The rapid neutron-capture process (r-process) is widely regarded as the dominant mechanism responsible for the synthesis of heavy elements in the universe, yet its astrophysical sites remain an open question. Recent studies suggest that the high-entropy, rapidly expanding baryonic material ejected by magnetar giant flares may provide favorable conditions for r-process nucleosynthesis, while the late-time gamma-ray emission observed from the magnetar SGR 1806-20 offers direct observational support for this scenario. In this work, we perform nuclear reaction network simulations to investigate the nucleosynthesis yields of magnetar giant flares and to characterize the associated nuclear gamma-ray line emission arising from the radioactive decay of heavy nuclei. The nuclei synthesized in magnetar giant flares are found to be mainly distributed near the first and second r-process abundance peaks. Owing to this nuclide composition, the gamma-ray opacity is found to be strongly energy-dependent, with the opacity in the keV band exceeding that in the MeV band by approximately three orders of magnitude. The nuclear gamma-ray emission is dominated by MeV photons at early times (t ≲ 103 s) and gradually extends toward the sub-MeV and keV bands as time progresses, thereby offering a diagnostic of heavy element enrichment in the ejecta. The gamma-ray spectrum exhibits a peak near ∼ 1 MeV with major contributions from 88Kr and 92Sr, whose radioactive decays produce several bright gamma-ray lines with fluxes exceeding ∼ 10−8 erg cm−2 s−1, making them the most promising lines for detection by MeV gamma-ray detectors. Because magnetar giant flares occur in the Galaxy at a rate roughly three orders of magnitude higher than neutron star mergers and their nuclear gamma-ray lines are accessible to current MeV instruments, they offer new and valuable science opportunities for MeV gamma-ray astronomy.

The gamma-ray light curve of long-duration GRB 220711B, is characterized by a multipeaked structure with a duration lasting '105 s. More interestingly, the X-ray afterglow light curve is composed of a plateau emission smoothly connected with a similar to t(-2) segment overlapping some flares followed by an extremely steep decay. By analysing the light curves of both prompt emission and X-ray afterglow, no high-confidence-level quasi-periodic oscillation (QPO) signals are found in the light curves of the prompt emission (e.g. Burst Alert Telescope and Gamma-ray Burst Monitor), but it is found that a QPO signal at '50 s above 6cr confidence level indeed exist in the X-ray afterglow. Here, we propose that a supra-massive magnetar as the central engine of GRB 220711B with precession motion is a good interpretation of the features of the X-ray emission. The initial plateau emission and followed decay segment, as well as the extremely steep-decay segment, are consistent with the physical process of supra-massive magnetar spin-down and then collapse into black hole. Moreover, the QPO signal in the X-ray emission can be explained as an effect of the precession motion of the magnetar. If this is the case, one can derive various magnetar parameters such as the initial period ( P-0 ) and surface magnetic field strength ( B-p ) within a pseudo-redshift range of [1.08, 4.27]. By considering beaming corrections with jet opening angle 5 degrees, we find that P-0 and B-p lie within the range of [1.87, 6.25] ms and [1 . 47 x 10(16) , 3 . 09 x 10(16) ] G, respectively. The parameter of Bp is slightly larger than that of other typical long-duration GRBs, but P-0 fall in a reasonable range.

Gamma-ray bursts (GRBs), among the most energetic transients in the Universe, are traditionally classified into long-duration GRBs (lasting more than two seconds) and short-duration GRBs (lasting less than two seconds)\cite{Kouveliotou1993}. Long-duration GRBs are typically associated with the core collapse of massive stars (Type II), whereas short-duration GRBs originate from the merger of compact binary systems (Type I)\cite{Woosley2006, Zhang2006Natur, Zhang2009b, Berger2014}. Owing to their distinct physical origins, the two classes exhibit markedly different observational properties, which serve as key diagnostic criteria for GRB classification\cite{Norris2000, Zhang2009b, Lv2010, Lv2014, Qin2013, Li2016, Minaev2020}. Here we report a peculiar gamma-ray burst, GRB 160425A, comprising a short-sharp duration burst ($G_1$) followed by a long-broad duration burst ($G_2$), separated by only four minutes. Strikingly, nearly all standard prompt-emission observational diagnostics, including pulse morphology\cite{Norris2005}, duration\cite{Kouveliotou1993}, hardness ratio \cite{Horvath2010, Goldstein2017}, minimum variability timescale\cite{Golkhou2014, Golkhou2015}, spectral properties \cite{Dezalay1992}, spectral lag\cite{Norris2000,Norris2006, Yi2006, Bernardini2015}, and established empirical correlations (the Amati and Norris relations \cite{Amati2002, Norris2000}), consistently categorize $G_1$ as a short-like (Type-I, merger-origin) GRB and $G_2$ as a long-like (Type-II, collapsar-origin) GRB. The coexistence of merger and collapsar signatures within a single event challenges existing progenitor frameworks, calling for a fundamental re-evaluation of GRB classification schemes and progenitor scenarios.

