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
-
ALISIO-1, el primer satélite propio del Instituto de Astrofísica de Canarias (IAC), ha iniciado su viaje al espacio este viernes, 1 de diciembre, a bordo de un cohete de SpaceX. El lanzamiento que ha tenido lugar a las 18:19 horas desde la Base Vandenberg de la Fuerza Aérea Estadounidense situada en California (EEUU), se ha desarrollado sin ningún contratiempo El presidente del Gobierno de Canarias, Fernando Clavijo, que ha presidido el lanzamiento del primer satélite canario, ha valorado el exitoso trabajo que viene realizando el Instituto de Astrofísica de Canarias y ha dicho que “sitúa aAdvertised on
-
Members of the different institutions that make up the International Scientific Committee (CCI) of the Canary Islands Observatories met last Tuesday, 31 October, in the island of La Palma. The meeting was attended by Rafael Rebolo, Director of the Instituto de Astrofísica de Canarias (IAC), and Casiana Múñoz, Deputy Director of the IAC. The CCI is the committee created in the International Agreements that established the Canary Islands Observatories for an effective participation of the User Institutions in the adoption of decisions related to the use and improvement of the observatoriesAdvertised on
-
The 19th scientific meeting of CARMENES, a collaboration of more than 100 scientists from 11 Spanish and German institutions aimed at studying extrasolar planets around M-type dwarf stars, the lowest mass stars, was held this week at the IACTEC facilities in La Laguna (Tenerife, Spain). Since it became operational in 2016, CARMENES has analysed more than 360 such stars, leading to the discovery of more than 65 new planets, making it the most efficient instrument and mapper in the study of planets around very low-mass stars, with 30 % of the total number of planets discovered in this rangeAdvertised on