摘要:

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. TheHETEsatellite was launched into equatorial orbit on 9 October 2000. A science team from France, Japan, Brazil, India, Italy, and the US is responsible for theHETEmission, which was completed for ∼ 1/3 the cost of a NASA Small Explorer (SMEX). TheHETEmission 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 ofHETEis 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 ofHETE‐localized GRBs.HETEis 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 allowingHETEto probe further the unique physics that produces the brightest known photon sources in the universe. To date (December 2002),HETEhas 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,HETEhas detected ∼ 25 bursts from soft gamma repeaters (SGRs), and >600 X‐ray bursts (XRBs). © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1579291

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The gamma‐ray detector of HETE‐2, called FREGATE, has been designed to detect gamma‐ray bursts in the energy range 6–400 keV. Its main task is to alert the other instruments of the occurrence of a gamma‐ray burst (GRB) and to provide the spectral coverage of the GRB prompt emission in hard X‐rays and soft gamma‐rays. FREGATE was switched on on October 16, 2000, one week after the successful launch of HETE‐2, and has been continuously working since then. We describe here the main characteristics of the instrument, its in‐flight performance and we briefly discuss the first GRB observations. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1579292

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

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. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1579293

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

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. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1579294

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The High Energy Transient Explorer is an unusually small and inexpensive satellite. We will discuss the technology that made this possible. HETE incorporates a robust and efficient power system, a 3‐axis stabilized gyroless control system, and an unusually efficient communication system. We will discuss the advantages this technology offers for the HETE mission, as well as the constraints it imposes and the difficulties it has caused. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1579295

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The FREGATE experiment aboard HETE‐II has been successfully integrated into the Third Interplanetary Network (IPN) of gamma‐ray burst detectors. We show how HETE’s timing has been verified in flight, and discuss what HETE can do for the IPN and vice‐versa. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1579296

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We have developed a simple scheme using a 1‐dimensional discrete wavelet transform, to search for bursts in the ground analysis ofHETEdata. The method, which complements the on‐boardHETEtriggering systems, has proven useful for verifying that these systems are functioning and for detecting untriggered bursts. We outline the method and discuss the results obtained. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1579297

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The HETE Soft X‐ray Camera (SXC) uses X‐ray CCDs and a micro‐fabricated coded aperture mask to image X‐ray sources with sub‐arcminute accuracy over a steradian field of view. Calibration of imaging with observations of the Crab and Sco X‐1 is described. The accuracy of SXC localizations is determined trough observations of known steady and transient galactic X‐ray sources and sensitivity to GRBs is estimated through detections of steady and transient Galactic X‐ray sources. [NB: As of October 2002, the SXC had localized 4 GRBs to arcminute accuracy]. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1579298

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We present the discovery of the optical and radio afterglow of GRB 010921, the first gamma‐ray burst afterglow to be found from a localisation by the High Energy Transient Explorer satellite. Discovery of the afterglow enabled us to determine the redshift,z= 0.45092 from the host galaxy. We expect that the low redshift of this GRB will enable the strongest limits on the detection of an underlying supernova to be made with HST. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1579299

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The FREGATE gamma ray detector of HETE‐2 is sensitive to photons between 6 and 400 keV. This sensitivity range, extended towards low energies, allows us to explore the emission of GRBs in hard X‐rays. We fit the spectra of 23 GRBs with Band’s spectral function in order to derive the distribution of their peak energies (E‐peak). This distribution is then compared with the E‐peak distributions measured by BATSE and GINGA. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1579300

出版商:AIP    

年代:1903

数据来源: AIP