scholarly journals Analysis of the Open Cluster NGC 2281

Galaxies ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 7
Author(s):  
Dirk Terrell ◽  
John Gross ◽  
Walter R. Cooney
Keyword(s):  
Variable Star ◽  
American Association ◽  
Open Cluster ◽  
Standard System ◽  
Proper Motions ◽  
Eclipsing Binary ◽  
Photometric Observations ◽  
Sky Survey ◽  
Gaia Dr2

BV observations of an approximately 68′×48′ field centered on the open cluster NGC 2281 and covering more than 400 nights from 2013 to 2018 are presented. The photometric observations were transformed to the standard system using standards from the American Association of Variable Star Observers Photometric All-sky Survey (APASS) DR10 and analyzed with Gaia DR2 parallaxes and proper motions to determine the distance, age, and metallicity of the cluster. The discovery of an eclipsing binary in the field is discussed.

scholarly journals A revision of the vdB 130 cluster stellar content based on Gaia DR2 data: interstellar extinction toward the Cyg OB1 supershell

2020 ◽  
Vol 498 (4) ◽  
pp. 5437-5449
Author(s):  
T G Sitnik ◽  
A S Rastorguev ◽  
A A Tatarnikova ◽  
A M Tatarnikov ◽  
O V Egorov ◽  
...  
Keyword(s):  
Open Cluster ◽  
Interstellar Extinction ◽  
Proper Motions ◽  
Stellar Content ◽  
Star Forming ◽  
Star Forming Regions ◽  
Colour Excess ◽  
Photometric Observations ◽  
Trigonometric Parallaxes ◽  
Gaia Dr2

ABSTRACT Two star-forming regions are studied: the young embedded open cluster vdB 130 and the protocluster neighbourhood observed in the head and tail of the cometary molecular cloud located in the wall of the expanding supershell surrounding the Cyg OB1 association. The Gaia DR2 catalogue is employed to verify the stellar composition of the vdB 130 cluster whose members were earlier selected using the UCAC4 catalogue. The new sample of vdB 130 members contains 68 stars with close proper motions (within 1 mas yr−1) and close trigonometric parallaxes (ranging from 0.50–0.70 mas). The relative parallax error is shown to increase with distance to objects and depend on their magnitude. At a distance of 1.5–2 kpc it is of about 3–7 per cent and 20–30 per cent for bright and faint stars, respectively. The cluster is not older than ∼10 Myr. New spectroscopic and photometric observations carried out on Russian telescopes are combined with Gaia DR2 to search for optical components in the protocluster region – a new starburst. An analysis of 20 stars in the vicinity of the protocluster revealed no concentration of either proper motions or parallaxes. According to spectroscopic, photometric and trigonometric estimates, the distances to these stars range from 0.4–2.5 kpc, and colour excess is shown to increase with a distance D (kpc) in accordance with the law E(B − V) ≃ 0.6 × D mag.

scholarly journals The extended main-sequence turn-off of the Milky Way open cluster Collinder 347

2019 ◽  
Vol 490 (2) ◽  
pp. 2414-2420 ◽  
Author(s):  
Andrés E Piatti ◽  
Charles Bonatto
Keyword(s):  
Main Sequence ◽  
Milky Way ◽  
Open Cluster ◽  
Age Difference ◽  
Proper Motions ◽  
Gaussian Distributions ◽  
Young Object ◽  
Magnitude Diagram ◽  
Chemical Content ◽  
Gaia Dr2

ABSTRACT We made use of the Gaia DR2 archive to comprehensively study the Milky Way open cluster Collinder 347, known until now as a very young object of solar metal content. However, the G versus GBP − GRP colour–magnitude diagram (CMD) of bonafide probable cluster members, selected on the basis of individual stellar proper motions, their spatial distribution, and placement in the CMD, reveals the existence of a Hyades-like age open cluster (log(t /yr) = 8.8) of moderately metal-poor chemical content ([Fe/H]  = −0.4 dex), with a present-day mass of 3.3 × 103 M⊙. The cluster exhibits an extended main-sequence turn-off (eMSTO) of nearly 500 Myr, while that computed assuming Gaussian distributions from photometric errors, stellar binarity, rotation, and metallicity spread yields an eMSTO of ∼340 Myr. Such an age difference points to the existence within the cluster of stellar populations with different ages.

