- ID:
- ivo://CDS.VizieR/J/PASP/131/D4101
- Title:
- Likely Pleiades members with Gaia DR2
- Short Name:
- J/PASP/131/D4101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents an investigation on fundamental astrophysical properties of the Pleiades cluster (M 45) using high-precision astrometric and photometric data from the Gaia Data Release 2 (Gaia-DR2). To obtain reliable cluster members, a machine-learning (ML) method is used to compute membership probabilities for 31462 sample stars within a radius of 6.5{deg} from the cluster center, both the astrometric and photometric data are taken into account. We obtain a total number of 1454 likely cluster members with membership probabilities larger than 0.6, including a well-known white dwarf (LB 1497) with a high membership probability of ~0.96. We find a well-defined relationship between the parallaxes and proper motions of the cluster members, the most likely explanation for the relationship is that the depth effect of the cluster along the line of sight must be taken into consideration. Using Monte Carlo simulations, the most likely distance, proper motion, and radial velocity of the cluster are determined to be D=136.0+/-0.1pc, (<{mu}_{alpha}_cos{delta}>, <{mu}_{delta}_>)=(+20.141+/-0.093, -45.536+/ -0.081)mas/yr, and <V_r_>=+5.8+/-0.1km/s, respectively. It is found that the likely cluster members extend outward to a limiting radius of R_lim_=310'+/-12' (12.3+/-0.5pc) from the cluster center, and the total mass of the cluster within this radius is M_tot_=721+/-93M_{sun}_. We find clear evidence for the presence of spatial mass segregation in this young cluster by analyzing the photometry and spatial positions of the likely cluster members. Interestingly, we also find that four high-mass cluster members with high membership probabilities (>0.99) are being ejected from the inner region of the cluster, they may have formed via close encounters between single and binary stars.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/137/4377
- Title:
- List of SEGUE plate pairs
- Short Name:
- J/AJ/137/4377
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sloan Extension for Galactic Understanding and Exploration (SEGUE) Survey obtained ~240000 moderate-resolution (R~1800) spectra from 3900{AA} to 9000{AA} of fainter Milky Way stars (14.0<g<20.3) of a wide variety of spectral types, both main-sequence and evolved objects, with the goal of studying the kinematics and populations of our Galaxy and its halo. The spectra are clustered in 212 regions spaced over three quarters of the sky. Radial velocity accuracies for stars are {sigma}(RV)~4km/s at g<18, degrading to {sigma}(RV)~15km/s at g~20. For stars with signal-to-noise ratio >10 per resolution element, stellar atmospheric parameters are estimated, including metallicity, surface gravity, and effective temperature. SEGUE obtained 3500deg^2^ of additional ugriz imaging (primarily at low Galactic latitudes) providing precise multicolor photometry ({sigma}(g,r,i) ~2%), ({sigma}(u,z)~3%) and astrometry (~0.1") for spectroscopic target selection. The stellar spectra, imaging data, and derived parameter catalogs for this survey are publicly available as part of Sloan Digital Sky Survey Data Release 7. Individual images of spectra in this data set may be examined by fetching from the DAS, with a link like wget http://das.sdss.org/spectro/1d_26/1880/gif/spPlot-53262-1880-014.gif A FITS data file of the calibrated 1D spectrum is available from wget http://das.sdss.org/spectro/1d_26/1880/1d/spSpec-53262-1880-014.fit
- ID:
- ivo://CDS.VizieR/J/MNRAS/342/1241
- Title:
- Low-mass stars in M45 and M44
- Short Name:
- J/MNRAS/342/1241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present near-infrared J-, H- and K-band photometry and optical spectroscopy of low-mass star and brown dwarf (BD) candidates in the Pleiades and Praesepe open clusters. We flag non-members from their position in K, I-K and J, J-K colour-magnitude diagrams (CMDs), and J-H, H-K two-colour diagrams.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A187
- Title:
- Massive binaries in Westerlund 1. VII.
