Multiwavelength Identification of Black Hole Candidates in M13

Overview

Dr. Laura Chomiuk Ms. Laura Shishkovsky Michigan State University Department of Physics and Astronomy Finding black holes in globular clusters helps fine-tune models for the causes of gravitational wave events which have been recently detected by the Laser-Interferometer Gravitational-Wave Observatory (LIGO) and helps predict the abundance of black holes in globular clusters. I present the identification of the most promising black hole candidates in the Milky Way globular cluster M13. I utilized source-finding programs in conjunction with X-ray catalogs and radio data from the Karl G. Jansky Very Large Array (VLA), as well as a Hubble Space Telescope image of M13, to identify candidates and determine the likelihood of each being a black hole. The sources I identified most closely match the LR/LX (radio luminosity/X-ray luminosity) correlation of black holes, and the most likely sources also have optical counterparts (which would signify the presence of a companion star in an X-ray binary, indicating the likelihood of the radio/X-ray source being a black hole). These sources have radio luminosities between 5.3 × 1027 and 1.3 × 1028 erg s-1, and have X-ray luminosities between 4.4 × 1030 and 2.6 × 1032 erg s-1, rendering the candidates too X-ray-faint to be neutron stars and too radio-bright to be white dwarfs. Additionally, several radio sources without X-ray matches were observed in both the 5 GHz and 7.4 GHz basebands of the VLA observation; their spectral indices close to zero indicate the possibility of them being black holes.