- ID:
- ivo://CDS.VizieR/J/MNRAS/455/199
- Title:
- CaII triplet in red giant spectra
- Short Name:
- J/MNRAS/455/199
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Measurements are presented and analysed of the strength of the CaII triplet lines in red giants in Galactic globular and open clusters, and in a sample of red giants in the LMC disc that have significantly different [Ca/Fe] abundance ratios to the Galactic objects. The Galactic objects are used to generate a calibration between CaII triplet line strength and [Fe/H], which is then used to estimate [Fe/H]CaT for the LMC stars. The values are then compared with the [Fe/H]spec determinations from high-dispersion spectroscopy. After allowance for a small systematic offset, the two abundance determinations are in excellent agreement. Further, as found in earlier studies, the difference is only a very weak function of the [Ca/Fe] ratio. For example, changing [Ca/Fe] from +0.3 to -0.2 causes the CaII-based abundance to underestimate [Fe/H]spec by only ~0.15dex, assuming a Galactic calibration. Consequently, the CaII triplet approach to metallicity determinations can be used without significant bias to study stellar systems that have substantially different chemical evolution histories.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/411/1013
- Title:
- CaII triplet in Sextans dSph galaxy
- Short Name:
- J/MNRAS/411/1013
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use Very Large Telescope (VLT)/Fibre Large Array Multi Element Spectrograph (FLAMES) intermediate-resolution (R~6500) spectra of individual red giant branch stars in the near-infrared Ca ii triplet (CaT) region to investigate the wide-area metallicity properties and internal kinematics of the Sextans dwarf spheroidal galaxy (dSph). Our final sample consists of 174 probable members of Sextans with accurate line-of-sight velocities (+/-2km/s) and CaT [Fe/H] measurements (+/-0.2dex).
- ID:
- ivo://CDS.VizieR/J/A+AS/124/359
- Title:
- Ca II triplet lines in cool stars
- Short Name:
- J/A+AS/124/359
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD spectra of the infrared triplet lines of ionized calcium at {lambda}{lambda}8498, 8542, 8662 have been obtained at a spectral resolution of 0.4{AA} in 146 stars brighter than V=+7.0 spanning a range in spectral types from F7 to M4 of all luminosity classes and a range in metallicity [Fe/H] from -3.0 to +1.1. These have been analysed to investigate the dependence of the Ca II triplet strengths on stellar parameters like luminosity, temperature and metallicity. A detailed study reveals a strong dependence on luminosity, much stronger for metal rich stars than for the metal poor ones and a milder dependence on metallicity, although much more conspicuous in supergiants than in dwarfs. All these correlations are found to be non-linear over the parameter space covered. The present study also shows chromospheric activity to be an important phenomenon affecting the strength and the shape of the line profiles. Stars of similar luminosity and metallicity have varying Ca II line depths owing to varying chromospheric emission filling in their Ca II absorption. The Ca II triplet strength is thus observed to be a triparametric discriminant in cool stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/383/183
- Title:
- CaII triplet of RGB from VLT/FLAMES obs.
- Short Name:
- J/MNRAS/383/183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We demonstrate that low-resolution CaII triplet (CaT) spectroscopic estimates of the overall metallicity ([Fe/H]) of individual red giant branch (RGB) stars in two nearby dwarf spheroidal galaxies (dSphs) agree to +/-0.1-0.2dex with detailed high-resolution spectroscopic determinations for the same stars over the range -2.5<[Fe/H]<-0.5. For this study, we used a sample of 129 stars observed in low- and high-resolution modes with VLT/FLAMES in the Sculptor and Fornax dSphs. We also present the data-reduction steps we used in our low-resolution analysis and show that the typical accuracy of our velocity and CaT [Fe/H] measurement is ~2km/s and 0.1dex, respectively. We conclude that CaT[Fe/H] relations calibrated on globular clusters can be applied with confidence to RGB stars in composite stellar populations over the range -2.5<[Fe/H]<-0.5.
- ID:
- ivo://CDS.VizieR/J/AJ/130/2666
- Title:
- Ca4227 indices in early-type galaxies
- Short Name:
- J/AJ/130/2666
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have investigated the abundance of calcium in early-type galaxies by measuring the strength of the CaI {lambda}4227 absorption line in their integrated spectra. The database used is the large sample of early-type galaxy integrated spectra in Caldwell and coworkers (2003AJ....125.2891C). We have measured Ca abundances from the CaI {lambda}4227 feature both by using the Lick Ca4227 index and by defining a new index, Ca4227_r_, that avoids the CN4216 molecular band in the continuum on the blueward side of the line.
