scholarly journals Exploring open cluster properties with Gaia and LAMOST

2020 ◽  
Vol 640 ◽  
pp. A127
Author(s):  
Jing Zhong ◽  
Li Chen ◽  
Di Wu ◽  
Lu Li ◽  
Leya Bai ◽  
...  
Keyword(s):  
Open Cluster ◽  
Open Clusters ◽  
Reliable Determination ◽  
Spectroscopic Parameters ◽  
Orbital Parameters ◽  
Spectroscopic Observations ◽  
Fundamental Properties ◽  
Cluster Properties ◽  
Stellar Properties ◽  
High Level

Context. In Gaia DR2, an unprecedented high level of precision has been reached at sub-milliarcsecond for astrometry and millimagnitudes for photometry. Using cluster members identified with the astrometry and photometry in Gaia DR2, we can obtain a reliable determination of cluster properties. However, because of the shortcomings of Gaia spectroscopic observations in dealing with densely crowded cluster regions, the RVs and metallicity values for cluster member stars from Gaia DR2 are still lacking. It is necessary to combine the Gaia data with the data from large spectroscopic surveys, such as LAMOST, APOGEE, GALAH, and Gaia-ESO. Aims. In this study our aim is to improve the cluster properties by combining the LAMOST spectra. In particular, we provide the list of cluster members with spectroscopic parameters as an add-value catalog in LAMOST DR5, which can be used to perform a detailed study for a better understanding of the stellar properties, by using their spectra and fundamental properties from the host cluster. Methods. We cross-matched the spectroscopic catalog in LAMOST DR5 with the identified cluster members in Cantat-Gaudin et al. (2018, A&A, 618, A93). We then used members with spectroscopic parameters to derive statistical properties of open clusters. Results. We obtained a list of 8811 members with spectroscopic parameters and a catalog of 295 cluster properties. The provided cluster properties include astrometric parameters, spectroscopic parameters, derived kinematic and orbital parameters, and isochrone fitting results. In addition, we study the radial and vertical metallicity gradient and age-metallicity relation with the compiled open clusters as tracers, finding slopes of −0.053 ± 0.004 dex kpc−1, −0.252 ± 0.039 dex kpc−1, and 0.022 ± 0.008 dex Gyr−1, respectively. The slopes of the metallicity distribution relation for young clusters (0.1 Gyr < Age < 2 Gyr) and the age-metallicity relation for clusters within 6 Gyr are both consistent with the literature results. In order to fully study the chemical evolution history in the disk, more spectroscopic observations for old and distant open clusters are needed for further investigation.

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.

scholarly journals Study of open cluster NGC 5617 in Gaia era

2019 ◽  
Vol 14 (S353) ◽  
pp. 22-23
Author(s):  
D. Bisht ◽  
Qingfeng Zhu
Keyword(s):  
Data Base ◽  
Proper Motion ◽  
Open Cluster ◽  
Open Clusters ◽  
Fundamental Parameters ◽  
Magnitude Diagram ◽  
Cluster Properties ◽  
Open Question ◽  
Gaia Dr2

AbstractIdentification of member stars in open clusters is still an open question. Thanks to Gaia DR2 data base, which improves our statistics regarding true members in clusters to understand cluster properties much better way. In this paper, we identify the cluster members using proper motion and colour magnitude diagram for NGC 5617. In addition to this, we have determined more precise fundamental parameters as well.

scholarly journals Orbital Parameters and Binary Properties of 37 FGK Stars in the Cores of Open Clusters NGC 2516 and NGC 2422

2021 ◽  
Vol 162 (6) ◽  
pp. 285
Author(s):  
Isabel Lipartito ◽  
John I. Bailey III ◽  
Timothy D. Brandt ◽  
Benjamin A. Mazin ◽  
Mario Mateo ◽  
...  
Keyword(s):  
Open Cluster ◽  
Open Clusters ◽  
Spectroscopic Binaries ◽  
Proper Motions ◽  
Orbital Eccentricity ◽  
Critical Window ◽  
Cluster Membership ◽  
Orbital Parameters ◽  
Keplerian Orbits ◽  
Cluster Cores

