CCD Photometric Study Research Articles

A NEW VISIT TO THE VARIABLE STARS IN M56 AND ITS COLOUR-MAGNITUDE DIAGRAM STRUCTURE

We present a VI CCD photometric study and a membership analysis of the globular cluster M56 (NGC 6779). This produced a CMD decontaminated from field stars, which enabled a better confrontation with theoretical isochrones, zero-age horizontal branches (ZAHB) and post-ZAHB evolutionary tracks. Post He-flash evolutionary models with a He-core mass of 0.5 Mʘ and envelopes of 0.04 - 0.18 Mʘ, cover the complete horizontal branch. Models with total mass ≈ 0.68 Mʘ explain the RR Lyrae, while those with a mass ≈ 0.56 Mʘ and a very subtle envelope, explain the Pop II cepheids with a progenitor in the blue tail of the HB. Based on the Fourier decomposition of the V light curve of a single cluster member RRc star, we determined a metallicity of [Fe/H]ZW = −1.96 ± 0.09. Several independent distance determination approaches lead to a mean distance to M56 of ⟨d⟩ = 9.4 ± 0.4 kpc. Finally, we report 5 new variables: one SX Phe, three EB, and one Rrc.

Observational and Theoretical Studies of 27 δ Scuti Stars with Investigation of the Period–Luminosity Relation

The multi-color CCD photometric study of 27 δ Scuti stars is presented. By using approximately three years of photometric observations, we obtained the times of maxima and magnitude changes during the observation time interval for each star. The ephemerides of our δ Scuti stars were calculated based on the Markov Chain Monte Carlo (MCMC) method using the observed times of maxima and the period of the stars’ oscillations. We used the Gaia EDR3 parallaxes to calculate the luminosities and also the absolute magnitudes of these δ Scuti stars. The fundamental physical parameters of all the stars in our sample such as masses and radii were estimated. We determined the pulsation modes of the stars based on the pulsation constants. Moreover, the period–luminosity (P–L) relation of δ Scuti stars was investigated and discussed. Then, by using a machine learning classification, new P–L relations for fundamental and overtone modes are presented.

The first CCD photometric study of the open cluster NGC 744

We present the first CCD photometric observations of open cluster NGC 744, as part of the 50BiN Open Cluster Survey. The color-magnitude diagrams of this cluster were derived from absolute BV RI photometry on a good photometric night. A brief isochrone fitting gives a distance modulus of (m − M)V = 11.58 ± 0.2 and a reddening of E(B − V) = 0.35 ± 0.05 with an age of log t = 8.30 ± 0.05. By carefully examining the BV time-series data, we discovered four new variable stars in a 20′ × 20′ field around the cluster. We classified them as three eclipsing binary stars and one δ Scuti pulsating star, mainly based on the light-curve shape, the detected periods and the positions on the color-magnitude diagrams.

Kottamia 74-inch telescope discovery of the new eclipsing binary 2MASS J20004638 + 0547475.: First CCD photometry and light curve analysis

A CCD photometric study is presented for the eclipsing binary system 2MASS J20004638+ 0547475. Observations of the system were obtained in the V, R and I colours with the 2Kx2K CCD attached to 1.88m Kottamia Optical Telescope. New times of light minimum and new ephemeris were obtained. The V, R and I light curves were analyzed using the PHOEBE 0.31 program to determine geometrical and physical parameters of the system. The results show that 2MASS J20004638+ 0547475, is A-Type WUMa and is an overcontact binary with high fill-out factor= 69%. The current evolutionary status of the system indicates that the primary component lies very close to the main sequence while the secondary is evolved. The asymmetric maxima were studied and a modeling of the hot spot parameters is given.

UBVI photometric study of open star clusters Ruprecht 25 and Czernik 6

We present a UBVI CCD photometric study of two open star clusters Ruprecht 25 and Czernik 6 using the data taken with 104-cm Sampurnanand telescope, ARIES, Nainital, India. The optical CCD data for these clusters are obtained for the first time. The clusters radii are found to be 2′.4 and 1′.5. Using two colour (U−B) versus (B−V) diagram we have estimated the reddening as E(B−V)=0.55± 0.05 mag for Ruprecht 25 and 0.48 ± 0.05 mag for Czernik 6, while the corresponding distances are 5.8 ± 0.5 and 5.0 ± 0.3 kpc. Ages of 800 ± 80 Myr for Ruprecht 25 and 40 ± 10 Myr for Czernik 6 are determined using the stellar isochrones of metallicity Z=0.019. We have also determined the relaxation time for the clusters Ruprecht 25 and Czernik 6. Our analysis indicates that both clusters are dynamically relaxed. This may be due to the dynamical evolution or imprint of star formation itself or both.

