Abstract
Several years of timing the pulsar in the binary neutron star system M15C have yielded the masses of both stars: the total mass is
M
T
= 2.7121(6) M
⊙
; the companion mass is
m
c
= 1.36(4) M
⊙
; and the pulsar mass is
m
p
= 1.35(4) M
⊙
. We argue that this system is not likely to have formed through accretion-induced collapse (AIC), and that the standard model also has problems in explaining the formation.