Orbital Decay and Evidence of Disk Formation in the X-Ray Binary Pulsar OAO 1657-415
Abstract
OAO 1657-415 is an eclipsing X-ray binary wind-fed pulsar that has exhibited smooth spin-up/spin-down episodes and has undergone several torque reversals throughout its long history of observation. We present a frequency history spanning nearly 19 years of observations from the Burst and Transient Source Experiment and from the Gamma-Ray Burst Monitor (Fermi/GBM). Our analysis suggests two modes of accretion: one resulting in steady spin-up correlated with flux during which we believe a stable accretion disk is present and one in which the neutron star is spinning down at a lesser rate which is uncorrelated with flux. Orbital elements of the pulsar system are determined at several intervals throughout this history. With these ephemerides, statistically significant orbital decay with a \dot{P}_{orb} =(-9.74+/- 0.78)\times 10^{-8} is established.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2012
- DOI:
- 10.1088/0004-637X/759/2/124
- arXiv:
- arXiv:1112.5190
- Bibcode:
- 2012ApJ...759..124J
- Keywords:
-
- accretion;
- accretion disks;
- pulsars: individual: OAO 1657–415;
- stars: neutron;
- stars: winds;
- outflows;
- X-rays: binaries;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- doi:10.1088/0004-637X/759/2/124