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We propose an improved version of the redshift indicator developed by Atteia, which gets rid of the dependence on the burst duration and provides better estimates for high-redshift GRBs. We present first this redshift indicator, then its calibration with HETE-GRBs with known redshifts. We also provide an estimation of the redshift for 59 bursts, and we finally discuss the redshift distribution of HETE-bursts and the possible other applications of this redshift indicator. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Swift has now detected a large enough sample of gamma-ray bursts (GRBs) to allow correlation studies of burst parameters. Such studies of earlier data sets have yielded important results leading to further understanding of burst parameters and classifications. This work focusses on seventeen Swift bursts that have also been detected either by Konus-Wind or HETE-II, providing high energy spectra and fits to Epeak . Eight of these bursts have spectroscopic redshifts and for others we can estimate redshifts using the variability/luminosity relationship. We can also compare Epeak with Eiso, and for those bursts for which a jet break was observed in the afterglow we can derive Eg and test the relationship between Epeak and Eγ . For all bursts we can derive durations and hardness ratios from the prompt emission. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

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. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

It is claimed by many authors that there are tight correlations between the spectral peak energy Ep, and the “brightness” such as isotropic energy Erad, collimation-corrected energy Eγ, or peak luminosity Lp. In many long GRBs, their light curves consist of several pulses or humps, and each pulse has a different spectrum. Using data of multi pulsed GRBs observed by HETE-2, we investigated these relations for each pulse and found it looked to have some correlations. This may imply that each pulse could behave as a single burst. Considering that the GRB rate follow the star formation rate of the Universe, we should have already detected a number of distant GRBs. Some methods are proposed to estimate a redshift by applying the above mentioned correlations. Extending the previous studies, we apply the redshift estimations using Ep-Erad correlation for an individual pulse. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The availability of a few dozen GRB redshifts now allows studies of the intrinsic properties of these high energy transients. Amati et al. recently discovered a correlation between E peak, the intrinsic peak energy of the vfv spectrum, and Eiso, the isotropic equivalent energy radiated by the source. Lamb et al. have shown that HETE-2 data confirm and extend this correlation. We discuss here one of the consequences of this correlation: the existence of a ‘spectral standard candle’, which can be used to construct a simple redshift indicator for GRBs. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

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. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

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. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

A new type of imaging detector, the Soft X-ray Camera (SXC), is now flying on the HETE-2 satellite as part of the instrument suite to detect and localize GRBs. The low point spread function of CCDs combined with a finely ruled and highly aligned coded mask results in a compact instrument (∼ 10 cm on a side) which can localize transients with high precision (∼30 arcseconds) over a large field of view (∼ 1 sr). We present an overview of the design, fabrication, and testing of the SXC. The in-flight performance and capabilities are then presented. Finally, the adverse effects of the space environment (in particular the micrometeorite flux and increased atomic oxygen concentrations during solar maximum) on the SXC, and the steps taken to mitigate these effects are discussed. Both GRBs and XRBs are being routinely localized with high accuracy by the SXC. [ABSTRACT FROM AUTHOR]

We report on the X-ray emission from the shell-like, non-thermal radio source Sgr A East (SNR 000.0+00.0). The X-ray emitting region is concentrated within the central ≃ 2 pc of the larger radio shell. The spectrum shows strong Kα lines from highly ionized ions of S, Ar, Ca, and Fe. The plasma appears to be rich in heavy elements, over-abundant by roughly a factor of four with respect to solar abundances, and shows a spatial gradient of elemental abundance: the spatial distribution of iron is more compact than that of the lighter elements. The X-ray properties support the longstanding hypothesis that Sgr A East is an old supernova remnant (SNR). [ABSTRACT FROM AUTHOR]