scholarly journals High-Level Magnetic Activity on a Low-Mass Close Binary: GSC 02038-0293

2012 ◽  
Vol 29 (2) ◽  
pp. 150-160 ◽  
Author(s):  
H. A. Dal ◽  
E. Sipahi ◽  
O. Özdarcan
Keyword(s):  
Light Curve ◽  
Active Component ◽  
Magnetic Activity ◽  
Curve Analysis ◽  
Light Curves ◽  
Close Binary ◽  
Physical Parameters ◽  
Light Curve Analysis ◽  
Low Mass ◽  
High Level

AbstractTaking into account results obtained from light-curve analysis and out-of-eclipse analyses, we discuss the nature of GSC 02038-00293 and also its magnetic activity behaviour.We obtained light curves of the system during observing seasons 2007, 2008 and 2011. We obtained its secondary minimum clearly in I-band observations in 2008 for the first time. Analysing this light curve, we found the physical parameters of the components. The light-curve analysis indicates that the possible mass ratio of the system is 0.35. We obtained the remaining V-band light curves, extracting the eclipses. We modelled these remaining curves using the SPOTMODEL program and found possible spot configurations of the magnetically active component for each observing season. The models demonstrated that there are two active longitudes for the active component. The models reveal that both active longitudes migrate in the direction of decreasing longitude. We also examined the light curves in out-of-eclipse phases with respect to minimum and maximum brightness, amplitude, etc. The amplitude of the curves during out-of-eclipse phases varies in a sinusoidal way with a period of ∼8.9 yr; the mean brightness of the system is dramatically decreasing. The phases of the deeper minimum during out-of-eclipse periods exhibit a migration toward decreasing phase.

scholarly journals Synthetic Light Curve Analysis of the Close Binary Systems BX Andromedae and RR Leporis

1989 ◽  
Vol 107 ◽  
pp. 359-360
Author(s):  
R.G. Samec ◽  
R.E. Fuller ◽  
R. H. Kaitchuck ◽  
B. B. Bookmyer ◽  
D. R. Faulkner
Keyword(s):  
Light Curve ◽  
Binary Systems ◽  
Thermal Relaxation ◽  
Curve Analysis ◽  
Light Curves ◽  
Close Binary ◽  
Comparison Star ◽  
Short Time Scale ◽  
Light Curve Analysis ◽  
Short Period

AbstractUnpublished photoelectric observations of the systems BX And and RR Lep were subjected to light curve analysis using the Wilson-Devinney Code.The short-period eclipsing binary system BX And was observed on five nights in 1976 at the Morgan-Monroe station of the Goethe Link Observatory of Indiana University. The observations covering the eclipse portions of the light curves yielded four times of minimum light. A period study covering 89 years of observations confirms that a major period change took place about 1950. The system is suspected of being quite active on a short time scale. Standard magnitudes were derived for BX And and for the comparison star. The corrected color indices indicate that BX And and the comparison star BD+39° 476 are in the spectral range of F3-F5. The light curves, defined by 1092 observations in B, 1097 in V and 971 in the U filter are symmetric. The difference in the eclipse depths are quite large averaging 0.m46. A distinct de-reddening of the light curves occurs during the secondary eclipse. The first synthetic light curve solutions of the system were obtained. The solution of BX And indicates that the system consists of an F-type primary and a K-type secondary component in a state of shallow contact. This result is supported by the location of BX And on the Eggen period-color diagram for contact binaries. The large mass ratio, temperature disparity and period increase are found to be consistent with an early contact phase of thermal relaxation oscillations.

scholarly journals Comparison of the power-2 limb-darkening law from the STAGGER-grid to Kepler light curves of transiting exoplanets

2018 ◽  
Vol 616 ◽  
pp. A39 ◽  
Author(s):  
P. F. L. Maxted
Keyword(s):  
Light Curve ◽  
Probability Distributions ◽  
Binary Star ◽  
Magnetic Activity ◽  
Light Curves ◽  
Practical Implementation ◽  
Light Curve Analysis ◽  
Stagger Grid ◽  
Least Squares Fit ◽  
Limb Darkening

