- ID:
- ivo://CDS.VizieR/J/AJ/158/35
- Title:
- Swift UVOT Stars Survey. III. Galactic open clusters
- Short Name:
- J/AJ/158/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of the Swift/Ultraviolet-Optical Telescope Stars Survey, we present near-ultraviolet (NUV; 3000-1700 {AA}) point-source photometry for 103 Galactic open clusters. These data, taken over the span of the mission, provide a unique and unprecedented set of NUV point-source photometry on simple stellar populations. After applying a membership analysis fueled mostly by Gaia DR2 (Cat. I/345) proper motions, we find that 49 of these 103 have clear precise color-magnitude diagrams (CMDs) amenable to investigation. We compare the CMDs to theoretical isochrones and find good agreement between the theoretical isochrones and the CMDs. The exceptions are the fainter parts of the main sequence and the red giant branch in the uvw2-uvw1 CMDs, which is most likely due to either the difficulty of correcting for the red leak in the uvw2 filter or limitations in our understanding of UV opacities for cool stars. For the most part, our derived cluster parameters - age, distance, and reddening - agree with the consensus literature, but we find a few clusters that warrant substantial revision from literature values, notably NGC 2304, NGC 2343, NGC 2360, NGC 2396, NGC 2428, NGC 2509, NGC 2533, NGC 2571, NGC 2818, Collinder 220, and NGC 6939. A number of these are clusters in the third Galactic quadrant, where previous studies may have mistaken the disk sequence for the cluster. However, the Gaia DR2 proper motions clearly favor a different sequence. A number of clusters also show white dwarf and blue straggler sequences. We confirm the presence of extended main-sequence turnoffs in NGC 2360 and NGC 2818 and show hints of them in a number of other clusters that may warrant future spectroscopic study. Most of the clusters in the study have low extinction, and the rest are well fit by a "Milky Way-like" extinction law. However, Collinder 220 hints at a possible "LMC-like" extinction law. We finally provide a comprehensive point-source catalog to the community as a tool for future investigation.
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- ID:
- ivo://CDS.VizieR/J/A+A/622/A111
- Title:
- Systematic diff. in spectroscopic analysis
- Short Name:
- J/A+A/622/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A spectroscopic analysis of stellar spectra can be carried out using multiple approaches such as different methods, line lists, atmospheric models, atomic parameters, and solar abundances. The resulting atmospheric parameters from these choices can vary beyond the quoted uncertainties in the literature. We characterize these differences by systematically comparing some of the commonly adopted ingredients such as line lists, equivalent width measurements, and atomic parameters. High-resolution and high signal-to-noise (S/N) spectroscopic data of one helium-core-burning red giant star in each of the three open clusters, NGC 6819, M67, and NGC 188 were obtained with the FIES spectrograph at the Nordic Optical Telescope. The M67 target was used to benchmark the analysis, as it is a well-studied cluster with asteroseismic data from the K2 mission. For the other two clusters we obtained higher quality data than had been analyzed before, which allows us to establish their chemical composition more securely. Using a line by line analysis, we tested several different combinations of line lists and programs to measure equivalent widths of stellar absorption lines to characterize systematic differences within the same spectroscopic method. The obtained parameters for the benchmark star in M67 vary up to ~170K in effective temperature, ~0.4dex in logg and ~0.25dex in [Fe/H] between the tested setups. Using the combination of an equivalent width measurement program and line list that best reproduce the inferred surface gravity from asteroseismology, we determined the atmospheric parameters for the three stars and securely established the chemical composition of NGC 6819 to be close to solar, [Fe/H]=-0.02+/-0.01dex. We highlighted the significantly different results obtained with different combinations of line lists, programs, and atomic parameters. The results emphasize the importance of benchmark stars studied with several methods to anchor spectroscopic analyses.
- ID:
- ivo://CDS.VizieR/J/A+A/566/A132
- Title:
- Teff and L for stars in 7 open clusters
- Short Name:
- J/A+A/566/A132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To study the time evolution of magnetic fields, chemical abundance peculiarities, and other characteristics of magnetic Ap and Bp stars during their main sequence lives, a sample of these stars in open clusters has been obtained, as such stars can be assumed to have the same ages as the clusters to which they belong. However, in exploring age determinations in the literature, we find a large dispersion among different age determinations, even for bright, nearby clusters. Our aim is to obtain ages that are as accurate as possible for the seven nearby open clusters {alpha} Per, Coma Ber, IC 2602, NGC 2232, NGC 2451A, NGC 2516, and NGC 6475, each of which contains at least one magnetic Ap or Bp star. Simultaneously, we test the current calibrations of T_e_ and luminosity for the Ap/Bp star members, and identify clearly blue stragglers in the clusters studied. We explore the possibility that isochrone fitting in the theoretical Hertzsprung-Russell diagram (i.e. log(L/L_{sun}_) vs. logT_e_), rather than in the conventional colour-magnitude diagram, can provide more precise and accurate cluster ages, with well-defined uncertainties.
