scholarly journals Thermonuclear Burst Observations for Model Comparisons: A Reference Sample

2017 ◽  
Vol 34 ◽  
Author(s):  
Duncan K. Galloway ◽  
Adelle J. Goodwin ◽  
Laurens Keek
Keyword(s):  
Accretion Rate ◽  
Numerical Models ◽  
Reference Sample ◽  
Recurrence Time ◽  
Test Cases ◽  
Type I ◽  
Time Resolved ◽  
X Ray ◽  
Peak Flux ◽  
Flux Level

AbstractWe present observations of thermonuclear (type-I) X-ray bursts, selected for comparison with numerical models. We provide examples of four distinct cases of ignition: He-ignition in mixed H/He fuel (case 1); He-ignition in pure He fuel, following exhaustion of accreted H by steady burning (case 2); ignition in (almost) pure He accumulated from an evolved donor in an ultracompact system; and a superburst, thought to arise from ignition of carbon fuel produced as a by-product of H/He bursts. For regular bursts, we measured the recurrence time and calculated averaged burst profiles from RXTE observations. We also estimated the recurrence time for pairs of bursts, including those observed during a transient outburst, modelled using a numerical ignition code. For each example we list the burst properties including recurrence time, fluence, peak flux, the persistent flux level (and inferred accretion rate), and the ratio of persistent flux to fluence. In the accompanying material, we provide a bolometric lightcurve for each burst, determined from time-resolved spectral analysis. Along with the inferred or adopted parameters for each burst system, including distance, surface gravity, and redshift, these data are suggested as suitable test cases for ignition models.

scholarly journals The type I X-ray bursts of 4U 1735–44

2012 ◽  
Vol 8 (S290) ◽  
pp. 251-252
Author(s):  
Y. J. Lei ◽  
H. T. Zhang ◽  
Y. Q. Dong ◽  
H. L. Yuan
Keyword(s):  
Accretion Rate ◽  
Type I ◽  
X Ray ◽  
Mass Accretion Rate ◽  
Peak Flux ◽  
Low Mass

AbstractWith RXTE data ranging from 1997 August to 1998 May, we detected 8 type I X-ray bursts from the atoll source 4U 1735–44. The bursts are present at all the branches, and most occur at an inferred low mass accretion rate. We find no correlation between the peak flux of the bursts and the mass accretion rate. The results are different from that of 4U 1728-34, whose bursts' peak flux are anti-correlated with the mass accretion rate.

scholarly journals The efficiency of nuclear burning during thermonuclear (Type I) bursts as a function of accretion rate

2020 ◽  
Vol 499 (2) ◽  
pp. 2148-2156
Author(s):  
Y Cavecchi ◽  
D K Galloway ◽  
A J Goodwin ◽  
Z Johnston ◽  
A Heger
Keyword(s):  
Neutron Star ◽  
Binary Systems ◽  
Accretion Rate ◽  
Numerical Models ◽  
Type I ◽  
X Ray ◽  
Accretion Rates ◽  
Key Factor ◽  
Nuclear Burning ◽  
Stable Burning

ABSTRACT We measured the thermonuclear burning efficiency as a function of accretion rate for the Type I X-ray bursts of five low-mass X-ray binary systems. We chose sources with measured neutron star spins and a substantial population of bursts from a large observational sample. The general trend for the burst rate is qualitatively the same for all sources; the burst rate first increases with the accretion rate up to a maximum, above which the burst rate declines, despite the increasing accretion rate. At higher accretion rates, when the burst rate decreases, the α-value (the ratio of accretion energy and burst energy) increases by up to a factor of 10 above that in the rising burst rate regime. These observations are contrary to the predictions of 1D numerical models, but can be explained as the consequence of a zone of stable burning on the neutron star surface, which expands with increasing accretion rate. The stable burning also ‘pollutes’ the unstable burning layer with ashes, contributing to the change in burst properties measured in the falling burst rate regime. We find that the mass accretion rate at which the burst rate begins to decrease is anticorrelated with the spin of the neutron star. We conclude that the neutron star spin is a key factor, moderating the nuclear burning stability, via the local accretion rate and fuel composition over the star.

scholarly journals The study of multipeaked type-I X-ray bursts in the neutron star low-mass X-ray binary 4U 1636 − 536 with RXTE

2020 ◽  
Vol 501 (1) ◽  
pp. 168-178
Author(s):  
Chen Li ◽  
Guobao Zhang ◽  
Mariano Méndez ◽  
Jiancheng Wang ◽  
Ming Lyu
Keyword(s):  
Neutron Star ◽  
Flux Ratio ◽  
Light Curves ◽  
Type I ◽  
X Ray ◽  
Soft State ◽  
Peak Flux ◽  
Low Mass ◽  
Two Peaks ◽  
Second Peak