High-frequency gravitational-wave (GW) radiation has been detected by LIGO-Virgo-KAGRA in the merger of compact stars. However, in two GW events, GW190814 and GW200210, the mass of one companion object falls into the mass region of (2.2–3) M _⊙ , and how to identify such an object (e.g., as a low-mass black hole (BH) or a massive neutron star (NS)) remains an open question. In this paper, we propose a method to identify the mystery compact object (MCO) with the mass region of (2.2–3) M _⊙ in a binary system via the possible electromagnetic (EM) radiations before and after the mergers. A multiband EM emission can be produced with L ∝ ( − t ) ^7/4 (or L ∝ ( − t ) ^−5/4 ) during the inspiral phase due to the BH battery (or interaction magnetospheres) mechanism, and a bright (or dark) kilonova emission is powered by radioactive decay with ejecta mass ratio q > 1.7 (or q < 1.7) during the postmerge state when MCO is as a low-mass BH (or massive NS) to merger with NS. Moreover, by considering the merger system between MCO and a BH when MCO is a massive NS, we find that it requires the BH with high spin (e.g., a ∼ 0.8–0.99) to make sure the tidal disruption event occurred, and a multiband precursor emission and bright kilonova emission can also be produced during the inspiral phase and postmerge state, respectively. In any case, no matter which mechanism we adopt, such precursor emissions are too weak to be detected by most current telescopes unless the distance is close enough.

GRB 240529A is a long-duration gamma-ray burst (GRB) whose light curve of prompt emission is composed of a triple-episode structure, separated by quiescent gaps of tens to hundreds of seconds. More interestingly, its X-ray light curve of afterglow exhibits two plateau emissions, namely, an internal plateau emission that is smoothly connected with a ∼ t ^−0.1 segment and followed by a ∼ t ^−2 power-law decay. The three episodes in the prompt emission, together with two plateau emissions in X-ray, are unique in the Swift era. They are very difficult to explain with the standard internal/external shock model by invoking a black hole central engine. However, it could be consistent with the prediction of a supramassive magnetar as the central engine, the physical process of phase transition from a magnetar to a strange star, as well as the cooling and spin-down of the strange star. In this paper, we propose that the first- and second-episode emissions in the prompt gamma ray of GRB 240529A are from the jet emission of a massive star collapsing into a supramassive magnetar and the reactivity of the central engine, respectively. Then, the third-episode emission of the prompt is attributed to the phase transition from a magnetar to a strange star. Finally, the first and second plateau emissions of the X-ray afterglow are powered by the cooling and spin-down of the strange star, respectively. The observational data of each component of GRB 240529A are roughly coincident with the estimations of the above physical picture.

Long-duration GRB 211211A, which lacked an associated supernova at very a low redshift z = 0.076 but was associated with a possible kilonova emission, has attracted great attention. The neutron star–white dwarf (NS–WD) merger is proposed as a possible progenitor of GRB 211211A, and it could naturally explain the long duration of the prompt emission. However, the NS–WD merger is not an ideal site for producing heavy elements via r -process nucleosynthesis. In this Letter, we investigate the heavy elements produced in NS–WD mergers based on numerical simulations of nucleosynthesis via SkyNet and then calculate the resulting kilonova-like emission to compare with the solidly observed case of possible kilonova emission associated with GRB 211211A. By adopting three models (i.e., Model-A, Model-B, and Model-C) from M. A. R. Kaltenborn et al. at different temperatures ( T = 4, 5, and 6 GK), which are treated as free parameters, we find that the mass number of the heaviest element produced in our simulations is less than 90 ( A < 90). Moreover, by comparing the calculated kilonova-like emission with the afterglow-subtracted observations of the possible kilonova associated with GRB 211211A, it is found that the merger of an NS and WD cannot be ruled out as the origin of GRB 211211A to produce the possible kilonova emission if the remnant of the WD–NS merger is a supramassive or stable magnetar. Otherwise, it is difficult to explain the early possible kilonova emission following GRB 211211A by invoking the merger of a WD and an NS.

