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1651. Vr light curves of NGC 5466 RR Lyrae
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.
1652. VR light curves of 15 RR Lyrae in NGC 4147
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.
1653. VR photometry of type II Cepheids
ID:
ivo://CDS.VizieR/J/AJ/128/1748
Title:
VR photometry of type II Cepheids
Short Name:
J/AJ/128/1748
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 1256 new photometric observations of 36 Cepheids with periods longer than 8 days. The majority are likely type II Cepheids, but we have included about a dozen classical Cepheids for comparison purposes, a few stars of uncertain type, and one putative RV Tauri star. We discuss the appearance of the light curves, the Fourier parameters, and the light-curve stability in terms of differentiation between type I and type II Cepheids. Although we encounter the same difficulties as previous investigators in using these parameters for this purpose, we are able to identify some stars of particular interest, including several likely type I Cepheids at large distances from the Galactic plane. Six stars with especially large period changes are identified and discussed.
1654. VR photometry of type II Cepheids. III
ID:
ivo://CDS.VizieR/J/AJ/130/832
Title:
VR photometry of type II Cepheids. III
Short Name:
J/AJ/130/832
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 741 new photometric observations for 22 Cepheids with periods between 3 and 8 days. Many of the stars are probable type II Cepheids, but we have included some type I Cepheids for comparison.
1655. V340 Ser and V448 Lac light curves
ID:
ivo://CDS.VizieR/J/PAZh/37/691
Title:
V340 Ser and V448 Lac light curves
Short Name:
J/PAZh/37/691
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyze long-term UBV observations and ASAS-3 photometry for five candidates for protoplanetary nebulae - F and G supergiants with infrared excesses at high Galactic latitudes - V340 Ser, IRAS 05113+1347, V552 Pup, V448 Lac, and RV Col. These stars exhibit quasi-periodic multifrequency light variations caused by pulsations with characteristic time scales from 83 to 139 days, depending on the stellar temperature. Cooler stars undergo variations with larger amplitudes and periods. The variations at close frequencies with a period ratio of 1.03-1.09 are responsible for the amplitude modulation revealed for most program stars.
1656. V356 Sgr optical polarization
ID:
ivo://CDS.VizieR/J/MNRAS/464/1936
Title:
V356 Sgr optical polarization
Short Name:
J/MNRAS/464/1936
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyse 45 spectropolarimetric observations of the eclipsing, interacting binary star V356 Sgr, obtained over a period of ~21yr, to characterize the geometry of the system's circumstellar material. After removing interstellar polarization from these data, we find that the system exhibits a large intrinsic polarization signature arising from electron scattering. In addition, the lack of repeatable eclipses in the polarization phase curves indicates the presence of a substantial pool of scatterers not occulted by either star. We suggest that these scatterers form either a circumbinary disc coplanar with the gainer's accretion disc or an elongated structure perpendicular to the orbital plane of V356 Sgr, possibly formed by bipolar outflows. We also observe small-scale, cycle-to-cycle variations in the magnitude of intrinsic polarization at individual phases, which we interpret as evidence of variability in the amount of scattering material present within and around the system. This may indicate a mass-transfer or mass-loss rate that varies on the time-scale of the system's orbital period. Finally, we compare the basic polarimetric properties of V356 Sgr with those of the well-studied {beta} Lyr system; the significant differences observed between the two systems suggest diversity in the basic circumstellar geometry of Roche lobe overflow systems.
1657. V1241 Tau and GQ Dra light curves
ID:
ivo://CDS.VizieR/J/AcA/70/219
Title:
V1241 Tau and GQ Dra light curves
Short Name:
J/AcA/70/219
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new photometric and spectroscopic observations and analyses for the eclipsing binary systems V1241 Tau and GQ Dra. Our photometric light and radial velocity curves analyses combining with the TESS light curves show that both are conventional semi--detached binary systems. Their absolute parameters are also derived. We present the O-C analyses of the systems and we propose the most possible orbital period modulating mechanisms. Furthermore, Fourier analyses are applied to the photometric residual data of the systems to check for the pulsational behavior of the components. We conclude that the primary component of the system GQ Dra is a delta Sct type pulsator with a dominant pulsation frequency of 18.58d^-1^ based on our B filter residual light curve although it can not be justified by 30-minute cadence TESS data. No satisfactory evidence of pulsational behaviour for V1241 Tau was verified. Finally, the evolutionary tracks of the components of both systems are calculated, while their locations within evolutionary diagrams are compared with other Algol-type systems.
