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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 observations were collected using the 1-m telescope of the T\"UB\.ITAK National Observatory. Gaia DR2 proper motion data in the direction of two groupings were used to identify cluster membership. We determined mean proper motion values ($ \mu_{\alpha}\cos\delta, \mu_{\delta}$) = ($-3.02\pm 0.10$, $-1.75 \pm 0.08$) and ($-3.66 \pm 0.07$, $-2.17 \pm 0.06$) mas yr$^{-1}$ for Frolov 1 and NGC 7510, respectively. We used two-colour diagrams to obtain $E(B-V)$ colour excesses for Frolov 1 and NGC 7510 as $0.65\pm0.06$ and $1.05\pm0.05$ mag, respectively. We derived the photometric metallicity of Frolov 1 as [Fe/H] = 0.03$\pm$0.03 dex and adopted a solar metallicity for NGC 7510. Based on these reddening and metallicities we determined the distance moduli and ages of the clusters via fitting PARSEC isochrones to the cluster colour-magnitude diagrams. Isochrone fitting distances for Frolov 1 and NGC 7510 are $2864 \pm 254$ and $2818 \pm 247$ pc, respectively, which correspond to the ages $35\pm 10$ Myr and $18\pm 6$ Myr. We also calculated mean Gaia distances and compared them with those given in the literature and in this study, concluding that our results are in good agreement with previous work. Finally, we calculated the mass function slopes as being $X=-1.21\pm0.18$ for Frolov 1 and $X=-1.42\pm0.27$ for NGC 7510., Comment: 17 pages, including 12 figures and 8 tables, accepted for publication in Astronomische Nachrichten

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 spectroscopic, photometric and Gaia astrometric data for UBV photometry. The sample consists of 504 main-sequence stars covering the temperature, surface gravity and colour index intervals $5300 4$ (cgs) and $0.3<(B-V)_0<0.8$ mag, respectively. Stars with relative trigonometric parallax errors $\sigma_{\pi}/\pi\leq0.01$ were preferred from Gaia DR2 data for the estimation of their $M_V$ absolute magnitudes. In order to obtain calibrations, $(U-B)_0$ and $(B-V)_0$ colour indices of stars were preferred and a multi-variable second order equation was used. Calibrations are valid for main-sequence stars in the metallicity and absolute magnitude ranges $-2<{\rm [Fe/H]}<0.5$ dex and $2.5

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 reddening, metallicity, distance, age, and mass functions. We used new Gaia Data Release 2 (DR2) astrometric data to separate cluster member stars from the field stars and obtain precise structural and astrophysical parameters. To identify cluster member stars we utilized an unsupervised membership assignment code (UPMASK), which is based on the photometric and astrometric data. The density distributions for the open clusters show good fits with the empirical King model except for Roslund 1 and Stock 21 not having central concentration. The colour excesses and metallicities were derived separately using U-B vs B-V two-colour diagrams. Keeping these parameters as constants, we simultaneously calculated distance moduli and ages of the clusters from V vs B-V and V vs U-B colour-magnitude diagrams using PARSEC theoretical isochrones. Taking into account Gaia DR2 proper motion components and parallaxes of the member stars, we also calculated mean proper motions and distances for the clusters. Distances derived both from isochrone fitting to colour-magnitude diagrams of the clusters and Gaia DR2 trigonometric parallaxes are compatible with each other. Slopes of the mass functions of the eight open clusters are in good agreement with Salpeter (1955) value of 1.35., Comment: 24 pages, 12 figures and 7 tables, accepted for publication in Astrophysics and Space Science

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 quadrants. Observations were obtained with T100, the 1-m telescope of the TUBITAK National Observatory. Using photometric data, we determined several astrophysical parameters such as reddening, distance, metallicity and ages and from them, initial mass functions, integrated magnitudes and colours. We took into account the proper motions of the observed stars to calculate the membership probabilities. The colour excesses and metallicities were determined independently using two-colour diagrams. After obtaining the colour excesses of the clusters Dolidze 36, NGC 6728, NGC 6800, NGC 7209, and Platais 1 as $0.19\pm0.06$, $0.15\pm0.05$, $0.32\pm0.05$, $0.12\pm0.04$, and $0.43\pm0.06$ mag, respectively, the metallicities are found to be $0.00\pm0.09$, $0.02\pm0.11$, $0.03\pm0.07$, $0.01\pm0.08$, and $0.01\pm0.08$ dex, respectively. Furthermore, using these parameters, distance moduli and age of the clusters were also calculated from colour-magnitude diagrams simultaneously using PARSEC theoretical models. The distances to the clusters Dolidze 36, NGC 6728, NGC 6800, NGC 7209, and Platais 1 are $1050\pm90$, $1610\pm190$, $1210\pm150$, $1060\pm 90$, and $1710\pm250$ pc, respectively, while corresponding ages are $400\pm100$, $750\pm150$, $400\pm100$, $600\pm100$, and $175\pm50$ Myr, respectively. Our results are compatible with those found in previous studies. The mass function of each cluster is derived. The slopes of the mass functions of the open clusters range from 1.31 to 1.58, which are in agreement with Salpeter's initial mass function. We also found integrated absolute magnitudes varying from -4.08 to -3.40 for the clusters., Comment: 17 pages, 9 figures and 8 tables, accepted for publication in Astrophysics and Space Science

