scholarly journals QUIESCENT THERMAL EMISSION OF NEUTRON STARS IN LMXBs

2010 ◽  
Vol 19 (06) ◽  
pp. 805-810
Author(s):  
ANABELA R. TURLIONE ◽  
JOSE A. PONS ◽  
DEBORAH N. AGUILERA
Keyword(s):  
Thermal Conductivity ◽  
Thermal Emission ◽  
Accretion Rate ◽  
Thermal Relaxation ◽  
Dense Matter ◽  
Light Curves ◽  
Model Parameters ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

Recent monitoring of the quiescent thermal emission from NSs in low mass X–ray binaries (LMXBs) after active periods (bursts) opened a new view to the physics of dense matter. Theoretical modeling of the thermal relaxation of the crust may be used to establish constraints on the thermal conductivity of matter, depending on the accretion rate. We present here cooling curves obtained from numerical simulations that fit the light curves for two sources (KS 1731-260, MXB 1659-29). We estimate the model parameters (accretion rate, thermal conductivity) that match the data and compare our results with previous constraints of neutron star crust properties in LMXBs.

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 X-Ray Burst Sources - A Simple Two Zone Model

1980 ◽  
Vol 58 ◽  
pp. 585-590 ◽  
Author(s):  
J. Robert Buchler ◽  
Manuel Barranco ◽  
Mario Livio
Keyword(s):  
Neutron Stars ◽  
Limit Cycle ◽  
Accretion Rate ◽  
Thermal Relaxation ◽  
Model Parameters ◽  
Zone Model ◽  
Helium Burning ◽  
Hydrogen Burning ◽  
X Ray ◽  
Reasonable Model

AbstractWith the help of a very simple two zone model, we demonstrate the possibility of periodic thermal relaxation (limit cycle) oscillations in the helium burning envelope of accreting neutron stars. Physically reasonable model parameters can be chosen which yield agreement with the observed features of x-ray bursts and we suggest that this limit cycle is operative in neutron stars which have an accretion rate in a specific range. For hydrogen burning a similar cycle is possible, but it operates at such high temperatures that an unrealistically large accretion rate would be required.

scholarly journals Understanding X-ray irradiation in low-mass X-ray binaries directly from their light-curves

2018 ◽  
Vol 480 (1) ◽  
pp. 2-16 ◽  
Author(s):  
BE Tetarenko ◽  
G Dubus ◽  
J-P Lasota ◽  
CO Heinke ◽  
GR Sivakoff
Keyword(s):  
Light Curves ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

scholarly journals Non-Linear Resonances in Accretion Disks and QPOs

2004 ◽  
Vol 194 ◽  
pp. 128-129
Author(s):  
Włodek Kluźniak
Keyword(s):  
Black Holes ◽  
Neutron Stars ◽  
Accretion Disk ◽  
Accretion Disks ◽  
High Frequency ◽  
Light Curves ◽  
X Ray ◽  
Non Linear ◽  
Low Mass ◽  
X Ray Binaries

AbstractNon-linear oscillations in the accretion disk are favored as an explanation of high-frequency QPOs observed in the light curves of low-mass X-ray binaries containing neutron stars, black holes, or white dwarfs.

scholarly journals Quiescent thermal emission from neutron stars in low-mass X-ray binaries

2015 ◽  
Vol 577 ◽  
pp. A5 ◽  
Author(s):  
A. Turlione ◽  
D. N. Aguilera ◽  
J. A. Pons
Keyword(s):  
Neutron Stars ◽  
Thermal Emission ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

scholarly journals R-modes in neutron stars: Theory and observations

2015 ◽  
Vol 24 (09) ◽  
pp. 1541007 ◽  
Author(s):  
B. Haskell
Keyword(s):  
Neutron Stars ◽  
Light Curves ◽  
Mutual Friction ◽  
Mode Instability ◽  
Flux Tubes ◽  
X Ray ◽  
Physical Mechanisms ◽  
Low Mass ◽  
Superfluid Vortices ◽  
X Ray Binaries

In this paper, I will review the theory behind the gravitational wave (GW) driven r-mode instability in rapidly rotating neutron stars (NSs) and discuss which constraints can be derived from observations of spins and temperatures in low mass X-ray binaries (LMXBs). I will discuss how a standard, 'minimal' NS model is not consistent with the data, and discuss some of the additional physical mechanisms that could reconcile theory with observations. In particular, I will focus on additional forms of damping due to exotic cores and on strong mutual friction due to superfluid vortices cutting through superconducting flux tubes, and examine the repercussions these effects could have on the saturation amplitude of the mode. Finally I will also discuss the possibility that oscillations due to r-modes may have been recently observed in the X-ray light curves of two LMXBs.

