Thermonuclear X-ray bursts from 4U 1636 − 536  observed with AstroSat

ABSTRACT MAXI J1807+132 is a low-mass X-ray binary (LMXB) first detected in outburst in 2017. Observations during the 2017 outburst did not allow for an unambiguous identification of the nature of the compact object. MAXI J1807+132 that was detected in outburst again in 2019 and was monitored regularly with Neutron Star Interior Composition Explorer(NICER). In this paper, we report on 5 days of observations during which we detected three thermonuclear (Type-I) X-ray bursts, identifying the system as a neutron star LMXB. Time-resolved spectroscopy of the three Type-I bursts revealed typical characteristics expected for these phenomena. All three Type-I bursts show slow rises and long decays, indicative of mixed H/He fuel. We find no strong evidence that any of the Type-I bursts reached the Eddington Luminosity; however, under the assumption that the brightest X-ray burst underwent photospheric radius expansion, we estimate a <12.4 kpc upper limit for the distance. We searched for burst oscillations during the Type-I bursts from MAXI J1807+132 and found none (<10 per cent amplitude upper limit at 95 per cent confidence level). Finally, we found that the brightest Type-I burst shows a ∼1.6 s pause during the rise. This pause is similar to one recently found with NICER in a bright Type-I burst from the accreting millisecond X-ray pulsar SAX J1808.4–3658. The fact that Type-I bursts from both sources can show this type of pause suggests that the origin of the pauses is independent of the composition of the burning fuel, the peak luminosity of the Type-I bursts, or whether the NS is an X-ray pulsar.

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Constraining neutron star EoS from cooling stages of X-ray bursts

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312023411 ◽

2012 ◽

Vol 8 (S291) ◽

pp. 145-145

Author(s):

Juri Poutanen ◽

Valery Suleimanov

Keyword(s):

Neutron Star ◽

Thermal Emission ◽

Chemical Compositions ◽

Large Set ◽

X Ray ◽

Accretion Rates ◽

Cooling Phase ◽

Photospheric Radius ◽

Neutron Star Radius

AbstractThermal emission during X-ray bursts is a powerful tool to determine neutron star masses and radii, if the Eddington flux and the apparent radius in the cooling tail can be measured accurately, and distances to the sources are known. We propose here an improved method of determining the basic stellar parameters using the data from the cooling phase of long, photospheric radius expansion bursts covering a large range of luminosities. For this purpose, we computed a large set of atmosphere models for burst luminosities varying by two orders of magnitude and for various chemical compositions and surface gravities. We show that the variation of the inverse square root of the apparent blackbody radius with the flux, observed during the photospheric radius expansion bursts from a number of sources at low accretion rate is entirely consistent with the theoretical expectations of the color-correction factor evolution. However, for bursts happening at higher accretion rates the observed evolution is inconsistent with theory, implying that accretion strongly disturbs the neutron star atmosphere. These findings have profound implications for the recent claims on determination of the neutron star radii and masses from such bursts. Our method allows us to determine both the Eddington flux and the ratio of the stellar apparent radius to the distance much more reliably. For 4U 1724-307, we find a lower limit on the neutron star radius of 13 km, independently of the chemical composition. These results suggest that the matter inside neutron stars is characterized by a stiff equation of state.

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Binary and Other Recycled Pulsars

Symposium - International Astronomical Union ◽

10.1017/s0074180900122119 ◽

1992 ◽

Vol 151 ◽

pp. 115-122

Author(s):

Virginia Trimble

Keyword(s):

Mass Transfer ◽

Neutron Star ◽

Time History ◽

Close Binary ◽

Rapid Rotation ◽

X Ray ◽

Binary Pulsars ◽

History Of ◽

X Ray Binaries ◽

Weak Fields

Binary pulsars and others with weak fields and rapid rotation now number several dozen and appear to have been spun up by close binary mass transfer. Some are lineal descendents of X-ray binaries; others may result from accretion-induced collapse of binary white dwarfs or from captures, exchanges, and collisions in clusters. Seven accurate neutron star masses, 1.27-1.44 Mo, have been measured so far. Outstanding issues include the dominant formation process in various sites and the time history of the neutron stars' magnetic fields in and out of binaries.

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Discovery of thermonuclear (Type I) X-ray bursts in the X-ray binary Swift J1858.6–0814 observed with NICER and NuSTAR

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2749 ◽

2020 ◽

Vol 499 (1) ◽

pp. 793-803

Author(s):

D J K Buisson ◽

D Altamirano ◽

P Bult ◽

G C Mancuso ◽

T Güver ◽

...