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, $\delta_{0.41}$ defined with $ugr$ data in the SDSS. We estimated the $M_g$ absolute magnitudes for the same stars via the re-reduced Hipparcos parallaxes and calibrated the absolute magnitude offsets, $\Delta M_g$, relative to the intrinsic sequence of Hyades to a third order polynomial in terms of $\delta_{0.41}$. The ranges of the calibrations are $-2<$[Fe/H]$\leq$0.3 dex and $418$ mag)., Comment: Eq. 11 was corrected, results and conclusions are the same. 16 pages, 16 figures and 5 tables, accepted for publication in Astrophysics and Space Science

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 of the largest sample in the literature investigating radial and vertical metallicity gradients. The absolute magnitude of Groenewegen (2008) is used to determine distances to our sample stars. The resulting distances agree with the RAVE DR4 distances Binney et al. (2014) of the same stars. Our photometric method also provides distances to 6185 stars that are not assigned a distance in RAVE DR4. The metallicity gradients are calculated with their current orbital positions ($R_{gc}$ and $Z$) and with their orbital properties (mean Galactocentric distance, $R_{m}$ and $z_{max}$), as a function of the distance to the Galactic plane: d[Fe/H]/d$R_{gc}=$-$0.047\pm0.003$ dex/kpc for $0\leq |Z|\leq0.5$ kpc and d[Fe/H]/d$R_m=$-$0.025\pm0.002$ dex/kpc for $0\leq z_{max}\leq0.5$ kpc. This reaffirms the radial metallicity gradient in the thin disc but highlights that gradients are sensitive to the selection effects caused by the difference between $R_{gc}$ and $R_{m}$. The radial gradient is flat in the distance interval 0.5-1 kpc from the plane and then becomes positive greater than 1 kpc from the plane. The radial metallicity gradients are also eccentricity dependent. We showed that d[Fe/H]/d$R_m=$-$0.089\pm0.010$, -$0.073\pm0.007$, -$0.053\pm0.004$ and -$0.044\pm0.002$ dex/kpc for $e_p\leq0.05$, $e_p\leq0.07$, $e_p\leq0.10$ and $e_p\leq0.20$ sub-samples, respectively, in the distance interval $0\leq z_{max}\leq0.5$ kpc. Similar trend is found for vertical metallicity gradients. Both the radial and vertical metallicity gradients are found to become shallower as the eccentricity of the sample increases. These findings can be used to constrain different formation scenarios of the thick and thin discs., Comment: 18 pages, including 16 figures and 6 tables, accepted for publication in PASA

We present the results of CCD $UBV$ photometric and spectroscopic observations of the open cluster NGC 225. In order to determine the structural parameters of NGC 225, we calculated the stellar density profile in the cluster's field. We estimated the probabilities of the stars being physical members of the cluster using the existing astrometric data. The most likely members of the cluster were used in the determination of the astrophysical parameters of the cluster. We calculated the mean radial velocity of the cluster as $V_{r}=-8.3\pm 5.0$ km s$^{-1}$ from the optical spectra of eight stars in the cluster's field. Using the U-B vs B-V two-colour diagram and UV excesses of the F-G type main-sequence stars, the reddening and metallicity of NGC 225 were inferred as $E(B-V)=0.151\pm 0.047$ mag and $[Fe/H]=-0.11\pm 0.01$ dex, respectively. We fitted the colour-magnitude diagrams of NGC 225 with the PARSEC isochrones and derived the distance modulus, distance and age of the cluster as $\mu_{V}=9.3\pm 0.07$ mag, d=585$\pm$20 pc and $t=900\pm 100$ Myr, respectively. We also estimated the galactic orbital parameters and space velocity components of the cluster and found that the cluster has a slightly eccentric orbit of $e=0.07\pm 0.01$ and an orbital period of $P_{orb}= 255\pm 5$ Myr., Comment: 34 pages, 13 figures and 7 tables, accepted for publication in Advances in Space Research. arXiv admin note: text overlap with arXiv:1603.00474, arXiv:1507.05968

