Gravitational lensing as a probe of compact object populations in the Galaxy

Abstract

Aims. The population of solitary compact objects in the Galaxy is very difficult to investigate. In this paper we examine the possibility of using microlensing searches to detect and to analyze the properties of solitary black holes and neutron stars. Methods. Evolution of single and binary stars is followed using the StarTrack population synthesis code. The spatial distribution of compact objects in the Galaxy is determined by propagating them in the Galactic gravitational potential. Lensing events are found by tracing individual stars and compact objects. Results. We find that compact object lensing events are concentrated in a region with a radius of ≈5 degrees around the Galactic center. The distribution of masses of the lenses for the models we consider differs, but only slightly, from the underlying mass distribution of compact objects. The expected detection rates are of the order of a few per year.

Statistical Searches for Microlensing Events in Large, Non-Uniformly Sampled Time-Domain Surveys: A Test Using Palomar Transient Factory Data

“…Over the past 20 years, microlensing, in which gravitational lensing causes a transient increase in the flux from a background point source, has been used to search for dark and compact objects (Alcock et al 1993;Os lowski et al 2008;Sartore & Treves 2010), to study Galactic structure and kinematics (Binney et al 2000), to determine the shape of stars (Rattenbury et al 2005), and to identify extrasolar planets (Gaudi 2011, and references therein). Such studies were once limited by the small number of detected events, but thanks to advances in CCD technology and the development of dedicated microlensing surveys, a few thousand events are now observed each year.…”