- evn2024@mpifr.de
Support
Contribution
Discovering the quiet side of Black Hole X-ray Binaries: A Systematic Search in Radio Surveys
Content
Black hole X-ray binaries (BHXBs) are stellar-mass black holes in binary systems with stars, serving as laboratories for studying various astrophysical phenomena such as accretion-outflow mechanisms, jet launching processes, and binary evolution. With approximately 70 known systems in our Galaxy and 2-3 new discoveries annually, most studies focus on systems detected during outbursts when sudden changes in accretion rates illuminate them across the electromagnetic spectrum. This biases our understanding of BHXB behavior toward systems undergoing outbursts, whereas it is known that the systems spend most of their life in a quiescent, quiet state. In this talk, I'll demonstrate the effectiveness of measuring proper motions of variable radio sources from wide-field surveys to select compact Galactic targets and find potential quiescent BHXB candidates or other unknown radio transients. Using the Very Long Baseline Array (VLBA), we observed 33 highly variable radio sources, detecting 14 on one or more epochs, with no optical, X-ray or infrared counterparts found. Among the detected targets, we identified five Galactic candidates for quiescent BHXBs, while only one such system had been known prior to this study. This illustrates the potential of systematic searches in radio surveys, archival and upcoming, to expand the population of quiescent BHXBs and discover new types of exotic radio transients.