Student Clears Up "Massive" Black Hole Confusion
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Student Clears Up "Massive" Black Hole Confusion:
Black-holes come in various flavors and sizes, from 'small' stellar-mass black holes to supermassive black holes found in the center of galaxies. Stellar-mass black holes are the final remnants of massive stars, born more than 20 to 30 times the mass of our Sun and should only form in certain mass ranges according to current theory. In this context, the claimed discovery, published in the distinguished journal Nature in November 2019, of a black hole 70 times more massive than our Sun caught the attention of the astronomical community.
The system in question, LS V +22 25 or LB-1 in short, was claimed to be a double-star system consisting of an 8 solar mass star and a 70 solar mass black hole that orbit around one another in just 80 days, very much the same way as planets orbit around stars. The data used in the original study showed two spectral signatures that moved in different ways: one clear signature belonging to the star and another, more subtle, that was interpreted as belonging to material around the black hole, thus tracing its orbital motion. Based on the motion of these two signatures, the original authors reached their controversial conclusion.
"A stellar black hole this massive challenges everything we know about massive star evolution," says Michael Abdul-Masih, a PhD student from the KU Leuven Institute of Astronomy in Belgium. "Theory tells us that in this mass range, when a star dies it should completely annihilate itself without leaving anything behind, and certainly not such a massive black hole."
The interpretation of the second signature has since come under scrutiny. Using higher-resolution data from the Flemish-funded Mercator Telescope on the island of La Palma (Spain), the KU Leuven team ran several simulations and concluded that the original interpretation of the system was in fact incorrect.
Journal References:
Michael Abdul-Masih, Gareth Banyard, Julia Bodensteiner, et al. On the signature of a 70-solar-mass black hole in LB-1, Nature (DOI: 10.1038/s41586-020-2216-x)
Jifeng Liu, Haotong Zhang, Andrew W. Howard, et al. A wide star-black-hole binary system from radial-velocity measurements, Nature (DOI: 10.1038/s41586-019-1766-2)
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