arXiv subjects

F. Y. Wang

Publications and source records attributed to F. Y. Wang.

At least 91 records · Page 5Linked to original sources

arXiv2018

Testing the Distance-Duality Relation in the $R_h=ct$ Universe

In this paper, we test the cosmic distance duality (CDD) relation using the luminosity distances from joint light-curve analysis (JLA) type Ia supernovae (SNe Ia) sample and angular diameter distance sample from galaxy clusters. The $R_h=ct$ and $Λ$CDM models are considered. In order to compare the two models, we constrain the CCD relation and the SNe Ia light-curve parameters simultaneously. Considering the effects of Hubble constant, we find that $η\equiv D_A(1+z)^2/D_L=1$ is valid at the 2$σ$ confidence level in both models with $H_0 = 67.8\pm0.9$ km/s/Mpc. However, the CDD relation is valid at 3$σ$ confidence level with $H_0 = 73.45\pm1.66$ km/s/Mpc. Using the Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC), we find that the $Λ$CDM model is very strongly preferred over the $R_h=ct$ model with these data sets for the CDD relation test.

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arXiv2018

Lensing of Fast Radio Bursts by Binaries to Probe Compact Dark Matter

The possibility that a fraction of the dark matter is comprised of massive compact halo objects (MACHOs) remains unclear, especially in the 20-100 $M_{\odot}$ window. MACHOs could make up binaries, whose mergers may be detected by LIGO as gravitational wave events. On the other hand, the cosmological origin of fast radio burst (FRBs) has been confirmed. We investigate the possibility of detecting fast radio bursts (FRBs) gravitational lensed by MACHO binaries to constrain their properties. Since lensing events could generate more than one images, lensing by binaries could cause multiple-peak FRBs. The angular separation between these images is roughly $10^{-3}$ mas, which is too small to be resolved. The typical time interval between different images is roughly 1 millisecond (ms). The flux ratio between different images is roughly from 10 to $10^3$. With the expected detection rate of $10^4$ FRBs per year by the upcoming experiments, we could expect five multi-peak FRBs observed per year with time interval larger than 1 ms and flux ratio less than $10^3$ if the fraction of dark matter in MACHOs is $f\sim0.01$. A null search multiple-peak FRBs for time interval larger than 1 ms and flux ratio less than $10^3$ with $10^4$ FRBs would constrain the fraction $f$ of dark matter in MACHOs to $f<0.001$.

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arXiv2017

The formation rate of short gamma-ray bursts and gravitational waves

In this paper, we study the luminosity function and formation rate of short gamma-ray bursts (sGRBs). Firstly, we derive the $E_p-L_p$ correlation using 16 sGRBs with redshift measurements and determine the pseudo redshifts of 284 Fermi sGRBs. Then, we use the Lynden-Bell c$^-$ method to study the luminosity function and formation rate of sGRBs without any assumptions. A strong evolution of luminosity $L(z)\propto (1+z)^{4.47}$ is found. After removing this evolution, the luminosity function is $ Ψ(L) \propto L_0 ^ {- 0.29 \pm 0.01} $ for dim sGRBs and $ ψ(L) \propto L_0 ^ {- 1.07 \pm 0.01} $ for bright sGRBs, with the break point $8.26 \times 10^{50} $ erg s$^{-1}$. We also find that the formation rate decreases rapidly at $z<1.0$, which is different with previous works. The local formation rate of sGRBs is 7.53 events Gpc$^{-3}$ yr$^{-1}$. Considering the beaming effect, the local formation rate of sGRBs including off-axis sGRBs is $ 203.31^{+1152.09}_{-135.54} $ events Gpc$^{-3}$ yr$^{-1}$. We also estimate that the event rate of sGRBs detected by the advanced LIGO and Virgo is $0.85^{+4.82}_{-0.56} $ events yr$^{-1}$ for NS-NS binary.

