- ID:
- ivo://CDS.VizieR/J/A+A/573/A103
- Title:
- Light curves for variables in 5 clusters
- Short Name:
- J/A+A/573/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present the analysis of time-series observations from 2013 and 2014 of five metal rich ([Fe/H]>-1) globular clusters: NGC6388, NGC6441, NGC6528, NGC6638, and NGC6652. The data have been used to perform a census of the variable stars in the central parts of these clusters. The observations were made with the electron multiplying CCD (EMCCD) camera at the Danish 1.54m Telescope at La Silla, Chile, and they were analysed using difference image analysis (DIA) to obtain high-precision light curves of the variable stars. It was possible to identify and classify all of the previously known or suspected variable stars in the central regions of the five clusters. Furthermore, we were able to identify, and in most cases classify 48, 49, 7, 8, and 2 previously unknown variables in NGC 6388, NGC 6441, NGC 6528, NGC 6638, and NGC 6652, respectively. Especially interesting is the case of NGC 6441, for which the variable star population of about 150 stars has been thoroughly examined by previous studies, including a Hubble Space Telescope study. In this paper we are able to present 49 new variable stars for this cluster, of which one (possibly two) are RR Lyrae stars, two are W Virginis stars, and the rest are long period semi-regular or irregular variables on the red giant branch. We have also detected the first double mode RR Lyrae in the cluster.
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- ID:
- ivo://CDS.VizieR/J/AJ/143/13
- Title:
- Light curves of AL Gem and BM Mon
- Short Name:
- J/AJ/143/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the CCD photometry of two Algol-type binaries, AL Gem and BM Mon, observed from 2008 November to 2011 January. With the updated Wilson-Devinney program, photometric solutions were deduced from their EA-type light curves. The mass ratios and fill-out factors of the primaries are found to be q_ph_=0.090(+/-0.005) and f_1_=47.3%(+/-0.3%) for AL Gem, and q_ph_=0.275(+/-0.007) and f_1_=55.4%(+/-0.5%) for BM Mon, respectively. By analyzing the O-C curves, we discovered that the periods of AL Gem and BM Mon change in a quasi-sinusoidal mode, which may possibly result from the light-time effect via the presence of a third body. Periods, amplitudes, and eccentricities of light-time orbits are 77.83(+/-1.17)yr, 0.0204(+/-0.0007)d, and 0.28(+/-0.02) for AL Gem and 97.78(+/-2.67)yr, 0.0175(+/-0.0006)d, and 0.29(+/-0.02) for BM Mon, respectively. Assumed to be in a coplanar orbit with the binary, the masses of the third bodies would be 0.29M_{sun}_ for AL Gem and 0.26M_{sun}_ for BM Mon. This kind of additional companion can extract angular momentum from the close binary orbit, and such processes may play an important role in multiple star evolution.
- ID:
- ivo://CDS.VizieR/J/AJ/147/66
- Title:
- Light curves of Algol-type binaries. VII. V404 And
- Short Name:
- J/AJ/147/66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new CCD light curves of the short-period Algol-type eclipsing binary V404 And obtained in 2009-2011. The time-resolving multiple BVRI color light curves of the year 2011 with full phase coverage were analyzed simultaneously using the latest Wilson-Devinney program. We concluded that the configuration of two starspots on the primary is the most reliable explanation for the light curve distortions observed in 2011. Based on the new photometric solution, we further applied the spot model to explain the other light curves, including the previously published R-band light curves. We revealed that the starspots changed on a long timescale in terms of the spot parameters and the differences between Max.I and Max.II. Moreover, the O-C diagram spanning about 15yr shows an upward parabola, which indicates a secular increase in the orbital period of V404 And. The orbital period increases at a rate of dP/dt=5.3(0.3)x10^-7^days/yr, which might be interpreted by the angular momentum exchange via magnetic activity.
- ID:
- ivo://CDS.VizieR/J/A+A/507/495
- Title:
- Light curves of Datura and 2003 CL5 asteroids
- Short Name:
- J/A+A/507/495
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Research of asteroid families has been recently refreshed by the discovery of very young ones. These families are of great interest because they represent the product of their parent body fragmentation before orbital and physical evolutionary processes can change them. A cluster of seven objects around the largest body (1270) Datura is of particular interest because it has enough known members and resides in the inner part of the main asteroid belt, facilitating observations. We carried out photometric observations of the two largest members of the Datura family - asteroids (1270) Datura and (90265) 2003 CL5 - with the goal of inferring their physical parameters. We also used numerous astrometric observations of Datura-family members in the past few years to revisit the age of this cluster.
- ID:
- ivo://CDS.VizieR/J/A+A/546/A72
- Title:
- Light curves of Flora region asteroids
- Short Name:
- J/A+A/546/A72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent studies have uncovered evidence that the statistical properties of asteroids' physical parameters are a fundamental source of information on the physics of their collisions and evolution. The analysis of the spin rates and spin vector distributions helps us to understand the role of various known and new effects. The alignment of spin vectors and the correlation of spin rates are for the first time observed for ten members of the Koronis family. These unexpected non-random orientations of the spin axes and correlations of the spin rates, now known as Slivan states are interpreted in terms of a YORP effect and spin-orbit resonances. To study non-gravitational-effects, there appears to be a need for new observational campaigns devoted to determining the physical parameters of the asteroid families. We analysed the photometric observations of the asteroids, which are the most efficient method of studying asteroid physical parameters.
