The mystery of the MeV gamma-ray emission from gamma-ray binary systems: Dr. Hiroki Yoneda (RIKEN)

ICRR Seminar

 Date&Time October 23, 2020 15:30-17:00
 Speaker Dr. Hiroki Yoneda (RIKEN)
 Title“The mystery of the MeV gamma-ray emission from gamma-ray binary systems”
 AbstractFrom the middle of the 2000s, a new class of compact binary systems is established, so-called gamma-ray binary systems. They show non-thermal emission peaking above 1 MeV in their SEDs, which is completely different from X-ray binaries. This feature indicates that particle acceleration takes place in these binaries, however, the physical mechanism of their activities is still unclear. In this talk, I will report our recent results of X-ray/gamma-ray observations of the brightest gamma-ray binary system LS 5039: 1) LS 5039 has at least four spectral components from X-ray to TeV. The dominant MeV gamma-ray component indicates a more efficient acceleration than Fermi acceleration. 2) A sign of pulsation was found in the hard X-ray emission with ∼3σ. If it is real, the period and its derivative suggest that the compact object is a magnetar. Based on these results, I also will explain a new acceleration scenario for this object: LS 5039 contains a magnetar, and particles are accelerated via magnetic reconnection close to the magnetar.