An accretion model for anomalous X-ray pulsars. Pinaki Chatterjee, Lars Hernquist & Ramesh Narayan The Astrophysical Journal, 534, 373, 2000. A classical work on the accretion model for AXPs A link between the typical radio pulsars and AXPs A global description of pulsars’ fates.
An accretion model for anomalous X-ray pulsars Pinaki Chatterjee, Lars Hernquist & Ramesh Narayan The Astrophysical Journal, 534, 373, 2000
A classical work on the accretion model for AXPs • A link between the typical radio pulsars and AXPs • A global description of pulsars’ fates
What is AXP (Anomalous X-ray Pulsar) • Relatively low luminosity • The rate of loss of the rotational energy • Soft spectra • No binary companions
Two models for AXPs • Magnetars; isolated, ultra-magnetized neutron stars • Accretion models; fall-back disk (in this paper)
Magnetospheric radius; the point at which the magnetic pressure exceeds the gas pressure
Whether or not will the disk influence the neutron star • Magnetosphric radius • Light cylinder; • Corotation radius ;
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
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.
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
Average ratio of permanent changes to slowdown rate For Vela 0.00092 For Crab 0.00009
Chandra detection is consistent with standard magnetospheric emission (Kaspi et al. 2001)
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.