The determination of the equation of state (EOS) of a neutron star (NS) and its maximum mass is very important for understanding the formation and properties of NSs under extreme conditions, but they remain open questions. Short-duration gamma-ray bursts (GRBs) are believed to originate from the merger of binary NSs or giant flares (GFs) of soft gamma repeaters (SGRs). Recently, the high-frequency quasi-periodic oscillations (QPOs) have been claimed to be identified from two short GRBs (GRB 931101B and GRB 910711). In this paper, we propose that the observed high-frequency QPOs in these two short GRBs result from torsional oscillations in the GFs of SGRs associated with cold NSs, or from radial oscillations of hypermassive NSs as the hot remnants of binary NS mergers, and then to constrain the EOS of NSs. For torsional oscillations, the six selected EOSs (TM1, NL3, APR, SLy4, DDME2, and GM1) of NSs suitable for the zero-temperature condition exhibit significant overlap in mass ranges, suggesting that we cannot constrain the EOS of NSs. For radial oscillations, the six selected EOSs (IUF, TM1, TMA, FSG, BHBLp, and NL3) of NSs suitable for the high-temperature condition cannot be ruled out when redshift is considered. However, it is found that the EOS can only be constrained if the redshift and temperature of the remnant can be measured.

The first direct detection of the gravitational wave (GW) event GW170817 and its electromagnetic (EM) counterpart open a new window for studying of multimessenger astronomy. However, how to identify the remnant of binary neutron star (NS) merger via EM radiation remain an open question. In this paper, we propose a method of colour evolution of kilonova emission to identify its progenitors. We assume that the energy of the kilonova is contributed from radioactive decay, magnetar spin-down, and pulsar wind nebula (PWN). The colour evolution of kilonova emission associated with short GRB is significant when the spectrum is thermal emission, while it tends towards a constant when the spectrum is non-thermal radiation. On the other hand, if the central engine is a black hole (BH) which is promptly generated by the NS-NS merger or NS-BH merger, then the kilonova is powered only by the radioactive decay. There is no colour evolution at the beginning before the peak of kilonova emission, but is significantly and rapidly increasing after the peak. On the contrary, if the central engine is a magnetar or stable NS, the kilonova emission is contributed from radioactive decay, magnetar, and PWN. The colour evolution after the peak of kilonova emission is complex behaviour which depends on the rotational energy and spin-down time-scale of magnetar, and finally tend to a constant in the late state.

Rapidly rotating newborn magnetars, which originate from binary neutron star (NS) mergers and serve as the central engines of short gamma-ray bursts (GRBs), may leave some imprints on their prompt gamma-ray lightcurves even though they are far from their radiating fireballs. A high-frequency quasi-periodic oscillation (QPO) would be a unique feature for the magnetar central engine, especially a hypermassive magnetar. By conducting a systematic analysis of the prompt gamma-ray lightcurves from 605 short GRBs observed by Fermi/GBM, we have identified such QPO signals in three GRBs (e.g. GRB 120323A, GRB 181222B, and GRB 190606A). The QPOs that peaked at $1258^{+6}_{-6}$ Hz for GRB 120323A, $623^{+4}_{-4}$ Hz for GRB 181222B, and $1410^{+4}_{-5}$ Hz for GRB 190606A are all with a confidence level above 5.2 σ. The high-frequency QPO signals of those three short GRBs may be caused by a hypermassive magnetar acting as the central engine in a binary neutron star merger of binary neutron star.

Short gamma-ray bursts (SGRBs) with extended emission (EE) are composed of initial main emission with a short-hard spike (ME) and followed by a long-lasting EE. Whether the ME and EE originated from the same origin or not, as well as the jet composition, remains an open question. In this paper, we present a systematic analysis to search for 36 GRBs in our sample, which are identified as the category of SGRBs with EE as observed by Fermi/GBM. By extracting time-integrated spectra of ME and EE with CPL or Band models for our sample, we find that 20 out of 36 SGRBs for which α values are exceeding the death line (e.g., -2/3) of synchrotron emission within either ME or EE phases, and suggest that the quasi-thermal component should exist in the prompt emission. Then, we extract the time-resolved spectra of our samples, but only four GRBs are bright enough to extract the time-resolved spectra. We find that both thermal and non-thermal emissions do exist in the prompt emission of those four bright GRBs, and it suggests that a hybrid jet (e.g., matter and Poynting-flux outflow) in GRB should exist. Moreover, strong positive correlations (e.g., F_ tot-Γ and F_ tot-kT) in the time-resolved spectra of ME and EE for those four GRBs are discovered. It indicates that the spectral evolution of both ME and EE seem to share similar behavior, possibly from the same physical origin.

