- ID:
- ivo://CDS.VizieR/J/other/ApSS/355.267
- Title:
- NGC 6811 CCD UBVRI photometry
- Short Name:
- J/other/ApSS/355
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of CCD UBVRI observations of the open cluster NGC 6811 obtained on 18th July 2012 with the 1m telescope at the TIBITAK National Observatory (TUG). Using these photometric results, we determine the structural and astrophysical parameters of the cluster. The mean photometric uncertainties are better than 0.02 mag in the V magnitude and B-V, V-R, and V-I colour indices to about 0.03mag for U-B among stars brighter than magnitude V=18. Cluster member stars were separated from the field stars using the Galaxia model of Sharma et al. (2011ApJ...730....3S) together with other techniques. The core radius of the cluster is found to be r_c_=3.60arcmin. The astrophysical parameters were determined simultaneously via Bayesian statistics using the colour-magnitude diagrams V versus B-V, V versus V-I, V versus V-R, and V versus R-I of the cluster. The resulting most likely parameters were further confirmed using independent methods, removing any possible degeneracies. The colour excess, distance modulus, metallicity and the age of the cluster are determined simultaneously as E(B-V)=0.05+/-0.01mag, {mu}=10.06+/-0.08mag, [M/H]=-0.10+/-0.01dex and t=1.00+/-0.05Gyr, respectively. Distances of five red clump stars which were found to be members of the cluster further confirm our distance estimation.
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- ID:
- ivo://CDS.VizieR/J/PASP/110/1318
- Title:
- NGC 7789 CCD VI photometry
- Short Name:
- J/PASP/110/1318
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A V, V-I-diagram for the intermediate-age open cluster NGC 7789 has been derived from CCD observations of more than 15,000 stars within ~18' of the cluster center. From the brightest giants and blue stragglers at V~11 to the faintest lower main-sequence stars that were observed (at V~21, M_V_~9), the color-magnitude diagram is well defined. A prominent clump of core helium-burning stars is evident at V=13.0, and the upper end of the main sequence shows a fairly pronounced curvature to the red, which is indicative of significant convective core overshooting. Indeed, comparisons with up-to-date stellar models show that it is not possible to explain the observed morphology in the vicinity of the turnoff unless the overshooting is quite extensive. Interestingly, if sufficient overshooting is assumed in order to match the main-sequence data, it is not possible to reproduce the cluster's extended giant branch unless the cluster age is at least 1.6 Gyr (assuming a metallicity in the range -0.2<=[FeMH]<=0.0). This, in turn, requires that the cluster have an apparent distance modulus m-M_V_<=12.2. Thus, sometime within the past few hundred million years, the ignition of helium burning in NGC 7789 has switched from a quiescent to an explosive ("flash") phenomenon, and the length of the cluster's red giant branch has been steadily increasing with the passage of time since then. From main-sequence fits to models that have been carefully normalized to the Sun, we infer a reddening 0.35<=E(V-I)<=0.38.
- ID:
- ivo://CDS.VizieR/J/ApJS/69/99
- Title:
- NGC 6334 centers of star formation JHK photometry
- Short Name:
- J/ApJS/69/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present near-infrared observations of specific sites of high-mass star formation activity in the giant H II region/molecular cloud complex NGC 6334. The observations consist of high-spatial resolution broad-band imaging, chopping photometry, and moderate-resolution spectra. The imaging observations provide full spatial sampling of the stellar population over a significant area of the cloud to a limit of K=13.5mag and reveal many faint red sources around the sites of recent high-mass star formation. We show that most of these sources are associated with the NGC 6334 molecular cloud and are not Galactic field sources. In the majority of the regions the embedded sources are primarily reddened main-sequence stars of low and intermediate mass though in three of the 11 regions studied there is a high proportion of objects showing H-K excesses which are therefore probably pre main-sequence. We identify the red objects in FIR-I as belonging to a very young compact cluster of ~1pc spatial extent. In FIR-V an unexpectedly large number of bright red sources are detected which have CO absorption at 2.3{mu}m. The probability that these objects are Galactic field sources is very low and if they are giant stars associated with NGC 6334 their implied ages (>10^9^yr) are inconsistent with the many indicators of extreme youth in this region. We propose that they form a hitherto unrecognized population of high-luminosity pre-main-sequence objects. Two objects with similar characteristics are also found in images of an area of the NGC 6334 molecular cloud to the north of FIR-V (SH-1). In FIR-V we also find evidence that the molecular outflow from the already known high-mass protostar has triggered intermediate-mass star formation via interaction with the local interstellar medium. Mass functions have been derived for the embedded stellar aggregates under the assumption that all sources lie on the main sequence unless otherwise indicated. The effect of a population of pre-main-sequence objects on the derived mass function slopes is shown to be small. Embedded aggregates in NGC 6334 have stellar mass distributions similar to those found both in young visible clusters and in other embedded clusters. This suggests that the slope of the mass function is relatively insensitive to conditions in the star formation environment and that the solar neighborhood value applies to star formation regions on scales as small as 1pc and of ages less than 10^7^yr.