- ID:
- ivo://CDS.VizieR/J/ApJS/159/100
- Title:
- Temperatures and Rc photometry in the Hyades
- Short Name:
- J/ApJS/159/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using Hyades photometry published by Mendoza (1967BOTT....4..149M) and other authors, Pinsonneault et al. (2004ApJ...600..946P) have recently concluded that Cousins V-I photometry published by Taylor & Joner (1985AJ.....90..479T, 1988AJ.....96..211T, 1996AJ....111.1338T) is not on the Cousins system. Extensive tests of the Taylor-Joner photometry and other pertinent results are therefore performed in this paper. It is found that in part, the Pinsonneault et al. conclusion rests on (1) a systematic error in Mendoza's (R-I)J photometry and (2) a small error in an approximate Johnson-to-Cousins transformation published by Bessell. For the Taylor-Joner values of (V-R)C, it is found that there are possible (though not definite) differences of several mmag with other results. However, the Taylor-Joner values of (R-I)C data are supported at the 1mmag level. Using the (R-I)C data and other published results, an (R-I)C catalog is assembled for 146 Hyades stars with spectral types earlier than about K5. For single stars with multiple contributing data, the rms errors of the catalog entries are less than 4.4 mmag. Temperatures on the Di Benedetto angular-diameter scale are also given in the catalog and are used to help update published analyses of high-dispersion values of [Fe/H] for the Hyades. The best current mean Hyades value of [Fe/H] is found to be +0.103+/-0.008dex and is essentially unchanged from its previous value. In addition to these numerical results, recommendations are made about improving attitudes and practices that are pertinent to issues like those raised by Pinsonneault et al.
- ID:
- ivo://CDS.VizieR/J/A+A/615/A49
- Title:
- TGAS stars membership in 128 open clusters
- Short Name:
- J/A+A/615/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Tycho-Gaia Astrometric Solution (TGAS) subset of the first Gaia catalogue contains an unprecedented sample of proper motions and parallaxes for two million stars brighter than G~12 mag. We take advantage of the full astrometric solution available for those stars to identify the members of known open clusters and compute mean cluster parameters using either TGAS or UCAC4 proper motions, and TGAS parallaxes. We apply an unsupervised membership assignment procedure to select high probability cluster members, we use a Bayesian/MCMC technique to fit stellar isochrones to the observed 2MASS JHK magnitudes of the member stars and derive cluster parameters (age, metallicity, extinction, distance modulus), and we combine TGAS data with spectroscopic radial velocities to compute full Galactic orbits. We obtain mean astrometric parameters (proper motions and parallaxes) for 128 clusters closer than about 2kpc, and cluster parameters from isochrone fitting for 26 of them located inside 1kpc from us. We show the orbital parameters obtained from integrating 36 orbits in a Galactic potential.
- ID:
- ivo://CDS.VizieR/VII/183
- Title:
- The Cluster System of the LMC
- Short Name:
- VII/183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new catalogue of clusters in the Large Magellanic Cloud has been constructed from searches of the IIIa-J component of the ESO/SERC Southern Sky Atlas. The catalogue contains coordinate and diameter measurements of 1762 clusters in a 25x25{deg} area of sky centred on the LMC, but excluding the very crowded 3.5 square deg. region around the Bar. The distribution of these clusters appears as two superimposed elliptical systems. The higher density inner system extends over about 8d; the lower density outer system can be represented by 13d X 10d disc inclined at 42d to the line of sight. There are suggestions of two weak "arms" in the latter.
- ID:
- ivo://CDS.VizieR/J/ApJ/718/683
- Title:
- The edge of the young Galactic disk
- Short Name:
- J/ApJ/718/683
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work, we report and discuss the detection of two distant diffuse stellar groups in the third Galactic quadrant. They are composed of young stars, with spectral types ranging from late O to late B, and lie at galactocentric distances between 15 and 20kpc. These groups are located in the area of two cataloged open clusters (VdB-Hagen 04 and Ruprecht 30), projected toward the Vela-Puppis constellations, and within the core of the Canis Major overdensity. Their reddening and distances have been estimated by analyzing their color-color and color-magnitude diagrams, derived from deep UBV photometry. The existence of young star aggregates at such extreme distances from the Galactic center challenges the commonly accepted scenario in which the Galactic disk has a sharp cutoff at about 14kpc from the Galactic center and indicates that it extends to much greater distances (as also supported by the recent detection of CO molecular complexes well beyond this distance). While the groups we find in the area of Ruprecht 30 are compatible with the Orion and Norma-Cygnus spiral arms, respectively, the distant group we identify in the region of VdB-Hagen 04 lies in the external regions of the Norma-Cygnus arm, at a galactocentric distance (~20kpc) where no young stars have been detected so far in the optical.
