Accretion mode changes in Centaurus X-3

Abstract

We report here discovery of the existence of two different accretion modes in the high mass X-ray binary pulsar Cen X-3 during its high states. The multiband X-ray light curves of Cen X-3 lasting for more than 3400 days obtained with the All Sky Monitor (ASM) onboard the Rossi X-ray Timing Explorer (RXTE) shows many episodes of high and low X-ray intensities. The high intensity phases last between a few to upto 110 days and the separation between two high intensity phases also varies widely. One remarkable feature deduced from the RXTE-ASM light curves is that during these high intensity phases, Cen X-3 manifests in two very distinct spectral states. When the source makes a transition from the low intensity phase to the high intensity phase, it adopts one of these two spectral states and during the entire high intensity phase remains in that particular spectral state. During December 2000 to April 2004, all the high intensity episodes showed a hardness ratio which is significantly larger than the same during all the high states prior to and subsequent to this period. It is also found that most of the soft outbursts reach a nearly constant peak flux in the 5--12 keV band. For comparison, similar analysis was carried out on the long term X-ray light curves of three other X-ray binary pulsars Her X-1, Vela X-1, and SMC X-1. Results obtained with these sources are also presented here and we found that none of the other sources show such a behaviour. From these observations, we suggest that Cen X-3 has two different accretion modes and in the course of nine years it has exhibited two switch overs between these.

5 pages, 5 postscript figures, accepted for publication in Astronomy and Astrophysics Letters

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Cited by in corpus (11)

• Warping and precession in galactic and extragalactic accretion disks
• X-ray Spectroscopy of the High Mass X-ray Binary Pulsar Centaurus X-3 over its Binary Orbit
• Effect of pulse profile variations on measurement of eccentricity in orbits of Cen X-3 and SMC X-1
• Quasiperiodic oscillations in Cen X-3 and the long term intensity variations
• Quasi periodic oscillations in XTE J0111.2--7317, highest frequency among the HMXB pulsars
• Long term flux variations in Cen X-3: clues from flux dependent orbital modulation and pulsed fraction
• Fitting strategies of accretion column models and application to the broadband spectrum of Cen X-3
• Orbital- and spin-phase variability in the X-ray emission from the accreting pulsar Cen X-3
• Tidal Interaction in High Mass X-ray Binaries
• No apparent accretion mode changes detected in Cen X-3
• Variations in the X-ray eclipse transitions of Cen X-3