Wei-Hong Gao

Nanjing Normal University

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Yi-Zhong Fan

Purple Mountain Observatory

Da-Ming Wei

Chinese Academy of Sciences

Shao-Peng Tang

Purple Mountain Observatory

Jin-Liang Jiang

Kavli Institute for the Physics and Mathematics of the Universe

Kenji Toma

Tohoku University

K. Wiersema

University of Washington

R. Salvaterra

Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano

N. R. Tanvir

University of Leicester

M. G. Bernardini

Brera Astronomical Observatory

L. Kaper

University of Amsterdam

Cooperative Institutions

Centre National de la Recherche Scientifique

498

California Institute of Technology

336

Consejo Nacional de Investigaciones Científicas y Técnicas

285

Goddard Space Flight Center

221

Université Paris Cité

196

University of Alaska Anchorage

178

Clark Atlanta University

177

National Institute for Astrophysics

176

Universidad Nacional de La Plata

175

University of Buenos Aires

166

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The Masses of Isolated Neutron Stars Inferred from the Gravitational Redshift Measurements

The Astrophysical Journal (2020)

Shao-Peng Tang Jin-Liang Jiang Wei-Hong Gao Yi-Zhong Fan Da-Ming Wei

Abstract For some neutron stars (NSs) in the binary systems, the masses have been accurately measured. While for the isolated neutron stars (INSs), no mass measurement has been reported yet. The situation will change soon thanks to the successful performance of the Neutron Star Interior Composition Explorer ( NICER ), with which the radius and mass of the isolated PSR J0030+0451 can be simultaneously measured. For most INSs, no mass measurements are possible for NICER because of observational limitations. Benefiting from recent significant progress made on constraining the equation of state of NSs, in this work we propose a way to estimate the masses of the INSs with the measured gravitational redshifts. We apply our method to RX J1856.5-3754, RX J0720.4-3125, and RBS 1223, three members of “The Magnificent Seven” (M7), and estimate their masses to be , , and , respectively. These masses are consistent with that of binary NS systems, suggesting no evidence for experiencing significant accretion of these isolated objects.

Low Mass

10.3847/1538-4357/ab5959

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Citations (16)

The physical origin of optical flares following GRB 110205A and the nature of the outflow

Research in Astronomy and Astrophysics (2011)

Wei-Hong Gao

The optical emission of GRB 110205A is distinguished by two flares. In this work we examine two possible scenarios for the optical afterglow emission. In the first scenario, the first optical flare is the reverse shock emission of the main outflow and the second one is powered by the prolonged activity of central engine. We however find out that it is rather hard to interpret the late ($t>0.1$ day) afterglow data reasonably unless the GRB efficiency is very high ($\sim 0.95$). In the second scenario, the first optical flare is the low energy prompt emission and the second one is the reverse shock of the initial outflow. Within this scenario we can interpret the late afterglow emission self-consistently. The reverse shock region may be weakly magnetized and the decline of the second optical flare may be dominated by the high latitude emission, for which strong polarization evolution accompanying the quick decline is possible, as suggested by Fan et al. in 2008. Time-resolved polarimetry by RINGO2-like polarimeters will test our prediction directly.

Outflow

Flare

10.1088/1674-4527/11/11/007

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Citations (4)

The Bulk Properties of Isolated Neutron Stars Inferred from the Gravitational Redshift Measurements

The Astrophysical Journal (2022)

C. N. Luo Shao-Peng Tang Jin-Liang Jiang Wei-Hong Gao Da-Ming Wei

Abstract The measurements of the bulk properties of most isolated neutron stars (INSs) are challenging tasks. Tang et al. have developed a new method, based on the equation of state (EoS) of neutron star (NS) material constrained by the observational data, to infer the gravitational masses of a few INSs whose gravitational redshifts are available. However, in that work, the authors only considered the constraints on the EoS from nuclear experiments/theories and the gravitational wave data of GW170817; the possible phase transition has not been taken into account. In this work, we adopt three EoS models (including the one incorporates a first-order strong phase transition) that are constrained by the latest multimessenger NS data, including in particular the recent mass–radius measurements of two NSs by Neutron Star Interior Composition Explorer, to update the estimation of the gravitational masses of RBS 1223, RX J0720.4-3125, and RX J1856.5-3754. In comparison to our previous approach, the new constraints are tighter, and the gravitational masses are larger by about 0.1 M ⊙ . All the inferred gravitational masses are within the range of the NS masses measured in other ways. We have also calculated the radius, tidal-deformability, and moment of inertia of these sources. The inclusion of the first-order strong phase transition has little influence on modifying the results.

