Search

We investigated the properties of active galactic nucleus (AGN) environments, particularly environments where the association of a luminous galaxy (LG) is found within 4 Mpc from an AGN with redshift 0.8–1.1. For comparison, three additional AGN environments, (namely, AGNs of all types, type 1 AGNs with X-ray and/or radio detection, and type 2 AGNs) and an environment of blue M*, the characteristic luminosity of the Schechter function, galaxies were investigated. The cross-correlation function with the surrounding galaxies was measured and compared between the AGN and blue galaxy samples. We also compared the distributions of color, absolute magnitude, and stellar mass of the galaxies around such target objects. The properties of clusters detected using surrounding galaxies selected based on a photometric redshift were examined and compared for different samples. The target AGNs were drawn from the Million Quasars (MILLIQUAS) catalog, and the blue galaxies were drawn from six redshift survey catalogs (SDSS, WiggleZ, DEEP2, VVDS, VIPERS, and PRIMUS). The galaxies used as a measure of the environment around the targets were drawn from the S18a internal data released by the Hyper Suprime-Cam Subaru Strategic Program. We found that, among the five AGN and blue galaxy samples considered, the environment of AGN–LG pairs is the most enriched with luminous galaxies. We also found an enhancement in the number of mass-selected clusters in the AGN–LG pair sample against those in the other samples. The results obtained in this study indicate that existence of multiple clusters is the major driver in the association of AGNs and LGs, rather than a single large-mass dark matter halo hosting the AGN.

We have measured the clustering of galaxies around active galactic nuclei (AGN) for which single-epoch virial masses of the super-massive black hole (SMBH) are available to investigate the relation between the large scale environment of AGNs and the evolution of SMBHs. The AGN samples used in this work were derived from the Sloan Digital Sky Survey (SDSS) observations and the galaxy samples were from 240~deg$^{2}$ S15b data of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). The investigated redshift range is 0.6--3.0, and the masses of the SMBHs lie in the range $10^{7.5}$--$10^{10}$~M$_{\odot}$. The absolute magnitude of the galaxy samples reaches to $M_{\lambda 310}$ $\sim$ $-$18 at rest frame wavelength 310~nm for the low-redshift end of the samples. More than 70\% of the galaxies in the analysis are blue. We found a significant dependence of the cross-correlation length on redshift, which primarily reflects the brightness dependence of the galaxy clustering. At the lowest redshifts the cross-correlation length increases from 7~$h^{-1}$~Mpc around $M_{\lambda 310}$$ = $$-19$~mag to $>$10~$h^{-1}$~Mpc beyond $M_{\lambda 310}$$ = $$-20$~mag. No significant dependence of the cross-correlation length on BH mass was found for whole galaxy samples dominated by blue galaxies, while there was an indication of BH mass dependence in the cross-correlation with red galaxies. These results provides a picture of the environment of AGNs studied in this paper being enriched with blue starforming galaxies, and a fraction of the galaxies are being evolved to red galaxies along with the evolution of SMBHs in that system., Comment: 46 pages, 24 figures, accepted for publication in PASJ for the HSC special issue

We have measured the lateral distributions of atmospheric C˘erenkov photons associated with extensive air showers to study the chemical composition of the primary cosmic rays in the energy range from 10 14.5 to 10 16 eV, so called knee region. The atmospheric C˘erenkov photon detectors were installed in the EAS array at Mt. Chacaltaya. The measured lateral distributions were fitted with an empirical formula with a parameter which is sensitive to mass numbers of primary cosmic rays. A three species model (proton, carbon, and iron nuclei) is used for the chemical composition study of the present experiment. To determine the mixing ratio of the three species, the distributions of the parameter for the observed events were examined to reproduce those for the simulated ones calculated with the CORSIKA code using the QGSJET hadronic interaction model. From the obtained mixing ratio of the three species, we determined the mean logarithmic mass numbers of primary cosmic rays, 〈ln A 〉, in the knee region. The present result shows that the values of 〈ln A 〉 are higher than the logarithmic mass number for carbon and the proton component is no more dominant at the knee.