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arXiv2017

Short Gamma-Ray Bursts and Gravitational-Wave Observations from Eccentric Compact Binaries

Mergers of compact binaries, such as binary neutron stars (BNSs), neutron star-black hole binaries (NSBHs), and binary black holes (BBHs), are expected to be the best candidates for the sources of gravitational waves (GWs) and the leading theoretical models for short gamma-ray bursts (SGRBs). Based on the observations of SGRBs, we could derive the merger rates of these compact binaries, and study the stochastic GW backgrounds (SGWBs) or the co-detection rates of GWs associate with SGRBs (GW-SGRBs). But before that, the most important thing is to derive the GW spectrum from a single GW source. Usually, GW spectrum from a circular orbit binary is assumed. However, observations of the large spatial offsets of SGRBs from their host galaxies imply that SGRB progenitors may be formed by the dynamical processes, and will merge with residual eccentricities. The orbital eccentricity has important effect on GW spectra, and therefore on the SGWB and GW-SGRB co-detection rate. Our results show that the power spectra of the SGWBs from eccentric compact binaries are greatly suppressed at low frequencies. Especially, SGWBs from binaries with high residual eccentricities will hard to be detected (above the detection frequency of $\sim100~\rm Hz$). For the co-detection rates of GW-SGRB events, they could be $\sim1.4$ times higher than the circular case within some particular ranges of $e_{\rm r}$ , but greatly reduced for high residual eccentricities (e.g., $e_{\rm r}>0.1$ for BNSs). In general, the BBH progenitors produce 200 and 10 times higher GW-SGRB events than the BNS and NSBH progenitors, respectively. Therefore, binaries with low residual eccentricities and high total masses will easier to be detected by aLIGO.

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arXiv2017

Testing the isotropy of the Universe with type Ia supernovae in a model-independent way

In this paper, we study an anisotropic universe model with Bianchi-I metric using Joint Light-curve Analysis (JLA) sample of type Ia supernovae (SNe Ia). Because light-curve parameters of SNe Ia vary with different cosmological models and SNe Ia samples, we fit the SNe Ia light-curve parameters and cosmological parameters simultaneously employing Markov Chain Monte Carlo method. Therefore, the results on the amount of deviation from isotropy of the dark energy equation of state ($δ$), and the level of anisotropy of the large-scale geometry ($Σ_0$) at present, are totally model-independent. The constraints on the skewness and cosmic shear are $-0.101<δ<0.071$ and $-0.007<Σ_0<0.008$. This result is consistent with a standard isotropic universe ($δ=Σ_0=0$). However, a moderate level of anisotropy in the geometry of the Universe and the equation of state of dark energy, is allowed. Besides, there is no obvious evidence for a preferred direction of anisotropic axis in this model.

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arXiv2017

A rapid cosmic-ray increase in BC 3372-3371 from ancient buried tree rings in China

Cosmic rays interact with the Earth's atmosphere to produce $^{14}$C, which can be absorbed by trees. Therefore, rapid increases of $^{14}$C in tree rings can be used to probe previous cosmic-ray events. By this method, three $^{14}$C rapidly increasing events have been found. Plausible causes of these events include large solar proton events, supernovae or short gamma-ray bursts. However, due to the lack of measurements of $^{14}$C by year, the occurrence frequency of such $^{14}$C rapidly increasing events is poorly known. In addition, rapid increases may be hidden in the IntCal13 data with five-year resolution. Here we report the result of $^{14}$C measurements using an ancient buried tree during the period between BC 3388 and 3358. We find a rapid increase of about 9\textperthousand~ in the $^{14}$C content from BC 3372 to BC 3371. We suggest that this event could originate from a large solar proton event.

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arXiv2017

Measuring the cosmic proper distance from fast radio bursts

The cosmic proper distance $d_P$ is a fundamental distance in the Universe. Unlike the luminosity and angular diameter distances, which correspond to the angular size, the proper distance is the length of light path from the source to observer. However, the proper distance has not been measured before. The recent redshift measurement of a repeat fast radio burst (FRB) can shed light on the proper distance. We show that the proper distance-redshift relation can indeed be derived from dispersion measures (DMs) of FRBs with measured redshifts. From Monte Carlo simulations, we find that about 500 FRBs with DM and redshift measurements can tightly constrain the proper distance-redshift relation. We also show that the curvature of our Universe can be constrained with a model-independent method using this derived proper distance-redshift relation and the observed angular diameter distances. Owing to the high event rate of FRBs, hundreds of FRBs can be discovered in the future by upcoming instruments. The proper distance will play an important role in investigating the accelerating expansion and the geometry of the Universe.

