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Hao Tong

Bio: Hao Tong is an academic researcher from Guangzhou University. The author has contributed to research in topics: Magnetar & Pulsar. The author has an hindex of 21, co-authored 96 publications receiving 1136 citations. Previous affiliations of Hao Tong include Nanjing University & Chinese Academy of Sciences.


Papers
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Journal ArticleDOI
TL;DR: In this article, the authors explore the wind braking of magnetars considering recent observations challenging the traditional magnetar model, and show that a small reduction of the dipole magnetic field is possible only when the particle wind is very collimated at the star surface.
Abstract: We explore the wind braking of magnetars considering recent observations challenging the traditional magnetar model. There is evidence for strong multipole magnetic fields in active magnetars, but the dipole field inferred from spin-down measurements may be strongly biased by particle wind. Recent observations challenging the traditional model of magnetars may be explained naturally by the wind braking scenario: (1) the supernova energies of magnetars are of normal value; (2) the non-detection in Fermi observations of magnetars; (3) the problem posed by low magnetic field soft gamma-ray repeaters; (4) the relation between magnetars and high magnetic field pulsars; and (5) a decreasing period derivative during magnetar outbursts. Transient magnetars with L-x<-(E) over dot(rot) may still be magnetic dipole braking. This may explain why low luminosity magnetars are more likely to have radio emissions. A strong reduction of the dipole magnetic field is possible only when the particle wind is very collimated at the star surface. A small reduction of the dipole magnetic field may result from detailed considerations of magnetar wind luminosity. In the wind braking scenario, magnetars are neutron stars with a strong multipole field. For some sources, a strong dipole field may no longer be needed. A magnetism-powered pulsar wind nebula will be one of the consequences of wind braking. For a magnetism-powered pulsar wind nebula, we should see a correlation between the nebula luminosity and the magnetar luminosity. Under the wind braking scenario, a braking index smaller than three is expected. Future braking index measurement of a magnetar may tell us whether magnetars are wind braking or magnetic dipole braking.

83 citations

Journal ArticleDOI
TL;DR: In this article, the primal magnetic field of the collapsed core during a supernova explosion was shown to receive a massive boost to more than 90 times its original value by the induced Pauli paramagnetization of the highly degenerate relativistic electron gas in the interior of the neutron star.
Abstract: In this paper we present a new result, namely that the primal magnetic field of the collapsed core during a supernova explosion will, as a result of the conservation of magnetic flux, receive a massive boost to more than 90 times its original value by the Pauli paramagnetization of the highly degenerate relativistic electron gas just after the formation of the neutron star. Thus, the observed super-strong magnetic field of neutron stars may originate from the induced Pauli paramagnetization of the highly degenerate relativistic electron gas in the interior of the neutron star. We therefore have an apparently natural explanation for the surface magnetic field of a neutron star.

59 citations

Journal ArticleDOI
TL;DR: In this article, a pulsar wind model is updated by considering the effect of particle density and pulsar death, which can describe both the short-term and long-term rotational evolution of pulsars consistently.
Abstract: The pulsar wind model is updated by considering the effect of particle density and pulsar death. It can describe both the short-term and long-term rotational evolution of pulsars consistently. It is applied to model the rotational evolution of the Crab pulsar. The pulsar is spun down by a combination of magnetic dipole radiation and particle wind. The parameters of the Crab pulsar, including magnetic field, inclination angle, and particle density are calculated. The primary particle density in acceleration region is about 103 times the Goldreich-Julian charge density. The lower braking index between glitches is due to a larger outflowing particle density. This may be glitch induced magnetospheric activities in normal pulsars. Evolution of braking index and the Crab pulsar in P - (P) over dot diagram are calculated. The Crab pulsar will evolve from magnetic dipole radiation dominated case towards particle wind-dominated case. Considering the effect of pulsar 'death', the Crab pulsar (and other normal pulsars) will not evolve to the cluster of magnetars but downwards to the death valley. Different acceleration models are also considered. Applications to other sources are also discussed, including pulsars with braking index measured, and the magnetar population.

51 citations

Journal ArticleDOI
TL;DR: In this article, a starquake model of solid quark stars is proposed to understand the physical mechanism of the sudden spin-up of pulsars, which is a common phenomenon in pulsar observations.
Abstract: Glitch (sudden spin-up) is a common phenomenon in pulsar observations. However, the physical mechanism of glitch is still a matter of debate because it depends on the puzzle of pulsar's inner structure, i.e. the equation of state of dense matter. Some pulsars (e.g. Vela like) show large glitches (Delta nu/nu similar to 10(-6)) but release negligible energy, whereas the large glitches of AXPs/SGRs (anomalous X-ray pulsars/soft gamma repeaters) are usually (but not always) accompanied with detectable energy releases manifesting as X-ray bursts or outbursts. We try to understand this aspect of glitches in a starquake model of solid quark stars. There are two kinds of glitches in this scenario: bulk-invariable (type I) and bulk-variable (type II) ones. The total stellar volume changes (and then energy releases) significantly for the latter but not for the former. Therefore, glitches accompanied with X-ray bursts (e.g. that of AXP/SGRs) could originate from type II starquakes induced probably by accretion, while the others without evident energy release (e.g. that of Vela pulsar) would be the result of type I starquakes due to, simply, a change of stellar ellipticity.