We present results of the clustering analysis between active galactic nuclei (AGNs) and galaxies at redshift 0.1-1.0 for investigating properties of galaxies associated with the AGNs, revealing the nature of fueling mechanism of supermassive black holes (SMBHs). We used 8059 SDSS AGNs/QSOs for which virial masses of individual SMBHs were measured, and divided them into four mass groups. Cross-correlation analysis was performed and bias for each mass group was derived. The averaged color and luminosity distributions of galaxies around the AGNs/QSOs were also derived for each mass group. The galaxy color was estimated for SED constructed from a merged SDSS and UKIDSS catalog. The distributions of color and luminosity were derived by the subtraction method, which does not require redshift information of galaxies. The main results of this work are: (1) a bias increases by a factor two from the lower mass group to the highest mass group; (2) the environment around AGNs with the most massive SMBH (Mbh > 10^9 Msun) is dominated by red sequence galaxies; (3) marginal indication of decline in luminosity function at dimmer side of M > -19.5 mag is found for galaxies around AGNs with Mbh = 10^8.2 - 10^9 Msun and nearest redshift group (z=0.1-0.3). These results indicate that AGNs with the most massive SMBHs reside in haloes where large fraction of galaxies have been transited to the red sequence. The accretion of hot halo gas as well as recycled gas from evolving stars can be the most plausible mechanism to fuel the SMBHs above ~10^9 Msun., 23 pages, 20 figures, Accepted for publication in PASJ

HETE‐2 localized 63 flares from SGR1806‐20 and 6 flares from SGR1900+14 in the summer periods from June 18 2001 through August 7 2005. We report on the temporal and spectral analyses of short flares from those SGRs. The estimation of T90 durations in 2–30 keV and 30–100 keV revealed that there is no difference between them with a few exceptions. For these exceptional short flares, there seems softening or possibly hardening during flares, but these spectral evolution are not common. We also found a good linear correlation between the rise and decay time, and they do not depend on a peak flux. We also found that the spectra are well reproduced by a sum of two blackbody models for all short flares. The temperatures are lying around 4 keV and 11 keV which are consistent with previous studies. They are not depend on either the magnitude of flare, the event morphology or the source.

We describe and discuss the global properties of 45 gamma-ray bursts (GRBs) observed by HETE-2 during the first 3 years of its mission, focusing on the properties of X-ray flashes (XRFs) and X-ray-rich GRBs (XRRs). We find that the numbers of XRFs, XRRs, and GRBs are comparable, and that the durations and the sky distributions of XRFs and XRRs are similar to those of GRBs. We also find that the spectral properties of XRFs and XRRs are similar to those of GRBs, except that the values of the peak energy Eobspeak of the burst spectrum in νFν, the peak energy flux Fpeak, and the energy fluence SE of XRFs are much smaller (and those of XRRs are smaller) than those of GRBs. Finally, we find that the distributions of all three kinds of bursts form a continuum in the [SE(2-30 keV), SE(30-400) keV] plane, the [SE(2-400 keV), Epeak] plane, and the [Fpeak(50-300 keV), Epeak] plane. These results provide strong evidence that all three kinds of bursts arise from the same phenomenon.

An exceptionally intense gamma-ray burst, GRB030329, was detected and localized by the instruments on board the High Energy Transient Explorer satellite (HETE) at 11:37:14 UT on 29 March 2003. The burst consisted of two \~10s pulses of roughly equal brightness and an X-ray tail lasting >100s. The energy fluence in the 30-400 keV energy band was 1.08e-4 erg/cm2, making GRB030329 one of the brightest GRBs ever detected. Communication of a 2 arcmin error box 73 minutes after the burst allowed the rapid detection of a counterpart in the optical, X-ray, radio and the ensuing discovery of a supernova with most unusual characteristics. Analyses of the burst lightcurves reveal the presence of a distinct, bright, soft X-ray component underlying the main GRB: the 2-10 keV fluence of this component is ~7e-6 erg/cm2. The main pulses of GRB030329 were preceded by two soft, faint, non-thermal bumps. We present details of the HETE observations of GRB030329., 22 pages, 5 figures, to be published in ApJ 617, no. 2 (10 December 2004). Referee comments have been incorporated; results of improved spectral analysis are included

We have measured extensive air showers with primary energies above 6 TeV at Mount Chacaltaya in Bolivia. The data were collected by an air shower array called the Minimum Air Shower (MAS) array starting in 2000 March. We applied an equi-intensity analysis method to the extensive air showers extended over the region of their maximum development. We varied the mixture of protons and iron in our simulations and compared these to the data to determine the mixing ratio of protons as a function of the primary energy. Using this, we derived the primary energy spectrum from 1014 to 5 × 1016 eV. Consequently, we conclude that the power-law index of the spectrum changes gradually around 1015.5 eV and that the obtained proton ratio decreases with increasing energy. We directly measured the longitudinal development of air showers generated by primaries with energies around the knee. We found that the average mass number of primary cosmic rays shows a steady increase with energy above 1014.5 eV and that the dominant component around the knee is not protons.

