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Search Results: 1 - 10 of 448553 matches for " J-L Atteia "
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A simple empirical redshift indicator for gamma-ray bursts
J-L Atteia
Physics , 2003, DOI: 10.1051/0004-6361:20030958
Abstract: We propose a new empirical redshift indicator for gamma-ray bursts. This indicator is easily computed from the gamma-ray burst spectral parameters, and its duration, and it provides ``pseudo-redshifts'' accurate to a factor two. Possible applications of this redshift indicator are briefly discussed.
Gamma-ray bursts: towards a standard candle luminosity
J-L. Atteia
Physics , 1997,
Abstract: It is usual, in gamma-ray burst (GRB) studies, to compare the average properties of bright and faint GRBs, with the assumption that brightness classes reflect distance classes. When brightness is intented to reflect the distance to the sources, it is nevertheless important to use a quantity with a small intrinsic dispersion. We propose here a method to compare the intrinsic dispersion of various measures of GRB brightness. This method assumes that nearby bursters are homogeneously distributed in an Euclidean space with no density or luminosity evolution. We then use it to compare 5 measures of GRB brightness in the BATSE Catalog. Our analysis reveals that better (i.e. less dispersed) measures of brightness are obtained at low energy and that GRBs are much closer to standard candles below 100 keV than above. We suggest that a beaming of the emission above 100 keV could explain this behaviour.
Choosing a measure of GRB brightness that approaches a standard candle
J-L. Atteia
Physics , 1997, DOI: 10.1063/1.55422
Abstract: Studies using the GRB brightness as a distance indicator require a measure of brightness with a small intrinsic dispersion (close to a standard candle). There is unfortunately no general agreement on the definition of such a quantity. We show here that the comparison of the size-frequency curves obtained with various measures of brightness can be used to select the quantity which is closer to a standard candle. Our method relies on a few general assumptions on the burster spatial distribution, namely that nearby bursters are homogeneously distributed in an Euclidean space with no density or luminosity evolution. We apply it to 5 measures of GRB brightness in the Current BATSE Catalog and we find that the GRB size-frequency distribution depends significantly on the energy window used to measure the GRB brightness. The influence of the time window being, in comparison, negligible. Our method suggests that the best distance indicator in this Catalog is the fluence measured below 100 keV, indicating that GRB luminosities have a smaller intrinsic dispersion below 100 keV than above.
Are bright gamma-ray bursts a fair sample ?
J-L. Atteia
Physics , 1999,
Abstract: We conjecture that bright gamma-ray bursts (GRBs) are bright because they come from sources which are intrinsically over luminous and not because they come from nearby sources. We show that this hypothesis is supported by theoretical and observational arguments and that it explains some well-known properties of GRBs such as their Hardness-Intensity Correlation or the No-Host problem. We discuss the consequences of this hypothesis on our understanding of the properties of the GRB population.
The Epeak-Eiso relation revisited with Fermi GRBs: Resolving a long-standing debate?
V. Heussaff,J-L. Atteia,Y. Zolnierowski
Physics , 2013, DOI: 10.1051/0004-6361/201321528
Abstract: We used a sample of GRBs detected by Fermi and Swift to reanalyze the correlation discovered by Amati et al. (2002) between Epi, the peak energy of the prompt GRB emission, and Eiso, the energy released by the GRB assuming isotropic emission. This correlation has been disputed by various authors, and our aim is to assess whether it is an intrinsic GRB property or the consequence of selection effects. We constructed a sample of Fermi GRBs with homogeneous selection criteria, and we studied their distribution in the Epi-Eiso plane. Our sample is made of 43 GRBs with a redshift and 243 GRBs without a redshift. We show that GRBs with a redshift follow a broad Epi-Eiso relation, while GRBs without a redshift show several outliers. We use these samples to discuss the impact of selection effects associated with GRB detection and with redshift measurement. We find that the Epi-Eiso relation is partly due to intrinsic GRB properties and partly due to selection effects. The lower right boundary of the Epi-Eiso relation stems from a true lack of luminous GRBs with low Epi. In contrast, the upper left boundary is attributed to selection effects acting against the detection GRBs with low Eiso and large Epi that appear to have a lower signal-to-noise ratio. In addition, we demonstrate that GRBs with and without a redshift follow different distributions in the Epi-Eiso plane. GRBs with a redshift are concentrated near the lower right boundary of the Epi-Eiso relation. This suggests that it is easier to measure the redshift of GRBs close to the lower Epi-Eiso boundary. In this context, we attribute the controversy about the reality of the Amati relation to the complex nature of this relation resulting from the combination of a true physical boundary and biases favoring the detection and the measurement of the redshift of GRBs located close to this boundary.
