- ID:
- ivo://CDS.VizieR/J/AJ/134/1216
- Title:
- Abundances of NGC 7142, 6939, and IC 4756 stars
- Short Name:
- J/AJ/134/1216
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of echelle spectra of stars in three open clusters obtained with the Hydra multiobject spectrograph on the WIYN 3.5m telescope. Abundances of Fe, O, Si, Ca, Na, Al, and Ni have been determined via equivalent width analysis and spectrum synthesis. Mean abundances for each cluster are compared to those of previous studies and of other clusters in the literature, with emphasis on exploring the enhancements of Na and Al seen in many open clusters. All three clusters show enhanced values of [Na/Fe] and [Al/Fe], while the abundances of Fe, O, Si, and Ca are consistent with their ages and locations in the Galactic disk.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/431/933
- Title:
- Abundances of NGC 7789 evolved stars
- Short Name:
- J/A+A/431/933
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution spectra of six giants and three core-helium-burning "clump" stars in the open cluster NGC 7789 have been obtained with the SOFIN spectrograph on the Nordic Optical Telescope to investigate abundances of up to 20 chemical elements. Abundances of carbon were studied using the C_2_ Swan (0, 1) band head at 5635.5{AA}. The wavelength interval 7980-8130{AA} with strong CN features was analysed in order to determine nitrogen abundances and ^12^C/^13^C isotope ratios. The oxygen abundances were determined from the [O I] line at 6300{AA}.
- ID:
- ivo://CDS.VizieR/J/ApJ/660/1462
- Title:
- Abundances of ONC X-ray PMS stars
- Short Name:
- J/ApJ/660/1462
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Following the Chandra Orion Ultradeep Project (COUP) observation, we have studied the chemical composition of the hot plasma in a sample of 146 X-ray-bright pre-main-sequence stars in the Orion Nebula Cluster (ONC). We report measurements of individual element abundances for a subsample of 86 slightly absorbed and bright X-ray sources, using low-resolution X-ray spectra obtained from the Chandra ACIS instrument.
- ID:
- ivo://CDS.VizieR/J/MNRAS/428/2321
- Title:
- Abundances of open cluster stars
- Short Name:
- J/MNRAS/428/2321
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The first generation of large-scale chemical tagging surveys, in particular the High Efficiency and Resolution Multi-Element Spectrograph (HERMES)/Galactic Archaeology with HERMES million star survey, promises to vastly expand our understanding of the chemical and dynamical evolution of the Galaxy. This, however, is contingent on our ability to confidently perform chemical tagging on such a large data set. Chemical homogeneity has been observed across a range of elements within several Galactic open clusters, yet the level to which this is the case globally, and particularly in comparison to the scatter across clusters themselves, is not well understood. The patterns of elements in coeval cluster members, occupying a complex chemical abundance space, are rooted in the evolution, ultimately the nature of the very late stages, of early generations of stars. The current astrophysical models of such stages are not yet sufficient to explain all observations, combining with our significant gaps in the understanding of star formation, makes this a difficult arena to tackle theoretically. Here, we describe a robust pair-wise metric used to gauge the chemical difference between two stellar components. This metric is then applied to a data base of high-resolution literature abundance sources to derive a function describing the probability that two stars are of common evolutionary origin. With this cluster probability function, it will be possible to report a confidence, grounded in empirical observational evidence, with which clusters are detected, independent of the group finding methods. This formulation is also used to probe the role of chemical dimensionality, and that of individual chemical species, on the ability of chemical tagging to differentiate coeval groups of stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/446/3562
- Title:
- Abundances of red giants in NGC752
- Short Name:
- J/MNRAS/446/3562
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present detailed chemical compositions of 10 red giant star members of the Galactic (open) cluster NGC 752, derived from high-resolution (R~60000), high signal-to-noise (S/N>=140) spectra. We confirmed cluster memberships by measuring the stellar radial velocities, and by deriving model atmosphere parameters (Teff, logg, [Fe/H] and {xi}t) from equivalent widths of FeI, FeII, TiI, and TiII lines. The metallicity we obtained for NGC 752 ([Fe/H]=-0.02+/-0.05) is in good agreement with previous studies. We derived abundances of alpha (Mg, Si, Ca), light odd-Z (Na, Al), Fe-group (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn), n-capture (Y, La, Nd, Eu), and p-capture (Li, C, N, O) species for each star. Furthermore, we also derived abundances of the LiCNO p-capture element group and carbon isotopic ratios, using synthetic spectrum analyses of the LiI 6707{AA} resonance doublet, the [OI] line at 6300{AA}, the CH G-band features near 4311 and 4325{AA}, the C_2_ bandheads at 5160 and 563{AA}, and ^12,13^CN red system lines in the 7995-8040{AA} region. By applying recent isochrones to NGC 752 photometry, and comparing the colour-magnitude diagram information to our Li abundances and 12C/13C ratios, we suggest that the 10 observed red giants can be separated into three first-ascent, six red-clump and one red horizontal branch star.