ABSTRACT We have found and analysed 16 multipeaked type-I bursts from the neutron-star low-mass X-ray binary 4U 1636 − 53 with the Rossi X-ray Timing Explorer (RXTE). One of the bursts is a rare quadruple-peaked burst that was not previously reported. All 16 bursts show a multipeaked structure not only in the X-ray light curves but also in the bolometric light curves. Most of the multipeaked bursts appear in observations during the transition from the hard to the soft state in the colour–colour diagram. We find an anticorrelation between the second peak flux and the separation time between two peaks. We also find that in the double-peaked bursts the peak-flux ratio and the temperature of the thermal component in the pre-burst spectra are correlated. This indicates that the double-peaked structure in the light curve of the bursts may be affected by enhanced accretion rate in the disc, or increased temperature of the neutron star.

scholarly journals A catalogue of intermediate-duration Type I X-ray bursts observed with the INTEGRAL satellite

2020 ◽  
Vol 494 (2) ◽  
pp. 2509-2522 ◽  
Author(s):  
K Alizai ◽  
J Chenevez ◽  
S Brandt ◽  
N Lund
Keyword(s):  
Accretion Rate ◽  
Type I ◽  
Emission Method ◽  
X Ray ◽  
Long Duration ◽  
Photospheric Radius

ABSTRACT We present a catalogue of long-duration bursts observed with the Joint European X-ray Monitor and IBIS/ISGRI instruments onboard the INTEGRAL satellite. The 14 bursts have e-folding times ranging from 55 s to ≈17 min, and are therefore classified as intermediate-duration bursts, caused by the ignition of an unusually thick helium layer. Though seven events have already been reported in literature, we have systematically reanalysed the whole sample. We find three new photospheric radius expansion bursts, which are not reported in the literature, allowing us to provide a new estimate of the distances to these sources. We apply the enhanced persistent emission method (also known as the fa method) on sources with detectable persistent emission prior to a burst, in order to follow the evolution of the accretion rate during the burst. Although we do not get significantly better fits, the evolution of the fa factor shows an indicative behaviour, which we discuss.

scholarly journals Mixed H/He bursts in SAX J1748.9–2021 during the spectral change of its 2015 outburst

2018 ◽  
Vol 620 ◽  
pp. A114 ◽  
Author(s):  
Z. Li ◽  
V. De Falco ◽  
M. Falanga ◽  
E. Bozzo ◽  
L. Kuiper ◽  
...  
Keyword(s):  
Plasma Temperature ◽  
Compact Object ◽  
Recurrence Time ◽  
Type I ◽  
Slab Geometry ◽  
X Ray ◽  
Soft State ◽  
Hard State ◽  
Best Fit ◽  
Spectral States

SAX J1748.9–2021 is a transiently accreting X-ray millisecond pulsar. It is also known as an X-ray burster source discovered by Beppo-SAX. We analyzed the persistent emission and type-I X-ray burst properties during its 2015 outburst. The source changed from hard to soft state within half day. We modeled the broadband spectra of the persistent emission in the (1–250) keV energy band for both spectral states using the quasi-simultaneous INTEGRAL and Swift data. The broadband spectra are well fitted by an absorbed thermal Componization model, COMPPS, in a slab geometry. The best-fits for the two states indicate significantly different plasma temperature of 18 and 5 keV and the Thomson optical depths of three and four, respectively. In total, 56 type-I X-ray bursts were observed during the 2015 outburst, of which 26 detected by INTEGRAL in the hard state, 25 by XMM-Newton in the soft state, and five by Swift in both states. As the object transited from the hard to the soft state, the recurrence time for X-ray bursts decreased from ≈2 to ≈1 h. The relation between the recurrence time, Δtrec, and the local mass accretion rate per unit area onto the compact object, ṁ, is fitted by a power-law model, and yielded as best fit at Δtrec ∼ ⟨ṁ⟩−1.02±0.03 using all X-ray bursts. In both cases, the observed recurrence times are consistent with the mixed hydrogen and helium bursts. We also discuss the effects of type-I X-ray bursts prior to the hard to soft transition.

scholarly journals Cooling of accretion disc coronae by Type I X-ray bursts

2020 ◽  
Vol 499 (3) ◽  
pp. 4479-4489
Author(s):  
J Speicher ◽  
D R Ballantyne ◽  
J Malzac
Keyword(s):  
Accretion Rate ◽  
Temperature Drop ◽  
Accretion Disc ◽  
Type I ◽  
X Ray ◽  
Geometrical Properties ◽  
Fundamental Properties ◽  
Cooling Effects ◽  
The Impact ◽  
Burst Emission

