Flares, Broadening of the Pulse frequency peak, and Quasi Periodic Oscillations in the Transient X-ray Pulsar 4U 1901+03

Abstract

After a long quiescence of three decades, the transient X-ray pulsar 4U 1901+03 became highly active in 2003 February. From the analysis of a large number of Rossi X-ray Timing Explorer/ Proportional Counter Array (RXTE/PCA) observations of this source, we report here the detection of X-ray flares, a broadening of the pulse frequency peak and Quasi Periodic Oscillations (QPOs). The X-ray flares showed spectral changes, had a duration of 100 s - 300 s, and were more frequent and stronger during the peak of the outburst. In most of the observations during the outburst we also detected a broadening of the pulse frequency peak. We have also found intensity dependent changes in the pulse profile at very short timescales. This reveals a coupling between the periodic and the low frequency aperiodic variabilities. In addition, near the end of the outburst we have detected a strong QPO feature centered at ~ 0.135 Hz. The QPO feature is broad with a quality factor of 3.3 and with an rms value of 18.5+/-3.1%. Using the QPO frequency and the X-ray luminosity during the QPO detection period we estimated the magnetic field strength of the neutron star as 0.31*10^12 G which is consistent with the value inferred earlier under the assumption of spin equilibrium.

7 pages; 6 figures, Accepted in MNRAS

References in corpus (4)

• High variability in Vela X-1: giant flares and off states
• Quasiperiodic oscillations in Cen X-3 and the long term intensity variations
• A study of the long term evolution of quasi periodic oscillations in the accretion powered X-ray pulsar 4U 1626-67
• Bright flares from the X-ray pulsar SWIFT J1626.6-5156

Cited by in corpus (11)

• Low-level accretion in neutron-star X-ray binaries
• Timing and spectral studies of the transient X-ray pulsar GX 304-1 during an outburst
• Accretion regimes in the X-ray pulsar 4U 1901+03
• Detection of a variable QPO at ~41 mHz in the Be/X-ray transient pulsar 4U 0115+634
• Evolution of timing and spectral characteristics of 4U 1901+03 during its 2019 outburst using the Swift and NuSTAR observatories
• Switches between accretion structures during flares in 4U 1901+03
• AstroSat detection of a mHz QPO and cyclotron line in IGR J19294+1816 during the 2019 outburst
• High energy Millihertz quasi-periodic oscillations in 1A 0535+262 with Insight-HXMT challenge current models
• Timing and spectral studies of Cen X-3 in multiple luminosity states using $\text{AstroSat}$
• Sidebands to mHz QPOs in 4U 1626$-$67 in the second spin-down state
• Spectral evolution of X-ray pulsar 4U 1901+03 during the 2019 outburst based on Insight-HXMT and NuSTAR observations