Massive binaries in the vicinity of Sgr A*

Abstract

A long-term spectroscopic and photometric survey of the most luminous and massive stars in the vicinity of the super-massive black hole Sgr A* revealed two new binaries; a long-period Ofpe/WN9 binary, GCIRS 16NE, with a modest eccentricity of 0.3 and a period of 224 days and an eclipsing Wolf-Rayet binary with a period of 2.3 days. Together with the already identified binary GCIRS 16SW, there are now three confirmed OB/WR binaries in the inner 0.2\,pc of the Galactic Center. Using radial velocity change upper limits, we were able to constrain the spectroscopic binary fraction in the Galactic Center to $F_{\rm SB}=0.27^{+0.29}_{-0.19}$ at a confidence level of 95%, a massive binary fraction similar to that observed in dense clusters. The fraction of eclipsing binaries with photometric amplitudes $\Delta m>0.4$ is $F^{\rm GC}_{\rm EB}=3\pm2%$, which is consistent with local OB star clusters ($F_{\rm EB}=1%$). Overall the Galactic Center binary fraction seems to be close to the binary fraction in comparable young clusters.