22–25 avr. 2008
Ecole Polytechnique
Fuseau horaire Europe/Paris
Les blazars sont connus comme étant variables sur différentes échelles de temps, allant des temps courts (entre la minute et le jour) aux longs (entre la semaine et l'année). Différents modèles existent pour expliquer les mécanismes à l'origine de la variabilité observée, et les identifier a été jusque là très difficile. Une grande gamme d'outils sont utlilsés pour définir et caractériser la variabilité, avec des limitations dépendant de la méthode d'analyse et l'uniformité de l'observation. Nous prévoyons plusieurs exposés de synthèse sur la variabilité des blazars, dépendant de la longueur d'onde des observations, allant des ondes radio aux Très Hautes Energies, avec une mention particulière pour les résultats issus des télescopes à effet Cherenkov atmosphériques qui mesurent les temps caractéristiques les plus courts. Les exposés donneront une meilleure compréhension de leurs fluctuations et leurs spectres de puissance, les asymétries dans les courbes de lumière, leur possible origine intrinsèque ou extrinsèque, mais aussi les limitations des méthodes d'analyse. L'objectif principal du colloque est d'avoir une vue globale de la variabilité dans le spectre électromagnétique des blazars, et de comprendre quelles sont les caractéristiques fondamentales (échelles de temps, distributions de puissance), les corrélations, et quelle physique sous-jacente peut être mise en évidence avec la gérération actuelle d'instruments.

En-dehors des exposés invités, beacoup de temps sera consacré aux posters pour lesquels nous attendons des contributions, et qui seront également publiés sous forme de compte-rendu de conférence dans PoS - Proceedings of Science

It has been known for a long time that blazars are variable, both on short (minutes to days) and long (weeks to years) timescales. Various models exist to explain the mechanisms causing variability, and disentangling them has also been particularly hard. A wide variety of tools are used to define and characterize variability, with varying limitations depending on the analysis method and observation uniformity. We plan to have several wavelength-dependent review talks about variability of blazars, ranging from radio to Very High Energy wavelengths, with a special emphasis on Atmospheric Cherenkov Telescope results - and possibly from GLAST - where the timescales have been the shortest. A better view of their fluctuations and power spectra, flare asymmetries in lightcurves, their possible intrinsic or extrinsic origin, as well as different talks on analysis methods strengths and limitations. The main objective of the meeting is to have a view across the spectrum of what the relevant characteristics are (timescales, power distributions), their correlations, the caveats of their assessment, and what underlying physics can realistically be probed with the current generation of instruments.

Besides the invited talks, plenty of time will be devoted to Poster sessions for which contributions are welcomed! All contributions will be published as proceedings (probably with PoS - Proceedings of Science)

In order to estimate the attendance, and hence define the workshop fee, we strongly encourage potential participants to pre-register now on the website. The pre-registration is also necessary to give your intended contribution (poster or not). Given the limited seating capacity we might stop registrations once the capacity limit is reached.

Commence le
Finit le
Europe/Paris
Ecole Polytechnique
Amphitheater Becquerel
Palaiseau
Pre-register here:
http://polywww.in2p3.fr/blazars/

Ecole Polytechnique can be accessed through the express regional metro (RER) line B from Paris, but also from Roissy-Charles-de-Gaulle Airport and from Orly Airport (via the VAL automatic metro connecting Orly to the RER station ANTONY). You should get down at Massy-Palaiseau. Panels on the platform indicate the stations at which the current train will stop; you should check that Massy-Palaiseau is one of them. In Massy-Palaiseau, take the regional bus 91-06 which brings you to Ecole Polytechnique within 10 minutes. There are several bus stops within the Ecole. We recommend to get down at "Chemin de Lozère", the closest to the auditorium. There the way to the auditorium "Becquerel" (located in the main hall) will be indicated by arrows.

For the more sporty, it is possible to avoid the bus: continue a few more stops on the RER-B line to the "Lozère" station (check on the platform that the train goes beyond Massy-Palaiseau and stops at "Lozère"). There, take the underground passage across the railway and follow the street facing the exit and going up the slope for about 100m; then, take the path prolongating the street, eventually followed by steps; at a bifurcation, a bit later, turn left and use the more irregular steps. It takes about 15-20 minutes to get from Lozère station to the plateau and the bus stop "Chemin de Lozère" mentioned above. On the other hand, the Lozère path provides a quick way back to the RER B line in the evening. Maps indicating the "Lozère path" are available on the web site of the campus:

http://www.polytechnique.fr/campus/plans.php