We report High Energy Transient Explorer 2 (HETE-2) Wide Field X-Ray Monitor/French Gamma Telescope observations of the X-ray flash XRF 020903. This event was extremely soft: the ratio log(SX/Sγ)=0.7, where SX and Sγ 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 of Eobspeakobspeak 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 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 Eiso and the peak Epeak of the νFν 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 X-ray flashes (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.

Solar neutrons have been detected using the neutron monitor located at Mt. Chacaltaya, Bolivia, in association with a large solar flare on November 24, 2000. This is the first detection of solar neutrons by the neutron monitor that have been reported so far in solar cycle 23. The statistical significance of the detection is 5.5 sigma. In this flare, the intense emission of hard X-rays and gamma-rays has been observed by the Yohkoh Hard X-ray Telescope (HXT) and Gamma Ray Spectrometer (GRS), respectively. The production time of solar neutrons is better correlated with those of hard X-rays and gamma-rays than with the production time of soft X-rays. The observations of the solar neutrons on the ground have been limited to solar flares with soft X-ray class greater than X8 in former solar cycles. In this cycle, however, neutrons were detected associated with an X2.3 solar flare on November 24, 2000. This is the first report of the detection of solar neutrons on the ground associated with a solar flare with its X-ray class smaller than X8.

The High Energy Transient Explorer 2 is a small scientific satellite designed to detect and localize gamma-ray bursts (GRBs). The coordinates of GRBs detected by HETE-2 will be distributed to interested ground-based observers within seconds of burst detection, thereby allowing detailed observations of the initial phases of GRBs. HETE-2 was launched successfully on October 9, 2000. The GRB positions will start to be delivered after a few months of the complete testing and calibration of the spacecraft system and the science instruments.

An advanced large-scale Pd-based membrane reformer system with a nominal hydrogen production capacity of 40 Nm3/h has been developed. The system demonstrates the potential advantages of the membrane reformer: the simplicity of the system configuration (high purity (99.999% level) hydrogen is produced in a single step from natural gas), its compactness and its high energy efficiency. Other benefits of the membrane reformer include the fact that the CO2 in the off-gas can easily be liquefied and captured, due to the high CO2 concentration of 90%. The results of preliminary operational tests of the membrane reformer show that CO2 emissions decreased by over 50% with only a minor energy loss.

Searches for gamma rays above 100 TeV from SN 1987A and above 50 TeV from Cen X-3 were carried out with an air shower array at Mount Chacaltaya over a period of 3 years. The array, which consists of 13 4 m2 and 28 1 m2 scintillation detectors, was located on a slope of about 30i facing southward to e†ectively observe air showers coming from the directions of these sources. In the analysis, a selection by shower age parameter was applied to reduce the background due to showers initiated by protons or nuclei. No signi-cant excess of gamma rays (and/or neutral particles) from these sources was found; our upper limits on the Nux of gamma rays above 100 TeV from SN 1987A and above 50 TeV from Cen X-3 are 2.2 ) 10~13 and 3.5 ) 10~13 photons cm~2 s~1 (95% con-dence level), respectively. Subject headings: gamma rays: observations E stars: individual (Centaurus X-3) E supernovae: individual(SN 1987A)

We have operated a small air-shower array at Mount Chacaltaya in Bolivia since September 1987 and have observed air showers with primary energies above 2.0 × 1013 eV. This array consists of thirty-three unshielded scintillation detectors and a shielded scintillation detector. The unshielded detectors are installed over an almost flat field of approximately 8 × 103m2 area, while the shielded detector is located at the array center. In the present paper, we report both the details and the operation of this array and the analysis method for the observed data. Furthermore, we have simulated air showers with a Monte Carlo technique. Then, analyzing these air showers, we examine the performance of our array, that is, the accuracy in determination of the electron sizes and the arrival directions of observed air showers.

Immunoreactivities of beta/A4 amyloid precursor protein (APP) and soluble derivative of APP (APPs) were determined in the hippocampus and the striatum of reserpinized rat brains. Significant decrease of APPs immunoreactivity was observed in the cytosolic fraction of hippocampus, but not of striatum, whereas APP immunoreactivity was found to be increased in the membrane fraction of hippocampus. These findings suggest that processing of APP in hippocampus may be regulated through the monoaminergic signal transduction system.

