- ID:
- ivo://CDS.VizieR/J/ApJ/669/424
- Title:
- H2O maser emissions of IRAS 19134+2131
- Short Name:
- J/ApJ/669/424
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the Very Long Baseline Array at six epochs, we have observed H_2_O maser emission in the preplanetary nebula IRAS 19134+2131 (I19134), in which the H_2_O maser spectrum has two groups of emission features separated in radial velocity by ~100km/s. We also obtained optical images of I19134 with the Hubble Space Telescope to locate the bipolar reflection nebula in this source for the first time.
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Search Results
- ID:
- ivo://CDS.VizieR/J/other/AstBu/72.257
- Title:
- Homogeneous Catalog of Open Cluster Param.
- Short Name:
- J/other/AstBu/72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the current version of the "Homogeneous Catalog of Open Clusters Parameters", supported by our group during last decades. The catalog is created on the base of redetermination of the main parameters of clusters (colour excesses, distances from the Sun and ages) using published photometric measurements, in particular, according to the 2MASS catalog of point sources. At present, the catalog contains parameters of 1035 clusters. The catalog includes the radial velocities data for 496 open clusters. All clusters of the catalog have estimates of the components of proper motion.
- ID:
- ivo://CDS.VizieR/I/339
- Title:
- Hot Stuff for One Year (HSOY)
- Short Name:
- I/339
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recently, the first installment of data from ESA's Gaia astrometric satellite mission (Gaia DR1) was released, containing positions of more than 1 billion stars with unprecedented precision, as well as proper motions and parallaxes, however only for a subset of 2 million objects. The second release will include those quantities for most objects. In order to provide a dataset that bridges the time gap between the Gaia DR1 and Gaia DR2 releases and partly remedies the lack of proper motions in the former, HSOY ("Hot Stuff for One Year") was created as a hybrid catalog between Gaia and ground-based astrometry, featuring proper motions (but no parallaxes) for a large fraction of the DR1 objects. While not attempting to compete with future Gaia releases in terms of data quality or number of objects, the aim of HSOY is to provide improved proper motions partly based on Gaia data, allowing studies to be carried out just now or as pilot studies for later projects requiring higher-precision data. The HSOY catalog was compiled using the positions taken from Gaia DR1 combined with the input data from the PPMXL catalog, employing the same weighted least-squares technique that was used to assemble the PPMXL catalog itself. This effect resulted in a four-parameter astrometric catalog containing 583 million stars, with Gaia DR1 quality positions and proper motions with precisions from far less than 1 mas/yr to 5 mas/yr, depending on object brightness and location on the sky.
- ID:
- ivo://CDS.VizieR/J/A+A/317/689
- Title:
- Hot subdwarfs proper motions
- Short Name:
- J/A+A/317/689
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on first results from an ongoing program to measure and analyze proper motions for hot subdwarf and white dwarf stars, with the aim of determining to which stellar population sdB stars (in the V magnitude range 10.5 to 14.5) belong. Ours is the largest sample of hot subdwarf proper motions measured to date. Our kinematic analysis suggests that the parent population of these hydrogen-rich sdB stars is as old or older than the old disk. We measure the absolute magnitude of the sdB in the field as M_V_=4.5, providing independent confirmation of absolute V magnitude estimates for these stars from clusters and spectroscopic analyses. Provided it can be shown that the sdO stars evolve from the sdB, then the sdO absolute V magnitude distribution is about 1 magnitude brighter than for the sdB, and 1 magnitude wider.
- ID:
- ivo://CDS.VizieR/J/ApJ/835/152
- Title:
- HST FGS-1r parallaxes for 8 metal-poor stars
- Short Name:
- J/ApJ/835/152
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hubble Space Telescope (HST) fine guidance sensor observations were used to obtain parallaxes of eight metal-poor ([Fe/H]< -1.4) stars. The parallaxes of these stars determined by the new Hipparcos reduction average 17% accuracy, in contrast to our new HST parallaxes, which average 1% accuracy and have errors on the individual parallaxes ranging from 85 to 144{mu}as. These parallax data were combined with HST Advanced Camera for Surveys photometry in the F606W and F814W filters to obtain the absolute magnitudes of the stars with an accuracy of 0.02-0.03 mag. Six of these stars are on the main sequence (MS) (with -2.7<[Fe/H]< -1.8) and are suitable for testing metal-poor stellar evolution models and determining the distances to metal-poor globular clusters (GCs). Using the abundances obtained by O'Malley+ (2017ApJ...838...90O), we find that standard stellar models using the VandenBerg & Clem (2003AJ....126..778V) color transformation do a reasonable job of matching five of the MS stars, with HD 54639 ([Fe/H]=-2.5) being anomalous in its location in the color-magnitude diagram. Stellar models and isochrones were generated using a Monte Carlo analysis to take into account uncertainties in the models. Isochrones that fit the parallax stars were used to determine the distances and ages of nine GCs (with -2.4{<=}[Fe/H]{<=}-1.9). Averaging together the age of all nine clusters led to an absolute age of the oldest, most metal-poor GCs of 12.7+/-1.0Gyr, where the quoted uncertainty takes into account the known uncertainties in the stellar models and isochrones, along with the uncertainty in the distance and reddening of the clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/840/30
- Title:
- HST/Gemini proper motions for Pyxis
- Short Name:
- J/ApJ/840/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a proper motion measurement for the halo globular cluster Pyxis, using Hubble Space Telescope/ACS data as the first epoch and GeMS/GSAOI Adaptive Optics data as the second, separated by a baseline of ~5 years. This is both the first measurement of the proper motion of Pyxis and the first calibration and use of Multi-Conjugate Adaptive Optics data to measure an absolute proper motion for a faint, distant halo object. Consequently, we present our analysis of the Adaptive Optics data in detail. We obtain a proper motion of {mu}_{alpha}_cos({delta})=1.09+/-0.31mas/yr and {mu}_{delta}_=0.68+/-0.29mas/yr. From the proper motion and line-of-sight velocity, we find that the orbit of Pyxis is rather eccentric, with its apocenter at more than 100kpc and its pericenter at about 30kpc. We also investigate two literature-proposed associations for Pyxis with the recently discovered ATLAS stream and the Magellanic system. Combining our measurements with dynamical modeling and cosmological numerical simulations, we find it unlikely Pyxis is associated with either system. We examine other Milky Way satellites for possible association using the orbit, eccentricity, metallicity, and age as constraints and find no likely matches in satellites down to the mass of Leo II. We propose that Pyxis probably originated in an unknown galaxy, which today is fully disrupted. Assuming that Pyxis is bound and not on a first approach, we derive a 68% lower limit on the mass of the Milky Way of 0.95x10^12^M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/ApJ/853/86
- Title:
- HST large programme on {omega} Centauri. II.