A CCD photometric study of the newly discovered short period eclipsing binary 1SWASP J210318.76 + 021002.2

We present a CCD photometric study for the newly discovered short period eclipsing binary 1SWASP J210318.76+021002.2 using BVRI observations carried out on 8 Sept. 2013 using Kottamia optical telescope at NRIAG, Egypt. The observed light curves were analyzed using Willson–Devinney code. The accepted solution shows that the primary star is more massive and hotter than the secondary with about 72K and has a hot spot with temperature factor about 1.25. The system is at a distance of 710±29 pc. Evolutionary state of the system is investigated using stellar models.

CCD photometric study of a contact binary HH Ursae Majoris

New complete BV light curves of a poorly investigated contact binary HH Ursae Majoris (HH UMa) are presented. The light curves are analyzed by using the 2003 version of the Wilson–Devinney (W–D) code. Combining with the radial velocity published by the previous investigators, we obtain the photometric solution of the system. The solution indicates that HH UMa is a W-type W UMa system with a mass ratio of q=m2/m1=3.344 and a contact degree of 31.9%. The system has a very low inclination of i=53.035° and a temperature difference of 247K between two components. The asymmetry of the light curves can be explained by adding a hot spot located near the neck region of the more massive component. A period investigation based on all available data shows that the period increases at a rate of dP/dt=2.84×10-7daysyr−1, which can be explained by mass transfer from the less massive component to the more massive one. We also give the absolute parameters of the system.

A CCD photometric study of the late type contact binary EK Comae Berenices

We present CCD photometric observations of the W UMa type contact binary EK Comae Berenices using the 2 m telescope of IUCAA Girawali Observatory, India. The star was classified as a W UMa type binary of subtype-W by Samec et al. (1996). The new V band photometric observations of the star reveal that shape of the light curve has changed significantly from the one observed by Samec et al. (1996). A detailed analysis of the light curve obtained from the high-precision CCD photometric observations of the star indicates that EK Comae Berenices is not a W-type but an A-type totally eclipsing W UMa contact binary. The photometric mass ratio is determined to be 0.349 ± 0.005. A temperature difference of Δ T = 141 ± 10 K between the components and an orbital inclination of i[°] = 89.800 ± 0.075 were obtained for the binary system. Absolute values of masses, radii and luminosities are estimated by means of the standard mass-luminosity relation for zero age main-sequence stars. The star shows O’Connell effect, asymmetries in the light curve shape around the primary and secondary maximum. The observed O’Connell effect is explained by the presence of a hot spot on the primary component.

The CCD photometric study of the newly identified RS CVn binary star DV Piscium

This paper presents new CCD BVRI light curves of the newly discovered RS CVn eclipsing binary star DV Psc. From the asymmetric light curves outside the eclipse, we find there are two depressions in the phase ranges 0.3–0.45 and 0.6–0.9, respectively. By analyzing the light curves using the Wilson–Devinney program, the four photometric solutions of the system are obtained and the starspot parameters are also derived. It turns out that the case of two spots being on the primary is most successful in reproducing the light curve distortion of DV Psc. Moreover, analysis the longitudes of spots suggests that there are two active longitude belts (one is about 90°, the other is about 270°). At the same time, on 22 November 2008, the first flare-like event was detected on DV Psc at phase 0.35 whose duration was about 13.5 min. These findings reveal that DV Psc has a high degree of magnetic activity.