Evidence for a Fast Decline in the Progenitor Population of Gamma Ray Bursts and the Nature of their Origin
B. E. Stern,J-L. Atteia,K. Hurley
Physics , 2002, DOI: 10.1086/342467
Abstract: We show that the source population of long gamma-ray bursts (GRBs) has declined by at least a factor of 12 (at the 90% confidence level) since the early stages of the Universe ($z \sim 2 - 3$). This result has been obtained using the combined BATSE and \it Ulysses \rm GRB brightness distribution and the detection of four GRBs with known redshifts brighter than 10$^{52}$ erg s$^{-1}$ in the 50 - 300 keV range at their peak. The data indicate that the decline of the GRB source population is as fast as, or even faster than, the measured decline of the star formation rate. Models for the evolution of neutron star binaries predict a significantly larger number of apparently bright GRBs than observed. Thus our results give independent support to the hypernova model, which naturally explains the fast decline in the progenitor population.
Connecting Prompt and Afterglow GRB emission I. Investigating the impact of optical selection effects in the Epi - Eiso plane
D. Turpin,V. Heussaff,J. -P. Dezalay,J-L. Atteia,A. Klotz,D. Dornic
Physics , 2015,
Abstract: Measuring GRB properties in their rest-frame is crucial to understand the physics at work in gamma-ray bursts. This can only be done for GRBs with known redshift. Since redshifts are usually measured from the optical spectrum of the afterglow, correlations between prompt and afterglow emissions may introduce biases in the distribution of rest-frame properties of the prompt emission, especially considering that we measure the redshift of only one third of Swift GRBs. In this paper we study the brightness of optical GRB afterglows and the role of optical selection effects in the distribution of various intrinsic properties of GRBs and on the Epi - Eiso relation discovered by Amati et al. (2002). Our analysis is based on a sample of 85 GRBs with good optical follow-up and well measured prompt emission. 71 of them have a measure of redshift and 14 have no redshift. We discuss the connection between the location of GRBs in the Epi-Eiso plane and their optical brightness measured two hours after the trigger in the GRB rest frame. We show that the brightness of GRBs in our sample is mainly driven by their intrinsic luminosity and depends only slightly on their redshift. We also show that GRBs with faint afterglows are preferentially located in the upper part of the Epi-Eiso plane. This optical selection effect favors the detection of GRBs with bright afterglows located below the best fit Epi - Eiso relation whose redshift is easily measurable. We conclude that the distributions of prompt GRB properties in the rest frame undergo selection effects due to the need to measure the redshift from the optical afterglow emission. These biases put significant uncertanties when interpreting the statistical studies of GRB properties in the rest frame. We show that the Epi - Eiso relation is not immune to these selection effects.
In-flight verification of the FREGATE spectral response
J-F. Olive,J-P. Dezalay,J-L. Atteia,C. Barraud,N. Butler,G. B. Crew,J. Doty,G. Ricker,R. Vanderspek
Physics , 2002, DOI: 10.1063/1.1579308
Abstract: We present the first results of the in-flight validation of the spectral response of the FREGATE X/gamma detectors on-board the HETE-2 satellite. This validation uses the Crab pulsar and nebula as reference spectra.
FREGATE observation of a strong burst from SGR1900+14
J-F. Olive,K. Hurley,J-P. Dezalay,J-L. Atteia,C. Barraud,N. Butler,G. B. Crew,J. Doty,G. Ricker,R. Vanderspek
Physics , 2002, DOI: 10.1063/1.1579307
Abstract: 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.
Limits on the early afterglow phase of gamma-ray burst sources from TAROT-1
M Boer,J-L Atteia,M Bringer,B Gendre,A Klotz,R Malina,J-A de Freitas Pacheco,H Pedersen
Physics , 2001, DOI: 10.1051/0004-6361:20011203
Abstract: The T\'elescope \`a Action Rapide pour les Objets Transitoires (TAROT-1) has as prime objective the observation of the prompt and delayed emission of cosmic gamma-ray bursts (GRBs). We have performed a search for optical emission from 6 GRBs detected by BATSE. The positioning error circle was fully covered within typically thirty minutes after the trigger. No detection of the early afterglow phase was made, and magnitude limits in the range of $ \mathrm{m}_{\mathrm{R}} = 13-15 $ were estimated using 20s exposures. These limits are compared to optical afterglow data obtained in later phases and the results are interpreted in terms of source distances. They correspond to a median redshift of z = 0.5. With HETE-2 and the planned instrument upgrade, TAROT-1 will be able to detect the early optical emission of GRBs up to a redshift of the order of 5.
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