- ID:
- ivo://CDS.VizieR/J/A+A/631/A124
- Title:
- NGC 2345 Stroemgren photometry
- Short Name:
- J/A+A/631/A124
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 2345 is a young open cluster hosting seven blue and red supergiants, low metallicity and a high fraction of Be stars which makes it a privileged laboratory to study stellar evolution. We aim to improve the determination of the cluster parameters and study the Be phenomenon. Our objective is also to characterise its seven evolved stars by deriving their atmospheric parameters and chemical abundances. We performed a complete analysis combining for the first time ubvy photometry with spectroscopy as well as Gaia Data Release 2. We obtained spectra with classification purposes for 76 stars and high-resolution spectroscopy for an in-depth analysis of the blue and red evolved stars. We identify a new red supergiant and 145 B-type likely members within a radius of 18.7+/-1.2arcmin, which implies an initial mass, M_cl_~5,200M_{sun}_. We find a distance of 2.5+/-0.2kpc for NGC 2345, placing it at R_GC_=10.2+/-0.2kpc. Isochrone fitting supports an age of 56+/-13Ma, implying masses around 6.5M_{sun}_ for the supergiants. A high fraction of Be stars (~10%) is found. From the spectral analysis we estimate for the cluster an average v_rad}_=+58.6+/-0.5km/1 and a low metallicity, [Fe/H]=-0.28+/-0.07. We also have determined chemical abundances for Li, O, Na, Mg, Si, Ca, Ti, Ni, Rb, Y, and Ba for the evolved stars. The chemical composition of the cluster is consistent with that of the Galactic thin disc. One of the K supergiants, S50, is a Li-rich star, presenting an A(Li)~2.1. An overabundance of Ba is found, supporting the enhanced s-process. NGC 2345 has a low metallicity for its Galactocentric distance, comparable to typical LMC stars. It is massive enough to serve as a testbed for theoretical evolutionary models for massive intermediate-mass stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/609/A10
- Title:
- NGC2264 structure and star formation history
- Short Name:
- J/A+A/609/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Reconstructing the structure and history of young clusters is pivotal to understanding the mechanisms and timescales of early stellar evolution and planet formation. Recent studies suggest that star clusters often exhibit a hierarchical structure, possibly resulting from several star formation episodes occurring sequentially rather than a monolithic cloud collapse. We aim to explore the structure of the open cluster and star-forming region NGC 2264 (~3Myr), which is one of the youngest, richest and most accessible star clusters in the local spiral arm of our Galaxy; we link the spatial distribution of cluster members to other stellar properties such as age and evolutionary stage to probe the star formation history within the region. We combined spectroscopic data obtained as part of the Gaia-ESO Survey (GES) with multi-wavelength photometric data from the Coordinated Synoptic Investigation of NGC 2264 (CSI 2264) campaign. We examined a sample of 655 cluster members, with masses between 0.2 and 1.8M_{sun}_ and including both disk-bearing and disk-free young stars. We used Teff estimates from GES and g,r,i photometry from CSI 2264 to derive individual extinction and stellar parameters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/484/5102
- Title:
- NGC 6383 T Tauri accretion rates
- Short Name:
- J/MNRAS/484/5102
- Date:
- 03 Nov 2021 13:02:39
- Publisher:
- CDS
- Description:
- This paper presents optical (ugriH{alpha})-infrared (JHKs, 3.6-8.0um) photometry and Gaia astrometry of 55 Classical T-Tauri stars (CTTS) in the star-forming region Sh 2-012 and its central cluster NGC 6383. The sample was identified based on photometric H{alpha} emission linewidths, and has a median age of 2.8+/-1.6Myr, with a mass range between 0.3 and 1M_{sun}_. 94 per cent of CTTS with near-infrared cross-matches fall on the near-infrared T-Tauri locus, with all stars having mid-infrared photometry exhibiting evidence for accreting circumstellar discs. CTTS are found concentrated around the central cluster NGC 6383, and towards the bright rims located at the edges of Sh 2-012. Stars across the region have similar ages, suggestive of a single burst of star formation. Mass accretion rates dMacc/dt) estimated via H{alpha} and u-band line intensities show a scatter (0.3dex) similar to spectroscopic studies, indicating the suitability of H{alpha} photometry to estimate dMacc/dt. Examining the variation of dMacc/dt with stellar mass (M*), we find a smaller intercept in the (dMacc/dt)-M* relation than oft-quoted in the literature, providing evidence to discriminate between competing theories of protoplanetary disc evolution.
- ID:
- ivo://CDS.VizieR/J/MNRAS/429/1981
- Title:
- NGC 2264 T Tauri star properties
- Short Name:
- J/MNRAS/429/1981
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- There are many pertinent open issues in the area of star and planet formation. Large statistical samples of young stars across star-forming regions are needed to trigger a breakthrough in our understanding, but most optical studies are based on a wide variety of spectrographs and analysis methods, which introduces large biases. Here we show how graphical Bayesian networks can be employed to construct a hierarchical probabilistic model which allows pre-main-sequence ages, masses, accretion rates and extinctions to be estimated using two widely available photometric survey data bases (Isaac Newton Telescope Photometric H{alpha} Survey r'/H{alpha}/i' and Two Micron All Sky Survey J-band magnitudes). Because our approach does not rely on spectroscopy, it can easily be applied to homogeneously study the large number of clusters for which Gaia will yield membership lists. We explain how the analysis is carried out using the Markov chain Monte Carlo method and provide python source code. We then demonstrate its use on 587 known low-mass members of the star-forming region NGC 2264 (Cone Nebula), arriving at a median age of 3.0Myr, an accretion fraction of 20+/-2 per cent and a median accretion rate of 10-8.4M{sun}/yr. The Bayesian analysis formulated in this work delivers results which are in agreement with spectroscopic studies already in the literature, but achieves this with great efficiency by depending only on photometry. It is a significant step forward from previous photometric studies because the probabilistic approach ensures that nuisance parameters, such as extinction and distance, are fully included in the analysis with a clear picture on any degeneracies.