- ID:
- ivo://CDS.VizieR/J/A+A/539/A74
- Title:
- NGC1893 Chandra X-ray catalog
- Short Name:
- J/A+A/539/A74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The outer Galaxy, where the environmental conditions are different from the solar neighbourhood is a laboratory in which it is possible to investigate the dependence of star formation process on the environmental parameters. We investigate the X-ray properties of NGC 1893, a young cluster (~1-2Myr) in the outer part of the Galaxy (galactic radius >=11kpc) where we expect differences in the disk evolution and in the mass distribution of the stars, to explore the X-ray emission of its members and compare it with that of young stars in star forming regions near to the Sun.
- ID:
- ivo://CDS.VizieR/J/ApJ/608/781
- Title:
- NGC 6530 Chandra X-ray catalog
- Short Name:
- J/ApJ/608/781
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a deep 60ks Chandra ACIS X-ray observation of the very young cluster NGC 6530, we detect 884 X-ray point sources and argue that a very large fraction of them (90%-95%) must be pre-main-sequence (PMS) cluster members, mostly of low masses. This is a significant enlargement of the known NGC 6530 stellar population with respect to previous optical studies, including H{alpha} surveys. We identify 220 X-ray sources with catalogued stars down to V=17, while most unidentified sources have fainter counterparts. Moreover, we find an infrared counterpart in the 2MASS (<II/246>) catalog for 731 X-ray sources. The optically identified cluster X-ray sources are found in a band in the H-R diagram above the main sequence, in the locus of 0.5-1.5Myr PMS stars, with masses down to 0.5-1.5M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/A+A/605/A85
- Title:
- NGC 3293 Chandra X-ray observation
- Short Name:
- J/A+A/605/A85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 3293 is a young stellar cluster at the northwestern periphery of the Carina Nebula Complex that remained poorly explored until now. We want to characterize the stellar population of NGC 3293 in order to evaluate key parameters of the cluster population like the age and the mass function, and to test claims of an abnormal IMF and a deficit of M<=2.5M_{sun}_ stars. WWe performed a deep (70 ksec) X-ray observation of NGC 3293 with Chandra and detected 1026 individual X-ray point sources. These X-ray data directly probe the low-mass (M<=2M_{sun}_) stellar population by means of the strong X-ray emission of young low-mass stars. We identify counterparts for 74% of the X-ray sources in our deep near-infrared images. Our data clearly show that NGC 3293 hosts a large population of ~solar-mass stars, refuting claims of a lack of M<=2.5M_{sun}_ stars. The analysis of the color-magnitude diagram suggests an age of ~8-10Myr for the low-mass population of the cluster. There are at least 511 X-ray detected stars with color-magnitude positions that are consistent with young stellar members within 7 arcmin from the cluster center. The number ratio of X-ray detected stars in the [1-2]M_{sun}_ range versus the M<=5M_{sun}_ stars (known from optical spectroscopy) is well consistent with the expectation from a normal field initial mass function. Most of the early B-type stars and ~20% of the later B-type stars are detected as X-ray sources. Our data shows that NGC 3293 is one of the most populous stellar clusters in the entire Carina Nebula Complex (only excelled by Tr 14, and very similar to Tr 16 and Tr 15). The cluster has probably harbored several O-type stars, the supernova explosions of which may have had an important impact on the early evolution of the Carina Nebula Complex.
- ID:
- ivo://CDS.VizieR/J/MNRAS/461/2519
- Title:
- NGC2548 clumpy spatial and kinematic structure
- Short Name:
- J/MNRAS/461/2519
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 2548 is a ~400-500Myr old open cluster with evidence of spatial substructures likely caused by its interaction with the Galactic disc. In this work we use precise astrometric data from the Carte du Ciel - San Fernando (CdC-SF) catalogue to study the clumpy structure in this cluster. We confirm the fragmented structure of NGC 2548 but, additionally, the relatively high precision of our kinematic data lead us to the first detection of substructures in the proper motion space of a stellar cluster. There are three spatially separated cores each of which has its own counterpart in the proper motion distribution. The two main cores lie nearly parallel to the Galactic plane whereas the third one is significantly fainter than the others and it moves towards the Galactic plane separating from the rest of the cluster. We derive core positions and proper motions, as well as the stars belonging to each core.