- ID:
- ivo://CDS.VizieR/J/MNRAS/463/580
- Title:
- Abundances of red giants in NGC6940
- Short Name:
- J/MNRAS/463/580
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the high-resolution (R~=60000), high signal-to-noise ratio (S/N~=120) spectroscopic analysis of 12 red giant members of the Galactic open cluster NGC 6940. We applied Yonsei-Yale isochrones to the colour-magnitude diagram, which suggested an age of 1.1Gyr for the cluster with a turn-off mass of 2 M_{sun}_. Atmospheric parameters (T_eff_, logg, [Fe/H], and {xi}_t_) were determined via equivalent widths of FeI, FeII, TiI, and TiII lines. Calculated mean metallicity of the cluster is <[Fe/H]>=0.04+/-0.02. We derived abundances of {alpha} (Mg, Si, Ca), Fe-group (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn), and n-capture (Y, La, Nd, Eu) elements to be about solar. Light odd-Z elements Na and Al are slightly enhanced in MMU 108 and MMU 152 by ~0.34 and ~0.16dex, respectively. Abundances of light elements Li, C, N, O, and ^12^C/^13^C ratios were derived from spectrum syntheses of the LiI resonance doublet at 6707{AA}, [OI] line at 6300{AA}, C_2_ Swan bandheads at 5164 and 5635{AA}, and strong ^12,13^CN system lines in the 7995-8040{AA} region. Most carbon isotopic ratios are similar to those found in other solar-metallicity giants, but MMU 152 has an unusual value of ^12^C/^13^C=6. Evaluation of the LiCNO abundances and ^12^C/^13^C ratios along with the present theoretical models suggests that all the red giants in our sample are core-helium-burning clump stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/431/3338
- Title:
- Abundances of red giants in open clusters
- Short Name:
- J/MNRAS/431/3338
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analysed high-resolution echelle spectra of red giant members for seven open clusters in the Galactic anticentre direction to explore their chemical compositions. Cluster membership has been confirmed by radial velocity. The spread in temperatures and gravities being very small among the red giants, nearly the same stellar lines were employed for all stars thereby reducing the abundance errors: the errors of the average abundance for a cluster were generally in the 0.02-0.05dex range. Our present sample covers Galactocentric distances of 8.3-11.3kpc and an age range of 0.2-4.3Gyr. A careful comparison of our results for the cluster NGC 2682 (M67) to other high-resolution abundance studies in the literature shows general good agreement for almost all elements in common.
- ID:
- ivo://CDS.VizieR/J/ApJ/854/184
- Title:
- Abundances of stars in 3 open clusters
- Short Name:
- J/ApJ/854/184
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Single stars in open clusters with known distances are important targets in constraining the nucleosynthesis process since their ages and luminosities are also known. In this work, we analyze a sample of 29 single red giants of the open clusters NGC2360, NGC3680, and NGC5822 using high-resolution spectroscopy. We obtained atmospheric parameters, abundances of the elements C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, and Nd, as well as radial and rotational velocities. We employed the local thermodynamic equilibrium atmospheric models of Kurucz and the spectral analysis code moog. Rotational velocities and light-element abundances were derived using spectral synthesis. Based on our analysis of the single red giants in these three open clusters, we could compare, for the first time, their abundance pattern with that of the binary stars of the same clusters previously studied. Our results show that the abundances of both single and binary stars of the open clusters NGC 2360, NGC 3680, and NGC 5822 do not have significant differences. For the elements created by the s-process, we observed that the open clusters NGC2360, NGC3680, and NGC5822 also follow the trend already raised in the literature that young clusters have higher s-process element abundances than older clusters. Finally, we observed that the three clusters of our sample exhibit a trend in the [Y/Mg]-age relation, which may indicate the ability of the [Y/Mg] ratio to be used as a clock for the giants.
- ID:
- ivo://CDS.VizieR/J/AJ/156/121
- Title:
- A catalog of 518 likely open cluster NGC 6405 members
- Short Name:
- J/AJ/156/121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents a combined method of Gaussian mixture model and random forest to compute membership probabilities of stars by using large, high-dimensional data sets. A significant advantage of this method is that it allows us to easily identify likely cluster members in large data sets starting from small training samples. As a benchmark, we select 40318 stars in the field of the open cluster NGC 6405 from the Gaia Data Release 2 (Gaia-DR2, Cat. I/345) by means of all five astrometric (positions, proper motions, and parallax) and photometric parameters. We use this combined method to determine likely cluster members in an eleven-dimensional parameter space. A total number of 518 high-probability (>=0.6) memberships are obtained, and the mean parallax and proper motion of the cluster are determined to be 2.171+/-0.005 mas (461+/-1 pc) and (<{mu}_{alpha}_cos{delta}>, <{mu}_{delta}_>)=(-1.357+/-0.023, -5.823+/-0.020) mas/yr, respectively. In addition, we quantitatively evaluate the relative importance of the parameters for membership determination and find that colors and magnitudes cannot be ignored in membership determination when using the RF method. Our results show that this combined method exhibits good performance in handling arbitrary high-dimensional and large data sets, such as Gaia-DR2, and it can also be used to investigate other open clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/710/597
- Title:
- Accretion in disks in Cep OB2
- Short Name:
- J/ApJ/710/597
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present accretion rates for a large number of solar-type stars in the Cep OB2 region, based on U-band observations. Our study comprises 95 members of the ~4Myr old cluster Tr 37 (including 20 "transition" objects (TOs)), as well as the only classical T Tauri star (CTTS) in the ~12Myr old cluster NGC 7160. The stars show different disk morphologies, with the majority of them having evolved and flattened disks. The typical accretion rates are about 1 order of magnitude lower than in regions aged 1-2Myr, and we find no strong correlation between disk morphology and accretion rates. Although half of the TOs are not accreting, the median accretion rates of normal CTTS and accreting "transition" disks are similar (~3x10^-9^ and 2x10^-9^M_{sun}_/yr, respectively). Comparison with other regions suggests that the TOs observed at different ages do not necessarily represent the same type of objects, which is consistent with the fact that the different processes that can lead to reduced IR excess/inner disk clearing (e.g., binarity, dust coagulation/settling, photoevaporation, giant planet formation) do not operate on the same timescales.