- ID:
- ivo://CDS.VizieR/J/AJ/142/127
- Title:
- NGC 5822 UBVI and uvbyCaH{beta} photometry
- Short Name:
- J/AJ/142/127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 5822 is a richly populated, moderately nearby, intermediate-age open cluster covering an area larger than the full moon on the sky. A CCD survey of the cluster on the UBVI and uvbyCaH{beta} systems shows that the cluster is superposed upon a heavily reddened field of background stars with E(B-V)>0.35mag, while the cluster has small and uniform reddening at E(b-y)=0.075+/-0.008mag or E(B-V)=0.103+/-0.011mag, based upon 48 and 61 probable A and F dwarf single-star members, respectively. The errors quoted include both internal photometric precision and external photometric uncertainties.
- ID:
- ivo://CDS.VizieR/J/MNRAS/309/739
- Title:
- NGC 2660 UBVIc photometry
- Short Name:
- J/MNRAS/309/739
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD UBVI photometry of the intermediate old open cluster NGC 2660, covering from the red giant region to about seven magnitudes below the main sequence turn-off. Using the synthetic colour-magnitude diagram method, we estimate in a self-consistent way values for distance modulus [(m-M)_0_~12.2], reddening [E(B-V)~0.40], metallicity ([Fe/H] about solar) and age (t<=1Gyr). A 30 per cent population of binary stars turns out to be probably present.
- ID:
- ivo://CDS.VizieR/J/AcA/59/349
- Title:
- NGC 1502 UBVIc photometry
- Short Name:
- J/AcA/59/349
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of variability search in the field of the young open cluster NGC 1502. Eight variable stars were discovered. Of six other stars in the observed field that were suspected for variability, we confirm variability of two, including one beta Cep star, NGC 1502-26. The remaining four suspects were found to be constant in our photometry. In addition, UBVIc photometry of the well-known massive eclipsing binary SZ Cam was obtained.
- ID:
- ivo://CDS.VizieR/J/MNRAS/224/61
- Title:
- NGC 6649 UBV photometry
- Short Name:
- J/MNRAS/224/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A colour magnitude diagram to V=20 is given for 395 stars in the heavily reddened open cluster NGC 6649. The absorption-corrected distance modulus is 11.00+/-0.15mag (1585+/-110pc) assuming R(OB)=3.27+/-0.10 for NGC 6649 and based on a ZAMS with zero point referenced to a Pleiades distance modulus of 5.56mag. The range of reddening over the 5arcmin diameter of the cluster is {DELTA}E(B-V)=0.3mag. NGC 6649 contains the double mode Cepheid V367 Sct, which has <M_V_>=-3.80+/-0.06 and <B_0_>-<V_0_>=0.58+/-0.02.
- ID:
- ivo://CDS.VizieR/J/AJ/115/734
- Title:
- NGC 6231 UBVRI and H{alpha} photometry
- Short Name:
- J/AJ/115/734
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- UBVRI and H{alpha} CCD photometry has been obtained for the young open cluster NGC 6231. From the R-H{alpha} color, a measure of the H{alpha} emission, we find 12 pre-main-sequence (PMS) members and seven possible PMS members in the cluster. Applying recent stellar evolutionary tracks and PMS evolutionary tracks, we derive the age, age spread, and initial mass function of the cluster. The initial mass function of NGC 6231 is a Gaussian with a turnover at logm~0.4 (m~2.5M_{Sun}_) and shows an abrupt decrease in the number of low-mass stars. Possible reasons for the suppression of low-mass star formation and star formation processes are discussed.
- ID:
- ivo://CDS.VizieR/J/MNRAS/453/1095
- Title:
- NGC 6866 UBVRI photometry
- Short Name:
- J/MNRAS/453/1095
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD UBVRI photometry of the field of the open cluster NGC 6866. Structural parameters of the cluster are determined utilizing the stellar density profile of the stars in the field. We calculate the probabilities of the stars being physical members of the cluster, using their astrometric data, and perform further analyses using only the most probable members. The reddening and metallicity of the cluster were determined by independent methods. The LAMOST spectra and the ultraviolet excess of the F- and G-type main-sequence stars in the cluster indicate that the metallicity of the cluster is about the solar value. We estimated the reddening E(B-V)=0.074+/-0.050mag using the U-B versus B-V two-colour diagram. The distance modula, the distance and the age of NGC 6866 were derived as {mu}=10.60+/-0.10mag, d=1189+/-75pc and t=813+/-50Myr, respectively, by fitting colour-magnitude diagrams of the cluster with the PARSEC isochrones. The Galactic orbit of NGC 6866 indicates that the cluster is orbiting in a slightly eccentric orbit with e=0.12. The mass function slope x=1.35+/-0.08 was derived by using the most probable members of the cluster.
