arXiv subjects

Shakhboz Khasanov

Publications and source records attributed to Shakhboz Khasanov.

2 recordsLinked to original sources

arXiv2026

Timing, Polarization, and Single-Pulse Properties of Long-Period FAST Pulsars

We present phase-connected timing and polarization measurements for two long-period FAST-CRAFTS pulsars, PSRs J0000+6252 and J2131+3642, and extend single-pulse emission-state analysis to a five-source sample including PSRs J1903+1407, J1502+4653, and J2112+4058. FAST L-band timing baselines span 414 to 511 days; the two pulsars have spin periods of 1.11 to 1.55 s, period derivatives of $(3.99$ to $4.06)\times10^{-15}~{\rm s~s^{-1}}$, characteristic ages of 4.34 to 6.16 Myr, surface magnetic fields of $(2.15$ to $2.52)\times10^{12}$ G, and spin-down luminosities of $(4.21\times10^{31}$ to $1.16\times10^{32})~{\rm erg~s^{-1}}$. Their rotation measures are $70.2\pm26.7$ and $-44.6\pm7.6~{\rm rad~m^{-2}}$, with linear polarization fractions of 17.6\% to 27.2\%. PSR J2131+3642 shows a short monotonic PA segment permitting a formal rotating-vector-model fit, though limited longitude coverage leaves the geometric parameters poorly constrained; PSR J0000+6252 has too few PA points for such a fit. Gaussian mixture modeling (GMM) of single-pulse energy distributions identifies null, weak, and burst components in PSRs J0000+6252, J1903+1407, J1502+4653, and J2112+4058, while J2131+3642 shows only weak and burst states. We also identify bright single pulses (peak intensity $\geq10\times$ the integrated average profile): 42 in J0000+6252, four each in J1903+1407 and J2112+4058, and none in J2131+3642 or J1502+4653. These bright pulses occur within the main emission window with no evidence of periodic recurrence, consistent with sporadic enhancements of the normal radio-emission beam. For J2112+4058, we measure a scattering timescale $τ_{\rm sc}=5.84\pm0.18$ ms at $ν_{\rm ref}=1.25$ GHz. Together, these results highlight the diversity of magnetospheric variability among slowly rotating neutron stars.

astro-ph.HE↗

arXiv2026

Ruppeiner thermodynamic geometry, microstructure, quasinormal modes and greybody factors of the Einstein-Skyrme black hole

We investigate the thermodynamic microstructure, quasinormal mode spectrum, and greybody factors of the exact, static, spherically symmetric black hole in Einstein-Skyrme theory, building on the recently established first law that promotes the Skyrme couplings K and λ to extensive variables. Using Ruppeiner geometry, we construct the scalar curvature from the Hessian of the mass. The curvature remains finite at the second-order (heat-capacity) phase transition but diverges in the extremal, zero-temperature limit. Throughout the physically admissible region the curvature retains a single sign, indicating microscopic interactions of one dominant (attractive) type whose strength grows towards extremality. We perform a Joule-Thomson-like isenthalpic expansion and prove analytically that the corresponding coefficient is strictly negative across the entire physical parameter space, implying the black hole always cools as λ increases at a fixed mass, with no inversion temperature. Turning to perturbations, we derive the effective potential for massless scalar fields. The solid-angle-deficit coupling K controls its shape-substantially lowering the barrier-while at fixed K the quartic coupling λ produces only minor changes. Rigorous lower bounds on greybody factors are obtained in closed form using Visser's method: increasing K raises the bound, since a larger horizon lowers the centrifugal barrier, whereas increasing λ mildly suppresses low-frequency transmission. Our results provide the first comprehensive study of the thermodynamic microstructure and perturbative spectroscopy of this rare analytic hairy black hole, complementing and extending the existing thermodynamic analysis into previously unexplored territory.

gr-qc↗