- 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.
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Search Results
- 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/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.
- ID:
- ivo://CDS.VizieR/J/AJ/158/54
- Title:
- New Taurus members from stellar to planetary masses
- Short Name:
- J/AJ/158/54
- Date:
- 06 Dec 2021 11:31:43
- Publisher:
- CDS
- Description:
- We present a large sample of new members of the Taurus star-forming region that extend from stellar to planetary masses. To identify candidate members at substellar masses, we have used color-magnitude diagrams and proper motions measured with several wide-field optical and infrared (IR) surveys. At stellar masses, we have considered the candidate members that were found in a recent analysis of high-precision astrometry from the Gaia mission. Using new and archival spectra, we have measured spectral types and assessed membership for these 161 candidates, 79 of which are classified as new members. Our updated census of Taurus now contains 519 known members. According to Gaia data, this census should be nearly complete for spectral types earlier than M6-M7 at A_J_<1. For a large field encompassing ~72% of the known members, the census should be complete for K<15.7 at A_J_<1.5, which corresponds to ~5-13 M_Jup_ for ages of 1-10 Myr based on theoretical evolutionary models. Our survey has doubled the number of known members at >=M9 and has uncovered the faintest known member in M_K_, which should have a mass of ~3-10 M_Jup_ for ages of 1-10 Myr. We have used mid-IR photometry from the Spitzer Space Telescope and the Wide-field Infrared Survey Explorer to determine whether the new members exhibit excess emission that would indicate the presence of circumstellar disks. The updated disk fraction for Taurus is ~0.7 at =<M3.5 and ~0.4 at >M3.5.
- ID:
- ivo://CDS.VizieR/J/PASP/130/L4101
- Title:
- NGC 2112, 2477, 7789 and Col 261 members
- Short Name:
- J/PASP/130/L4101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Membership determination of open clusters in high-noise environments is still an open question. This paper aims to evaluate the effectiveness of the Gaussian mixture model (GMM) in segregating likely cluster members of open clusters in high-noise environments. We use the GMM method to segregate likely cluster members of four low Galactic latitude open clusters: NGC 2112, NGC 2477, NGC 7789, and Collinder 261, based on the high-precision astrometric data of the Gaia Data Release 2 (Gaia-DR2). The GMM method is used to calculate the membership probabilities of the stars in the field of each cluster; five astrometric parameters (positions, parallaxes, and proper motions) are taken into account. We quantitatively evaluate the goodness of the cluster-field segregation for each cluster, and find that the GMM method is effective for segregating likely cluster members of these clusters, even if these clusters suffer from heavy field star contamination. We estimate the distances and absolute proper motions of these clusters using reliable cluster members; our results suggest the existence of a significant zero-point offset in Gaia-DR2 parallaxes. NGC 2112, NGC 2477, NGC 7789, and Collinder 261 are found to have a mean distance of <D>=1104+/-4, 1437+/-2, 2067+/-4 and 2802+/-21pc, respectively. Mean proper motions of (<{mu}_{alpha}_cos{delta}>, <{mu}_{delta}_>)=(-2.714+/-0.012, 4.272+/-0.012), (-2.449+/-0.006, 0.876+/-0.006), (-0.919+/-0.004, -1.938+/-0.004), and (-6.348+/-0.006, -2.714+/-0.006)mas/yr are determined for NGC 2112, NGC 2477, NGC 7789, and Collinder 261, respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/634/A51
- Title:
- NGC 330 seen by MUSE
- Short Name:
- J/A+A/634/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A majority of massive stars are part of binary systems, a large fraction of which will inevitably interact during their lives. Binary-interaction products (BiPs), i.e. stars affected by such interaction, are expected to be commonly present in stellar populations. BiPs are thus a crucial ingredient in the understanding of stellar evolution. We aim to identify and characterize a statistically significant sample of BiPs by studying clusters of 10-40Myr, an age at which binary population models predict the abundance of BiPs to be highest. One example of such a cluster is NGC 330 in the Small Magellanic Cloud. Using MUSE WFM-AO observations of NGC 330, we resolve the dense cluster core for the first time and are able to extract spectra of its entire massive star population. We develop an automated spectral classification scheme based on the equivalent widths of spectral lines in the red part of the spectrum. We characterize the massive star content of the core of NGC 330 which contains more than 200 B stars, 2 O stars, 6 A-type supergiants and 11 red supergiants. We find a lower limit on the Be star fraction of 32+/-3% in the whole sample. It increases to at least 46+/-10% when only considering stars brighter than V=17mag. We estimate an age of the cluster core between 35 and 40Myr and a total cluster mass of 88^+17^_-18_*10^3M_{sun}_. We find that the population in the cluster core is different than the population in the outskirts: while the stellar content in the core appears to be older than the stars in the outskirts, the Be star fraction and the observed binary fraction are significantly higher. Furthermore, we detect several BiP candidates that will be subject of future studies.