ABSTRACT Although accretion disc coronae appear to be common in many accreting systems, their fundamental properties remain insufficiently understood. Recent work suggests that Type I X-ray bursts from accreting neutron stars provide an opportunity to probe the characteristics of coronae. Several studies have observed hard X-ray shortages from the accretion disc during an X-ray burst implying strong coronal cooling by burst photons. Here, we use the plasma emission code eqpair to study the impact of X-ray bursts on coronae, and how the coronal and burst properties affect the coronal electron temperatures and emitted spectra. Assuming a constant accretion rate during the burst, our simulations show that soft photons can cool coronal electrons by a factor of ≳ 10 and cause a reduction of emission in the 30–50 keV band to $\lesssim 1{{\ \rm per\ cent}}$ of the pre-burst emission. This hard X-ray drop is intensified when the coronal optical depth and aspect ratio is increased. In contrast, depending on the properties of the burst and corona, the emission in the 8–24 keV band can either increase, by a factor of ≳ 20, or decrease, down to $\lesssim 1{{\ \rm per\ cent}}$ of the pre-burst emission. An increasing accretion rate during the X-ray burst reduces the coronal cooling effects and the electron temperature drop can be mitigated by $\gtrsim 60{{\ \rm per\ cent}}$. These results indicate that changes of the hard X-ray flux during an X-ray burst probe the geometrical properties of the corona.

scholarly journals Discovery of thermonuclear Type-I X-ray bursts from the X-ray binary MAXI J1807+132

2020 ◽  
Vol 501 (1) ◽  
pp. 261-268
Author(s):  
A C Albayati ◽  
D Altamirano ◽  
G K Jaisawal ◽  
P Bult ◽  
S Rapisarda ◽  
...  
Keyword(s):  
Neutron Star ◽  
Strong Evidence ◽  
Compact Object ◽  
Type I ◽  
Time Resolved ◽  
X Ray ◽  
Upper Limit ◽  
Low Mass ◽  
Photospheric Radius ◽  
Peak Luminosity

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.

A deficit of type I X-ray bursts from low-accretion-rate binaries: Data from the TTM/COMIS telescope onboard the Mir-Kvant observatory

2001 ◽  
Vol 27 (12) ◽  
pp. 781-789 ◽  
Author(s):  
A. N. Emelyanov ◽  
V. A. Aref’ev ◽  
E. M. Churazov ◽  
M. R. Gilfanov ◽  
R. A. Sunyaev
Keyword(s):  
Accretion Rate ◽  
Type I ◽  
X Ray

scholarly journals EVIDENCE FOR ACCRETION RATE CHANGE DURING TYPE I X-RAY BURSTS

2013 ◽  
Vol 772 (2) ◽  
pp. 94 ◽  
Author(s):  
Hauke Worpel ◽  
Duncan K. Galloway ◽  
Daniel J. Price
Keyword(s):  
Accretion Rate ◽  
Rate Change ◽  
Type I ◽  
X Ray

A Wide-Bandpass Multilayer Monochromator for Biological Small-Angle Scattering and Fiber Diffraction Studies

1998 ◽  
Vol 31 (5) ◽  
pp. 672-682 ◽  
Author(s):  
Hiro Tsuruta ◽  
Sean Brennan ◽  
Zofia U. Rek ◽  
Thomas C. Irving ◽  
W. H. Tompkins ◽  
...  
Keyword(s):  
Small Angle ◽  
Double Crystal ◽  
Time Resolved ◽  
X Ray ◽  
Double Crystal Monochromator ◽  
X Ray Scattering ◽  
Fiber Diffraction ◽  
Angle Scattering ◽  
Flux Level ◽  
Ray Scattering

Many biological applications of small-angle X-ray scattering, in particular time-resolved studies, are often limited by the flux incident on the sample due to the smaller scattering cross section of biological specimens. The wider-energy bandpass of a monochromator that consists of a pair of synthetic multilayer microstructures can, in principle, provide a flux two orders of magnitude higher than that of an Si(111) double-crystal monochromator. Two types of multilayers have been installed in the standard monochromator tank of beamline 4-2 at the Stanford Synchrotron Radiation Laboratory; the multilayer beam has been characterized for studies of small-angle X-ray scattering/diffraction from biological materials. Reflectivity and topography measurements indicate that the multilayers are quite adequate for these applications and a pair of Mo/B4C multilayers provided a 10–30 times increase in flux, compared with the flux level obtained with an Si(111) double-crystal monochromator. The increased flux level is very useful in time-resolved scattering studies as well as for recording weak scattering at higher angles. Having carried out many solution scattering and fiber diffraction experiments, we conclude that the use of multilayer does not result in significant broadening of diffraction peaks nor does it have appreciable effects on small-angle resolution. No significant increase in background is observed.

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