Moment of inertia

10.3847/1538-4357/ac6175

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Possible Signature of First-Order Phase Transition in the Multi-messenger Data of Neutron Stars

arXiv (Cornell University) (2020)

Shao-Peng Tang Jin-Liang Jiang Wei-Hong Gao Yi-Zhong Fan Da-Ming Wei

The equation of state (EoS) of the neutron star (NS) matter remains an enigma. In this work we perform the Bayesian parameter inference with the gravitational wave data (GW170817) and mass-radius observations of some NSs (PSR J0030+0451, PSR J0437-4715, and 4U 1702-429) using the phenomenologically constructed EoS models to search potential first-order phase transition. The whole data set, together with some additional/general conditions and the widely-adopted assumption that $M_{\rm TOV}$ lies between 2.04 and 2.3 solar mass, yield a signature of first-order phase transition at the density of $\sim2.7\rho_{\rm sat}$ with a density jump of $\sim 1.1\rho_{\rm sat}$, where $\rho_{\rm sat}$ is the nuclear saturation density. These parameters are in agreement with the current constraints and can be further tested with the new gravitational wave data as well as the upcoming {\it NICER} measurements of NSs in the near future.

Signature (topology)

Saturation (graph theory)

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Bulk properties of PSR J0030+0451 inferred with the compactness measurement of NICER

arXiv (Cornell University) (2024)

C. N. Luo Shao-Peng Tang Ming-Zhe Han Jin-Liang Jiang Wei-Hong Gao

In 2019, Neutron star Interior Composition ExploreR (NICER) mission released its findings on the mass and radius of the isolated neutron star (INS) PSR J0030+0451, revealing a mass of approximately 1.4 solar masses ($M_{\odot}$) and a radius near 13 kilometers. However, the recent re-analysis by the NICER collaboration \citep{vinciguerra2024updated} suggests that the available data primarily yields a precise inference of the compactness for this source while the resulting mass and radius are strongly model-dependent and diverse (the 68.3\% confidence counters just overlap slightly for the ST+PDT and PDT-U models). By integrating this compactness data with the equation of state (EoS) refined by our latest investigations, we have deduced the mass and radius for PSR J0030+0451, delivering estimates of $M=1.48^{+0.09}_{-0.10}~M_\odot$ and $R=12.39_{-0.70}^{+0.50}~{\rm km}$ for the compactness found in ST+PDT model, alongside $M=1.47^{+0.14}_{-0.20}~M_\odot$ and $R=12.37_{-0.70}^{+0.50}~{\rm km}$ for the compactness in PDT-U model. These two groups of results are well consistent with each other and the direct X-ray data inference within the ST+PDT model seems to be favored. Additionally, we have calculated the tidal deformability, moment of inertia, and gravitational binding energy for this NS. Furthermore, employing these refined EoS models, we have updated mass-radius estimates for three INSs with established gravitational redshifts.

10.48550/arxiv.2403.14105

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GRB 080916C AND GRB 090510: THE HIGH-ENERGY EMISSION AND THE AFTERGLOW

The Astrophysical Journal (2009)

Wei-Hong Gao J. Mao D. Xu Yi-Zhong Fan

We constrain the physical composition of the outflows of GRBs 080916C and 090510 with the prompt emission data and find that the former is likely magnetic while the latter may be baryonic. The X-ray and optical afterglow emission of both GRBs can be reasonably fitted using the standard external shock model but the density profiles of the circum-burst medium are different. We also propose a simple method to estimate the number of the seed photons suppose the GeV afterglow photons are due to the inverse Compton radiation of external forward shock electrons. The seed photons needed in the modeling are too many to be realistic for both events. The synchrotron radiation of the forward shock seems able to account for the GeV afterglow data.

10.1088/0004-637x/706/1/l33

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Citations (56)

Can the Bump Be Observed in the Early Afterglow of Gamma‐Ray Bursts with X‐Ray Line Emission Features?