The prompt emission mechanism of gamma-ray bursts (GRBs) is a long-standing open question, and GRBs have been considered as potential sources of high-energy neutrinos. Despite many years of search for the neutrino events associated with GRBs from IceCube, there were no results. However, the absence of search results for neutrinos provides a unique opportunity to constrain the parameter space of GRB jet models. In this paper, we chose four peculiar GRBs with two different types of jet composition to investigate neutrino emission. It is found that only GRB 211211A could be well constrained within the dissipative photosphere model. By adopting the specific parameters of the photosphere, one can obtain ε _ p/ε_ e<8 for f_ p>0.2 from GRB 211211A. For the Internal-collision-induced Magnetic Reconnection and Turbulence (ICMART) model, we can effectively constrain neither GRB 230307A nor GRB 080916C. Moreover, we also investigate the detection prospects of high-energy neutrinos from GRBs and find that it is difficult to detect at least one high-energy neutrino associated with GRBs from the ICMART model even during the IceCube-Gen2 operation. For the GRB 211211A-like events, it is possible to detect at least one neutrino coincident with the gravitational wave during the IceCube-Gen2 operation, if such an event originated from mergers of compact stars within the photosphere dissipation.

The nearby long-duration GRB 191019A recently detected by Swift lacks an associated supernova and belongs to a host galaxy with little star formation activity, suggesting that the origin of this burst is the result of a merger of two compact objects with dynamical interactions in a high-density medium of an active galactic nucleus. Given the potential motivation of this event, and given that it occurs in such a high-density environment, the ejecta–circumstellar medium (CSM) interaction cannot be ignored as possibly contributing to the kilonova emission. Here, we theoretically calculate the kilonova emission by considering the contribution of the ejecta–CSM interaction in a high-density environment. We find that the contribution to the kilonova emission from the ejecta–CSM interaction will dominate at a later time, and a smaller ejecta mass will have a stronger kilonova emission from the ejecta–CSM interaction. Moreover, we try to apply it to GRB 191019A, but we find that it is difficult to identify the possible kilonova emission from the observations, due to the contribution of the bright host galaxy. On the other hand, less injected mass (less than M _ej = 2 × 10 ^−5 M _⊙ ) will be required if one can detect the kilonova emission associated with a GRB 191019A–like event in the future. The r -process-powered and spin energy contributions from the magnetar are also discussed.

Recently, the detection of a coherent radio flash associated with short-duration GRB 201006A, occurring 76.6 minutes after the burst, has attracted great attention. However, the physical origin of the coherent radio flash remains under debate. By reanalyzing its data observed by Fermi and Swift, we find that an early radio afterglow as the physical origin of the radio flash can be ruled out, but the coherent radio emission seems to be consistent with the hypothesis of a supramassive magnetar as the central engine collapsing into a black hole. Within this scenario, the derived magnetar surface magnetic field (B p ) and the initial spin period (P 0) fall into a reasonable range but require a preferably low value of eta R = 10-7 or 10-6. Moreover, the calculated low-epsilon value and E gamma,iso-E p correlation of GRB 201006A also supports the progenitor which is from the merger of compact stars. We also discuss the non-detected kilonova emission associated with GRB 201006A, and then compare with its upper limits of optical observations.