- ID:
- ivo://CDS.VizieR/J/A+A/341/98
- Title:
- The ionizing cluster of 30 Doradus. I.
- Short Name:
- J/A+A/341/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- UBV profile fitting photometry is presented for 1469 stars within 90arcsec of the center of the ionizing cluster of 30 Doradus (NGC 2070). A value of 0.82+/-0.03 is found for the extinction parameter S=E(U-B)/E(B-V), constant over almost the whole area covered by this research, with some evidence for local variations. Two reddening components can be identified: a smooth and moderate one that increases towards R136, and a clumpy one varying widely across the face of the cluster. The total-to-selective extinction parameter, R_V_= A_V_/E(B-V), is found to be in the range of 3.0 to 3.7, consistent with previous determinations. A new visualization tool, the colour-magnitude stereogram, is introduced and used to argue that: (1) the observations imply mass segregation in a dust filled cluster; (2) that there has been continuous dust formation near the cluster core up to the present; and (3) that an insidious systematic error has plagued previous determinations of IMF slopes. A method to obtain an unbiased estimate of the slope is discussed.
1089. The Mayrit catalogue
- ID:
- ivo://CDS.VizieR/J/A+A/478/667
- Title:
- The Mayrit catalogue
- Short Name:
- J/A+A/478/667
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The young sigma Orionis cluster is an indispensable basis for understanding the formation and evolution of stars, brown dwarfs and planetary-mass objects. Our knowledge of its stellar population is, however, incomplete. I present the Mayrit catalogue, that comprises most of the stars and high-mass brown dwarfs of the cluster. The basis of this work is an optical-near infrared correlation between the 2MASS and DENIS catalogues in a circular area of radius 30 arcmin centred on the OB-type binary sigma Ori AB. The analysis is supported on a bibliographic search of confirmed cluster members with features of youth and on additional X-ray, mid-infrared and astrometric data. I list 241 sigma Orionis stars and brown dwarfs with known features of youth, 97 candidate cluster members (40 are new) and 115 back- and foreground sources in the survey area. The 338 cluster members and member candidates constitute the Mayrit catalogue. This catalogue is a suitable input for studying the spatial distribution, multiplicity, properties and frequency of discs and the complete mass function of sigma Orionis.
- ID:
- ivo://CDS.VizieR/J/ApJS/209/31
- Title:
- The MYStIX IR-Excess Source catalog (MIRES)
- Short Name:
- J/ApJS/209/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Massive Young Star-Forming Complex Study in Infrared and X-rays (MYStIX) project provides a comparative study of 20 Galactic massive star-forming complexes (d=0.4-3.6kpc). Probable stellar members in each target complex are identified using X-ray and/or infrared data via two pathways: X-ray detections of young/massive stars with coronal activity/strong winds or (2) infrared excess (IRE) selection of young stellar objects (YSOs) with circumstellar disks and/or protostellar envelopes. We present the methodology for the second pathway using Spitzer/IRAC, 2MASS, and UKIRT imaging and photometry. Although IRE selection of YSOs is well-trodden territory, MYStIX presents unique challenges. The target complexes range from relatively nearby clouds in uncrowded fields located toward the outer Galaxy (e.g., NGC 2264, the Flame Nebula) to more distant, massive complexes situated along complicated, inner Galaxy sightlines (e.g., NGC 6357, M17). We combine IR spectral energy distribution (SED) fitting with IR color cuts and spatial clustering analysis to identify IRE sources and isolate probable YSO members in each MYStIX target field from the myriad types of contaminating sources that can resemble YSOs: extragalactic sources, evolved stars, nebular knots, and even unassociated foreground/background YSOs. Applying our methodology consistently across 18 of the target complexes, we produce the MYStIX IRE Source (MIRES) Catalog comprising 20719 sources, including 8686 probable stellar members of the MYStIX target complexes. We also classify the SEDs of 9365 IR counterparts to MYStIX X-ray sources to assist the first pathway, the identification of X-ray-detected stellar members.