Pulsar Spindown by a Fall-Back Disk and the P-P_dot Diagram

Neutron stars may be surrounded by fall-back disks formed from supernova core-collapse. If the disk circumscribes the light-cylinder, the neutron star will be an active radio pulsar spinning down under the propeller spin-down torque applied by the disk as well as the usual magnetic dipole radiation torque. Evolution across the P-P_dot diagram is very rapid when pulsar spin-down is dominated by the propeller torque. This explains the distribution of pulsars in the P-P_dot diagram.Comment: 10 pages, 5 figures, aastex, final version accepted for publication in ApJ

Do Young Neutron Stars Which Show Themselves As AXPs, SGRs and Radio Pulsars Accrete?

We examined the fall-back disk models, and in general accretion, proposed to explain the properties of anomalous X-ray pulsars (AXPs), soft gamma repeaters (SGRs), and radio pulsars (PSRs). We checked the possibility of some gas remaining around the neutron star after the supernova explosion. We also compared AXPs and SGRs with the X-ray pulsars in X-ray binaries. We conclude the existing models of accretion from a fall-back disk are insufficient to explain the nature of AXPs/SGRs, particularly the SGR bursts. We also discussed the proposed model of combination of magnetic dipole radiation and propeller torques in order to explain the evolution of radio pulsars on the P-\.{P} diagram. The predictions of this model contradict the observational data.Comment: 16 Pages, 1 Figur

On Period and Burst Histories of AXPs and SGRs and the Possible Evolution of these Objects on the P-Pdot Diagram

In this paper, timing data for all of the anomalous X-ray pulsars and soft gamma repeaters are compiled. Timing properties of these objects are investigated. The effect of bursts of soft gamma repeaters on their period history is investigated. The P-Pdot diagram for pulsars, X-ray binaries, anomalous X-ray pulsars, soft gamma repeaters and dim radio quiet netron stars is constructed. The possible evolutionary tracks for anomalous X-ray pulsars, soft gamma repeaters and dim radio quiet netron stars are examined.Comment: 66 pages, 9 figures, submitted to Turkish Journal of Physic

Magnetospheric particle acceleration and X-ray emission of pulsars

The available data on isolated X-ray pulsars, their wind nebulae, and the supernova remnants which are connected to some of these sources are analyzed. It is shown that electric fields of neutron stars tear off charged particles from the surface of neutron star and trigger the acceleration of particles. The charged particles are accelerated mainly in the field of magneto-dipole radiation wave. Power and energy spectra of the charged particles depend on the strength of the magneto-dipole radiation. Therefore, the X-ray radiation is strongly dependent on the rate of rotational energy loss and weakly dependent on the electric field intensity. Coulomb interaction between the charged particles is the main factor for the energy loss and the X-ray spectra of the charged particles.Comment: minor correction on table format, 20 pages (4 figures, 1 table), submitted to International Journal of Modern Physics

Discovery of an OB Runaway Star Inside SNR S147

We present first results of a long term study: Searching for OB--type runaway stars inside supernova remnants (SNRs). We identified spectral types and measured radial velocities (RV) by optical spectroscopic observations and we found an early type runaway star inside SNR S147. HD 37424 is a B0.5V type star with a peculiar velocity of 74$\pm$8 km s$^{-1}$. Tracing back the past trajectories via Monte Carlo simulations, we found that HD 37424 was located at the same position as the central compact object, PSR J0538+2817, $30\!\pm\!4$ kyr ago. This position is only $\sim$4 arcmin away from the geometrical center of the SNR. So, we suggest that HD 37424 was the pre--supernova binary companion to the progenitor of the pulsar and the SNR. We found a distance of 1333$^{+103}_{-112}$ pc to the SNR. The zero age main sequence progenitor mass should be greater than 13 $M_\odot$. The age is $30\pm4$ kyr and the total visual absorption towards the center is 1.28$\pm$0.06 mag. For different progenitor masses, we calculated the pre--supernova binary parameters. The Roche Lobe radii suggest that it was an interacting binary in the late stages of the progenitor.Comment: Accepted to be published in MNRAS, 10 pages, 5 figure

Possible evolution of dim radio quiet neutron star 1E 1207.4-5209 based on a B-decay model

Dim radio-quiet neutron star (DRQNS) 1E 1207.4-5209 is one of the most heavily examined isolated neutron stars. Wide absorption lines were observed in its spectrum obtained by both XMM-Newton and Chandra X-ray satellites. These absorption lines can be interpreted as a principal frequency centered at 0.7 keV and its harmonics at 1.4, 2.1 and possibly 2.8 keV. The principal line can be formed by resonant proton cyclotron scattering leading to a magnetic field which is two orders of magnitude larger than the perpendicular component of the surface dipole magnetic field (B) found from the rotation period (P) and the time rate of change in the rotation period (\.{P}) of 1E 1207.4-5209. Besides, age of the supernova remnant (SNR) G296.5+10.0 which is physically connected to 1E 1207.4-5209 is two orders of magnitude smaller than the characteristic age ($\tau$=P/2\.{P}) of the neutron star. These huge differences between the magnetic field values and the ages can be explained based on a B-decay model. If the decay is assumed to be exponential, the characteristic decay time turns out to be several thousand years which is three orders of magnitude smaller than the characteristic decay time of radio pulsars represented in an earlier work. The lack of detection of radio emission from DRQNSs and the lack of point sources and pulsar wind nebulae in most of the observed SNRs can also be partly explained by such a very rapid exponential decay. The large difference between the characteristic decay times of DRQNSs and radio pulsars must be related to the differences in the magnetic fields, equation of states and masses of these isolated neutron stars.Comment: 13 pages, 1 figur