- ID:
- ivo://CDS.VizieR/J/A+A/351/526
- Title:
- NGC 2172 CCD BVI photometry
- Short Name:
- J/A+A/351/526
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new CCD photometry for the young LMC cluster NGC 2172, giving B, V, I magnitudes for more than 600 stars within 70" from the cluster center, down to -approximately- V=21mag. After correction for completeness and field stars contamination, we discuss the cluster HR diagram and the MS luminosity function in the light of current evolutionary theories and in connection with the problem of cluster age.
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- ID:
- ivo://CDS.VizieR/J/PASP/117/22
- Title:
- NGC 6318 CCD BVI photometry
- Short Name:
- J/PASP/117/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD BVI photometry for the southern open cluster NGC 6318. The sample consists of 9876 stars measured in an area of 13.6'x13.6', extending down to V~21.5mag. Star counts carried out within and outside the cluster region allowed us to estimate the cluster angular radius as 8'.
- ID:
- ivo://CDS.VizieR/J/other/ApSS/361.126
- Title:
- NGC 6819 CCD UBV photometry
- Short Name:
- J/other/ApSS/361
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of CCD UBV observations of the open cluster NGC 6819. We calculated the stellar density profile in the cluster's field to determine the structural parameters of NGC 6819. Using the existing astrometric data, we calculated the probabilities of the stars being physical members of the cluster, and used these objects in the determination of the astrophysical parameters of NGC 6819. We inferred the reddening and metallicity of the cluster as E(B-V)=0.130+/-0.035mag and [Fe/H]=+0.051+/-0.020dex, respectively, using the U-B vs B-V two-colour diagram and UV excesses of the F-G type main-sequence stars. We fit the colour-magnitude diagrams of NGC 6819 with the PARSEC isochrones and derived the distance modula, distance and age of the cluster as mu_V=12.22+/-0.10mag, d=2309+/-106pc and t=2.4+/-0.2Gyr, respectively. The parameters of the galactic orbit estimated for NGC 6819 indicate that the cluster is orbiting in a slightly eccentric orbit of e=0.06 with a period of P_orb_=142Myr. The slope of the mass function estimated for the cluster is close to the one found for the stars in the solar neighbourhood.
- 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.
- 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.