scholarly journals Spectroscopic membership for the populous 300 Myr-old open cluster NGC 3532

2019 ◽  
Vol 622 ◽  
pp. A110 ◽  
Author(s):  
D. J. Fritzewski ◽  
S. A. Barnes ◽  
D. J. James ◽  
A. M. Geller ◽  
S. Meibom ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Galactic Plane ◽  
Open Cluster ◽  
Mass Range ◽  
Open Clusters ◽  
Radial Velocities ◽  
Stellar Rotation ◽  
Low Mass Stars ◽  
Giant Stars ◽  
Cluster Sequence

Context. NGC 3532 is an extremely rich open cluster embedded in the Galactic disc, hitherto lacking a comprehensive, documented membership list. Aims. We provide membership probabilities from new radial velocity observations of solar-type and low-mass stars in NGC 3532, in part as a prelude to a subsequent study of stellar rotation in the cluster. Methods. Using extant optical and infra-red photometry we constructed a preliminary photometric membership catalogue, consisting of 2230 dwarf and turn-off stars. We selected 1060 of these for observation with the AAOmega spectrograph at the 3.9 m-Anglo-Australian Telescope and 391 stars for observations with the Hydra-South spectrograph at the 4 m Victor Blanco Telescope, obtaining spectroscopic observations over a decade for 145 stars. We measured radial velocities for our targets through cross-correlation with model spectra and standard stars, and supplemented them with radial velocities for 433 additional stars from the literature. We also measured log g, Teff, and [Fe/H] from the AAOmega spectra. Results. The radial velocity distribution emerging from the observations is centred at 5.43 ± 0.04 km s−1 and has a width (standard deviation) of 1.46 km s−1. Together with proper motions from Gaia DR2 we find 660 exclusive members, of which five are likely binary members. The members are distributed across the whole cluster sequence, from giant stars to M dwarfs, making NGC 3532 one of the richest Galactic open clusters known to date, on par with the Pleiades. From further spectroscopic analysis of 153 dwarf members we find the metallicity to be marginally sub-solar, with [Fe/H] = −0.07 ± 0.10. We confirm the extremely low reddening of the cluster, EB − V = 0.034 ± 0.012 mag, despite its location near the Galactic plane. Exploiting trigonometric parallax measurements from Gaia DR2 we find a distance of 48435−30 pc [(m − M)0 = 8.42 ± 0.14 mag]. Based on the membership we provide an empirical cluster sequence in multiple photometric passbands. A comparison of the photometry of the measured cluster members with several recent model isochrones enables us to confirm the 300 Myr cluster age. However, all of the models evince departures from the cluster sequence in particular regions, especially in the lower mass range.

scholarly journals Open cluster kinematics with Gaia DR2

2018 ◽  
Vol 619 ◽  
pp. A155 ◽  
Author(s):  
C. Soubiran ◽  
T. Cantat-Gaudin ◽  
M. Romero-Gómez ◽  
L. Casamiquela ◽  
C. Jordi ◽  
...  
Keyword(s):  
Phase Space ◽  
Velocity Distribution ◽  
Radial Velocity ◽  
Galactic Plane ◽  
Open Cluster ◽  
Open Clusters ◽  
High Resolution Spectroscopy ◽  
Weighted Mean ◽  
High Quality ◽  
Young Clusters

Context. Open clusters are very good tracers of the evolution of the Galactic disc. Thanks to Gaia, their kinematics can be investigated with an unprecedented precision and accuracy. Aims. The distribution of open clusters in the 6D phase space is revisited with Gaia DR2. Methods. The weighted mean radial velocity of open clusters was determined, using the most probable members available from a previous astrometric investigation that also provided mean parallaxes and proper motions. Those parameters, all derived from Gaia DR2 only, were combined to provide the 6D phase-space information of 861 clusters. The velocity distribution of nearby clusters was investigated, as well as the spatial and velocity distributions of the whole sample as a function of age. A high-quality subsample was used to investigate some possible pairs and groups of clusters sharing the same Galactic position and velocity. Results. For the high-quality sample of 406 clusters, the median uncertainty of the weighted mean radial velocity is 0.5 km s−1. The accuracy, assessed by comparison to ground-based high-resolution spectroscopy, is better than 1 km s−1. Open clusters nicely follow the velocity distribution of field stars in the close solar neighbourhood as previously revealed by Gaia DR2. As expected, the vertical distribution of young clusters is very flat, but the novelty is the high precision to which this can be seen. The dispersion of vertical velocities of young clusters is at the level of 5 km s−1. Clusters older than 1 Gyr span distances to the Galactic plane of up to 1 kpc with a vertical velocity dispersion of 14 km s−1, typical of the thin disc. Five pairs of clusters and one group with five members might be physically related. Other binary candidates that have been identified previously are found to be chance alignments.

