1. eXTP Workshop Timing Ultraluminous X-ray Sources with eXTP
Hua Feng
Tsinghua University

2. ULXs Non-nuclear accreting compact objects
Luminosity higher than the Eddington limit of stellar mass BHs
IMBHs M⊙
Pop III; star clusters;
Sub-Eddington
Stellar mass BHs
~10 M⊙ or massive
Similar to GBHBs or remnants of low-Z stars;
Near or super-Eddington
Could also be a pulsar (M82 X-2), but not a general case

3. X-ray timing – model independent mass estimate
Low frequency QPOs: spectral-timing correlation
Compare QPO frequency at the same spectral state
and spectral parameters
GRS
15 M⊙
XTE J
10 M⊙
LFQPO itself is not a good indicator of the BH mass, because it varies in a wide frequency range. But the QPO frequency is correlated with some spectral properties. An empirical method is to using such correlations and compare the QPO frequency at the same spectral state and same spectral parameters.
(Titarchuk & Fiorito 2004)

4. Shaposhnikov &Titarchuk 2009

5. HFQPOs

6. Timing ULXs M82 X-1 NGC 5408 X-1 NGC 6946 X-1 M82 X-2 (X42.3+59)
XMM-Newton
XTE
NGC 5408 X-1
NGC 6946 X-1
M82 X-2 (X )
Chandra
Strohmayer et al.; Feng et al; Rao et al.; Pasham et al.

7. M82 X-1 with eXTP
2-10 keV, 5000 cm2, 50 ks

8. Sources with QPO detectable
2XMM ULXs catalog，
Given 5σ significance, we expect to detect M82 X-1 like LFQPOs in 32 ULXs

9. Other targets
ULXs
BHBs in M31
BHBs in LMC
XRBs in Quiescence

10. HFQPOs for M82 X-1 Based on LFQPOs in XTE J1550-564
20 = 184 Hz
Q = /FWHM = 2.2 – 8.3
Assuming MBH = 500 M⊙, 20 = 3.72 Hz, FWHM = 0.5 (Q = 7.4)
84 ks exposure, rms = 7%,  = 6.5
Work done in 2012
6 year average result with XTE
(Pasham et al. 2014)