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

Universe ◽  
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.

scholarly journals 3D magnetized jet break-out from neutron-star binary merger ejecta: afterglow emission from the jet and the ejecta

2021 ◽  
Vol 502 (2) ◽  
pp. 1843-1855
Author(s):  
Antonios Nathanail ◽  
Ramandeep Gill ◽  
Oliver Porth ◽  
Christian M Fromm ◽  
Luciano Rezzolla
Keyword(s):  
Neutron Star ◽  
Thermal Emission ◽  
Opening Angle ◽  
Hollow Core ◽  
Binary Neutron Star ◽  
Vlbi Observations ◽  
Superluminal Motion ◽  
General Relativistic ◽  
Star Binary ◽  
Magnetohydrodynamic Simulations

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.

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

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.

scholarly journals An original interpretation of the wet edge of the surface temperature–albedo space to estimate crop evapotranspiration (SEB-1S), and its validation over an irrigated area in northwestern Mexico

2013 ◽  
Vol 17 (9) ◽  
pp. 3623-3637 ◽  
Author(s):  
O. Merlin
Keyword(s):  
Linear Regression ◽  
Surface Temperature ◽  
Thermal Emission ◽  
Meteorological Data ◽  
Remote Sensing Data ◽  
Available Energy ◽  
Irrigated Area ◽  
Green Vegetation ◽  
Northwestern Mexico ◽  
T Values

Abstract. The space defined by the pair surface temperature (T) and surface albedo (α), and the space defined by the pair T and fractional green vegetation cover (fvg) have been extensively used to estimate evaporative fraction (EF) from solar/thermal remote sensing data. In both space-based approaches, evapotranspiration (ET) is estimated as remotely sensed EF times the available energy. For a given data point in the T-α space or in the T-fvg space, EF is derived as the ratio of the distance separating the point from the line identified as the dry edge to the distance separating the dry edge and the line identified as the wet edge. The dry and wet edges are classically defined as the upper and lower limit of the spaces, respectively. When investigating side by side the T-α and the T-fvg spaces, one observes that the range covered by T values on the (classically determined) wet edge is different for both spaces. In addition, when extending the wet and dry lines of the T-α space, both lines cross at α ≈ 0.4 although the wet and dry edges of the T-fvg space never cross for 0 &amp;leq; fvg < 1. In this paper, a new ET (EF) model (SEB-1S) is derived by revisiting the classical physical interpretation of the T-α space to make its wet edge consistent with that of the T-fvg space. SEB-1S is tested over a 16 km by 10 km irrigated area in northwestern Mexico during the 2007–2008 agricultural season. The classical T-α space-based model is implemented as benchmark to evaluate the performance of SEB-1S. Input data are composed of ASTER (Advanced Spaceborne Thermal Emission and Reflection radiometer) thermal infrared, Formosat-2 shortwave, and station-based meteorological data. The fluxes simulated by SEB-1S and the classical T-α space-based model are compared on seven ASTER overpass dates with the in situ measurements collected at six locations within the study domain. The ET simulated by SEB-1S is significantly more accurate and robust than that predicted by the classical T-α space-based model. The correlation coefficient and slope of the linear regression between simulated and observed ET is improved from 0.82 to 0.93, and from 0.63 to 0.90, respectively. Moreover, constraining the wet edge using air temperature data improves the slope of the linear regression between simulated and observed ET.

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

2019 ◽  
Vol 627 ◽  
pp. A141 ◽  
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.

scholarly journals A model of an ion-proton radio pulsar polar cap

2019 ◽  
Author(s):  
P B Jones
Keyword(s):  
Neutron Star ◽  
Surface Temperature ◽  
Emission Mechanism ◽  
Polar Cap ◽  
Ion Proton ◽  
S Period ◽  
Basic Equations ◽  
Radio Transients ◽  
Star Surface ◽  
Rotating Radio Transients

Abstract A number of previous papers have developed an ion-proton theory of the pulsar polar cap. The basic equations summarizing this are given here with the results of sets of model step-to-step calculations of pulse-precursor profiles. The nature of step-to-step profile variations is described by calculated phase-resolved modulation indices. The conditions under which nulls are present in step sequences are analysed. The change of mean null length with neutron-star surface temperature shows a pathway ending in emission similar to the Rotating Radio Transients. The model accommodates exceptional pulsars, the millisecond pulsars (in principle), and the 8.5 s period PSR J2144-3933. These are considered separately and their emission mechanism discussed in some detail.

scholarly journals Neutron Star Cooling: Effects of Envelope Physics

1983 ◽  
Vol 101 ◽  
pp. 513-516
Author(s):  
Kenneth A. Van Riper
Keyword(s):  
Neutron Star ◽  
Surface Temperature ◽  
Supernova Remnants ◽  
Temperature Drop ◽  
Magnetic Star ◽  
Pion Condensate ◽  
Neutron Star Cooling ◽  
Cooling Mechanism ◽  
Cooling Effects ◽  
Star Surface

Neutron star cooling calculations are reported which employ improved physics in the calculation of the temperature drop through the atmosphere. The atmosphere microphysics is discussed briefly. The predicted neutron star surface temperatures, in the interesting interval 300 ≤ t (yr) ≤ 105, do not differ appreciably from the earlier results of Van Riper and Lamb (1981) for a non-magnetic star; for a magnetic star, the surface temperature is lower than in the previous work. Comparison with observational limits show that an exotic cooling mechanism such as neutrino emission from a pion-condensate or in the presence of percolating quarks, is not required, unless the existence of a neutron star in the Tycho or SN1006 supernova remnants is established.

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

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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