scholarly journals CHROMOSPHERIC ACTIVITY NATURE OF KIC 6044064

2021 ◽  
Vol 57 (2) ◽  
pp. 351-361
Author(s):  
E. Yoldaş
Keyword(s):  
Primary Component ◽  
Secondary Component ◽  
Migration Period ◽  
Chromospheric Activity ◽  
Spot Group ◽  
Kepler Mission ◽  
Phase Interval

This study presents results obtained from the data of KIC 6044064 (KOI 6652). KIC 6044064 was observed by the Kepler Mission for a total of 1384.254 days. 525 minima times were determined, 264 of which were primary minima and the rest were secondary minima. The OPEA model was derived and its parameters were obtained. On the secondary component, there are two different spot bands latitudinally outstretched, consisting of three spots located with a phase interval of 0.33. The average migration period was found to be 623.063±4.870 days (1.71±0.01 years) for the first spot group, while it was 1125.514±7.305 days (3.08±0.02 years) for the second group. The spectral types of the components seem to be G7V+K9V. Their masses and radii were determined to be 0.86Mʘ and 0.89Rʘ for the primary component and 0.54Mʘ and 0.62Rʘ for the secondary component.

scholarly journals Detailed Chromospheric Activity Nature of KIC 9641031

2016 ◽  
Vol 33 ◽  
Author(s):  
Ezgi Yoldaş ◽  
Hasan Ali Dal
Keyword(s):  
Active Component ◽  
Active Regions ◽  
Activity Level ◽  
Light Curves ◽  
Chromospheric Activity ◽  
Rotational Modulation ◽  
Kepler Mission ◽  
Period Variations ◽  
Analytic Models ◽  
Flare Frequency

AbstractThis study depends on KIC 9641031 eclipsing binary with a chromospherically active component. There are three type variations, such as geometrical variations due to eclipses, sinusoidal variations due to the rotational modulations, and also flares, in the light curves. Taking into account results obtained from observations in the Kepler Mission Database, we discuss the details of chromospheric activity. The sinusoidal light variations due to rotational modulation and the flare events were modelled. 92 different data subsets separated using the analytic models were modelled separately to obtain the cool spot configuration. Acording to the model, there are two active regions separated by about 180° longitudinally between the latitudes of +50° and +100°. 240 flares, whose parameters were computed, were detected. Using these parameters, the OPEA model was derived, in which the Plateau value was found to be 1.232±0.069 s, and half-life parameter was found as 2291.7 s. The flare frequency N1 was found as 0.41632 h−1, while the flare frequency N2 was found as 0.00027. Considering these parameters together with the orbital period variations demonstrates that the period variations depend on chromospheric activity. Comparing the system with its analogue, the activity level of KIC 9641031 is remarkably lower than the others.

scholarly journals KOI-256’s Magnetic Activity Under the Influence of the White Dwarf

2017 ◽  
Vol 34 ◽  
Author(s):  
Ezgi Yoldaş ◽  
Hasan Ali Dal
Keyword(s):  
White Dwarf ◽  
Active Component ◽  
Active Regions ◽  
Magnetic Activity ◽  
Activity Level ◽  
Logarithmic Scale ◽  
Flare Activity ◽  
Migration Period ◽  
Kepler Mission ◽  
Spot Activity

AbstractWe present the findings about chromospheric activity nature of KOI-256 obtained from the Kepler Mission data. First, it was found that there are some sinusoidal variations out-of-eclipses due to cool spot activity. The sinusoidal variations modelled by the spotmodel program indicate that the active component has two different active regions. Their longitudinal variation revealed that one of them has a migration period of 3.95 yrs, while the other has a migration period of 8.37 yrs. Second, 225 flares were detected from the short cadence data in total. The parameters, such as increase (Tr) and decay (Td) times, total flare time (Tt), equivalent durations (P), were calculated for each flare. The distribution of equivalent durations versus total flare times in logarithmic scale is modelled to find flare activity level. The Plateau value known as the saturation level of the active component was calculated to be 2.3121 ± 0.0964 s, and the Half-life value, which is required flare total time to reach the saturation, was computed to be 2233.6 s. In addition, the frequency of N1, which is the number of flares per an hour in the system, was found to be 0.05087 h−1, while the flare frequency N2 that the flare-equivalent duration emitting per an hour was found to be 0.00051. Contrary to the spot activity, it has been found that the flares are in tends to appear at specific phases due to the white dwarf component.