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 stars covering the colour, iron abundance and absolute magnitude intervals $0.30<(B-V)_0<0.68$ mag, $-2.0<[Fe/H]<0.4$ dex and $3.4

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 of NGC 6819. Using the existing astrometric data, we calculated the probabilities of the stars being physical members of the cluster, and used these objects in the determination of the astrophysical parameters of NGC 6819. We inferred the reddening and metallicity of the cluster as $E(B-V)=0.130\pm0.035$ mag and $[Fe/H]=+0.051\pm 0.020$ dex, respectively, using the U-B vs B-V two-colour diagram and UV excesses of the F-G type main-sequence stars. We fit the colour-magnitude diagrams of NGC6819 with the PARSEC isochrones and derived the distance modula, distance and age of the cluster as $\mu_{V}=12.22\pm 0.10$ mag, $d=2309\pm106$ pc and $t=2.4\pm0.2$ Gyr, respectively. The parameters of the galactic orbit estimated for NGC 6819 indicate that the cluster is orbiting in a slightly eccentric orbit of $e=0.06$ with a period of $P_{orb}=142$ Myr. The slope of the mass function estimated for the cluster is close to the one found for the stars in the solar neighbourhood., Comment: 17 pages, 15 figures and 9 tables, accepted for publication in Astrophysics and Space Science. arXiv admin note: substantial text overlap with arXiv:1507.05968

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 constraints Zmax<=825 pc and ep<=0.10 consists of stars with metal abundances and space velocity components agreeable with the thin-disc stars. The radial iron and metallicity gradients estimated for the vertical distance intervals 08 kpc. The range of the iron and metallicity abundance for the F and G type dwarfs on elongated orbits, [-0.13, -0.01), is similar to the thin-disc stars, while at least half of their space velocity components agree better with those of the thick-disc stars. The vertical iron gradients estimated for the F and G type dwarfs on circular orbits are d[Fe/H]/dZmax=-0.176(0.039) dex/kpc and d[Fe/H]/dZmax=-0.119(0.036) dex/kpc for the intervals Zmax<= 825 and Zmax<=1500 pc, respectively., Comment: 16 pages, including 11 figures and 5 tables, accepted for publication in PASA

We present CCD $UBVRI$ 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 in the field. We calculate the probabilities of the stars being a physical member of the cluster using their astrometric data and perform further analyses using only the most probable members. The reddening and metallicity of the cluster were determined by independent methods. The LAMOST spectra and the ultraviolet excess of the F and G type main-sequence stars in the cluster indicate that the metallicity of the cluster is about the solar value. We estimated the reddening $E(B-V)=0.074 \pm 0.050$ mag using the $U-B$ vs $B-V$ two-colour diagram. The distance modula, the distance and the age of NGC 6866 were derived as $\mu = 10.60 \pm 0.10$ mag, $d=1189 \pm 75$ pc and $t = 813 \pm 50$ Myr, respectively, by fitting colour-magnitude diagrams of the cluster with the PARSEC isochrones. The Galactic orbit of NGC 6866 indicates that the cluster is orbiting in a slightly eccentric orbit with $e=0.12$. The mass function slope $x=1.35 \pm 0.08$ was derived by using the most probable members of the cluster., Comment: 14 pages, including 16 figures and 7 tables, accepted for publication in MNRAS. Table 4 in the manuscript will be published electronically

Some short GRBs are followed by longer extended emission, lasting anywhere from ~10 to ~100 s. These short GRBs with extended emission (EE) can possess observational characteristics of both short and long GRBs (as represented by GRB 060614), and the traditional classification based on the observed duration places some of them in the long GRB class. While GRBs with EE pose a challenge to the compact binary merger scenario, they may therefore provide an important link between short and long duration events. To identify the population of GRBs with EE regardless of their initial classifications, we performed a systematic search of short GRBs with EE using all available data (up to February 2013) of both Swift/BAT and Fermi/GBM. The search identified 16 BAT and 14 GBM detected GRBs with EE, several of which are common events observed with both detectors. We investigated their spectral and temporal properties for both the spikes and the EE, and examined correlations among these parameters. Here we present the results of the systematic search as well as the properties of the identified events. Finally, their properties are also compared with short GRBs with EE observed with BATSE, identified through our previous search effort. We found several strong correlations among parameters, especially when all of the samples were combined. Based on our results, a possible progenitor scenario of two-component jet is discussed., Comment: Published in MNRAS; matched to the published version

