CONFIRMING THE ORBITAL X-RAY VARIABILITY OF LS 5039 THROUGH CHANDRA OBSERVATIONS

2008 ◽  
Vol 17 (10) ◽  
pp. 1867-1873 ◽  
Author(s):  
V. ZABALZA ◽  
J. M. PAREDES ◽  
V. BOSCH-RAMON
Keyword(s):  
Intrinsic Properties ◽  
X Ray ◽  
Flux Variability ◽  
Orbital Phase ◽  
Emission Models ◽  
Orbital Cycle

We present an analysis of two Chandra observations of LS 5039 performed in 2004 in two different orbital phases during the same orbital cycle. Our results show a clear flux variability, confirming a trend of increasing flux with orbital phase in the range 0.05 ≲ ϕ ≲ 0.7 as has been found in XMM observations carried out in 2005 during the same orbital cycle. We suggest that the X-ray variations are linked to orbital changes of the intrinsic properties of the emitter, which should have implications for possible emission models to explain the present multiwavelength knowledge of the source.

scholarly journals Aperiodic Flux Variability in A 0535+262

1996 ◽  
Vol 165 ◽  
pp. 313-319
Author(s):  
Mark H. Finger ◽  
Robert B. Wilson ◽  
B. Alan Harmon ◽  
William S. Paciesas
Keyword(s):  
Neutron Star ◽  
Gamma Ray ◽  
Beat Frequency ◽  
Power Spectra ◽  
Center Frequency ◽  
X Ray ◽  
Binary Pulsar ◽  
Transient Source ◽  
Flux Variability ◽  
Burst And Transient Source

A “giant” outburst of A 0535+262, a transient X-ray binary pulsar, was observed in 1994 February and March with the Burst and Transient Source Experiment (BATSE) onboard the Compton Gamma-Ray Observatory. During the outburst power spectra of the hard X-ray flux contained a QPO-like component with a FWHM of approximately 50% of its center frequency. Over the course of the outburst the center frequency rose smoothly from 35 mHz to 70 mHz and then fell to below 40 mHz. We compare this QPO frequency with the neutron star spin-up rate, and discuss the observed correlation in terms of the beat frequency and Keplerian frequency QPO models in conjunction with the Ghosh-Lamb accretion torque model.

scholarly journals Image Segmentation Techniques in Bone Structure Psychiatry

2020 ◽  
Vol 9 (07) ◽  
pp. 25102-25112
Author(s):  
Ajayi Olayinka Adedoyin ◽  
Olamide Timothy Tawose ◽  
Olu Sunday Adetolaju
Keyword(s):  
Image Segmentation ◽  
Bone Structure ◽  
Performance Comparison ◽  
Imaging Systems ◽  
Intrinsic Properties ◽  
X Ray ◽  
Practical Applications ◽  
X Ray Imaging ◽  
Segmentation Algorithms ◽  
Bone Structures

Today, a large number of x-ray images are interpreted in hospitals and computer-aided system that can perform some intelligent task and analysis is needed in order to raise the accuracy and bring down the miss rate in hospitals, particularly when it comes to diagnosis of hairline fractures and fissures in bone joints. This research considered some segmentation techniques that have been used in the processing and analysis of medical images and a system design was proposed to efficiently compare these techniques. The designed system was tested successfully on a hand X-ray image which led to the proposal of simple techniques to eliminate intrinsic properties of x-ray imaging systems such as noise. The performance and accuracy of image segmentation techniques in bone structures were compared and these eliminated time wasting on the choice of image segmentation algorithms. Although there are several practical applications of image segmentation such as content-based image retrieval, machine vision, medical imaging, object detection, recognition tasks, etc., this study focuses on the performance comparison of several image segmentation techniques for medical X-ray images.

