Title: Exploration of the Synchrotron-Compton Transition in PKS 2155-304


Proposal ID: 0120131
Subject category: Extragalactic Object
Principal investigator: Paltani
Institute: Harvard-Smithsonian Center for Astrophysics


Abstract

We propose to perform a single, long observation of the high-energy peaked BL Lac object PKS 2155-304. The aim of the proposal is to use IBIS and SPI to measure accurately the spectral properties of the synchrotron bump up to at least 100 keV, and possibly to detect the low-energy tail of the Compton bump above 200 keV. The Compton bump will be observed simultaneously by AGILE. The goal of the proposal is to obtain the best determination of the spectral energy distribution for a BL Lac object. These observations will be of fundamental importance to constrain the physical and geometrical properties of the emitting region. Other, mostly ground-based, observations are planned. The proposal also puts a strong emphasis on the intra-observation variability properties that will be analyzed in great details owing to the continuous monitoring by ISGRI, Jem-X and OMC. The very dense light curves obtained with these instruments will prove to be of huge importance in assessing the viability of the emission models.