Importance of Compton scattering on X-ray spectra of Millisecond Pulsars and Intermediate Polars V. Suleimanov (Tuebingen University, Kazan State University) In collaboration with J. Poutanen (Oulu University) M. Falanga (SEA - Saclay)

Millisecond Pulsars LMXB, ν spin (NS) ~ 200 – 700 Hz, P orb ~ 40 min – 4.5 hours, B ~ 10 8 – 10 9 Gs Intermediate Polars (IPs) CV, P spin (WD) < P orb, B ~ 1 – 10 MGs AD disrupted by magnetic field at some radius R A (Alfven radius) R A is radius where P ram = P mag

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Method of WD mass estimations Shock wave standing above WD surface The kinetic energy of the infalling gas is converted to the thermal energy There is a reliable mass-radius relation for WD (Nauenberg 1972) Maximum temperature after the shock depends on WD mass only The temperature can be obtained from the fitting of the observed X- ray spectrum by bremsstrahlung model

Spectrum of IP TV Col obtained with the RXTE observatory. Crosses denote the PCA data, open circles – HEXTE data. Solid line show best fit model (see below).

Previous investigations Rotschild et al (1981) - idea Ishida (1991) – GINGA / LAC observations, isothermal post-shock region (PSR, or accretion column) Detail model of PSR (non-isothermal) Aizu (1973), Wu et al (1994), Woelk & Beuermann (1996), Cropper et al. (1999) WD mass determinations using non-isothermal models of PSR Cropper et al (1999) – GINGA / LAC (2-20 keV) Ramsay (2000) – RXTE / PCA (3-20 keV) First works

The model based on Cropper et al (1999) Mass continuity equation The momentum equation The energy equation Ideal-gas law The cooling rate The cooling function from Sutherland & Dopita (1993)

Is Compton scattering significant?

Method: radiation transfer solving by short characteristic method with Compton scattering taking into consideration (redistribution functions method (Poutanen & Svensson 1996))

Results (plane parallel approximation ):

More detail:

Conclusions Work is not finished It is necessary to improve the “accretion column” model for Millisecond Pulsars Compton scattering is significant for high mass Intermediate Polars and it is necessary to take into account