UBVRI CCD photometric study of southern open star clusters observed at Pico dos Dias Observatory (LNA/Brazil)

AbstractOpen clusters have long been recognized as important objects to investigate aspects of Galactic structure such as the location of spiral arms, Galactic dynamics or even the chemical-abundance gradients in the Galactic disk. Great effort has been dedicated to studies of these objects throughout the past few years to determine parameters like age, distance, reddening, metallicity as well as kinematic information in a systematic and consistent manner. In this work, we present results on several open clusters selected from the DAML02 catalog that have been observed and investigated for the first time. CCD UBVRI (Johnsons–Cousins system) observations were carried out in 2009 using the 60 cm telescope of the Pico dos Dias Observatory (LNA/Brazil). The color–color and color–magnitude diagrams were analyzed for each cluster with the help of a program written by our group, which allows handling photometric and astrometric data simultaneously. We determined the fundamental parameters (reddening, distance and age) using the main-sequence fitting method, taking into account kinematic information of individual stars in the clusters. The mean proper motion and radial velocity were estimated using a set of stars selected photometrically.

The CCD photometric study of the newly identified RS CVn binary star V1034 Hercules

This paper presents a new CCD Bessell VR c I c light curves and photometric analysis of the newly discovered RS CVn type eclipsing binary star V1034 Her. The light curves were obtained at the Çanakkale Onsekiz Mart University Observatory in 2006. Variations of the orbital period of the system were firstly studied. The ( O − C) diagram with a low range of observing time of about 20 years shows an upward parabola, which indicates a secular increase in the orbital period of the system. The light curves are generally those of detached eclipsing binaries; however, there are large asymmetries between maxima. The VR c I c light curves were analysed with two different fitting procedures: Wilson–Devinney method supplemented with a Monte Carlo type algorithm and Information Limit Optimization Technique (ILOT). Our general results find V1034 Her. as a well detached system, in which the components are filling ∼65% of their Roche lobes. Light curve asymmetries of the system are explained in terms of large dark starspots on the primary component. The primary star shows a long-lived spot distribution with active longitudes in the same hemisphere.

CCD Photometric Study of the W UMa-Type Binary II Canis Majoris in the Field of Berkeley 33

Abstract The CCD photometric data of an EW-type binary, IICMa, which is a contact star in the field of the middle-aged open cluster Berkeley 33, are presented. A complete $R$ light curve was obtained. In the present work, using the five CCD epochs of light minimum [three of them were calculated from Mazur et al. (1993 MNRAS, 265, 405)’s data and two from our new data], the orbital period $P$ was revised to 0.22919704 days. The complete $R$ light curve was analyzed by using the 2003 version of W-D (Wilson-Devinney) program. It is found that this is a contact system with a mass ratio of $q=0.9$ and a contact factor of $f=4.1$%. The high mass ratio ($q=0.9$) and the low contact factor ($f=4.1$%) indicate that the system just evolved into the marginal contact stage.

CCD photometric and mass function study of nine young Large Magellanic Cloud star clusters

Abstract We present a CCD photometric and mass function study of nine young Large Magellanic Cloud star clusters, namely NGC 1767, 1994, 2002, 2003, 2006, SL 538, NGC 2011, 2098 and 2136. BV RI data, reaching down to V∼ 21 mag, were collected from the 3.5-m NTT/EFOSC2 in subarcsec seeing conditions. For NGC 1767, 1994, 2002, 2003, 2011 and 2136, broad-band photometric CCD data are presented for the first time. Seven of the nine clusters have ages between 16 and 25 Myr, and the other two have ages of 32 ± 4 Myr (NGC 2098) and 90 ± 10 Myr (NGC 2136). For the seven youngest clusters, the age estimates based on a recent model and the integrated spectra are found to be systematically lower (∼10 Myr) than the present estimates. In the mass range ∼2–12 M⊙, the mass function slopes for eight out of nine clusters were found to be similar, with the value of γ ranging from −1.90 ± 0.16 to −2.28 ± 0.21. For NGC 1767 the slope is flatter, with γ=−1.23 ± 0.27. Mass segregation effects are observed for NGC 2002, 2006, 2136 and 2098. This is consistent with the findings of Kontizas and colleagues for NGC 2098. The presence of mass segregation in these clusters could be an imprint of the star formation process, as their ages are significantly smaller than their dynamical evolution time. The mean mass function slope of γ=−2.22 ± 0.16 derived for a sample of 25 young (≤100 Myr) dynamically unevolved Large Magellanic Cloud stellar systems provides support for the universality of the initial mass function in the intermediate-mass range ∼2–12 M⊙.

