Decomposing Interacting Binary Light Curves: The Eclipses of the Mean Light, Secular Variability and Flickering in Rw Tri

1996 ◽  
pp. 33-34 ◽  
Author(s):  
Paul J. Bennie ◽  
R. W. Hilditch ◽  
Keith Horne
Keyword(s):  
Light Curves ◽  
Secular Variability ◽  
The Mean

scholarly journals Decomposing Interacting Binary Light Curves: The Eclipses of the Mean Light, Secular Variability and Flickering in RW Tri

1996 ◽  
Vol 158 ◽  
pp. 33-34
Author(s):  
Paul J. Bennie ◽  
R. W. Hilditch ◽  
Keith Horne
Keyword(s):  
Light Curve ◽  
Accretion Disc ◽  
Light Curves ◽  
New Method ◽  
Secular Variability ◽  
The Mean

AbstractWe describe a new method of orbital light curve decomposition which is applicable to long-term photometry of interacting binaries. This method determines the orbital dependence (including eclipses) of the mean light, secular variability and RMS flickering. We identify the true line of centres of RW Tri and find that the accretion disc is a location of secular variability and a source of flickering.

scholarly journals The Eclipses of the Close Binary Star BE UMa

1996 ◽  
Vol 158 ◽  
pp. 471-472
Author(s):  
Janet H. Wood ◽  
E. L. Robinson ◽  
E.-H. Zhang
Keyword(s):  
Light Curve ◽  
High Speed ◽  
Binary Star ◽  
Light Curves ◽  
Close Binary ◽  
Primary Star ◽  
Secondary Star ◽  
Different Depths ◽  
The Mean ◽  
Close Binary Star

BE UMa is a close binary star, not transferring mass, with an extremely hot primary star irradiating the inner face of the cool secondary star. The light curve shows a large-amplitude, sinusoidal variation with a period of 2.29 d, and an eclipse that is centered on the minimum of the variation [1], [3]. According to [1], the eclipse is partial, not total. However, it has been argued [2] that the eclipse was really flat bottomed and thus total. This has important repercussions for the deduced model of the system. To resolve this issue we obtained simultaneous UBVR photometry of BE UMa using the Stiening 4-channel, high-speed photometer on the 82-inch telescope at McDonald Observatory. The mean light curves are shown in Fig. 1. The eclipse in all colours is round bottomed and partial. The different depths are caused by the different contribution from the red secondary star in each bandpass.

scholarly journals On the role of evaporative wind in precataclysmic binaries (PCB)

1997 ◽  
Vol 180 ◽  
pp. 131-131
Author(s):  
I. Pustylnik ◽  
V. Pustynski
Keyword(s):  
Optical Depth ◽  
Black Body ◽  
Temperature Inversion ◽  
Light Curves ◽  
Gravitational Acceleration ◽  
Cool Component ◽  
First Results ◽  
The Mean ◽  
Absolutely Black Body ◽  
Definition Of

Recently we have started a systematic reevaluation of the existing observational methods of analysis hitherto applied to PCB-s. Here we report the first results of our investigations. The improved Napier's algorithm (Napier, 1968) to model the light curves of PCB (with the aid of the set of our computer programs in Turbo Pascal) is used. The source function is taken either from Sobieski (1965) or Strittmatter (1974). The entire luminosity received from the cool companion is calculated by integration of the emerging radiation over its disk; contributions from the illuminated and unilluminated portions of the disk are accounted for. We assume: a) the validity of the LTE in the photosphere of cool component, b) constancy of the monochromatic to mean absorption coefficient ratio within the photosphere, c) the hot star radiates as the absolutely black body, d) there are no other effects influencing the light curve except for the reflection effect. We have modelled the light curves of EC11575-1845 (Chen et al (1995). The analysis of the temperature distributions in the heated photosphere indicates the occurence of the temperature inversion. To make a rough estimate of physical conditions which can induce generation of evaporative wind we have used two criteria: i) the temperature inversion, ii) relation between radiative pressure and the effective gravitational acceleration. We assumed the density varies with the height in the atmosphere of the illuminated star as ρ ≃ exp(−Φ/RgT), Φ - being the Roche potential. The integral equation following from the definition of the mean optical depth was solved numerically to establish the relation between the mean optical depth and the distance in the atmosphere. We find the characteristic height scale for X-ray and EUV radiation is ∼ 106 − 107cm (for concentration of particles ∼ 1013cm−3). To check the validity of the ii) criterium we used a simplified model of radially expanding evaporative stellar wind and mass flux J conservation condition along the stream tube of the form J ∼ ρsvsrs2 exp −(Φ/RgT) (Pustylnik (1995)) and found M ∼ 10−12–10−11M/y. Although mass loss of such a rate cannot compete with the effects of the angular momentum loss which is responsible for a secular orbital shrinkage, the evaporative wind should significantly alter the structure of the the cool irradiated components.

scholarly journals New near-infrared JHKs light-curve templates for RR Lyrae variables

