Analysing neutron star in HESS J1731–347 from thermal emission and cooling theory

ABSTRACT We perform 3D general-relativistic magnetohydrodynamic simulations to model the jet break-out from the ejecta expected to be produced in a binary neutron-star merger. The structure of the relativistic outflow from the 3D simulation confirms our previous results from 2D simulations, namely, that a relativistic magnetized outflow breaking out from the merger ejecta exhibits a hollow core of θcore ≈ 4°, an opening angle of θjet ≳ 10°, and is accompanied by a wind of ejected matter that will contribute to the kilonova emission. We also compute the non-thermal afterglow emission of the relativistic outflow and fit it to the panchromatic afterglow from GRB170817A, together with the superluminal motion reported from VLBI observations. In this way, we deduce an observer angle of $\theta _{\rm obs}= 35.7^{\circ \, \, +1.8}_{\phantom{\circ \, \, }-2.2}$. We further compute the afterglow emission from the ejected matter and constrain the parameter space for a scenario in which the matter responsible for the thermal kilonova emission will also lead to a non-thermal emission yet to be observed.

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UV and X-ray observations of the neutron star LMXB EXO 0748–676 in its quiescent state

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3734 ◽

2020 ◽

Vol 501 (1) ◽

pp. 1453-1462

Author(s):

A S Parikh ◽

N Degenaar ◽

J V Hernández Santisteban ◽

R Wijnands ◽

I Psaradaki ◽

...

Keyword(s):

Neutron Star ◽

Thermal Emission ◽

Hubble Space Telescope ◽

Dense Matter ◽

Continuum Emission ◽

Quiescent State ◽

X Ray ◽

Low Level ◽

Low Mass ◽

Different Origins

ABSTRACT The accretion behaviour in low-mass X-ray binaries (LMXBs) at low luminosities, especially at <1034 erg s−1, is not well known. This is an important regime to study to obtain a complete understanding of the accretion process in LMXBs, and to determine if systems that host neutron stars with accretion-heated crusts can be used probe the physics of dense matter (which requires their quiescent thermal emission to be uncontaminated by residual accretion). Here, we examine ultraviolet (UV) and X-ray data obtained when EXO 0748–676, a crust-cooling source, was in quiescence. Our Hubble Space Telescope spectroscopy observations do not detect the far-UV continuum emission, but do reveal one strong emission line, C iv. The line is relatively broad (≳3500 km s−1), which could indicate that it results from an outflow such as a pulsar wind. By studying several epochs of X-ray and near-UV data obtained with XMM–Newton, we find no clear indication that the emission in the two wavebands is connected. Moreover, the luminosity ratio of LX/LUV ≳ 100 is much higher than that observed from neutron star LMXBs that exhibit low-level accretion in quiescence. Taken together, this suggests that the UV and X-ray emission of EXO 0748–676 may have different origins, and that thermal emission from crust-cooling of the neutron star, rather than ongoing low-level accretion, may be dominating the observed quiescent X-ray flux evolution of this LMXB.

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Thermal emission areas of heated neutron star polar caps

Isolated Neutron Stars: From the Surface to the Interior ◽

10.1007/978-1-4020-5998-8_52 ◽

2007 ◽

pp. 419-422

Author(s):

M. Ruderman ◽

A. M. Beloborodov

Keyword(s):

Neutron Star ◽

Thermal Emission ◽

Polar Caps

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Thermal X-ray emission identified from the millisecond pulsar PSR J1909–3744

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732040 ◽

2019 ◽

Vol 627 ◽

pp. A141 ◽

Cited By ~ 2

Author(s):

N. A. Webb ◽

D. Leahy ◽

S. Guillot ◽

N. Baillot d’Etivaux ◽

D. Barret ◽

...

Keyword(s):

Neutron Star ◽

Equation Of State ◽

Thermal Emission ◽

Black Body ◽

Millisecond Pulsar ◽

Distance Measurements ◽

Millisecond Pulsars ◽

X Ray ◽

Link Type

Context. Pulsating thermal X-ray emission from millisecond pulsars can be used to obtain constraints on the neutron star equation of state, but to date only five such sources have been identified. Of these five millisecond pulsars, only two have well-constrained neutron star masses, which improve the determination of the radius via modelling of the X-ray waveform. Aims. We aim to find other millisecond pulsars that already have well-constrained mass and distance measurements that show pulsed thermal X-ray emission in order to obtain tight constraints on the neutron star equation of state. Methods. The millisecond pulsar PSR J1909–3744 has an accurately determined mass, M = 1.54 ± 0.03 M⊙ (1σ error) and distance, D = 1.07 ± 0.04 kpc. We analysed XMM-Newton data of this 2.95 ms pulsar to identify the nature of the X-ray emission. Results. We show that the X-ray emission from PSR J1909–3744 appears to be dominated by thermal emission from the polar cap. Only a single component model is required to fit the data. The black-body temperature of this emission is $ {kT}=0.26^{0.03}_{0.02} $ keV and we find a 0.2–10 keV un-absorbed flux of 1.1 × 10−14 erg cm−2 s−1 or an un-absorbed luminosity of 1.5 × 1030 erg s−1. Conclusion. Thanks to the previously determined mass and distance constraints of the neutron star PSR J1909–3744, and its predominantly thermal emission, deep observations of this object with future X-ray facilities should provide useful constraints on the neutron star equation of state.

