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
-
An international research, in which the Instituto de Astrofísica de Canarias (IAC) has played a leading role, has found a planet of intermediate size between Earth and Venus orbiting a cool red dwarf 40 light-years away. The new world, named Gliese 12 b, lies within the habitable zone of its star, making it a promising candidate for the James Webb Space Telescope to study its atmosphere. The discovery was made possible thanks to observations from NASA's TESS satellite and other facilities such as CARMENES, at Calar Alto Observatory (CAHA), and MuSCAT2, installed at the Carlos SánchezAdvertised on
-
Gravity has shaped our cosmos. Its attractive influence turned tiny differences in the amount of matter present in the early universe into the sprawling strands of galaxies we see today. A new study using data from the Dark Energy Spectroscopic Instrument (DESI) has traced how this cosmic structure grew over the past 11 billion years, providing the most precise test to date of gravity at very large scales. DESI is an international collaboration of more than 900 researchers, included the Instituto de Astrofísica de Canarias (IAC), from over 70 institutions around the world and is managed byAdvertised on
-
An international scientific team, with the participation of researchers from the Instituto de Astrofísica de Canarias (IAC), has found a new world similar in size to our planet orbiting an ultra-cold red dwarf located about 55 light-years away. Observations from the SPECULOOS telescope network, which includes the ARTEMIS telescope at the Teide Observatory in Tenerife, have made this discovery possible. The Gran Telescopio Canarias (GTC), at the Roque de los Muchachos Observatory on La Palma, has also played a key role in confirming the discovery, providing some of the most accurate groundAdvertised on