Revised physical elements of the astrophysically important O9.5+O9.5V eclipsing binary system Y Cygni (original) (raw)
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Spectroscopic characterization of nine binary star systems as well as HIP 107136 and HIP 107533
Astronomische Nachrichten, 2020
We present the results of our second radial velocity (RV) monitoring campaign, carried out with the Échelle spectrograph FLECHAS at the University Observatory Jena in the course of the Großschwabhausen binary survey between December 2016 and June 2018. The aim of this project is to obtain precise RV measurements for spectroscopic binary stars in order to redetermine, verify, improve, and constrain their Keplerian orbital solutions. In this paper, we describe the observations, data reduction, and analysis and present the results of this project. In total, we have taken 721 RV measurements of 11 stars and derived well-determined orbital solutions for nine systems (seven single-and two double-lined spectroscopic binaries) with periods in the range between 2 and 70 days. In addition, we could rule out the orbital solutions for the previously classified spectroscopic binary systems HIP 107136 and HIP 107533, whose radial velocities are found to be constant on the km s −1-level over a span of time of more than 500 days. In the case of HIP 2225, a significant change of its systematic velocity is detected between our individual observing epochs, indicating the presence of an additional companion, which is located on a wider orbit in this system.
New photometric solutions have been carried out on the important eccentric eclipsing system V380 Cygni (B1.5 II-III + B2 V) from U BV differential photoelectric photometry obtained by us. The photometric elements obtained from the analysis of the light curves have been combined with the spectroscopic solution recently published by Popper & Guinan and have led to the physical properties of the system components. The effective temperature of the stars has been determined by fitting IUE UV spectrophotometry to Kurucz model atmospheres and compared with other determinations from broad-band and intermediate-band standard photometry. The values of mass, absolute radius, and effective temperature, for the primary and secondary stars are: 11.1±0.5 M ⊙ , 14.7±0.2 R ⊙ , 21 350±400 K, and 6.95±0.25 M ⊙ , 3.74±0.07 R ⊙ , 20 500±500 K, respectively. In addition, a re-determination of the system's apsidal motion rate has been done from the analysis of 12 eclipse timings obtained from 1923 to 1995. The apsidal motion study yields the internal mass distribution of the more luminous component. Using stellar structure and evolutionary models with modern input physics, tests on the extent of convection in the core of the more massive B1.5 II-III star of the system have been carried out. Both the analysis of the log g − log T eff diagram and the apsidal motion study indicate a star with a larger convective core, and thus more centrally condensed, than currently assumed. This has been quantified in form of an overshooting parameter with a value of α ov ≈ 0.6 ± 0.1. Finally, the tidal evolution of the system (synchronization and circularization times) has also been studied.
Stellar parameters of the two binary systems: HIP 14075 and HIP 14230
Journal of Astrophysics and Astronomy, 2018
We present the stellar parameters of the individual components of the two old close binary systems HIP 14075 and HIP 14230 using synthetic photometric analysis. These parameters are accurately calculated based on the best match between the synthetic photometric results within three different photometric systems with the observed photometry of the entire system. From the synthetic photometry, we derive the masses and radii of HIP 14075 as: M A = 0.99 ± 0.19 M , R A = 0.877 ± 0.08 R for the primary and M B = 0.96 ± 0.15 M , R B = 0.821 ± 0.07 R for the secondary, and of HIP 14230 as: M A = 1.18 ± 0.22 M , R A = 1.234 ± 0.05 R for the primary and M B = 0.84 ± 0.12 M , R B = 0.820 ± 0.05 R for the secondary, both systems depend on Gaia parallaxes. Based on the positions of the components of the two systems on a theoretical Hertzsprung-Russell diagram, we find that the age of HIP 14075 is 11.5 ± 2.0 Gyr and of HIP 14230 is 3.5 ± 1.5 Gyr. Our analysis reveals that both systems are old close binary systems (≈> 4 Gyr). Finally, the positions of the components of both systems on the stellar evolutionary tracks and isochrones are discussed.
