Publications (51)
The Galactic Kinematics of Cataclysmic Variables
T. Ak, S. Bilir, A. Ãzdönmez +5
Kinematical properties of CVs were investigated according to population types and orbital periods, using the space velocities computed from recently updated systemic velocities, pr…
An Improved Metallicity Calibration with UBV Photometry
S. Karaali, S. Bilir, S. Ak +2
We used the data of 701 stars covering the colour index interval 0.32<B-V<=1.16, with metallicities -1.76<=[Fe/H]<=+0.40 dex, which were taken from PASTEL catalogue and estimated m…
Local stellar kinematics from RAVE data: II. Radial Metallicity Gradient
B. Coskunoglu, S. Ak, S. Bilir +5
We investigate radial metallicity gradients for a sample of dwarf stars from the RAdial Velocity Experiment (RAVE) Data Release 3 (DR3). We select a total of approximately 17000 F-…
Luminosity-Colours relations for thin disc main-sequence stars
S. Bilir, S. Karaali, S. Ak +3
In this study we present the absolute magnitude calibrations of thin disc main-sequence stars in the optical (), and in the near-infrared (). Thin disc stars are iden…
Colour Transformations between BVRc and g'r'i' Photometric Systems for Giant Stars
S. Ak, T. Ak, S. Karaali +9
The transformation equations from to magnitudes and vice versa for the giants were established from a sample of 80 stars collected from Soubiran et al. (2010) with…
A Multi-Data Approach to Open Clusters: Roslund 3 and Ruprecht 174 in CCD UBV and Gaia DR3 Context
H. Karagoz, T. Yontan, S. Bilir +5
A detailed analysis of the structural, astrophysical, kinematic, and dynamical properties of the open clusters Roslund 3 and Ruprecht1 74 is carried out using CCD UBV photometry in…
Local Stellar Kinematics from RAVE data - VI. Metallicity Gradients Based on the F-G Main-sequence Stars
O. Plevne, T. Ak, S. Karaali +3
We estimated iron and metallicity gradients in the radial and vertical directions with the F and G type dwarfs taken from the RAVE DR4 database. The sample defined by the constrain…
First identification and absolute magnitudes of the red clump stars in the Solar neighbourhood for WISE
E. Yaz Gokce, S. Bilir, N. D. Ozturkmen +4
We present the first determination of absolute magnitudes for the red clump (RC) stars with the Wide-field Infrared Survey Explorer (WISE). We used recently reduced parallaxes take…
Local Stellar Kinematics from RAVE data - VII. Metallicity Gradients from Red Clump Stars
O. Onal Tas, S. Bilir, G. M. Seabroke +4
We investigate the Milky Way Galaxy's radial and vertical metallicity gradients using a sample of 47,406 red clump stars from the RAVE DR4. This sample is more than twice the size…
A new absolute magnitude calibration with 2MASS for cataclysmic variables
T. Ak, S. Bilir, S. Ak +1
Using reliable trigonometric measurements, we find that the absolute magnitude of cataclysmic variables depends on the orbital period and de-reddened and $(H-K_{s})_{0}…
Galactic longitude dependent Galactic model parameters
S. Bilir, S. Karaali, S. Ak +2
We present the Galactic model parameters for thin disc estimated by Sloan Digital Sky Survey (SDSS) data of 14 940 stars with apparent magnitudes in six intermedia…
The metallicity distributions in high-latitudes with SDSS
S. Ak, S. Bilir, S. Karaali +2
We present metallicities and their variations with different parameters for 36 high-latitude fields covering Galactic longitudes 0<l<360. The metallicities for relatively short ver…
Vertical and radial metallicity gradients in high latitude galactic fields with SDSS
S. Tuncel Guctekin, S. Bilir, S. Karaali +2
We used the ugr magnitudes of 1,437,467 F-G type main-sequence stars with metal abundance -2<[Fe/H]<+0.2 dex and estimated radial and vertical metallicity gradients for high Galact…
