arXiv subjects

Habtamu Menberu Tedila

Publications and source records attributed to Habtamu Menberu Tedila.

7 recordsLinked to original sources

arXiv2026

Component-dependent Periodic Emission Variations of PSR J1857+0943 Observed with FAST

Single-pulse studies of millisecond pulsars provide an important way to probe the plasma processes responsible for their radio emission, but such studies remain rare because of the weak emission and short rotation periods of these objects. Using the high sensitivity of the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we investigate the pulse-to-pulse variability of PSR J1857+0943 and report the first detection of distinct fluctuation behavior across its main pulse and interpulse. The integrated main pulse and interpulse each show multiple emission components with markedly different variability properties. Pulse longitude resolved fluctuation analysis reveals quasi-periodic intensity modulation in both pulse regions, with the interpulse showing a characteristic modulation timescale approximately twice that observed in the trailing part of the main pulse. A longitude-resolved cross-correlation analysis further reveals a weak anti-correlation between the trailing main-pulse emission and the interpulse at a lag of one rotation period, suggesting that these widely separated pulse-longitude ranges may be influenced by a common magnetospheric process. The polarization properties of the single pulses in the same longitude range also differ from those of the adjacent main-pulse components, supporting the presence of component-dependent emission behavior. In addition, we measure a one-hour jitter noise of $σ_{\rm J,1h}=73.2\pm1.5$ ns at 1.25 GHz, consistent with previous measurements. These results demonstrate that PSR J1857+0943 exhibits complex single-pulse variability and provide new observational constraints on the magnetospheric structure of interpulse millisecond pulsars.

astro-ph.HE↗

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

Indication for Decreasing Dispersion Measure in the Population of Repeating Fast Radio Bursts and Connection to Young Supernova Remnant Expansion

Fast Radio Bursts (FRBs) are millisecond-duration, highly energetic radio transients of uncertain origin. Repeating FRBs provide an excellent population for investigating their nature, particularly through studies of parameter evolution. Out of the 63 repeaters monitored by CHIME, we select the 19 sources with more than 10 detected bursts, and examine their long-term dispersion measure (DM) evolution. Seven sources show statistically significant DM evolution and are classified as the golden sample. Of these, five exhibit a decreasing DM trend and two show an increasing trend. We then perform a binomial test under the null hypothesis that decreasing and increasing DM variation trends have equal probabilities. The current combined sample, including our golden sample and additional repeaters with reported DM change rate from the literature, gives a p-value of 0.033, supporting that decreasing DM trends are more common in the repeating FRB population. This statistical result is consistent with scenarios in that the local electron density around repeaters generally decreases with time, for example, due to expansion of a young supernova remnant (SNR). Finally, within the SNR expansion model, we provide an illustrative estimate of the SNR contributions to the DM for different ejecta masses.

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↗

arXiv2025

Multi-Faceted Emission Properties of PSR J2129+4119 Observed with FAST

We present a detailed single-pulse study of the long-period pulsar PSR J2129+4119 using high-sensitivity FAST observations. Despite locating well below the traditional death line, the pulsar exhibits sustained and multi-modal emission behavior, including nulls, weak pulses, regular emission, and occasional bright pulses. The nulling fraction is measured to be $8.13\% \pm 0.51\%$, with null durations typically under four pulse periods. Fluctuation spectral analysis reveals both phase-modulated subpulse drifting and intermittent beat-like modulation. At the same time, polarization profiles show high linear polarization and stable polarization position angle (PPA) swings consistent with a near-tangential sightline geometry. Quasi-periodic microstructures are detected in 11.54\% of regular pulses, with a mean periodicity and width of 4.57 ms and 4.30 ms, respectively. A well-defined scintillation arc in the secondary spectrum confirms the presence of a localized scattering screen. These results indicate that PSR J2129+4119 remains magnetospherically active and coherently emitting despite its low energy loss rate, offering key insights into pulsar emission physics near the death line.

astro-ph.HE↗

arXiv2025

The magnetar model's energy crisis for a prolific repeating fast radio burst source

Fast radio bursts (FRBs) are widely considered to originate from magnetars that power the explosion through releasing magnetic energy. Active repeating FRBs have been seen to produce hundreds of bursts per hour and can stay active for months, thus may provide stringent constraints on the energy budget of FRBs' central engine. Within a time span of 214 days, we detected 11,553 bursts from the hyper-active FRB 20240114A that reached a peak burst rate of 729 hr$^{-1}$. This is the largest burst sample from any single FRB source, exceeding the cumulative total of all published bursts from all known FRBs to date. Assuming typical values of radio efficiency and beaming factor, the estimated total isotropic burst energy of this source exceeds 86% of the dipolar magnetic energy of a typical magnetar. The total released energy from this source exceeds that of other known repeaters by about one and a half orders of magnitude, yielding the most stringent lower limit of $4.7\times10^{32}$ G cm$^3$ for the magnetar's magnetic moment. The source remained active at the end of this observation campaign. Our findings thus require either the FRB's central magnetar engine's possessing exceptionally high emission efficiency or a more powerful compact object than a typical magnetar.

astro-ph.HE↗

arXiv2024

The Study of Mode Switching behavior of PSR J0614+2229 Using the Parkes Ultra-wideband Receiver Observations

In this paper, we presented a detailed single pulse and polarization study of PSR J0614+2229 based on the archived data observed on 2019 August 15 (MJD 58710) and September 12 (MJD 58738) using the Ultra-wideband Low-frequency Receiver on the Parkes radio telescope. The single-pulse sequences show that this pulsar switches between two emission states, in which the emission of state A occurs earlier than that of state B in pulse longitude. We found that the variation in relative brightness between the two states is related to time and both states follow a simple power law very well. Based on the phase-aligned multi-frequency profiles, we found that there is a significant difference in the distributions of spectral index across the emission regions of the two states. Furthermore, we obtained the emission height evolution for the two emission states and found that, at a fixed frequency, the emission height of state A is higher than that of state B. What is even more interesting is that the emission heights of both states A and B have not changed with frequency. Our results suggest that the mode switching of this pulsar is possibly caused by changes in the emission heights that alter the distributions of spectral index across the emission regions of states A and B resulting in the frequency-dependent behaviors, i.e., intensity and pulse width.

astro-ph.HE↗