Timing Features of XTE J1807-294 in 2003 March outburst

Fan Zhang et al. (astro-ph/0602529)

--Possible Evidence for Accreting Blobs

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

Source state

Power density spectrum

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

Introduction of MXPsAccretion 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

Frequency correlation in MXPs

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

Power Spectra

Frequency correlation

1,Common frequency correlations betweenLu,Ll,LhHz,Lh,Lb

2, Additional componentsof L_h2, L_LFN

3,shift factor of 1.5 forLu, 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

1. 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.

2. 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.

3. Shift factor of about 1.5 exists also in XTE J1807-294.

4. 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

Poutanen, J. & Gierlinski, M. 2003, MNRAS, 343, 1301Bildsten, L. 1993, Apj, 418, L21

Strohmyer, T. E. Astro-ph/0301544

Possible Origin: 1.Accreting inhomogeneous disk flow 2.Nuclear burning, e.g. ‘fires’ on the NS surface

(Bildsten 1993)

Thanks !