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A catalogue of chromospherically active binary stars (third edition)
(Wiley-Blackwell, 2008) Eker, Z.; Ak, N. Filiz; Bilir, S.; Dogru, D.; Tueysuez, M.; Soydugan, Esin; Bakis, H.
The catalogue of chromospherically active binaries (CABs) has been revised and updated. With 203 new identifications, the number of CAB stars is increased to 409. The catalogue is available in electronic format where each system has a number of lines (suborders) with a unique order number. The columns contain data of limited numbers of selected cross references, comments to explain peculiarities and the position of the binarity in case it belongs to a multiple system, classical identifications (RS Canum Venaticorum, BY Draconis), brightness and colours, photometric and spectroscopic data, a description of emission features (Ca II H and K, H alpha, ultraviolet, infrared), X-ray luminosity, radio flux, physical quantities and orbital information, where each basic entry is referenced so users can go to the original sources.
Absolute dimensions and apsidal motion of the eccentric binary PT Velorum
(Blackwell Publishing, 2008) Bakis, V.; Bakis, H.; Demircan, O.; Eker, Z.
High-resolution (lambda/d lambda similar to 41 000) echelle spectra of the eccentric binary system PT Vel were analysed. Precise spectroscopic orbital elements of the system were obtained by means of cross-correlation technique. According to the solution of radial velocities with Hipparcos and All Sky Automated Survey-3 (ASAS-3) light curves, PT Vel consists of two main-sequence stars with masses M-1 = 2.198 +/- 0.016 M-circle dot, M-2 = 1.626 +/- 0.009 M-circle dot, radii R-1 = 2.094 +/- 0.020 R-circle dot, R-2 = 1.559 +/- 0.020 R-circle dot and temperatures T-eff1 = 9250 +/- 150 K, T-eff2 = 7650 +/- 200 K separated from each other by A = 9.74 +/- 0.02 R-circle dot in an orbit inclined 88.2 degrees +/- 0.5. The projected rotational velocities of component stars were found to be (v sin i)(1) = 63 +/- 2 and (v sin i)(2) = 40 +/- 3 km s(-1) from the comparison of observed spectra with synthetic spectra which were calculated using model atmospheres. Our measurements of the projected rotational velocities indicate that both stars rotate synchronously. Analysis of longitude of periastron values obtained from light-curve analysis from different photometric sets of this moderately eccentric system (e = 0.127 +/- 0.006) has revealed a significant motion of the line of apsides of (w) over dot = 0.0097 +/- 0 degrees.0004 cycle(-1) corresponding to an apsidal motion period of U = 182.2 +/- 8.4 yr. The contribution from general relativity effects is moderate (similar to 9 per cent). A comparison with predictions from interior structure models shows the real stars to be more concentrated in mass than expected. Comparison of absolute dimensions with theoretical isochrones yielded an age of the system of 400 +/- 40 Myr.
Active binary R Arae revisited: Bringing the secondary component to light and physical modelling of the circumstellar material
(Oxford Univ Press, 2016) Bakis, H.; Bakis, V.; Eker, Z.; Demircan, O.
The spectral lines of the secondary component of the active binary system R Ara were uncovered for the first time, which allowed directly to determine the parameters of the spectroscopic orbit. The mass ratio of the system is updated to a new observational value of M-2/M-1 = 0.305 +/- 0.005 which is similar to 20 per cent smaller than the literature value (M-2/M-1 = 0.39). Modelling the reconstructed component spectra yielded the equatorial rotational velocities of the components as nu(rot1) = 202 km s(-1) and nu(rot2) = 73 km s(-1) indicating a very fast rotation (similar to 5 times faster than the synchronous rotation velocity) for the primary and synchronous rotation for the secondary component. The circumstellar material in the system was investigated using the Hipparcossatellite data and the high-resolution (R similar to 41 000) spectral data. According to our model, there is always material transferring from the secondary component on to the primary causing a hot region on its surface. The structural difference between the spectra taken at the same orbital phase but at different epochs proved that the density and the velocity of the transferring material are variable. There are three main trends in the light curve and spectral line variations suggesting the activity cycles for the system, namely quiescent, moderate and, active cycles. It was estimated that the circumstellar material around could be extended to large distances up to 40 R-circle dot from the system.
