The Massive Runaway Stars HD 14633 and HD 15137

We present results from a radial velocity study of two runaway O-type stars, HD 14633 (ON8.5 V) and HD 15137 [O9.5 III(n)]. We find that HD 14633 is a single-lined spectroscopic binary with an orbital period of 15.4083 days. The second target, HD 15137, is a radial velocity variable and a possible single-lined spectroscopic binary with a period close to 1 month. Both binaries have large eccentricity, small semiamplitude, and a small mass function. We show the trajectories of the stars in the sky based on an integration of motion in the Galactic potential, and we suggest that both stars were ejected from the vicinity of the open cluster NGC 654 in the Perseus spiral arm. The binary orbital parameters and runaway velocities are consistent with the idea that both these stars were ejected by supernova explosions in binaries and that they host neutron star companions. We find that the time of flight since ejection is longer than the predicted evolutionary timescales for the stars. This discrepancy may indicate that the stars have a lower mass than normally associated with their spectral classifications, that they were rejuvenated by mass transfer prior to the supernova, or that their lives have been extended through rapid rotation.