arXiv subjects

Biping Gong

Publications and source records attributed to Biping Gong.

14 recordsLinked to original sources

arXiv2026

Single-Pulse Study of the Pseudo-nulling Pulsar PSR J1820-0509 Based on FAST Observations

Using two observations obtained with the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we present a detailed single-pulse analysis of the high-nulling pulsar PSR J1820-0509. We measure an exceptionally high nulling fraction of approximately 81.78%, significantly exceeding previous estimates from Parkes observations. The single-pulse energy distribution exhibits a clear bimodal structure, consistent with classical nulling behavior. However, stacking the identified null pulses reveals a statistically significant residual profile above the noise level, indicating that the nulls correspond to a very weak emission state rather than a complete cessation of radio emission. The pulsar shows clustered burst activities spanning several hundred rotation periods, with prominent quasi-periodicities at 1191 +/- 81 and 590 +/- 15 pulse periods in the two observations. Based on temporal clustering and integrated profile morphology, we identify three distinct emission modes (A, B, and C) and a pseudo-null state (D). These modes exhibit systematic differences in pulse morphology, polarization, and energy statistics. The pulse width-energy relations reveal clear transitions between low- and high-energy regimes. The energy distributions of Modes A and C are well described by lognormal functions, while Mode B follows a composite Gaussian-lognormal distribution. These results suggest that the radio emission of PSR J1820-0509 is governed by multiple quasi-stable magnetospheric states. The presence of weak emission during pseudo-nulls, together with systematic mode-dependent variations, supports the interpretation that pulsar nulling reflects transitions between different magnetospheric activity levels rather than a complete shutdown of emission.

astro-ph.HE↗

arXiv2025

Single-Pulse Morphology of PSR J1935+1616 (B1933+16) Based on archival data from FAST

We utilized archived data from the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) to analyze the single-pulse profile morphology of PSR J1935$+$1616 (B1933$+$16). The results show that PSR J1935$+$1616 exhibits significant micropulses as well as various changes in single-pulse profile morphology. In the FAST archived data, a total of 969 single pulses with microstructure were identified, accounting for 9.69$\%$ of the total pulse sample, with characteristic widths of $127.63^{+70.74}_{-46.25}$ $μ$s. About half of these pulses display quasiperiodic micropulses, with a periodicity of 231.77 $\pm$ 9.90 $μ$s. Among the 520 single pulses with quasiperiodic microstructure, 208 also exhibit quasiperiodicity in circular polarization, with a characteristic period of $244.70^{+45.66}_{-21.05}$ $μ$s. The micropulse characteristic width in circular polarization is 106.52 $\pm$ 46.14 $μ$s. Compared to normal pulses, the relative energy (E/ ) of single pulse with microstructure follows a double Gaussian distribution, while that of normal pulses follows a single Gaussian distribution. Based on the intensity of the leading and trailing components in the single-pulse profile morphology of PSR J1935+1616, we classified the pulses into four morphological modes (A, B, C, and D). The relative energy distribution of pulses in mode A is significantly different from the others, following a double Gaussian distribution, while the relative energy distributions in modes B, C, and D follow a single Gaussian distribution. Our study also suggests a possible correlation between micropulses and single-pulse profile morphology. Single pulse with micropulses are most likely to occur in mode A, while their occurrence is least likely in mode D.

astro-ph.HE↗

arXiv2023

The innermost jet in the hidden ultra-luminous X-ray source Cygnus X-3

Cygnus X-3 is a high-mass X-ray binary with a compact object accreting matter from a Wolf-Rayet donor star. Recently, it has been revealed by the Imaging X-ray Polarimetry Explorer (IXPE) as a hidden Galactic ultra-luminous X-ray (ULX) source with a luminosity above the Eddington limit along the direction of a narrow (opening angle <~32 degree) funnel. In between the IXPE observations, we observed Cyg X-3 with the European VLBI (very long baseline interferometry) Network at 22 GHz and the NICER X-ray instrument. To probe possible relations between the X-ray funnel and the potential radio jet from the ULX, we analyzed the simultaneous multi-wavelength data. Our high-resolution VLBI image reveals an elongated structure with a position angle of -3.2+/-0.4 degree, accurately perpendicular to the direction of the linear X-ray polarization. Because Cyg X-3 was in the radio quiescent state on 2022 November 10, we identify the mas-scale structure as the innermost radio jet. The finding indicates that the radio jet propagates along and within the funnel. Moreover, the jet is marginally resolved in the transverse direction. This possibly results from the strong stellar winds and the rapid orbital motion of the binary system.

