The recently discovered binary system LB-1 has been reported to contain a \sim 70 M _ { \odot } black hole ( BH ) .
The evidence for the unprecedentedly high mass of the unseen companion comes from reported radial velocity ( RV ) variability of the H \alpha emission line , which has been proposed to originate from an accretion disk around a BH .
We show that there is in fact no evidence for RV variability of the H \alpha emission line , and that its apparent shifts instead originate from shifts in the luminous star ’ s H \alpha absorption line .
If not accounted for , such shifts will always cause a stationary emission line to appear to shift in anti-phase with the luminous star .
We show that once the template spectrum of a B star is subtracted from the observed Keck/HIRES spectra of LB-1 , evidence for RV variability vanishes .
Indeed , the data rule out any periodic variability of the emission line with velocity semi-amplitude K _ { H \alpha } > 1.3 km s ^ { -1 } .
This strongly suggests that the observed H \alpha emission does not originate primarily from an accretion disk around a BH , and thus that the mass ratio can not be constrained from the relative velocity amplitudes of the emission and absorption lines .
The nature of the unseen companion remains uncertain , but a ‘ ‘ normal ’ ’ stellar-mass BH with mass 5 \lesssim M / M _ { \odot } \lesssim 20 seems most plausible .
The H \alpha emission likely originates primarily from circumbinary material , not from either component of the binary .