Timing and spectral study of XB 1254-690 using new RXTE PCA data
arXiv:1107.3993 · doi:10.1111/j.1365-2966.2010.17872.x
Abstract
We have analyzed the new Rossi X-ray Timing Explorer Proportional Counter Array data of the atoll neutron star (NS) low-mass X-ray binary (LMXB) system XB 1254-690. The colour-colour diagram shows that the source was in the high-intensity banana state. We have found two low-frequency candidate peaks with single trial significances of ~ 2.65 X 10^{-8} and ~ 7.39 X 10^{-8} in the power spectra. After taking into account the number of trials, the joint probability of appearance of these two peaks in the data set only by chance is ~ 4.5 X 10^{-4}, and hence a low-frequency QPO can be considered to be detected with a significance of ~ 4.5 X 10^{-4}, or, ~ 3.5σfor the first time from this source. We have also done the first systematic X-ray spectral study of XB 1254-690, and found that, while one-component models are inadequate, three-component models are not required by the data. We have concluded that a combined broken-powerlaw and Comptonization model best describes the source continuum spectrum among 19 two-component models. The plasma temperature (~ 3 keV) and the optical depth (~ 7) of the Comptonization component are consistent with the previously reported values for other sources. However, the use of a broken-powerlaw component to describe NS LMXB spectra has recently been started, and we have used this component for XB 1254-690 for the first time. We have attempted to determine the relative energy budgets of the accretion disc and the boundary layer using the best-fit spectral model, and concluded that a reliable estimation of these budgets requires correlations among time variations of spectral properties in different wavelengths.
16 pages, 6 figures, 4 tables; published in MNRAS
References in corpus (17)
- Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
- Nuclear-Powered Millisecond Pulsars and the Maximum Spin Frequency of Neutron Stars
- Evaluating Spectral Models and the X-ray States of Neutron-Star X-ray Transients
- Boundary layer, accretion disk and X-ray variability in luminous LMXBs
- Spectral changes during dipping in low-mass X-ray binaries due to highly-ionized absorbers
- The broad band X-ray/hard X-ray spectra of accreting neutron stars
- Spectral Fits to the 1999 Aql X-1 Outburst Data
- Measurement of neutron star parameters: a review of methods for low-mass X-ray binaries
- Results of a LMXB survey: variation in the height of the neutron star blackbody emission region
- Evolution of Spectral States of Aql X-1 during the 2000 Outburst
- Temperature Profiles of Accretion Disks around Rapidly Rotating Neutron Stars in General Relativity and Implications for Cygnus X-2
- Correlated timing and spectral behavior of 4U 1705-44
- A Hard Tail in the Broad Band Spectrum of the Dipper XB 1254-690
- Timing properties of XB 1254-690
- Chandra Observation of the Dipping Source XB 1254-690
- Quasi-periodic oscillations and noise in neutron star and black-hole X-ray binaries
- A study of accretion discs around rapidly rotating neutron stars in general relativity and its applications to four Low Mass X-ray Binaries