All stellar-mass black holes have hitherto been identified by X-rays emitted from gas that is accreting onto the black hole from a companion star. These systems are all binaries with a black-hole mass that is less than 30 times that of the Sun. Theory predicts, however, that X-ray-emitting systems form a minority of the total population of star–black-hole binaries. When the black hole is not accreting gas, it can be found through radial-velocity measurements of the motion of the companion star. We report here radial-velocity measurements taken over two years of the Galactic B-type star, LB-1. The star was initially discovered during a monitoring campaign with the 4-m telescope LAMOST and subsequently studied in more detail with the 10-m class telescopes GTC and Keck. We find that the motion of the B star and a superimposed Hα emission line (see figure) require the presence of a dark companion with a mass of 68 solar masses, which can only be a black hole. The long orbital period of 78.9 days shows that this is a wide binary system. For comparison, black holes detected in X-ray binaries have masses in the range 5-15 solar masses. On the other hand, gravitational-wave experiments have detected black holes with several tens of solar masses. However, the formation of a ~70 solar mass black hole in a high-metallicity environment is extremely challenging within current stellar evolution theories. This would require a significant reduction in wind mass-loss rates and overcoming the pair-instability supernova phase, which limits the maximum black hole mass to less than ~50 solar masses. Alternatively, the black hole in LB-1 might have formed after a binary black hole merger or other exotic mechanisms.
It may interest you
-
The IAC researcher Susana Iglesias-Groth has discovered the existence of tryptophan, an amino acid essential for the formation of proteins and the develoment of living organisms, within a stellar system in the Perseus Cloud. She did this using data from the Spitzer Space Observatory. The results of this finding are published in the journal Monthly Notices of the Royal Astronomical Society. Tryptophan is one of the 20 amino acids considered essential for the formation of proteins, which are key macromolecules for the development of life on Earth. This amino acid has many spectral features in
Advertised on -
Researchers at the Instituto de Astrofísica de Canarias (IAC) and the University of La Laguna (ULL), publish today in the journal Astronomy & Astrophysics the first results of a detailed study of nearly a thousand blue supergiants in the Milky Way. This is the biggest sample of stars of this type which has been studied until now. The study has used over 15 years of high quality observations taken mainly with the NOT and Mercator telescopes at the Roque de los Muchachos Observatory in La Palma. The analysis of these data will allow researchers to improve their knowledge of the evolution of
Advertised on -
International research, with the participation of the Instituto de Astrofísica de Canarias (IAC), reveals that perturbations in the magnetic fields of galaxies may be related to star formation. The study has mapped the magnetic fields of about fifteen galaxies in the vicinity of the Milky Way. The data were obtained with the HAWC+ instrument on board SOFIA, an airborne infrared telescope on a Boeing 747 that was operational until September 2022. The results are published in The Astrophysical Journal. For decades, astronomers have studied the forces that govern the interior of galaxies -
Advertised on