scholarly journals Stellar population of Sco OB2 revealed by Gaia DR2 data

2019 ◽  
Vol 623 ◽  
pp. A112 ◽  
Author(s):  
F. Damiani ◽  
L. Prisinzano ◽  
I. Pillitteri ◽  
G. Micela ◽  
S. Sciortino
Keyword(s):  
Stellar Population ◽  
Main Sequence ◽  
Open Cluster ◽  
Proper Motions ◽  
Lower Mass ◽  
Global Pattern ◽  
Field Star ◽  
Photometric Measurements ◽  
Stellar Masses ◽  
Gaia Dr2

Context. The Sco OB2 association is the nearest OB association, extending over approximately 2000 square degrees on the sky. Only its brightest and most massive members are already known (from HIPPARCOS) across its entire size, while studies of its lower mass population refer only to small portions of its extent. Aims. In this work we exploit the capabilities of Gaia DR2 measurements to search for Sco OB2 members across its entire size and down to the lowest stellar masses. Methods. We used both Gaia astrometric (proper motions and parallaxes) and photometric measurements (integrated photometry and colors) to select association members, using minimal assumptions derived mostly from the HIPPARCOS studies. Gaia resolves small details in both the kinematics of individual Sco OB2 subgroups and their distribution with distance from the Sun. We developed methods to explore the 3D kinematics of a stellar population covering large sky areas. Results. We find nearly 11 000 pre-main-sequence (PMS) members of Sco OB2 (with less than 3% field-star contamination), plus ∼3600 main-sequence (MS) candidate members with a larger (10–30%) field-star contamination. A higher confidence subsample of ∼9200 PMS (and ∼1340 MS) members is also selected (<1% contamination for the PMS), however this group is affected by larger (∼15%) incompleteness. We separately classify stars in compact and diffuse populations. Most members belong to one of several kinematically distinct diffuse populations, whose ensemble clearly outlines the shape of the entire association. Upper Sco is the densest region of Sco OB2. It is characterized by a complex spatial and kinematical structure and has no global pattern of motion. Other dense subclusters are found in Lower Centaurus-Crux and in Upper Centaurus-Lupus; the richest example of the latter, which has been recently identified, is coincident with the group near V1062 Sco. Most of the clustered stars appear to be younger than the diffuse PMS population, suggesting star formation in small groups that rapidly disperse and are diluted, reaching space densities lower than field stars while keeping memory of their original kinematics. We also find that the open cluster IC 2602 has a similar dynamics to Sco OB2, and its PMS members are currently evaporating and forming a diffuse (size ∼10°) halo around its double-peaked core.

scholarly journals A Variable Star Survey of the Open Cluster NGC 2126

2004 ◽  
Vol 193 ◽  
pp. 162-165
Author(s):  
A. Derekas ◽  
L.L. Kiss ◽  
T.R. Bedding ◽  
A. Gáspár ◽  
K. Sárneczky ◽  
...  
Keyword(s):  
Variable Star ◽  
Open Cluster ◽  
Variable Stars ◽  
Time Span ◽  
Photometric Observations

AbstractWe present the first CCD photometric observations of the northern open cluster NGC 2126. Data were taken on eight nights in 2002 February and December with a total time span of ~57 hours. We have discovered six new variable stars and have estimated the main characteristics of the cluster.

A cluster of intermediate age in the Large Magellanic Cloud

1964 ◽  
Vol 20 ◽  
pp. 347-348
Author(s):  
Richard Woolley
Keyword(s):  
Variable Star ◽  
Open Cluster ◽  
Large Magellanic Cloud ◽  
Proper Motions ◽  
Giant Stars ◽  
Tight Cluster ◽  
Faint Object ◽  
Bright Blue ◽  
Star Field ◽  
Hr Diagram

