scholarly journals A comparative study of the strength of flickering in cataclysmic variables

2021 ◽  
Vol 503 (1) ◽  
pp. 953-971
Author(s):  
Albert Bruch
Keyword(s):  
Broad Band ◽  
Cataclysmic Variables ◽  
Absolute Magnitude ◽  
Primary Component ◽  
Band Spectrum ◽  
Orbital Inclination ◽  
Magnitude Distribution ◽  
Orbital Phase ◽  
Gaussian Fit ◽  
Data Points

ABSTRACT Flickering is a universal phenomenon in accreting astronomical systems that still defies detailed physical understanding. It is particularly evident in cataclysmic variables (CVs). Attempting to define boundary conditions for models, the strength of the flickering is measured in several thousand light curves of more than 100 CVs. The flickering amplitude is parametrized by the full width at half-maximum of a Gaussian fit to the magnitude distribution of data points in a light curve. This quantity requires several corrections before a comparison between different sources can be made. While no correlations of the flickering strength with simple parameters such as component masses, orbital inclination, or period were detected, a dependence on the absolute magnitude of the primary component and on the CV subtype is found. In particular, flickering in VY Scl type novalike variables is systematically stronger than in UX UMa type novalikes. The broad-band spectrum of the flickering light source can be fit by simple models but shows excess in the U band. When the data permitted to investigate the flickering strength as a function of orbital phase in eclipsing CVs, such a dependence was found, but it is different for different systems. Surprisingly, there are also indications for variations of the flickering strength with the superhump phase in novalike variables with permanent superhumps. In dwarf novae, the flickering amplitude is high during quiescence, drops quickly at an intermediate magnitude when the system enters into (or returns from) an outburst and, on average, remains constant above a given brightness threshold.

scholarly journals The broad-band spectrum of Cygnus X-1 measured by INTEGRAL

2006 ◽  
Vol 446 (2) ◽  
pp. 591-602 ◽  
Author(s):  
M. Cadolle Bel ◽  
P. Sizun ◽  
A. Goldwurm ◽  
J. Rodriguez ◽  
P. Laurent ◽  
...  
Keyword(s):  
Broad Band ◽  
Band Spectrum

scholarly journals γ DOR: A PULSATING COMPONENT OF KIC 8043961 IN A STELLAR TRIPLE SYSTEM

2020 ◽  
Vol 56 (2) ◽  
pp. 179-191
Author(s):  
C. Kamil ◽  
H. A. Dal ◽  
O. Özdarcan ◽  
E. Yoldaş
Keyword(s):  
Major Axis ◽  
Primary Component ◽  
Mass Ratio ◽  
Third Body ◽  
Semi Major Axis ◽  
Orbital Inclination ◽  
The Third ◽  
New Findings ◽  
Effective Temperatures ◽  
Orbit Model

We present new findings about KIC 8043961. We find the effective temperatures of the components as 6900 ± 200 K for the primary, and 6598 ± 200 K for the secondary, while the logarithm of the surface gravities are found to be 4.06 cm s-2 and 3.77 cm s-2, respectively. Combination of the light curve with the spectroscopic orbit model results leads to a mass ratio of 1.09 ± 0.07 with an orbital inclination of 73.71 ± 0.14 and a semi-major axis of 8.05 ± 0.22 R⨀ . Masses of the primary and secondary components are calculated as 1.379 ± 0.109 M⨀ and 1.513 ± 0.181 M⨀, while the radii are found to be 1.806 ± 0.084 R⨀ and 2.611 ± 0.059 R⨀. In addition, we obtain a considerable light contribution (≈0.54%) of a third body. We compute a possible mass for the third body as 0.778 ± 0.002 M⨀. We find that the primary component exhibits γ Dor type pulsations with 137 frequencies.

scholarly journals The HR Diagram

1978 ◽  
Vol 80 ◽  
pp. 101-116
Author(s):  
Jesse L. Greenstein
Keyword(s):  
Chemical Composition ◽  
Broad Band ◽  
Wavelength Region ◽  
Absolute Magnitude ◽  
Coordinate Space ◽  
Evolutionary Status ◽  
Bolometric Luminosity ◽  
The Galaxy ◽  
Stellar Masses ◽  
Hr Diagram

The HR diagram is a useful shorthand locating a star in a two-coordinate space. For the astrophysicist, the y-coordinate is bolometric luminosity, Mbol, the x-coordinate, effective temperature, Teff. Objects of given chemical composition, age (or evolutionary status) are labeled in the xy plane by mass. For an observer, y may be apparent or absolute magnitude in a certain wavelength region and x may be spectral type or color. The HR diagrams for populations differ because of age, chemical composition and stellar masses present. HR diagrams are often of mixed nature; some involve observables others derived or semi-theoretical quantities. I will display various types of HR diagrams for low-luminosity stars. For galactic or extragalactic studies the HR diagram needs a further dimension, the frequency of stars at an x,y. The mass of the Galaxy, but not its light, may be dominated by M dwarfs. HR diagrams are also interesting for their nearly empty spaces. In Fig. 1 we show as a sample, the basic results of the U.S. Naval Observatory parallax program, in which broad band (B-V) colors define the visual luminosity, My, on the main (MS) and degenerate (WD) sequences.