Purpose There is little knowledge regarding the prevalence of mucosal injury (MI) in Japanese patients receiving antiplatelet therapy. This study estimated the prevalence of gastroduodenal MI in asymptomatic Japanese patients taking antiplatelet agents and nonsteroidal anti-inflammatory drugs (NSAIDs). Methods Among patients who underwent an upper gastrointestinal endoscopy at Teikyo University Hospital (Tokyo, Japan), 382 asymptomatic patients taking either low-dose aspirin, ticlopidine, cilostazol, or other NSAIDs and 119 people not taking any of these agents were included. Endoscopic records were evaluated for the presence of MI. Results Aspirin and NSAIDs users showed a higher prevalence of MI than controls (Aspirin, OR = 2.6 (95% CI = 1.4 - 4.9), NSAIDs, 2.9 (1.4 - 4.4)). Concomitant use of aspirin and NSAIDs increased the prevalence of MI (11.2 (2.8 - 44.8)). Ticlopidine and cilostazol were less likely to cause injury than aspirin and other NSAIDs, the difference remained insignificant due to small sample number (ticlopidine, 0.8 (0.2 - 4.0), cilostazol, 1.3 (0.3 - 4.8)). Conclusions In asymptomatic Japanese patients receiving low-dose aspirin, the prevalence of the gastroduodenal MI was the same as that in patients taking NSAIDs and higher than that in controls.

GRB060115 is a long, hard GRB detected with High Energy Transient Explorer 2 (HETE-2). It presents substantial substructures in its light curve. With the spectral analysis of the whole burst and its substructures in the wide energy range of HETE-2 (2-400 keV), we find in the time history of the emission process a hard-to-soft trend first followed by a soft-to-hard evolution. This evolution is not common in GRBs, which generally exhibit only a hard-to-soft evolution. The evolution of the prompt emission of GRB060115 is discussed in this framework.

The case was 54-year-old male with some risks such as chronic heart failure, atrial fibrillation, and liver chirrhosis. He was admitted because of severe back pain and diagnosed as empyema by preoperative thoracentesis. By thoracoscopic procedures under local anesthesia, fibrinopurulent tissues were cleaned as much as possible and 3 of chest tubes were replaced. The final diagnosis was Bacillus cereus pyothorax by bacterial cultures of pleural effusion. Intrathoracic cavity was cleaned with physiological saline solution. The patient made favorable progress and recovered. Thoracoscopic surgery under local anesthesia with thoracic irrigation was so effective and safe methods to control the infection.

The purpose of this study was to clarify the relationship between mechanical stress and tissue response of the contracted knee joint in rats and to propose a new design of contracture correction device for clinical use. Wistar rats were operated on to immobilize their knee joints with a procedure causing periarticular bleeding and were kept in flexed position for 40 days. At day 40, the immobilizing wire was removed, and after day 43, the contracted knee joint had been treated with tunable corrective devices secured by an external fixation method to the rear limb. These devices consisted of four types of motor-driving system which provided several different low-load and continuous stretch torques. Measuring the angle of maximum knee extension, its effectiveness was assessed comparing with a lower load and control group of natural recovery course. The device also had a cyclic joint movement within the acquired range of motion and an oval cam mechanism producing a small distraction force to the joint along its long axis. The results showed that an appropriate range of low-load continuous torque was more effective to correct joint contracture. On the basis of the animal experiment, a new computer-controlled, gas-driven contracture correction device was developed for clinical trial. It was concluded that mechanical application in a condition with low and continuous torque is a useful treatment for fixed joint contracture.

Gamma-Ray Bursts (GRBs) fall into two classes: short-hard and long-soft bursts. The latter are now known to have X-ray and optical afterglows, to occur at cosmological distances in star-forming galaxies, and to be associated with the explosion of massive stars. In contrast, the distance scale, the energy scale, and the progenitors of short bursts have remained a mystery. Here we report the discovery of a short-hard burst whose accurate localization has led to follow-up observations that have identified the X-ray afterglow and (for the first time) the optical afterglow of a short-hard burst. These, in turn, have led to identification of the host galaxy of the burst as a late-type galaxy at z=0.16 showing that at least some short-hard bursts occur at cosmological distances in the outskirts of galaxies, and are likely to be due to the merging of compact binaries., Comment: 19 pages, 4 figures. Submitted to Nature

We report timing properties of Gamma‐ray bursts (GRBs) and X‐ray flashes (XRFs) observed by HETE‐2. We studied 1) duration (or emission time), 2) Variability and 3) spectral lag of the bursts and empirical relations of them. In particular, we examine whether the empirical relations hold or not in lower energy band below 25 keV.