- ID:
- ivo://CDS.VizieR/J/AJ/148/126
- Title:
- Light curves of four overcontact binaries
- Short Name:
- J/AJ/148/126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze new, high quality multicolor light curves of four overcontact binaries: AK Her, HI Dra, V1128 Tau, and V2612 Oph, and determine their orbital and physical parameters using the modeling program of G. Djurasevic and recently published results of radial velocity studies. The achieved precision in absolute masses is between 10% and 20%, and the precision in absolute radii is between 5% and 10%. All four systems are W UMa-type binaries with bright or dark spots indicative of mass and energy transfer or surface activity. We estimate the distances and the ages of the systems using the luminosities computed through our analysis, and perform an O-C study for V1128 Tau, which reveals a complex period variation that can be interpreted in terms of mass loss/exchange and either the presence of the third body, or the magnetic activity on one of the components. We conclude that further observations of these systems are needed to deepen our understanding of their nature and variability.
- ID:
- ivo://CDS.VizieR/J/A+A/550/L11
- Title:
- Lightcurves of Near-Earth Asteroid 162173 (1999 JU3)
- Short Name:
- J/A+A/550/L11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Near-Earth asteroid (hereafter NEA) 162173 (1999 JU3) is a potential target of two asteroid sample return missions not only because of its accessibility but also because of the first C-type asteroid for exploration missions. The lightcurve related physical properties of this object were investigated during the 2011-2012 apparition. We aim to confirm the physical parameters useful for JAXAs Hayabusa 2 mission such as rotational period, absolute magnitude and phase function. Our data complement previous studies which did not cover low phase angles. With optical imagers and 1-2m class telescopes, we acquired the photometric data at different phase angles. We independently derived the rotational lightcurve and the phase curve of the asteroid.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A123
- Title:
- Lightcurves of Near-Earth Asteroid 3200 Phaethon
- Short Name:
- J/A+A/619/A123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The near-Earth asteroid 3200 Phaethon (1983 TB) is an attractive object not only from a scientific viewpoint but also because of JAXA's DESTINY+ target. The rotational lightcurve and spin properties were investigated based on the data obtained in the ground-based observation campaign of Phaethon. We aim to refine the lightcurves and shape model of Phaethon using all available lightcurve datasets obtained via optical observation, as well as our time-series observation data from the 2017 apparition. Using eight 1-2-m telescopes and an optical imager, we acquired the optical lightcurves and derived the spin parameters of Phaethon. We applied the lightcurve inversion method and SAGE (Shaping Asteroids with Genetic Evolution) algorithm to deduce the convex and non-convex shape model and pole orientations.
- ID:
- ivo://CDS.VizieR/J/A+A/511/A49
- Title:
- Lightcurves of 12 NEAs
- Short Name:
- J/A+A/511/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Very small asteroids (VSAs) are thought to be the building blocks of larger asteroids and, as such, are interesting to study. Many of these monolithic or deeply fractured objects display rapid rotations with periods as short as several minutes. Observations of such asteroids can reveal their spin limits, which can be related to the tensile strength of their interiors. The evolution of the spins of these objects is primarily shaped by the YORP effect, the theory of which needs comparison with observations. With the 10m SALT telescope, we observed VSAs belonging to near-Earth asteroids. The obtained lightcurves were used to derive synodical periods of rotation, amplitudes, and elongations of these bodies. Results for 14 rapidly rotating asteroids were reported in the first paper in this series. Here we show lightcurves of 2 fast rotators, 9 objects with periods >=1h, and a possible non-principal axis rotator. We also list negative detections that most probably indicate asteroids with long periods and/or low amplitudes. Combining our results with the data from the literature, we obtain a set of 79 near-Earth VSAs with a median period of 0.25h (15min). By adjusting the spin limits predicted by theory to those observations, we find tentative evidence that the tensile strengths of VSAs, after scaling them to the same size, are of the same order as the minimum tensile strengths of stony meteoroids that undergo fragmentation under the atmospheric load.
- ID:
- ivo://CDS.VizieR/J/A+A/509/A94
- Title:
- Lightcurves of 14 NEAs
- Short Name:
- J/A+A/509/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report first results from our extensive survey of the very small (H>21.5mag) near-Earth asteroids. Our aim was to obtain photometric lightcurves for these faint, fast moving objects and to measure their rotation periods and amplitudes of light variations. These parameters can be used to make statistical analysis of the still little known population of the smallest asteroids, test present theories of the YORP effect as well as to study their spin limits, which are connected with their internal structure. Due to the faintness of the targets and the expected short periods of rotation, observations were performed with the large, 10-m SALT telescope in SAAO (South Africa). For most asteroids, V filter images with exposure times of 5-60 seconds were obtained with the instrument's SALTICAM's CCD camera. Even though the non-sidereal tracking was not available, the SALTICAM's relatively large field-of-view of 8'x8' helped to perform the relative photometry of the fast-moving targets. The presented asteroids have synodic periods ranging from 77s to 44min, effective diameters from 21 to 94m, and significantly elongated shapes.
