Pulsar Braking Index: A Test of Emission Models?

Abstract

Pulsar braking torques due to magnetodipole radiation and to unipolar generator are considered, which results in braking index being less than 3 and could be employed to test the emission models. Improved equations to obtain pulsar braking index and magnetic field are presented if we deem that the rotation energy loss rate equals to the sum of the dipole radiation energy loss rate and that of relativistic particles powered by unipolar generator. The magnetic field calculated by conventional way could be good enough but only modified by a factor of ∼ 0.6 at most. Both inner and outer gaps may coexist in the magnetosphere of the Vela pulsar.

Absorption features caused by oscillations of electrons on the surface of a quark star

“…The frequencies, ω(ℓ), at which hydro-cyclotron oscillations occur for 1E 1207.4-5209 with effective temperature T ≃ 0.2 keV, assuming a magnetic field of B ≃ 7 × 10 11 G. G and thus ω(ℓ = 3) = 0.7 keV, we obtain the oscillation frequencies shown in Table III. A magnetic field of ∼ 7 × 10 11 G is compatible with the magnetic fields inferred for 1E 1207.4-5209 from timing solutions [18] (9.9 × 10 10 G or 2.4 × 10 11 G), since 1E 1207.4-5209 shows no magnetospheric activity and theṖ -value would be overestimated if one applies the spin-down power of magnetic-dipole radiation [25,26]. We note that the absorption feature at ω(ℓ = 1) = 4.2 keV shown in Table III may not be detectable since the stellar temperature is only ∼ 0.2 keV (see Table I), which will suppress any thermal feature in that energy range.…”

What can the braking indices tell us about the nature of pulsars?

“…Although a constant potential drop of 10 12 V is generally accepted, we would like to note that Φ might changes slightly with Ω (e.g. Φ ∼ Ω −1/7 in Xu & Qiao, 2001). The effects would change the braking index by a factor, e.g.…”

“…Φ ∼ Ω −1/7 in Xu & Qiao, 2001), or just a few×10 12 V (e.g. RS75; Usov & Melrose, 1995), so we could assume a constant potential drop Φ = 10 12 V in the polar gap region.…”

Can the Age Discrepancies of Neutron Stars Be Circumvented by an Accretion-assisted Torque?

“…A conventional and convenient way to obtain the age of rotation-powered neutron stars is by equalizing the energy-loss rate of spin-down to that of magnetodipole radiation, assuming that the inclination angle between magnetic and rotational axes is (e.g., Manchester & Taylor 1977). This conclusion a p 90Њ keeps quantitatively for any a, as long as the braking torques due to magnetodipole radiation and the unipolar generator are combined (Xu & Qiao 2001). The resultant age, the so-called characteristic age, is if the initial period is mucḣ T p P/(2P) P c 0…”