The Japanese Virtual Observatory (JVO) aims to provide astronomers to access federated astronomical databases (especially SUBARU, Nobeyama and ALMA) and data analysis environment by using the grid technology. We defined a unified query language to access federated astronomical databases, the JVOQL, and constructed a prototype of the JVO. We adopted Globus Tool Kit 2 (GTK2) in this prototype to see its effectiveness in VO type application, especially for remote operations and file transfers, and UDDI for looking up services. We found that the system worked as we had expected, however, it took very long to initiate each grid process. Thus we replaced the GTK2 with a tool distributed by NSF middleware initiative, and shortened the polling intervals of the job-manager from 30 seconds to 3 seconds. As a result, the serious problem has been partially resolved - the elapsed time for a query became about a half compared with the previous one.

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.

During its >2.5 years of operation, the High Energy Transient Explorer (HETE‐2) has detected nearly 300 GRBs, over 800 XRBs, and ∼50 bursts from SGRs in on‐orbit operations and sophisticated ground searches of archived data. In addition to these bursts, there have been over 1500 other triggers detected using on‐board or ground algorithms, hundreds of which are as yet unidentified and may come from cosmic sources. We have developed the HETE Burst Catalog as a means of organizing and analyzing the data from these nearly 3000 triggers in a systematic way. We present preliminary results from the HETE burst catalog.

The High Energy Transient Explorer (HETE‐2) has been in orbit for nearly three years. After a slow startup, the operation of the spacecraft and its instrumentation is now stable and efficient. GRBs are being localized at a rate of ∼25 per year, and the Soft X‐ray Camera (SXC) is determining burst positions with arcminute precision on a regular basis. As described elsewhere in this conference, HETE‐2 has essentially solved the mystery of the “dark bursts” and helped confirm the connection between long GRBs and type Ic supernovae. Because of its excellent low‐energy response, HETE has proven to be a capable detector of X‐ray rich GRBs and X‐ray flashes. In this paper, we give an update on the spacecraft and instruments and describe some of the more significant developments of the last 6‐12 months. We also highlight issues which, although described in part on the HETE web page (http: //space.mit.edu/HETE), may not be clear to many observers.

We present the in-flight calibration results of the detector response matrices of the X-ray instrument, Wide-field X-ray Monitor (WXM), on board the HETE-2 satellite. WXM consists of four one-dimensional position-sensitive proportional counters and two sets of one-dimensional coded aperture. Its energy range is 2-25 keV.The detector response matrix (DRM) of WXM is calculated numerically using the ground measurements for each anode wire. It is then calibrated with the observation of the Crab nebula in December 2001 and January 2002. The spectral parameters and the normalization of the spectra are investigated at various incident angles, and compared with the known values in literature. With the current DRM, the derived spectral parameters are mostly consistent with the values in literature, expect for 10-20% uncertainty in normalization for individual anode wires, and at large incidence angles.

One of the primary goals of HETE‐2 is the spectroscopy of the prompt emission of gamma‐ray bursts (GRBs) in a wide energy range. A large overlapping energy range of WXM and FREGATE ensures reliable spectral measurements. Thanks to the enhanced sensitivity in the X‐ray range, HETE‐2 has detected large numbers of X‐ray rich events in addition to the classical GRBs. We have examined the spectral properties of these cosmological bursts localized with HETE‐2. They have much variety in their properties, with the spectral peak energy ranging from a few keV to ∼400 keV, and the gamma‐ray (30–400 keV) fluence from ∼ 10 −8 to ∼ 10−4 erg cm−2. According to the ratio of fluence in the X‐ray range (2–30 keV) to that in the gamma‐ray range (30–400 keV), we have classified the localized cosmological bursts into three classes, hard GRBs, X‐ray rich GRBs and X‐ray flashes. When the nature of the X‐ray rich GRBs and X‐ray flashes are studied systematically, we find that they have many properties in common with the classica...

