- ID:
- ivo://CDS.VizieR/J/ApJ/856/152
- Title:
- New star clusters in the central plane region
- Short Name:
- J/ApJ/856/152
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of new star clusters in the central plane region (|l|<30{deg} and |b|<6{deg}) of the Milky Way. In order to overcome the extinction problem and the spatial limit of previous surveys, we use the Wide-field Infrared Survey Explorer (WISE) data to find clusters. We also use other infrared survey data in the archive for additional analysis. We find 923 new clusters, of which 202 clusters are embedded clusters. These clusters are concentrated toward the Galactic plane and show a symmetric distribution with respect to the Galactic latitude. The embedded clusters show a stronger concentration to the Galactic plane than the nonembedded clusters. The new clusters are found more in the first Galactic quadrant, while previously known clusters are found more in the fourth Galactic quadrant. The spatial distribution of the combined sample of known clusters and new clusters is approximately symmetric with respect to the Galactic longitude. We estimate reddenings, distances, and relative ages of the 15 class A clusters using theoretical isochrones. Ten of them are relatively old (age >800Myr) and five are young (age ~4Myr).
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/365/447
- Title:
- New stellar members of Coma Berenices cluster
- Short Name:
- J/MNRAS/365/447
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a survey of the Coma Berenices open star cluster (Melotte 111), undertaken using proper motions from the USNO-B1.0 (United States Naval Observatory, <I/284>) and photometry from the Two-Micron All-Sky Survey (2MASS, <II/246>) Point Source catalogues. We have identified 60 new candidate members with masses in the range 1.007<M<0.269M_{sun}_. For each we have estimated a membership probability by extracting control clusters from the proper motion vector diagram. All 60 are found to have greater than 60 per cent probability of being members, more than doubling the number of known cluster members. The new luminosity function for the cluster peaks at bright magnitudes, but is rising at K>>12, indicating that it is likely that lower mass members may exist. The mass function also supports this hypothesis.
- ID:
- ivo://CDS.VizieR/J/other/NewA/49.50
- Title:
- New Variables in 3 Galactic open clusters
- Short Name:
- J/other/NewA/49.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This project is a massive near-infrared (NIR) search for variable stars in highly reddened and obscured open cluster (OC) fields projected on regions of the Galactic bulge and disk. The search is performed using photometric NIR data in the J-, H- and Ks - bands obtained from the Vista Variables in the Via Lactea (VVV) Survey. We performed in each cluster field a variability search using Stetson's variability statistics to select the variable candidates. Later, those candidates were subjected to a frequency analysis using the Generalized Lomb-Scargle and the Phase Dispersion Minimization algorithms. The number of independent observations range between 63 and 73. The newly discovered variables in this study, 157 in total in three different known OCs, are classified based on their light curve shapes, periods, amplitudes and their location in the corresponding color-magnitude (J-Ks,Ks)(J-Ks,Ks) and color-color (H-Ks,J-H)(H-Ks,J-H) diagrams. We found 5 possible Cepheid stars which, based on the period-luminosity relation, are very likely type II Cepheids located behind the bulge. Among the newly discovered variables, there are eclipsing binaries, {delta} Scuti, as well as background RR Lyrae stars. Using the new version of the Wilson & Devinney code as well as the "Physics Of Eclipsing Binaries" (PHOEBE) code, we analyzed some of the best eclipsing binaries we discovered. Our results show that these studied systems turn out to be ranging from detached to double-contact binaries, with low eccentricities and high inclinations of approximately 80{deg}. Their surface temperatures range between 3500K and 8000K.
574. New variables in ONC
- ID:
- ivo://CDS.VizieR/J/MNRAS/400/603
- Title:
- New variables in ONC
- Short Name:
- J/MNRAS/400/603
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Since 2004, we have been engaged in a long-term observing programme to monitor young stellar objects (YSOs) in the Orion Nebula Cluster (ONC). We have collected about 2000 frames in V, R and I broad-band filters on more than 200 nights distributed over five consecutive observing seasons. The high-quality and time-extended photometric data give us an opportunity to address various phenomena associated with young stars.
