[en] Though pulsars spin regularly, the differences between the observed and predicted ToA (time of arrival), known as “timing noise^, can still reach a few milliseconds or more. We try to understand the noise in this study. As proposed by Xu and Qiao in 2001, both dipole radiation and particle emission would result in pulsar braking. Accordingly, possible fluctuation of particle current flow is suggested here to contribute significant ToA variation of pulsars. We find that the particle emission fluctuation could lead to timing noise which cannot be eliminated in timing process and that a longer period fluctuation would arouse a stronger noise. The simulated timing noise profile and amplitude are in agreement with the observed timing behaviors on the timescale of years. (geophysics, astronomy, and astrophysics)

[en] With the constraint from gravitational wave emission of a binary merger system (GW170817) and two-solar-mass pulsar observations, we investigate the r-mode instability windows of strange stars with unpaired and color-flavor-locked phase strange quark matter. Shear viscosities due to surface rubbing and electron-electron scattering are taken into account in this work. The results show that the effects of the equation of state of unpaired strange quark matter are only dominant at low temperature, but do not have significant effects on strange stars in the color-flavor-locked phase. A color-flavor-locked phase strange star, which is surrounded by an insulating nuclear crust, seems to be consistent with observational data of young pulsars. We find that an additional enhanced dissipation mechanisms might exist in SAX J1808.4–3658. Fast spinning young pulsar PSR J0537–6910 is a primary source for detecting gravitational waves from a rotating strange star, and young pulsars might be strange stars with color-flavor-locked phase strange quark matter. (paper)

[en] The very small braking index of PSR J1734–3333, n = 0.9 ± 0.2, challenges the current theories of braking mechanisms in pulsars. We present a possible interpretation that this pulsar is surrounded by a fall-back disk and braked by it. A modified braking torque is proposed based on the competition between the magnetic energy density of the pulsar and the kinetic energy density of the fall-back disk. With this torque, a self-similar disk can fit all the observed parameters of PSR J1734–3333 with natural initial values of parameters. In this regime, the star will evolve to the region having anomalous X-ray pulsars and soft gamma repeaters in the P – P^· diagram in about 20 000 years and stay there for a very long time. The mass of the disk around PSR J1734–3333 in our model is about 10M_⊕, similar to the observed mass of the disk around AXP 4U 0142+61. (research papers)

[en] The Five-hundred-meter Aperture Spherical radio Telescope (FAST) has the potential to discover many new pulsars and new phenomena. In this paper we mainly concentrate on how FAST can impact study of the pulsar emission mechanism and magnetospheric dynamics. Several observational programs heading to this direction are reviewed. To make full use of the superior performance of FAST and maximize the scientific outcome, these programs can be arranged in different phases of FAST according to their demands for observational conditions. We suggest that programs can be performed following the test phase, which are observations of multifrequency mean pulse profiles, anomalous X-ray pulsars (AXPs)/soft gamma-ray repeaters (SGRs), mode changing, drifting subpulse and nulling. The long-term monitoring can be carried out for mode changing, AXPs/SGRs and precessional pulsars. Others programs, including polarization observations of radio and γ-ray pulsars, searching for weak pulse components, and multifrequency observations of subpulse drifting, microstructure and giant pulses, can be conducted in all the normal operating phases (the first and second phases). These programs will push forward the frontier in this field in different respects. The search for sub-millisecond pulsars and follow-up observations of their emission properties are very important projects for FAST, but they may be covered by other papers in this mini-volume; therefore, they are not discussed here. (paper)

[en] Highlights: • A novel blue-emitting phosphor Li₄SrCa(SiO₄)₂:Tm³⁺ was reported. • Li₄SrCa(SiO₄)₂:Tm³⁺ exhibited excellent thermal and irradiation stability. • Li₄SrCa(SiO₄)₂:Tm³⁺ was found to possess high color purity. - Abstract: In this work, we synthesized Tm³⁺ doped Li₄SrCa(SiO₄)₂ phosphors and investigated their photoluminescence properties under the excitation of ultraviolet and vacuum ultraviolet lights. The crystal structure analysis and variation of cell parameters confirm that Tm³⁺ ions have been successfully doped in the structure of Li₄SrCa(SiO₄)₂ host by occupying the sites of Ca²⁺ with the coordination number of 6. The luminescence results suggest that Li₄SrCa(SiO₄)₂:Tm³⁺ is a good blue-emitting phosphor when excited by ultraviolet and vacuum ultraviolet irradiations. In addition, it is observed that there is nearly no degradation for Li₄SrCa(SiO₄)₂:Tm³⁺ after undergoing thermal and irradiation treatments. Possible mechanisms for the luminescence processes are proposed on the basis of the discussion of excitation and emission spectra. In particular, the emission color of Li₄SrCa(SiO₄)₂:Tm³⁺ by excitation of 147 and 172 nm irradiations is very close to the standard blue color, suggesting that it could be potentially applied in plasma display panels and mercury-free fluorescence lamps