Spectroscopic and spectropolarimetric observations of SN 2003dh/GRB 030329 obtained in 2003 May using the Subaru 8.2 m telescope are presented. The properties of the SN are investigated through a comparison with spectra of the Type Ic hypernovae SNe 1997ef and 1998bw. (Hypernovae being a tentatively defined class of SNe with very broad absorption features: these features suggest a large velocity of the ejected material and possibly a large explosion kinetic energy.) Comparison with spectra of other hypernovae shows that the spectrum of SN 2003dh obtained on 2003 May 8 and 9, i.e., 34-35 rest-frame days after the GRB (for z=0.1685), are similar to those of SN 1997ef obtained ~34-42 days after the fiducial time of explosion of that SN. The match with SN 1998bw spectra is not as good (at rest 7300-8000 A, but again spectra obtained ~33-43 days after GRB 980425 are preferred. This indicates that the SN may have intermediate properties between SNe 1997ef and 1998bw. Based on the analogy with the other hypernovae, the time of explosion of SN 2003dh is then constrained to be between -8 and +2 days of the GRB. The Si and O P-Cygni lines of SN 2003dh seem comparable to those of SN 1997ef, which suggests that the ejected mass in SN 2003dh may match that in SN 1997ef. Polarization was marginally detected at optical wavelengths. This is consistent with measurements of the late afterglow, implying that it mostly originated in the interstellar medium of the host galaxy., Comment: 7 pages, 4 figures, uses emulateapj5.sty, accepted for puclication in ApJL

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., 21 pages, 4 figures, accepted by ApJ, abstract. condensed; revised

The Wide‐field X‐ray Monitor (WXM) is one of the three main scientific instruments on HETE‐2, and is designed to measure the light curves, spectra, and locations of gamma‐ray bursts (GRBs) and other transients in the energy range of 2–25 keV. It consists of Xe‐filled 1‐D position‐sensitive proportional counters equipped with two 1‐D coded apertures in orthogonal directions with a field of view of 40° × 40°. The sophisticated onboard processing allows the localization of GRBs in real time with ∼ 10′ accuracy based on the alerts from FREGATE, the gamma‐ray detector. The WXM also triggers on its own count time history with a flexible algorithm and can localize X‐ray events on various time scales. We present the design and basic characteristics of the detectors, the handling of the data, the in‐flight performance, and some of the early observations.

The High Energy Transient Explorer (HETE ) mission is devoted to the study of gamma‐ray bursts (GRBs) using soft X‐ray, medium X‐ray, and gamma‐ray instruments mounted on a compact spacecraft. The HETE satellite was launched into equatorial orbit on 9 October 2000. A science team from France, Japan, Brazil, India, Italy, and the US is responsible for the HETE mission, which was completed for ∼ 1/3 the cost of a NASA Small Explorer (SMEX). The HETE mission is unique in that it is entirely “self‐contained,” insofar as it relies upon dedicated tracking, data acquisition, mission operations, and data analysis facilities run by members of its international Science Team. A powerful feature of HETE is its potential for localizing GRBs within seconds of the trigger with good precision (∼ 10′) using medium energy X‐rays and, for a subset of bright GRBs, improving the localization to ∼ 30″accuracy using low energy X‐rays. Real‐time GRB localizations are transmitted to ground observers within seconds via a dedicated network of 14 automated “Burst Alert Stations,” thereby allowing prompt optical, IR, and radio follow‐up, leading to the identification of counterparts for a large fraction of HETE ‐localized GRBs. HETE is the only satellite that can provide near‐real time localizations of GRBs, and that can localize GRBs that do not have X‐ray, optical, and radio afterglows, during the next two years. These capabilities are the key to allowing HETE to probe further the unique physics that produces the brightest known photon sources in the universe. To date (December 2002), HETE has produced 31 GRB localizations. Localization accuracies are routinely in the 4′– 20′ range; for the five GRBs with SXC localization, accuracies are ∼1–2′. In addition, HETE has detected ∼ 25 bursts from soft gamma repeaters (SGRs), and >600 X‐ray bursts (XRBs).

