scholarly journals On the ultra-compact nature of the neutron star system 1RXS J170854.4−321857: insights from X-ray spectroscopy

2019 ◽  
Vol 488 (4) ◽  
pp. 5014-5019 ◽  
Author(s):  
M Armas Padilla ◽  
E López-Navas
Keyword(s):  
Neutron Star ◽  
Spectral Study ◽  
Binary Systems ◽  
Absorption Model ◽  
Star System ◽  
X Ray ◽  
Emission Component ◽  
The Past ◽  
Solar Composition ◽  
Low Mass

ABSTRACT The relatively small family of ultra-compact X-ray binary systems is of great interest for many areas of astrophysics. We report on a detailed X-ray spectral study of the persistent neutron star low-mass X-ray binary 1RXS J170854.4−321857. We analysed two XMM–Newton observations obtained in late 2004 and early 2005 when, in agreement with previous studies, the system displayed an X-ray luminosity (0.5–10 keV) of ${\sim} 1\times 10^{36}\, \mathrm{erg~s}^{-1}$. The spectrum can be described by a Comptonized emission component with Γ ∼ 1.9 and a distribution of seed photons with a temperature of ∼0.23 keV. A prominent residual feature is present at soft energies, which is reproduced by the absorption model if overabundances of Ne and Fe are allowed. We discuss how similar observables, which might be attributed to the peculiar (non-solar) composition of the plasma donated by the companion star, are a common feature in confirmed and candidate ultra-compact systems. Although this interpretation is still under debate, we conclude that the detection of these features along with the persistent nature of the source at such low luminosity and the intermediate–long burst that it displayed in the past confirms 1RXS J170854.4−321857 as a solid ultra-compact X-ray binary candidate.

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 Hardness Ratio in Evolving Low-Mass X-ray Binary Systems

1987 ◽  
Vol 125 ◽  
pp. 199-199
Author(s):  
J. Shaham ◽  
M. Tavani
Keyword(s):  
Neutron Star ◽  
Accretion Disk ◽  
Binary Systems ◽  
Spectral Component ◽  
Soft Component ◽  
Hard Component ◽  
X Ray ◽  
Low Mass ◽  
Additional Support ◽  
X Ray Binaries

Spectral observations of low-mass X-ray binaries (LMXBs) show that the soft component usually dominates over the hard one. These results provide additional support to an interpretation based on models of LMXBs in which the neutron star while, on the average, spinning up, is also experiencing a spinning down torque. Under these conditions, a fraction of the luminosity associated with the gravitational release of energy on the surface of the accreting neutron star may manifest itself as luminosity originating in the inner part of the accretion disk. It is probably possible to separate the two contributions; the stellar luminosity can be associated with the hard component of the spectrum and the disk luminosity, related to the exchange of energy due to the torque between the rapidly spinning neutron star and the accretion disk, can be associated with the soft spectral component.

scholarly journals The Galactic Pulsar Population and Neutron Star Birth

1987 ◽  
Vol 125 ◽  
pp. 67-78
Author(s):  
Ramesh Narayan
Keyword(s):  
Angular Momentum ◽  
Neutron Star ◽  
Binary Systems ◽  
Magnetic Coupling ◽  
Scale Height ◽  
High Magnetic Fields ◽  
Radio Pulsars ◽  
X Ray ◽  
The Galaxy ◽  
Low Mass

The radio pulsars in the Galaxy are found predominantly in the disk, with a scale height of several hundred parsecs. After allowing for pulsar velocities, the data are consistent with the hypothesis that single pulsars form from massive stellar progenitors. The number of active single pulsars in the Galaxy is ∼ 1.5 × 105, and their birthrate is 1 per ∼ 60 yrs. There is some evidence that many single pulsars, particularly those with high magnetic fields, are born spinning slowly, with initial periods ∼ 0.5–1s. This could imply an origin through binary “recycling” followed by orbit disruption, or might suggest that the pre-supernova stellar core efficiently loses angular momentum to the envelope through magnetic coupling. The birthrate of binary radio pulsars, particularly of the millisecond variety, seems to be much larger than previous estimates, and might suggest that these systems do not originate in low mass X-ray binary systems.

scholarly journals News on the X-ray emission from hot subdwarf stars

2017 ◽  
Vol 26 (1) ◽  
Author(s):  
Nicola La Palombara ◽  
Sandro Mereghetti
Keyword(s):  
Neutron Star ◽  
Binary Systems ◽  
High Sensitivity ◽  
Research Area ◽  
X Rays ◽  
Low Mass Stars ◽  
X Ray ◽  
Low Mass ◽  
Hot Subdwarfs ◽  
Weak Winds