astro-ph.HE↗

arXiv2022

Gravitational waves from bubble collisions in FLRW spacetime

Stochastic gravitational wave background (SGWB) is a promising tool to probe the very early universe where the standard model of particle physics and cosmology are connected closely. As a possible component of SGWB, gravitational waves (GW) from bubble collisions during the first order cosmological phase transitions deserve comprehensive analyses. In 2017, Ryusuke Jinno and Masahiro Takimoto proposed an elegant analysis approach to derive the analytical expressions of energy spectra of GW from bubble collisions in Minkowski spacetime avoiding large-scale numerical simulations for the first time[26]. However, they neglect the expansion of the universe and regard the duration of phase transitions as infinity in their derivation which could deviate their estimations from true values. For these two reasons, we give a new expression of GW spectra by adopting their method, switching spacetime background to FLRW spacetime, and considering a finite duration of phase transitions. By denoting $σ$ as the fraction of the speed of phase transitions to the expansion speed of the universe, we find when $σ$ is around $\mathcal{O}(10)$, the maxima of estimated GW energy spectra drop by around 1 order of magnitude than the results given by their previous work. Even when $σ=100$, the maximum of GW energy spectrum is only $65\%$ of their previous estimation. Such a significant decrease may bring about new challenges for the detectability of GW from bubble collisions. Luckily, by comparing new spectra with PLI (\textit{power-law integrated}) sensitivity curves of GW detectors, we find that the detection prospect for GW from bubble collisions is still promising for DECIGO, BBO, LISA, and TianQin in the foreseeable future.

gr-qc↗

arXiv2020

A Three-Dimensional Laser Interferometer Gravitational-Wave Detector

The gravitational wave (GW) has opened a new window to the universe beyond the electromagnetic spectrum. Since 2015, dozens of GW events have been caught by the ground-based GW detectors through laser interferometry. However, all the ground-based detectors are L-shaped Michelson interferometers, with very limited directional response to GW. Here we propose a three-dimensional (3-D) laser interferometer detector in the shape of a regular triangular pyramid, which has more spherically symmetric antenna pattern. Moreover, the new configuration corresponds to much stronger constraints on parameters of GW sources, and is capable of constructing null-streams to get rid of the signal-like noise events. A 3-D detector of kilometer scale of such kind would shed new light on the joint search of GW and electromagnetic emission.

gr-qc↗

arXiv2018

A Model of Solar Dynamo with Alternative Conversion of Large-Scale Magnetic Field and Production of Sunspots

Since the discovery of solar cycle related with magnetic field in 1908, deep seated oscillatory dynamo has been studied extensively. However, there are still open questions on the solar dynamo, e.g., asymmetric conversion between large-scale poloidal and toroidal field as well as physics underlying the butterfly pattern of sunspots. Here we report a new generation of large-scale magnetic field and process of energy release. The inductive action of fluid motions pervading the solar interior is represented by a RLC circuit in which the toroidal field built up through twisting of poloidal field, so called $ω$-effect, plays the role of a capacitor. Such a RLC circuit not only provides a self-sustained oscillatory system avoiding Cowling's antidynamo theorem, but also site of rapid magnetic reconnection which reproduces quadrupole magnetic field interpreting the behavior of sunspots and moving of foot-point in solar activities. Moreover, parameters of the circuit and the Sun are well consistent with the 22-year solar cycle.

astro-ph.SR↗

arXiv2017

Test of Weak Equivalence Principle with the multi-band timing of the Crab Pulsar

Weak Equivalent Principle (WEP) can be tested through the parameterized post-Newtonian parameter $γ$, representing the space curvature produced by unit rest mass. The parameter $γ$ in turn has been constrained by comparing the arrival times of photons originating in distant transient events, such as gamma-ray bursts, fast radio bursts as well as giant pulses of pulsars. Those measurements normally correspond to an individual burst event with very limited energy bands and signal-to-noise ratio (S/N). In this letter, the discrepancy in the pulse arrival times of the Crab Pulsar between different energy bands is obtained by the phase difference between corresponding pulse profiles. This allows us to compare the pulse arrival times at the largest energy band differences, between radio and optical, radio and X-ray, radio and gamma-ray respectively. As the pulse profiles are generated by phase-folding thousands of individual pulses, the time discrepancies between two energy bands are actually measured from thousands of events at each energy band, which corresponds to much higher S/N. The upper limit of the $γ$ discrepancy set by such an extensively-observed and well-modeled source is as follows: $γ_{radio}-γ_{γ-ray}<3.28\times10^{-9}$ at the energy difference of $E_{γ-ray}/E_{radio}\sim10^{13}$, $γ_{radio}-γ_{X-ray}<4.01\times10^{-9}$ at the energy difference of $E_{X-ray}/E_{radio}\sim10^{9}$, $γ_{radio}-γ_{optical}<2.63\times10^{-9}$ at $E_{optical}/E_{radio}\sim10^{5}$, and $γ_{optical}-γ_{γ-ray}<3.03\times10^{-10}$ at $E_{γ-ray}/E_{optical}\sim10^8$. This actually measures the arrival times of freely-falling photons in the gravitational field of the Milky Way with the largest amount of events and with data of the highest S/N, which tests WEP at the energy band differences that has never been reached before.

