[[UTAPwiki/セミナー/宇宙物理学セミナー]]

Speaker: Tatsuya Matsumoto

Title: Dynamics of an emission centroid during Sgr A* flares

Abstract: Sgr A* is a supermassive BH in our Galaxy confirmed by long-term monitoring of stellar orbits.
Abstract:
Sgr A* is a supermassive BH in our Galaxy confirmed by long-term monitoring of stellar orbits.
The luminosity of Sgr A* is usually very small (~10^8 times smaller than its Eddington luminosity), but sometimes it rises up suddenly, so-called flare events. Flares are most noticeable in near-infrared and X-ray bands, where the luminosity increases from a quiescent level of ~10^{33-34} erg/s to a peak level of ~10^{35} erg/s. Although several flare models have been proposed, their origin is still uncertain. Recently, the Gravity collaboration carried out an interferometric observations of NIR flares and detected a motion of an emission centroid with an astrometric accuracy of ~10^{-5} arcsecond. They fit the observed trajectory with a circular Kepler orbit and find the best-fit radius of 7-10 gravitational radius. However, their best-fit orbit lies entirely inside of the trajectory because the small radius is required to reproduce the duration.To resolve this problem, we fit the observed trajectory with different models and I will discuss our results.

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