Some years ago (1960) I discussed the HR diagram of the variable star field investigated at Herstmonceux as the result of Drs. Sandage and Eggen's visit to Pretoria, and found colour-luminosity arrays showing mainly very blue giant stars; and later (1961) I suggested that a second and older population could be seen in the same area of the LMC, showing a rather different x,y distribution. Recently Miss Epps has assisted me to make further investigations into the matter. We are now discussing stars fainter than V = 14 · 5 and therefore too faint for us to determine their proper motions. In order to get rid of foreground stars which obscure the HR diagram we have had to make use of the x, y distribution to discriminate between LMC members and foreground stars. Firstly, we examined an open cluster which appears as a faint object on the 74-inch Pretoria plates. It is away from the main lane occupied by the bright blue objects, and its appearance on the B and V plates showed it not to be excessively blue. On a Radcliffe plate (74 in. stopped to 44 in.) with an exposure of 20 min, 29 stars can be seen within a circle of diameter of 1′ of arc. We have been able to determine V accurately for only 15 of these stars, one of which proved to be a variable of period 4–75 days. The HR diagram shows a gap between B – V = 0 · 2 and B – V = 1 · 0, the variable being in this gap. It is comparable with those of NGC 129, NGC 2287, and NGC 6067, and, by analogy with these objects, the open cluster now described probably has an age of about 108 years. The object is of course very different from the young or blue (but tight) cluster NGC 1818 not far away from it.

scholarly journals AN ASTROMETRIC AND PHOTOMETRIC STUDY OF THE INTERMEDIATE-AGE OPEN CLUSTER NGC 2158 AND ITS ECLIPSING BINARY [NBN2015]78

2020 ◽  
Vol 56 (2) ◽  
pp. 245-257
Author(s):  
A. E. Abdelaziz ◽  
Y. H. M. Hendy ◽  
A. Shokry ◽  
S. M. Saad ◽  
F. Y. Kamal ◽  
...  
Keyword(s):  
Open Cluster ◽  
Distance Modulus ◽  
Mass Ratio ◽  
Photometric Analysis ◽  
Eclipsing Binary ◽  
Color Excess ◽  
Contact Binary ◽  
Cluster Age ◽  
Gaia Dr2 ◽  
Intrinsic Distance

We present a photometric and astrometric analysis of the NGC 2158 cluster using Gaia DR2 and 2MASS data. The cluster age, color excess, intrinsic distance modulus and distance are calculated to be t = 2.240 ± 0.260 Gyr, E(B − V) = 0.420 ± 0.050 mag, (m − M)⨀ = 12.540 ± 0.130 mag and d⨀ = 3224 ± 200 pc respectively. The photometric analysis and light curve modelling of the proposed eclipsing binary member [NBN2015]78 is performed using the latest version of the Wilson-Devinney (W-D) code. The solutions show that the system is an over-contact binary with a secondary component filling its Roche lobe, with a mass ratio q = 0.262. The primary and the secondary components of the system consist of two late spectral types K1 and K2 respectively. The membership of [NBN2015]78 is discussed using two independent methods, and we find that [NBN2015]78 is an interloper and not a member of NGC 2158.

scholarly journals ML-MOC: Machine Learning (kNN and GMM) based Membership determination for Open Clusters

2021 ◽  
Vol 502 (2) ◽  
pp. 2582-2599
Author(s):  
Manan Agarwal ◽  
Khushboo K Rao ◽  
Kaushar Vaidya ◽  
Souradeep Bhattacharya
Keyword(s):  
Machine Learning ◽  
Open Cluster ◽  
A Priori ◽  
Gaussian Mixture ◽  
Open Clusters ◽  
Proper Motions ◽  
Cluster Membership ◽  
Priori Information ◽  
Gaia Dr2 ◽  
Good Agreement

ABSTRACT The existing open-cluster membership determination algorithms are either prior dependent on some known parameters of clusters or are not automatable to large samples of clusters. In this paper, we present ml-moc, a new machine-learning-based approach to identify likely members of open clusters using the Gaia DR2 data and no a priori information about cluster parameters. We use the k-nearest neighbour (kNN) algorithm and the Gaussian mixture model (GMM) on high-precision proper motions and parallax measurements from the Gaia DR2 data to determine the membership probabilities of individual sources down to G ∼ 20 mag. To validate the developed method, we apply it to 15 open clusters: M67, NGC 2099, NGC 2141, NGC 2243, NGC 2539, NGC 6253, NGC 6405, NGC 6791, NGC 7044, NGC 7142, NGC 752, Blanco 1, Berkeley 18, IC 4651, and Hyades. These clusters differ in terms of their ages, distances, metallicities, and extinctions and cover a wide parameter space in proper motions and parallaxes with respect to the field population. The extracted members produce clean colour–magnitude diagrams and our astrometric parameters of the clusters are in good agreement with the values derived in previous work. The estimated degree of contamination in the extracted members ranges between 2 ${{\ \rm per\ cent}}$ and 12 ${{\ \rm per\ cent}}$. The results show that ml-moc is a reliable approach to segregate open-cluster members from field stars.