- Short Name:
- J/A+A/635/A187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Context. The formation, properties, and evolution of massive stars remain subject to considerable theoretical and observational uncertainty. This impacts on fields as diverse as galactic feedback, the production of cosmic rays, and the nature of the progenitors of both electromagnetic and gravitational wave transients. Aims. The young massive clusters many such stars reside within provide a unique laboratory for addressing these issues. In this work we provide a comprehensive stellar census of Westerlund 1 in order to to underpin such efforts. Methods. We employed optical spectroscopy of a large sample of early-type stars to determine cluster membership for photometrically-identified candidates, characterise their spectral type, and identify new candidate spectroscopic binaries. Results. Sixty nine new members of Westerlund 1 are identified via I-band spectroscopy. Together with previous observations, they illustrate a smooth and continuous morphological sequence from late-O giant through to OB supergiant. Subsequently, the progression bifurcates, with one branch yielding mid-B to late-F hypergiants, and cool supergiants, and the other massive blue stragglers prior to a diverse population of H-depleted WRs. We identify a substantial population of O-type stars with very broad Paschen series lines, a morphology that is directly comparable to known binaries in the cluster. In a few cases additional low-resolution R-band spectroscopy is available, revealing double-lined He I profiles and confirming binarity for these objects; suggesting a correspondingly high binary fraction amongst relatively unevolved cluster members.Conclusions. Our current census remains incomplete, but indicates that Westerlund 1 contains at least 166 stars with initial masses estimated to lie between ~25M_{sun}_ and ~50M_{sun}_, with more massive stars already lost to supernova. Our data is consistent with the cluster being co-eval, although binary interaction is clearly required to yield the observed stellar population, which is characterised by a uniquely rich cohort of hypergiants ranging from spectral type O to F, with both mass-stripped primaries and rejuvenated secondaries or merger products present. Future observations of Wd1 and similar stellar aggregates hold out the prospect of characterising both single- and binary- evolutionary channels for massive stars and determining their relative contributions. This in turn will permit the physical properties of such objects at the point of core-collapse to be predicted, which is of direct relevance for understanding the formation of relativistic remnants such as the magnetars associated with Wd1 and other young massive clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/288/413
- Title:
- Massive stars in I Zw 36
- Short Name:
- J/A+A/288/413
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed the blue dwarf galaxy I Zw 36 with the f/96 relay of the HST Faint Object Camera and have for the first time resolved massive stars, using the broad band filters F175W, F342W, F430W and F480LP. We have measured the fluxes of 143 of these objects and studied their characteristics in color-magnitude diagrams. A few stars may be red supergiants but their contribution to the integrated light is less than 5% in the F430W filter. The F175W-F430W color of the integrated stellar population is redder than expected from the current burst of star formation, suggesting therefore the presence of an older and unresolved underlying population. The ultraviolet measurements combined with synthetic photometry calculations allow us to place the massive stars in a bolometric magnitude vs. temperature diagram. In this diagram, the stars are compared to evolutionary tracks for different stellar masses. The current burst probably has an age less than 12Myr. We infer an Initial Mass Function, with a power-law slope in the range -1.7 to -2.6 for masses M>=20M_{sun}_. This is consistent with most of the values reported for sites of star formation in the Galaxy and the Magellanic Clouds and does not support the view of an IMF flattening at low metallicity.
- ID:
- ivo://CDS.VizieR/J/MNRAS/416/3108
- Title:
- Membership of Sco OB2 moving group
- Short Name:
- J/MNRAS/416/3108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new high-mass membership of the nearby Sco OB2 association based on Hipparcos positions, proper motions and parallaxes, and radial velocities taken from the 2nd Catalogue of Radial Velocities with Astrometric Data (CRVAD-2). The Bayesian membership selection method developed makes no distinction between subgroups of Sco OB2 and utilizes linear models in calculation of membership probabilities. We select 436 members, 88 of which are new members not included in previous membership selections. We include the classical non-members alpha-Cru and beta-Cru as new members as well as the pre-main-sequence stars HIP 79080 and 79081. We also show that the association is well mixed over distances of 8{deg} on the sky, and hence no determination can be made as to the formation process of the entire association.