Photometric study of distant open clusters in the second quadrant: NGC 7245, King 9, King 13 and IC 166

We present a UBV CCD photometric study of four open clusters, NGC 7245, King 9, IC 166 and King 13, located between $l = 90^o - 135^o$. All are embedded in a rich galactic field. NGC 7245 and King 9 are close together in the sky and have similar reddenings. The distances and ages are: NGC 7245, 3.8$\pm$0.35 kpc and 400 Myr; King 9 (the most distant cluster in this quadrant) 7.9$\pm$1.1 kpc and 3.0 Gyr. King 13 is 3.1$\pm$0.3 kpc distant and 300 Myr old. King 9 and IC 166 (4.8$\pm$0.5 kpc distant & 1 Gyr old) may be metal poor clusters (Z=0.008), as estimated from isochrone fitting. The average value of the distance of young clusters from the galactic plane in the above longitude range and beyond 2 kpc ($-47\pm$16 pc, for 64 clusters), indicates that the young disk bends towards the southern latitudes.

NEAR-INFRARED PHOTOMETRIC STUDY OF THE GALACTIC OPEN CLUSTERS NGC 1641 AND NGC 2394 BASED ON 2MASS DATA

We present <TEX>$JHK_S$</TEX> near-infrared CCD photometric study for the Galactic open clusters NGC 1641 and NGC 2394. These clusters have never been studied before, and we provide, for the first time the cluster parameters; reddening, distance, metallicity and age. NGC 1641 is an old open cluster with age <TEX>$1.6{\pm}0.2$</TEX> Gyr, metallicity <TEX>$[Fe/H]=0.0{\pm}0.2$</TEX> dex, distance modulus<TEX>$(m-M)_0=10.4{\pm}0.3\;mag(d=1.2{\pm}02\;kpc)$</TEX>, and reddening <TEX>$E(B-V)=0.10{\pm}0.05$</TEX> mag. The parameters for the other old open cluster NGC 2394 are estimated to be <TEX>$age=1.1{\pm}0.2$</TEX> Gyr, <TEX>$[Fe/H]=0.0{\pm}0.2$</TEX> dex, <TEX>$(m-M)_0=9.1{\pm}0.4\;mag(d=660{\pm}120\;pc)$</TEX>, and <TEX>$E(B-V)=0.05{\pm}0.10$</TEX> mag. The metallicities and distance values for these two old open clusters are consistent with the relation between the metallicities and the Galactocentric distances of other old open clusters. We find the metallicity gradient of 53 old open clusters including NGC 1641 and NGC 2394 to be <TEX>${\Delta}[Fe/H]/{\Delta}R_{gc}=-0.067{\pm}0.009\;dex\;kpc^{-1}$</TEX>.

Mass Segregation and Tidal Tails of the Globular Cluster NGC 7492

We present a wide-field CCD photometric study of the Galactic globular cluster NGC 7492. The derived VR color-magnitude diagram (CMD) extends down to about 3.5 mag below the cluster main-sequence turnoff. The field covers 42' × 42', about 3 times larger than the known tidal radius of this cluster. The sample of cluster member candidates obtained by the CMD-mask process has been used to construct luminosity (LFs) and mass functions (MFs) and a surface density map. NGC 7492 has a very flat MF with very little variation in the slope with distance from the cluster center. However, there is a clear evidence for an increase of the MF slope from inner to outer regions, indicating mass segregation of the cluster. The surface density map of NGC 7492 shows extensions toward the Galactic anticenter (northeast) and northwest from the cluster center. A comparison of the LF for stars in the tails with that for stars within the tidal radius suggests that the extensions shown in the surface density map could be a real feature. The overall shape of NGC 7492 is significantly flattened. If the flattened shape of the NGC 7492 is caused by its rotation, the Galactic tidal field must have been an important influence, since the initial rotation would have been almost completely removed by dynamical relaxation.

