2007ApJ...658..514R

We report the detection of pulsations from two accreting transient high-mass X-ray binaries (HMXBs) at low X-ray luminosities (~1-4x10³⁴ ergs/s). While one (4U 1145-619) has been detected pulsing previously at a lower luminosity, the second (1A 1118-615) has not, making it the third such transient HMXB from which pulsations are detected at low luminosity. The pulsars exhibit broadband rms variability (22.3%±0.1% and 9.2%±0.1%, respectively). While the present observations do not permit measurement of a spin frequency derivative, spin-down is implied in comparison with previous Compton Gamma Ray Observatory/BATSE observations. If spin-down occurred at the presently observed X-ray luminosity of 4U 1145-619, the required mass accretion rate is insufficient to produce the observed X-ray luminosity from a shock at the magnetosphere, and only a fraction of the mass accretion makes its way to the neutron star surface, with most of the mass leaving the system, carrying away angular momentum to affect spin-down.