2019 ◽  
Vol 625 ◽  
pp. A1 ◽  
Author(s):  
V. F. Braga ◽  
P. B. Stetson ◽  
G. Bono ◽  
M. Dall’Ora ◽  
I. Ferraro ◽  
...  
Keyword(s):  
Light Curve ◽  
Near Infrared ◽  
Large Magellanic Cloud ◽  
Light Curves ◽  
Anchor Point ◽  
Phase Point ◽  
Pulsation Period ◽  
Rr Lyrae ◽  
The Mean ◽  
The Difference

We provide homogeneous optical (UBVRI) and near-infrared (NIR, JHK) time series photometry for 254 cluster (ω Cen, M 4) and field RR Lyrae (RRL) variables. We ended up with more than 551 000 measurements, of which only 9% are literature data. For 94 fundamental (RRab) and 51 first overtones (RRc) we provide a complete optical/NIR characterization (mean magnitudes, luminosity amplitudes, epoch of the anchor point). The NIR light curves of these variables were adopted to provide new light-curve templates for both RRc and RRab variables. The templates for the J and the H bands are newly introduced, together with the use of the pulsation period to discriminate among the different RRab templates. To overcome subtle uncertainties in the fit of secondary features of the light curves we provide two independent sets of analytical functions (Fourier and periodic Gaussian series). The new templates were validated by using 26 ω Cen and Bulge RRLs. We find that the difference between the measured mean magnitude along the light curve and the mean magnitude estimated by using the template on a single randomly extracted phase point is better than 0.01 mag (σ = 0.04 mag). We also validated the template on variables for which at least three phase points were available, but without information on the phase of the anchor point. We find that the accuracy of the mean magnitudes is also ∼0.01 mag (σ = 0.04 mag). The new templates were applied to the Large Magellanic Cloud (LMC) globular cluster Reticulum and by using literature data and predicted PLZ relations we find true distance moduli μ = 18.47 ± 0.10 (rand.) ± 0.03 (syst.) mag (J) and 18.49 ± 0.09 ± 0.05 mag (K). We also used literature optical and mid-infrared data and we found a mean μ of 18.47 ± 0.02 ± 0.06 mag, suggesting that Reticulum is ∼1 kpc closer than the LMC.

scholarly journals Studies of Large-Amplitude δ Scuti Variables

1993 ◽  
Vol 139 ◽  
pp. 104-104
Author(s):  
W. J. F. Wilson ◽  
E. F. Milone ◽  
D. J. I. Fry
Keyword(s):  
Radial Velocity ◽  
Large Amplitude ◽  
Light Curves ◽  
Pulsating Stars ◽  
Modest Contribution ◽  
The Mean ◽  
Absolute Magnitudes ◽  
Scuti Stars ◽  
Radial Velocity Data

The determination of Baade-Wesselink radii and luminosities for pulsating stars are long-standing and highly desired goals since they provide the promise of being standard candles. In a modest contribution towards these goals, we have undertaken a programme to determine the radii and luminosities of the large-amplitude δ Scuti stars DY Herculis, EH Librae and DY Pegasi from optical and infrared photometry and cross-correlated radial velocity data. We use Fourier representations for V, I and J light curves and for the radial velocity curves in Baade-Wesselink analyses to derive minimum radii over the pulsation cycles. These radii and their errors and the mean bolometric luminosities and absolute magnitudes will be discussed here and in papers to follow. As a check, we also apply our method to the data and results of other groups.

scholarly journals The Long-Term Behaviour of BY Dra

1995 ◽  
Vol 151 ◽  
pp. 103-105
Author(s):  
K.P. Panov ◽  
M.S. Ivanovo ◽  
J.S.W. Stegert
Keyword(s):  
Activity Cycle ◽  
Light Level ◽  
Light Curves ◽  
Sunspot Activity ◽  
The Past ◽  
Cyclic Variations ◽  
The Mean ◽  
Subsequent Rise ◽  
Visual Light

BY Dra has been extensively monitored for flares and spot-modulation of brightness at the Bulgarian National Astronomical Observatory (Panov & Ivanova 1993). Its mean light level exhibited remarkable changes in the past, due to the emergence and disintegration of photospheric spots, and different cycles have been proposed for the long-term changes of the BY Dra activity. This star is still believed to be a good candidate for cyclic variations, presumably similar to the sunspot activity cycle. After a spectacular drop in brightness in 1965 — 1967, and a subsequent rise in the early 70s, the mean light remained approximately constant during 1977 - 1991. A brightening of BY Dra occurred in 1992.In Fig. 1, the light curves are shown for 1991, 1992 and 1993 in the V-band and in B — V. Phases were calculated with the ephemeris of Chugainov (1966):JD (min. light) = 2438983.612 + 3.836 · EFrom Fig. 1, it is apparent that the mean visual light, which was about V = 8.20 in 1991, increased in 1992 by 0m.10, and a further increase by another 0m.03 occurred in 1993. The phase of minimum light in 1992 indicates that the position of the spot remained approximately the same in stellar longitude as in 1991. However, in 1993 the position of the spot changed by almost half a period.

