# 28th Texas Symposium on Relativistic Astrophysics

Dec 13 – 18, 2015
International Conference Centre Geneva
Europe/Zurich timezone

## How the observational quantities of strong gravitational lens effect depend on BH's mass and spin

Dec 17, 2015, 2:00 PM
21m
Level -1, Room 16 (International Conference Centre Geneva)

### Level -1, Room 16

#### International Conference Centre Geneva

17 Rue de Varembé, 1211 Geneva

### Speaker

Hiromi Saida (Daido University)

### Description

According to the general relativity (GR), the black hole (BH) is characterized by three parameters: mass $M$, spin angular momentum $J$ and electric charge $Q$. In real cases, the charge is expected to be zero, $Q=0$. Then, the "BH observation" may be understood as the measurement of $M$ and $J$ through a direct observation of GR phenomena, for example the strong gravitational lens effect. I am studying how the two parameters $(M,J)$ appear in a time series data (light curve) seen by single telescope observing the strong gravitational lens effect by Kerr BH. The situation treated in my study consists of three parts as follows: (1) If an emission of light with short duration (burst-like emission) occurs near a BH, we focus on two light rays: One light ray propagates from the source to observer along the shortest path which does not wind around the BH ("direct ray" or "zero-winding ray"). Another ray propagates along the secondary short path which winds once around the BH ("secondary ray" or "1-winding ray"). (2) When the observer detects the 0-winding and 1-winding rays by single telescope, he/she can (in principle) readout following two informations from the light curve seen by the telescope: the time delay $\Delta t_{obs}$ between detection time of 0-winding and 1-winding rays, and the ratio of brightness $R_{obs}$ of 0-winding and 1-winding rays. (3) These two parameters $(\Delta t_{obs} , R_{obs})$ are determined by BH parameters $(M,J)$ and also the position and velocity $(\vec{x},\vec{v})$ of source at the emission. I will report how these quantities $(M,J,\vec{x},\vec{v})$ determine the two observational quantities $(\Delta t_{obs},R_{obs})$. Also, it will be found that the estimated values of $\Delta t_{obs}$ and $R_{obs}$ seem to be detectable by the present telescope capability.

### Primary author

Hiromi Saida (Daido University)