Local Stellar Kinematics from RAVE Data: I. Local Standard of Rest
B. Coskunoglu, S. Ak, S. Bilir +19
We analyze a sample of 82850 stars from the RAVE survey, with well-determined velocities and stellar parameters, to isolate a sample of 18026 high-probability thin-disc dwarfs with…
Estimation of Galactic model parameters with the SDSS and metallicity distribution in two fields in the anti-centre direction of the Galaxy
S. Ak, S. Bilir, S. Karaali +1
We estimated the Galactic model parameters from the SDSS data reduced for two fields in the anti-centre direction of the Galaxy, , and symmetric relative to the Galacti…
A study of the Czernik 2 and NGC 7654 open clusters using CCD UBV photometric and Gaia EDR3 data
B. Akbulut, S. Ak, T. Yontan +5
We analysed the open clusters Czernik 2 and NGC 7654 using CCD UBV photometric and Gaia Early Data Release 3 (EDR3) photometric and astrometric data. Structural parameters of the t…
Local stellar kinematics from RAVE data: IV. Solar neighbourhood age-metallicity relation
S. Duran, S. Ak, S. Bilir +4
We investigated the age-metallicity relation using a sample of 5691 F and G type dwarfs from RAVE DR3 by applying several constraints: i) We selected stars with surface gravities l…
Transformations between 2MASS, SDSS and BVI photometric systems for late-type giants
E. Yaz, S. Bilir, S. Karaali +3
We present colour transformations from Two Micron All Sky Survey (2MASS) photometric system to Johnson-Cousins system and to Sloan Digital Sky Survey (SDSS) system for late-type gi…
Estimation of galactic model parameters in high latitudes with SDSS
S. Bilir, A. Cabrera-Lavers, S. Karaali +3
We estimated the Galactic model parameters for a set of 36 high-latitude fields included in the currently available Data Release 5 (DR 5) of the Sloan Digital Sky Survey ({\em SDSS…
Metallicity Calibration and Photometric Parallax Estimation: II. SDSS photometry
S. Tuncel Guctekin, S. Bilir, S. Karaali +4
We used the updated [Fe/H] abundances of 168 F-G type dwarfs and calibrated them to a third order polynomial in terms of reduced ultraviolet excess, defined with …
A photometric and astrometric study of the open clusters NGC 1664 and NGC 6939
S. Koc, T. Yontan, S. Bilir +5
This study calculated astrophysical parameters, as well as kinematic and galactic orbital parameters, of the open clusters NGC 1664 and NGC 6939. The work is based on CCD UBV and G…
Spatial distribution and galactic model parameters of cataclysmic variables
T. Ak, S. Bilir, S. Ak +1
The spatial distribution, galactic model parameters and luminosity function of cataclysmic variables (CVs) in the solar neighbourhood have been determined from a carefully establis…
A comprehensive study of the open cluster NGC 6866
Z. F. Bostanci, T. Ak, T. Yontan +15
We present CCD photometry of the field of the open cluster NGC 6866. Structural parameters of the cluster are determined utilizing the stellar density profile of the stars…
Estimation of Galactic model parameters in high latitudes with 2MASS
A. Cabrera-Lavers, S. Bilir, S. Ak +2
In this paper, we try to find any dependence of the Galactic structural parameters with the Galactic longitude for either the thin disc or the thick disc of the Milky Way, that wou…
CCD UBV photometric and Gaia astrometric study of eight open clusters- ASCC 115, Collinder 421, NGC 6793, NGC 7031, NGC 7039, NGC 7086, Roslund 1 and Stock 21
T. Yontan, S. Bilir, Z. F. Bostanci +8
In this study, we carried out CCD UBV photometry of eight open clusters, ASCC 115, Collinder 421, NGC 6793, NGC 7031, NGC 7039, NGC 7086, Roslund 1, Stock 21, and determined their…
CCD UBV Photometry and Kinematics of the Open Cluster NGC 225
S. Bilir, Z. F. Bostanci, T. Yontan +6