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Chandra Study of the Central Object Associated with the Supernova Remnant MSH 11–62

Symposium - International Astronomical Union ◽

10.1017/s0074180900180970 ◽

2004 ◽

Vol 218 ◽

pp. 203-206

Author(s):

Ilana Harrus ◽

Joseph P. Bernstein ◽

Patrick O. Slane ◽

Bryan Gaensler ◽

John P. Hughes ◽

...

Keyword(s):

Neutron Star ◽

Radio Emission ◽

Supernova Remnant ◽

Loss Rate ◽

Thermal Emission ◽

Compact Object ◽

Small Region ◽

Compact Source ◽

Synchrotron Nebula ◽

Compact Array

We present results from our analysis of Chandra data on the supernova remnant MSH 11–62 (also known as G291.0−0.1). Our previous ASCA analysis showed that MSH 11–62 is most likely a composite remnant whose strong non-thermal emission is powered by a compact object, most probably a pulsar. The present analysis confirms in a spectacular fashion the earlier detection of a compact source. The Chandra data reveal a small region with a hard non-thermal spectrum located at the tip of the central radio emission seen in data taken at the Australia Telescope Compact Array (ATCA). This source is likely the young rapidly rotating neutron star powering the synchrotron nebula in MSH 11–62. Compared to other young rotation-powered pulsars the Chandra specrum of MSH 11–62 implies an energy loss rate of Ė ∼ 5 × 1036 ergs s−1.

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Variability in the Thermal Emission from Accreting Neutron Star Transients

The Astrophysical Journal ◽

10.1086/341066 ◽

2002 ◽

Vol 574 (2) ◽

pp. 920-929 ◽

Cited By ~ 96

Author(s):

Edward F. Brown ◽

Lars Bildsten ◽

Philip Chang

Keyword(s):

Neutron Star ◽

Thermal Emission

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Charge Densities above Pulsar Polar Caps

International Astronomical Union Colloquium ◽

10.1017/s0252921100060310 ◽

2000 ◽

Vol 177 ◽

pp. 463-464

Author(s):

A. Jessner ◽

H. Lesch ◽

Th. Kunzl

Keyword(s):

Neutron Star ◽

Electric Field ◽

Work Function ◽

Potential Barrier ◽

Electric Fields ◽

Surface Potential ◽

Thermal Emission ◽

Equilibrium Density ◽

Charge Densities ◽

Polar Caps

A simplified model provided the framework for our investigation into the distribution of energy and charge densities above the polar caps of a rotating neutron star. We assumed a neutron star withm= 1.4M⊙,r= 10km, dipolar field |B0| = 1012G,B||Ω and Ω = 2Π · (0.5s)−1. The effects of general relativity were disregarded. The induced accelerating electric fieldE||reachesE0= 2.5 · 1013V m−1at the surface near the magnetic poles. The current density along the field lines has an upper limitnGJ, when the electric field of the charged particle flow cancels the induced electric field: At the polesnGJ(r=rns,θ= 0) = 1.4 · 1017m−3.The work function(surface potential barrier)EWis approximated by the Fermi energyEFof magnetised matter. Following Abrahams and Shapiro (1992) one needs to revise the surface density from the canonical 1.4 · 108kg m−3down toρFe = 2.9 · 107kg m−3. Withwe obtain a value ofEF=Ew= 417eV. There are two relevant particle emission processes:Field (cold cathode) emissionby quantum-mechanical tunneling of charges through the surface potentialandthermal emissionwhich is a purely classical process. In strong electric fields it is enhanced by the lowering of the potential barrier due to the Schottky effect. The combined Dushman-Schottky equationwithtells us, thatat temperatures> 2 · 105K the the Goldreich-Julian current can be supplied thermal emission alone. The surface temperature however has a lower limit in the order of 105K due to the rotational braking. Therefore, in most cases a sufficient supply of charges for the Goldreich-Julian current is available and the electrical field accelerating the particles will be quenched as a result of their abundance. Otherwise a residual equilibrium electric field Eeqremains with:and hence the equilibrium density is:n=nfieid(Eeq,EW) +nDS(Eeq,EW,T) For a temperature just below the onset of thermal emission (T= 1.85 · 105K) the charge density is found to vary almost linearly with the work functionEWfor values ofEWbetween 0.3 and 2 keV. At the chosen value forEWof 417 eVthe residual electric field amounts to only 8.5% of the vacuum value. Even in the residual electric field the particles are rapidly accelerated to relativistic energies balanced by inverse Compton and curvature radiation losses.