- ID:
- ivo://CDS.VizieR/J/A+AS/134/525
- Title:
- NGC 6611 compiled catalog
- Short Name:
- J/A+AS/134/525
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue contains data on stars in sky area of the open cluster NGC 6611. The catalogue is based on a new reduction of positions, proper motions, and photometric data whenever published in this region and includes among others, Hipparcos, AC/GSC and Tautenburg Schmidt plate observations. The basis of compiled catalogue is made of stars distributed over a circular area with radius of 22.8arcmin centered on the cluster NGC 6611 (Kharchenko and Schilbach, 1995AN....316...91K). To construct the compiled catalogue, we used also astrometric data published by Van Schewick (1962VeUSB..62....1V), Kamp (1974A&AS...16....1K), Tucholke et al. (1986A&AS...66..311T), Bastian and Roeser (1993, Cat. <I/193>), Roeser (1996, in "An updated GSC as the astrometric reference for minor planet observations", Kluwer Dordrecht, p. 481.), Hillenbrand et al. (1993, Cat. <J/AJ/106/1906>), and photometry published by Walker (1961ApJ...133..438W), Hoag et al. (1961PUSNO..17..343H), Hiltner and Morgan (1969AJ.....74.1152H), Sagar and Joshi (1979Ap&SS..66....3S), The et al (1990A&AS...82..319T), Hillenbrand et al. (1993, Cat. <J/AJ/106/1906>) as it described by Belikov et al. (1998, A&A, in press, this paper, 1999A&AS..134..525B). The catalogue contains 2185 stars up to the limiting magnitudes V=16.78mag. It includes equatorial (equinox 2000.0 and epoch 1990.77) and rectangular coordinates, absolute proper motions with respect to the Hipparcos proper motion system, photometric data (results of UBV, HJK photometry and color excess) and cluster membership probabilities. X - and Y - directions correspond to right ascension and declination directions. The rms errors of right ascension and declination are 0.008sec and 0.14arcsec, respectively. The individual rms errors of proper motions and V-magnitudes are given in the catalogue. The membership probabilities of the cluster stars belonging to the core and corona were determined using information both on spatial and proper motion distributions of stars in the field.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A16
- Title:
- NGC 6774 cool stars rotation periods
- Short Name:
- J/A+A/644/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gyrochronology allows the derivation of ages for cool main sequence stars based on their observed rotation periods and masses, or a suitable proxy thereof. It is increasingly well-explored for FGK stars, but requires further measurements for older ages and K-M-type stars. We study the 2.7Gyr-old open cluster Ruprecht 147 to compare it with the previously-studied, but far more distant, NGC 6819 cluster, and especially to measure cooler stars than was previously possible there. We constructed an inclusive list of 102 cluster members from prior work, including Gaia DR2, and for which light curves were also obtained during Campaign 7 of the Kepler/K2 space mission. We placed them in the cluster color-magnitude diagram and checked the related information against appropriate isochrones. The light curves were then corrected for data systematics using Principal Component Analysis on all observed K2 C07 stars and subsequently subjected to periodicity analysis. Periodic signals are found for 32 stars, 21 of which are considered to be both highly reliable and to represent single, or effectively single, Ru 147 stars. These stars cover the spectral types from late-F to mid-M stars, and they have periods ranging from 6d-33d, allowing for a comparison of Ruprecht 147 to both other open clusters and to models of rotational spindown. The derived rotation periods connect reasonably to, overlap with, and extend to lower masses the known rotation period distribution of the 2.5 Gyr-old cluster NGC 6819. The data confirm that cool stars lie on a single surface in rotation period-mass-age space, and they simultaneously challenge its commonly assumed shape. The shape at the low mass region of the color-period diagram at the age of Ru 147 favors a recently-proposed model which requires a third mass-dependent timescale in addition to the two timescales required by a former model, suggesting that a third physical process is required to model rotating stars effectively.
600. NGC 6819 3D members
- ID:
- ivo://CDS.VizieR/J/other/RAA/15.2193
- Title:
- NGC 6819 3D members
- Short Name:
- J/other/RAA/15.2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to obtain clean members of the open cluster NGC 6819, the proper motions and radial velocities of 1691 stars are used to construct a three-dimensional (3D) velocity space. Based on the DBSCAN clustering algorithm, 537 3D cluster members are obtained. From the 537 3D cluster members, the average radial velocity and absolute proper motion of the cluster are Vr=+2.30+/-0.04km/s and (PMRA, PMDE)=(-2.5+/-0.5, -4.3+/-0.5)mas/yr, respectively. The proper motions, radial velocities, spatial positions and color-magnitude diagram of the 537 3D members indicate that our membership determination is effective. Among the 537 3D cluster members, 15 red clump giants can be easily identified by eye and are used as reliable standard candles for the distance estimate of the cluster. The distance modulus of the cluster is determined to be (m-M)0=11.86+/-0.05mag (2355+/-54pc), which is quite consistent with published values. The uncertainty of our distance modulus is dominated by the intrinsic dispersion in the luminosities of red clump giants (~0.04mag).