51 citations

Journal ArticleDOI
TL;DR: In this paper, the authors discuss the properties of detected glitches in Crab pulsar and compare them with glitches in the Vela pulsar, concluding that the occurrence of glitches appears to be a random process as described by previous researches.
Abstract: From 2000 to 2010, monitoring of radio emission from the Crab pulsar at Xinjiang Observatory detected a total of nine glitches. The occurrence of glitches appears to be a random process as described by previous researches. A persistent change in pulse frequency and pulse frequency derivative after each glitch was found. There is no obvious correlation between glitch sizes and the time since last glitch. For these glitches Delta nu (p) and span two orders of magnitude. The pulsar suffered the largest frequency jump ever seen on MJD 53067.1. The size of the glitch is similar to 6.8x10(-6) Hz, similar to 3.5 times that of the glitch occurred in 1989 glitch, with a very large permanent changes in frequency and pulse frequency derivative and followed by a decay with time constant similar to 21 days. The braking index presents significant changes. We attribute this variation to a varying particle wind strength which may be caused by glitch activities. We discuss the properties of detected glitches in Crab pulsar and compare them with glitches in the Vela pulsar.

40 citations


Cited by
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01 Dec 1998
TL;DR: The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) as mentioned in this paper is dedicated to the fine spectroscopy (2.5 − 1.5 ) and fine imaging (angular resolution: 12 arcmin FWHM) of celestial gamma-ray sources in the energy range 15 − 10 − MeV with concurrent source monitoring in the X-ray ($3 − 35 ) and optical (V -band, 550 −nm) energy ranges.
Abstract: The ESA observatory INTEGRAL (International Gamma-Ray Astrophysics Laboratory) is dedicated to the fine spectroscopy (2.5 keV FWHM @ 1 MeV) and fine imaging (angular resolution: 12 arcmin FWHM) of celestial gamma-ray sources in the energy range 15 keV to 10 MeV with concurrent source monitoring in the X-ray ($3{-}35$ keV) and optical ( V -band, 550 nm) energy ranges. INTEGRAL carries two main gamma-ray instruments, the spectrometer SPI (Vedrenne et al. [CITE]) – optimized for the high-resolution gamma-ray line spectroscopy (20 keV–8 MeV), and the imager IBIS (Ubertini et al. [CITE]) – optimized for high-angular resolution imaging (15 keV–10 MeV). Two monitors, JEM-X (Lund et al. [CITE]) in the ($3{-}35$) keV X-ray band, and OMC (Mas-Hesse et al. [CITE]) in optical Johnson V -band complement the payload. The ground segment includes the Mission Operations Centre at ESOC, ESA and NASA ground stations, the Science Operations Centre at ESTEC and the Science Data Centre near Geneva. INTEGRAL was launched on 17 October 2002. The observing programme is well underway and sky exposure (until June 2003) reaches ~1800 ks in the Galactic plane. The prospects are excellent for the scientific community to observe the high energy sky using state-of-the-art gamma-ray imaging and spectroscopy. This paper presents a high-level overview of INTEGRAL.

726 citations

Journal ArticleDOI
TL;DR: In this article, the authors present the results of 2D simulations of the fully-coupled evolution of temperature and magnetic field in neutron stars, including the state-of-the-art kinetic coefficients and, for the first time, the important effect of the Hall term.
Abstract: Observations of magnetars and some of the high magnetic field pulsars have shown that their thermal luminosity is systematically higher than that of classical radiopulsars, thus confirming the idea that magnetic fields are involved in their X-ray emission. Here we present the results of 2D simulations of the fully-coupled evolution of temperature and magnetic field in neutron stars, including the state-of-the-art kinetic coefficients and, for the first time, the important effect of the Hall term. After gathering and thoroughly re-analysing in a consistent way all the best available data on isolated, thermally emitting neutron stars, we compare our theoretical models to a data sample of 40 sources. We find that our evolutionary models can explain the phenomenological diversity of magnetars, high-B radio-pulsars, and isolated nearby neutron stars by only varying their initial magnetic field, mass and envelope composition. Nearly all sources appear to follow the expectations of the standard theoretical models. Finally, we discuss the expected outburst rates and the evolutionary links between different classes. Our results constitute a major step towards the grand unification of the isolated neutron star zoo.

434 citations

Book
01 Jan 2014
TL;DR: This book discusses the evolution of Modern Fishes, the Dinosaur Integument, Mammal-like Reptiles, and Reptiles Return to the Sea.
Abstract: Introduction.- The First Vertebrates, Jawless Fishes, the Agnathans.- The Earliest Jawed Vertebrates, the Gnathostomes.- Evolution of Modern Fishes: Critical Biological Innovations.- Tetrapods and the Invasion of Land.- Crucial Vertebrate Innovations.- The Dinosaur Integument.- Mammal-like Reptiles.- Reptiles Return to the Sea.

354 citations

Journal ArticleDOI
TL;DR: In this article, coherent pulsations from the ultraluminous X-ray source (ULX) NGC 7793 P13 were detected using XMM-Newton and NuSTAR data.
Abstract: We report the detection of coherent pulsations from the ultraluminous X-ray source (ULX) NGC 7793 P13. The ≈0.42 s nearly sinusoidal pulsations were initially discovered in broadband X-ray observations using XMM-Newton and NuSTAR taken in 2016. We subsequently also found pulsations in archival XMM-Newton data taken in 2013 and 2014. The significant (≫5σ) detection of coherent pulsations demonstrates that the compact object in P13 is a neutron star, and given the observed peak luminosity of ≈10^(40) erg s^(-1) (assuming isotropy), it is well above the Eddington limit for a 1.4 M⊙ accretor. This makes P13 the second ULX known to be powered by an accreting neutron star. The pulse period varies between epochs, with a slow but persistent spin-up over the 2013–2016 period. This spin-up indicates a magnetic field of B ≈ 1.5 × 10^(12) G, typical of many Galactic accreting pulsars. The most likely explanation for the extreme luminosity is a high degree of beaming; however, this is difficult to reconcile with the sinusoidal pulse profile.

296 citations