scholarly journals Simultaneous detection of an intrinsic absorber and a compact jet emission in the X-ray binary IGR J17091−3624 during a hard accretion state

2019 ◽  
Vol 491 (4) ◽  
pp. 4857-4868 ◽  
Author(s):  
E Gatuzz ◽  
M Díaz Trigo ◽  
J C A Miller-Jones ◽  
S Migliari
Keyword(s):  
Black Hole ◽  
Detailed Analysis ◽  
Simultaneous Detection ◽  
The Other ◽  
Radio Observations ◽  
X Ray ◽  
Other Hand ◽  
Low Mass ◽  
Ionization Parameter ◽  
Compact Array

ABSTRACT We present a detailed analysis of three XMM–Newton observations of the black hole low-mass X-ray binary IGR J17091−3624 taken during its 2016 outburst. Radio observations obtained with the Australia Telescope Compact Array indicate the presence of a compact jet during all observations. From the best X-ray data fit results, we concluded that the observations were taken during a transition from a hard accretion state to a hard-intermediate accretion state. For Observations 1 and 2, a local absorber can be identified in the EPIC-pn spectra but not in the RGS spectra, preventing us from distinguishing between absorption local to the source and that from the hot ISM component. For Observation 3, on the other hand, we have identified an intrinsic ionized static absorber in both EPIC-pn and RGS spectra. The absorber, observed simultaneously with a compact jet emission, is characterized by an ionization parameter of 1.96 < log ξ < 2.05 and traced mainly by Ne x, Mg xii, Si xiii, and Fe xviii.

scholarly journals The MAVERIC survey: a hidden pulsar and a black hole candidate in ATCA radio imaging of the globular cluster NGC 6397

2020 ◽  
Vol 493 (4) ◽  
pp. 6033-6049 ◽  
Author(s):  
Yue Zhao ◽  
Craig O Heinke ◽  
Vlad Tudor ◽  
Arash Bahramian ◽  
James C A Miller-Jones ◽  
...  
Keyword(s):  
Black Hole ◽  
Globular Cluster ◽  
Radio Observation ◽  
Millisecond Pulsar ◽  
Radio Flux ◽  
X Ray ◽  
Black Hole Candidate ◽  
Radio Imaging ◽  
Low Mass ◽  
Compact Array

ABSTRACT Using a 16.2-h radio observation by the Australia Telescope Compact Array and archival Chandra data, we found >5σ radio counterparts to four known and three new X-ray sources within the half-light radius (rh) of the Galactic globular cluster NGC 6397. The previously suggested millisecond pulsar (MSP) candidate, U18, is a steep-spectrum (Sν ∝ να; $\alpha =-2.0^{+0.4}_{-0.5}$) radio source with a 5.5-GHz flux density of 54.7 ± 4.3 $\mu \mathrm{ Jy}$. We argue that U18 is most likely a ‘hidden’ MSP that is continuously hidden by plasma shocked at the collision between the winds from the pulsar and companion star. The non-detection of radio pulsations so far is probably the result of enhanced scattering in this shocked wind. On the other hand, we observed the 5.5-GHz flux of the known MSP PSR J1740−5340 (U12) to decrease by a factor of >2.8 during epochs of 1.4-GHz eclipse, indicating that the radio flux is absorbed in its shocked wind. If U18 is indeed a pulsar whose pulsations are scattered, we note the contrast with U12’s flux decreases in eclipse, which argues for two different eclipse mechanisms at the same radio frequency. In addition to U12 and U18, we also found radio associations for five other Chandra X-ray sources, four of which are likely background galaxies. The last, U97, which shows strong H α variability, is mysterious; it may be either a quiescent black hole low-mass X-ray binary or something more unusual.

scholarly journals Puzzling blue dips in the black hole candidate Swift J1357.2 − 0933, from ULTRACAM, SALT, ATCA, Swift, and NuSTAR

2019 ◽  
Vol 488 (1) ◽  
pp. 512-524 ◽  
Author(s):  
J A Paice ◽  
P Gandhi ◽  
P A Charles ◽  
V S Dhillon ◽  
T R Marsh ◽  
...  
Keyword(s):  
Black Hole ◽  
Binary Systems ◽  
Radio Observations ◽  
X Ray ◽  
Black Hole Candidate ◽  
Low Mass ◽  
Absorption Features