AbstractIn latest years, the high sensitivity of the instruments on-board the XMM-Newton and Chandra satellites allowed us to explore the properties of the X-ray emission from hot subdwarf stars. The small but growing sample of X-ray detected hot subdwarfs includes binary systems, in which the X-ray emission is due to wind accretion onto a compact companion (white dwarf or neutron star), as well as isolated sdO stars, in which X-rays are probably due to shock instabilities in the wind. X-ray observations of these low-mass stars provide information which can be useful for our understanding of the weak winds of this type of stars and can lead to the discovery of particularly interesting binary systems. Here we report the most recent results we have recently obtained in this research area.

scholarly journals Millisecond Pulsar Surveys

1987 ◽  
Vol 125 ◽  
pp. 13-21
Author(s):  
D. C. Backer
Keyword(s):  
Mass Transfer ◽  
Stellar Evolution ◽  
Binary Systems ◽  
Rotation Period ◽  
Millisecond Pulsar ◽  
Millisecond Pulsars ◽  
X Ray ◽  
New Class ◽  
The Past ◽  
Low Mass

In 1982 a new class of pulsars was defined by the discovery of a star with a millisecond rotation period, 1.6 ms. In the past 3.5 years two additional pulsars with millisecond periods have been discovered. The rapid spin of these pulsars is attributed to mass transfer in a low-mass binary progenitor system. This hypothesis is supported by the presence of companions in two of the three millisecond pulsars. These recent discoveries have led both to a deeper understanding of the final stages of stellar evolution in binary systems, and to closer ties between the observational study of neutron stars by radio, optical and X-ray techniques. In addition the millisecond pulsars provide precise astrophysical clocks that can be used to improve the solar-system ephemeredes and to search for a background of gravitational waves that may have been produced in the early stages of the visible universe. Old and ongoing searches for new millisecond pulsars are described in this paper.

scholarly journals Some Constraints on Neutron Star Properties from Gamma Ray Burster Observations

1987 ◽  
Vol 125 ◽  
pp. 489-500
Author(s):  
K. Hurley
Keyword(s):  
Neutron Star ◽  
Low Temperature ◽  
Neutron Stars ◽  
Binary Systems ◽  
Main Sequence ◽  
Gamma Ray ◽  
Cooling Curves ◽  
X Ray ◽  
Upper Limits ◽  
Low Mass

The results of recent soft X-ray and optical searches for quiescent gamma ray burster counterparts are used to constrain the properties of the neutron stars responsible for bursters. Ages are restricted to the range 2×105 y and above based on temperature upper limits and theoretical cooling curves, or 107 y and above if bursters have evolved from pulsars. Velocities are greater than 20 km/s if the neutron stars are unmagnetized. Practically no main sequence star could have escaped detection in the optical/IR searches, so if the neutron stars are in binary systems, the companion is most likely a degenerate, low mass, low temperature object.

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 Hystereses in dwarf nova outbursts and low-mass X-ray binaries

2017 ◽  
Vol 600 ◽  
pp. A95 ◽  
Author(s):  
J.-M. Hameury ◽  
J.-P. Lasota ◽  
C. Knigge ◽  
E. G. Körding
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
White Dwarfs ◽  
Binary Systems ◽  
X Rays ◽  
X Ray ◽  
Dwarf Nova ◽  
Low Mass ◽  
Nova Outbursts ◽  
X Ray Binaries

Context. The disc instability model (DIM) successfully explains why many accreting compact binary systems exhibit outbursts during which their luminosity increases by orders of magnitude. The DIM correctly predicts which systems should be transient and works regardless of whether the accretor is a black hole, a neutron star, or a white dwarf. However, it has been known for some time that the outbursts of X-ray binaries, which contain neutron-star or black-hole accretors, exhibit hysteresis in the X-ray hardness-intensity diagram (HID). More recently, it has been shown that the outbursts of accreting white dwarfs also show hysteresis, but in a diagram combining optical, EUV, and X-ray fluxes. Aims. We examine the nature of the hysteresis observed in cataclysmic variables and low-mass X-ray binaries. Methods. We used our disc evolution code for modelling dwarf nova outbursts, and constructed the hardness intensity diagram as predicted by the disc instability model. Results. We show explicitly that the standard DIM, modified only to account for disc truncation, can explain the hysteresis observed in accreting white dwarfs, but cannot explain that observed in X-ray binaries. Conclusions. The spectral evidence for the existence of different accretion regimes or components (disc, corona, jets, etc.) should only be based on wavebands that are specific to the innermost parts of the discs, i.e. EUV and X-rays; this task is difficult because of interstellar absorption. The existing data, however, indicate that a hysteresis is in the EUV – X-ray domain is present in SS Cyg.

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