We present the results of CCD photometric and spectroscopic observations of the open cluster NGC 225. In order to determine the structural parameters of NGC 225, we calculate…
The age of cataclysmic variables: a kinematical study
T. Ak, S. Bilir, S. Ak +2
Using available astrometric and radial velocity data, the space velocities of cataclysmic variables (CVs) with respect to Sun were computed and kinematical properties of various su…
Metallicity and absolute magnitude calibrations for F-G type main-sequence stars in the Gaia era
M. Celebi, S. Bilir, S. Ak +3
In this study, photometric metallicity and absolute magnitude calibrations were derived using F-G spectral type main-sequence stars in the Solar neighbourhood with precise spectros…
Identification of field dwarfs and giants in RAVE
S. Bilir, S. Karaali, S. Ak +3
The second RAdial Velocity Experiment (RAVE) Data Release (DR2) derives log g values but we present a simpler and cleaner method of identifying dwarfs and giants using only magnitu…
The Age-Metallicity Relation in the Solar Neighbourhood
S. Doner, S. Ak, O. Onal Tas +1
Age-metallicity relation for the Galactic disc is a crucial tool and to constrain the Galactic chemical evolution models. We investigate the age-metallicity relation of the Galacti…
Solar Space Density of the Red Clump Stars and the Scale-length of the Thin Disc
E. Yaz Gokce, S. Karaali, S. Duran +6
We estimated the scale-length of the thin disc with the J and W1 magnitudes of the most probable Red Clump (RC) stars in the Galactic plane, $-0\overset{^\circ}.5 \leq b \leq +0\ov…
Transformations between WISE and 2MASS, SDSS, BVI photometric systems: II. Transformation equations for red clump stars
S. Bilir, S. Karaali, N. D. Dagtekin +4
We present colour transformations for the conversion of the Wide-Field Survey Explorer (WISE) W1, W2, and W3 magnitudes to the Johnson-Cousins (BVIc), Sloan Digital Sky Survey (gri…
Transformations between 2MASS, SDSS and BVRI photometric systems: bridging the near infrared and optical
S. Bilir, S. Ak, S. Karaali +3
We present colour transformations for the conversion of the {\em 2MASS} photometric system to the Johnson-Cousins system and further into the {\em SDSS} system. We…
Extragalactic Objects in Basle Fields
S. Bilir, Y. Karatas, S. Ak
We discriminated the extragalactic objects (galaxies and quasars) from stars for Basle star fields, Plaut I, SA 54, and SA 82 by comparison of Basle fields and APS POSS I finder ch…
A New Procedure for the Photometric Parallax Estimation
S. Karaali, Y. Karatas, S. Bilir +2
We present a new procedure for photometric parallax estimation. The data for 1236 stars provide calibrations between the absolute magnitude offset from the Hyades main-sequence and…
CCD UBV photometric study of five open clusters - Dolidze 36, NGC 6728, NGC 6800, NGC 7209 and Platais 1
Z. F. Bostanci, T. Yontan, S. Bilir +9
In this study, we present CCD UBV photometry of poorly studied open star clusters, Dolidze 36, NGC 6728, NGC 6800, NGC 7209, and Platais 1, located in the first and second Galactic…
CCD UBV photometry of the open cluster NGC 6819
T. Ak, Z. F. Bostanci, T. Yontan +5
We present the results of CCD UBV observations of the open cluster NGC 6819. We calculated the stellar density profile in the cluster's field to determine the structural parameters…
Local stellar kinematics from RAVE data: III. Radial and Vertical Metallicity Gradients based on Red Clump Stars
S. Bilir, S. Karaali, S. Ak +5
We investigate radial and vertical metallicity gradients for a sample of red clump stars from the RAdial Velocity Experiment (RAVE) Data Release 3. We select a total of 6781 stars,…
Transformations between WISE, 2MASS, SDSS and BVRI photometric systems: I. Transformation equations for dwarfs
