8月6日（木）10:00～12:00 VLBIコロキウム 中央棟（南）2F VLBIセミナー室
Aug 6 Thu VLBI Colloquium VLBI Seminar Room, Main Bldg. (South) 2F
- Kotaro Moriyama
- Kyoto university
- method for black-hole spin measurement based on flux variation from an infalling gas ring
- In this presentation, we propose a new method for black hole spin measurement. In this method, we consider a gas blob or ring falling onto a black hole from an inner edge of an accretion disk, keeping its initial orbital angular momentum. We assume that the gas blob or ring emits monochromatic radiation, and carefully examine how it is observed by a distant observer. The radiation from the gas undergoes four relativistic effects: (i) gravitational lensing, (ii) beaming effect, (iii) focusing effect around the photon circular orbit, and (iv) gravitational red-shift. The light curve of the orbiting gas blob is composed of many peaks because of periodic enhancement of the flux due to the effects (i) and (ii). Further, the intensity of each peak first gradually increases with time [due to (iii)] and then rapidly decreases [(iv)], as the gas blob approaches the event horizon. The light curve of the gas ring is equivalent to a superposition of those of the blobs with various initial orbital phases, and so it is continuous and with no peaks. The flux variation timescale depends on the black hole spin and is independent from the inclination angle, while time averaged frequency shift have dependences of both effects. We can thus, in principle, determine spin and inclination angle from observations. The observational implications and future issues are briefly discussed. Furthermore, we consider a new method for inspecting the black hole space-time structure itself by adding space information, i.e. a direct imaging data of gas cloud, to flux variation timescale.
- 名前：酒井 大裕