Updated radial velocities and new constraints on the nature of the unseen source in NGC1850 BH1

A black hole candidate orbiting a luminous star in the Large Magellanic Cloud young cluster NGC 1850 ($\sim100$Myr) has recently been reported based on radial velocity and light curve modelling. Subsequently, an alternative explanation suggested for system: bloated post-mass transfer secondary (M$_{\rm initial} \sim 4-5M_{\odot}$, M$_{\rm current} 1-2M_{\odot}$) with more massive, yet companion (the primary). Upon reanalysis of MUSE spectra, we found that variations originally were underestimated ($K_{\rm 2,revised} = 176\pm3$km/s vs $K_{\rm 2,original} 140\pm3$km/s) because weighting scheme adopted full-spectrum fitting analysis. The increased semi-amplitude translates into system mass function larger than previously deduced ($f_{\rm revised}$=2.83$M_{\odot}$ $f_{\rm original}$=1.42$M_{\odot}$). By exploiting spectral disentangling technique, place upper limit 10\% primary source to observed optical NGC1850 BH1, assuming are only components contributing system. Furthermore, by analysing archival near-infrared data, find clues presence accretion disk These constraints support low-mass but do not provide definitive answer whether unseen component BH1 is indeed hole. results predict scenario where, if M $\ge 4.7M_{\odot}$, present (given inclination constraints), it must be hidden optically thick undetected spectra.