scholarly journals Absolute properties of RU Cnc revisited: an active RS CVn-type eclipsing binary with red giant branch and main-sequence components

2019 ◽  
Vol 488 (4) ◽  
pp. 4520-4525 ◽  
Author(s):  
K A Çokluk ◽  
D Koçak ◽  
T İçli ◽  
S Karaköse ◽  
S Üstündağ ◽  
...  
Keyword(s):  
Main Sequence ◽  
Variation Analysis ◽  
High Quality ◽  
Eclipsing Binary ◽  
Data Release ◽  
Sequence Components ◽  
Red Giant ◽  
Period Decrease ◽  
The Masses

ABSTRACT We present observations and analysis of an RS CVn-type double-lined eclipsing binary system, RU Cnc. The system has been observed for over a century. High-quality long-cadence observations, newly obtained from the Kepler K2 C5 and C18 campaigns, and two radial velocity curves were combined and analysed simultaneously, assuming a multispot model. The masses, radii and luminosities of the component stars have been precisely obtained as $M_\textrm{c} = 1.386\pm 0.044\, \mathrm{M}_{\odot }$, $M_\textrm{h} = 1.437 \pm 0.046\, \mathrm{M}_{\odot }$, $R_\textrm{h} = 2.39\pm 0.07\, \mathrm{R}_{\odot }$, $R_\textrm{c} = 5.02 \pm 0.08\, \mathrm{R}_{\odot }$, $L_\textrm{h} = 11.4\pm 1.2\, \mathrm{L}_{\odot }$ and$L_\textrm{c} = 12.0 \pm 1.0\, \mathrm{L}_{\odot }$, with a separation of $a = 27.914 \pm 0.016\, \mathrm{R}_{\odot }$. The distance of the system is determined to be $380\pm 57\,$ pc, which is consistent with the Gaia Data Release 2 result. Long-term detailed period variation analysis of the system indicates a period decrease of 7.9 × 10−7 d yr–1. The results suggest that the cooler component is on the red giant branch (RGB) and the hotter component is still on the main sequence.

Astrometry and Spectroscopy as Tools Toward Visual-Binary Masses

1992 ◽  
Vol 135 ◽  
pp. 273-275
Author(s):  
W.D. Heintz
Keyword(s):  
High Precision ◽  
Main Sequence ◽  
Mass Determination ◽  
Orbital Elements ◽  
High Quality ◽  
Visual Binary ◽  
Mass Ratios ◽  
The Status ◽  
Sequence Components

Following the diversified topic of this conference, let me present a variety of comments — not all new, but resulting from a long string of stars drifting across the desk. The chase after visual orbital elements is not exactly a self-purpose but is aiming at further data, in particular, at good masses. The last published lists of high-quality mass determination represent the status of 20 years ago; but a compilation at this time would probably not last long as the progress promises to quicken.We have 1000 positional (visual/photographic/speckle) orbits, among them about 700 acceptable in the range from fair to definitive. Yet less than 10% of them give good component masses. Most of them are outside the range of parallax measures with the requisite, high precision (that unfortunatly holds for the Hyades); some frustrate the parallax measurer by displaying wedge– and peanut–shaped images, and the more exciting cases of abnormal, non-main–sequence components often cannot get good mass ratios owing to large distances or long periods.

scholarly journals Eclipsing binary stars as tests of stellar evolutionary models and stellar ages

2008 ◽  
Vol 4 (S258) ◽  
pp. 161-170 ◽  
Author(s):  
Keivan G. Stassun ◽  
Leslie Hebb ◽  
Mercedes López-Morales ◽  
Andrej Prša
Keyword(s):  
Binary Stars ◽  
Main Sequence ◽  
Magnetic Activity ◽  
Eclipsing Binaries ◽  
Evolutionary Models ◽  
Main Sequence Stars ◽  
Eclipsing Binary ◽  
Eclipsing Binary Stars ◽  
Sequence Components ◽  
Low Mass

AbstractEclipsing binary stars provide highly accurate measurements of the fundamental physical properties of stars. They therefore serve as stringent tests of the predictions of evolutionary models upon which most stellar age determinations are based. Models generally perform very well in predicting coeval ages for eclipsing binaries with main-sequence components more massive than ≈1.2 M⊙; relative ages are good to ~5% or better in this mass regime. Low-mass main-sequence stars (M < 0.8 M⊙) reveal large discrepancies in the model predicted ages, primarily due to magnetic activity in the observed stars that appears to inhibit convection and likely causes the radii to be 10–20% larger than predicted. In mass-radius diagrams these stars thus appear 50–90% older or younger than they really are. Aside from these activity-related effects, low-mass pre–main-sequence stars at ages ~1 Myr can also show non-coevality of ~30% due to star formation effects, however these effects are largely erased after ~10 Myr.