scholarly journals Diva - A Small Satellite for Global Astrometry and Photometry

1998 ◽  
Vol 11 (1) ◽  
pp. 583-583
Author(s):  
S. Röser ◽  
U. Bastian ◽  
K.S. de Boer ◽  
E. Høg ◽  
E. Schilbach ◽  
...  
Keyword(s):  
High Precision ◽  
Wavelength Range ◽  
Fizeau Interferometer ◽  
Proper Motions ◽  
Small Satellite ◽  
Short Overview ◽  
Photometric Observations ◽  
Photometric Measurements ◽  
First Time ◽  
Astronomy And Astrophysics

DIVA (Double Interferometer for Visual Astrometry) is a Fizeau interferometer on a small satellite. It will perform astrometric and photometric observations of at least 4 million stars. A launch in 2002 and a minimum mission length of 24 months are aimed at. A detailed description of the experiment can be obtained from the DIVA homepage at http://www.aip.de:8080/᷉dso/diva. An overview is given by Röser et al., 1997. The limiting magnitude of DIVA is about V = 15 for spectral types earlier than M0, but drops to about V = 17.5 for stars later than M5. Table 1 gives a short overview on DIVA’s performance. DIVA will carry out a skysurvey complete to V = 12.5. For the first time this survey will comprise precise photometry in at least 8 bands in the wavelength range from 400 to 1000 nm. DIVA will improve parallaxes by a factor of 3 compared to Hipparcos; proper motions by at least a factor of 2 and, in combination with the Hipparcos observations, by a factor of 10 for Hipparcos stars. At least 30 times asmany stars as Hipparcos will be observed, and doing this DIVA will fill the gap in observations between Hipparcos and GAIA. DIVA’s combined astrometric and photometric measurements of high precision will have important impacts on astronomy and astrophysics in the next decade.

scholarly journals Gaia DR2 reveals a very massive runaway star ejected from R136

2018 ◽  
Vol 619 ◽  
pp. A78 ◽  
Author(s):  
D. J. Lennon ◽  
C. J. Evans ◽  
R. P. van der Marel ◽  
J. Anderson ◽  
I. Platais ◽  
...  
Keyword(s):  
Lower Limit ◽  
Proper Motion ◽  
Evolutionary History ◽  
Massive Star ◽  
Position Angle ◽  
Proper Motions ◽  
Central Cluster ◽  
Dynamical Constraints ◽  
Runaway Stars ◽  
Gaia Dr2

A previous spectroscopic study identified the very massive O2 III star VFTS 16 in the Tarantula Nebula as a runaway star based on its peculiar line-of-sight velocity. We use the Gaia DR2 catalog to measure the relative proper motion of VFTS 16 and nearby bright stars to test if this star might have been ejected from the central cluster, R136, via dynamical ejection. We find that the position angle and magnitude of the relative proper motion (0.338±0.046 mas yr−1, or approximately 80±11 km s−1) of VFTS 16 are consistent with ejection from R136 approximately 1.5±0.2 Myr ago, very soon after the cluster was formed. There is some tension with the presumed age of VFTS 16 that, from published stellar parameters, cannot be greater than 0.9+0.3−0.2 Myr. Older ages for this star would appear to be prohibited due to the absence of He I lines in its optical spectrum, since this sets a firm lower limit on its effective temperature. The dynamical constraints may imply an unusual evolutionary history for this object, perhaps indicating it is a merger product. Gaia DR2 also confirms that another very massive star in the Tarantula Nebula, VFTS 72 (alias BI 253; O2 III-V(n)((f*)), is also a runaway on the basis of its proper motion as measured by Gaia. While its tangential proper motion (0.392±0.062 mas yr−1 or 93±15 km s−1) would be consistent with dynamical ejection from R136 approximately 1 Myr ago, its position angle is discrepant with this direction at the 2σ level. From their Gaia DR2 proper motions we conclude that the two ∼100 M⊙ O2 stars, VFTS 16 and VFTS 72, are fast runaway stars, with space velocities of around 100 km s−1 relative to R136 and the local massive star population. The dynamics of VFTS 16 are consistent with it having been ejected from R136, and this star therefore sets a robust lower limit on the age of the central cluster of ∼1.3 Myr.

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.

Sign in / Sign up

Export Citation Format

Share Document