scholarly journals Theoretical study of irradiation effects in close binaries

2009 ◽  
pp. 49-56 ◽  
Author(s):  
Rao Srinivasa ◽  
B.A. Varghese
Keyword(s):  
Radiation Field ◽  
Close Binary System ◽  
Primary Component ◽  
Secondary Component ◽  
Close Binary ◽  
Close Binaries ◽  
Irradiation Effects ◽  
3 Dimensional ◽  
Cartesian Coordinate ◽  
Coordinate Geometry

The effect of irradiation is studied in a close binary system assuming that the secondary component is a point source, moving in a circular orbit. The irradiation effects are calculated on the atmosphere of the primary component in a 3-dimensional Cartesian coordinate geometry. In treating the reflection effect theoretically, the total radiation (ST) is obtained as the sum of the radiation of 1) the effect of irradiation on the primary component which is calculated by using one dimensional rod model (Sr) and 2) the self radiation of the primary component which is calculated by using the solution of radiative transfer equation in spherical symmetry (Ss). The radiation field is estimated along the line of sight of the observer at infinity. It is shown how the radiation field changes depending on the position of the secondary component.

scholarly journals KIC 7385478: An Eclipsing Binary with a γ Doradus Component

2017 ◽  
Vol 34 ◽  
Author(s):  
Orkun Özdarcan ◽  
Hasan Ali Dal
Keyword(s):  
Light Curve ◽  
Orbital Period ◽  
Spectroscopic Data ◽  
Primary Component ◽  
Secondary Component ◽  
Photometric Analysis ◽  
Eclipsing Binary ◽  
Cool Star ◽  
Star Activity ◽  
Dominant Period

AbstractWe present spectroscopic and photometric analysis of the eclipsing binary KIC 7385478. We find that the system is formed by F1V + K4III–IV components. Combining results from analysis of spectroscopic data and Kepler photometry, we calculate masses and radii of the primary and the secondary components as M1 = 1.71 ± 0.08 M⊙, M2 = 0.37 ± 0.04 M⊙ and R1 = 1.59 ± 0.03 R⊙, R2 = 1.90 ± 0.03 R⊙, respectively. Position of the primary component in HR diagram is in the region of γ Doradus type pulsators and residuals from light curve modelling exhibit additional light variation with a dominant period of ~ 0.5 d. These are clear evidences of the γ Doradus type pulsations on the primary component. We also observe occasional increase in amplitude of the residuals, where the orbital period becomes the most dominant period. These may be attributed to the cool star activity originating from the secondary component.

scholarly journals Palaeomagnetic results from late Cretaceous and early Tertiary limestones from Tingri area, southern Tibet, China

1998 ◽  
Vol 18 ◽  
Author(s):  
E. Appel ◽  
H. Li ◽  
A. Patzelt ◽  
J. Wang
Keyword(s):  
Late Cretaceous ◽  
Primary Component ◽  
Field Direction ◽  
Secondary Component ◽  
Reverse Polarity ◽  
Southern Tibet ◽  
Early Tertiary ◽  
Primary Direction ◽  
Stratigraphic Succession ◽  
Tethyan Himalaya

Palaeomagnetic studies have been carried out on the late Campanian (Zhepure Shanbei Formation: ZSbF), early Palaeocene (Zbepure Shanpo Formation: ZSpF) and early to mid-Eocene (Zhepure Shan Formation, memberV: ZSFmV) limestones from the Tethyan Himalaya west of Tingri (28°48'N, 86°54'E) in southern Tibet (China). A primary component in the ZSbF is proven by normal and reverse polarity zones in a stratigraphic succession of uniform layers (1 site, 24 specimens). The inclination (-50.2°) approximately fits to the expected palaeolatitude of the area for late Campanian. However, this result bas to be considered with caution because of non-antipodal remanence directions. The ZSpF shows a recent field direction only and is affected by gyroremanence acquisition. In contrast to results published earlier by Besse et al. (1984), no primary component could be identified in the ZSFmV. The characteristic remanence (ChRM) isolated in this unit (5 sites, 32 specimens) is most likely of secondary origin. The significance of the fold test is below the 95% level due to rather uniform bedding attitudes, but tilt corrected inclinations are unrealistically high for the area. The polarity of the ChRM is reverse and thus represents a palaeoremanence acquired sometimes between the Brunbes/Matuyama boundary and Eocene times. Declinations of Besse et al. (1984)'s primary direction and of our secondary component in the ZSFmV coincide and suggest that no rotation of the Tingri area occurred between Eocene and the time where the remanence was acquired.

