scholarly journals Absolute Parameters of Detached Binaries in the Southern Sky – I: V349 Ara and V4403 Sgr

2015 ◽  
Vol 32 ◽  
Author(s):  
A. Erdem ◽  
D. Sürgit ◽  
C. A. Engelbrecht ◽  
H. P. Van Heerden
Keyword(s):  
South African ◽  
Binary Stars ◽  
Interstellar Extinction ◽  
Main Sequence Stars ◽  
Photometric Observations ◽  
Two Systems ◽  
Theoretical Evolution ◽  
Detached Binaries ◽  
The Masses ◽  
Absolute Parameters

AbstractWe present the first analysis of spectroscopic and photometric observations of the two southern eclipsing binary stars, V349 Ara and V4403 Sgr. Radial velocity curves of these two systems obtained at the South African Astronomical Observatory and their V light curves from the All Sky Automated Survey were solved simultaneously using the Wilson–Devinney code. Our photometric models describe these two systems as Algol-like binary stars with detached configurations. The masses and radii were found to be 2.59 ± 0.07 M⊙, 3.60 ± 0.07 R⊙ and 2.51 ± 0.06 M⊙, 4.15 ± 0.07 R⊙ for the primary and secondary components of V349 Ara, respectively. Those of V4403 Sgr were derived to be 1.33 ± 0.02 M⊙, 1.74 ± 0.02 R⊙ and 1.59 ± 0.03 M⊙, 2.50 ± 0.03 R⊙ for the primary and secondary components, respectively. The distances to V349 Ara and V4403 Sgr were computed to be 677 ± 36 and 199 ± 10 pc from the dynamic parallax, respectively, taking into account interstellar extinction. The evolution cases of these two systems are also examined. Both components of these two systems are evolved main-sequence stars, and the dynamic ages were estimated as approximately 0.67 and 2.29 Gyr for V349 Ara and V4403 Sgr, respectively, when compared to Geneva theoretical evolution models.

Absolute parameters of three southern eclipsing binaries: DQ Car, BK Ind, and V4396 Sgr

2020 ◽  
Vol 493 (2) ◽  
pp. 2659-2675
Author(s):  
Derya Sürgit ◽  
Ahmet Erdem ◽  
Chris A Engelbrecht ◽  
Fred Marang
Keyword(s):  
South African ◽  
Binary Stars ◽  
Main Sequence ◽  
Interstellar Extinction ◽  
Eclipsing Binaries ◽  
Evolutionary Status ◽  
Distance Modulus ◽  
Main Sequence Stars ◽  
The Masses ◽  
Absolute Parameters

ABSTRACT We present combined photometric and spectroscopic analyses of the three southern eclipsing binary stars: DQ Car, BK Ind, and V4396 Sgr. Radial velocity curves of these three systems were obtained at the South African Astronomical Observatory, and their light curves from the available data bases and surveys were used for the analysis. 75 new times of minima for these three eclipsing binaries were derived, and their ephemerides were updated. Only the O–C diagram of DQ Car indicates a cyclical variation, which was interpreted in terms of the light-time effect due to a third body in the system. Our final models describe these three systems as Algol-like binary stars with detached configurations. The masses and radii were found to be M1 = 1.86(±0.17) M⊙, R1 = 1.63(±0.06) R⊙ and M2 = 1.74(±0.17) M⊙, R2 = 1.52(±0.07) R⊙ for the primary and secondary components of DQ Car; M1 = 1.16(±0.05) M⊙, R1 = 1.33(±0.03) R⊙ and M2 = 0.98(±0.04) M⊙, R2 = 1.00(±0.03) R⊙ for BK Ind; and M1 = 3.14(±0.22) M⊙, R1 = 3.00(±0.09) R⊙ and M2 = 3.13(±0.24) M⊙, R2 = 2.40(±0.08) R⊙ for V4396 Sgr, respectively. The distances to DQ Car, BK Ind, and V4396 Sgr were derived to be 701(±50), 285(±20), and 414(±30) pc from the distance modulus formula, taking into account interstellar extinction. The evolutionary status of these three systems was also studied. It has been found that the components of DQ Car are very young stars at the age of ∼25 Myr and those of BK Ind and V4396 Sgr are evolved main-sequence stars at the ages of ∼2.69 Gyr and ∼204 Myr, respectively.

scholarly journals V444 Cygni and CQ Cephei, Key Wolf-Rayet Binary Stars

1991 ◽  
Vol 143 ◽  
pp. 255-255
Author(s):  
Anne B. Underhill
Keyword(s):  
Radial Velocity ◽  
Binary Stars ◽  
Eclipsing Binaries ◽  
Photometric Observations ◽  
Types Of Information ◽  
The Masses

Radial-velocity and photometric observations of eclipsing binaries allow one to estimate the masses of the stars in such systems, their relative brightnesses and sizes. If polarization variations are detected throughout the binary period, one may confirm the inclination of the system. All three types of information are available for V444 Cygni and CQ Cephei, see Underhill, Yang, and Hill (1988a,b), Underhill, Gilroy, and Hill (1990), and the references quoted in those papers.