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 T\"UB\.ITAK National Observatory (TUG). Using these photometric results, we determine the structural and astrophysical parameters of the cluster. The mean photometric uncertainties are better than 0.02 mag in the V magnitude and B-V, V-R, and V-I colour indices to about 0.03 mag for U-B among stars brighter than magnitude V=18. Cluster member stars were separated from the field stars using the Galaxia model of Sharma et al. (2011) together with other techniques. The core radius of the cluster is found to be $r_{c}$=3.60 arcmin. The astrophysical parameters were determined simultaneously via Bayesian statistics using the colour-magnitude diagrams V versus B-V, V versus V-I, V versus V-R, and V versus R-I of the cluster. The resulting most likely parameters were further confirmed using independent methods, removing any possible degeneracies. The colour excess, distance modulus, metallicity and the age of the cluster are determined simultaneously as E(B-V)=0.05$\pm$0.01 mag, $\mu=10.06\pm0.08$ mag, [M/H]=-0.10$\pm$0.01 dex and t=1.00$\pm$0.05 Gyr, respectively. Distances of five red clump stars which were found to be members of the cluster further confirm our distance estimation., Comment: 22 pages, 13 figures and 9 tables, accepted for publication in Astrophysics and Space Science

In the present work, we study the periodicities of oscillations in dark fine structures using observations of a network and a semi-active region close to the solar disk center. We simultaneously obtained spatially high resolution time series of white light images and narrow band images in the H$\alpha$ line using the 2D G\"ottingen spectrometer, which were based on two Fabry-Perot interferometers and mounted in the VTT/Observatorio del Teide/Tenerife. During the observations, the H$\alpha$ line was scanned at 18 wavelength positions with steps of 125 m\AA. We computed series of Doppler and intensity images by subtraction and addition of the H$\alpha$ $\pm$ 0.3 \AA\ and $\pm$ 0.7 \AA\ pairs, sampling the upper chromosphere and the upper photosphere, respectively. Then we obtained power, coherence and phase difference spectra by performing a wavelet analysis to the Doppler fluctuations. Here, we present comparative results of oscillatory properties of dark fine structures seen in a network and a semi-active region., Comment: 8 pages, 5 figures, accepted for publication in MNRAS

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 log g < 3.8 and effective temperatures in the 5310

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 metallicities: M_V = 0.627(0.104)(B-V)o+0.046(0.043)[Fe/H]+0.262(0.111). The calibration equation is valid in the ranges 0.42<(B-V)o<1.20 mag, -1.55<[Fe/H]<+0.40 dex and 0.43

In this paper, we analyze the physical properties of dark mottles in the chromospheric network using two dimensional spectroscopic observations in H-alpha obtained with the Gottingen Fabry-Perot Spectrometer in the Vacuum Tower Telescope at the Observatory del Teide, Tenerife. Cloud modeling was applied to measure the mottles' optical thickness, source function, Doppler width, and line of sight velocity. Using these measurements, the number density of hydrogen atoms in levels 1 and 2, total particle density, electron density, temperature, gas pressure, and mass density parameters were determined with the method of Tsiropoula & Schmieder (1997). We also analyzed the temporal behaviour of a mottle using cloud parameters. Our result shows that it is dominated by 3 minute signals in source function, and 5 minutes or more in velocity., Comment: 6 pages, 5 figures, accepted for publication in Astronomische Nachrichten - Astronomical Notes

We present chromospheric cloud modeling on the basis of H-alpha profile-sampling images taken with the Interferometric Bidimensional Spectrometer (IBIS) at the Dunn Solar Telescope (DST). We choose the required reference background profile by using theoretical NLTE profile synthesis. The resulting cloud parameters are converted into estimates of physical parameters (temperature and various densities). Their mean values compare well with the VAL-C model., Comment: 4 pages, 4 figures. To appear in the proceedings of the 25th NSO Workshop "Chromospheric Structure and Dynamics. From Old Wisdom to New Insights", Memorie della Societa' Astronomica Italiana, Eds. Tritschler et al