gr-qc↗

arXiv2014

Evidence of residual Doppler shift on three pulsars, PSR B1259-63, 4U1627-67 and PSR J2051-0827

The huge derivative of orbital period observed in binary pulsar PSR B1259-63, the torque reversal displaying on low mass X-ray binary, 4U1627-67 and the long term change of orbital period of PSR J2051-0827, seem totally unrelated phenomena occurring at totally different pulsar systems. In this paper, they are simply interpreted by the same mechanism, residual Doppler shift. In a binary system with periodic signals sending to an observer, the drift of the signal frequency actually changes with the varying orbital velocity, projected to line of sight at different phases of orbit. And it has been taken for granted that the net red-shift and blue-shift of an full orbit circle be cancelled out, so that the effect of Doppler shift to the signal in binary motion cannot be accumulated over the orbital period. However, taking the propagation time at each velocity state into account, the symmetry of the velocity distribution over the orbital phase is broken. Consequently, the net Doppler shift left in an orbit is non-zero. Understanding this Newtonian second Doppler effect not only makes pulsars better laboratory in the test of gravitational effects, but also allows us to extract the angular momentum of the pulsar of PSR J2051-0827, $\leq 2\times 10^{43}gcm^2$; and the accretion disc of 4U 1627-67, $7\times 10^{50} gcm^2/s$, respectively, which are of importance in the study of structure of neutron stars and the physics of accretion disc of X-ray binaries.

astro-ph.HE↗

arXiv2011

The non-ballistic superluminal motion in the plane of the sky-II

The model of non-ballistic jet motion proposed in 2008 provides a simple explanation to the inward jet motion and bent jet. Recently, evidences of such a non-radial motion increase rapidly, and more complicated morphologies appear. On the other hand, the ballistic plus precession model likely holds in majority samples of jet motion. This paper discusses the relationship between the ballistic and non-ballistic model of jet motion, which suggests that the interaction of ejectors with ambient matter can produce knots at different stages of evolution and hence different separations to the core. And as a jet precesses, knots produced between the core and the deceleration radius result in spiral pattern expected by the model of ballistic plus precession; and knots generated at the deceleration radius display non-radial motion such as bent jet or oscillation of ridge-line. This paper develops the first non-ballistic model in four aspects. Firstly, it provides a numerical simulation to the production of multi-knot for a precessing jet. Secondly, it fits the precession behavior of multi-knot and interprets the oscillation of ridge lines like S5 1803+784. Thirdly, it gives an unified interpretation to the bent jet applicable to both multi-knot and single knot. And fourthly, the problem of very large numbers of observed outward motions as opposed to the inward ones is addressed in a new scope.

astro-ph.HE↗

arXiv2008

The non-ballistic superluminal motion in the plane of the sky

Faster-than-light or superluminal motion was originally predicted as a relativistic illusion of ballistic moving ejecta, and confirmed in a few tens of sources observationally. However, the recent results of the long-term multi-epoch observations of quasars, active galaxies, tracing the structure further along the jets and following the motion of individual features for longer time, rise questions that are difficult to understand by the standard ballistic model. I.e., the ejecta are aligned with the local jet direction, instead of the core; and within individual jets apparently inward-moving features are observed. Here we show that these unexpected phenomena, although only a small fraction among large samples, indicate the existence of non-ballistic jet motion, in which a continuous jet produces a discrete hot spot. And the precession of such a hot spot in the plane of the sky appears superluminal. Therefore, an unified and simple interpretation to the new results is obtained, which can be further tested through its predictions on the evolution of ejecta. The study is of importance in the understanding of the nature of superluminal motion, the interaction of jets and surrounding materials, as well as the common physics underlying quasars and microquasars.

astro-ph↗

arXiv2006

An unified model for superluminal motion and state transition on microquasars and quasars