A CCD Photometric Study of the W UMa–Type Binary System EZ Hydrae

ABSTRACTNew complete CCD light curves in B and V bands for EZ Hya are presented in this paper. The first photometric spectroscopic solution for this system was obtained by using the latest version of the Wilson‐Devinney program. The orbital inclination of 83 .°3(±0 .°6) confirms that this system is a total eclipsing binary system. Our solution indicates that EZ Hya is W‐type overcontact binary with a small mass ratio of q = 0.257(±0.001) and an overcontact degree of f = 34.2%. Combining our light curves with the radial velocity curves from King & Hilditch, we were able to give the absolute parameters of this system: a = 2.98(±0.61) R⊙, R1 = 1.54(±0.32) R⊙, R2 = 0.85(±0.18) R⊙, M1 = 1.37(±0.12) M⊙, and M2 = 0.35(±0.03) M⊙. A period analysis using all photoelectric and CCD times of minimum light suggests an oscillation period of 30.9(±0.61) yr and an amplitude of 0.0185(±0.0012) days. The sinusoidal change can be explained either by the presence of an unseen third body or as the result of magnetic activity cycles of both components.

A comprehensive CCD photometric study of the open cluster NGC 2421

We present the UBVRI CCD photometry in the region of the open cluster NGC 2421. The radius of the cluster is determined as ∼3.0 arcmin using a stellar density profile. Our study indicates that the metallicity of the cluster is Z ∼ 0.004. The reddening E(B - V) = 0.42 ± 0.05 mag is determined using a two colour (U - B) versus (B - V) diagram. By combining the 2MASS JHK data with the optical data, we determined that E(J - K) = 0.20 ± 0.20 mag and E(V - K) = 1.15 ± 0.20 mag for this cluster. Colour-excess diagrams show a normal interstellar extinction law in the direction of the cluster. We determined that the distance of the cluster is 2.2 ± 0.2 kpc by comparing the zero-age main sequence with the intrinsic colour-magnitude diagram of the cluster. The age of the cluster has been estimated as 80 ± 20 Myr using the stellar isochrones of metallicity Z = 0.004. The mass function slope x = 1.2 ± 0.3 has been derived by applying the corrections of field star contamination and data incompleteness. Our analyses indicate that the cluster NGC 2421 is dynamically relaxed.

UBV RICCD photometric study of the open clusters Basel 4 and NGC 7067

In this paper we present UBVRI CCD photometry in the region of two young open star clusters Basel 4 and NGC 7067 for the first time. Our sample consists of ~ 4000 stars down to V ~ 21 mag. Stellar surface density profile indicates that radius of Basel 4 and NGC 7067 are about 1.8 and 3.0 arcmin respectively.The (U-B) versus (B-V) diagrams indicate that metallicity of NGC 7067 is solar while that of Basel 4 is Z ~ 0.008. We estimate the mean value of E(B-V) = 0.45$\pm$0.05 and 0.75$\pm$0.05 mag for Basel 4 and NGC 7067 respectively. The analysis of 2MASS JHK data in combination with the optical data in both the clusters yields E(J-K) = 0.30$\pm$0.20 mag and E(V-K) = 1.60$\pm$0.20 mag for Basel 4 while E(J-K) = 0.40$\pm$0.20 mag and E(V-K) = 2.10$\pm$0.20 mag for NGC 7067. Furthermore, colour excess diagrams show a normal interstellar extinction law towards both the clusters. Using the intrinsic colour-magnitude diagrams of the cluster members, we estimated the distances of the clusters as 3.0$\pm$0.2 and 3.6$\pm$0.2 Kpc for Basel 4 and NGC 7067 respectively. By fitting the proper metallicity isochrones to the bright cluster members we estimated the age of the clusters as 200$\pm$50 and 100$\pm$25 Myr for Basel 4 and NGC 7067 respectively. The mass function slope which is derived by applying the corrections of field star contamination and data incompleteness are $1.55\pm0.25$ and $1.68\pm0.47$ for Basel 4 and NGC 7067 respectively. The values of mass function slopes are thus not too different from the Salpeter's (1955) value. Mass segregation is observed in both the clusters which may be due to the dynamical evolutions or imprint of star formation processes or both.

A CCD photometric study of the W UMa contact binary RZ Comae

In this paper a B-band light curve of the W UMa contact binary RZ Com is presented. From the observations, five times of light minimum were determined. The light curve was analyzed by means of the latest version of the Wilson–Devinney code. The results suggest that RZ Com is a W-subtype contact with a mass ratio of q= m 2/ m 1=2.226. In the new photometric solution, the photospheric temperature of the secondary T 2=4842±8 K. It is slightly lower than the photospheric temperature of the primary T 1.