scholarly journals Supergiant Fast X-ray Transients uncovered by the EXTraS project: flares reveal the development of magnetospheric instability in accreting neutron stars

2019 ◽  
Vol 487 (1) ◽  
pp. 420-434
Author(s):  
Lara Sidoli ◽  
Konstantin A Postnov ◽  
Andrea Belfiore ◽  
Martino Marelli ◽  
David Salvetti ◽  
...  
Keyword(s):  
Neutron Stars ◽  
Large Range ◽  
Accretion Rate ◽  
Light Curves ◽  
High Mass ◽  
Time Interval ◽  
X Ray ◽  
Rayleigh Taylor Instability ◽  
X Ray Binaries ◽  
Peak Luminosity

ABSTRACT The low luminosity, X-ray flaring activity, of the sub-class of high-mass X-ray binaries called Supergiant Fast X-ray Transients, has been investigated using XMM–Newton public observations, taking advantage of the products made publicly available by the EXTraS project. One of the goals of EXTraS was to extract from the XMM–Newton public archive information on the aperiodic variability of all sources observed in the soft X-ray range with EPIC (0.2–12 keV). Adopting a Bayesian block decomposition of the X-ray light curves of a sample of SFXTs, we picked out 144 X-ray flares, covering a large range of soft X-ray luminosities (1032–1036 erg s−1). We measured temporal quantities, like the rise time to and the decay time from the peak of the flares, their duration and the time interval between adjacent flares. We also estimated the peak luminosity, average accretion rate, and energy release in the flares. The observed soft X-ray properties of low-luminosity flaring activity from SFXTs is in qualitative agreement with what is expected by the application of the Rayleigh–Taylor instability model in accreting plasma near the neutron star magnetosphere. In the case of rapidly rotating neutron stars, sporadic accretion from temporary discs cannot be excluded.

scholarly journals Consistent accretion-induced heating of the neutron-star crust in MXB 1659−29 during two different outbursts

2019 ◽  
Vol 624 ◽  
pp. A84 ◽  
Author(s):  
A. S. Parikh ◽  
R. Wijnands ◽  
L. S. Ootes ◽  
D. Page ◽  
N. Degenaar ◽  
...  
Keyword(s):  
Neutron Star ◽  
Accretion Rate ◽  
Dense Matter ◽  
Effective Surface ◽  
X Ray ◽  
Heating Mechanism ◽  
Heating And Cooling ◽  
Neutron Star Mass ◽  
Low Mass ◽  
Using Data

Monitoring the cooling of neutron-star crusts heated during accretion outbursts allows us to infer the physics of the dense matter present in the crust. We examine the crust cooling evolution of the low-mass X-ray binary MXB 1659−29 up to ∼505 days after the end of its 2015 outburst (hereafter outburst II) and compare it with what we observed after its previous 1999 outburst (hereafter outburst I) using data obtained from the Swift, XMM-Newton, and Chandra observatories. The observed effective surface temperature of the neutron star in MXB 1659 − 29 dropped from ∼92 eV to ∼56 eV from ∼12 days to ∼505 days after the end of outburst II. The most recently performed observation after outburst II suggests that the crust is close to returning to thermal equilibrium with the core. We model the crust heating and cooling for both its outbursts collectively to understand the effect of parameters that may change for every outburst (e.g. the average accretion rate, the length of outburst, the envelope composition of the neutron star at the end of the outburst) and those which can be assumed to be the same during these two outbursts (e.g. the neutron star mass, its radius). Our modelling indicates that all parameters were consistent between the two outbursts with no need for any significant changes. In particular, the strength and the depth of the shallow heating mechanism at work (in the crust) were inferred to be consistent during both outbursts, contrary to what has been found when modelling the cooling curves after multiple outburst of another source, MAXI J0556−332. This difference in source behaviour is not understood. We discuss our results in the context of our current understanding of cooling of accretion-heated neutron-star crusts, and in particular with respect to the unexplained shallow heating mechanism.

scholarly journals New Constraints on the Nuclear Equation of State from the Thermal Emission of Neutron Stars in Quiescent Low-mass X-Ray Binaries

2019 ◽  
Vol 887 (1) ◽  
pp. 48 ◽  
Author(s):  
Nicolas Baillot d’Etivaux ◽  
Sebastien Guillot ◽  
Jérôme Margueron ◽  
Natalie Webb ◽  
Márcio Catelan ◽  
...  
Keyword(s):  
Equation Of State ◽  
Neutron Stars ◽  
Thermal Emission ◽  
X Ray ◽  
Nuclear Equation Of State ◽  
Low Mass ◽  
X Ray Binaries
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