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Timing Features of XTE J1807-294 in 2003 March outburst. --Possible Evidence for Accreting Blobs. Fan Zhang et al. (astro-ph/0602529). Content. 1. Introduction LMXBs : correlations of spectral state and timing variability MXPs : basic observational results
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Timing Features of XTE J1807-294 in 2003 March outburst --Possible Evidence for Accreting Blobs Fan Zhang et al. (astro-ph/0602529)
Content 1. Introduction • LMXBs : correlations of spectral state and timing variability • MXPs : basic observational results 2. Timing features of J1807-294 • Four flares distinguished in 2003 March RXTE observation • Correlations among count rate, basic fractional pulse amplitude and QPO frequencies 3. Discussion of our results • Constraints on QPO models • Possible origin of the relatively soft broad ‘puny’ flares
Introduction of LMXBs Van der Klis 2004, astro-ph/0410551
Common frequency correlation ? L_Hz ~150Hz ? L_h2 (harmonic) ? L_LFN
Open questions • Is hecto-hertz QPO specific for atoll ? • Is L_h harmonic specific for Z ? • Does LFN really vary in different Z ? • Are twin kHz QPOs correlated with NS spin ? ----- MXP,e.g. SAX J1808.4-3658 ----- burst oscillation-spin
Introduction of MXPs Accretion powerd millisecond X-ray pulsar • Ultra-compact group (Porb<40 min) XTE J1807-294 (2003) XTE J1751-305 (2002) XTE J0929-314 (2002) • Relatively wide group (Porb=2.~4.28 hour) SAX J1808.4-3658 (1998) XTE J1814-338 (2003) IGR J00291+5934 (2005) ---------type I thermal nuclear outburst ---------kHz QPOs
Lightcurve of MXPs -----Wijnands (astro-ph/0501264)
Why choose XTE J1807-294? • Twin kHz QPOs – inner disk evolution • Binary parameters – pulse profiles – NS surface emission • Compton dominated spectrum • No type I thermonuclear bursts so we can focus on studying the effect of disk evolutions on the NS surface emission
XTE J1807-294: 4 flares 1. Hours-to-days low-amplitude intensity fluctuation; 2. Stronger soft emission enhancement 3. Apparent basic pulse amplitude variability
Frequency correlation 1,Common frequency correlations between Lu,Ll,LhHz,Lh,Lb 2, Additional components of L_h2, L_LFN 3,shift factor of 1.5 for Lu, Ll, L_LFN
Correlations between net count rate,kHz QPOs and the fractional basic pulse profile Are parallel tracks related to the flares? Inner disk movement is correlated with NS surface emissions
Discussion: constraints on QPO models • Both L_Hz and L_h harmonic are observed in one source XTE J1807-294, so they are not specific components for atoll or Z sources. • L_b and L_LFN appear simultaneously in the spectrum of XTE J1807-294, so they are two components with different origins. L_LFN of GX17+2 is a different component from L_LFN observed in other Z sources, so its distribution can not be explained by the same QPO model for L_b of atoll or L_LFN of other Z sources. • Shift factor of about 1.5 exists also in XTE J1807-294. • The kHz QPO frequency separation varies around 191Hz. Abramowicz et al. 2003, A&A, 404, L21
Discussion: origin of the flares Inner disk radius variability (Accretion rate? Accretion pattern?) • groups 1-3, groups 4-6 QPO frequency variability NS emission variability • Variable relationship between a0/c0 and c0 Possible Origin: 1.Accreting inhomogeneous disk flow 2.Nuclear burning, e.g. ‘fires’ on the NS surface (Bildsten 1993) Poutanen, J. & Gierlinski, M. 2003, MNRAS, 343, 1301 Bildsten, L. 1993, Apj, 418, L21 Strohmyer, T. E. Astro-ph/0301544