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- ID:
- ivo://CDS.VizieR/J/A+A/557/A77
- Title:
- VR light curves of AA Tau in 2007-2013
- Short Name:
- J/A+A/557/A77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- AA Tau has been monitored for more than 20 years since 1987, exhibiting a nearly constant brightness level of V=12.5mag. We report here that in 2011 it suddenly faded away, becoming 2 magnitudes fainter in the V-band, and has remained in this deep state since then. We investigate the origin of the sudden dimming of the AA Tau system. We report new optical and near-IR photometry and spectroscopy obtained during the fading event.
- ID:
- ivo://CDS.VizieR/J/AJ/143/122
- Title:
- VR light curves of CK Boo
- Short Name:
- J/AJ/143/122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present precision CCD photometry, a period study, and a two-color simultaneous Wilson code solution of the short-period contact binary CK Bootis. The asymmetric light curves were modeled by a dark spot on the primary component. The result identifies that CK Boo is an A-type W UMa binary with a high fillout of f=71.7(+/-4.4)%. From the O-C curve, it is found that the orbital period changes in a complicated mode, i.e., a long-term increase with two sinusoidal variations. One cyclic oscillation with a period of 10.67(+/-0.20)yr may result from magnetic activity cycles, which are identified by the variability of Max. I-Max. II. Another sinusoidal variation (i.e., A=0.0131days(+/-0.0009days) and P3=24.16(+/-0.64)yr) may be attributed to the light-time effect due to a third body. This kind of additional companion can extract angular momentum from the central binary system. The orbital period secularly increases at a rate of dP/dt=+9.79(+/-0.80)*10^-8days/yr, which may be interpreted by conservative mass transfer from the secondary to the primary. This kind of deep, low-mass ratio overcontact binaries may evolve into a rapid-rotating single star, only if the contact configuration do not break down at J_spin_>(1/3)J_orb_.
- ID:
- ivo://CDS.VizieR/J/other/RAA/11.181
- Title:
- VR light curves of EI CVn
- Short Name:
- J/other/RAA/11.1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present charge-coupled device (CCD) photometry for the short-period K-type binary EI CVn, observed on 2009 February 28 at the Xinglong Station of National Astronomical Observatories, Chinese Academy of Sciences. By using the Wilson-Devinney program, the photometric solution was first deduced from our VR observations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/372/69
- Title:
- VR light curves of M2 variables
- Short Name:
- J/MNRAS/372/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of CCD V and R photometry of the RR Lyrae stars in M2. The periodicities of most variables are revised and new ephemerides are calculated. Light-curve decomposition of the RR Lyrae stars was carried out and the corresponding mean physical parameters [Fe/H]=-1.47, Teff=6276K, logL=1.63L_{sun}_ and M_V_=0.71 from nine RRab and [Fe/H]=-1.61, M=0.54M_{sun}_, Teff=7215K, logL=1.74L_{sun}_ and M_V_=0.71 from two RRc stars were calculated. A comparison of the radii obtained from the above luminosity and temperature with predicted radii from non-linear convective models is discussed. The estimated mean distance to the cluster is 10.49+/-0.15kpc. These results place M2 correctly in the general globular cluster sequences for Oosterhoff type, mass, luminosity and temperature, all as a function of the metallicity. Mean relationships for M, logL/L_{sun}_, Teff and MV as a function of [Fe/H] for a family of globular clusters are offered. These trends are consistent with evolutionary and structural notions on the horizontal branch. Eight new variables are reported.
