The first massive compact companion in a wide orbit around a hot subdwarf star

We report the discovery of first hot subdwarf B (sdB) star with a massive compact companion in wide ( P = 892.5 ± 60.2 d) binary system. It was discovered based on an astrometric solution provided by Gaia mission Data Release 3. performed detailed analyses spectral energy distribution (SED) as well spectroscopic follow-up observations and confirm nature visible component sdB star. The is invisible despite its high mass M comp 1.50 −0.45 +0.37 ⊙ . A main sequence this would significantly contribute to SED can be excluded. must object, either white dwarf or neutron Stable Roche lobe overflow likely led stripping red giant formation sdB, exposed helium core giant. Based very preliminary data, we estimate that ∼9% sdBs might formed through new channel. This also prototype for progenitor class supernovae type Ia, which has been predicted theory.