Entity

Time filter

Source Type


Gendre B.,ASDC | Atteia J.L.,Toulouse 1 University Capitole | Atteia J.L.,French National Center for Scientific Research | Boer M.,Artemis | And 10 more authors.
Astrophysical Journal | Year: 2012

The Swift burst GRB 110205A was a very bright burst visible in the Northern Hemisphere. GRB 110205A was intrinsically long and very energetic and it occurred in a low-density interstellar medium environment, leading to delayed afterglow emission and a clear temporal separation of the main emitting components: prompt emission, reverse shock, and forward shock. Our observations show several remarkable features of GRB 110205A: the detection of prompt optical emission strongly correlated with the Burst Alert Telescope light curve, with no temporal lag between the two; the absence of correlation of the X-ray emission compared to the optical and high-energy gamma-ray ones during the prompt phase; and a large optical re-brightening after the end of the prompt phase, that we interpret as a signature of the reverse shock. Beyond the pedagogical value offered by the excellent multi-wavelength coverage of a gamma-ray burst with temporally separated radiating components, we discuss several questions raised by our observations: the nature of the prompt optical emission and the spectral evolution of the prompt emission at high energies (from 0.5keV to 150keV); the origin of an X-ray flare at the beginning of the forward shock; and the modeling of the afterglow, including the reverse shock, in the framework of the classical fireball model. © 2012 The American Astronomical Society. All rights reserved. Source


Korsun P.P.,Ukrainian Academy of Sciences | Kulyk I.V.,Ukrainian Academy of Sciences | Ivanova O.V.,Ukrainian Academy of Sciences | Afanasiev V.L.,Russian Academy of Sciences | And 3 more authors.
Icarus | Year: 2010

We present the study of dust environment of dynamically new Comet C/2003 WT42 (LINEAR) based on spectroscopic and photometric observations. The comet was observed before and after the perihelion passage at heliocentric distances from 5.2 to 9.5AU. Although the comet moved beyond the zone where water ice sublimation could be significant, its bright coma and extended dust tail evidenced the high level of physical activity. Afρ values exceeded 3000cm likely reaching its maximum before the perihelion passage. At the same time, the spectrum of the comet did not reveal molecular emission features above the reflected continuum. Reddening of the continuum derived from the cometary spectrum is nonlinear along the dispersion with the steeper slop in the blue region. The pair of the blue and red continuum images was analyzed to estimate a color of the comet. The mean normalized reflectivity gradient derived from the innermost part of the cometary coma equals to 8% per 1000Å that is typical for Oort cloud objects. However, the color map shows that the reddening of the cometary dust varies over the coma increasing to 15% per 1000Å along the tail axis. The photometric images were fitted with a Monte Carlo model to construct the theoretical brightness distribution of the cometary coma and tail and to investigate the development of the cometary activity along the orbit. As the dust particles of distant comets are expected to be icy, we propose here the model, which describes the tail formation taking into account sublimation of grains along their orbits. The chemical composition and structure of these particles are assumed to correspond with Greenberg's interstellar dust model of comet dust. All images were fitted with the close values of the model parameters. According to the results of the modeling, the physical activity of the comet is mainly determined by two active areas with outflows into the wide cones. The obliquity of the rotation axis of the nucleus equals to 20° relative to the comet's orbital plane. The grains occupying the coma and tail are rather large amounting to 1mm in size, with the exponential size distribution of a-4.5. The outflow velocities of the dust particles vary from a few centimeters to tens of meters per second depending on their sizes. Our observations and the model findings evidence that the activity of the nucleus decreased sharply to a low-level phase at the end of April-beginning of May 2007. About 190days later, in the first half of November 2007 the nucleus stopped any activity, however, the remnant tail did not disappear for more than 1.5years at least. © 2010 Elsevier Inc. Source


Mousis O.,University of Franche Comte | Hueso R.,University of the Basque Country | Beaulieu J.-P.,French National Center for Scientific Research | Bouley S.,University Paris - Sud | And 58 more authors.
Experimental Astronomy | Year: 2014

Amateur contributions to professional publications have increased exponentially over the last decades in the field of planetary astronomy. Here we review the different domains of the field in which collaborations between professional and amateur astronomers are effective and regularly lead to scientific publications.We discuss the instruments, detectors, software and methodologies typically used by amateur astronomers to collect the scientific data in the different domains of interest. Amateur contributions to the monitoring of planets and interplanetary matter, characterization of asteroids and comets, as well as the determination of the physical properties of Kuiper Belt Objects and exoplanets are discussed. © 2014, Springer Science+Business Media Dordrecht. Source

Discover hidden collaborations