- ID:
- ivo://CDS.VizieR/J/AJ/159/199
- Title:
- OCCAM. IV. Open cluster abundances using APOGEE DR16
- Short Name:
- J/AJ/159/199
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Open Cluster Chemical Abundances and Mapping (OCCAM) survey aims to constrain key Galactic dynamical and chemical evolution parameters by the construction of a large, comprehensive, uniform, infrared-based spectroscopic data set of hundreds of open clusters. This fourth contribution from the OCCAM survey presents analysis using Sloan Digital Sky Survey/APOGEE DR16 of a sample of 128 open clusters, 71 of which we designate to be "high quality" based on the appearance of their color-magnitude diagram. We find the APOGEE DR16 derived [Fe/H] abundances to be in good agreement with previous high-resolution spectroscopic open cluster abundance studies. Using the high-quality sample, we measure Galactic abundance gradients in 16 elements, and find evolution of some of the [X/Fe] gradients as a function of age. We find an overall Galactic [Fe/H] versus Rgc gradient of -0.068{+-}0.001dex/kpc over the range of 6<Rgc<13.9kpc; however, we note that this result is sensitive to the distance catalog used, varying as much as 15%. We formally derive the location of a break in the [Fe/H] abundance gradient as a free parameter in the gradient fit for the first time. We also measure significant Galactic gradients in O, Mg, S, Ca, Mn, Cr, Cu, Na, Al, and K, some of which are measured for the first time. Our large sample allows us to examine four well-populated age bins in order to explore the time evolution of gradients for a large number of elements and comment on possible implications for Galactic chemical evolution and radial migration.
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- ID:
- ivo://CDS.VizieR/J/A+A/658/A14
- Title:
- OCCASO IV. open cluster stars radial velocities
- Short Name:
- J/A+A/658/A14
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Open clusters (OCs) are widely used as test particles to investigate a variety of astrophysical phenomena, from stellar evolution to Galactic evolution. Gaia and the complementary massive spectroscopic surveys are providing an unprecedented wealth of information about these systems. The Open Cluster Chemical Abundances from Spanish Observatories (OCCASO) survey aims to complement all this work by determining OCs' accurate radial velocities and chemical abundances from high-resolution, R>=60000, spectra. Methods. Radial velocities were obtained by cross-correlating the observed spectra with a library of synthetic spectra that covers early M to A spectral types. We provide radial velocities for 336 stars including several Gaia benchmark stars and objects belonging to 51 open clusters. The internal uncertainties of the derived radial velocities go from 10m/s to 21m/s as a function of the instrumental configuration used. The derived radial velocities, together with the Gaia proper motions, were used to investigate the cluster membership of the observed stars. After this careful membership analysis, we obtained average velocities for 47 open clusters. To our knowledge, this is the first radial velocity determination for five of these clusters. Finally, the radial velocities, proper motions, distances and ages were used to investigate the kinematics of the observed clusters and in the integration of their orbits.
- ID:
- ivo://CDS.VizieR/J/MNRAS/458/3150
- Title:
- OCCASO survey. HRV for 12 open clusters
- Short Name:
- J/MNRAS/458/3150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Open clusters (OCs) are crucial for studying the formation and evolution of the Galactic disc. However, the lack of a large number of OCs analyzed homogeneously hampers the investigations about chemical patterns and the existence of Galactocentric radial and vertical gradients, or an age-metallicity relation. To overcome this, we have designed the Open Cluster Chemical Abundances from Spanish Observatories survey (OCCASO). We aim to provide homogeneous radial velocities, physical parameters and individual chemical abundances of six or more Red Clump stars for a sample of 25 old and intermediate-age OCs visible from the Northern hemisphere. To do so, we use high resolution spectroscopic facilities (R~62,000) available at Spanish observatories. We present the motivation, design and current status of the survey, together with the first data release of radial velocities for 77 stars in 12 OCs, which represents about 50% of the survey. We include clusters never studied with high-resolution spectroscopy before (NGC 1907, NGC 6991, NGC 7762), and clusters in common with other large spectroscopic surveys like the Gaia-ESO Survey (NGC 6705) and APOGEE (NGC 2682 and NGC 6819). We perform internal comparisons between instruments to evaluate and correct internal systematics of the results, and compare our radial velocities with previous determinations in the literature, when available. Finally, radial velocities for each cluster are used to perform a preliminar kinematic study in relation with the Galactic disc.
- ID:
- ivo://CDS.VizieR/J/ApJ/868/30
- Title:
- OGLE LMC-T2CEP-211 eclipsing binary LCs and RVs
- Short Name:
- J/ApJ/868/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of a peculiar W Virginis (pWVir) type II Cepheid, OGLE-LMC-T2CEP-211 (P_puls_=9.393d), in a double-lined binary system (P_orb_=242d), which shed light on virtually unknown evolutionary status and structure of pWVir stars. The dynamical mass of the Cepheid (first ever for a type II Cepheid) is 0.64+/-0.02M_{sun}_, and the radius R=25.1+/-0.3R_{sun}_. The companion is a massive (5.67M_{sun}_) main-sequence star obscured by a disk. Such a configuration suggests a mass transfer in the system history. We found that originally the system (P_orb_^init^=12d) was composed of 3.5 and 2.8M_{sun}_ stars, with the current Cepheid being more massive. The system age is now ~200Myr, and the Cepheid is almost completely stripped of hydrogen, with helium mass of ~92% of the total mass. It finished transferring the mass 2.5Myr ago and is evolving toward lower temperatures passing through the instability strip. Comparison with observations indicates a reasonable 2.7x10^-8^M_{sun}_/yr mass loss from the Cepheid. The companion is most probably a Be main-sequence star with T=22000K and R=2.5R_{sun}_. Our results yield a good agreement with a pulsation theory model for a hydrogen-deficient pulsator, confirming the described evolutionary scenario. We detected a two-ring disk (R_disk_~116R_{sun}_) and a shell (R_shell_~9R_{sun}_) around the companion, which is probably a combination of the matter from the past mass transfer, the mass being lost by the Cepheid owing to wind and pulsations, and a decretion disk around a rapidly rotating secondary. Our study, together with observational properties of pWVir stars, suggests that the majority of them are products of a similar binary evolution interaction.