Dynamical evolution of active detached binaries on the log Jo-log M diagram and contact binary formation
(Blackwell Publishing, 2006) Eker, Z.; Demircan, O.; Bilir, S.; Karatas, Y.
Orbital angular momentum (OAM, J(o)), systemic mass (M) and orbital period (P) distributions of chromospherically active binaries (CAB) and W Ursae Majoris (W UMa) systems were investigated. The diagrams of logJ(o)-IogP, logM-logP and logJ(o)-IogM were fortned from 119 CAB and 102 W UMa stars. The log J(o)-Iog M diagram is found to be most meaningful in demonstrating dynamical evolution of binary star orbits. A slightly curved borderline (contact border) separating the detached and the contact systems was discovered on the log J(o)-Iog M diagram. Since the orbital size (a) and period (P) of binaries are determined by their current J(o), M and mass ratio, q, the rates of OAM loss (d log J(o)/dt) and mass loss (d log M/dt) are primary parameters to determine the direction and the speed of the dynamical evolution. A detached system becomes a contact system if its own dynamical evolution enables it to pass the contact border on the log J(o)-log M diagram. The evolution of q for a mass-losing detached system is unknown unless the mass-loss rate for each component is known. Assuming q is constant in the first approximation and using the mean decreasing rates of J(o) and M from the kinematical ages of CAB stars, it has been predicted that 11, 23 and 39 per cent of current CAB stars would transform to W UMa systems if their nuclear evolution permits them to live 2, 4 and 6 Gyr, respectively.
Effective Temperatures of Selected Main-Sequence Stars with the Most Accurate Parameters
(Astronomical Soc Pacific, 2015) Soydugan, Faruk; Eker, Z.; Soydugan, Esin; Bilir, S.; Gokce, E. Y.; Steer, I.; Tuysuz, M.
In this study we investigate the distributions of the properties of detached double-lined binaries (DBs) in the mass luminosity, mass radius, and mass-effective temperature diagrams. We have improved the classical mass luminosity relation based on the database of DBs by Eker et al. (2014a). Based on the accurate observational data available to us we propose a method for improving the effective temperatures of eclipsing binaries with accurate mass and radius determinations.
Empirical bolometric correction coefficients for nearby main-sequence stars in the Gaia era
(Oxford Univ Press, 2020) Eker, Z.; Soydugan, Faruk; Bilir, S.; Bakis, V; Alicavus, F.; Ozer, S.; Aslan, G.
Nearby detached double-lined eclipsing binaries with most accurate data were studied and 290 systems were found with at least one main-sequence component having a metallicity of 0.008 <= Z <= 0.040. Stellar parameters, light ratios, Gaia Data Release 2 trigonometric parallaxes, extinctions and/or reddening were investigated and only 206 systems were selected as eligible to calculate empirical bolometric corrections. NASA/IPAC Galactic dustmaps were the main source of extinctions. Unreliable extinctions at low Galactic latitudes vertical bar b vertical bar <= 5 degrees were replaced with individual determinations, if they exist in the literature, else associated systems were discarded. The main-sequence stars of te remaining systems were used to calculate the bolometric corrections (BCs) and to calibrate the BC-T-eff relation, which is valid in the range 3100-36 000 K. De-reddened (B - V)(0) colours, on the other hand, allowed us to calibrate two intrinsic colour-effective temperature relations; the linear one is valid for T-eff > 10 000 K, while the quadratic relation is valid for T-eff < 10 000 K; that is, both are valid in the same temperature range in which the BC-Teff relation is valid. New BCs computed from Teff and other astrophysical parameters are tabulated, as well.
Evidences on secular dynamical evolution of detached active binary orbits and contact binary formation
(Astronomical Soc Pacific, 2007) Eker, Z.; Demircan, O.; Bilir, S.; Karatas, Y.
Evidence of secular dynamical evolution for detached active binary orbits are presented. First order decreasing rates of orbital angular momentum (OAM), systemic mass (M = M-1 + M-2) and orbital period of detached active binaries have been determined a J/J = 3.48 x 10(-10)yr(-1),M/M = 1.30 x 10(10)yr(-1) and P/P 3.96 x 10(-10)yr(-1) from the kinematical ages of 62 field detached systems. The ratio of d log J/ d log M = 2.68 implies that either there are mechanisms which amplify AM loss delta = 2.68 times with respect to isotropic AM loss of hypothetical isotropic winds or there exist external causes contributing AM loss in order to produce this mean rate of decrease for orbital periods. Various decreasing rates of OAM (d log J /dt) and systemic mass (d log M /dt) determine various speeds of dynamical evolutions towards a contact configuration. According to average dynamical evolution with delta = 2.68, the fraction of 10, 22 and 39 per cent of current detached sample is expected to be contact system within 2, 4 and 6 Gyr respectively.
Formation and evolution of W Ursa Majoris stars: fallacies and corrections
(Wiley-Blackwell, 2008) Eker, Z.; Demircan, O.; Bilir, S.
Period histograms of eclipsing binaries generated with data from the All-Sky Automated Survey cannot be interpreted only using orbital evolution. Eclipse probabilities, selection effects and space distributions in the solar neighbourhood should be considered before any interpretations are made. Depending upon the physical dimensions (the total mass and the period) of the progenitor stars and the efficiency of the angular momentum loss mechanism, a newly formed W Ursa Majoris type binary can be at any age up to several Gyr. Also, the evolution in the contact stage is controlled not only by angular momentum and mass loss but also by mass transfer between the component stars. Thus, the mean life of the contact stages should be about 1.6 Gyr. A different time-scale would cause inconsistencies.
High Resolution Coude Echelle Spectroscopy of IX Per
(Amer Inst Physics, 2009) Ak, N. Filiz; Eker, Z.; Ak, H.; Kuecuek, I.
High resolution (R=45033) Coude - Echelle spectra of IX Per has been obtained at TUBITAK National Observatory (TUG) of Turkey. IX Per has been known to be a single lined (SBI) spectroscopic binary having chromospheric activity. However, analyzed spectra of IX Per by KOREL disentangling method indicated that the system is a double lined (SB2) spectroscopic binary. Weaker lines from the secondary arc discovered on the decomposed spectra. A preliminary orbit indicates that the mass ratio of the system is 0.64. The light contribution of the secondary is tip to 10% in investigated spectral region. Circular orbit is sufficient to explain radial velocity variations.
Interrelated main-sequence mass-luminosity, mass-radius, and mass-effective temperature relations
(Oxford Univ Press, 2018) Eker, Z.; Bakis, V.; Bilir, S.; Soydugan, Faruk; Steer, I.; Soydugan, Esin; Bakis, H.
Absolute parameters of 509 main-sequence stars selected from the components of detached eclipsing spectroscopic binaries in the solar neighbourhood are used to study mass-luminosity, mass-radius, and mass-effective temperature relations (MLR, MRR, and MTR). The MLR function is found better if expressed by a six-piece classical MLR (L proportional to M-alpha) rather than a fifth or a sixth degree polynomial within the mass range of 0.179 < M/M-circle dot <= 31. The break points separating the mass ranges with classical MLR do not appear to us to be arbitrary. Instead, the data indicate abrupt changes along the mass axis in the mean energy generation per unit of stellar mass. Unlike the MLR function, the MRR and MTR functions cannot be determined over the full range of masses. A single-piece MRR function is calibrated from the radii of stars with M <= 1.5M(circle dot), while a second single-piece MTR function is found for stars with M > 1.5M(circle dot). The missing part of the MRR is computed from the MLR and MTR, while the missing part of the MTR is computed from the MLR and MRR. As a result, we have interrelated the MLR, MRR, and MTR, which are useful in determining the typical absolute physical parameters of main-sequence stars of given masses. These functions are also useful to estimate typical absolute physical parameters from typical T-eff values. Thus, we were able to estimate the typical absolute physical parameters of main-sequence stars observed in the Sejong Open cluster Survey, based on that survey's published values for T-eff. Since typical absolute physical parameters of main-sequence stars cannot normally be determined in such photometric surveys, the interrelated functions are shown to be useful to compute such missing parameters from similar surveys.
MAIN-SEQUENCE EFFECTIVE TEMPERATURES FROM A REVISED MASS-LUMINOSITY RELATION BASED ON ACCURATE PROPERTIES
(Iop Publishing Ltd, 2015) Eker, Z.; Soydugan, Faruk; Soydugan, Esin; Bilir, S.; Gokce, E. Yaz; Steer, I.; Tuysuz, M.
The mass-luminosity (M-L), mass-radius (M-R), and mass-effective temperature (M-T-eff) diagrams for a subset of galactic nearby main-sequence stars with masses and radii accurate to <= 3% and luminosities accurate to <= 30% (268 stars) has led to a putative discovery. Four distinct mass domains have been identified, which we have tentatively associated with low, intermediate, high, and very high mass main-sequence stars, but which nevertheless are clearly separated by three distinct break points at 1.05, 2.4, and 7 M-circle dot within the studied mass range of 0.38-32 M-circle dot. Further, a revised mass-luminosity relation (MLR) is found based on linear fits for each of the mass domains identified. The revised, mass-domain based MLRs, which are classical (L proportional to M-alpha), are shown to be preferable to a single linear, quadratic, or cubic equation representing an alternative MLR. Stellar radius evolution within the main sequence for stars with M > 1 M-circle dot is clearly evident on the M-R diagram, but it is not clear on the M-T-eff diagram based on published temperatures. Effective temperatures can be calculated directly using the well known Stephan-Boltzmann law by employing the accurately known values of M and R with the newly defined MLRs. With the calculated temperatures, stellar temperature evolution within the main sequence for stars with M>1 M-circle dot is clearly visible on the M-T-eff diagram. Our study asserts that it is now possible to compute the effective temperature of a main-sequence star with an accuracy of similar to 6%, as long as its observed radius error is adequately small (<1%) and its observed mass error is reasonably small (<6%).
? Muscae
(Wiley-Blackwell, 2007) Bakis, V.; Bakis, H.; Eker, Z.; Demircan, O.
High-resolution (lambda/d lambda similar to 41 000) echelle spectra of the multiple system eta Muscae were analysed. Precise spectroscopic orbital elements of the close pair eta Muscae-A were obtained by means of two techniques; cross-correlation and spectral disentangling. The updated light elements of the close pair were derived using new photometric and spectroscopic data together with Hipparcos ephemerides. According to simultaneous studies of radial velocities with Hipparcos light curve and recent and historic light curves in Stromgren bands, eta Mus-A consists of two quasi-identical components: M(1) =3.30 M., M(2) = 3.29 M., R(1) = 2.14 R., R(2) = 2.13 R., T(1)=12 700 K and T(2) = 12 550 K separated from each other by a = 14.11 R. in an orbit inclined 77 degrees.4. The membership of eta Mus-A to the Lower Centaurus-Crux OB association is discussed. The rotational velocity of the primary component was found to be smaller than that of the secondary component. The asynchronous slow rotation of the primary and the synchronous rotation of the secondary imply a recent decrease in the orbital period, either due to orbital angular momentum being transferred to the visual companion eta Mus-C or due to relatively frequent stellar encounters in this crowded region. The visual companion eta Mus-B is found to be gravitationally unbound to the close pair eta Mus-A. The radial velocity measurements of the visual companion eta Mus-B, when combined with its positional information, support its membership to the Lower Centaurus-Crux OB association, but the evidence for membership of eta Mus-A is weaker.
New absolute magnitude calibrations for detached binaries
(Wiley-V C H Verlag Gmbh, 2008) Bilir, S.; Ak, T.; Soydugan, Esin; Soydugan, Faruk; Yaz, E.; Ak, N. Filiz; Eker, Z.