- ID:
- ivo://CDS.VizieR/J/MNRAS/384/1444
- Title:
- Vr light curves of NGC 5466 RR Lyrae
- Short Name:
- J/MNRAS/384/1444
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of CCD V and r photometry of the globular cluster NGC 5466. The difference image analysis technique adopted in this work has resulted in accurate time series photometry even in crowded regions of the cluster enabling us to discover five probably semi-regular variables. We present new photometry of three previously known eclipsing binaries and six SX Phe stars. The light curves of the RR Lyrae stars have been decomposed in their Fourier harmonics and their fundamental physical parameters have been estimated using semi-empirical calibrations. The zero points of the metallicity, luminosity and temperature scales are discussed and our Fourier results are transformed accordingly. The average iron abundance and distance to the Sun derived from individual RR Lyrae stars, indicate values of [Fe/H]=-1.91+/-0.19 and D=16.0+/-0.6kpc, or a true distance modulus of 16.02+/-0.09mag, for the parent cluster. These values are respectively in the Zinn & West metallicity scale and in agreement with recent luminosity determinations for the RR Lyrae stars in the LMC. The M_V_-[Fe/H] relation has been recalibrated as M_V_=+(0.18+/-0.03)[Fe/H]+(0.85+/-0.05) using the mean values derived by the Fourier technique on RR Lyrae s tars in a family of clusters. This equation predicts M_V_=0.58mag for [Fe/H]=-1.5, in agreement with the average absolute magnitude of RR Lyrae stars calculated from several independent methods. The M_V-[Fe/H] relationship and the value of [Fe/H] have implications on the age of the globular clusters when determined from the magnitude difference between the horizontal branch and the turn off point (HB-TO method). The above results however would not imply a change in the age of NGC 5466, of 12.5+/-0.9Gyr, estimated from recent isochrone fitting.
- ID:
- ivo://CDS.VizieR/J/other/RMxAA/40.209
- Title:
- VR light curves of 15 RR Lyrae in NGC 4147
- Short Name:
- J/other/RMxAA/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of CCD V and R photometry of the RR Lyrae stars known in NGC 4147. The periodicities of most variables are revised and new ephemerides are calculated. The Blazhko effect has been detected in V2 and V6. Three previously reported variables; V5, V9, and V15 are found to be non-variable. A new variable V18 was discovered with a period of 0.49205-days and an amplitude of 0.15mag. Using the approach of Fourier decomposition of the light curves, the physical parameters of the RRab and RRc variables were estimated. The cluster is of the Oosterhoff type I. With the newly values [Fe/H]=-1.22+/-0.31 and 16.8+/-1.3kpc, the cluster fits very well into the Oosterhoff type-metallicity and metallicity-temperature sequence found in globular clusters. A comparison with ZAHB models indicates that the RRab stars have not yet evolved off the horizontal branch, a result consistent with the mean period of the RRab variables and with the metallicity of the cluster derived in this work.
- ID:
- ivo://CDS.VizieR/J/AJ/152/129
- Title:
- VR photometry for 914 stars in NGC 188
- Short Name:
- J/AJ/152/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the newly commissioned 50cm Binocular Network telescope at Qinghai Station of Purple Mountain Observatory (Chinese Academy of Sciences) to observe the old open cluster NGC188 in V and R as part of a search for variable objects. Our time-series data span a total of 36 days. Radial velocity and proper-motion selection resulted in a sample of 532 genuine cluster members. Isochrone fitting was applied to the cleaned cluster sequence, yielding a distance modulus of (m-M)_V_^0^=11.35+/-0.10mag and a total foreground reddening of E(V-R)=0.062+/-0.002mag. Light-curve solutions were obtained for eight W Ursae Majoris eclipsing binary systems (W UMas), and their orbital parameters were estimated. Using the latter parameters, we estimate a distance to the W UMas that is independent of the host cluster's physical properties. Based on combined fits to six of the W UMas (EP Cep, EQ Cep, ES Cep, V369 Cep, and-for the first time-V370 Cep and V782 Cep), we obtain an average distance modulus of (m-M)_V_^0^=11.31+/-0.08mag, which is comparable to that resulting from our isochrone fits. These six W UMas exhibit an obvious period-luminosity relation. We derive more accurate physical parameters for the W UMa systems and discuss their initial masses and ages. The former show that these W UMa systems have likely undergone angular momentum evolution within a convective envelope (W-type evolution). The ages of the W UMa systems agree well with the cluster's age.
- ID:
- ivo://CDS.VizieR/J/A+AS/119/329
- Title:
- VR photometry in the Shapley Supercluster
- Short Name:
- J/A+AS/119/329
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present V and R CCD photometric sequences of stars and galaxies for calibrating ESO/SERC (R) survey plates in the region of the Shapley supercluster of galaxies.
- ID:
- ivo://CDS.VizieR/J/AJ/122/714
- Title:
- VR photometry of Century Survey galaxies
- Short Name:
- J/AJ/122/714
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use 64{deg}^2^ of deep V and R CCD images to measure the local V- and R-band luminosity functions of galaxies. The V_0_<16.7 and R_0_<16.2 redshift samples contain 1255 and 1251 galaxies and are 98.1% and 98.2% complete, respectively.