scholarly journals New distance and depth estimates from observations of eclipsing binaries in the SMC

2008 ◽  
Vol 4 (S256) ◽  
pp. 57-62
Author(s):  
Pierre L. North ◽  
Romain Gauderon ◽  
Frédéric Royer
Keyword(s):  
Binary Stars ◽  
Binary Systems ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Average Error ◽  
Distance Modulus ◽  
Orbital Parameters ◽  
Individual System ◽  
The Mean

AbstractA sample of 33 eclipsing binaries observed in a field of the SMC with FLAMES@VLT is presented. The radial velocity curves obtained, together with existing OGLE light curves, allowed the determination of all stellar and orbital parameters of these binary systems. The mean distance modulus of the observed part of the SMC is 19.05 mag, based on the 26 most reliable systems. Assuming an average error of 0.1 mag on the distance modulus to an individual system, and a gaussian distribution of the distance moduli, we obtain a 2-σ depth of 0.36 mag or 10.6 kpc. Some results on the kinematics of the binary stars and of the H ii gas are also given.

scholarly journals Line Profile Variations in AGN

1994 ◽  
Vol 159 ◽  
pp. 395-395
Author(s):  
W. Kollatschny ◽  
M. Dietrich
Keyword(s):  
Seyfert Galaxy ◽  
Relative Strength ◽  
Light Curves ◽  
First Year ◽  
Line Profiles ◽  
Difference Spectra ◽  
Physical Conditions ◽  
Blue Wing ◽  
Blue Component ◽  
The Mean

An international collaboration is monitoring the variable Seyfert galaxy NGC 5548 in the optical spectral range since 1988. In Fig. 1 (left) the Hα light curves of the blue wing (–6000 until – 1000 km s−1) and the red wing (+1000 until + 6000 km s−1) are shown for the first year of the monitoring campaign from Dec.1988 until Oct.1989. It can be seen that these line components of the Hα profile have different amplitudes in the light curves. The mean Hα and Hβ difference spectra with respect to the minimum state are plotted in Fig. 1 (right) for the same period. The relative strength of the blue component at vrel = −2000 km s−1 is different with respect to the core of the line profiles. Therefore, these components originate under different physical conditions or in regions with different dust content. This work has been supported by DFG grant Ko 857/13-1

scholarly journals MANIA Complex – Hardware and Software for the Investigation of Optical Variability on Time Scales 10−7−102 s

1995 ◽  
Vol 151 ◽  
pp. 131-132
Author(s):  
G.M. Beskin ◽  
S.I. Neizvestny ◽  
V.L. Plokhotnichenko ◽  
A.I. Zhuravkov
Keyword(s):  
Time Scales ◽  
Photon Counting ◽  
Light Curves ◽  
Special Astrophysical Observatory ◽  
Synchronous Detection ◽  
Arrival Times ◽  
Multichannel Analysis ◽  
Astrophysical Objects ◽  
The Mean ◽  
Mean Time

One of the basic astrophysical problems is the search for and investigation of brightness fluctuations of celestial objects on time scales comparable with the mean time between registered photons. To facilitate this a special mathematical formalism was developed (Shwartsman 1977, Plokhotnichenko 1983).At the Special Astrophysical Observatory, photometric equipment has been developed which allows these ideas to be explored observationally and which also allows to study light curves of astrophysical objects using classical methods.This equipment and these methods are used in the search for and study of variable objects with time resolution 10−7 s in the MANIA (Multichannel Analysis of Nanosecond Intensity Alterations) experiment. The hardware consists of a photon-counting photometer for synchronous detection in different colour bands, a specialized “time-code” converter (Quantochron 3-16), measuring photon arrival times with an accuracy of 20 ns and a PC AT 386 and DAT-cassette recorder. Our equipment allows the uninterrupted accumulation of 108 photocounts with a rate up to 375 kHz without distortions in 28 or 216 parallel channels (Zhuravkov et al. 1994). The software permits the investigation of variability on time scales 10−7 − 102 s.

scholarly journals Mean Magnitudes and Colours of Six Cepheids in Three Red Globular Clusters of the Large Magellanic Cloud

1973 ◽  
Vol 21 ◽  
pp. 150-150
Author(s):  
Serge Demers
Keyword(s):  
Globular Clusters ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Classical Cepheids ◽  
The Galaxy ◽  
The Mean ◽  
Field Cepheids

AbstractPhotographic B and V light curves are determined for six variables, with periods longer than one day, in and near NGC 1751, NGC 1953, and NGC 2121. New photoelectric sequences are used to calibrate the plates. The mean magnitudes and colours of these variables are similar to the magnitudes and colours of Classical Cepheids of the same period. The photometric properties of these variables are unlike Population II Cepheids in the Galaxy but are comparable to field Cepheids of the Large Magellanic Cloud.

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