scholarly journals Properties of the Hyades, the eclipsing binary HD 27130, and the oscillating red giant ϵ Tauri

2020 ◽  
Vol 645 ◽  
pp. A25
Author(s):  
K. Brogaard ◽  
E. Pakštienė ◽  
F. Grundahl ◽  
Š. Mikolaitis ◽  
G. Tautvaišienė ◽  
...  
Keyword(s):  
Binary Stars ◽  
Giant Star ◽  
Eclipsing Binary ◽  
Helium Content ◽  
Additional Information ◽  
Red Giant ◽  
Model Dependency ◽  
The Masses ◽  
Cluster Age ◽  
Age Estimates

Context. The derivation of accurate and precise masses and radii is possible for eclipsing binary stars, allowing for insights into their evolution. When residing in star clusters, they provide measurements of even greater precision, along with additional information on their properties. Asteroseismic investigations of solar-like oscillations offers similar possibilities for single stars. Aims. We wish to improve the previously established properties of the Hyades eclipsing binary HD 27130 and re-assess the asteroseismic properties of the giant star ϵ Tau. The physical properties of these members of the Hyades can be used to constrain the helium content and age of the cluster. Methods. New multi-colour light curves were combined with multi-epoch radial velocities to yield masses and radii of HD 27130. Measurements of Teff were derived from spectroscopy and photometry, and verified using the Gaia parallax. We estimated the cluster age from re-evaluated asteroseismic properties of ϵ Tau while using HD 27130 to constrain the helium content. Results. The masses, radii, and Teff of HD 27130 were found to be M = 1.0245  ±  0.0024 M⊙, R = 0.9226  ±  0.015 R⊙, Teff = 5650  ±  50 K for the primary, and M = 0.7426  ±  0.0016 M⊙, R = 0.7388  ±  0.026 R⊙, Teff = 4300  ±  100 K for the secondary component. Our re-evaluation of ϵ Tau suggests that the previous literature estimates are trustworthy and that the HIPPARCOS parallax is more reliable than the Gaia DR2 parallax. Conclusions. The helium content of HD 27130 and, thus, of the Hyades is found to be Y = 0.27 but with a significant model dependency. Correlations with the adopted metallicity result in a robust helium enrichment law, with ΔY/ΔZ close to 1.2 We estimate the age of the Hyades to be 0.9 ± 0.1 (stat) ±0.1 (sys) Gyr, which is in slight tension with recent age estimates based on the cluster white dwarfs. The precision of the age estimate can be much improved via asteroseismic investigations of the other Hyades giants and by future improvements to the Gaia parallax for bright stars.

KIC 5359678: A detached eclipsing binary with starspots

2021 ◽  
Author(s):  
Jiaxin Wang ◽  
Jianning Fu ◽  
Hubiao Niu ◽  
Yang Pan ◽  
Chunqian Li ◽  
...  
Keyword(s):  
Main Sequence ◽  
Function Analysis ◽  
Light Curves ◽  
Main Sequence Stars ◽  
Period Range ◽  
Eclipsing Binary ◽  
A Value ◽  
Auto Correlation ◽  
Auto Correlation Function ◽  
The Masses

Abstract We study the detached eclipsing binary, KIC 5359678, with starspot modulation using the high-quality Kepler photometry and LAMOST spectroscopy. The PHOEBE model, optimal for this binary, reveals that this system is a circular detached binary, composed of two F-type main-sequence stars. The masses and radii of the primary and the secondary are M1 = 1.31 ± 0.05M⊙, R1 = 1.52 ± 0.04R⊙, M2 = 1.12 ± 0.04M⊙, and R2 = 1.05 ± 0.06R⊙, respectively. The age of this binary is estimated to be about 2Gyr, a value much longer than the synchronization timescale of 17.8 Myr. The residuals of light curves show quasi-sinusoidal signals, which could be induced by starspots. We apply auto-correlation function analysis on the out-of-eclipse residuals and find that the spot with rotational period close to the orbital period, while, the decay timescale of starspots is longer than that on the single stars with the same temperature, period range, and rms scatter. A two-starspot model is adopted to fit the signals with two-dip pattern, whose result shows that the longitude decreases with time.