The Astrophysical Journal, 2006
We present spectroscopic and photometric observations of the eclipsing system V1061 Cyg, previously thought to be a member of the rare class of "cool Algols". We show that it is instead a hierarchical triple system in which the inner eclipsing pair (with P = 2.35 days) is composed of main-sequence stars and is well detached, and the third star is also visible in the spectrum. We combine the radial velocities for the three stars, times of eclipse, and intermediate astrometric data from the HIPPARCOS mission (abscissae residuals) to establish the elements of the outer orbit, which is eccentric and has a period of 15.8 yr. We determine accurate values for the masses, radii, and effective temperatures of the binary components: M Aa = 1.282 ± 0.015 M ⊙ , R Aa = 1.615 ± 0.017 R ⊙ , and T Aa eff = 6180 ± 100 K for the primary (star Aa), and M Ab = 0.9315 ± 0.0068 M ⊙ , R Ab = 0.974 ± 0.020 R ⊙ , and T Ab eff = 5300 ± 150 K for the secondary (Ab). The masses and radii have relative errors of only 1-2%. Both stars are rotating rapidly (v sin i values are 36±2 km s −1 and 20±3 km s −1 ) and have their rotation synchronized with the orbital motion. There are signs of activity including strong X-ray emission and possibly spots. The mass of the tertiary is determined to be M B = 0.925 ± 0.036 M ⊙ and its effective temperature is T B eff = 5670 ± 150 K.
Further critical tests of stellar evolution by means of double-lined eclipsing binaries
Monthly Notices of the Royal Astronomical Society, 1997
The most accurately measured stellar masses and radii come from detached, double-lined eclipsing binaries, as compiled by Andersen. We present a detailed quantitative comparison of these fundamental data with evolution models for single stars computed with our evolution code, both with and without the effects of enhanced mixing or overshooting beyond the convective cores. We use the same prescription for overshooting that Schroder, Pols & Eggleton found to reproduce the properties of r Aurigae binaries. For about 80 per cent of the 49 binary systems in the sample, both sets of models provide a good fit to both stars at a single age and metallicity within the observational uncertainties. We discuss possible causes for the discrepancies in the other systems. For only one system, AI Hya, do the enhanced-mixing models provide a significantly better fit to the data. For two others (WX Cep and TZ For) the fit to the enhanced-mixing models is also better. None of the other systems can individually distinguish between the models with and without enhanced mixing. However, the number of systems in a post-main-sequence phase is in much better agreement with the enhanced-mixing models. This test provides supportive evidence for extended mixing in main-sequence stars in the range 2-3M 0 .
RX J0513.1+0851 and RX J0539.9+0956: Two Young, Rapidly Rotating Spectroscopic Binary Stars
The Astronomical Journal, 2013
RX J0513.1+0851 and RX J0539.9+0956 were previously identified as young, low-mass, single-lined spectroscopic binary systems and classified as weak-lined T Tauri stars at visible wavelengths. Here we present radial velocities, spectral types, v sin i values, and flux ratios for the components in these systems resulting from two-dimensional cross-correlation analysis. These results are based on highresolution, near-infrared spectroscopy taken with the Keck II telescope to provide a first characterization of these systems as double-lined rather than single-lined. It applies the power of infrared spectroscopy to the detection of cool secondaries; the flux scales as a less steep function of mass in the infrared than in the visible, thus enabling an identification of low-mass secondaries. We found that the RX J0513.1+0851 and RX J0539.9+0956 primary stars are fast rotators, 60 km s −1 and 80 km s −1 respectively; this introduces extra difficulty in the detection of the secondary component as a result of the quite broad absorption lines. To date, these are the highest rotational velocities measured for a pre-main sequence spectroscopic binary. The orbital parameters and mass ratios were determined by combining new visible light spectroscopy with our infrared data for both systems. For RX J0513.1+0851, we derived a period of ∼4 days and a mass ratio of q = 0.46 ± 0.01 and for RX J0539.9+0956, a period of ∼1117 days and a mass ratio of q = 0.66 ± 0.01. Based on our derived properties for the stellar components, we estimate the luminosities and hence distances to these binaries at 220 pc and 90 pc. They appear to be significantly closer than previously estimated.
The IGRINS YSO Survey. I. Stellar Parameters of Pre-main-sequence Stars in Taurus-Auriga
The Astrophysical Journal
We present fundamental parameters for 110 canonical K-& M-type (1.3−0.13 M) Taurus-Auriga young stellar objects (YSOs). The analysis produces a simultaneous determination of effective temperature (T eff), surface gravity (log g), magnetic field strength (B), and projected rotational velocity (v sin i). Our method employed synthetic spectra and high-resolution (R∼45,000) near-infrared spectra taken with the Immersion GRating INfrared Spectrometer (IGRINS) to fit specific K-band spectral regions most sensitive to those parameters. The use of these high-resolution spectra reduces the influence of distance uncertainties, reddening, and non-photospheric continuum emission on the parameter determinations. The median total (fit + systematic) uncertainties were 170 K, 0.28 dex, 0.60 kG, 2.5 km s −1 for T eff , log g, B, and v sin i, respectively. We determined B for 41 Taurus YSOs (upper limits for the remainder) and find systematic offsets (lower T eff , higher log g and v sin i) in parameters when B is measurable but not considered in the fit. The average log g for the Class ii and Class iii objects differs by 0.23±0.05 dex, which is consistent with Class iii objects being the more evolved members of the star-forming region. However, the dispersion in log g is greater than the uncertainties, which highlights how the YSO classification correlates with age (log g), yet there are exceptionally young (lower log g) Class iii YSOs and relatively old (higher log g) Class ii YSOs with unexplained evolutionary histories. The spectra from this work are provided in an online repository along with TW Hydrae Association (TWA) comparison objects and the model grid used in our analysis.