The Astrophysical Journal (2004)

Wei-Hong Gao Da-Ming Wei

Extremely powerful emission lines are observed in the X-ray afterglow of several gamma-ray bursts (GRBs). The energy contained in the illuminatingcontinuum that is responsible for the line production exceeds 1051 ergs, much higher than that of the collimated GRBs, constraining the models that might explain the production of X-ray emission lines. In this paper, we argue that this energy can come from a continuous postburst outflow. Focusing on a central engine of highly magnetized millisecond pulsar or magnetar, we find that the afterglow can be affected by the illuminating continuum, and therefore a distinct achromatic bump can be observed in the early afterglow light curves. With the luminosity of the continuous outflow that produces the line emission, we define the upper limit of the time when the bump feature appears. We argue that the reason why the achromatic bumps have not been detected so far is that the bumps appear at too early a time to be observed.

Achromatic lens

Outflow

Line (geometry)

Collimated light

10.1086/381427

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Citations (3)

Superhumps in a Peculiar SU Ursae Majoris–Type Dwarf Nova, ER Ursae Majoris

The Astrophysical Journal (1999)

Wei-Hong Gao Zongyun Li Xiaoan Wu Zhousheng Zhang Yulan Li

We report the photometry of a peculiar SU Ursae Majoris-type dwarf nova, ER Ursae Majoris, for 10 nights during 1998 December and 1999 March, covering a complete rise to the supermaximum and a normal outburst cycle. Superhumps have been found during the rise to the superoutburst. A negative superhump appeared in the December 22 light curve, while the superhump on the next night became positive and had a large-amplitude waveform distinct from that of the previous night. In the normal outbursts we captured, superhumps with larger or smaller amplitudes seem to always exist, although it is not necessarily true for every normal outburst. These results show great resemblance to V1159 Ori. It is more likely that superhumps occasionally exist at essentially all phases of the eruption cycles of ER UMa stars, which should be considered in modeling.

Dwarf nova

Cataclysmic variable star

Accretion disc

10.1086/312398

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Citations (26)

A New Model for Iron Emission Lines and Rebursts in Gamma‐Ray Burst X‐Ray Afterglows

The Astrophysical Journal (2005)

Wei-Hong Gao Da-Ming Wei

Recently iron emission features have been observed in several X-ray afterglows of GRBs. It is found that the energy obtained from the illuminating continuum which produces the emission lines is much higher than that of the main burst.The observation of SN-GRB association indicates a fallback disk should be formed after the supernovae explosion. The disk is optically thick and advection-dominated and dense. We suggest that the delayed injection energy after the initial main burst, much higher than energy of the main burst, causes the re-burst appearance in GRB afterglow and illuminates the region of the disk surface with $τ\approx1$($τ$ is the optical depth for the Thomson scatter ) and produces the iron emission line whose luminosity can be up to $10^{45}$ erg$s^{-1}$. The duration of the iron line emission can be $10^{4}-10^{5}$ s. This model can explain the appearance of re-burst and emission lines in GRB afterglow and disappearance of the iron emission lines, and also can naturally solve the problem of higher energy of the illuminating continuum than that of the main burst. This scenario is different from the models put forward to explain the emission lines before, that can be tested by SWIFT satellite.

Line (geometry)

10.1086/431293

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Citations (4)

HESS J1427−608: AN UNUSUAL HARD, UNBROKENγ-RAY SPECTRUM IN A VERY WIDE ENERGY RANGE

The Astrophysical Journal (2017)

Xiaolei Guo Y. Xin Neng-Hui Liao Qiang Yuan Wei-Hong Gao

We report the detection of a GeV $\gamma$-ray source which is spatially overlapping and thus very likely associated with the unidentified very-high-energy (VHE) $\gamma$-ray source HESS J1427-608 with the Pass 8 data recorded by the Fermi Large Area Telescope. The photon spectrum of this source is best described by a power-law with an index of $1.85\pm0.17$ in the energy range of $3-500$ GeV, and the measured flux connects smoothly with that of HESS J1427-608 at a few hundred GeV. This source shows no significant extension and time variation. The broadband GeV-TeV emission over four decades of energies can be well fitted by a single power-law function with an index of 2.0, without obvious indication of spectral cutoff toward high energies. Such a result implies that HESS J1427-608 may be a PeV particle accelerator. We discuss possible nature of HESS J1427-608 according to the multi-wavelength spectral fittings. Given the relatively large errors, either a leptonic or a hadronic model can explain the multi-wavelength data from radio to VHE $\gamma$-rays. The inferred magnetic field strength is a few $\mu$G, which is smaller than typical values of supernova remnants (SNRs), and is consistent with some pulsar wind nebulae (PWNe). On the other hand, the flat $\gamma$-ray spectrum is slightly different from typical PWNe but similar to that of some known SNRs.

10.3847/1538-4357/835/1/42

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Citations (8)