scholarly journals An unusual transient following the short GRB 071227

2019 ◽  
Vol 489 (1) ◽  
pp. 13-27
Author(s):  
R A J Eyles ◽  
P T O’Brien ◽  
K Wiersema ◽  
R L C Starling ◽  
B P Gompertz ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Thermal Emission ◽  
Chemical Properties ◽  
Major Axis ◽  
Optical Observations ◽  
X Ray ◽  
Very Large Telescope ◽  
The Galaxy ◽  
Simple Extrapolation ◽  
Emission Models

ABSTRACT We present X-ray and optical observations of the short duration gamma-ray burst GRB 071227 and its host at z = 0.381, obtained using Swift, Gemini South, and the Very Large Telescope. We identify a short-lived and moderately bright optical transient, with flux significantly in excess of that expected from a simple extrapolation of the X-ray spectrum at 0.2–0.3 d after burst. We fit the SED with afterglow models allowing for high extinction and thermal emission models that approximate a kilonova to assess the excess’ origins. While some kilonova contribution is plausible, it is not favoured due to the low temperature and high luminosity required, implying superluminal expansion and a large ejecta mass of ∼0.1 M$\odot$. We find, instead, that the transient is broadly consistent with power-law spectra with additional dust extinction of E(B − V) ∼ 0.4 mag, although a possibly thermal excess remains in the z band. We investigate the host, a spiral galaxy with an edge-on orientation, resolving its spectrum along its major axis to construct the galaxy rotation curve and analyse the star formation and chemical properties. The integrated host emission shows evidence for high extinction, consistent with the afterglow findings. The metallicity and extinction are consistent with previous studies of this host and indicate the galaxy is a typical, but dusty, late-type SGRB host.

scholarly journals X-Ray Emission from Expanding Shells in NGC 3077

2004 ◽  
Vol 217 ◽  
pp. 310-311
Author(s):  
Jürgen Ott ◽  
Crystal L. Martin ◽  
Fabian Walter
Keyword(s):  
Thermal Emission ◽  
Dwarf Galaxy ◽  
Point Sources ◽  
Starburst Galaxy ◽  
Interstellar Gas ◽  
X Ray ◽  
Hot Gas ◽  
Hα Emission ◽  
Emission Models ◽  
Expanding Shells

Deep Chandra observations of NGC 3077, a starburst dwarf galaxy in the M81 triplet, resolve the X-ray emission from several supershells. The emission is brightest in the cavities defined by expanding shells detected previously in Hα emission. Thermal emission models fitted to the data imply temperatures ranging from 1.3 to 4.9 × 106 K. The total 0.3–6.0 keV X-ray luminosity is 2 − 5 × 1039ergs−1 (depending on the selected thermal plasma model). Most (85%) of the X-ray luminosity in NGC 3077 comes from the hot interstellar gas; the remainder comes from six X-ray point sources. The radial density profile of the hot gas is not as steep as that expected in a freely expanding wind (e.g., as seen in the neighboring starburst galaxy M 82) implying that the hot gas is still confined by the Hα shells.

scholarly journals Line Structures in the X-ray Spectra of Cygnus X-2 Observed With EXOSAT

1990 ◽  
Vol 115 ◽  
pp. 197-200
Author(s):  
P. E. Freeman ◽  
S. M. Kahn ◽  
L. Chiappetti ◽  
E. G. Tanzi ◽  
A. Ciapi ◽  
...  
Keyword(s):  
X Ray ◽  
Five Phases ◽  
Orbital Cycle

AbstractCygnus X-2 was observed with EXOSAT at five phases of a single orbital cycle in September of 1983. We will summarize the results of spectral fits of the LE + ME (Argon) data in terms of a superposition of thermal bremstrahlung and blackbody components. During the first observation a grating spectrum was obtained and this is described in some detail. The GSPC data are used to investigate the presence of iron features, and their behavior during dips.

scholarly journals Gamma-Ray Pulsar Emission Models

1996 ◽  
Vol 160 ◽  
pp. 315-322 ◽  
Author(s):  
Alice K. Harding
Keyword(s):  
Spectral Index ◽  
Gamma Ray ◽  
High Energy ◽  
Pulsar Emission ◽  
High Energy Radiation ◽  
X Ray ◽  
Gamma Ray Detectors ◽  
Emerging Patterns ◽  
Increased Sensitivity ◽  
Emission Models