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arXiv2017

Self-organized criticality in type I X-ray bursts

Type I X-ray bursts in a low-mass X-ray binary (LMXB) are caused by unstable nuclear burning of accreted materials. Semi-analytical and numerical studies of unstable nuclear burning have successfully reproduced partial properties of this kind of burst. However, some other properties (e.g. the waiting time) are not well explained. In this paper, we find that the probability distributions of fluence, peak count, rise time, duration and waiting time can be described as power-law-like distributions. This indicates that type I X-ray bursts may be governed by a self-organized criticality (SOC) process. The power-law index of waiting time distribution (WTD) is around $-1$, which is not predicted by any current waiting time model. We propose a physical burst rate model, in which the mean occurrence rate is inversely proportional to time $λ\propto t^{-1}$. In this case, the WTD is well explained by a non-stationary Poisson process within the SOC theory. In this theory, the burst size is also predicted to follow a power-law distribution, which requires that the emission area possesses only part of the neutron star surface. Furthermore, we find that the WTDs of some astrophysical phenomena can also be described by similar occurrence rate models.

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arXiv2017

Statistical Distributions of Optical Flares from Gamma-Ray Bursts

We statistically study gamma-ray burst (GRB) optical flares from the Swift/UVOT catalog. We compile 119 optical flares, including 77 flares with redshift measurements. Some tight correlations among the time scales of optical flares are found. For example, the rise time is correlated with the decay time, and the duration time is correlated with the peak time of optical flares. These two tight correlations indicate that longer rise times are associated with longer decay times of optical flares, and also suggest that broader optical flares peak at later times, which are consistent with the corresponding correlations of X-ray flares. We also study the frequency distributions of optical flare parameters, including the duration time, rise time, decay time, peak time and waiting time. Similar power-law distributions for optical and X-ray flares are found. Our statistic results imply that GRB optical flares and X-ray flares may share the similar physical origin and both of them are possibly related to central engine activities.

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arXiv2017

A universal scaling law of black hole activity including gamma-ray bursts

Previous works show that a correlation among radio luminosity, X-ray luminosity, and black hole (BH) mass from stellar-mass BHs in X-ray binaries to supermassive BHs in active galactic nuclei (AGNs), which leads to the so-called fundamental plane of BH activity. However, there are two competing explanations for this fundamental plane, including the jet-dominated model and the disk-jet model. Thus, the physical origin of this fundamental plane remains unknown. In this paper, we show that the X-ray luminosities, radio luminosities and BH masses of gamma-ray bursts (GRBs) and M82 X-1 also show a similar distribution. The universal scaling law among stellar-mass, intermediate and supermassive BH systems, together with the fact that radio and X-ray emission of GRBs originates from relativistic jets, reveals that the fundamental plane of BH activity is controlled by a jet, i.e., the radio and X-ray emission is mainly from the jet. Our work also suggests that the jets are scale-invariant with respect to the BH mass.

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arXiv2017

SGR-like behaviour of the repeating FRB 121102

Fast radio bursts (FRBs) are millisecond-duration radio signals occurring at cosmological distances. However the physical model of FRBs is mystery, many models have been proposed. Here we study the frequency distributions of peak flux, fluence, duration and waiting time for the repeating FRB 121102. The cumulative distributions of peak flux, fluence and duration show power-law forms. The waiting time distribution also shows power-law distribution, and is consistent with a non-stationary Poisson process. These distributions are similar as those of soft gamma repeaters (SGRs). We also use the statistical results to test the proposed models for FRBs. These distributions are consistent with the predictions from avalanche models of slowly driven nonlinear dissipative systems.

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arXiv2017

Investigating the effect of cosmic opacity on standard candles

Standard candles can probe the evolution of dark energy in a large redshift range. But the cosmic opacity can degrade the quality of standard candles. In this paper, we use the latest observations, including type Ia supernovae (SNe Ia) from JLA sample and Hubble parameters, to probe the opacity of the universe. In order to avoid the cosmological dependence of SNe Ia luminosity distances, a joint fitting of the SNe Ia light-curve parameters, cosmological parameters and opacity is used. In order to explore the cosmic opacity at high redshifts, the latest gamma-ray bursts (GRBs) are used. At high redshifts, cosmic reionization process is considered. We find that the sample supports an almost transparent universe for flat $Λ$CDM and XCDM models. Meanwhile, free electrons deplete photons from standard candles through the (inverse) Compton scattering, known as an important component of opacity. This Compton dimming may paly an important role in future supernova surveys. From analysis, we find that about a few percent cosmic opacity is caused by Compton dimming in the two models, which can be correctable.