scholarly journals Radial-velocity search and statistical studies for short-period planets in the Pleiades open cluster

2020 ◽  
Vol 72 (6) ◽  
Author(s):  
Takuya Takarada ◽  
Bun’ei Sato ◽  
Masashi Omiya ◽  
Yasunori Hori ◽  
Michiko S Fujii
Keyword(s):  
Radial Velocity ◽  
Open Cluster ◽  
Open Clusters ◽  
Occurrence Rate ◽  
High Dispersion ◽  
Echelle Spectrograph ◽  
Upper Limit ◽  
Stringent Constraint ◽  
Short Period ◽  
Statistical Studies

Abstract We report on a radial-velocity search for short-period planets in the Pleiades open cluster. We observed 30 Pleiades member stars at the Okayama Astrophysical Observatory with the High Dispersion Echelle Spectrograph. To evaluate and mitigate the effects of stellar activity on radial-velocity (RV) measurements, we computed four activity indicators (full width at half maximum, Vspan, Wspan, and SHα). Among our sample, no short-period planet candidates were detected. Stellar intrinsic RV jitter was estimated to be 52 m s−1, 128 m s−1, and 173 m s−1 for stars with $v$ sin i of 10 km s−1, 15 km s−1, and 20 km s−1, respectively. We determined the planet occurrence rate from our survey and set the upper limit to 11.4% for planets with masses 1–13 MJUP and period 1–10 d. To set a more stringent constraint on the planet occurrence rate, we combined the result of our survey with those of other surveys targeting open clusters with ages in the range 30–300 Myr. As a result, the planet occurrence rate in young open clusters was found to be less than 7.4%, 2.9%, and 1.9% for planets with an orbital period of 3 d and masses of 1–5, 5–13, and 13–80 MJUP, respectively.

scholarly journals A Gaia DR2 view of the open cluster population in the Milky Way

2018 ◽  
Vol 618 ◽  
pp. A93 ◽  
Author(s):  
T. Cantat-Gaudin ◽  
C. Jordi ◽  
A. Vallenari ◽  
A. Bragaglia ◽  
L. Balaguer-Núñez ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Milky Way ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Open Cluster ◽  
Open Clusters ◽  
Number Of Clusters ◽  
History Of ◽  
Gaia Dr2

Context. Open clusters are convenient probes of the structure and history of the Galactic disk. They are also fundamental to stellar evolution studies. The second Gaia data release contains precise astrometry at the submilliarcsecond level and homogeneous photometry at the mmag level, that can be used to characterise a large number of clusters over the entire sky. Aims. In this study we aim to establish a list of members and derive mean parameters, in particular distances, for as many clusters as possible, making use of Gaia data alone. Methods. We compiled a list of thousands of known or putative clusters from the literature. We then applied an unsupervised membership assignment code, UPMASK, to the Gaia DR2 data contained within the fields of those clusters. Results. We obtained a list of members and cluster parameters for 1229 clusters. As expected, the youngest clusters are seen to be tightly distributed near the Galactic plane and to trace the spiral arms of the Milky Way, while older objects are more uniformly distributed, deviate further from the plane, and tend to be located at larger Galactocentric distances. Thanks to the quality of Gaia DR2 astrometry, the fully homogeneous parameters derived in this study are the most precise to date. Furthermore, we report on the serendipitous discovery of 60 new open clusters in the fields analysed during this study.

scholarly journals OCCASO – III. Iron peak and α elements of 18 open clusters. Comparison with chemical evolution models and field stars

2019 ◽  
Vol 490 (2) ◽  
pp. 1821-1842 ◽  
Author(s):  
L Casamiquela ◽  
S Blanco-Cuaresma ◽  
R Carrera ◽  
L Balaguer-Núñez ◽  
C Jordi ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Open Cluster ◽  
Dynamical Evolution ◽  
Open Clusters ◽  
Chemical Abundances ◽  
Homogeneous Sample ◽  
Giant Stars ◽  
Stellar Nucleosynthesis ◽  
Solar Abundances ◽  
Red Giant

