Engineering topics

Atteia, J.-L.

Publications and source records attributed to Atteia, J.-L..

13 records

NASA NTRS2004

Observations of Gamma-Ray Bursts by HETE-2

The High Energy Transient Explorer 2 (HETE-2), launched in October 2000, is currently localizing gamma-ray bursts (GRBs) at a rate of approximately 20/yr, many in real time. As of August 2003, HETE-2 had localized 43 GRBs; 16 localizations had led to the detection of an X-ray, optical, or radio afterglows. The prompt position notification of HETE-2 enabled probing the nature of so-called "dark bursts" for which no optical afterglows were found despite of accurate localizations. In some cases, the optical afterglow was found to be intrinsically faint , and its flux declined rapidly. In another case, the optical emission was likely to be extinguished by the dust in the vicinity of the GRB source. The bright afterglows of GRB021004 and GRB030329 were observed in unprecedented details by telescopes around the world. Strong evidence for the association of long GRBs with the core-collapse supernovae was found. HETE-2 has localized almost as many X-ray rich GRBs as classical GRBs. The nature of the X-ray rich GRBs and X-ray flashes have been studied systematically with HETE-2, and they are found to have many properties in common with the classical GRBs, suggesting that they are a single phenomenon.

Kawai, N.↗

NASA NTRS1994

Simultaneous observations of gamma-ray bursts with Phebus/Granat and Ulysses GRB

We compare the characteristics of 35 gamma-ray bursts (GRBs) detected simultaneously by Phebus aboard Granat and the Ulysses GRB experiment. Phebus observes a medium to high energy range (100 keV - 100 MeV), while the Ulysses GRB detector is sensitive to lower energy photons (25 - 150 keV). Comparison of the peak counts recorded by these two instruments shows that the variation in burst intensities is more extended for Phebus (above approximately 150 keV) than for Ulysses GRB. This result confirms similar observations from other instruments (Atteia et al. 1991; Mitrofanov et al. 1992; Belli 1992). We discuss the consequences of this behavior for the statistical properties of GRBs, and for the searches for a possible cosmological redshift.

Atteia, J.-L.↗

NASA NTRS1993

Gamma-ray burst observations

The most important observational characteristics of gamma-ray bursts are reviewed, with emphasis on X-ray and gamma-ray data. The observations are used to derive some basic properties of the sources. The sources are found to be isotropically distributed; the burster population is limited in space, and the edge of the distribution is visible.

Atteia, J.-L.↗

NASA NTRS1992

The solar X-ray/cosmic gamma-ray burst experiment aboard Ulysses

The scientific objectives of the Ulysses solar X-ray/cosmic gamma-ray burst experiment, and the unique features of the Ulysses mission which will help to achieve them are described. After a discussion of the special design constraints imposed by the mission, the sensor systems, consisting of two CsI scintillators and two Si surface barrier detectors covering the energy range 5-150 keV are described. Their operating modes and inflight performance are also given.

Hurley, K.↗

NASA NTRS1989

Gamma-ray burster counterparts - Radio

Many observers and theorists have suggested that gamma-ray bursters (GRBs) are related to highly magnetized rotating, neutron stars, in which case an analogy with pulsars implies that GRBs would be prodigious emitters of polarized radio emission during quiescence. The paper reports on a survey conducted with the Very Large Array radio telescope of 10 small GRB error regions for quiescent radio emission at wavelengths of 2, 6, and 20 cm. The sensitivity of the survey varied from 0.1 to 0.8 mJy. The observations did indeed reveal four radio sources inside the GRB error regions.

Schaefer, Bradley E.↗

NASA NTRS1987

Localization, time histories, and energy spectra of a new type of recurrent high-energy transient source

The detection of a recurrent high-energy transient source which is neither a classical X-ray nor a gamma-ray burster, but whose properties are intermediate between the two, is reported. The energy spectra of 12 recurrent events are found to be soft, characterized by kT's of 34-56 keV. The time histories are short with rise and fall times as fast as about 10 ms. The source location is a 0.12 sq deg region about 10 deg from the Galactic center.