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 Long-Term Multicolour Photometry of the Young Stellar Objects FHO 26, FHO 27, FHO 28, FHO 29, and V1929 Cygni

2015 ◽  
Vol 32 ◽  
Author(s):  
S. I. Ibryamov ◽  
E. H. Semkov ◽  
S. P. Peneva
Keyword(s):  
Gulf Of Mexico ◽  
Young Stellar Objects ◽  
Main Sequence Stars ◽  
Stellar Objects ◽  
Photometric Variability ◽  
The North ◽  
Dense Molecular Cloud ◽  
Photometric Observations ◽  
All Optical

AbstractResults from long-term multicolour optical photometric observations of the pre-main-sequence stars FHO 26, FHO 27, FHO 28, FHO 29, and V1929 Cyg collected during the period from 1997 June to 2014 December are presented. The objects are located in the dense molecular cloud L935, named ‘Gulf of Mexico’, in the field between the North America and Pelican nebulae. All stars from our study exhibit strong photometric variability in all optical passbands. Using our BVRI observations and data published by other authors, we tried to define the reasons for the observed brightness variations. The presented paper is a part of our long-term photometric study of the young stellar objects in the region of ‘Gulf of Mexico’.

scholarly journals Asteroseismology of two Kepler detached eclipsing binaries

2020 ◽  
Vol 642 ◽  
pp. A91
Author(s):  
A. Liakos
Keyword(s):  
Theoretical Models ◽  
Eclipsing Binaries ◽  
Pulsation Period ◽  
Oscillation Modes ◽  
Modeling Techniques ◽  
Degree Of Certainty ◽  
Detached Binaries ◽  
Scuti Stars ◽  
Absolute Parameters ◽  
Oscillation Properties

The present work contains light curve, spectroscopic, and asteroseismic analyses for KIC 04851217 and KIC 10686876. These systems are detached eclipsing binaries hosting a pulsating component of δ Scuti type and have been observed with the unprecedented accuracy of the Kepler space telescope. Using ground-based spectroscopic observations, the spectral types of the primary components of the systems were estimated as A6V and A5V for KIC 04851217 and KIC 10686876, respectively, with an uncertainty of one subclass. The present spectral classification, together with literature radial velocity curves, were used to model the light curves of the systems and, therefore, to calculate the absolute parameters of their components with a higher degree of certainty. The photometric data were analysed using standard eclipsing binary modeling techniques, while their residuals were further analysed using Fourier transformation techniques to extract the pulsation frequencies of their host δ Scuti stars. The oscillation modes of the independent frequencies were identified using theoretical models of δ Scuti stars. The distances of the systems were calculated using the relation between the luminosity and the pulsation period for δ Scuti stars. Here, the physical and the oscillation properties of the pulsating components of these systems are discussed and compared with others of the same type. Moreover, using all the currently known cases of δ Scuti stars in detached binaries, updated correlations between orbital and dominant pulsation periods and between log g and pulsation periods are derived. It can concluded that the proximity of the companion plays significant role in the evolution of the pulsational frequencies.

South Africa’s COVID-19 lockdown dilemma

2020 ◽  
Vol 10 (3) ◽  
pp. 1-10
Author(s):  
Michael Ward
Keyword(s):  
Economic Impact ◽  
South African ◽  
Human Life ◽  
Grocery Shopping ◽  
Content Type ◽  
Academic Level ◽  
Medical Emergencies ◽  
Daily Wage ◽  
The Masses ◽  
Wage Earners

Learning outcomes The case presents a significant amount of information on the outbreak of COVID-19 and the expected impact on the economy. Although the case is necessarily concise, several links are given to the online articles and video material on which the case is based. This allows participants to deepen their knowledge of the virus and their understanding of its likely economic impact. To frame the discussion, several philosophies, ranging from Libertarianism to Marxism, are lightly expounded. Readers will need to consider divergent ideas; the sanctity of human life versus the monetary value of a life; the hysteria evoked by COVID-19 deaths versus the placid acceptance of an annual 66,000 deaths by another disease – TB; and the differential economic impact of the virus across extremes of inequality. Perhaps, the key issue relates to the skewness in the death rate: Should young people’s livelihood be sacrificed for a few old people about to die anyway? The case also illustrates the essence of a dilemma – a situation in which a difficult choice has to be made between two or more alternatives, especially ones that are equally undesirable. Case overview/synopsis In March 2020, South African President Cyril Ramaposa ordered a 21-day national “lockdown” to enable and enforce social distancing in an effort to slow the spread of the COVID-19. Many other countries had already taken similar steps, but in a country with 43,000 murders annually, South Africa’s response to only 11 COVID-19 deaths and 1,071 cases was both rapid and harsh. Schools, businesses, social areas and parks were closed. Medical emergencies, essential services and weekly grocery shopping were the only permissible activities. Two weeks after lockdown, there were 1,845 cases and 18 deaths, a far cry from the predicted 30,000 cases and 300 deaths, estimated on the basis of the three-day doubling rate at the start of lockdown. Many businesses, pulverised by closure, daily wage earners and those fearful of losing jobs were hopeful that the lockdown would not be extended. In a country with immense inequality, how would the masses under the age of 65 years, already in poverty and now with their lives pulled apart by an imported disease of the wealthy, respond to extended social and economic deprivation followed by bailouts for business? Complexity academic level MBA and Executive Education Supplementary materials Teaching Notes are available for educators only. Subject code CSS: 11 Strategy.