S. Bilir, S. Karaali, S. Ak +5
We present colour transformations for the conversion of the W1 and W2 magnitudes of WISE photometric system to the Johnson-Cousins' BVRI, SDSS (gri), and 2MASS (JHK_s) photometric…
SDSS Absolute Magnitudes for Thin Disc Stars based on Trigonometric Parallaxes
S. Bilir, S. Karaali, S. Ak +3
We present a new luminosity-colour relation based on trigonometric parallaxes for thin disc main-sequence stars in SDSS photometry. We matched stars from the newly reduced Hipparco…
A Chandra X-ray Study of Supernova Remnant N63A in the Large Magellanic Cloud
E. Karagoz, N. Alan, S. Bilir +1
We perform extensive spectroscopy of the supernova remnant N63A in the Large Magellanic Cloud, using ks {\it Chandra} archival data. By analysing the spectra of the entir…
Population types of cataclysmic variables in the solar neighbourhood
T. Ak, S. Bilir, T. Guver +2
The Galactic orbital parameters of 159 cataclysmic variables in the Solar neighbourhood are calculated, for the first time, to determine their population types using published kine…
CCD UBV and Gaia DR3 Analyses of Open Clusters King 6 and NGC 1605
S. Gokmen, Z. Eker, T. Yontan +5
A detailed analysis of ground-based CCD UBV photometry and space-based Gaia Data Release 3 (DR3) data for the open clusters King 6 and NGC 1605 was performed. Using the pyUPMASK al…
A Study of Open Clusters Frolov 1 and NGC 7510 using CCD UBV Photometry and Gaia DR2 Astrometry
T. Yontan, S. Bilir, T. Ak +6
We present reddening, photometric metallicity, age and distance estimates for the Frolov 1 and NGC 7510 open clusters based on CCD UBV photometric and Gaia data. Photometric observ…
Local stellar kinematics from RAVE data- V. Kinematic investigation of the Galaxy with red clump stars
S. Karaali, S. Bilir, S. Ak +3
We investigated the space velocity components of 6610 red clump (RC) stars in terms of vertical distance, Galactocentric radial distance and Galactic longitude. Stellar velocity ve…
CCD BV and 2MASS photometric study of the open cluster NGC 1513
S. Bilir, T. Guver, I. Khamitov +5
We present CCD BV and JHK 2MASS photometric data for the open cluster NGC 1513. We observed 609 stars in the direction of the cluster up to a limiting magnitude of …
A Comprehensive Study of Czernik 41 and NGC 1342 Using CCD UBV and Gaia DR3 Data
B. Tanik Ozturk, S. Bilir, T. Yontan +5
In this study, the structural, astrophysical, kinematic, and Galactic orbital parameters of the open clusters Czernik 41 and NGC 1342, as well as their dynamical evolution, are inv…
Metallicity Calibration and Photometric Parallax Estimation: I. UBV photometry
S. Tuncel Guctekin, S. Bilir, S. Karaali +3
We present metallicity and photometric parallax calibrations for the F and G type dwarfs with photometric, astrometric and spectroscopic data. The sample consists of 168 dwarf star…
A New Absolute Magnitude Calibration for Red Clump Stars
S. Bilir, T. Ak, S. Ak +2
We present an M_V absolute magnitude calibration including the B-V colour and [Fe/H] metallicity for the red clump stars in the globular and open clusters with a wide range of meta…
Bridging the Ultraviolet and Optical Regions: Transformation Equations between {\it GALEX} and {\it UBV} Photometric Systems
S. Bilir, N. Alan, S. Tuncel Guctekin +6
We derive transformation equations between GALEX and UBV colours by using the reliable data of 556 stars. We present two sets of equations; as a function of (only) luminosity class…
CCD UBVRI photometry of NGC 6811
T. Yontan, S. Bilir, Z. F. Bostancı +6
We present the results of CCD UBVRI observations of the open cluster NGC 6811 obtained on 18th July 2012 with the 1m telescope at the TÃBÄ°TAK National Observatory (TUG). Using th…