Binarity as a tool for determining the physical properties and evolutionary aspects of A-stars
Proceedings of the International Astronomical Union, 2004
Double-lined-eclipsing binaries are the essential systems for the measurement of stellar masses and radii. About 50-60 systems have components (mostly A-stars) for which these values are known with an uncertainty less than 1-2%. Therefore, these systems are very suitable to improve our understanding of stellar structure and evolution. In this paper, special attention is given to the assessment of the role of internal rotation of the early-type stars in selected double-lined binaries (i.e., EK Cep, PV Cas, and θ 2 Tau): it is shown that adoption of rapidly rotating cores for such stars permits the models to be in very good agreement with the observational results including the apsidal advance rates.
The Astrophysical Journal, 2009
We report extensive spectroscopic and differential photometric BVRI observations of the active, detached, 1.309-day double-lined eclipsing binary IM Vir, composed of a G7-type primary and a K7 secondary. With these observations we derive accurate absolute masses and radii of M 1 = 0.981 ± 0.012 M ⊙ , M 2 = 0.6644 ± 0.0048 M ⊙ , R 1 = 1.061 ± 0.016 R ⊙ , and R 2 = 0.681 ± 0.013 R ⊙ for the primary and secondary, with relative errors under 2%. The effective temperatures are 5570 ± 100 K and 4250 ± 130 K. The significant difference in mass makes this a favorable case for comparison with stellar evolution theory. We find that both stars are larger than the models predict, by 3.7% for the primary and 7.5% for the secondary, as well as cooler than expected, by 100 K and 150 K, respectively. These discrepancies are in line with previously reported differences in low-mass stars, and are believed to be caused by chromospheric activity, which is not accounted for in current models. The effect is not confined to low-mass stars: the rapidly-rotating primary of IM Vir joins the growing list of objects of near-solar mass (but still with convective envelopes) that show similar anomalies. The comparison with the models suggests an age of 2.4 Gyr for the system, and a metallicity of [Fe/H] ≈ −0.3 that is consistent with other indications, but requires confirmation.
Astronomy & Astrophysics, 2012
We present an asteroseismic study of the solar-like stars KIC 11395018, KIC 10273246, KIC 10920273, KIC 10339342, and KIC 11234888 using short-cadence time series of more than eight months from the Kepler satellite. For four of these stars, we derive atmospheric parameters from spectra acquired with the Nordic Optical Telescope. The global seismic quantities (average large frequency separation and frequency of maximum power), combined with the atmospheric parameters, yield the mean density and surface gravity with precisions of 2% and ∼0.03 dex, respectively. We also determine the radius, mass, and age with precisions of 2-5%, 7-11%, and ∼35%, respectively, using grid-based analyses. Coupling the stellar parameters with photometric data yields an asteroseismic distance with a precision better than 10%. A v sin i measurement provides a rotational period-inclination correlation, and using the rotational periods from the recent literature, we constrain the stellar inclination for three of the stars. An Li abundance analysis yields an independent estimate of the age, but this is inconsistent with the asteroseismically determined age for one of the stars. We assess the performance of five grid-based analysis methods and find them all to provide consistent values of the surface gravity to ∼0.03 dex when both atmospheric and seismic constraints are at hand. The different grid-based analyses all yield fitted values of radius and mass to within 2.4σ, and taking the mean of these results reduces it to 1.5σ. The absence of a metallicity constraint when the average large frequency separation is measured with a precision of 1% biases the fitted radius and mass for the stars with non-solar metallicity (metal-rich KIC 11395018 and metal-poor KIC 10273246), while including a metallicity constraint reduces the uncertainties in both of these parameters by almost a factor of two. We found that including the average small frequency separation improves the determination of the age only for KIC 11395018 and KIC 11234888, and for the latter this improvement was due to the lack of strong atmospheric constraints.