Luminosity and Intrinsic Color Calibration of Main-Sequence Stars With 2Mass Photometry: All Sky Local Extinction

2003 ◽  
Vol 12 (4) ◽  
Author(s):  
Jens Knude ◽  
Claus Fabricius
Keyword(s):  
Color Index ◽  
Main Sequence ◽  
Absolute Magnitude ◽  
Interstellar Extinction ◽  
Local Extinction ◽  
Sequence Information ◽  
Main Sequence Stars ◽  
Color Calibration

AbstractWe present a new color index vs. absolute magnitude calibration of 2MASS JHK photometry. For the A0 to ~G5 and M segments of the main sequence information on the amount of interstellar extinction and its location in space may be obtained.

scholarly journals Photometric Observations of the Central Stars of Planetary Nebulae

1968 ◽  
Vol 34 ◽  
pp. 320-323 ◽  
Author(s):  
William Liller ◽  
Cheng-Yuan Shao
Keyword(s):  
Planetary Nebulae ◽  
Interstellar Extinction ◽  
Photometric Observations ◽  
The Individual ◽  
Central Stars ◽  
Individual Objects

Currently at Harvard, we are engaged in a program for measuring multi-color magnitudes of the central stars of planetary nebulae. We plan to determine magnitudes of all favourable planetaries having central stars brighter than 16th photographic magnitude. The results, when completed, will give us improved information on (1) the amount of interstellar extinction for the individual objects, (2) the luminosities and colors of the central stars, (3) interstellar reddening corrections for spectrophotometric studies, and (4) the existence of variability among the central stars.

scholarly journals On the Distribution of Young Spectroscopic Binary Stars Over the Major Semiaxes of their Orbits

1982 ◽  
Vol 69 ◽  
pp. 129-131
Author(s):  
E.I. Popova ◽  
A.V. Tutukov ◽  
B.M. Shustov ◽  
L.R. Yungelson
Keyword(s):  
Binary Stars ◽  
Binary Systems ◽  
Spectroscopic Binaries ◽  
Close Binary ◽  
Physical Parameters ◽  
Origin And Evolution ◽  
Spectroscopic Binary ◽  
Visible Spectra ◽  
Major Semiaxes ◽  
The Masses

About 60% of stars of the disc population in our Galaxy are close binary systems (CBS). Half of the known CBS are spectroscopic binary stars (Kraitcheva et al., 1978).To know the distribution of a correlation between the masses of CBS components and semiaxes of their orbits is necessary for the investigation of the origin and evolution of CBS. For such statistical investigations, a catalogue of CBS was compiled at the Astronomical Council. The catalogue is based on the 6th Batten catalogue (Batten, 1967), its extensions (Pedoussant and Ginestet, 1971; Pedoussant and Carquillat, 1973) and data published up to the end of 1980 (Popova et al., 1981). Now it is recorded on magnetic tape and contains data on 1041 spectroscopic binaries; 333 of them are stars with two visible spectra. The latter are mostly systems prior to mass exchange and the distribution of physical parameters in these systems reflects the distribution and presumably conditions at the time of formation. Using some assumptions, we can obtain for spectroscopic binaries masses of the components M1 and M2 (or the ratio q = M1/M2) and semiaxes of their orbits. Masses of components with the known sin i were obtained by the usual technique; when sin i was not known, masses were estimated from the spectra. We shall discuss here the distribution of CBS in the M-a plane.

scholarly journals ASAS census of twins

2020 ◽  
Vol 496 (3) ◽  
pp. 2605-2612
Author(s):  
Volkan Bakış ◽  
Zeki Eker ◽  
Oğuzhan Sarı ◽  
Gökhan Yücel ◽  
Eda Sonbaş
Keyword(s):  
Spectral Type ◽  
Binary Stars ◽  
Binary Systems ◽  
Eclipsing Binaries ◽  
Physical Parameters ◽  
Eclipsing Binary ◽  
Type Distribution ◽  
Eclipsing Binary Stars ◽  
Detached Binaries

ABSTRACT Twin binaries were identified among the eclipsing binaries with δ &gt; –30° listed in the All Sky Automated Survey (ASAS) catalogue. In addition to the known twin binaries in the literature, 68 new systems have been identified and photometric and spectroscopic observations were done. Colour, spectral type, temperature, ratio of radii and masses of the components have been derived and are presented. Including 12 twin binary systems that exist in both ASAS and the catalogue of absolute parameters of detached eclipsing binary stars, a total of 80 twin detached binary systems have been statistically studied. A comparison of the spectral type distribution of the twins with those of detached eclipsing binary stars in the ASAS database shows that the spectral type distribution of twins is similar to that of detached systems. This result has been interpreted as indicating that there is no special formation mechanism for twins compared to normal detached binaries. As a result of our case study for HD 154010, a twin binary, we present the precise physical parameters of the system.

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