ABSTRACT The study of open-cluster chemical abundances provides insights on stellar nucleosynthesis processes and on Galactic chemo-dynamical evolution. In this paper we present an extended abundance analysis of 10 species (Fe, Ni, Cr, V, Sc, Si, Ca, Ti, Mg, O) for red giant stars in 18 OCCASO clusters. This represents a homogeneous sample regarding the instrument features, method, line list and solar abundances from confirmed member stars. We perform an extensive comparison with previous results in the literature, and in particular with the Gaia FGK Benchmark stars Arcturus and $\mu$-Leo. We investigate the dependence of [X/Fe] with metallicity, Galactocentric radius (6.5 kpc < RGC < 11 kpc), age (0.3 Gyr < Age < 10 Gyr), and height above the plane (|z| < 1000 pc). We discuss the observational results in the chemo-dynamical framework, and the radial migration impact when comparing with chemical evolution models. We also use APOGEE DR14 data to investigate the differences between the abundance trends in RGC and |z| obtained for clusters and for field stars.

scholarly journals The nature of the NGC 2546: Not one but two open clusters

2020 ◽  
Vol 633 ◽  
pp. A146 ◽  
Author(s):  
A. D. Alejo ◽  
J. F. González ◽  
M. E. Veramendi
Keyword(s):  
Radial Velocity ◽  
Binary Stars ◽  
Open Cluster ◽  
Open Clusters ◽  
Spectroscopic Binaries ◽  
Physical Parameters ◽  
Distance Modulus ◽  
Cluster Membership ◽  
Spectroscopic Observations ◽  
Astrometric Data

Context. As part of a broader project on the role of binary stars in clusters, we present a spectroscopic study of the open cluster NGC 2546, which is a large cluster lacking previous spectroscopic analysis. Aims. We report the finding of two open clusters in the region of NGC 2546. For the two star groups, we determine radial velocity, parallax, proper motion, reddening, distance modulus, and age, using our spectroscopic observations and available photometric and astrometric data, mainly from the second Gaia data release (Gaia-DR2). We also determine the orbit of four spectroscopic binaries in these open clusters. Methods. From mid-resolution spectroscopic observations for 28 stars in the NGC 2546 region, we determined radial velocities and evaluate velocity variability. To analyze double-lined spectroscopic binaries, we used a spectral separation technique and fit the spectroscopic orbits using a least-squares code. The presence of two stellar groups is suggested by the radial velocity distribution and confirmed by available photometric and astrometric data. We applied a multi-criteria analysis to determine cluster membership, and obtained kinematic and physical parameters of the clusters. Results. NGC 2546 is actually two clusters, NGC 2546A and NGC 2546B, which are not physically related to each other. NGC 2546A has an age of about 180 Myr and a distance of 950 pc. It has a half-number radius of 8 pc and contains about 480 members brighter than G = 18 mag. NGC 2546B is a very young cluster (<10 Myr) located at a distance of 1450 pc. It is a small cluster with 80 members and a half-number radius of 1.6 pc. Stars less massive than 2.5 M⊙ in this cluster would be pre-main-sequence objects. We detected four spectroscopic binaries and determined their orbits. The two binaries of NGC 2546A contain chemically peculiar components: HD 68693 is composed of two mercury-manganese stars and HD 68624 has a Bp silicon secondary. Among the most massive objects of NGC 2546B, there are two binary stars: HD 68572, with P = 124.2 d, and CD -37 4344 with P = 10.4 d.

Open cluster study in LAMOST DR3

2017 ◽  
Vol 13 (S334) ◽  
pp. 391-393
Author(s):  
Jing Zhong ◽  
Li Chen ◽  
Chaoli Zhang ◽  
Zhengyi Shao ◽  
Jinliang Hou
Keyword(s):  
Radial Velocity ◽  
Proper Motion ◽  
Open Cluster ◽  
Open Clusters ◽  
Projection Area ◽  
Distance Modulus ◽  
Membership Probability ◽  
Cluster Area ◽  
Large Projection ◽  
Cross Match

AbstractIn studying Galactic open clusters based on LAMOST DR3, we deliberately selected several nearby cluster, which have relatively large projection area and reliable proper motion measurements. For each cluster, we firstly determine the typical proper motion distribution profiles in the cluster-core and the outskirt region, respectively, and perform field-star decontamination on the cluster area. We then calculate kinematic membership probability for each star in the cluster area and cross-match the highly probable members with LAMOST DR3 spectral catalog. Based on enhanced signal of cluster-member radial velocity distribution emerging from the whole field, we have also obtained reliable radial velocity membership probability for each star. Finally, we perform isochrones fitting with MCMC technique to study basic properties of these cluster, including age, metallicity, and distance modulus.

