Tolman–Oppenheimer–Volkoff limit
Name Mass ( M ☉ ) Distance ( ly ) Companion class Mass determination method Notes
GW170817 s remnant 2.74 +0.04 −0.01 144,000,000 N/A Gravitational wave data of neutron star merger from LIGO and Virgo interferometers In NGC 4993 . Delayed collapse into a black hole 0.98 +0.31 −0.26 seconds after merger
2MASS J05215658+4359220 3.3 +2.8 −0.7 10,000 K-type ( ? ) giant Spectroscopic radial velocity measurements of noninteracting companion In Milky Way outskirts
LS 5039 3.7 +1.3 −1.0 8,200±300 O ( f ) N6.5V Intermediate-dispersion spectroscopy and atmosphere model fitting of companion Microquasar system
GRO J0422+32 / V518 Per 3.97 ± 0.95 8,500 M4.5V Photometric light curve modelling SXT system
LS I +61 303 ≤4.0 ~7,000 B0Ve Spectroscopic radial velocity measurements of companion Microquasar system
GRO J1719-24 / GRS 1716−249 ≥4.9 8,500 K0-5 V Near-infrared photometry of companion and Eddington flux LMXB system
4U 1543-47 5.0 +2.5 −2.3 ~30,000±3,500 A2 ( V ? ) Spectroscopic radial velocity measurements of companion SXT system
List of least massive black holes
See also : Stellar black hole Below is a list of black holes which approach the TOV limit from above .
The Tolman-Oppenheimer-Volkoff limit (or TOV limit) is an upper bound to the mass of cold, nonrotating neutron stars, analogous to the Chandrasekhar limit for white dwarf stars. Observations of GW170817, the first gravitational wave event due to merging neutron stars (which are thought to have collapsed into a black hole within a few seconds after merging), suggest that the limit is close to 2.17 solar masses. A neutron star in a binary pair (PSR J2215+5135) has been measured to have a mass close to or slightly above this limit, . A more secure measurement of PSR J0740+6620, a pulsar being eclipsed by a white dwarf, yields a mass of . Earlier theoretical work placed the limit at approximately 1.5 to 3.0 solar masses, corresponding to an original stellar mass of 15 to 20 solar masses. In the case of a rigidly spinning neutron star, the mass limit is thought to increase by up to 18-20%.