Distribution of observed compact object masses. The vertical dashed line represents the maximum mass allowed for NS (Fryer & Kalogera 2001). Open circles below that limit represent the masses of the NS compiled by Lattimer & Prakash (2005), extended with updated data from Özel et al. (2012) and Antoniadis et al. (2013). The solid circles indicate reliable BH masses (adopting the values favoured by Casares & Jonker 2014), while arrows indicate lower limits based on mass functions and upper limits to the inclination.