scholarly journals RADIAL VELOCITIES AND METALLICITIES OF RED GIANT STARS IN THE OLD OPEN CLUSTER NGC 7762

2016 ◽  
Vol 152 (6) ◽  
pp. 224 ◽  
Author(s):  
Giovanni Carraro ◽  
Eugene A. Semenko ◽  
Sandro Villanova
Keyword(s):  
Open Cluster ◽  
Radial Velocities ◽  
Giant Stars ◽  
Red Giant Stars ◽  
Red Giant

scholarly journals The Gaia-ESO Survey: The inner disc, intermediate-age open cluster Pismis 18

2019 ◽  
Vol 626 ◽  
pp. A90 ◽  
Author(s):  
D. Hatzidimitriou ◽  
E. V. Held ◽  
E. Tognelli ◽  
A. Bragaglia ◽  
L. Magrini ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Proper Motion ◽  
Open Cluster ◽  
Open Clusters ◽  
High Resolution Spectroscopy ◽  
Distance Modulus ◽  
Chemical Abundance ◽  
High Confidence ◽  
Galactocentric Distance ◽  
Red Clump

Context. Pismis 18 is a moderately populated, intermediate-age open cluster located within the solar circle at a Galactocentric distance of about seven kpc. Few open clusters have been studied in detail in the inner disc region before the Gaia-ESO Survey. Aims. New data from the Gaia-ESO Survey allowed us to conduct an extended radial velocity membership study as well as spectroscopic metallicity and detailed chemical abundance measurements for this cluster. Methods. Gaia-ESO Survey data for 142 potential members, lying on the upper main sequence and on the red clump, yielded radial velocity measurements, which, together with proper motion measurements from the Gaia Second Data Release (Gaia DR2), were used to determine the systemic velocity of the cluster and membership of individual stars. Photometry from Gaia DR2 was used to re-determine cluster parameters based on high confidence member stars only. Cluster abundance measurements of six radial-velocity member stars with UVES high-resolution spectroscopy are presented for 23 elements. Results. The average radial velocity of 26 high confidence members is −27.5 ± 2.5 (std) km s−1 with an average proper motion of pmra = −5.65 ± 0.08 (std) mas yr−1 and pmdec = −2.29 ± 0.11 (std) mas yr−1. According to the new estimates, based on high confidence members, Pismis 18 has an age of τ = 700+40−50 Myr, interstellar reddening of E(B − V) = 0.562+0.012−0.026 mag and a de-reddened distance modulus of DM0 = 11.96+0.10−0.24 mag. The median metallicity of the cluster (using the six UVES stars) is [Fe/H] = +0.23 ± 0.05 dex, with [α/Fe] = 0.07 ± 0.13 and a slight enhancement of s- and r-neutron-capture elements. Conclusions. With the present work, we fully characterized the open cluster Pismis 18. We confirmed its present location in the inner disc. We estimated a younger age than the previous literature values and we gave, for the first time, its metallicity and its detailed abundances. Its [α/Fe] and [s-process/Fe], both slightly super-solar, are in agreement with other inner-disc open clusters observed by the Gaia-ESO survey.

scholarly journals Extended main sequence turnoffs in open clusters as seen by Gaia – II. The enigma of NGC 2509

2019 ◽  
Vol 491 (2) ◽  
pp. 2129-2136 ◽  
Author(s):  
M de Juan Ovelar ◽  
S Gossage ◽  
S Kamann ◽  
N Bastian ◽  
C Usher ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Main Sequence ◽  
Narrow Range ◽  
Open Cluster ◽  
Open Clusters ◽  
Stellar Rotation ◽  
Rotation Rates ◽  
Magnitude Diagram ◽  
Stellar Density

ABSTRACT We investigate the morphology of the colour–magnitude diagram (CMD) of the open cluster NGC 2509 in comparison with other Galactic open clusters of similar age using Gaia photometry. At ${\sim}900\,\rm {Myr}$ Galactic open clusters in our sample all show an extended main sequence turnoff (eMSTO) with the exception of NGC 2509, which presents an exceptionally narrow CMD. Our analysis of the Gaia data rules out differential extinction, stellar density, and binaries as a cause for the singular MSTO morphology in this cluster. We interpret this feature as a consequence of the stellar rotation distribution within the cluster and present the analysis with mesa Isochrones and Stellar Tracks (MIST) stellar evolution models that include the effect of stellar rotation on which we based our conclusion. In particular, these models point to an unusually narrow range of stellar rotation rates (Ω/Ωcrit, ZAMS = [0.4, 0.6]) within the cluster as the cause of this singular feature in the CMD of NGC 2509. Interestingly, models that do not include rotation are not as good at reproducing the morphology of the observed CMD in this cluster.

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