Marianne Heida

Ultraluminous X-ray sources

or ULXs are the most extreme X-ray binaries in the Universe. They are the only 'nearby' example of super-Eddington accretion that we know of. Using optical and near-infrared observations from Palomar, Keck and other large telescopes I look for the donor stars in these systems. Together with researchers at Caltech and elsewhere who observe ULXs in X-rays, radio and mid-infrared wavelengths I try to form a more complete picture of these intriguing sources. We want to find out where they fit in the evolution of massive binary star systems, if they can be the progenitors of gravitational wave sources detected by LIGO/VIRGO, and to measure the masses of the black holes in ULXs.

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Galactic X-ray binaries

are where almost all stellar-mass black holes are discovered. We expect that there are around 10 million black holes in the Milky Way, but we have only found a tiny fraction of them and none of those are as massive as some of the black holes found by LIGO. 

I am involved in a large project using the Keck telescopes on Hawaii, the VLT in Chile, and the GTC on La Palma. Together we will try to measure the masses of black holes in X-ray binaries that are hidden behind the dust in the Galactic plane, to see if they harbor these more massive stellar-mass black holes.