Stability of the parameters of the Stellar black-hole mass distribution estimated using nonparametric methods

Individual probability-density distributions for the masses of compact objects in 20 X-ray binary systems have been constructed. The mass distributions were modeled using Monte-Carlo simulations. The closeness of the components in systems with massive optical stars was taken into account using K corrections. The parameters of the resulting black-hole mass distributions were obtained using nonparametric statistical methods. The presence of a statistically significant mass gap in the range 3–5M _⊙ is confirmed. The currently observed probability-density distributions of the compact-object masses are stable against small amounts of data contamination.