Atteia, J.-L.↗

NASA NTRS1987

A new type of repetitive behavior in a high-energy transient

The high-energy burster GB 790107 has been observed to repeat, on the order of 100 times, between August 13, 1978 and June 27, 1986, with most repetitions occurring in the latter part of 1983. Here, these activities are described, discussing intensity and time-of-occurrence information covering a seven-year span of International Cometary Explorer (ICE) data. Arguments for the reality of this activity and its association with the GB 790107 source are presented. A moderately precise location derived from ICE, SMM, Pioneer Venus Orbiter, and Venera 13 Signe data is given and related to the published GB 790107 location.

Laros, J. G.↗

NASA NTRS1987

A second catalog of gamma-ray bursts - 1978-1980 localizations from the interplanetary network

A catalog of 84 gamma-ray bursts which occurred between September 14, 1978 and February 13, 1980 is presented. The data presented consist of earth crossing times, given to about the nearest second, and time histories, in the tens of keV to MeV range, for all 84 events, as well as localizations for 80 of the events. The localizations, derived from arrival-time analysis, are given as single error boxes, double error boxes, or annuli of location, and, where possible, have been compared to the Konus localizations. They range in size from less than a square arcminute to over 1000 square degrees. The fluences of the bursts cataloged are in the range 3 x 10 to the -7th ergs/sq cm and above.

Atteia, J.-L.↗

NASA NTRS1987

Search for optical bursts from gamma-ray bursters. I

Preliminary results of an examination of the Ondrejov and Sonneberg plate collections for possible optical counterparts to gamma-ray bursters are presented. The investigation proceeds in three different directions: (1) time-correlated searches for gamma-ray bursts (GRB) with known positions, (2) time-correlated searches for GRB without know positions, and (3) archival searches. 3 GRB with known positions and 28 GRB without known positions were studied in this way; archival searches representing a total exposure of 2.75 yr were done for 10 GRB positions, with limiting magnitudes for a 1 s flash between 3 and 8. No evidence for true optical images associated with GRB was found. Some statistical conclusions are drawn and the results obtained are discussed.

Hudec, R.↗

NASA NTRS1987

Gamma-ray burster counterparts - Infrared

The discovery of an IR counterpart to a gamma-ray burster (GRB) would be a big step forward in understanding this enigmatic phenomenon. A program of searching for IR emission from the smallest GRB source regions has been initiated. Seven boxes have been searched with ground-based telescopes at a wavelength of 2.2 microns and 23 with the IRAS data base at wavelengths of 12, 25, 60, and 100 microns. No convincing candidates were identified. The most constraining result are for two error boxes where the K-band magnitude are found to be fainter than 19.03. This observation is compared with the flux predicted from either a companion star or an accretion disk. The new IR observations pose serious difficulties for several GRB models.

Schaefer, Bradley E.↗

NASA NTRS1986

Constraints on neutron star models of gamma-burst sources from the Einstein Observatory

Six Einstein observations of five gamma-ray burst sources are presented and discussed. With one possible exception, no point source was detected in any of the observations. The data are interpreted in the framework of neutron star models for gamma bursters. Upper limits are derived for the surface temperatures of the neutron stars assumed to be responsible for the bursts. It is shown that the lack of soft X-ray emission may impose stringent constraints on accretion rates onto neutron stars.

Pizzichini, G.↗

NASA NTRS1986

Search for optical flashes from gamma-ray bursters

Preliminary results of an investigation of the Ondrejov and Sonneberg plate collections for possible optical counterparts to gamma ray bursters (GRBs) are presented. The study proceeds in three directions: as time-correlated searches for GRBs with known positions, as time-correlated searches for GRBs without known positions, and as archival searches. The position of the Perseus flasher was also investigated using 1000 hours of monitoring. No evidence for true optical images associated with GRBs was found. Statistical conclusions are drawn and discussed.

Hudec, R.↗

NASA NTRS1985

Archival searches for optical counterparts to gamma ray bursters

The results of searches of about 1500 h of archival astronomical plates, taken with a variety of instruments at two observatories are reported. The areas of the sky photographed coincided with the positions of ten recently observed gamma ray bursts. The limiting magnitudes of the plates would in most cases have allowed the detection of the type of optical transients recently observed to be associated with gamma-bursters, although no such transients were found. A simple statistical argument is presented which allows confidence limits to be set for the repetition rates of bursters using these or other archival data.

Atteia, J.-L.↗