The Wide Field X‐ray Monitor (WXM) onboard HETE‐2 spacecraft observes the rectangular sky region of about 1.6 str centered at the anti‐solar direction. SGR1806‐20 and SGR1900+14 were monitored with the WXM instrument for about 60 days between June and August 2001 while they were within the field of view. We have firmly detected 2 and 4 bursts from SGR1806‐20 and SGR1900+14, respectively. A burst from SGR1900+14 occurred at 2001 July 2, 03:34 UT had a high fluence of ∼ 8 × 10−6 ergs cm−2 (6 – 40 keV) and broad‐band burst spectrum was obtained by WXM and FREGATE (GCN Circular 1078). Here we present preliminary analyses of these bursts, and other ∼20 possible bursts from the SGRs detected by HETE‐2.

Wide field X‐ray Monitor (WXM) of HETE‐2 is designed to localized the GRBs which occurred in its wide field of view (60° × 60°) with 10′ accuracy. In order to maintain such a good accuracy, we have been monitoring the positional response of proportional counter and correcting the change at regular intervals. We also have determined the difference of the alignments between WXM and the optical camera system, which is crucially important for determining the coordinate of the GRBs. The localization accuracy is estimated to be ∼ 3′ for 1 Crab burst with 20 sec duration including the systematic error of 2.2′.

In the period that the Galactic center region was in the field of view of HETE‐2 satellite from May to September 2001, it detected bursts from well‐known X‐ray bursters (XRBs). More than 130 events were localized with the Wide‐Field X‐ray Monitor (WXM) on HETE‐2 in these four months to the XRBs including X 1728‐34, SAX J1750‐29, Aq1 X‐1, NGC 6624, and GS 1826‐238. Localization accuracy is better than 18 arc‐minutes for most of the events. In this paper, we summarize the XRBs detected by HETE‐2 and show the light curves of the several events.

This paper describes the acoustic video-signal transmission system for an autonomous underwater vehicle. The acoustic transmission system can transmit a color image of 160/spl times/120 pixels per one second over 1600 meters in distance. The size and weight of the electronics are very small and light enough to be put in a small AUV. The power consumption, that is less than 20 watts, is small enough for AUVs. The transmission speed is 16,000 BPS. In order to realize this system, quadrature phase-shift-keying, adaptive equalizer, image compression, and error correction code for error free transmissions are employed. A wideband transducer was developed for high-speed transmission. It has a small size, light weight, and high sensitivity. A vertical transmission test was carried out in a depth of 100 meters. As a result of this test, it was found that this system has enough Doppler immunity and can transmit images more than 1600 meters in distance without any errors if the SNR (signal to noise ratio) is greater than 15 dB. In the sea test of our AUV, the images of the sea floor were successfully transmitted. This test was carried out at a depth of 400 meters, and no transmission errors were detected.

This paper describes the outline and the summary of an autonomous underwater robot "AQUA EXPLORER 1000" (AE1000) for inspection of underwater telecommunication cables. AE1000 can find and track buried underwater cables with a cable tracking sensor, and record the view of the seafloor on a built in video cassette recorder (VCR). A high-bit-rate acoustic link for video-signal transmission is also newly developed, that enables the operator to monitor the seafloor in real-time. Five sea trials have been carried out since 1992, in which we succeeded in the continuous tracking of real underwater telecommunication tables over 2.6 kilometers. The object of the project, basic design, performance, and the results of sea trials are discussed.

This paper describes the technology of cable tracking and experimental results with an autonomous underwater vehicle (AUV) called AQUA EXPLORER 1000 (AE1000) that is designed to be able to inspect submarine telecommunication cables at the depth of up to 1000 m. The vehicle can detect the magnetic field induced from a cable with on-board magnetometers and calculate the location of the cable. We discuss the errors of the cable location caused by the magnetic noise and misalignment of the sensor axes. We also describe the attitude of the vehicle that is necessary to record the scene of the cable. In the recent sea test, AE1000 succeeded to find out a submarine cable and to track it autonomously. We report the results of the experiment.

The paper deals with analysis of control performance of an autonomous underwater vehicle named AQUA EXPLORER 1000 (AE1000) for inspection of underwater telecommunication cables up to 1000 m depth, reviewing results of sea trials in autonomous tracking. The control performance of the cable tracking at 40 m water depth, consisting of descent from the surface, cable searching, cable tracking and ascent to the surface, is discussed based on the measured data. Next, the performance of spiral motion control in a limited area from the mother ship, which is an important operation for the AE1000 not to be lost during descent and ascent, is discussed by showing test results. Finally, the performance of the fuzzy controller for cable tracking control in tidal currents is discussed by use of numerical simulation. >