Abstract We present orbits for 24 binaries in the field of open cluster NGC 2516 (∼150 Myr) and 13 binaries in the field of open cluster NGC 2422 (∼130 Myr) using results from a multiyear radial-velocity (RV) survey of the cluster cores. Six of these systems are double-lined spectroscopic binaries. We fit these RV variable systems with orvara, a MCMC-based fitting program that models Keplerian orbits. We use precise stellar parallaxes and proper motions from Gaia EDR3 to determine cluster membership. We impose a barycentric RV prior on all cluster members; this significantly improves our orbital constraints. Two of our systems have periods between five and 15 days, the critical window in which tides efficiently damp orbital eccentricity. These binaries should be included in future analyses of circularization across similarly-aged clusters. We also find a relatively flat distribution of binary mass ratios, consistent with previous work. With the inclusion of TESS light curves for all available targets, we identity target 378–036252 as a new eclipsing binary. We also identify a field star whose secondary has a mass in the brown dwarf range, as well as two cluster members whose RVs suggest the presence of an additional companion. Our orbital fits will help constrain the binary fraction and binary properties across stellar age and across stellar environment.

scholarly journals Formation rate of LB-1-like systems through dynamical interactions

2020 ◽  
Vol 72 (3) ◽  
Author(s):  
Ataru Tanikawa ◽  
Tomoya Kinugawa ◽  
Jun Kumamoto ◽  
Michiko S Fujii
Keyword(s):  
Open Cluster ◽  
Formation Rate ◽  
Open Clusters ◽  
Type Star ◽  
Dynamical Mechanism ◽  
Milky Way Galaxy ◽  
Triple Systems ◽  
Stellar Collisions ◽  
Solar Metallicity ◽  
Helium Star

Abstract We estimate formation rates of LB-1-like systems through dynamical interactions in the framework of the theory of stellar evolution before the discovery of the LB-1 system. The LB-1 system contains a ∼70 ${M_{\odot}}$ black hole (BH), a so-called pair instability (PI) gap BH, and a B-type star with solar metallicity, and has nearly zero eccentricity. The most efficient formation mechanism is as follows. In an open cluster, a naked helium star (with ∼20 ${M_{\odot}}$) collides with a heavy main sequence star (with ∼50 ${M_{\odot}}$) which has a B-type companion. The collision results in a binary consisting of the collision product and the B-type star with a high eccentricity. The binary can be circularized through the dynamical tide with radiative damping of the collision product envelope. Finally, the collision product collapses to a PI-gap BH, avoiding pulsational pair instability and pair instability supernovae because its He core is as massive as the pre-colliding naked He star. We find that the number of LB-1-like systems in the Milky Way galaxy is ∼0.01(ρoc/104 ${M_{\odot}}$ pc−3), where ρoc is the initial mass densities of open clusters. If we take into account LB-1-like systems with O-type companion stars, the number increases to ∼0.03(ρoc/104 ${M_{\odot}}$ pc−3). This mechanism can form LB-1-like systems at least ten times more efficiently than the other mechanisms: captures of B-type stars by PI-gap BHs, stellar collisions between other types of stars, and stellar mergers in hierarchical triple systems. We conclude that no dynamical mechanism can explain the presence of the LB-1 system.

scholarly journals X-Ray Coronae from Stars

1998 ◽  
Vol 188 ◽  
pp. 13-16
Author(s):  
R. Pallavicini
Keyword(s):  
Open Clusters ◽  
Temperature Structure ◽  
List Type ◽  
Star Forming ◽  
Spectroscopic Observations ◽  
Star Forming Regions ◽  
Complete Mapping ◽  
Sky Survey ◽  
Order Of Magnitude ◽  
Age Range

A number of major advances in stellar coronal physics have occurred since 1990 mainly as a consequence of imaging observations by ROSAT and spectroscopic observations by ASCA. These can be summarised as follows: 1.an all-sky survey has been performed by ROSAT at a sensitivity of ~ 2 × 10−13 erg cm−2 s−1, complemented by pointed observations an order of magnitude deeper;2.complete mapping and deeper pointings have been obtained for virtually all open clusters closer than ~ 500 pc, and covering the age range from ~ 30 Myr to ~ 700 Myr;3.complete mapping and deeper paintings have been obtained for several Star Forming Regions (SFRs) covering the age range ~ 1 to ~ 10 Myr;4.spectroscopic observations of bright coronal sources have been obtained with EUVE and ASCA allowing the derivation of the temperature structure and elemental abundances.

scholarly journals Refining the true parameters of the open cluster NGC 4852

2009 ◽  
Vol 5 (S266) ◽  
pp. 539-539
Author(s):  
Gladys Solivella ◽  
Edgard Giorg ◽  
Rubén Vázquez ◽  
Giovanni Carraro
Keyword(s):  
Emission Line ◽  
Open Cluster ◽  
Open Clusters ◽  
Occurrence Rate ◽  
Hot Stars ◽  
Cluster Area ◽  
Young Object ◽  
Cluster Distance ◽  
Be Star ◽  
Compact Cluster

