Open AccessShort‐term pulse frequency fluctuations of OAO 1657−415 from RXTE observations
Author(s) -
Baykal Altan
Publication year - 2000
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2000.03249.x
Subject(s) - physics , astrophysics , pulsar , luminosity , accretion (finance) , pulse (music) , spin (aerodynamics) , accretion disc , orbital period , binary number , astronomy , stars , arithmetic , mathematics , galaxy , detector , optics , thermodynamics
We present new X‐ray observations of the high‐mass X‐ray binary (HMXRB) pulsar OAO 1657−415, obtained during one orbital period (10.44 d) with the Rossi X‐Ray Timing Explorer ( RXTE ). Using the binary orbital parameters, obtained from Burst and Transient Source Experiment (BATSE) observations, we resolve the fluctuations in the pulse frequency at time‐scales on the order of 1 d for the first time. Recent BATSE results by Baykal showed that OAO 1657−415 has spin‐up/down trends in its pulse frequency time series, without any correlation with the X‐ray luminosity at energies >20 keV. In the present RXTE observations the source is found to be in an extended phase of spin‐down. We also find a gradual increase in the X‐ray luminosity which is correlated with a marginal spin‐up episode. The marginal correlation between the gradual spin‐up (or decrease in spin‐down rate) and increase in X‐ray luminosity suggests that OAO 1657−415 is observed during a stable accretion episode where the prograde accretion disc is formed.