An accretion model for anomalous X-ray pulsars

1. An accretion model for anomalous X-ray pulsars Pinaki Chatterjee, Lars Hernquist & Ramesh Narayan The Astrophysical Journal, 534, 373, 2000

2. A classical work on the accretion model for AXPs • A link between the typical radio pulsars and AXPs • A global description of pulsars’ fates

4. What is AXP (Anomalous X-ray Pulsar)

5. What is AXP (Anomalous X-ray Pulsar) • Relatively low luminosity • The rate of loss of the rotational energy • Soft spectra • No binary companions

6. Two models for AXPs • Magnetars; isolated, ultra-magnetized neutron stars • Accretion models; fall-back disk (in this paper)

7. Accretion from a debris disk

8. Magnetospheric radius; the point at which the magnetic pressure exceeds the gas pressure

9. Whether or not will the disk influence the neutron star • Magnetosphric radius • Light cylinder; • Corotation radius ;

10. Typical radio pulsar phase

11. Propeller phase

12. Quasi-equilibrium “tracking” phase Rc roughly matches Rm (never really attained because the accretion rate declines steadily). X-ray bright Time from propeller to tracking; ttrans

13. ADAF model for disk • Infall will eventually become an ADAF accretion flow. • The ADAF transition will occur at tADAF when the associated accretion luminosity falls to 0.01LE. • LE is the Eddington luminosity. • X-ray luminosity will decline.

17. Contents • Brief introduction to the timing feature of AXP • Introduction to pulsar glitches and the post-glitch recovery • Explanations for the age problem of PSR B1757-24 • The fate of PSR B1757-24 (a future candidate of Anomalous X-ray Pulsar). • Conclusions and discussion

18. Classical description of the pulsars

20. What is AXP (Anomalous X-ray Pulsar)

21. glitches

22. Theoretical models for pulsar glitches; star quake and vortex creep

23. Post-glitch recovery for Vela and Crab

24. Average ratio of permanent changes to slowdown rate For Vela 0.00092 For Crab 0.00009

26. propeller

27. Spin-down rate in the accretion model

28. Fate of pulsars in accretion model (P. Chatterjee et al. 2000)

29. Chandra detection is consistent with standard magnetospheric emission (Kaspi et al. 2001)

31. Estimation of the age of PSR B1757-24 or similar pulsars

32. Glitch pulsars and their associated SNRs

33. “young” pulsars and their missing SNRs

36. Glitches in AXP?

37. Conclusions and discussion • New model bases on observation; glitches • We should carefully estimate the pulsars’ ages • the fate of a pulsar depends on its post-glitch recovery type. • The population of AXPs given by our model is reasonable.