Keyword(s):

Compact Object ◽

Type I ◽

X Rays ◽

Helium Atmosphere ◽

X Ray ◽

Systematic Effects ◽

Photospheric Radius ◽

Rms Amplitude ◽

Peak Luminosity ◽

Stable Burning

ABSTRACT Swift J1858.6–0814 is a recently discovered X-ray binary notable for extremely strong variability (by factors of >100 in soft X-rays) in its discovery state. We present the detection of five thermonuclear (Type I) X-ray bursts from Swift J1858.6–0814, implying that the compact object in the system is a neutron star (NS). Some of the bursts show photospheric radius expansion, so their peak flux can be used to estimate the distance to the system. The peak luminosity, and hence distance, can depend on several system parameters; for the most likely values, a high inclination and a helium atmosphere, $D=12.8_{-0.6}^{+0.8}$ kpc, although systematic effects allow a conservative range of 9–18 kpc. Before one burst, we detect a QPO at 9.6 ± 0.5 mHz with a fractional rms amplitude of 2.2 ± 0.2 per cent (0.5–10 keV), likely due to marginally stable burning of helium; similar oscillations may be present before the other bursts but the light curves are not long enough to allow their detection. We also search for burst oscillations but do not detect any, with an upper limit in the best case of 15 per cent fractional amplitude (over 1–8 keV). Finally, we discuss the implications of the NS accretor and this distance on other inferences which have been made about the system. In particular, we find that Swift J1858.6–0814 was observed at super-Eddington luminosities at least during bright flares during the variable stage of its outburst.

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Influence of the Neutron Star 1E 161348–5055 in RCW 103 on the Surrounding Medium

Publications of the Astronomical Society of Australia ◽

10.1071/as03053 ◽

2004 ◽

Vol 21 (1) ◽

pp. 82-88 ◽

Cited By ~ 25

Author(s):

E. M. Reynoso ◽

A. J. Green ◽

S. Johnston ◽

W. M. Goss ◽

G. M. Dubner ◽

...

Keyword(s):

Neutron Star ◽

Spatial Scales ◽

Surrounding Medium ◽

Neutral Hydrogen ◽

X Rays ◽

Distance Measurements ◽

X Ray ◽

A Value ◽

Very High

AbstractWe have carried out a study of the neutral hydrogen in the direction of the X-ray source 1E 161348–5055, a compact central object (CCO) located in the interior of the supernova remnant (SNR) RCW 103. The Hi 21 cm line observations were carried out using the Australia Telescope Compact Array, complemented with single dish data from the Parkes radio telescope to recover information at all spatial scales. We derive a distance to RCW 103 of 3.1 kpc, in agreement with previous distance measurements. We have also detected a small hole in the Hi emission which is positionally and kinematically coincident with the location of the CCO which confirms the association between the SNR and the CCO. This is the third case of a depression in Hi emission seemingly associated with CCOs in SNRs. The characteristic parameters of the holes such as their size, eccentricity and evacuated mass are similar in all three cases. We estimate the absorbing HI column density towards 1E 161348–5055 to be ∼6 × 1021 cm–2, a value compatible with a blackbody solution for the CCO X-ray emission. However, the implied temperature and luminosity are very high compared to most neutron stars. Moreover, the strong long-term variability in X-rays favours the hypothesis that 1E 161348–5055 is an accreting binary source rather than an isolated, cooling neutron star. An analysis of the continuum image obtained at 1.4 GHz from these observations shows no trace of a pulsar wind nebula around 1E 161348–5055, in spite of it being a young object.

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The amplitude of the kilohertz quasi-periodic oscillations in 4U 1636–53 in the frequency-energy space

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2463 ◽

2019 ◽

Vol 489 (4) ◽

pp. 4980-4991 ◽

Cited By ~ 3

Author(s):

Evandro M Ribeiro ◽

Mariano Méndez ◽

Marcio G B de Avellar ◽

Guobao Zhang ◽

Konstantinos Karpouzas

Keyword(s):

Neutron Star ◽

Local Maximum ◽

Radiative Properties ◽

Energy Bands ◽

Periodic Oscillations ◽

X Ray ◽

High Energies ◽

Low Mass ◽

First Time ◽

Rms Amplitude

ABSTRACT We present for the neutron-star low-mass X-ray binary 4U 1636–53, and for the first time for any source of kilohertz quasi-periodic oscillations (kHz QPOs), the two-dimensional behaviour of the fractional rms amplitude of the kHz QPOs in the parameter space defined by QPO frequency and photon energy. We find that the rms amplitude of the lower kHz QPO increases with energy up to $\sim \!\!12$ keV and then decreases at higher energies, while the rms amplitude of the upper kHz QPO either continues increasing or levels off at high energies. The rms amplitude of the lower kHz QPO increases and then decreases with frequency, peaking at $\sim \!\!760$ Hz, while the amplitude of the upper kHz QPO decreases with frequency, with a local maximum at around $\sim \!\!770$ Hz, and is consistent with becoming zero at the same QPO frequency, $\sim \!\!1400$ Hz, in all energy bands, thus constraining the neutron-star mass at $M_{NS} \le 1.6 \, \mathrm{M}_{\odot }$, under the assumption that this QPO reflects the Keplerian frequency at the inner edge of the accretion disc. We show that the slope of the rms energy spectrum is connected to the changing properties of the kHz QPOs in different energy bands as its frequencies change. Finally, we discuss a possible mechanism responsible for the radiative properties of the kHz QPOs and, based on a model in which the QPO arises from oscillations in a Comptonizing cloud of hot electrons, we show that the properties of the kHz QPOs can constrain the thermodynamic properties of the inner accretion flow.