Abstract We present rapid, multiwavelength photometry of the low-mass X-ray binary Swift J1357.2-0933 during its 2017 outburst. Using several sets of quasi-simultaneous ULTRACAM/NTT (optical), NuSTAR (X-ray), XRT/Swift (X-ray), SALT (optical), and ATCA (radio) observations taken during outburst decline, we confirm the frequent optical dipping that has previously been noted both in outburst and in quiescence. We also find: (1) that the dip frequency decreases as the outburst decays, similar to what was seen in the previous outburst, (2) that the dips produce a shape similar to that in binary systems with partial disc occultations, (3) that the source becomes significantly bluer during these dips, indicating an unusual geometry compared to other LMXB dippers, and (4) that dip superposition analysis confirms the lack of an X-ray response to the optical dips. These very unusual properties appear to be unique to Swift J1357.2−0933, and are likely the result of a high binary inclination, as inferred from features such as its very low outburst X-ray luminosity. From this analysis as well as X-ray/optical timing correlations, we suggest a model with multicomponent emission/absorption features with differing colours. This could include the possible presence of a sporadically occulted jet base and a recessed disc. This source still hosts many puzzling features, with consequences for the very faint X-ray transients population.

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 White Dwarf Masses and Accretion Rates of Recurrent Novae: an X-ray Perspective

2011 ◽  
Vol 7 (S281) ◽  
pp. 186-189
Author(s):  
Koji Mukai ◽  
Jennifer L. Sokoloski ◽  
Thomas Nelson ◽  
Gerardo J. M. Luna
Keyword(s):  
White Dwarf ◽  
Cataclysmic Variables ◽  
The Other ◽  
X Ray ◽  
Other Hand ◽  
Accretion Rates

AbstractWe present recent results of quiescent X-ray observations of recurrent novae (RNe) and related objects. Several RNe are luminous hard X-ray sources in quiescence, consistent with accretion onto a near Chandrasekhar mass white dwarf. Detection of similar hard X-ray emissions in old novae and other cataclysmic variables may lead to identification of additional RNe candidates. On the other hand, other RNe are found to be comparatively hard X-ray faint. We present several scenarios that may explain this dichotomy, which should be explored further.

scholarly journals The relationship between body weight and exterior measurements in domestic ostriches during the first four months after hatching

2007 ◽  
Vol 23 (1-2) ◽  
pp. 13-20
Author(s):  
Andrey Kurtenkov
Keyword(s):  
Body Weight ◽  
Detailed Analysis ◽  
The Body ◽  
The Other ◽  
Phenotypic Correlation ◽  
Other Hand ◽  
The One ◽  
The Relationship ◽  
Selection Of

It is related leg problems to the realization of the necessity of doing a detailed analysis of the phenotype correlations between body weight and exterior measurements. As a result of the study, lower coefficients have been obtained of the correlation between the girth of the tarso metatarsus on one hand, and the body weight and the girth behind the wings, on the other hand (respectively 0.563 and 0.608), compared with the one between the body weight and the girth behind the wings (0.898). It is advisable in the selection of ostriches to take into consideration the necessity of a higher phenotypic correlation between the girth of the tarso metatarsus on the one hand, and the body weight and the girth behind the wings on the other hand, with a view to preventing leg problems.

Synthesis of ZrO2 Nanotubes by Anodization of Zr Foil

2015 ◽  
Vol 799-800 ◽  
pp. 125-129
Author(s):  
Mary Donnabelle L. Balela ◽  
April Alexa S. Lagarde ◽  
Stephen Jann A. Tamayo ◽  
Nikko S. Villareal ◽  
Ann Marielle Parreno
Keyword(s):  
Aqueous Solution ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Surface Preparation ◽  
The Other ◽  
Preparation Methods ◽  
X Ray ◽  
Anodization Time ◽  
Other Hand ◽  
Scanning Electron

Zirconia (ZrO2) nanotubes were synthesized by anodization of zirconium (Zr) foil in NH4Fand (NH4)2SO4 aqueous solution. Different surface preparation methods (electropolishing and etching) were applied on the Zr foil prior to anodizaton. In addition, the anodization time and NH4F concentration were varied. The structure and morphologies of the nanotubes and their crystallinity were confirmed using scanning electron microscope and x-ray diffractometer, respectively. ZrO2 nanotubes with large diameters and thick walls were formed at lower NH4F concentration and longer anodization time. On the other hand, smaller nanotubes with thinner walls were produced when the NH4F concentration was increased. The synthesized nanotubes were predominantly tetragonal ZrO2 with small amounts of monoclinic ZrO2.

scholarly journals Formation of black hole low-mass X-ray binaries

2015 ◽  
Vol 64-66 ◽  
pp. 1-6 ◽  
Author(s):  
Xiang-Dong Li
Keyword(s):  
Black Hole ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

Distribution of Calcium and Phosphate in Cells of the Enamel Organ in the Rat Lower Incisor

1987 ◽  
Vol 1 (2) ◽  
pp. 236-244 ◽  
Author(s):  
T. Kawamoto ◽  
M. Shimizu
Keyword(s):  
The Other ◽  
Whole Body ◽  
Enamel Organ ◽  
Maturation Stage ◽  
Lower Incisor ◽  
X Ray ◽  
Other Hand ◽  
Freeze Dried ◽  
Significant Difference ◽  
Cell Layers