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arXiv2016

New Model-independent Method to Test the Curvature of the Universe

We propose a new model-independent method to test the cosmic curvature by comparing the proper distance and transverse comoving distance. Using the measurements of Hubble parameter $H(z)$ and angular diameter distance $d_A$, the cosmic curvature parameter $Ω_K$ is constrained to be $-0.09\pm0.19$, which is consistent with a flat universe. We also use Monte Carlo simulation to test the validity and efficiency, and find that our method can give a reliable and efficient constraint on cosmic curvature. Compared with other model-independent methods testing the cosmic curvature, our method can avoid some drawbacks and give a better constraint.

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arXiv2016

Constraining warm dark matter mass with cosmic reionization and gravitational wave

We constrain the warm dark matter (WDM) particle mass with the observations of cosmic reionization and CMB optical depth. We suggest that the GWs from stellar mass black holes (BHs) could give a further constraint on WDM particle mass for future observations. The star formation rates (SFRs) of Population I/II (Pop I/II) and Population III (Pop III) stars are also derived. If the metallicity of the universe have been enriched beyond the critical value of $Z_{\rm crit}=10^{-3.5}Z_{\odot}$, the star formation shift from Pop III to Pop I/II stars. Our results show that the SFRs are quite dependent on the WDM particle mass, especially at high redshifts. Combing with the reionization history and CMB optical depth derived from the recent \emph{Planck} mission, we find that the current data requires the WDM particle mass in a narrow range of $1 < m_x < 3$ keV. Furthermore, we suggest that the stochastic gravitational wave background (SGWB) produced by stellar BHs could give a further constraint on the WDM particle mass for future observations. For $m_{x}=3$ keV with Salpeter (Chabrier) initial mass function (IMF), the SGWB from Pop I/II BHs has a peak amplitude of $Ω_{\rm GW}\approx2.8\times 10^{-9}~(5.0\times 10^{-9})$ at $f= 316 {\rm Hz}$, while the GW radiation at $f<10$Hz is seriously suppressed. For $m_{\rm x}=1$ keV, the SGWB peak amplitude is the same as that of $m_{\rm x}=1$ keV, but a little lower at low frequencies. Therefore, it is hard to constrain the WDM particle mass by the SGWB from Pop I/II BHs. To assess the detectability of GW signal, we also calculate the signal to noise ratio (SNR), which are $\rm SNR=37.7~ (66.5)$ and $27~(47.7)$ for $m_{\rm x}=3$ keV and $m_{\rm x}=1$ keV for Einstein Telescope (ET) with Salpeter (Chabrier) IMF, respectively.

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arXiv2016

Comprehensive study of the X-ray flares from gamma-ray bursts observed by Swift

X-ray flares are generally supposed to be produced by the later central engine activities, and may share the similar physical origin with prompt emission of gamma-ray bursts (GRBs). In this paper, we have analyzed all significant X-ray flares from the GRBs observed by {\em Swift} from April 2005 to March 2015. The catalog contains 468 bright X-ray flares, including 200 flares with redshifts. We obtain the fitting results of X-ray flares, such as start time, peak time, duration, peak flux, fluence, peak luminosity, and mean luminosity. The peak luminosity decreases with peak time, following a power-law behavior $L_p \propto T_{peak,z}^{-1.27}$. The flare duration increases with peak time. The 0.3-10 keV isotropic energy of X-ray flares distribution is a lognormal peaked at $10^{51.2}$ erg. We also study the frequency distributions of flare parameters, including energies, durations, peak fluxes, rise times, decay times and waiting times. Power-law distributions of energies, durations, peak fluxes, and waiting times are found in GRB X-ray flares and solar flares. These distributions could be well explained by a fractal-diffusive, self-organized criticality model. Some theoretical models basing on magnetic reconnection have been proposed to explain X-ray flares. Our result shows that the relativistic jets of GRBs may be Poynting-flux dominated.