- ID:
- ivo://CDS.VizieR/J/A+A/345/471
- Title:
- Memberships of open clusters
- Short Name:
- J/A+A/345/471
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New memberships, mean parallaxes and proper motions of all 9 open clusters closer than 300pc (except the Hyades) and 9 rich clusters between 300 and 500pc have been computed using Hipparcos (Cat. <I/239>) data. Precisions, ranging from 0.2 to 0.5mas for parallaxes and 0.1 to 0.5mas/yr for proper motions, are of great interest for calibrating photometric parallaxes as well as for kinematical studies. Careful investigations of possible biases have been performed and no evidence of significant systematic errors on the mean cluster parallaxes has been found. The distances and proper motions of 32 more distant clusters, which may be used statistically, are also indicated.
- ID:
- ivo://CDS.VizieR/J/AJ/158/239
- Title:
- Metal-rich host stars abundances & equivalent widths
- Short Name:
- J/AJ/158/239
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The relationship between the compositions of giant planets and their host stars is of fundamental interest in understanding planet formation. The solar system giant planets are enhanced above solar composition in metals, both in their visible atmospheres and bulk compositions. A key question is whether the metal enrichment of giant exoplanets is correlated with that of their host stars. Thorngren et al. (2016, J/ApJ/831/64) showed that in cool (T_eq_<1000 K) giant exoplanets, the total heavy-element mass increases with total M_p_ and the heavy-element enrichment relative to the parent star decreases with total M_p_. In their work, the host star metallicity was derived from literature [Fe/H] measurements. Here we conduct a more detailed and uniform study to determine whether different host star metals (C, O, Mg, Si, Fe, and Ni) correlate with the bulk metallicity of their planets, using correlation tests and Bayesian linear fits. We present new host star abundances of 19 cool giant planet systems, and combine these with existing host star data for a total of 22 cool giant planet systems (24 planets). Surprisingly, we find no clear correlation between stellar metallicity and planetary residual metallicity (the relative amount of metal versus that expected from the planet mass alone), which is in conflict with common predictions from formation models. We also find a potential correlation between residual planet metals and stellar volatile-to-refractory element ratios. These results provide intriguing new relationships between giant planet and host star compositions for future modeling studies of planet formation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/505/979
- Title:
- Model spectra for identifying age spreads
- Short Name:
- J/MNRAS/505/979
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- In this third paper of a series on the precision of obtaining ages of stellar populations using the full spectrum fitting technique, we examine the precision of this technique in deriving possible age spreads within a star cluster. We test how well an internal age spread can be resolved as a function of cluster age, population mass fraction, and signal-to-noise (S/N) ratio. For this test, the two ages (Age (SSP1) and Age (SSP2)) are free parameters along with the mass fraction of SSP1. We perform the analysis on 118,800 mock star clusters covering all ages in the range 6.8<log(age/yr)<10.2, with mass fractions from 10% to 90% for two age gaps (0.2dex and 0.5dex). Random noise is added to the model spectra to achieve S/N ratios between 50 to 100 per wavelength pixel. We find that the mean of the derived Age (SSP1) generally matches the real Age (SSP1) to within 0.1dex up to ages around log(age/yr)=9.5. The precision decreases for log(age/yr)>9.6 for any mass fraction or S/N, due to the similarity of SED shapes for those ages. In terms of the recovery of age spreads, we find that the derived age spreads are often larger than the real ones, especially for log(age/yr)<8.0 and high mass fractions of SSP1. Increasing the age gap in the mock clusters improves the derived parameters, but Age (SSP2) is still overestimated for the younger ages.
- ID:
- ivo://CDS.VizieR/J/MNRAS/476/3160
- Title:
- Monoceros star-forming region radial velocities
- Short Name:
- J/MNRAS/476/3160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The principal aim of this work is to study the velocity field in the Monoceros star-forming region using the radial velocity data available in the literature, as well as astrometric data from the Gaia first release. This region is a large star-forming com- plex formed by two associations named Monoceros OB1 and OB2. We have collected radial velocity data for more than 400 stars in the area of 8x12 square degrees and distance for more than 200 objects. We apply a clustering analysis in the subspace of the phase space formed by angular coordinates and radial velocity or distance data using the Spectrum of Kinematic Grouping methodology. We found four and three spatial groupings in radial velocity and distance variables, respectively, corresponding to the Local arm, the central clusters forming the associations and the Perseus arm, respectively.