AbstractNGC 4852 is a moderately compact cluster centered at α2000 = 13 : 00 : 09; δ = −59 : 36 : 48, located near the center of an Hα superring. This cluster forms part of an extended region including young stellar aggregates inside a circle with a radius of 3 degrees, where many show an abundance of emission line stars. In the field of this cluster, two stars of known type exist: Wray 15–1039 (emission-line object) and CD −58:4845 (emission-line star). We do not yet know whether the Be phase is transient or whether it is just what randomly happens in some hot stars. It appears that Be star may be found even in clusters as old as 70 Myr with a high occurrence rate in clusters of 25–27 Myr old. A recent photometric survey in NGC 4852 down to V = 22 – 23 mag established that NGC 4852 is about 200 – 250 Myr old, located at 1.1 kpc from the Sun and with a mean E(B − V) = 0.45 mag. Since the presence of potential Be-type stars in the cluster area suggests it may be a very young object instead of moderately old, we decided to carry out spectroscopy for 33 selected stars and CCD UBVI photometry for the bright objects in the cluster area. This way, we attempt to clarify their evolutionary state and include them in the framework of emission-line stars and open clusters. From our analysis, we agree with the cluster distance and reddening determined by earlier studies, but we derive that the age of NGC 4852 is younger than 40 Myr.

scholarly journals Defining the Binary Star Population in the Young Open Cluster M35 (NGC 2168)

2007 ◽  
Vol 3 (S246) ◽  
pp. 105-106
Author(s):  
Ella K. Braden ◽  
Robert D. Mathieu ◽  
Sören Meibom
Keyword(s):  
Binary Systems ◽  
Initial Conditions ◽  
Binary Star ◽  
Open Cluster ◽  
Open Clusters ◽  
Spatial Period ◽  
Large Sample Size ◽  
Long Baseline ◽  
Dynamical Simulations ◽  
Young Open Cluster

AbstractWe present current results from the ongoing WIYN Open Cluster Study radial-velocity survey for 1410 stars in the young (150 Myr) open cluster M35 (NGC 2168) and establish a benchmark for initial conditions in young open clusters. We find for periods ≲ 1000 days a minimum binary frequency of 0.36 – 0.51. We also analyze the spatial, period and eccentricity distributions of the binary systems and find that the period and eccentricity distributions are well approximated by scaled field distributions from Duquennoy & Mayor (1991). With our large sample size and long baseline, we have a unique understanding of the binary population in this young cluster, making it ideal for defining initial conditions for dynamical simulations.

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 Characterising open clusters in the solar neighbourhood with the Tycho-Gaia Astrometric Solution

2018 ◽  
Vol 615 ◽  
pp. A49 ◽  
Author(s):  
T. Cantat-Gaudin ◽  
A. Vallenari ◽  
R. Sordo ◽  
F. Pensabene ◽  
A. Krone-Martins ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Markov Chain ◽  
High Probability ◽  
Open Clusters ◽  
Distance Modulus ◽  
The Sun ◽  
Proper Motions ◽  
Orbital Parameters ◽  
Naval Observatory ◽  
Galactic Potential

Context. The Tycho-Gaia Astrometric Solution (TGAS) subset of the first Gaia catalogue contains an unprecedented sample of proper motions and parallaxes for two million stars brighter than G ~ 12 mag. Aims. We take advantage of the full astrometric solution available for those stars to identify the members of known open clusters and compute mean cluster parameters using either TGAS or the fourth U.S. Naval Observatory CCD Astrograph Catalog (UCAC4) proper motions, and TGAS parallaxes. Methods. We apply an unsupervised membership assignment procedure to select high probability cluster members, we use a Bayesian/Markov Chain Monte Carlo technique to fit stellar isochrones to the observed 2MASS JHKS magnitudes of the member stars and derive cluster parameters (age, metallicity, extinction, distance modulus), and we combine TGAS data with spectroscopic radial velocities to compute full Galactic orbits. Results. We obtain mean astrometric parameters (proper motions and parallaxes) for 128 clusters closer than about 2 kpc, and cluster parameters from isochrone fitting for 26 of them located within a distance of 1 kpc from the Sun. We show the orbital parameters obtained from integrating 36 orbits in a Galactic potential.

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