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arXiv2016

On the inconsistency between cosmic stellar mass density and star formation rate up to $z\sim8$

In this paper, we test the discrepancy between the stellar mass density and instantaneous star formation rate in redshift range $0 6$), the derived star formation history is consistent with the observations. This is the first time to test the discrepancy between the observed stellar mass density and instantaneous star formation rate up to very high redshift $z\approx8$ using the Markov chain monte carlo method and a varying recycling factor. Several possible reasons for this discrepancy are discussed, such as underestimation of stellar mass density, initial mass function and cosmic metallicity evolution.

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arXiv2016

GRBs and fundamental physics

Gamma-ray bursts (GRBs) are short and intense flashes at the cosmological distances, which are the most luminous explosions in the Universe. The high luminosities of GRBs make them detectable out to the edge of the visible universe. So, they are unique tools to probe the properties of high-redshift universe: including the cosmic expansion and dark energy, star formation rate, the reionization epoch and the metal evolution of the Universe. First, they can be used to constrain the history of cosmic acceleration and the evolution of dark energy in a redshift range hardly achievable by other cosmological probes. Second, long GRBs are believed to be formed by collapse of massive stars. So they can be used to derive the high-redshift star formation rate, which can not be probed by current observations. Moreover, the use of GRBs as cosmological tools could unveil the reionization history and metal evolution of the Universe, the intergalactic medium (IGM) properties and the nature of first stars in the early universe. But beyond that, the GRB high-energy photons can be applied to constrain Lorentz invariance violation (LIV) and to test Einstein's Equivalence Principle (EEP). In this paper, we review the progress on the GRB cosmology and fundamental physics probed by GRBs.

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arXiv2015

Measuring dark energy with the $E_{\rm iso}-E_{\rm p}$ correlation of gamma-ray bursts using model-independent methods

In this paper, we use two model-independent methods to standardize long gamma-ray bursts (GRBs) using the $E_{\rm iso}-E_{\rm p}$ correlation, where $E_{\rm iso}$ is the isotropic-equivalent gamma-ray energy and $E_{\rm p}$ is the spectral peak energy. We update 42 long GRBs and try to make constraint on cosmological parameters. The full sample contains 151 long GRBs with redshifts from 0.0331 to 8.2. The first method is the simultaneous fitting method. The extrinsic scatter $σ_{\rm ext}$ is taken into account and assigned to the parameter $E_{\rm iso}$. The best-fitting values are $a=49.15\pm0.26$, $b=1.42\pm0.11$, $σ_{\rm ext}=0.34\pm0.03$ and $Ω_m=0.79$ in the flat $Λ$CDM model. The constraint on $Ω_m$ is $0.55<Ω_m<1$ at the 1$σ$ confidence level. If reduced $χ^2$ method is used, the best-fit results are $a=48.96\pm0.18$, $b=1.52\pm0.08$ and $Ω_m=0.50\pm0.12$. The second method is using type Ia supernovae (SNe Ia) to calibrate the $E_{\rm iso}-E_{\rm p}$ correlation. We calibrate 90 high-redshift GRBs in the redshift range from 1.44 to 8.1. The cosmological constraints from these 90 GRBs are $Ω_m=0.23^{+0.06}_{-0.04}$ for flat $Λ$CDM, and $Ω_m=0.18\pm0.11$ and $Ω_Λ=0.46\pm0.51$ for non-flat $Λ$CDM. For the combination of GRB and SNe Ia sample, we obtain $Ω_m=0.271\pm0.019$ and $h=0.701\pm0.002$ for the flat $Λ$CDM, and for the non-flat $Λ$CDM, the results are $Ω_m=0.225\pm0.044$, $Ω_Λ=0.640\pm0.082$ and $h=0.698\pm0.004$. These results from calibrated GRBs are consistent with that of SNe Ia. Meanwhile, the combined data can improve cosmological constraints significantly, comparing to SNe Ia alone. Our results show that the $E_{\rm iso}-E_{\rm p}$ correlation is promising to probe the high-redshift universe.

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