The distribution of calcium and phosphate in the cells of the enamel organ of the rat lower incisors was investigated by autoradiography and energy-dispersive x-ray spectrometry (EDS). Radioactive calcium or phosphate was injected i.p. into seven-day-old rats of the Wistar strain. The animals were frozen 0.5, 1, and 10 min after injection, and embedded in 5% carboxymethyl cellulose. Sagittal sections of 10 μm thickness were made in which the lower incisor was included as a part of the whole-body section. For autoradiography, the sections were freeze-dried and placed in contact with dry thin films prepared from autoradiographic emulsion. For EDS, sections were mounted on carbon stubs, freeze-dried, coated with carbon, and examined by EDS in a SEM. 45Ca and 32P autoradiograms showed that the radioactivity was located over the papillary layer cells adjacent to the secretory stage ameloblasts and was much higher here than in the ameloblastic layer. On the other hand, there was no significant difference between the amount of radioactivity of these two cell layers in the maturation stage, although higher radioactivity was detectable in the maturation stage enamel than in the secretory stage enamel. Pronounced Ka x-ray peaks were obtained for P, S, Cl, and K originating from the cells of the papillary and ameloblastic layers in the secretory stage, but only very low peaks were obtained for Ca. On the other hand, in addition to these elements, remarkably high Ca and Fe peaks could be detected in the ameloblastic layer of the maturation stage.

scholarly journals Year-scale Morphological Variation of the X-ray Crab Nebula

2004 ◽  
Vol 218 ◽  
pp. 181-184 ◽  
Author(s):  
Koji Mori ◽  
David N. Burrows ◽  
George G. Pavlov ◽  
J. Jeff Hester ◽  
Shinpei Shibata ◽  
...  
Keyword(s):  
Morphological Variation ◽  
Crab Nebula ◽  
The Other ◽  
X Ray ◽  
Morphological Variations ◽  
Other Hand ◽  
Pulsar Wind ◽  
Circular Structures ◽  
The Crab Nebula

We present year-scale morphological variations of the Crab Nebula revealed by the Chandra X-ray Observatory. Observations have been performed about every 1.7 years over the three years from launch. The variations are clearly recognized at two sites: the torus and the southern jet. The torus, which had been steadily expanding until 1.7 years ago, now appears to have shrunk in the latest observation. Additionally, the circular structures seen to the northeast of the torus have decayed into several arcs. On the other hand, the southern jet shows the growth of its overall kinked-structure. We discuss the nature of these variations in terms of the pulsar wind nebula mechanism.

scholarly journals A broad-band X-ray spectral study of the Seyfert 1 galaxy ESO 141–G055 with XMM–Newton and NuSTAR

2020 ◽  
Vol 497 (4) ◽  
pp. 4213-4221
Author(s):  
Ritesh Ghosh ◽  
Sibasish Laha
Keyword(s):  
Black Hole ◽  
Spectral Study ◽  
Column Density ◽  
Broad Band ◽  
Accretion Disc ◽  
Physical Models ◽  
X Ray ◽  
Reflection Model ◽  
Ionization Parameter

ABSTRACT We have extensively studied the broad--band X-ray spectra of the source ESO 141–G055 using all available XMM–Newton and NuSTAR observations. We detect a prominent soft excess below $2\rm \, \, {\rm keV}$, a narrow Fe line, and a Compton hump ($\gt 10\rm \, \, {\rm keV}$). The origin of the soft excess is still debated. We used two models to describe the soft excess: the blurred reflection from the ionized accretion disc and the intrinsic thermal Comptonization model. We find that both of these models explain the soft excess equally well. We confirm that we do not detect any broad Fe line in the X-ray spectra of this source, although both the physical models prefer a maximally spinning black hole scenario (a > 0.96). This may mean that either the broad Fe line is absent or blurred beyond detection. The Eddington rate of the source is estimated to be $\lambda _{\rm \, Edd}\sim 0.31$. In the reflection model, the Compton hump has a contribution from both ionized and neutral reflection components. The neutral reflector which simultaneously describes the narrow Fe K α and the Compton hump has a column density of $N_{\rm H} \ge 7\times 10^{24} \, \rm cm^{-2}$. In addition, we detect a partially covering ionized absorption with ionization parameter $\log \xi /\rm \, erg\, cm\, s^{-1}$  = $0.1^{+0.1}_{-0.1}$ and column density $N_{\rm H} =20.6^{+1.0}_{-1.0}\times 10^{22} \, \rm cm^{-2}$ with a covering factor of $0.21^{+0.01}_{-0.01}$.

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