The black hole at the galactic center as a possible retro-lens for the S2 orbiting star

Free access article

Issue		A&A Volume 409, Number 3, October III 2003


Page(s)		809 - 812
Section		Cosmology
DOI		http://dx.doi.org/10.1051/0004-6361:20031137

A&A 409, 809-812 (2003)
DOI: 10.1051/0004-6361:20031137

The black hole at the galactic center as a possible retro-lens for the S2 orbiting star

F. De Paolis¹, A. Geralico^{1, 2}, G. Ingrosso¹ and A. A. Nucita¹

¹ Dipartimento di Fisica, Università di Lecce, and INFN, Sezione di Lecce, CP 193, 73100 Lecce, Italy
² International Center for Relativistic Astrophysics - I.C.R.A., University of Rome "La Sapienza", 00185 Rome, Italy

(Received 6 June 2003 / Accepted 23 July 2003)

Abstract
Holz & Wheeler (2002) have recently proposed that a Schwarzschild black hole may act as a retro-lens which, if illuminated by a powerful light source, deflects light ray paths to large bending angles and a series of luminous arcs (or rings in the case of aligned objects) centered on the black hole may form. Obviously, the most convenient geometry to get retro-lensing images would be that of a very bright star close to a massive black hole, say the putative ${\sim} 4\times 10^6~ M_{\odot}$ black hole at the galactic center. Recent observations of the galactic center region in the K-band have revealed the presence of a very bright main sequence star (labelled S2) with mass ${\sim} 15~M_{\odot}$ orbiting at close distance (130-1900 AU) from Sgr A ^*. The relatively vicinity of S2 to the central massive black hole may offer a unique laboratory to test the formation of retro-lensing images. The next generation of space-based telescopes in the K-band (like NGST) may have high enough limiting magnitude necessary to observe such retro-lensing images.

Key words: gravitation -- gravitational lensing

Offprint request: F. De Paolis, depaolis@le.infn.it

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