1658. V1184 Tauri UBVRI light curves
ID:
ivo://CDS.VizieR/J/A+A/582/A113
Title:
V1184 Tauri UBVRI light curves
Short Name:
J/A+A/582/A113
Date:
21 Oct 2021
Publisher:
CDS
Description:
V1184 Tau (CB 34V) lies in the field of the Bok globule CB 34 and was discovered as a large amplitude variable in 1993. According to the first hypothesis of the variability of the star, it is a FU Orionis candidate erupted between 1951 and 1993. During subsequent observations, the star manifests large amplitude variability interpreted as obscuration from circumstellar clouds of dust. We included V1184 Tau (CB 34V) in our target list of highly variable pre-main-sequence stars to determine the reasons for the variations in the brightness of this object. Data from BVRI photometric observations of V1184 Tau were performed in two observatories with two medium-sized and two small telescopes. Our results indicate that during periods of maximum light the star shows characteristics typical of T Tauri stars. During the observed deep minimum in brightness, however, V1184 Tau is rather similar to UX Orionis objects. The deep drop in brightness magnitude diagrams is also confirmation of obscuration from circumstellar clouds of dust as a reason for the large amplitude variability in the brightness.
1659. V1794 UBVR time series
ID:
ivo://CDS.VizieR/J/A+A/351/212
Title:
V1794 UBVR time series
Short Name:
J/A+A/351/212
Date:
21 Oct 2021
Publisher:
CDS
Description:
Standard Johnson UBVRI photometry of V1794 Cyg (HD 199178) between 1975 and 1995 is analysed. Instead of the traditional constant period ephemeris, we determine the seasonal periodicities (P_phot_) and the primary and secondary minima epochs (t_min,1_, t_min,2_) of the normalized UBVRI magnitudes using the three stage period analysis (TSPA) and complementary methods.
1660. VVV globulars. I. 2MASS-GC 02, Terzan 10
ID:
ivo://CDS.VizieR/J/AJ/149/99
Title:
VVV globulars. I. 2MASS-GC 02, Terzan 10
Short Name:
J/AJ/149/99
Date:
21 Oct 2021
Publisher:
CDS
Description:
The VISTA Variables in the Via Lactea (VVV) ESO Public Survey is opening a new window to study inner Galactic globular clusters (GCs) using their variable stars. These GCs have been neglected in the past due to the difficulties caused by the presence of elevated extinction and high field stellar densities in their lines of sight. However, the discovery and study of any present variables in these clusters, especially RR Lyrae stars, can help to greatly improve the accuracy of their physical parameters. It can also help to shed some light on the questions raised by the intriguing Oosterhoff dichotomy in the Galactic GC system. In a series of papers we plan to explore variable stars in the GCs falling inside the field of the VVV survey. In this first paper, we search for and study the variables present in two highly reddened, moderately metal-poor, faint, inner Galactic GCs: 2MASS-GC 02 and Terzan 10. We report the discovery of sizable populations of RR Lyrae stars in both GCs. We use near-infrared period-luminosity relations to determine the color excess of each RR Lyrae star, from which we obtain both accurate distances to the GCs and the ratios of the selective-to-total extinction in their directions. We find the extinction toward both clusters to be elevated, non-standard, and highly differential. We also find both clusters to be closer to the Galactic center than previously thought, with Terzan 10 being on the far side of the Galactic bulge. Finally, we discuss their Oosterhoff properties, and conclude that both clusters stand out from the dichotomy followed by most Galactic GCs.