Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Time Delay in Black Hole Gravitational Lensing as a Distance Estimator   We calculate the time delay between different relativistic images formed by
black hole gravitational lensing in the strong field limit. For spherically
symmetric black holes, it turns out that the time delay between the first two
images is proportional to the minimum impact angle. Their ratio gives a very
interesting and precise measure of the distance of the black hole. Moreover,
using also the separation between the images and their luminosity ratio, it is
possible to extract the mass of the black hole. The time delay for the black
hole at the center of our Galaxy is just few minutes, but for supermassive
black holes with M=10^8 - 10^9 solar masses in the neighbourhood of the Local
Group the time delay amounts to few days, thus being measurable with a good
accuracy.

26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
27
The categories of this paper are: comp-gas
24
The categories of this paper are: dg-ga
11
The categories of this paper are: hep-lat
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
4
The categories of this paper are: cond-mat
16
The categories of this paper are: stat
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph