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High resolution CoudeEchelle spectra of IX Per has been obtained at TÜBİTAK National Observatory (TUG) of Turkey. IX Per has been known to be a single lined (SB1) spectroscopic binary having chromospheric activity. However, analyzed... more
High resolution CoudeEchelle spectra of IX Per has been obtained at TÜBİTAK National Observatory (TUG) of Turkey. IX Per has been known to be a single lined (SB1) spectroscopic binary having chromospheric activity. However, analyzed spectra of IX Per by KOREL disentangling ...
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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... more
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 as $\dot J/J = -3.48 \times 10^{-10}$yr$^{-1}$, $\dot M/M = -1.30 \times 10^{-10}$yr$^{-1}$ and $\dot P/P = -3.96\times 10^{-10}$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 fract...
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Orbital angular momentum (Jo), 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 log Jo - log P, log M - log P and log... more
Orbital angular momentum (Jo), 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 log Jo - log P, log M - log P and log Jo-log M were formed from 119 CAB and 102 W UMa stars. The log Jo-log 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 Jo - log M diagram. Since orbital size (a) and period (P) of binaries are determined by their current Jo, M and mass ratio q, the rates of orbital angular momentum loss (dlog Jo/dt) and mass loss (dlog 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 Jo - log M diagram. Evolution of q for a mass...
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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... more
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 dust maps were the main source of extinctions. Unreliable extinctions at low Galactic latitudes |b| ≤ 5° 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–Teff 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...
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Physical dimensions and evolutionary status of the A-type twin binary GSC 4019 3345 are presented. Located at a distance of ~1.1 kpc from the Sun, the system was found to have two components with identical masses (M 1,2 = 1.92 M⊙), radii... more
Physical dimensions and evolutionary status of the A-type twin binary GSC 4019 3345 are presented. Located at a distance of ~1.1 kpc from the Sun, the system was found to have two components with identical masses (M 1,2 = 1.92 M⊙), radii (R 1,2 = 1.76 R⊙), and luminosities (log L 1,2 = 1.1 L⊙) revolving in a circular orbit. Modeling the components with theoretical evolutionary tracks and isochrones implies a young age (t = 280 Myr) for the system, which is bigger than the synchronization time scale but smaller than the circularization time scale. Nevertheless, synthetic spectrum models revealed components’ rotation velocity of V rot12 = 70 km s−1, that is about three times higher than their synchronization velocity. No evidence is found for an age difference between the components.
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A modelling of the sunspot deficit in solar irradiance measurements in 3 spectral wavelengths and the total flux as observed by the VIRGO experiment on SOHO has been performed for several periods of 1996 in a pixel-by-pixel manner using... more
A modelling of the sunspot deficit in solar irradiance measurements in 3 spectral wavelengths and the total flux as observed by the VIRGO experiment on SOHO has been performed for several periods of 1996 in a pixel-by-pixel manner using high resolution photoheliograms taken at Kanzelhöhe Observatory. The calculation of the irradiance contributions of the other features of active regions is
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The last solar activity minimum in 1996 was characterized by several periods without any sunspots or faculae visible on the solar disk. Between these extremely quiet intervals, from time to time a single active region emerged and... more
The last solar activity minimum in 1996 was characterized by several periods without any sunspots or faculae visible on the solar disk. Between these extremely quiet intervals, from time to time a single active region emerged and developed. The passage of these individual active regions across the visible solar hemisphere was accompanied by a pronounced variation in the solar irradiance
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The transformation equations from BVRc to g′r′i′ magnitudes and vice versa for the giants were established from a sample of 80 stars collected from Soubiran et al. (2010) with confirmed surface gravity (2 ⩽ logg (cm s− 2) ⩽ 3) at... more
The transformation equations from BVRc to g′r′i′ magnitudes and vice versa for the giants were established from a sample of 80 stars collected from Soubiran et al. (2010) with confirmed surface gravity (2 ⩽ logg (cm s− 2) ⩽ 3) at effective temperatures 4000 < Teff (K) < 16000. The photometric observations, all sample stars at g′r′i′ and 65 of them at BVRc , were obtained at TÜBİTAK National Observatory (TUG) 1m (T100) telescope, on the Taurus Mountains in Turkey. The MV absolute magnitudes of the giant stars were estimated from the absolute magnitude-temperature data for the giant stars by Sung et al. (2013) using the Teff from the intrinsic colours considered in this study. The transformation equations could be considered to be valid through the ranges of the following magnitudes and colours involved: 7.10 < V 0 < 14.50, 7.30 < g′0…
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High-resolution spectra ($R\sim 48\, 000$) of the massive binary system HH Carinae have been analysed. Precise absolute parameters were derived from a simultaneous solution of the radial velocities and the light curves. The primary... more
High-resolution spectra ($R\sim 48\, 000$) of the massive binary system HH Carinae have been analysed. Precise absolute parameters were derived from a simultaneous solution of the radial velocities and the light curves. The primary component is found to be an O9-type main-sequence star with a temperature of 33 500 K, while the secondary component is a B0-type giant/subgiant star with a temperature of 27 500 K. An analysis of the spectroscopic and photometric data has shown that the primary component rotates at a speed of vrot1 = 220 km s−1, which is three times faster than the synchronous rotation, while the secondary component synchronously rotates with the orbit at a speed of vrot2 = 150 km s−1. The distance to the system and the velocity of the centre of mass are determined as d = 4.6 ± 0.8 kpc and Vγ = –16 km s−1, respectively. The distance of the system is in agreement with the most probable Gaia distance of $4.9^{+0.9}_{-0.7}$ kpc and the distance in the latest data release (D...
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Methods of obtaining stellar luminosities (L) have been revised and a new concept, standard stellar luminosity, has been defined. In this paper, we study three methods: (i) a direct method from radii and effective temperatures; (ii) a... more
Methods of obtaining stellar luminosities (L) have been revised and a new concept, standard stellar luminosity, has been defined. In this paper, we study three methods: (i) a direct method from radii and effective temperatures; (ii) a method using a mass–luminosity relation (MLR); and (iii) a method requiring a bolometric correction. If the unique bolometric correction (BC) of a star extracted from a flux ratio (fV/fBol) obtained from the observed spectrum with sufficient spectral coverage and resolution are used, the third method is estimated to provide an uncertainty (ΔL/L) typically at a low percentage, which could be as accurate as 1 per cent, perhaps more. The typical and limiting uncertainties of the predicted L of the three methods were compared. The secondary methods, which require either a pre-determined non-unique BC or MLR, were found to provide less accurate luminosities than the direct method, which could provide stellar luminosities with a typical accuracy of 8.2–12.2 ...
Arbitrariness attributed to the zero-point constant of the V-band bolometric corrections (BCV) and its relation to ‘bolometric magnitude of a star ought to be brighter than its visual magnitude’ and ‘bolometric corrections must always be... more
Arbitrariness attributed to the zero-point constant of the V-band bolometric corrections (BCV) and its relation to ‘bolometric magnitude of a star ought to be brighter than its visual magnitude’ and ‘bolometric corrections must always be negative’ was investigated. The falsehood of the second assertion became noticeable to us after IAU 2015 General Assembly Resolution B2, where the zero-point constant of bolometric magnitude scale was decided to have a definite value CBol(W) = 71.197 425 ... . Since the zero-point constant of the BCV scale could be written as C2 = CBol − CV, where CV is the zero-point constant of the visual magnitudes in the basic definition BCV = MBol − MV = mbol − mV, and CBol > CV, the zero-point constant (C2) of the BCV scale cannot be arbitrary anymore; rather, it must be a definite positive number obtained from the two definite positive numbers. The two conditions C2 > 0 and 0 < BCV < C2 are also sufficient for LV < L, a similar case to negative...
Using Python 3, astropy and astrometry.net, we have developed a pipeline to obtain photometric light curves of asteroids automatically queried by the SkyBoT database from sequential FITS images. The pipeline provides: pre-reduction of... more
Using Python 3, astropy and astrometry.net, we have developed a pipeline to obtain photometric light curves of asteroids automatically queried by the SkyBoT database from sequential FITS images. The pipeline provides: pre-reduction of data, astrometry, standard differential photometry and light curves by auto-selecting multiple comparison stars (maximum user-defined) from NOMAD catalog via VizieR. The code is an open source, free and hosted on GitHub with the GNU GPL v3 license.
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Radial velocities from 1916.95 to 1991.95 and photometry from l979.25, both published and new in this paper, are presented and analyzed. A new solution of the radial velocity curve reveals a new period of 80.90 days and an eccentricity of... more
Radial velocities from 1916.95 to 1991.95 and photometry from l979.25, both published and new in this paper, are presented and analyzed. A new solution of the radial velocity curve reveals a new period of 80.90 days and an eccentricity of e = 0.05 +/- 0.02, both very different from the 80.17 days and 0.35 found by Abt et al. (1969).
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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 0.008 Z 0.040. Stellar parameters, light ratios, Gaia DR2... more
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 0.008 Z 0.040. Stellar parameters, light ratios, Gaia DR2 trigonomet-ric parallaxes, extinctions and/or reddening were investigated and only 206 systems were selected eligible to calculate empirical bolometric corrections. NASA-IPAC Galac-tic dust maps were main source of extinctions. Unreliable extinctions at low Galactic latitudes |b| 5 o were replaced with individual determinations, if they exist in the literature, else associated systems are discarded. Main-sequence stars of remaining systems were used to calculate bolometric corrections (BC) and to calibrate BC − T ef f relation, which is valid in the range 3100-36000 K. De-reddened (B − V) 0 colours, on the other hand, allowed us to calibrate two intrinsic colour effective temperature relations , where the linear one is valid for T ef f > 10000 K, whil...
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The uniqueness problem in Doppler imaging is discussed. Most of the problem appears to be confusion between different meanings of the word “uniqueness”. According to specific definitions presented in this study, there should not be any... more
The uniqueness problem in Doppler imaging is discussed. Most of the problem appears to be confusion between different meanings of the word “uniqueness”. According to specific definitions presented in this study, there should not be any uniqueness problem.
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The kinematics of 237 chromospherically active binaries (CABs) were studied. The sample is heterogeneous with different orbits and physically different components from F to M spectral-type main-sequence stars to G and K giants and... more
The kinematics of 237 chromospherically active binaries (CABs) were studied. The sample is heterogeneous with different orbits and physically different components from F to M spectral-type main-sequence stars to G and K giants and supergiants. The computed U, V, W space velocities indicate that the sample is also heterogeneous in velocity space. (2 data files).
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We present observations and analysis of a new eclipsing binary HBHA 4705-03. Using decomposition of the light curve into accretion disk and hot spot components, we estimated photometrically the mass ratio of the studied system to be... more
We present observations and analysis of a new eclipsing binary HBHA 4705-03. Using decomposition of the light curve into accretion disk and hot spot components, we estimated photometrically the mass ratio of the studied system to be q=0.62 +-0.07. Other fundamental parameters was found with modeling. This approach gave: white dwarf mass M_1 = (0.8 +- 0.2) M_sun, secondary mass M_2=(0.497 +- 0.05) M_sun, orbital radius a=1.418 R_sun, orbital inclination i = (81.58 +- 0.5) deg, accretion disk radius r_d/a = 0.366 +- 0.002, and accretion rate dot{M} = (2.5 +- 2) * 10^{18}[g/s], (3*10^{-8} [M_sun/yr]). Power spectrum analysis revealed ambiguous low-period Quasi Periodic Oscillations centered at the frequencies f_{1}=0.00076 Hz, f_2=0.00048 Hz and f_3=0.00036 Hz. The B-V=0.04 [mag] color corresponds to a dwarf novae during an outburst. The examined light curves suggest that HBHA 4705-03 is a nova-like variable star.
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ABSTRACT 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 $\leq 3\%$ and luminosities accurate to... more
ABSTRACT 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 $\leq 3\%$ and luminosities accurate to $\leq 30\%$ (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$M_{\odot}$ within the mass range studied of $0.38-32M_{\odot}$. 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 ($L \propto M^{\alpha}$), are shown to be preferable to a single linear, quadratic or cubic equation representing as an alternative MLR. Stellar radius evolution within the main-sequence for stars with $M&gt;1M_{\odot}$ is clearly evident on the M-R diagram, but it is not the 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 $M&gt;1M_{\odot}$ 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 $\sim 6\%$, as long as its observed radius error is adequately small (&lt;1%) and its observed mass error is reasonably small (&lt;6%).
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... Printed in USA SEE ERRATUM. Reliability of Light Curves for Photometric Imaging. ZEKI EKER. King Saud University, College of Science, Department of Astronomy, PO Box 2455, Riyadh 11451, Saudia Arabia. Received 1998 June 30; accepted... more
... Printed in USA SEE ERRATUM. Reliability of Light Curves for Photometric Imaging. ZEKI EKER. King Saud University, College of Science, Department of Astronomy, PO Box 2455, Riyadh 11451, Saudia Arabia. Received 1998 June 30; accepted 1998 August 31. ABSTRACT. ...
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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,... more
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, & Giménez (2010). Distributions of some basic parameters were investigated. The ranges of effective temperatures, masses, and radii are$2\,750<T_{\text{eff}}$(K) < 43000, 0.18 <M/M⊙< 33, and 0.2 <R/R⊙< 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 ...
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Spatial distribution, galactic model parameters and luminosity function of cataclysmic variables (CVs) in the solar neighbourhood have been found using distances estimated from the period-luminosity-colours (PLCs) relation of CVs. It can... more
Spatial distribution, galactic model parameters and luminosity function of cataclysmic variables (CVs) in the solar neighbourhood have been found using distances estimated from the period-luminosity-colours (PLCs) relation of CVs. It can be concluded that exponential function fits better to the observational z-distributions of the whole CVs in the sample, non-magnetic CVs and dwarf novae, while the sech2 function is more appropriate for nova-like stars and polars. The vertical scaleheight of CVs is 158+/-14pc for the 2MASS J band limiting apparent magnitude of 15.8. The discrepancies between the theoretical and observational population studies of CVs can be at least partly removed if the sech2 density function is used in deriving the galactic model parameters. We estimated the vertical scaleheights of 128+/-20pc and 160+/-5pc for dwarf novae and nova-like stars, respectively. The local space density of CVs is found ~3x10-5pc-3 which is in agreement with the lower limit of the theore...