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.

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

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.

scholarly journals A peculiar thermonuclear X-ray burst from the transiently accreting neutron star SAX J1810.8–2609

2012 ◽  
Vol 8 (S291) ◽  
pp. 141-144
Author(s):  
N. Degenaar ◽  
R. Wijnands
Keyword(s):  
Neutron Star ◽  
Early Stage ◽  
Type I ◽  
X Ray ◽  
Radiated Energy ◽  
Low Mass ◽  
Peak Luminosity

AbstractWe report on a thermonuclear (type-I) X-ray burst that was detected from the neutron star low-mass X-ray binary SAX J1810.8–2609 in 2007 with Swift. This event was longer (≃20 min) and more energetic (a radiated energy of Eb≃6.5×1039 erg) than other X-ray bursts observed from this source. A possible explanation for the peculiar properties is that the X-ray burst occurred during the early stage of the outburst when the neutron star was relatively cold, which allows for the accumulation of a thicker layer of fuel. We also report on a new accretion outburst of SAX J1810.8–2609 that was observed with MAXI and Swift in 2012. The outburst had a duration of ≃17 days and reached a 2–10 keV peak luminosity of ≃ 3 × 1037 (D/5.7 kpc)2 erg s−1. This is a factor >10 more luminous than the two previous outbursts observed from the source, and classifies it as a bright rather than a faint X-ray transient.

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 Machine Learning Approach For Classifying Low-mass X-ray Binaries Based On Their Compact Object Nature

2020 ◽  
Author(s):  
R Pattnaik ◽  
K Sharma ◽  
K Alabarta ◽  
D Altamirano ◽  
M Chakraborty ◽  
...  
Keyword(s):  
Machine Learning ◽  
Black Hole ◽  
Neutron Star ◽  
Binary Systems ◽  
Compact Object ◽  
X Ray ◽  
Average Accuracy ◽  
Machine Learning Approach ◽  
Low Mass ◽  
X Ray Binaries

Abstract Low Mass X-ray binaries (LMXBs) are binary systems where one of the components is either a black hole or a neutron star and the other is a less massive star. It is challenging to unambiguously determine whether a LMXB hosts a black hole or a neutron star. In the last few decades, multiple observational works have tried, with different levels of success, to address this problem. In this paper, we explore the use of machine learning to tackle this observational challenge. We train a random forest classifier to identify the type of compact object using the energy spectrum in the energy range 5-25 keV obtained from the Rossi X-ray Timing Explorer archive. We report an average accuracy of 87±13% in classifying the spectra of LMXB sources. We further use the trained model for predicting the classes for LMXB systems with unknown or ambiguous classification. With the ever-increasing volume of astronomical data in the X-ray domain from present and upcoming missions (e.g., SWIFT, XMM-Newton, XARM, ATHENA, NICER), such methods can be extremely useful for faster and robust classification of X-ray sources and can also be deployed as part of the data reduction pipeline.

scholarly journals Swift/XRT, Chandra, and XMM–Newton observations of IGR J17091–3624 as it returns into quiescence

2020 ◽  
Vol 497 (1) ◽  
pp. 1115-1126
Author(s):  
M Pereyra ◽  
D Altamirano ◽  
J M C Court ◽  
N Degenaar ◽  
R Wijnands ◽  
...  
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Time Scales ◽  
Strong Evidence ◽  
Spectral Properties ◽  
X Ray ◽  
Term Evolution ◽  
Wide Range ◽  
Low Mass

ABSTRACT IGR J17091–3624 is a low-mass X-ray binary (LMXB), which received wide attention from the community thanks to its similarities with the bright black hole system GRS 1915+105. Both systems exhibit a wide range of highly structured X-ray variability during outburst, with time-scales from few seconds to tens of minutes, which make them unique in the study of mass accretion in LMXBs. In this work, we present a general overview into the long-term evolution of IGR J17091–3624, using Swift/XRT observations from the onset of the 2011–2013 outburst in 2011 February till the end of the last bright outburst in 2016 November. We found four re-flares during the decay of the 2011 outburst, but no similar re-flares appear to be present in the latter one. We studied, in detail, the period with the lowest flux observed in the last 10 yr, just at the tail end of the 2011–2013 outburst, using Chandra and XMM-Newton observations. We observed changes in flux as high as a factor of 10 during this period of relative quiescence, without strong evidence of softening in the spectra. This result suggests that the source has not been observed at its true quiescence so far. By comparing the spectral properties at low luminosities of IGR J17091–3624 and those observed for a well-studied population of LMXBs, we concluded that IGR J17091–3624 is most likely to host a black hole as a compact companion rather than a neutron star.

