Colloquium on 4 February 2016
Revealing the binary interaction in the puzzling gamma-ray binary HESS J0632+057

Details

Title: Revealing the binary interaction in the puzzling gamma-ray binary HESS J0632+057
Speaker: Yuki Moritani (Kavli IPMU, Japan)
Date: Thursday, 4 February 2016
Time: 11:00 - 12:00
Venue: SAAO Auditorium

Abstract

The gamma-ray binaries, a relatively newly identified subclass of X-ray binaries, show variable emissions in a wide range of energy bands, from radio to the TeV gamma-rays. Currently, 5 systems are classified as gamma-ray binaries, among which 4 systems have the compact object of unknown nature, whilst their optical counterparts are well-known as massive stars (M > 10 M_sun) with circumstellar disks or strong stellar winds. Despite plenty of both theoretical and observational studies, the nature of the compact object is still under discussion for four systems. Hence the mechanisms for particle acceleration and very high-energy emissions are still one of the big challenges of the this field. We have monitored gamma-ray binaries to probe the nature of the compact object and detailed binary interaction, focusing on the role of the massive star in the interaction. In particular, I’ll show some results of our monitoring about HESS J0632+057 in the seminar. This system exhibits puzzling X-ray and gamma-ray light curves – during one orbital cycle, there are two outbursts apart from periastron and a “dip” around apastron. This makes it more difficult to study the system based on a simple model. Our optical spectroscopic monitoring, however, gives evidence that the compact object is a pulsar.

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