AbstractWith the increased sensitivity of gamma-ray detectors on the Compton Gamma-Ray Observatory (CGRO) the number of presently known gamma-ray pulsars has grown. The new detections are beginning to provide clues to the origin of the high-energy radiation in the form of emerging patterns and correlations among observed quantities such as gamma-ray efficiency and spectral index vs. age. But there are still many questions about the location of the emission and its relation to the radio, optical and X-ray pulses. This paper will review models for gamma-ray emission from pulsars and will examine how well the detailed predictions of these models account for the existing observations.

Three-band observations of the soft X-ray background and some implications of thermal emission models

1977 ◽  
Vol 213 ◽  
pp. 405 ◽  
Author(s):  
P. Burstein ◽  
R. J. Borken ◽  
W. L. Kraushaar ◽  
W. T. Sanders
Keyword(s):  
Thermal Emission ◽  
X Ray ◽  
Emission Models ◽  
X Ray Background

X‐Ray and Ultraviolet Orbital Phase Dependence in LMC X‐3

2001 ◽  
Vol 555 (2) ◽  
pp. 822-828 ◽  
Author(s):  
Patricia T. Boyd ◽  
Alan P. Smale ◽  
Joseph F. Dolan
Keyword(s):  
Phase Dependence ◽  
X Ray ◽  
Orbital Phase

scholarly journals Infrared spectroscopic variability of Cygnus X-3

1999 ◽  
Vol 193 ◽  
pp. 358-359
Author(s):  
Margaret M. Hanson ◽  
Rob P. Fender ◽  
G.G. Pooley
Keyword(s):  
Mass Transfer ◽  
High Resolution ◽  
Ir Spectroscopy ◽  
Spherically Symmetric ◽  
X Rays ◽  
Spectral Variability ◽  
X Ray ◽  
Orbital Phase ◽  
Band Spectra ◽  
Binary Orbit

We present four epochs of high-resolution IR spectroscopy of the peculiar X-ray binary Cygnus X-3. The observations cover quiescent, small flaring and outburst states of the system as defined by radio and X-ray monitoring. The underlying IR spectrum of the source, as observed during radio and X-ray quiescence and small flaring states is one of broad, weak He II and N V emission. Spectral variability in this state is dominated by modulation at the 4.8 hr orbital period of the system. H-band spectra confirm the significant hydrogen depletion of the mass donor. In outburst, the infrared spectrum is dramatically different, with the appearance of very strong twin-peaked He I emission displaying both day-to-day variability and V (iolet) / R(ed) variations with orbital phase. We argue that the most likely explanation appears to be an enhanced stellar wind from the companion. Thus the X-ray and radio outbursts in this system are likely to originate in mass-transfer, and not disc instabilities. We suggest that the wind in Cyg X-3 is significantly flattened in the plane of the binary orbit. This may explain the observed twin-peaked He I features as well as reconcile the large infrared luminosity with the large optical depth to X-rays if Cyg X-3 is embedded in a spherically symmetric wind.

scholarly journals Full Phase Coverage of BY Dra with the VLA

1991 ◽  
Vol 130 ◽  
pp. 494-497
Author(s):  
Jean-Pierre Caillault ◽  
Stephen Drake
Keyword(s):  
Amplitude Distribution ◽  
Light Curves ◽  
Optical Counterpart ◽  
X Ray ◽  
Orbital Phase ◽  
Spotted Star

AbstractWe have obtained 21 ~one-hour observations of the prototypical spotted star, BY Dra, with the VLA. These data are sufficiently well spaced in time to allow for complete rotational and orbital phase coverage; the resultant radio light curves are compared to their optical counterpart. We also plot the emission versus time without phase-folding, in order to search for longer periods of activity. Splitting the data into smaller (three minute) time bins allows for the determination of the normalized amplitude distribution of the flux; we compare this with known stellar optical and X-ray flare distributions.

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