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Early neutron star evolution in high-mass X-ray binaries

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa675 ◽

2020 ◽

Vol 494 (1) ◽

pp. 44-49 ◽

Cited By ~ 2

Author(s):

Wynn C G Ho ◽

M J P Wijngaarden ◽

Nils Andersson ◽

Thomas M Tauris ◽

F Haberl

Keyword(s):

Magnetic Field ◽

Neutron Star ◽

Thermal Emission ◽

Equilibrium Phase ◽

High Mass ◽

X Ray ◽

Spin Period ◽

Long Duration ◽

X Ray Binaries ◽

The Magnetic Field

ABSTRACT The application of standard accretion theory to observations of X-ray binaries provides valuable insights into neutron star (NS) properties, such as their spin period and magnetic field. However, most studies concentrate on relatively old systems, where the NS is in its late propeller, accretor, or nearly spin equilibrium phase. Here, we use an analytic model from standard accretion theory to illustrate the evolution of high-mass X-ray binaries (HMXBs) early in their life. We show that a young NS is unlikely to be an accretor because of the long duration of ejector and propeller phases. We apply the model to the recently discovered ∼4000 yr old HMXB XMMU J051342.6−672412 and find that the system’s NS, with a tentative spin period of 4.4 s, cannot be in the accretor phase and has a magnetic field B > a few × 1013 G, which is comparable to the magnetic field of many older HMXBs and is much higher than the spin equilibrium inferred value of a few × 1011 G. The observed X-ray luminosity could be the result of thermal emission from a young cooling magnetic NS or a small amount of accretion that can occur in the propeller phase.

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Middle aged γ-ray pulsar J1957+5033 in X-rays: pulsations, thermal emission and nebula

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3991 ◽

2020 ◽

Author(s):

D A Zyuzin ◽

A V Karpova ◽

Y A Shibanov ◽

A Y Potekhin ◽

V F Suleimanov

Keyword(s):

Neutron Star ◽

Neutron Stars ◽

Power Law ◽

Thermal Emission ◽

Single Pulse ◽

X Rays ◽

Middle Aged ◽

X Ray ◽

Photon Index ◽

Γ Ray

Abstract We analyze new XMM-Newton and archival Chandra observations of the middle-aged γ-ray radio-quiet pulsar J1957+5033. We detect, for the first time, X-ray pulsations with the pulsar spin period of the point-like source coinciding by position with the pulsar. This confirms the pulsar nature of the source. In the 0.15–0.5 keV band, there is a single pulse per period and the pulsed fraction is ≈18 ± 6 per cent. In this band, the pulsar spectrum is dominated by a thermal emission component that likely comes from the entire surface of the neutron star, while at higher energies (≳ 0.7 keV) it is described by a power law with the photon index Γ ≈ 1.6. We construct new hydrogen atmosphere models for neutron stars with dipole magnetic fields and non-uniform surface temperature distributions with relatively low effective temperatures. We use them in the spectral analysis and derive the pulsar average effective temperature of ≈(2 − 3) × 105 K. This makes J1957+5033 the coldest among all known thermally emitting neutron stars with ages below 1 Myr. Using the interstellar extinction–distance relation, we constrain the distance to the pulsar in the range of 0.1–1 kpc. We compare the obtained X-ray thermal luminosity with those for other neutron stars and various neutron star cooling models and set some constraints on latter. We observe a faint trail-like feature, elongated ∼8 arcmin from J1957+5033. Its spectrum can be described by a power law with a photon index Γ = 1.9 ± 0.5 suggesting that it is likely a pulsar wind nebula powered by J1957+5033.

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A Simple Model of Radiation from a Magnetized Neutron Star: Accreted Matter and Polar Hotspots

Universe ◽

10.3390/universe7110395 ◽

2021 ◽

Vol 7 (11) ◽

pp. 395

Author(s):

Dmitry Yakovlev

Keyword(s):

Neutron Star ◽

Surface Temperature ◽

Thermal Emission ◽

Surface Element ◽

Local Surface ◽

Effective Surface ◽

Insulating Layer ◽

Radiation Spectra ◽

Dipole Magnetic Field ◽

Magnetic Poles

A simple and well known model for thermal radiation spectra from a magnetized neutron star is further studied. The model assumes that the star is internally isothermal and possesses a dipole magnetic field (B≲1014 G) in the outer heat-insulating layer. The heat transport through this layer makes the surface temperature distribution anisotropic; any local surface element is assumed to emit a blackbody (BB) radiation with a local effective temperature. It is shown that this thermal emission is nearly independent of the chemical composition of insulating envelope (at the same taken averaged effective surface temperature). Adding a slight extra heating of magnetic poles allows one to be qualitatively consistent with observations of some isolated neutron stars.

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