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The Harmonic Component of the Millihertz Quasi-periodic Oscillations in 4U 1636–53

The Astrophysical Journal ◽

10.3847/1538-4357/ac2501 ◽

2021 ◽

Vol 922 (2) ◽

pp. 119

Author(s):

Zhenyan Fei ◽

Ming Lyu ◽

Mariano Méndez ◽

D. Altamirano ◽

Guobao Zhang ◽

...

Keyword(s):

Black Hole ◽

Neutron Star ◽

Fundamental Frequency ◽

Harmonic Component ◽

Periodic Oscillations ◽

X Ray ◽

Wide Range ◽

Low Mass ◽

First Time ◽

Rms Amplitude

Abstract We studied the harmonics of the millihertz quasi-periodic oscillations (mHz QPOs) in the neutron star low-mass X-ray binary 4U 1636–53 using the Rossi X-ray Timing Explorer observations. We detected the harmonics of the mHz QPOs in 73 data intervals, with most of them in the transitional spectra state. We found that the ratio between the rms amplitude of the harmonic and that of the fundamental remains constant in a wide range of the fundamental frequency. More importantly, we studied, for the first time, the rms amplitude of the harmonics versus energy in 4U 1636–53 in the 2–5 keV range. We found that the rms amplitude of both the harmonic and the fundamental shows a decreasing trend as the energy increases, which is different from the behaviors reported in QPOs in certain black hole systems. Furthermore, our results suggest that not all observations with mHz QPOs have the harmonic component, although the reason behind this is still unclear.

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Defect-Mediated Conductivity Enhancements in Na3-xPn1-xWxS4 (Pn = P, Sb) using Aliovalent Substitutions

10.26434/chemrxiv.9943961.v2 ◽

2019 ◽

Author(s):

Till Fuchs ◽

Sean Culver ◽

Paul Till ◽

Wolfgang Zeier

Keyword(s):

Ionic Conductivity ◽

Vacancy Concentration ◽

Sodium Ion ◽

High Ionic Conductivity ◽

Ionic Conductors ◽

X Ray Diffraction ◽

X Ray ◽

Solid State Batteries ◽

Ion Conducting ◽

Very High

The sodium-ion conducting family of Na3PnS4, with Pn = P, Sb, have gained interest for the use in solid-state batteries due to their high ionic conductivity. However, significant improvements to the conductivity have been hampered by the lack of aliovalent dopants that can introduce vacancies into the structure. Inspired by the need for vacancy introduction into Na3PnS4, the solid solutions with WS42- introduction are explored. The influence of the substitution with WS42- for PS43- and SbS43-, respectively, is monitored using a combination of X-ray diffraction, Raman and impedance spectroscopy. With increasing vacancy concentration improvements resulting in a very high ionic conductivity of 13 ± 3 mS·cm-1 for Na2.9P0.9W0.1S4 and 41 ± 8 mS·cm-1 for Na2.9Sb0.9W0.1S4 can be observed. This work acts as a stepping-stone towards further engineering of ionic conductors using vacancy-injection via aliovalent substituents.

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Defect-Mediated Conductivity Enhancements in Na3-xPn1-xWxS4 (Pn = P, Sb) using Aliovalent Substitutions

10.26434/chemrxiv.9943961.v1 ◽

2019 ◽

Author(s):

Till Fuchs ◽

Sean Culver ◽

Paul Till ◽

Wolfgang Zeier

Keyword(s):

Ionic Conductivity ◽

Vacancy Concentration ◽

Sodium Ion ◽

High Ionic Conductivity ◽

Ionic Conductors ◽

X Ray Diffraction ◽

X Ray ◽

Solid State Batteries ◽

Ion Conducting ◽

Very High

The sodium-ion conducting family of Na3PnS4, with Pn = P, Sb, have gained interest for the use in solid-state batteries due to their high ionic conductivity. However, significant improvements to the conductivity have been hampered by the lack of aliovalent dopants that can introduce vacancies into the structure. Inspired by the need for vacancy introduction into Na3PnS4, the solid solutions with WS42- introduction are explored. The influence of the substitution with WS42- for PS43- and SbS43-, respectively, is monitored using a combination of X-ray diffraction, Raman and impedance spectroscopy. With increasing vacancy concentration improvements resulting in a very high ionic conductivity of 13 ± 3 mS·cm-1 for Na2.9P0.9W0.1S4 and 41 ± 8 mS·cm-1 for Na2.9Sb0.9W0.1S4 can be observed. This work acts as a stepping-stone towards further engineering of ionic conductors using vacancy-injection via aliovalent substituents.

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