Lutz-Kelker bias corrected absolute magnitude calibrations for the detached binary systems with main-sequence components are presented. The absolute magnitudes of the calibrator stars were derived at intrinsic colours of Johnson-Cousins and 2MASS (Two Micron All Sky Survey) photometric systems. As for the calibrator stars, 44 detached binaries were selected from the Hipparcos catalogue, which have relative observed parallax errors smaller than 15% (sigma(pi)/pi <= 0.15). The calibration equations which provide the corrected absolute magnitude for optical and near-infrared pass bands are valid for wide ranges of colours and absolute magnitudes: -0.18 < (B - V)(0) < 0.91, -1.6 < M-V < 5.5 and -0.15 < (J - H)(0) < 0.50, -0-02 < (H - K-s)(0) < 0. 13, 0 < M-J < 4, respectively. The distances computed using the luminosity-colours (LCs) relation with optical (B V) and near-infrared (J H K-s) observations were compared to the distances found from various other methods. The results show that new absolute magnitude calibrations of this study can be used as a convenient statistical tool to estimate the true distances of detached binaries out of Hipparcos' distance limit. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA. Weinheim
New absolute magnitude calibrations for W Ursa Majoris type binaries
(Wiley-V C H Verlag Gmbh, 2009) Eker, Z.; Bilir, S.; Yaz, E.; Demircan, O.; Helvaci, M.
Parallaxes of W UMa stars in the Hipparcos catalogue have been analyzed. 31 W UMa stars. which have the most accurate parallaxes (sigma(pi)/pi < 0.15) which are neither associated with a photometric tertiary nor with evidence of a Visual companion, were selected for re-calibrating the Period-Luminosity-Color (PLC) relation of W UMa stars. Using the Lutz-Kelker (LK) bias corrected (most probable) parallaxes. periods (0.26 < P < 0.87, P in days), and colors (0.04 < (B - V)(0) < 1.28) of the 31 selected W UMa, the PLC relation have been revised and re-calibrated. The difference between the old (revised but no( bias corrected) and the new (LK bias corrected) relations are almost negligible in predicting the distances of W UMa stars Up to about 100 pc. But, it increases and may become intolerable as distances of stars increase. Additionally, using (J - H)(0) and (H -K(s))(0) colors from 2MASS (Two Micron All Sky Survey) data, a PLC relation working with infrared data was derived. It can be used with infrared colors in the range -0.01 < (J-H)(0) < 0.58, and -0.10 < (H - K(s))(0) < 0.18. Despite of the fact that the 2MASS data refer to single epoch observations which are not guaranteed to be taken at maximum brightness of the W UMa stars. the established relation has been found surprisingly consistent and reliable in predicting LK corrected distances of W UMa stars. (C) 2009 WILEY-VCH Verlag GmbH & Co, KGaA, Weinheim
Solar and stellar rotation
(Astronomical Soc Pacific, 2007) Demircan, O.; Eker, Z.; Filiz-Ak, N.
The secular evolution of the stellar rotation through angular momentum loss, driven by the stellar wind, and the consequences of the angular momentum transfers between orbit and spinning components in binary star systems will be reviewed with the special emphasis on the Solar rotation. A large co-rotating distance (Alfven radius) of the magnetically driven wind around single stars will be introduced to explain the large angular momentum loss from close binary star systems.
Spatial distribution and galactic model parameters of cataclysmic variables
(Elsevier Science Bv, 2008) Ak, T.; Bilir, S.; Ak, S.; Eker, Z.
The spatial distribution, galactic model parameters and luminosity function of cataclysmic variables (CVs) in the solar neighbourhood have been determined from a carefully established sample of 459 CVs. The sample contains all of the CVs with distances computed from the period-luminosity-colours (PLCs) relation of CVs which has been recently derived and calibrated with 2MASS photometric data. It has been found that an exponential function fits best to the observational z-distributions of all of the CVs in the sample, non-magnetic CVs and dwarf novae, while the sech(2) function is more appropriate for nova-like stars and polars. The vertical scaleheight of CVs is 158 +/- 14 pc for the 2MASS J-band limiting apparent magnitude of 15.8. On the other hand, the vertical scaleheights are 128 +/- 20 and 160 +/- 5 pc for dwarf novae and nova-like stars, respectively. The local space density of CVs is found to be similar to 3 x 10(-5) pc(-3) Which is in agreement with the lower limit of the theoretical predictions. The luminosity function of CVs shows an increasing trend toward higher space densities at low luminosities, implying that the number of short-period systems should be high. The discrepancies between the theoretical and observational population studies of CVs will almost disappear if for the z-dependence of the space density the sech(2) density function is used. (C) 2007 Elsevier B.V. All rights reserved.