- ID:
- ivo://CDS.VizieR/J/A+A/542/A83
- Title:
- CAIXA. II. AGNs from excess variance analysis
- Short Name:
- J/A+A/542/A83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the results of the first XMM-Newton systematic "excess variance" study of all the radio quiet, X-ray unobscured AGN. The entire sample consist of 161 sources observed by XMM-Newton for more than 10ks in pointed observations, which is the largest sample used so far to study AGN X-ray variability on time scales less than a day. Recently it has been suggested that the same engine might be at work in the core of every Black Hole (BH) accreting object. In this hypothesis, the same variability should be observed in all AGN, once rescaled by the MBH (MBH) and accretion rate (dm/dt). We systematically compute the excess variance for all AGN, on different time-scales (10, 20, 40 and 80ks) and in different energy bands (0.3-0.7, 0.7-2 and 2-10keV).
- ID:
- ivo://CDS.VizieR/J/ApJS/133/119
- Title:
- Calan-ESO proper-motion catalog
- Short Name:
- J/ApJS/133/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Calan-ESO Proper-Motion Catalog (CE Catalog) contains 542 stars with proper motions >=0.2"/yr, identified in 14 ESO areas in the southern hemisphere. Proper motions were measured from red IIIa-F plates taken 6-16yr apart. Comparing the CE catalog with the Luyten and the Luyten half-second catalogs, we find that both suffer from incompleteness, which is particularly serious (<~40% complete) for m_R_>~13, where many of the astrophysically interesting object can be found. Proper motions, coordinates, estimated magnitudes, and finding charts for all objects in the catalog are provided
- ID:
- ivo://nasa.heasarc/cyder
- Title:
- Calan-Yale Deep Extragalactic Research Survey X-Ray Source Catalog
- Short Name:
- CYDER
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The main goal of the Calan-Yale Deep Extragalactic Research (CYDER) Survey X-ray survey is to study serendipitous X-ray sources detected by Chandra in an intermediate flux range (10<sup>-15</sup> to 10<sup>-12</sup> ergs/s) that comprises most of the X-ray background. A total of 267 X-ray sources spread over five archived fields were detected. The log N - log S distribution obtained for this sample is consistent with the results of other surveys. Deep V and I images were taken of these fields in order to calculate X-ray-to-optical flux ratios. Identifications and redshifts were obtained for 106 sources using optical spectroscopy from 8 m class telescopes to reach the optically faintest sources, to the same level as deeper X-ray fields like the Chandra Deep Fields, showing that the nature of sources detected depends mostly on the optical limit for spectroscopy. This table was created by the HEASARC in March 2007 based on the CDS table J/ApJ/621/104, file table4.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://CDS.VizieR/J/ApJ/712/L21
- Title:
- Calcium abundances in 17 globular clusters
- Short Name:
- J/ApJ/712/L21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use abundances of Ca, O, Na, and Al from high-resolution UVES spectra of 200 red giants in 17 globular clusters (GCs) to investigate the correlation found by Lee et al. (2009Icar..199..413C) between chemical enrichment from SNII and star-to-star variations in light elements in GC stars. We find that (1) the [Ca/H] variations between first and second generation stars are tiny in most GCs (~0.02-0.03dex, comparable with typical observational errors). In addition, (2) using a large sample of red giants in M4 (NGC 6121) with abundances from UVES spectra from Marino et al. (2008, Cat. J/A+A/490/625), we find that Ca and Fe abundances in the two populations of Na-poor and Na-rich stars are identical.
- ID:
- ivo://CDS.VizieR/J/AJ/135/836
- Title:
- Calcium triplet index in LMC stars
- Short Name:
- J/AJ/135/836
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Infrared CaII triplet (CaT) spectroscopy has been used to derive stellar metallicities for individual stars in four Large Magellanic Cloud fields situated at galactocentric distances of 3{deg}, 5{deg}, 6{deg}, and 8{deg} to the north of the bar. The combination of spectroscopy with deep CCD photometry has allowed us to break the RGB age-metallicity degeneracy and compute the ages for the objects observed spectroscopically. The obtained age-metallicity relationships (AMRs) for our four fields are statistically indistinguishable. We conclude that the lower mean metallicity in the outermost field is a consequence of it having a lower fraction of intermediate-age stars, which are more metal-rich than the older stars. The disk AMR is similar to that for clusters. However, the lack of objects with ages between 3 and 10Gyr is not observed in the field population. Finally, we used data from the literature to derive consistently the AMR of the bar. Simple chemical evolution models have been used to reproduce the observed AMRs with the purpose of investigating which mechanism has participated in the evolution of the disk and bar.