scholarly journals WASP 0639-32: a new F-type subgiant/K-type main-sequence detached eclipsing binary from the WASP project

2018 ◽  
Vol 615 ◽  
pp. A135 ◽  
Author(s):  
J. A. Kirkby-Kent ◽  
P. F. L. Maxted ◽  
A. M. Serenelli ◽  
D. R. Anderson ◽  
C. Hellier ◽  
...  
Keyword(s):  
Binary System ◽  
Main Sequence ◽  
Mass Density ◽  
Helium Abundance ◽  
Eclipsing Binary ◽  
Abundance Estimate ◽  
Secondary Star ◽  
Free Parameters ◽  
Effective Temperatures ◽  
The Masses

Aims. Our aim is to measure the masses and radii of the stars in a newly-discovered detached eclipsing binary system to a high precision (≈1%), enabling the system to be used for the calibration of free parameters in stellar evolutionary models. Methods. Photometry from the Wide Angle Search for Planets (WASP) project was used to identify 1SWASP J063930.33-322404.8 (TYC 7091-888-1, WASP 0369-32 hereafter) as a detached eclipsing binary system with total eclipses and an orbital period of P = 11.66 days. Lightcurve parameters for WASP 0639-32 are obtained using the EBOP lightcurve model, with standard errors evaluated using a prayer-bead algorithm. Radial velocities were measured from 11 high-resolution spectra using a broadening function approach, and an orbit was fitted using SBOP. Observed spectra were disentangled and an equivalent width fitting method was used to obtain effective temperatures and metallicities for both stars. A Bayesian framework is used to explore a grid of stellar evolution models, where both helium abundance and mixing length are free to vary, and use observed parameters (mass, density, temperature, and metallicity) for each star to obtain the age and constrain the helium abundance of the system. Results. The masses and radii are found to be M1 = 1.1544 ± 0.0043 M⊙, R1 = 1.833 ± 0.023 R⊙, and M2 = 0.7833 ± 0.0028 M⊙, R2 = 0.7286 ± 0.0081 R⊙ for the primary and secondary, respectively. The effective temperatures were found to be T1 = 6330 ± 50 K and T2 = 5400 ± 80 K for the primary and secondary star, respectively. The system has an age of 4.2−0.1+0.8 Gyr, and a helium abundance in the range 0.251–0.271. Conclusions. WASP 0639-32 is a rare example of a well-characterised detached eclipsing binary system containing a star near the main-sequence turn-off point. This makes it possible to measure a precise age for the stars in this binary system and to estimate their helium abundance. Further work is needed to explore how this helium abundance estimate depends on other free parameters in the stellar models.

scholarly journals Significant uncertainties from calibrating overshooting with eclipsing binary systems

2018 ◽  
Vol 618 ◽  
pp. A177 ◽  
Author(s):  
Thomas Constantino ◽  
Isabelle Baraffe
Keyword(s):  
Stellar Evolution ◽  
Binary Stars ◽  
Binary Systems ◽  
Precise Measurement ◽  
Main Sequence ◽  
Stellar Mass ◽  
Main Sequence Stars ◽  
Eclipsing Binary ◽  
The Masses ◽  
Convective Boundaries

The precise measurement of the masses and radii of stars in eclipsing binary systems provides a window into uncertain processes in stellar evolution, especially mixing at convective boundaries. Recently, these data have been used to calibrate models of convective overshooting in the cores of main sequence stars. In this study we have used a small representative sample of eclipsing binary stars with 1.25 ≤ M/M⊙ < 4.2 to test how precisely this method can constrain the overshooting and whether the data support a universal stellar mass–overshooting relation. We do not recover the previously reported stellar mass dependence for the extent of overshooting and in each case we find there is a substantial amount of uncertainty, that is, the same binary pair can be matched by models with different amounts of overshooting. Models with a moderate overshooting parameter 0.013 ≤ fos ≤ 0.014 (using the scheme from Herwig et al. 1997, A&A, 324, L81) are consistent with all eight systems studied. Generally, a much larger range of f is suitable for individual systems. In the case of main sequence and early post-main sequence stars, large changes in the amount of overshooting have little effect on the radius and effective temperature, and therefore the method is of extremely limited utility.

scholarly journals HD 46407: The First Eclipsing-Binary Barium Star

1992 ◽  
Vol 151 ◽  
pp. 411-414
Author(s):  
A. Jorissen ◽  
J. Manfroid ◽  
C. Sterken
Keyword(s):  
Orbital Period ◽  
High Accuracy ◽  
Dust Particles ◽  
Eclipsing Binary ◽  
Wide Ring ◽  
Red Giant

