Constraining the Equation Of State (EOS) of neutron stars with eXTP/GDP Long Ji

Lattimer, J. M.& Prakash, M. 2001

Nicer’s result

Target: 1, burst oscillations 2, accreting millisecond pulsars 3, rotation-powered pulsars Light bending : R/M Doppler effect(rotate rapidly) : R Key point : the local radiative model

1. the mass M of the neutron star; 2. the equatorial radius Req of the neutron star; 3. its specific spin angular momentum a ≡ 2πIf c/GM2, where I is its moment of inertia; 4. the inclination i; 5. the observer colatitude of the spot θs; Dimitrios Psaltis 2014 (if ρ <=10°)

Ka Ho Lo et al. 2013

Low background: ignore Minimum detectable polarization (MDP), 99% confidence level

For type-I bursts Plane-parallel symmetry semi-infinite optical depth Chandra 1947

flame spreading Spitkovsky, A. et al. 2002

flame spreading Spitkovsky, A. et al. 2002

K. Viironen and J. Poutanen 2004

Results:

Summary: GDP do not have enough ability to detect the polarization level during bursts.

Accreting millisecond pulsars:

Marek Gierlinski et al Comp/total flux model A: keV : 77% keV : 93% model B: keV : 40% keV : 79%

Can we distinguish them if we have a larger effective area? Produce a faked spectrum by using model A, and then fit it with model B.

thaw kT_bb

trapped by a local minimum

Gridding the parameter space

n: scattering orders tau: optical density K. Viironen and J. Poutanen 2004

Summary: GDP is very helpful to decouple the radiative models

X-ray pulsars (slow spin) Distinguish different radiation mechanisms

Further improvement?

Thanks ！！

1. the mass M of the neutron star; 2. the equatorial radius Req of the neutron star; 3. the ellipticity of its surface s; 4. its specific spin angular momentum a ≡ 2πIf c/GM2, where I is its moment of inertia; 5 the quadrupole moment of its spacetime as measured by the parameter η; 6. the inclination i; 7. the observer colatitude of the spot θs; and 8. the angular radius of the spot ρ. Dimitrios Psaltis 2014

Observables ： 1 ， flux rms 2 ， the ratio of the fundamental to second harmonic 3 ， color rms 4 ， phase difference Dimitrios Psaltis 2014

R norm ( e e-09) 93% ( e e-09) 77% ( e e-10 79%) ( e e-10 40%)

Dimitrios Psaltis 2014

Alessandro Patruno 2009