Opening a high-energy window to stellar phenomena at early epochs.
Our present understanding of how stars and galaxies formed during the first five billion years after the big bang have to a large extent been developed based on observations of distant sources that are magnified by intervening masses acting as “natural telescopes”.
Previous studies have harnessed strong gravitational lensing to probe the distant universe at wavelengths ranging from UV to the mm regime. While lensed active galactic nuclei have been studied at X-ray wavelengths, strong lensing studies of stellar populations in galaxies have never before been extended into the X-ray domain. I will report on recent and ongoing efforts with ITA participation to detect lensed X-ray emission from young, metal-poor stellar populations in galaxies, which have met with some success. Such observations can be used to probe the populations of high mass X-ray binaries and ultraluminous X-ray sources at earlier epochs.
These objects provide a potentially important source of feedback during reionization and may plausibly constitute a progenitor population to the black hole-black hole mergers that have been recently detected by gravitational wave observatories.