Context. Inaccurate limb-darkening models can be a significant source of error in the analysis of the light curves for transiting exoplanet and eclipsing binary star systems, particularly for high-precision light curves at optical wavelengths. The power-2 limb-darkening law, Iλ(µ) = 1 − c(1−µα), has recently been proposed as a good compromise between complexity and precision in the treatment of limb-darkening. Aims. My aim is to develop a practical implementation of the power-2 limb-darkening law and to quantify the accuracy of this implementation. Methods. I have used synthetic spectra based on the 3D stellar atmosphere models from the STAGGER-grid to compute the limb-darkening for several passbands (UBVRI, CHEOPS, TESS, Kepler, etc.). The parameters of the power-2 limb-darkening laws are optimized using a least-squares fit to a simulated light curve computed directly from the tabulated Iλ(μ) values. I use the transformed parameters h1 = 1 − c(1 − 2−α) and h2 = c2−α to directly compare these optimized limb-darkening parameters to the limb darkening measured from Kepler light curves of 16 transiting exoplanet systems. Results. The posterior probability distributions (PPDs) of the transformed parameters h1 and h2 resulting from the light curve analysis are found to be much less strongly correlated than the PPDs for c and α. The agreement between the computed and observed values of (h1, h2) is generally very good but there are significant differences between the observed and computed values for Kepler-17, the only star in the sample that shows significant variability between the eclipses due to magnetic activity (star spots). Conclusions. The tabulation of h1 and h2 provided here can be used to accurately model the light curves of transiting exoplanets. I also provide estimates of the priors that should be applied to transformed parameters h1 and h2 based on my analysis of the Kepler light curves of 16 stars with transiting exoplanets.

scholarly journals PELICAN: deeP architecturE for the LIght Curve ANalysis

2019 ◽  
Vol 627 ◽  
pp. A21 ◽  
Author(s):  
Johanna Pasquet ◽  
Jérôme Pasquet ◽  
Marc Chaumont ◽  
Dominique Fouchez
Keyword(s):  
Light Curve ◽  
Sampling Rate ◽  
Real Data ◽  
Curve Analysis ◽  
Irregular Sampling ◽  
Light Curves ◽  
Light Curve Analysis ◽  
Deep Architecture ◽  
Deep Fields

We developed a deeP architecturE for the LIght Curve ANalysis (PELICAN) for the characterization and the classification of supernovae light curves. It takes light curves as input, without any additional features. PELICAN can deal with the sparsity and the irregular sampling of light curves. It is designed to remove the problem of non-representativeness between the training and test databases coming from the limitations of the spectroscopic follow-up. We applied our methodology on different supernovae light curve databases. First, we tested PELICAN on the Supernova Photometric Classification Challenge for which we obtained the best performance ever achieved with a non-representative training database, by reaching an accuracy of 0.811. Then we tested PELICAN on simulated light curves of the LSST Deep Fields for which PELICAN is able to detect 87.4% of supernovae Ia with a precision higher than 98%, by considering a non-representative training database of 2k light curves. PELICAN can be trained on light curves of LSST Deep Fields to classify light curves of the LSST main survey, which have a lower sampling rate and are more noisy. In this scenario, it reaches an accuracy of 96.5% with a training database of 2k light curves of the Deep Fields. This constitutes a pivotal result as type Ia supernovae candidates from the main survey might then be used to increase the statistics without additional spectroscopic follow-up. Finally we tested PELICAN on real data from the Sloan Digital Sky Survey. PELICAN reaches an accuracy of 86.8% with a training database composed of simulated data and a fraction of 10% of real data. The ability of PELICAN to deal with the different causes of non-representativeness between the training and test databases, and its robustness against survey properties and observational conditions, put it in the forefront of light curve classification tools for the LSST era.

scholarly journals Magnetic Activity of Two Similar Subgiants in Binaries with Very Different Mass Ratios: EI Eri and V711 Tau

2011 ◽  
Vol 7 (S282) ◽  
pp. 478-479 ◽  
Author(s):  
Katalin Oláh ◽  
Zsolt Kővári ◽  
Krisztián Vida ◽  
Klaus G. Strassmeier
Keyword(s):  
Differential Rotation ◽  
Activity Patterns ◽  
Magnetic Activity ◽  
Light Curves ◽  
Physical Parameters ◽  
Remarkable Difference ◽  
High Latitudes ◽  
Solar Type ◽  
Low Mass ◽  
Fast Rotating

AbstractWe use more than three decades-long photometry to study the activity patterns on the two fast-rotating subgiant components in EI Eri (G5IV) and V711 Tau (K1IV). From yearly mean rotational periods from the light curves, we find that EI Eri, with well-measured solar-type differential rotation, always has spots from the equator to high latitudes. The measured differential rotation of V711 Tau is controversial, and in any case is very small. The spots on the K1IV star in V711 Tau seem to be tidally locked. The physical parameters of the two systems are similar, with one remarkable difference: EI Eri has a low mass M4-5 dwarf companion, whereas V711 Tau has a G5V star in the system, thus their mass centers are in very different positions. This may modify the whole internal structure of the active stars, causing marked differences in their surface features.