Long-duration gamma-ray bursts (GRBs) are thought to be from core collapse of massive stars, and a rapidly spinning magnetar or black hole may be formed as the central engine. The extended emission in the prompt emission, flares, and plateaus in X-ray afterglow, are proposed to be as the signature of central engine re-activity. However, the direct evidence from observations of identifying the central engines remains an open question. In this paper, we systemically search for long-duration GRBs that consist of bumps in X-ray afterglow detected by Swift/XRT and find that the peak time of the X-ray bumps exhibit bimodal distribution (defined as 'early' and 'late' bumps) with division line at t = 7190 s. Although we cannot rule out that such a bimodality arises from selection effects. We proposed that the long-duration GRBs with an early (or late) bumps may be originated from the fall-back accretion onto a new-born magnetar (or black hole). By adopting Monte Carlo Markov Chain (MCMC) method to fit the early (or late) bumps of X-ray afterglow with the fall-back accretion of magnetar (or black hole), it is found that the initial surface magnetic field and period of magnetars for most early bumps are clustered around 5.88 x 10(13) G and 1.04 ms, respectively. Meanwhile, the derived accretion mass of black hole for late bumps is in the range of [4 x 10(-4) , 1.8 x 10(-2)]M-Theta, and the typical fall-back radius is distributed range of [1.04 , 4.23] x 10(11) cm, which is consistent with the typical radius of a Wolf-Rayet star. However, we also find that the fall-back accretion magnetar model is disfavoured by the late bumps, but the fall-back accretion of black hole model cannot be ruled out to interpret the early bumps of X-ray afterglow.

Magnetars are potential energy sources or central engines for numerous transient phenomena in the Universe. How newborn magnetars evolve in different environments remains an open question. The majority of previous studies on the evolution of newborn magnetars considered either the spin evolution, inclination evolution, or magnetic field evolution in vacuum or in a plasma-filled magnetosphere. Based on both observed and candidate magnetars, it is found that the periods of all magnetars or candidates appear as a bimodal distribution, and are defined as the "long- P " and "short- P " magnetar subclasses, respectively. We find that for the short- P subclass of magnetars, the P (center dot) values also appear as a bimodal distribution, and therefore can be classified as "high- P (center dot) short- P " and "low- P (center dot) short- P " magnetar subclasses. In this paper, we use Monte Carlo simulations to generate synthetic magnetar populations and investigate the evolution of the high- P (center dot) short- P and low- P (center dot) short- P magnetar subclasses by considering both the magnetar spin and inclination, as well as the decay of their magnetic field within their evolution in both vacuum and plasmafilled magnetospheres. We find that the magnetar evolution is dependent on both spin and magnetic field, but seems to be insensitive to inclination evolution and magnetospheric environment for the high- P (center dot) short- P subclass. In comparison for the case of high- P (center dot) short- P, the magnetar evolution is dependent on spin, magnetic field, and inclination evolution, as well as the magnetospheric environment. The best evolution model should be the case of inclination evolution in vacuum with a small value of FOM. The differences in the best-fit parameters also suggest that the high- P (center dot) short- P and low- P (center dot) short- P magnetar subclasses may be tracking with different evolution channels.

Short gamma-ray bursts (SGRBs) with extended emission (EE) are composed of initial main emission (ME) with a short hard spike, followed by a long-lasting EE. Whether the ME and EE originated from the same origin or not, as well as the jet composition, remains an open question. In this paper, we present a systematic analysis of 36 gamma-ray bursts (GRBs) in our sample, which are identified as the category of SGRBs with EE as observed by Fermi/Gamma-ray Burst Monitor. By extracting time-integrated spectra of ME and EE with cutoff power-law or Band models for our sample, we find that 20 out of 36 SGRBs have alpha values that exceed the death line (e.g., -2/3) of synchrotron emission within either ME or EE phases, and we suggest that the quasi-thermal component should exist in the prompt emission. Then, we extract the time-resolved spectra of our samples, but only four GRBs are bright enough to extract the time-resolved spectra. We find that both thermal and nonthermal emissions do exist in the prompt emission of those four bright GRBs, which suggests that a hybrid jet (e.g., matter and Poynting-flux outflow) in GRBs should exist. Moreover, strong positive correlations (e.g., F tot-Gamma and F tot-kT) in the time-resolved spectra of ME and EE for those four GRBs have been discovered. This indicates that the spectral evolution of both ME and EE seem to share similar behavior, possibly from the same physical origin.

