peak energy E^{obs}_{peak} < 5.0 keV (99.7 % probability upper limit)
and no photons were detected above ~10 keV. The burst is shorter at higher
energies, which is similar to the behavior of long GRBs. We consider the
possibility that the burst lies at very high redshift and that the low value of
E^{obs}_{peak} is due to the cosmological redshift, and show that this is very
unlikely. We find that the properties of XRF 020903 are consistent with the
relation between the fluences S(7-30 keV) and S(30-400 keV) found by Barraud et
al. for GRBs and X-ray-rich GRBs, and are consistent with the extension by a
decade of the hardness-intensity correlation (Mallozzi et al. 1995) found by
the same authors. Assuming that XRF 020903 lies at a redshift z = 0.25 as
implied by the host galaxy of the candidate optical and radio afterglows of
this burst, we find that the properties of XRF 020903 are consistent with an
extension by a factor ~300 of the relation between the isotropic-equivalent
energy E_iso and the peak E_peak of the nu F_nu spectrum (in the source frame
of the burst) found by Amati et al. for GRBs. The results presented in this
paper therefore provide evidence that XRFs, X-ray-rich GRBs, and GRBs form a
continuum and are a single phenomenon. The results also impose strong
constraints on models of XRFs and X-ray-rich GRBs.
Since 1978, our group has examined porphyrin derivatives based on hemoglobin and chlorophyll and their metal complexes (200 in all) through the cooperation of Sakata et all, of Toyohakka Kogyo. We ...have previously found and reported that side chain structure and tumor tissue accumulation are related. Based on the datas obtained, our study now been forcused on making the following substances available. a) Bacterio-pheophorbide (λ=755nm) which has an absorption band shifted to longer wavelength than that of HPD or DHE, so that deeper tissue penetration of photo-radiation can be achieved. b) Highly tumor-seeking radiopharmaceuticals for scintigraphic studies that have advantages over Ga-67 citrate which is used clinically in the world. c) New cancer-targetting anti-tumor chemicals which have accumulate and remain in cancer tissue. In this congress, I would like to report our results of investigation.
Astrophys.J. 599 (2003) 387-393 A bright, x-ray-rich GRB was detected by HETE-2 at 11:18:34.03 UT on 11 Dec
2002. The WXM localization was to 14' and relayed to the GCN 22 s after the
start of the ...burst. The ground SXC localization was within 2' of R.A. 08h 09m
00s, Dec 06d 44' 20" (J2000). GRB021211 consists of a single, FRED-like pulse
with t90s of 2.3 s (85-400 keV) and 8.5 s (2-10 keV). The peak photon number
and photon energy fluxes in the 2-400 keV band, are 34.0 +/- 1.8 ph cm^-2 s^-1
and 1.68 +/- 0.11 x 10^-6 erg cm^-2 s^-1, respectively. The energy fluences in
the 2-30 keV and 30-400 kev energy bands are S_X = 1.36 +/- 0.05 x 10^-6 erg
cm^-2 and S_gamma 2.17 +/- 0.15 x 10^-6 erg cm^-2, respectively. Thus GRB021211
is an X-ray-rich GRB (S_X/S_gamma = 0.63 > 0.32). The spectrum is well-fit by a
Band function (alpha = -0.805, beta = -2.37, E_peak = 46.8 keV). The prompt
localization allowed the detection of an optical afterglow for what would
otherwise have been an ``optically dark'' GRB. GRB 021211 demonstrates that
some fraction of burst afterglows are ``optically dark'' because their optical
afterglows at times > 1 hr after the burst are very faint, and thus have often
escaped detection. GRB 021211 shows that such ``optically dim'' bursts can have
very bright afterglows at times < 20 min after the burst.
On September 21 at 18950.56 SOD (05:15:50.56) UT the FREGATE gamma-ray
instrument on the High Energy Transient Explorer (HETE) detected a bright
gamma-ray burst (GRB). The burst was also seen by the ...X-detector on the WXM
X-ray instrument and was therefore well-localized in the X direction; however,
the burst was outside the fully-coded field-of-view of the WXM Y-detector, and
therefore information on the Y direction of the burst was limited.
Cross-correlation of the HETE and Ulysses time histories yielded an
Interplanetary Network (IPN) annulus that crosses the HETE error strip at a ~45
degree angle. The intersection of the HETE error strip and the IPN annulus
produces a diamond-shaped error region for the location of the burst having an
area of 310 square arcminutes. Based on the FREGATE and WXM light curves, the
duration of the burst is characterized by a t90 = 18.4 s in the WXM 4 - 25 keV
energy range, and 23.8 s and 21.8 s in the FREGATE 6 - 40 and 32 - 400 keV
energy ranges, respectively. The fluence of the burst in these same energy
ranges is 4.8 10^{-6}, 5.5 10^{-6}, and 11.4 10^{-6} erg cm^{-2}, respectively.