- Short Name:
- J/ApJ/853/86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this second installment of the series, we look at the internal kinematics of the multiple stellar populations of the globular cluster {omega} Centauri in one of the parallel Hubble Space Telescope (HST) fields, located at about 3.5 half-light radii from the center of the cluster. Thanks to the over 15yr long baseline and the exquisite astrometric precision of the HST cameras, well-measured stars in our proper-motion catalog have errors as low as ~10{mu}as/yr, and the catalog itself extends to near the hydrogen-burning limit of the cluster. We show that second-generation (2G) stars are significantly more radially anisotropic than first-generation (1G) stars. The latter are instead consistent with an isotropic velocity distribution. In addition, 1G stars have excess systemic rotation in the plane of the sky with respect to 2G stars. We show that the six populations below the main-sequence (MS) knee identified in our first paper are associated with the five main population groups recently isolated on the upper MS in the core of cluster. Furthermore, we find both 1G and 2G stars in the field to be far from being in energy equipartition, with {eta}_1G_=-0.007+/-0.026 for the former and {eta}_2G_=0.074+/-0.029 for the latter, where {eta} is defined so that the velocity dispersion {sigma}_{mu}_ scales with stellar mass as {sigma}_{mu}_{propto}m^-{eta}^. The kinematical differences reported here can help constrain the formation mechanisms for the multiple stellar populations in {omega} Centauri and other globular clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/861/99
- Title:
- HSTPROMO cat. VI. Improved analysis of NGC362
- Short Name:
- J/ApJ/861/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an improved data-reduction technique to obtain high-precision proper motions (PMs) of globular clusters (GCs) using Hubble Space Telescope data. The new reduction is superior to the one presented in the first paper of this series for the faintest sources in very crowded fields. We choose the GC NGC 362 as a benchmark to test our new procedures. We measure PMs of 117450 sources in the field, showing that we are able to obtain a PM precision better than 10{mu}as/yr for bright stars. We make use of this new PM catalog of NGC 362 to study the cluster's internal kinematics. We investigate the velocity dispersion profiles of the multiple stellar populations hosted by NGC 362 and find new pieces of information on the kinematics of first- and second- generation stars. We analyze the level of energy equipartition of the cluster and find direct evidence for its post-core-collapsed state from kinematic arguments alone. We refine the dynamical mass of the blue stragglers (BSs) and study possible kinematic differences between BSs formed by collisions and mass transfer. We also measure no significant cluster rotation in the plane of the sky. Finally, we measure the absolute PM of NGC 362 and of the background stars belonging to the Small Magellanic Cloud, finding a good agreement with previous estimates in the literature. We make the PM catalog publicly available.
- ID:
- ivo://CDS.VizieR/J/ApJ/797/115
- Title:
- HSTPROMO I. Observations and NGC7078 results
- Short Name:
- J/ApJ/797/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first study of high-precision internal proper motions (PMs) in a large sample of globular clusters, based on Hubble Space Telescope (HST) data obtained over the past decade with the ACS/WFC, ACS/HRC, and WFC3/UVIS instruments. We determine PMs for over 1.3 million stars in the central regions of 22 clusters, with a median number of ~60000 stars per cluster. These PMs have the potential to significantly advance our understanding of the internal kinematics of globular clusters by extending past line-of-sight (LOS) velocity measurements to two- or three-dimensional velocities, lower stellar masses, and larger sample sizes. We describe the reduction pipeline that we developed to derive homogeneous PMs from the very heterogeneous archival data. We demonstrate the quality of the measurements through extensive Monte Carlo simulations. We also discuss the PM errors introduced by various systematic effects and the techniques that we have developed to correct or remove them to the extent possible. We provide in electronic form the catalog for NGC 7078 (M 15), which consists of 77837 stars in the central 2.4'. We validate the catalog by comparison with existing PM measurements and LOS velocities and use it to study the dependence of the velocity dispersion on radius, stellar magnitude (or mass) along the main sequence, and direction in the plane of the sky (radial or tangential).
- ID:
- ivo://CDS.VizieR/J/AJ/127/2771
- Title:
- HST proper-motions of M4 main-sequence stars
- Short Name:
- J/AJ/127/2771
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new results from a photometric study of the main-sequence stars in M4 (NGC 6121=C1620-264), the closest globular cluster to the Sun. Multifield, multiepoch observations at approximately 1, 2, and 6 core radii were obtained with WFPC2 on the Hubble Space Telescope through either the F606W filter or the F555W (V) and F814W (I) filters. The multi-epoch observations allowed us to clean the data on the basis of proper motion and thus separate cluster from field stars or extragalactic objects.