A long-term, high-accuracy, differential uvby monitoring of a sample of 19 barium stars revealed that HD 46407, a well known barium star with an orbital period of 458 d, is an eclipsing binary. The eclipse (of the companion by the barium star) was most clearly seen in November 1988, when a dip of 0.02 mag (in y) having a FWHM of about 10 d was recorded in the lightcurve. Confirmation of the eclipsing nature of HD 46407 was also obtained in February 1985 and in February 1990. A shallow secondary eclipse (extending over about 50% of the orbital period) seems to be present as well. The b – y index is marginally variable, while v – b color variations are correlated with the y variations, in the sense that the system appears redder when it is fainter. We suggest that these variations originate in the scattering of the red-giant light by dust particles trapped (in a wide ring or shell?) around the (compact) companion. The eclipsed light would then be the light of the red giant backscattered by the dust around the companion.

ANALYSIS OF ABDOMINAL TYPHOID INCIDENCE IN THE SOUTH REGION OF THE KYRGYZ REPUBLIC

2020 ◽  
pp. 43-48
Author(s):  
Zakirova J.S. ◽  
Nadirbekova R.A. ◽  
Zholdoshev S.T.
Keyword(s):  
Drinking Water ◽  
Typhoid Fever ◽  
Risk Groups ◽  
The Body ◽  
Kyrgyz Republic ◽  
Radiation Factor ◽  
High Quality ◽  
Two Generations ◽  
Immunological Deficiency

The article analyze the long-term morbidity, spread of typhoid fever in the southern regions of the Kyrgyz republic, and remains a permanent epidemic focus in the Jalal-Abad region, where against the low availability of the population to high-quality drinking water, an additional factor on the body for more than two generations and radiation factor, which we confirmed by the spread among the inhabitants of Mailuu-Suu of nosological forms of the syndrome of immunological deficiency, as a predictor of risk groups for infectious diseases, including typhoid fever.

One-step synthesis of high-quality vanadium disulfide quantum dots for long-term lysosome-targetable imaging

2021 ◽  
pp. 130544
Author(s):  
Dan Yang ◽  
Liwen Chen ◽  
Le Wang ◽  
Zhongjie Cui ◽  
Zhuoqi Wen ◽  
...  
Keyword(s):  
Quantum Dots ◽  
High Quality ◽  
One Step

scholarly journals Lyell, the Geikies and Croll's observations on terrestrial glacial sediments and landforms

2021 ◽  
pp. 1-14
Author(s):  
James ROSE
Keyword(s):  
Climate Change ◽  
High Quality ◽  
Glacial Sediments ◽  
Direct Observations ◽  
The Social ◽  
The Status ◽  
Social And Physical Environment ◽  
Glacial Landforms

ABSTRACT Within the context of the work and achievements of James Croll, this paper reviews the records of direct observations of glacial landforms and sediments made by Charles Lyell, Archibald and James Geikie and James Croll himself, in order to evaluate their contributions to the sciences of glacial geology and Quaternary environmental change. The paper outlines the social and physical environment of Croll's youth and contrasts this with the status and experiences of Lyell and the Geikies. It also outlines the character and role of the ‘Glasgow School’ of geologists, who stimulated Croll's interest into the causes of climate change and directed his focus to the glacial and ‘interglacial’ deposits of central Scotland. Contributions are outlined in chronological order, drawing attention to: (i) Lyell's high-quality observations and interpretations of glacial features in Glen Clova and Strathmore and his subsequent rejection of the glacial theory in favour of processes attributed to floating icebergs; (ii) the significant impact of Archibald Geikie's 1863 paper on the ‘glacial drift of Scotland’, which firmly established the land-ice theory; (iii) the fact that, despite James Croll's inherent dislike of geology and fieldwork, he provided high-quality descriptions and interpretations of the landforms and sediments of central Scotland in order to test his theory of climate change; and (iv) the great communication skills of James Geikie, enhanced by contacts and evidence from around the world. It is concluded that whilst direct observations of glacial landforms and sediments were critical to the long-term development of the study of glaciation, the acceptance of this theory was dependent also upon the skills, personality and status of the Geikies and Croll, who developed and promoted the concepts. Sadly, the subsequent rejection of the land-ice concept by Lyell resulted in the same factors challenging the acceptance of the glacial theory.

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