The VENUS project reuses the TPC-2, which is one of the demission submarine coaxial-cable systems, for multi-disciplinary real-time measurements at deep-sea. The VENUS system is comprised of sensors, a junction box, a data-coupling unit, a data-telemetry unit, main coaxial-cables, a shore station, sea-Earth, and a data center. Several new technologies in data communication and deployment of instruments are adopted. There are seven sensor sets, including broadband seismometers, a hydrophone array, etc. By using a submersible, instruments can be connected to junction box through ROV connectors. The power unit is specially designed to keep a constant current due to the constrain by the cable system. The whole system was successfully tested twice in laboratory in 1997. The data obtained by the first station are going to be transmitted to the data center through the shore station. Digital telemetry through the old analog telephone system can provide high accuracy real-time data acquisition.

The VENUS project is a five-year plan between 1995 and 1999 to utilize the retired trans-Pacific telephone cable from Okinawa to Guam Islands for multidisciplinary geo-scientific studies. The first seafloor observatory off Okinawa Island was deployed in March 1998 in the landward slope of Nanseishoto Trench at a depth of 2,200 m. Among several ideas to transmit the data from sophisticated sensors into the cable, such as inductive data coupling system, direct data coupling system was adopted in the VENUS phase I in order to get sufficient power from the cable for the instruments. Integrated seafloor observatory is comprised of broadband and velocity-type seismometers, tsunami pressure gauge, magnetometer, hydrophone array, sub-bottom temperature probe, geo-potential probes, precision transponders for baseline measurement, digital camera, CTD, current meter, etc. These sensors were deployed precisely by JAMSTEC/deep tow and connected with the main cable by manned submersible Shinkai 6500 and ROV Kaiko. In order to carry out underwater works in situ, ROV matable coaxial, electrical and optical connectors were developed. Also, cable cutter and grip were developed for underwater operations by Shinkai 6500. The VENUS project will contribute greatly to expand global seismic network, and to reuse economically retired submarine coaxial and optical telephone cables over the world ocean floor. Also, a revolutional progress is expected in the deep sea technology and deep sea research.

An ocean bottom broadband seismometer (OBBS) was installed 2170 m deep on the slope of the Ryukyu Trench with other sensors through the VENUS project. Prior to the installation of the OBBS unit, the bottom telemetry system, which supplies electrical power to the instruments, telemetry system and cable was installed on the ocean bottom by a method similar to cable repair works. Since broadband seismometers are extremely fragile, it was handled with special care. The installation of the seismometer was done by use of a deep-tow system and the ROV Kaiko-10 K. In September 1999, the OBBS unit was deployed at the target position, at 80-meter from the bottom telemetry system, with several meters allowances using a deep-tow system. To install the instrument at the exact location, the mother ship of the deep-tow system was precisely navigated. The connecting cable and eight weights were also dropped from the deep-tow system. The ROV Kaiko-10 K extended the 100 m-long connecting cable from the seismometer to the junction box and connected it to the junction box. The OBBS unit collected one and half month records. Several significant earthquakes near Japan, in Taiwan and San Francisco have been observed since the installation.

After a long period of quiescence, the soft gamma repeater SGR1900+14 was suddenly reactivated on April 2001. On July 2, 2001, a bright flare emitted by this source triggerred the WXM and FREGATE instruments onboard the HETE-2 satellite. Unlike typical short (0.1 s) and spiky SGRs recurrent bursts, this event features a 4.1 s long main peak, with a sharp rise (50 ms) and a slower cutoff (250 ms). This main peak is followed by a 2 sec decreasing tail. We found no evidence of any precursor or any extended `afterglow' tail to this burst. We present the preliminary spectral fits of the total emission of this flare as observed by the FREGATE instrument between 7 and 150 keV. The best fit is obtained with a model consisting of two blackbody components of temperatures 4.15 keV and 10.4 keV. A thermal bremsstrahlung can not be fitted to this spectrum. We compare these features and the burst energetics with the other strong or giant flares from SGR1900+14., 5 pages, Latex, Woods Hole 2001 GRB conference

MAXI is an X-ray all-sky monitor mission which will be deployed on the Japanese Experiment Module of the International Space Station in 2004. It is designed to monitor X-ray sources by scanning the entire sky every 90 minutes, and can detect X-ray sources of 3 mCrab in one day. Although its instantaneous field of view is limited to narrow fan beams, one can expect ∼5 GRBs to occur in the field of view and ∼25 afterglows to be detected per year.