Comparison of the X-Ray Sources CIR X-1. GX301-2 and 2S0535-668

1980 ◽  
Vol 4 (1) ◽  
pp. 108-111 ◽  
Author(s):  
M. L. Duldig ◽  
R. M. Thomas ◽  
R. F. Haynes
Keyword(s):  
Neutron Star ◽  
Binary System ◽  
Strong Evidence ◽  
Compact Object ◽  
Eccentric Orbit ◽  
X Ray

There is reasonably strong evidence to suggest that the periodic X-ray, radio and optical variable Cir X-1 is a highly eccentric orbit (e ~ 0.8), binary system comprising an OB supergiant primary and a compact object, probably a neutron star (Whelan et al. 1977; Haynes, Lerche and Murdin 1980).

scholarly journals Measuring the Masses of Compact Objects in Low-Mass X-Ray Binaries

2004 ◽  
Vol 194 ◽  
pp. 214-214
Author(s):  
Dawn M. Gelino
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Compact Object ◽  
Compact Objects ◽  
Orbital Inclination ◽  
X Ray ◽  
Secondary Star ◽  
Low Mass ◽  
The Masses ◽  
X Ray Binaries

Low-mass X-ray binaries (LMXBs) contain compact, black hole (BH) or neutron star (NS) primaries, and cool, low-mass secondary stars. We measure the orbital inclination of the system in quiescence by modeling infrared (IR) ellipsoidal variations from the secondary star in order to determine the compact object mass. I present our results for a few LMXBs, including the first BH that appears to conclusively fall in the 3-5 M⊙ range.

scholarly journals Optical Signatures of Reprocessing from Hercules X-l

1997 ◽  
Vol 163 ◽  
pp. 811-811
Author(s):  
M. D. Still ◽  
A. P. Reynolds ◽  
H. Quaintrell ◽  
P. Roche ◽  
D. Chakrabarty ◽  
...  
Keyword(s):  
Neutron Star ◽  
Large Scale ◽  
Rotational Velocity ◽  
Compact Object ◽  
Velocity Measurements ◽  
X Ray ◽  
A Value ◽  
Systemic Velocity ◽  
Mass Estimate ◽  
Low Mass

AbstractThe mechanism providing the 35-day period found in optical and X-ray light curves of the eclipsing low-mass X-ray binary Her X-l is considered to be the precession of a tilted and twisted accretion disc about the neutron star. We have obtained spectrophotometric observations of this system. The majority of line absorption and emission originates on or near the mass-losing primary, with distributions over the inner face of the star consistent with irradiation from the environs of the compact object. After suitable corrections for heating, the neutron star is found have a mass of 1.6±0.3M⊙, in contrast to the last radial velocity study which found a value less than 1.0 M⊙ . Rotational velocity measurements, while insufficiently precise to reject the older mass estimate, suggest that the rotational period of HZ Her differs from the synchronous rate by no more than 20%. Using a recently determined figure for the effective temperature of the unheated face, the distance to Her X-l is estimated at 6.7±0.4kpc, higher than prior estimates. The systemic velocity is found to be –69±6km s−1. In order to to determine the plausibility of the twisted disc model we reconstruct the expected shadow of the disc across the heated inner face of the donor star to compare with observation. Large scale emission structure is reproduced, but the model fails to synthesize finer observational details. HeII λ4686 Å emission is detected and found to be distributed closely about the neutron star, and is a likely tracer of the accretion flow.

scholarly journals Binary X-Ray Stars and Supernovae of Type I

1976 ◽  
Vol 73 ◽  
pp. 19-25
Author(s):  
H. Gursky
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
White Dwarf ◽  
Binary Systems ◽  
Close Binary ◽  
Type I ◽  
Mass Limit ◽  
X Ray ◽  
Close Binary Systems ◽  
Low Mass

Most of the strong galactic X-ray sources must be low mass, close binary systems, such as Her X-1 and Sco X-1. Two evolutionary scenarios are discussed, both involving type I supernovae that occur when mass-accreting white dwarfs are driven over their mass limit. In one, accepting the correctness of the idea that a neutron star or black hole is the seat of the X-ray emission, the SN occurs before the system is an X-ray source. Another possibility is that the white dwarf is the X-ray source, just prior to its collapse and the ensuing SN.

scholarly journals Rapidly Evolving Light Curves of Low Mass X-Ray Binaries

2004 ◽  
Vol 194 ◽  
pp. 211-211
Author(s):  
P. Muhli ◽  
P. J. Hakala ◽  
L. Hjalmarsdotter ◽  
D. C. Hannikainen ◽  
J. Schultz
Keyword(s):  
Neutron Star ◽  
Light Curve ◽  
Light Curves ◽  
Type I ◽  
X Ray ◽  
Short Period ◽  
First Results ◽  
Low Mass ◽  
Photometric Monitoring ◽  
X Ray Binaries

A few Galactic Low Mass X-Ray Binaries (LMXBs) have shown drastically evolving X-ray and/or optical orbital light curves. In two short-period LMXBs, MS 1603+2600 (= UW CrB, Porb = 111 min) and 4U 1916-053 (see e.g. Homer et al. 2001), the variations in the light curve morphology seem to be repeating in a periodic manner. We present first results of a photometric monitoring campaign of MS 1603+2600, showing evidence of a 5-day superorbital period in this yet unclassified source. The observations also unraveled optical flares, reminiscent of type I bursts, suggesting a neutron star primary.

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