- ID:
- ivo://CDS.VizieR/J/AJ/106/1906
- Title:
- NGC 6611: A Cluster Caught in the Act
- Short Name:
- J/AJ/106/1906
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have combined optical CCD photometry and spectroscopy with infrared imaging photometry to study the young cluster NGC 6611. We use these data to derive improved values for the reddening law (R=3.75) and the distance modulus (m-M=11.5), and to construct a physical H-R diagram from which we can probe the ages, masses, and evolutionary states of this stellar ensemble. The H-R diagram shows a strong population of high-mass stars, the most massive of which has a mass of roughly 80 solar masses, similar to what we find in other Galactic and Magellanic Cloud clusters and associations. The age of the massive stellar population in NGC 6611 is approximately 2 million years, with an age spread of, perhaps, a million years, although the data are also consistent with there being no discernible age spread among the most massive stars. However, the H-R diagram does reveal that one star of somewhat lower mass (30 solar masses) must have formed approximately 6 million years ago. The upper end of the mass function of NGC 6611 is found to have a slope of Gamma=-1.1+/-0.3, indistinguishable from a Salpeter slope, and similar to what we have found in other Galactic associations, but shallower than what we have found in the Magellanic Clouds. Our most significant result, however, is that we catch this cluster in the act of forming intermediate mass (3-8 Solar masses) stars. This is the first well-established case where large numbers of intermediate-mass stars have been seen on their way to the zero-age main sequence. That intermediate mass pre-main sequence stars are indeed present is evidenced both by their location above the zero-age main sequence in the H-R diagram, and in some cases by their spectroscopic and infrared signatures of (possibly remnant protostellar) circumstellar material. The pre-main sequence population ranges from as young as 0.25 million years to at least 1 million years of age. We find an highly unusual number (27) of emission-line stars, which appear quite similar in their optical and infrared continuum and optical spectroscopic properties to "classical Be/Ae" stars (as opposed to Herbig Be/Ae stars). Our data are inconsistent with the traditional interpretation that these "classical Be/Ae" stars are slightly evolved stars undergoing mass loss. Instead, we offer the conjecture that these may be young stars whose circumstellar disks have become optically thin, and produce Balmer emission lines. The infrared data do indicate a number of stars, particularly amongst the embedded sample, whose colors are consistent with those of stars thought to be surrounded by optically thick circumstellar accretion disks. The identification of such disks around young massive stars continues to be rare, and implies that the disk survival times around intermediate and high mass stars are much shorter (< 0.5Myr) than those of disks surrounding lower mass stars.
- ID:
- ivo://CDS.VizieR/J/A+A/542/A68
- Title:
- NGC 3231, 7055 and 7127 BVRI photometry
- Short Name:
- J/A+A/542/A68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Open clusters are often used as tracers for the formation and evolution of the Milky Way. But they can also be used to study distinct "local stellar populations" and all kind of stellar groups. All these studies crucially depend on their unambiguous detection and classification separating them from the fore- and background field population. Still more than one third of the catalogued galactic open clusters are unstudied to date. We have chosen three northern open cluster fields, namely NGC 3231, NGC 7055, and NGC 7127 which have been never studied before to shed more light on their true nature. We present Johnson-Cousins BVRI photometry down to V=19mag. After the transformation to the standard systems, colour-magnitude diagrams were generated. These diagrams were used to fit solar abundant isochrones to determine the distance modulus, reddening and apparent age of the main sequences. From the analysis of the colour-magnitude diagrams and the available proper motions we conclude that NGC 7055 and NGC 7127 are young, real, open clusters. NGC 3231, on the other hand, is probably a high galactic latitude open cluster remnant.
- 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/531/A73
- Title:
- NGC 6167 and NGC 6193 multi-photometry
- Short Name:
- J/A+A/531/A73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Ara OB1a association is a nearby complex in the fourth Galactic quadrant where a number of young/embedded star clusters are projected close to more evolved, intermediate age clusters. It is also rich in interstellar matter, and contains evidences of the interplay between massive stars and their surrounding medium, like the rim HII region NGC 6188. We provide more solid estimates of the fundamental parameters (age and distance) of the two most prominent stellar clusters, NGC 6167 and NGC 6193, that may be used as a basis to study the star formation history of the region. The study is based on a photometric optical survey (UBVIHa) of NGC 6167 and NGC 6193 and their nearby field, complemented with public data from 2MASS-VVV, UCAC3 and IRAC-Spitzer in this region. We produced a uniform photometric catalogue and we estimated more robustly the fundamental parameters for NGC 6167, NGC 6193 and the IRAS 16375-4854 source. As a consequence, all of them are located at approximately the same distance from the Sun in the Sagittarius-Carina Galactic arm. However, the ages we estimated differ widely: NGC 6167 results to be an intermediate-age cluster (20-30Myr), NGC 6193 a very young one (1-5Myr) with PMS, H{alpha} emitters, and class II objects; and the IRAS 16375-4854 source is revealed as the youngest of the three containing several YSOs. These results support a picture in which Ara OB1a is a region where star formation has proceeded for several tens of Myr up to the present. The difference in ages of different stellar groups can be interpreted as a consequence of a triggered star formation process. Additionally, in the specific case of NGC 6193, an indication of possible non-coeval star formation was found.
- ID:
- ivo://CDS.VizieR/J/A+AS/133/387
- Title:
- NGC 1817 and NGC 1807 proper motions
- Short Name:
- J/A+AS/133/387
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Relative proper motions, their corresponding errors and membership probabilities of 722 stars in the open cluster NGC 1817 region are given. Equatorial coordinates were computed using Tycho Catalog (Cat. <I/239>) as reference stars. Forty stars from this catalog are in the region under study. The cross-identification of this 40 stars are given as notes. Only 15 stars were found in this region from the PPM Catalog (Cat. <I/146>), and their respective identification is also included in the note5.dat file.
- ID:
- ivo://CDS.VizieR/J/AJ/141/58
- Title:
- NGC 2204 and NGC 2243 red giant abundances
- Short Name:
- J/AJ/141/58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Detailed element abundances have been determined for 10-13 stars each in the open clusters (OCs) NGC 2204 and NGC 2243 based on Hydra multi-object echelle spectra obtained with the CTIO 4m telescope. We have found average cluster metallicities of [Fe/H]=-0.23+/-0.04 and -0.42+/-0.05 for NGC 2204 and NGC 2243, respectively, from an equivalent width analysis.