REVIEW AND A MODEL OF PRE-SEISMIC ELECTROMAGNETIC EMISSIONS IN TERMS OF FRACTAL ELECTRODYNAMICS

Fractals ◽  
2004 ◽  
Vol 12 (02) ◽  
pp. 243-273 ◽  
Author(s):  
K. EFTAXIAS ◽  
P. FRANGOS ◽  
P. KAPIRIS ◽  
J. POLYGIANNAKIS ◽  
J. KOPANAS ◽  
...  
Keyword(s):  
Critical Point ◽  
Scaling Laws ◽  
Critical Phenomenon ◽  
Crack Opening ◽  
Broad Band ◽  
Ground Surface ◽  
Band Spectrum ◽  
Omori Law ◽  
Transient Electromagnetic ◽  
Electromagnetic Emissions

We introduce a new model of the generation of pre-seismic electromagnetic emissions, which explains the observed phenomenology in terms of its geometry and fractal electrodynamics. Accumulated evidence indicates that an earthquake can be viewed as a critical phenomenon culminating in a large event that corresponds to a type of critical point. The principle feature of criticality is the fractal organization in both space and time. Earthquakes display a complex spatio-temporal behavior: in addition to the regularity in the rate of occurrence (e.g. Gutenberg-Richter law, Omori law), the spatial distribution of epicenters is fractal and earthquakes occur on a fractal structure of faults. Thus, the hypothesis that the fault develops as a fractal is reasonable. A mounting body of laboratory evidence suggests that micro-fracturing of rocks are associated with the appearance of spontaneous charge production and transient electromagnetic emissions (EME). The emitting, diffusing and recombination charge accompanying the micro-fracturing, can act as current generated during the crack opening. In this view, an active crack or rupture, can be simulated by a "radiating element." The idea is that a fractal geo-antenna (FGA) can be formed as an array of line elements having a fractal distribution on the ground surface as the critical point is approached. We test this idea in terms of fractal electrodynamics: we argue that the precursory VLF-VHF EM signals associated with recent earthquakes in Greece are governed by characteristics (e.g. scaling laws, temporal evolution of the spectrum content, broad band spectrum region and accelerating emission rate) predicted by fractal electrodynamics.

scholarly journals Improved system for identifying biological tissue temperature using electrical impedance tomography

2018 ◽  
Vol 158 ◽  
pp. 01019 ◽  
Author(s):  
Evgeniy Korolyuk ◽  
Konstantin Brazovskii
Keyword(s):  
Electrical Impedance ◽  
Saline Water ◽  
Broad Band ◽  
Experimental Studies ◽  
Impedance Spectrum ◽  
Target Object ◽  
Tissue Temperature ◽  
Band Spectrum ◽  
Measuring Chamber ◽  
Impedance Tomography

This paper proposes a cheap and compact medical system that determines the temperature of an object using broadband impedance tomography. This system can be used in medicine to visualize ice structure in tissue during cryosurgical operations, as well as for fault diagnosis and location in studied industrial objects. These effects are achieved by measuring electrical impedance between electrode pairs in the measuring chamber. The assembled prototype is compact, consumes little power, and allows to non-invasively determine the impedance of a target object in real time. The research included experimental studies to determine the dependence of the impedance spectrum of saline water and muscle tissue on temperature in broad band spectrum, which allowed to obtain the dependence of total electrical impedance of target objects on temperature.

scholarly journals OSSOS. II. A SHARP TRANSITION IN THE ABSOLUTE MAGNITUDE DISTRIBUTION OF THE KUIPER BELT’S SCATTERING POPULATION

2016 ◽  
Vol 151 (2) ◽  
pp. 31 ◽  
Author(s):  
C. Shankman ◽  
JJ. Kavelaars ◽  
B. J. Gladman ◽  
M. Alexandersen ◽  
N. Kaib ◽  
...  
Keyword(s):  
Absolute Magnitude ◽  
Sharp Transition ◽  
Magnitude Distribution ◽  
The Absolute

scholarly journals A new absolute magnitude calibration with 2MASS for cataclysmic variables

New Astronomy ◽  
2007 ◽  
Vol 12 (6) ◽  
pp. 446-453 ◽  
Author(s):  
T. Ak ◽  
S. Bilir ◽  
S. Ak ◽  
A. Retter
Keyword(s):  
Cataclysmic Variables ◽  
Absolute Magnitude

scholarly journals Stellar Exotica in 47 Tucanae

2007 ◽  
Vol 3 (S246) ◽  
pp. 321-325
Author(s):  
C. Knigge ◽  
A. Dieball ◽  
J. Maíz-Apellániz ◽  
K. S. Long ◽  
D. R. Zurek ◽  
...  
Keyword(s):  
Binary System ◽  
White Dwarf ◽  
Broad Band ◽  
Cataclysmic Variables ◽  
Ultraviolet Spectroscopy ◽  
The Core ◽  
Blue Straggler ◽  
Far Ultraviolet

AbstractWe have used far-ultraviolet spectroscopy and broad-band photometry to identify and study dynamically-formed stellar exotica in the core of 47 Tucanane. Here, we present a subset of our main results, including: (i) the spectroscopic confirmation of three cataclysmic variables; (ii) the discovery of stripped sub-giant core in a binary system with a dark primary; (iii) the discovery of a Helium white dwarf; (iv) the discovery of a blue straggler with a white dwarf companion.

scholarly journals A Model of the Broad-Band Continuum of NGC 5548

1998 ◽  
Vol 188 ◽  
pp. 430-431
Author(s):  
P. Magdziarz ◽  
O. Blaes
Keyword(s):  
Broad Band ◽  
Continuum Emission ◽  
Band Spectrum ◽  
Complex Phase ◽  
Disk Structure ◽  
Three Phase ◽  
Central Disk ◽  
Ngc 5548 ◽  
Excess Component ◽  
The Continuum

We discuss a model of the central source in Seyfert 1 galaxy NGC 5548. The model assumes a three phase disk structure consisting of a cold outer disk, a hot central disk constituting a Comptonizing X/γ source, and an intermediate unstable and complex phase emitting a soft excess component. The model qualitatively explains broad-band spectrum and variability behavior assuming that the soft excess contributes significantly to the continuum emission and drives variability by geometrical changes of the intermediate disk zone.

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