- ID:
- ivo://CDS.VizieR/J/A+A/652/A70
- Title:
- NGC 330 seen by MUSE. II.
- Short Name:
- J/A+A/652/A70
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Observations of massive stars in open clusters younger than 8 Myr have shown that a majority of them are in binary systems, most of which will interact during their life. While these can be used as a proxy of the initial multiplicity properties, studying populations of massive stars older than ~20Myr allows us to probe the outcome of such interactions after a significant number of systems have experienced mass and angular momentum transfer and possibly even merged. Using multi-epoch integral-field spectroscopy, we aim to investigate the multiplicity properties of the massive-star population in the dense core of the ~40Myr-old cluster NGC 330 in the Small Magellanic Cloud in order to search for possible imprints of stellar evolution on the multiplicity properties. We obtained six epochs of VLT/MUSE observations operated in wide-field mode with the extended wavelength setup and supported by adaptive optics.We extract spectra and measure radial velocities for stars brighter than m_F814W_=19. We identify single-lined spectroscopic binaries through significant RV variability with a peak-to-peak amplitude larger than 20km/s. We also identify double-lined spectroscopic binaries, and quantify the observational biases for binary detection. In particular, we take into account that binary systems with similar line strength are difficult to detect in our data set. The observed spectroscopic binary fraction among the stars brighter than m_F814W_=19 (~5.5M_{sun}_ on the main sequence) is f^obs^_SB_=13.2+/-2:0%. Considering period and mass ratio ranges from log(P)=0.15-3.5 (about 1.4 to 3160d), and q=0.1-1.0, and a representative set of orbital parameter distributions, we find a bias-corrected close binary fraction of f_cl_=34^+8^_-7_%. This fraction seems to decline for the fainter stars, which indicates either that the close binary fraction drops in the B-type domain, or that the period distribution becomes more heavily weighted towards longer orbital periods.We further find that both fractions vary strongly in different regions of the color-magnitude diagram that corresponds to different evolutionary stages. This probably reveals the imprint of the binary history of different groups of stars. In particular, we find that the observed spectroscopic binary fraction of Be stars (f^obs^_SB_=2+/-2%) is significantly lower than the one of B-type stars (f^obs^_SB_=9+/-2%). In this work we provide the first homogeneous RV study of a large sample of B-type stars at a low metallicity ([Fe/H]<~-1.0). The overall bias-corrected close binary fraction (log(P)<3.5d) of the B-star population in NGC 330 is lower than the one reported for younger Galactic and LMC clusters in previous works. More data are, however, needed to establish whether the observed differences result from an age or a metallicity effect.
40. NGC 6067 stars
- ID:
- ivo://CDS.VizieR/J/MNRAS/469/1330
- Title:
- NGC 6067 stars
- Short Name:
- J/MNRAS/469/1330
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 6067 is a young open cluster hosting the largest population of evolved stars among known Milky Way clusters in the 50-150Ma age range. It thus represents the best laboratory in our Galaxy to constrain the evolutionary tracks of 5-7M_{sun}_ stars. We have used high-resolution spectra of a large sample of bright cluster members (45), combined with archival photometry, to obtain accurate parameters for the cluster as well as stellar atmospheric parameters. We derive a distance of 1.78+/-0.12 kpc, an age of 90+/-20Ma and a tidal radius of 14.8^+6.8^_-3.2_ arcmin. We estimate an initial mass above 5700M_{sun}_, for a present-day evolved population of two Cepheids, two A supergiants and 12 red giants with masses ~=6M_{sun}_. We also determine chemical abundances of Li, O, Na, Mg, Si, Ca, Ti, Ni, Rb, Y and Ba for the red clump stars. We find a supersolar metallicity, [Fe/H]=+0.19+/-0.05, and a homogeneous chemical composition, consistent with the Galactic metallicity gradient. The presence of a Li-rich red giant, star 276 with A(Li)=2.41, is also detected. An overabundance of Ba is found, supporting the enhanced s-process. The ratio of yellow to red giants is much smaller than 1, in agreement with models with moderate overshooting, but the properties of the cluster Cepheids do not seem consistent with current Padova models for supersolar metallicity.