The prompt emission, X-ray plateau, and X-ray flares of gamma-ray bursts (GRBs) are thought to be from internal dissipation, and the magnetar as the central engine with propeller fallback accretion is proposed to interpret the observed phenomena of GRBs. In this paper, by systematically searching for X-ray emission observed by Swift/X-ray Telescope, we find that seven robust GRBs include both X-ray flares and plateau emissions with measured redshift. More interestingly, the X-ray flares/bumps for those seven GRBs are simultaneously observed in the gamma-ray band. By adopting the propeller fallback accretion model to fit the observed data, it is found that the free parameters of two GRBs (140512A and 180329B) can be constrained very well, while in the other five cases, more or less, they are not all sufficiently constrained. On the other hand, this requires the conversion efficiency of the propeller to be two or three times higher than that of the spindown dipole radiation of the magnetar. If this is the case, it is contradictory to the expectation from the propeller model: namely, a dirtier ejecta should be less efficient in producing gamma-ray emissions. Our results hint that at least the magnetar central engine with propeller fallback accretion model cannot interpret very well both the GRB X-ray flares simultaneously observed in the gamma-ray band and the X-ray flares of GRBs with a high Lorentz factor.

Recently, a lack of supernova-associated with long-duration gamma-ray burst (GRB 230307A) at such a low redshift z = 0.065, but associated with a possible kilonova emission, has attracted great attention. Its heavy element nucleosynthesis and the characteristic of soft X-ray emission suggest that the central engine of GRB 230307A is a magnetar that is originated from a binary compact star merger. The calculated lower value of ε ∼ 0.05 suggests that GRB 230307A seems to have an ambiguous progenitor. The lower value of f _eff = 1.23 implies that GRB 230307A is not likely to be from the effect of “tip of iceberg.” We adopt the magnetar central engine model to fit the observed soft X-ray emission with varying efficiency and find that the parameter constraints of the magnetar falls into a reasonable range, i.e., B < 9.4 × 10 ^15 G and P < 2.5 ms for Γ _sat = 10 ^3 , and B < 3.6 × 10 ^15 G and P < 1.05 ms for Γ _sat = 10 ^4 . Whether the progenitor of GBR 230307A is from the mergers of neutron star–white dwarf (NS–WD) or neutron star–neutron star (NS–NS) remains unknown. The difference of GW radiation between NS–NS merger and NS–WD merger may be a probe to distinguish the progenitor of GRB 230307A-like events in the future.

ABSTRACT Gravitational waves (GWs) from core-collapse supernovae (CCSNe) have been proposed as a probe to investigate the physical properties inside supernovae. However, how to search for and extract the GW signals from CCSNe remains an open question owing to their complicated time–frequency structure. In this paper, we apply the ensemble empirical mode decomposition (EEMD) method to decompose and reconstruct simulated GW data generated by the magnetorotational mechanism and the neutrino-driven mechanism within the Advanced LIGO, using the match score as the criterion for assessing the quality of the reconstruction. The results indicate that by decomposing the data, the sum of the first six intrinsic mode functions (IMFs) can be used as the reconstructed waveform. To determine the probability that our reconstructed waveform corresponds to a real GW waveform, we calculate the false alarm probability of reconstruction (FAPR). By setting the threshold of the match score to be 0.75, we obtain the FAPRs of GW sources at distances of 5 and 10 kpc to be 6 × 10−3 and 1 × 10−2, respectively. If we normalize the maximum amplitude of the GW signal to 5 × 10−21, the FAPR at this threshold is 4 × 10−3. Furthermore, in our study, the reconstruction distance is not equivalent to the detection distance. When the strain of GWs reaches 7 × 10−21, and the match score threshold is set at 0.75, we can reconstruct GW waveforms up to approximately 36 kpc.

The nature of the merger remnant of binary neutron star (BNS) remains an open question. From the theoretical point of view, one possible outcome is a supra-massive neutron star (SMNS), which is supported by rigid rotation and through its survival of hundreds of seconds before collapsing into a black hole (BH). If this is the case, the SMNS can emit continuous gravitational waves (GW) and electromagnetic (EM) radiation, particularly in the X-ray band. In this work, the ellipticity and initial frequency of SMNS are constrained with a Bayesian framework using simulated X-ray and GW signals, which could be detected by The Transient High Energy Sky and Early Universe Surveyor (THESEUS) and Einstein Telescope (ET), respectively. We found that only considering the X-ray emission can not completely constrain the initial frequency and ellipticity of the SMNS, but it can reduce the ranges of the parameters. Afterwards, we can use the posterior distribution of the X-ray parameter estimates as a prior for the GW parameter estimates. It was found that the 95$\%$ credible region of the joint X-ray-GW analysis was about $10^5$ times smaller than that of the X-ray analysis alone.