1095. OH/H2O masers database
- ID:
- ivo://CDS.VizieR/J/A+AS/137/43
- Title:
- OH/H2O masers database
- Short Name:
- J/A+AS/137/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 3 contains VLA spectra and positions for OH and H2O maser spots in 74 star-forming regions mapped by Forster and Caswell (1989A&A...213..339F). Galactic coordinates are given, followed by offset positions of the 22GHz continuum peak (HII) if detected, and the flux, velocity and positions of OH and H_2_O maser spots mapped in that field.
- ID:
- ivo://CDS.VizieR/J/A+A/297/494
- Title:
- OH maser from semiregular variables
- Short Name:
- J/A+A/297/494
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have made a high sensivity (~0.15Jy) search in the OH main-lines for maser emission from a sample of 181 semiregular variables.
- ID:
- ivo://CDS.VizieR/J/AJ/143/52
- Title:
- Old star clusters in NGC 4449 from HST imaging
- Short Name:
- J/AJ/143/52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use Hubble Space Telescope imaging to show that the nearby dwarf starburst galaxy NGC 4449 (=UGC 7592) has an unusual abundance of luminous red star clusters. Joint constraints from integrated photometry, low-resolution spectroscopy, dynamical mass-to-light ratios, and resolved color-magnitude diagrams provide evidence that some of these clusters are old globular clusters (GCs). Spectroscopic data for two massive clusters suggest intermediate metallicities ([Fe/H]~-1) and subsolar Mg enhancement ([Mg/Fe]~-0.1 to -0.2). One of these clusters may be the nucleus of a tidally disrupting dwarf galaxy; the other is very massive (~3*10^6^M_{sun}_). We have also identified a population of remote halo GCs. NGC 4449 is consistent with an emerging picture of the ubiquity of stellar halos among dwarf galaxies, and study of its GCs may help distinguish between accretion and in situ scenarios for such halos.
- ID:
- ivo://CDS.VizieR/J/A+A/583/A76
- Title:
- Omega Cen candidates RAVE-selected
- Short Name:
- J/A+A/583/A76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using six-dimensional phase-space information from the Fourth Data release of the RAdial Velocity Experiment (RAVE) over the range of Galactic longitude 240{deg}<l<360{deg} and VLSR<-239km/s, we computed orbits for 329 RAVE stars that were originally selected as chemically and kinematically related to Omega Centauri. The orbits were integrated in a Milky-Way-like axisymmetric Galactic potential, ignoring the effects of the dynamical evolution of Omega Centauri due to the tidal effects of the Galaxy disk on the cluster along time. We also ignored secular changes in the Milky Way potential over time. In a Monte Carlo scheme, and under the assumption that the stars may have been ejected with velocities greater than the escape velocity (V_rel_>V_esc,0_) from the cluster, we identified 15 stars as having close encounters with Omega Centauri: (i) 8 stars with relative velocities V_rel_<200km/s may have been ejected ~200Myr ago from Centauri; (ii) another group of 7 stars were identified with high relative velocity V_rel_>200km/s during close encounters, and it seems unlikely that they were ejected from Omega Centauri. We also confirm the link between J131340.4-484714 as a potential member of Omega Centauri, and probably ejected ~2.0Myr ago, with a relative velocity V_rel_~80km/s.
- ID:
- ivo://CDS.VizieR/J/AJ/114/1087
- Title:
- Omega Cen radial velocities
- Short Name:
- J/AJ/114/1087
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents a catalog of the mean radial velocities of 471 giant stars in the galactic globular cluster Omega Cen, the large majority of which are confirmed as cluster members. The typical uncertainty in the mean velocities is less than 1kms; a variability indicator and notes on chemical peculiarities are provided. In extension of earlier dynamical analyses of Omega Cen, based on part of the data presented here (Meylan & Mayor 1986A&A...166..122M; Meylan 1987A&A...184..144M; Meylan et al. 1995A&A...303..761M), a companion paper (Merritt et al. 1997AJ....114.1074M) rediscusses the subject, based on the full data set and a new theoretical approach, using nonparametric techniques.
- ID:
- ivo://CDS.VizieR/J/ApJ/710/L30
- Title:
- On the multiplicity of the O star Herschel 36
- Short Name:
- J/ApJ/710/L30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of high-resolution optical spectroscopic observations of the zero-age main-sequence O star Herschel 36 spanning six years. This star is definitely a multiple system, with at least three components detected in its spectrum. Based on our radial-velocity (RV) study, we propose a picture of a close massive binary and a more distant companion, most probably in wide orbit about each other. The orbital solution for the binary, whose components we identify as O9V and B0.5V, is characterized by a period of 1.5415+/-0.0006 days. With a spectral type O7.5V, the third body is the most luminous component of the system and also presents RV variations with a period close to 498 days. Some possible hypotheses to explain the variability are briefly addressed and further observations are suggested.
