Does the binary system LB-1 host a Black Hole?

Lennon, Daniel J.; Allende-Prieto, Carlos; Bohlin, Ralph C.; Casares, Jorges; Castro, Norberto; Deustua, Susana E.; Dufton, Philip; Gonzalez-Hernandez, Jonay I.; Herrero, Artemio; Maiz Apellaniz, Jesus; Munoz Darias, Teo; Simon-Diaz, Sergio; Smartt, Stephen J.; de Burgos Sierra, Abel
Referencia bibliográfica

HST Proposal

Fecha de publicación:
2
2020
Número de autores
14
Número de autores del IAC
7
Número de citas
0
Número de citas referidas
0
Descripción
It was recently proposed that the Galactic binary system LB-1 hosts an ~8+70 solar mass B-star+black hole (BH) wide binary that is X-ray quiet, strongly challenging the current paradigm for the formation of stellar mass black holes in metal rich environments. This claim was quickly disputed in two ways: The Balmer emission lines originally thought to arise from an accretion disk around the BH have been re-interpreted as a stationary circumbinary disk, hence it is only possible to estimate a minimum mass for the dark companion from the inferred mass of the B-type star. Secondly, detailed non-LTE analyses of the optical spectrum and spectral energy distribution of the B-type star now imply two scenarios for a significantly lower mass of the B-type 'primary': It is found to be either a main sequence B-type star of 3.2+/-2 solar masses or a stripped helium star of 1.1+/-0.5 solar masses, consistent with a 'secondary' mass between approximately 2 and 5 solar masses. The dark secondary could therefore still be a stellar mass BH, making it only the second X-ray quiet star+BH system known, or possibly even a massive neutron star. We propose obtaining an exquisite UV/optical/near-IR flux calibrated spectrum of the system that will provide the pivotal means of discriminating between these two scenarios by tightly constraining the mass and helium abundance of the primary.