Subsequent optical and radio observations by ground-based observers have
identified the afterglow of GRB010921 and determined an apparent redshift of z
= 0.450.
The {\it HETE-2} (hereafter \HETE) French Gamma Telescope (FREGATE) and the
Wide-field X-ray Monitor (WXM) instruments detected a short ($t_{50} = 360$
msec in the FREGATE 85-300 keV energy band), ...hard gamma-ray burst (GRB) that
occurred at 1578.72 SOD (00:26:18.72 UT) on 31 May 2002. The WXM flight
localization software produced a valid location in spacecraft (relative)
coordinates. However, since no on-board real-time star camera aspect was
available, an absolute localization could not be disseminated. A preliminary
localization was reported as a GCN Position Notice at 01:54:22 UT, 88 min after
the burst. Further ground analysis produced a refined localization, which can
be expressed as a 90% confidence rectangle that is 67 arcminutes in RA and 43
arcminutes in Dec (90% confidence region), centered at RA = +15$^{\rm h}$
14$^{\rm m}$ 45$^{\rm s}$, Dec = -19$^\circ$ 21\arcmin 35\arcsec (J2000). An
IPN localization of the burst was disseminated 18 hours after the GRB (Hurley
et al. 2002b). A refined IPN localization was disseminated $\approx$ 5 days
after the burst. This hexagonal-shaped localization error region is centered on
RA = 15$^{\rm h}$ 15$^{\rm m}$ 03.57$^{\rm s}$, -19$^\circ$ 24\arcmin
51.00\arcsec (J2000), and has an area of $\approx$ 22 square arcminutes (99.7%
confidence region). The prompt localization of this short, hard GRB by \HETE
and the anti-Sun pointing of the \HETE instruments, coupled with the refinement
of the localization by the IPN, has made possible rapid follow-up observations
of the burst at radio, optical, and X-ray wavelengths.
We present a spectral analysis of 35 GRBs detected with the HETE-2 gamma-ray
detectors (the FREGATE instrument) in the energy range 7-400 keV. The GRB
sample analyzed is made of GRBs localized with ...the Wide Field X-ray Monitor
onboard HETE-2 or with the GRB Interplanetary Network. We derive the spectral
parameters of the time-integrated spectra, and present the distribution of the
low-energy photon index, alpha, and of the peak energy, e_peak . We then
discuss the existence and nature of the recently discovered X-Ray Flashes and
their relationship with classical GRBs.
MAXI, Monitor of All-sky X-ray Image, is the X-ray observatory on the
Japanese experimental module (JEM) Exposed Facility (EF) on the International
Space Station (ISS). MAXI is a slit scanning camera ...which consists of two kinds
of X-ray detectors: one is a one-dimensional position-sensitive proportional
counter with a total area of $\sim 5000 cm^2$, the Gas Slit Camera (GSC), and
the other is an X-ray CCD array with a total area $\sim 200 cm^2$, the
Solid-state Slit Camera (SSC). The GSC subtends a field of view with an angular
dimension of 1$^\circ\times 180^\circ$ while the SSC subtends a field of view
with an angular dimension of 1$^\circ$ times a little less than 180$^\circ$. In
the course of one station orbit, MAXI can scan almost the entire sky with a
precision of 1$^\circ$ and with an X-ray energy range of 0.5-30 keV. We have
developed the engineering model of CCD chips and the analogue electronics for
the SSC. The energy resolution of EM CCD for Mn K$\alpha$ has a full-width at
half maximum of $\simeq$ 182 eV. Readout noise is $\simeq$ 11 e^- rms.
Changes in aortic lipolytic enzyme activities (cholesterol esterase and lipoprotein lipase) and acid phosphatase activity during aging were investigated in three strains of rats with different blood ...pressures; stroke prone spontaneously hypertensive rats (SHRSP), spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto (WKR). The blood pressures of male, 7 month old animals, was 234 (SHRSP), 173 (SHR) and 128 (WKR) mmHg. The cholesterol esterase activity markedly decreased with age in the aortas of SHRSP, SHR and normotensive WKR rats, while acid phosphatase activity decreased only slightly, if at all, and lipoprotein lipase activity remained unchanged. This effect was enhanced by increasing blood pressure in SHRSP, SHR and WKR. The total aortic cholesterol content increased significantly with hypertension in a inverse relation with cholesterol esterase activity. These results suggest that cholesterol deposition in aged arteries is, at least partialy, ascribable to an age-related decrease in cholesterol esterase, and that hypertension aggravates the deposition of arterial cholesterol by accelerating the age-related decrease in aortic cholesterol esterase activity.
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