scholarly journals Is ξ Boo AB a Young or an Evolved System? A Model Atmosphere Analysis

1991 ◽  
Vol 130 ◽  
pp. 446-448
Author(s):  
I.S. Savanov
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Rotation Rate ◽  
Main Sequence ◽  
Rotational Velocity ◽  
Model Atmosphere ◽  
Secondary Component ◽  
The Sun ◽  
Chromospheric Activity ◽  
System A

AbstractWe perform a model atmosphere analysis of ξ Boo A, and make estimates for the secondary component. The abundances of 25 elements for ξ Boo A are obtained with the parameters: Teff=(5300 ± 100) K, log g= 4.1 ± 0.2, ξt = 0.5km/s. The atmosphere of ξ Boo A is deficient in Y and Zr, but overabundant in Ba and rare earth elements. We confirm the high Li abundance in ξBoo A (logA(Li) = 2.1), while Li is strongly underabundant in the secondary relative to the Sun. From comparison with evolutionary calculations we find that ξ Boo A has mass 0.95 M⊙, radius 1.4 R⊙ we also determine a rotational velocity v sin i = 8 km/s. We conclude that, in spite of its relatively high rotation rate and high chromospheric activity, it is already evolved from the main-sequence.

scholarly journals KIC 8553788: A pulsating Algol with an extreme mass ratio

2018 ◽  
Vol 616 ◽  
pp. A130 ◽  
Author(s):  
A. Liakos
Keyword(s):  
Radial Velocity ◽  
Spectral Type ◽  
Primary Component ◽  
Photometric Data ◽  
Light Curves ◽  
Secondary Component ◽  
Mass Ratio ◽  
Eclipsing Binary ◽  
Detached Binaries ◽  
Absolute Parameters

Context. The present research paper focuses on the eclipsing binary KIC 8553788 which belongs to two different types of binary systems regarding its physical properties. In particular, it is one of the 71 oscillating stars of Algol-type that have been discovered so far and one of the six that have been published based on high-cadence photometric data of the Kepler mission. In addition, it is one of the four semi-detached binaries of the group of R CMa-type systems, while its pulsating component has the fourth fastest frequency among the δ Scuti stars-members of semi-detached binaries. Detailed light curves as well as spectroscopic and pulsation analyses are presented, while possible explanation scenarios for the evolution of the system involving past mass transfer, mass loss, and/or angular momentum loss due to the presence of a tertiary component are discussed. Aims. The goal of the study is to extract the pulsational characteristics of the oscillating star of the system, to estimate the absolute parameters of its components, and to provide a possible explanation for its extreme evolutionary status. Methods. Ground-based spectroscopic observations using the 2.3 m “Aristarchos” telescope were obtained and used for the estimation of the spectral type of the primary component and to model the light curves of the system with higher certainty. The short-cadence photometric data provided by the Kepler mission were analysed using standard eclipsing binary modelling techniques, while Fourier analysis was applied on their residuals aiming to reveal the properties of the intrinsic oscillations. The resulting photometric model was combined with a published radial velocity curve to obtain accurate absolute parameters for the components of the system. Results. The results show that the primary component of the system is of A8 spectral type, has a mass of 1.6 M⊙, and a radius of 2 R⊙. It is a relatively fast pulsator of δ Scuti type that oscillates in 89 frequency modes with the dominant one being 58.26 cycles day−1. On the other hand, the secondary component has a mass of only 0.07 M⊙, a radius of 1 R⊙, and a temperature of 4400 K. In addition, it was found to be magnetically active with migrating cool spots on its surface. Conclusions. KIC 8553788, according to its geometrical configuration and its pulsational properties, belongs to the group of oscillating stars of Algol type, while according to its very low mass ratio and its relatively short orbital period belongs also to the group of R CMa stars. If confirmed by radial velocity data of the secondary component, the system would have the lowest mass ratio that has ever been found in semi-detached systems and could therefore be considered as one of the most extreme cases.

scholarly journals Possible Magnetic Activity Cycles of Four Chromospherically Active Binaries: ER Vul, UV Psc, AR Lac and BH Vir

