22-24 May 2013
Physics Department, University "La Sapienza", Roma, Italy
Europe/Rome timezone

Gamma-ray observations of Cygnus X-1 in the hard and soft states

23 May 2013, 16:45
15m
Aula Edoardo Amaldi (first floor) (Physics Department, University "La Sapienza", Roma, Italy)

Aula Edoardo Amaldi (first floor)

Physics Department, University "La Sapienza", Roma, Italy

Speaker

Dr Sabina Sabatini (INAF IAPS)

Description

Gamma-ray observations by the AGILE satellite during the period mid-2007-2010 of the black hole binary system Cygnus X-1 will be presented. The source was observed both in the most common hard state and during a remarkably prolonged `soft state' phase (June 2010 -- May 2011). Previous 1--10 MeV observations of Cyg X-1 in this state hinted at a possible existence of a non-thermal particle component with substantial modifications of the Comptonized emission from the inner accretion disk. Our AGILE data provide a significant upper limit for the gamma-ray emission above 100 MeV, excluding the existence of prominent non-thermal emission above 100 MeV during the soft state of Cygnus X-1. We will discuss theoretical implications of our findings in the context of high-energy emission models of black hole accretion. We also discuss possible gamma-ray flares detected by AGILE. In particular, we report a weak but important candidate for enhanced emission which occurred at the end of June 2010 (2010-06-30 10:00 - 2010-07-02 10:00 UT) exactly in coincidence with a hard-to-soft state transition and before an anomalous radio flare.

Primary author

Dr Sabina Sabatini (INAF IAPS)

Presentation Materials