The Catalogue of Stellar Parameters from the Detached Double-Lined Eclipsing Binaries in the Milky Way
(Cambridge Univ Press, 2014) Eker, Z.; Bilir, S.; Soydugan, Faruk; Gokce, E. Yaz; Soydugan, Esin; Tuysuz, M.; Senyuz, T.
The most accurate stellar astrophysical parameters were collected from the solutions of the light and the radial velocity curves of 257 detached double-lined eclipsing binaries in the Milky Way. The catalogue contains masses, radii, surface gravities, effective temperatures, luminosities, projected rotational velocities of the component stars, and the orbital parameters. The number of stars with accurate parameters increased 67% in comparison to the most recent similar collection by Torres, Andersen, & Gimenez (2010). Distributions of some basic parameters were investigated. The ranges of effective temperatures, masses, and radii are 2 750 < T-eff (K)< 43 000, 0.18 < M/M-circle dot < 33, and 0.2 < R/R-circle dot < 21.2, respectively. Being mostly located in one kpc in the Solar neighborhood, the present sample covers distances up to 4.6 kpc within the two local Galactic arms, Carina-Sagittarius and Orion Spur. The number of stars with both mass and radius measurements better than 1% uncertainty is 93, better than 3% uncertainty is 311, and better than 5% uncertainty is 388. It is estimated from the Roche lobe filling factors that 455 stars (88.5% of the sample) are spherical within 1% of uncertainty.
The early-type semidetached binary system V716 Centaurus
(Oxford Univ Press, 2008) Bakis, H.; Bakis, V.; Demircan, O.; Eker, Z.
New high-resolution spectra of V716 Cen revealed for the first time lines of the secondary component and its radial velocities. The simultaneous solution of the new radial velocity curves and the Hipparcos light curve yield the reliable absolute dimensions of this semidetached system. The masses for the primary and secondary are M-1 = 5.68 +/- 0.07 M-circle dot and M-2 = 2.39 +/- 0.05 M-circle dot respectively, and the radii are R-1 = 4.08 +/- 0.07 R-circle dot and R-2 = 3.36 +/- 0.02 R-circle dot. We derive also effective temperatures of T-eff1 = 15 500 +/- 50 K and T-eff2 = 9000 +/- 80 K, and equatorial rotational velocities of v(rot) sin i = 137 +/- 2 km s(-1) and v(rot) sin i = 116 +/- 7 km s(-1). These rotational velocities imply that the components rotate synchronously. The distance to the system is d = 339 +/- 8 pc, in good agreement with the less accurate Hipparcos distance (337 +/- 72 pc). The primary is underluminous and the secondary overluminous compared to normal main-sequence stars of the same mass. This implies that the secondary component of the semidetached system is in slow mass transferring stage after mass ratio reversal, although the Ha-line profiles do not show clear evidence for this.
The spectroscopic orbits of three double-lined eclipsing binaries: I. BG Ind, IM Mon, RS Sgr
(Elsevier Science Bv, 2010) Bakis, V.; Bakis, H.; Bilir, S.; Soydugan, Faruk; Soydugan, Esin; Demircan, O.; Eker, Z.
We present the spectroscopic orbit solutions of three double-lines eclipsing binaries, BG Ind, IM Mon and RS Sgr. The first precise radial velocities (RVs) of the components were determined using high resolution echelle spectra obtained at Mt. John University Observatory in New Zealand. The RVs of the components of BG Ind and RS Sgr were measured using Gaussian fittings to the selected spectral lines, whereas two-dimensional cross-correlation technique was preferred to determine the RVs of IM Mon since it has relatively short orbital period among the other targets and so blending of the lines is more effective. For all systems, the Keplerian orbital solution was used during the analysis and also circular orbit was adopted because the eccentricities for all targets were found to be negligible. The first precise orbit analysis of these systems gives the mass ratios of the systems as 0.894, 0.606 and 0.325, respectively for BG Ind, IM Mon and RS Sgr. Comparison of the mass ratio values, orbital sizes and minimum masses of the components of the systems indicates that all systems should have different physical, dynamical and probable evolutionary status. (C) 2009 Elsevier B.V. All rights reserved.

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