Extreme amplification regimes of the Schwarzschild gravitational lens

@article{77345,
   author = {Bakala, Pavel and Bakalova, Alena and La Placa, Riccardo and Falanga, Maurizio and Stella, Luigi},
   article_location = {LES ULIS CEDEX A},
   article_number = {May 2023},
   doi = {http://dx.doi.org/10.1051/0004-6361/202245426},
   keywords = {gravitational lensing;strong;black hole physics;methods;analytical},
   language = {eng},
   issn = {0004-6361},
   journal = {ASTRONOMY & ASTROPHYSICS},
   title = {Extreme amplification regimes of the Schwarzschild gravitational lens},
   url = {https://www.aanda.org/articles/aa/full_html/2023/05/aa45426-22/aa45426-22.html},
   volume = {673},
   year = {2023}
}

TY  - JOUR
ID  - 77345
AU  - Bakala, Pavel - Bakalova, Alena - La Placa, Riccardo - Falanga, Maurizio - Stella, Luigi
PY  - 2023
TI  - Extreme amplification regimes of the Schwarzschild gravitational lens
JF  - ASTRONOMY & ASTROPHYSICS
VL  - 673
IS  - May 2023
SP  - "A164-1"-"A164-13"
EP  - "A164-1"-"A164-13"
PB  - EDP SCIENCES S A
SN  - 00046361
KW  - gravitational lensing;strong;black hole physics;methods;analytical
UR  - https://www.aanda.org/articles/aa/full_html/2023/05/aa45426-22/aa45426-22.html
N2  - We investigated a complete set of relativistic images of a small source located at an arbitrary distance from a Schwarzschild black hole gravitational lens. This paper offers a description of a simple and efficient fully relativistic method for calculating the bolometric intensity amplification. We focused our analysis primarily on sources located at small radii and close angular distance from the caustic line, both behind and in front of the compact lens. We term the corresponding large deflection regime 'extreme lensing'. We approximated the regime of fully-relativistic, extreme amplification of point sources by simple analytical formulae valid over a wide range of source distances. Using such approximations, we also derived formulae for the maximum amplification of extended sources close to or intercepted by the caustic line. Simple analytical approximations of the time delay between the brightest consecutive images in extreme amplification regimes are also presented.
ER  - 

BAKALA, Pavel, Alena BAKALOVA, Riccardo LA PLACA, Maurizio FALANGA and Luigi STELLA. Extreme amplification regimes of the Schwarzschild gravitational lens. \textit{ASTRONOMY \&{}amp; ASTROPHYSICS}. LES ULIS CEDEX A: EDP SCIENCES S A, 2023, vol.~673, May 2023, p.~''A164-1''-''A164-13'', 13 pp. ISSN~0004-6361. Available from: https://dx.doi.org/10.1051/0004-6361/202245426.