2001 ◽  
Vol 203 ◽  
pp. 437-440 ◽  
Author(s):  
S. B. Qian
Keyword(s):  
Orbital Period ◽  
Magnetic Activity ◽  
Primary Component ◽  
The Other ◽  
Period Variation ◽  
Periodic Component ◽  
Secondary Component ◽  
Close Binaries ◽  
Activity Cycles ◽  
Orbital Periods

The study of a possible connection between magnetic activity and orbital period variation in close binaries is a very interesting work. Recently, the orbital periods of four chromospherically active binaries, ER Vul, UV Psc, AR Lac and BH Vir, are analyzed. It is discovered that the orbital periods of UV Psc and BH Vir oscillate with periods of 61 and 9.12 years, and the orbital periods of ER Vul and AR Lac show periodic variations with periods of 31 and 47 years respectively while they undergo secular decrease. The mechanisms that could explain the changes in the orbital periods of the four systems have been studied. The period variation of UV Psc may be caused by the cyclical magnetic activity in the primary component, and the magnetic activity in secondary component of AR Lac can explain its periodic component in the orbital period changes. For the other two systems, BH Vir and ER Vul, the cyclical magnetic activity in one or both of the components can explain the cyclical orbital period changes of BH Vir and the periodic component in the changes of the orbital period of ER Vul. These results suggest that the periods of the orbital period oscillations in the four systems may be the magnetic activity cycles.

scholarly journals TESS photometry of the eclipsing δ Scuti star AI Hydrae

2020 ◽  
Vol 72 (3) ◽  
Author(s):  
Jae Woo Lee ◽  
Kyeongsoo Hong ◽  
Martti H Kristiansen
Keyword(s):  
Binary Star ◽  
Primary Component ◽  
Secondary Component ◽  
Apsidal Motion ◽  
Star Model ◽  
Eclipsing Binary ◽  
Timing Diagram ◽  
Low Degree ◽  
Scuti Star ◽  
Good Agreement

Abstract AI Hya has been known as an eclipsing binary with a monoperiodic $\delta$ Sct pulsator. We present the results from its TESS (Transiting Exoplanet Survey Satellite) photometry observed during Sector 7. Including our five minimum epochs, the eclipse timing diagram displays the apsidal motion with a rate of $\dot{\omega } = 0.075 \pm 0.031\:$deg$\:$yr$^{-1}$, which corresponds to an apsidal period of $U = 4800\pm 2000\:$yr. The binary star model represents that the smaller, less massive primary component is $427\:$K hotter than the pulsating secondary, and our distance of $612\pm 36\:$pc is in good agreement with the Gaia distance of $644\pm 26\:$pc. We subtracted the binary effects from the observed TESS data and applied a multifrequency analysis to these residuals. The result reveals that AI Hya is multiperiodic in its pulsation. Of 14 signals detected, four ($f_1$, $f_2$, $f_3$, $f_6$) may be considered independent pulsation frequencies. The period ratios of $P_{\rm pul}/P_{\rm orb} = 0.012$–0.021 and the pulsation constants of $Q = 0.30$–0.52 d correspond to $\delta$ Sct pulsations in binaries. We found that the secondary component of AI Hya pulsates in both radial fundamental $F$ modes ($f_2$ and $f_3$) and non-radial $g_1$ modes with a low degree of $\ell = 2$ ($f_1$ and $f_6$).

Chromospheric activity as a function of age in main-sequence stars

1966 ◽  
Vol 24 ◽  
pp. 40-43
Author(s):  
O. C. Wilson ◽  
A. Skumanich
Keyword(s):  
Main Sequence ◽  
The Sun ◽  
Main Sequence Stars ◽  
Tentative Conclusion ◽  
Chromospheric Activity ◽  
General Field ◽  
Large Clusters

Evidence previously presented by one of the authors (1) suggests strongly that chromospheric activity decreases with age in main sequence stars. This tentative conclusion rests principally upon a comparison of the members of large clusters (Hyades, Praesepe, Pleiades) with non-cluster objects in the general field, including the Sun. It is at least conceivable, however, that cluster and non-cluster stars might differ in some fundamental fashion which could influence the degree of chromospheric activity, and that the observed differences in chromospheric activity would then be attributable to the circumstances of stellar origin rather than to age.

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