scholarly journals Hydrogen and Helium Flashes in Cataclysmic Variables

1995 ◽  
Vol 151 ◽  
pp. 236-244
Author(s):  
Mariko Kato
Keyword(s):  
Star Formation ◽  
Chemical Composition ◽  
Neutron Star ◽  
Light Curve ◽  
Cataclysmic Variables ◽  
Curve Analysis ◽  
Light Curves ◽  
Light Curve Analysis ◽  
Formation Stage ◽  
Type Ia

AbstractLight curve analysis for the decay phase of novae gives estimates of the white dwaif mass, the luminosity (or distance) and the chemical composition of ejecta. Differences in these parameters among nova subclass, i.e. fast, slow and recurrent, are briefly summarized to speculate on their cause. Helium shell flashes occur in mass-increasing white dwarfs, their theoretical light curves are given in UV and visual wavelength bands. An evolutional scenario for fast, slow and recurrent, and slow novae through a helium nova/EUV source-stage toward a type Ia supernova/neutron star formation-stage is given.

Synthetic light curve analysis of the close binary systems BX Andromedae and RR Leporis

1989 ◽  
Vol 50 (1-2) ◽  
pp. 359-360
Author(s):  
R.G. Samec ◽  
R.E. Fuller ◽  
R.H. Kaitchuck ◽  
B.B. Bookmyer ◽  
D.R. Faulkner
Keyword(s):  
Light Curve ◽  
Binary Systems ◽  
Curve Analysis ◽  
Close Binary ◽  
Light Curve Analysis ◽  
Close Binary Systems

Synthetic Light Curve Analysis of the Close Binary Systems BX Andromedae and RR Leporis

Algols ◽  
1989 ◽  
pp. 359-360
Author(s):  
R. G. Samec ◽  
R. E. Fuller ◽  
R. H. Kaitchuck ◽  
B. B. Bookmyer ◽  
D. R. Faulkner
Keyword(s):  
Light Curve ◽  
Binary Systems ◽  
Curve Analysis ◽  
Close Binary ◽  
Light Curve Analysis ◽  
Close Binary Systems

scholarly journals Frequency analysis of multiperiodic δ Scuti stars

1993 ◽  
Vol 139 ◽  
pp. 149-149 ◽  
Author(s):  
L. Mantegazza ◽  
E. Poretti ◽  
F.M. Zerbi
Keyword(s):  
Light Curve ◽  
Frequency Analysis ◽  
Curve Analysis ◽  
Light Curves ◽  
Light Curve Analysis ◽  
Preliminary Results ◽  
Long Time ◽  
Scuti Star ◽  
Scuti Stars ◽  
Δ Scuti Stars

We report some of the recent results of our studies on δ Scuti star pulsation which are based on observations made at Merate and La Silla Observatories, sometimes in two site campaigns. Our recent experiences on X Caeli and 44 Tauri have shown that quite complicate light curves can be resolved even with observations obtained from one site only, if compact and accurate datasets are collected on sufficiently long time baselines (Mantegazza and Poretti, 1992; Poretti et al., 1992). Here we report the preliminary results of the light curve analysis of three more stars surveyed for more than 120 hours each: BI CMi, HD 18878 and HD 224639.BI CMi has been observed in a two-site campaign in January-February 1991, the observations being collected during 17 nights. The frequency analysis of the light curve allowed us to identify unambiguously 4 pulsation modes at 8.247, 8.863, 8.514 and 7.424 c/d with semi-amplitudes of 22, 19, 5 and 5 mmag respectively.

scholarly journals Light Curve Analysis of Rotating Variable Stars

1986 ◽  
Vol 90 ◽  
pp. 171-174
Author(s):  
A. Hempelmann ◽  
W. Schöneich
Keyword(s):  
Light Curve ◽  
Variable Stars ◽  
Short Description ◽  
Curve Analysis ◽  
Light Curves ◽  
Light Curve Analysis

AbstractA short description of a method for analysing light curves of rotating variable stars is given. This method is applied to light curves of HD 24712.

scholarly journals The nature of V861 Sco (=HD 152667)

1981 ◽  
Vol 59 ◽  
pp. 481-486
Author(s):  
Ian D. Howarth ◽  
R. Wilson
Keyword(s):  
Light Curve ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Curve Analysis ◽  
Physical Parameters ◽  
Evolutionary Models ◽  
Light Curve Analysis ◽  
Phase Dependence ◽  
Large Phase ◽  
Good Agreement

AbstractThe physical parameters of the components of V861 Sco are derived from light-curve analysis and published spectroscopy. Good agreement with evolutionary models is obtained. The stellar wind is investigated using IUE data; the results include no large phase dependence of the mass loss rate and insensitivity of the velocity of the wind (measured with respect to interstellar lines) to changes in the photospheric velocity, even near the base of the wind. However, small random changes in velocity near the base of the wind are amplified to larger changes further out.

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