Superluminal motion has been interpreted as relativistically moving out flow. The increasing observations of such sources provide chance to investigate their mechanism in detail. This paper proposes that superluminal motion may be jet precession induced blob motion. This model can interpret a number of observational phenomena which are not well understood under the scenario of bulk motion, such as the absence of the receding blob after the outburst and the receding blob becomes brighter than the approaching one in XTE J1550-564 . Moreover the compton scattering of photos from a warped accretion disk may form a structured jet. And the precession of the structured jet may lead to the complicated state transitions observed in microquasars like GRS 1915+105. Applying to AGNs, the model may explain the scales of length and time of the phenomena proportioning to the mass of the black hole. The new model can be tested easily on microquasars, i.e., XTE J1550-564, on which the previous receding blob should move towards the core instead of away from it after 2002, and the previous approaching blob shall disappear. %For GRS 1915+105 the vibration of the two blobs should be observed in both %the time scales of year and days.

astro-ph↗

arXiv2006

On the nature of the radio quiet X-ray neutron star 1E 1207.4-5209

The strange timing property of X-ray pulsar 1E 1207.4-5209 can be explained by the hypothesis that it is a member of an ultra-compact binary system. This paper confronts the ultra-compact assumption with the observed properties of this pulsar. The gravitational potential well of an ultra-compact binary can enlarge the corotation radius and thus make it possible for accreting material to reach the surface of the NS in the low accretion rate case. Thus the generation of the absorption features should be similar to the case of accreting pulsars. The close equality of the energy loss by fast cooling of the postsupernova neutron star and the energy dissipation needed for a wide binary evolving to an ultra-compact binary demonstrates that the ultra-compact binary may be formed in 10-100yr after the second supernova explosion. Moreover, the ultra-compact binary hypothesis can well explain the the absence of optical counterpart and the observed two black body emissions. We suggest a simple method which can test the binary nature directly with XMM-Newton and Chandra observations. We further predict that the temperature of the two black bodies should vary at different pulse periods.

astro-ph↗

arXiv2005

The same physics underlying SGRs, AXPs, and radio pulsars

Unexpected sign, significant magnitude and time-variation of frequency second derivative exist not only in singular radio pulsars but also in Soft Gamma repeaters (SGRs) and Anomalous X-ray pulsars (AXPs). This paper shows that the these phenomena are related, and can be interpreted by a simple unified model, long-term orbital effect. Thus many of previous ``isolated'' pulsars may be binary pulsars, i.e., orbital period $P_b\approx(47, 72)$min for AXP 1E 2259+586, and $P_b\approx (20, 34)$min for PSR J1614-5047, $P_b\approx (3.6, 6.4)$min for SGR 1900+14, and $P_b\approx (1.5, 5.8)$min for SGR 1806-20. In addition to X-ray pulsar, 1E 1207.4-5209, these two SGRs may be the new ultra-compact binary pulsars with orbital period of a few minutes. There might be more binary pulsars that suitable for gravitational wave detection than we had thought.

astro-ph↗

arXiv2005

The precession of orbital plane and the significant variabilities of binary pulsars

There are two kinds of expressions on the precession of orbital plane of a binary pulsar system, which are given by Barker $&$ O'Connell (1975) and Apostolatos et al. (1994), Kidder (1995) respectively. This paper points out that these two kinds of orbital precession velocities are actually obtained by the same Lagrangian under different degrees of freedom. Correspondingly the former expression is not consistent with the conservation of the total angular momentum vector; whereas the latter one is. Damour $&$ Schäfer (1988) and Wex $&$ Kopeikin (1999) have applied Barker $&$ O'Connell's orbital precession velocity in pulsar timing measurement. This paper applies Apostolatos et al. $&$ Kidder's orbital precession velocity in pulsar timing measurement. We analyze that Damour $&$ Schäfer's treatment corresponds to negligible Spin-Orbit induced precession of periastron. Whereas the effects corresponding to Wex $&$ Kopeikin and this paper are both significant (however they are not equivalent). The observational data of two typical binary pulsars, PSR J2051-0827 and PSR J1713+0747 apparently support significant Spin-Orbit coupling effect. Further more, the discrepancies between Wex $&$ Kopeikin and this paper can be tested on specific binary pulsars with orbital plane nearly edge on. If the orbital period derivative of double-pulsar system PSRs J0737-3039 A and B, with orbital inclination angle $i=87.7_{-29}^{+17}$deg, is much larger than that of the gravitational radiation induced one, then the expression of this paper is supported, otherwise Wex $&$ Kopeikin's expression is supported.

astro-ph↗