- ID:
- ivo://CDS.VizieR/J/A+A/449/723
- Title:
- Abundances in atmospheres of stars with planets
- Short Name:
- J/A+A/449/723
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a uniform and homogeneous study of the abundances of Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Na, Mg and Al in 100 stars with and 94 without known planetary companions. The main purpose of this work is to make a deep investigation of the abundance of refractory elements, using an enlarged set of data which includes new observations, especially for the sample of stars without known planets. The new comparison sample spans metallicity range -0.70<[Fe/H]<0.50 and fills the gap that previously existed, mainly at high metallicities, in the number of field "single" comparison stars. Furthermore, we improved the line list previously studied by other authors: on average we analysed 90 spectral lines in every spectrum and carefully measured more than 16 600 equivalent widths (EW) to calculate the abundances. We investigate possible differences between the chemical abundances of the two groups of stars, with and without planets. The results are globally comparable to those obtained by other authors, and in most cases the abundance trends of planet-host stars are very similar to those of the comparison sample. This work represents a step towards the comprehension of recently discovered planetary systems. These results could also be useful for verifying galactic models at high metallicities and consequently improve our knowledge of stellar nucleosynthesis and galactic chemical evolution.
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- ID:
- ivo://CDS.VizieR/J/A+A/525/A63
- Title:
- Abundances in Ba stars
- Short Name:
- J/A+A/525/A63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present abundances of Mn, Cu, Zn, and various light and heavy elements for a sample of barium and normal giant stars, and present correlations between abundances contributed to different degrees by the weak-s, main-s, and r-processes of neutron capture, between Fe-peak elements and heavy elements. All spectra for the sample stars were obtained with the 1.52m telescope at ESO, La Silla, using the Fiber Fed Extended Range Optical Spectrograph (FEROS). FEROS spectra have a constant resolving power of R=48000 from 3600{AA} to 9200{AA}. The stellar sample targeted in our study includes eight mild and classical barium stars and six normal giants, with a spectral S/N ratio ranging from 200 to 450 in the visible range.
- ID:
- ivo://CDS.VizieR/J/A+A/580/A24
- Title:
- Abundances in dwarfs, subgiants, and giants
- Short Name:
- J/A+A/580/A24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analyzed high-resolution and high signal-to-noise ratio optical spectra of nearby FGK stars with and without detected giant planets in order to homogeneously measure their photospheric parameters, mass, age, and the abundances of volatile (C, N, and O) and refractory (Na, Mg, Si, Ca, Ti, V, Mn, Fe, Ni, Cu, and Ba) elements. Our sample contains 309 stars from the solar neighborhood (up to the distance of 100pc), out of which 140 are dwarfs, 29 are subgiants, and 140 are giants. The photospheric parameters are derived from the equivalent widths (EWs) of FeI and FeII lines. Masses and ages come from the interpolation in evolutionary tracks and isochrones on the HR diagram. The abundance determination is based on the equivalent widths of selected atomic lines of the refractory elements and on the spectral synthesis of C_2_, CN, CI, OI, and NaI features. We apply a set of statistical methods to analyze the abundances derived for the three subsamples. Our results show that: i) giant stars systematically exhibit underabundance in [C/Fe] and overabundance in [N/Fe] and [Na/Fe] in comparison with dwarfs, a result that is normally attributed to evolution-induced mixing processes in the envelope of evolved stars; ii) for solar analogs only, the abundance trends with the condensation temperature of the elements are correlated with age and anticorrelated with the surface gravity, which is in agreement with recent studies; iii) as in the case of [Fe/H], dwarf stars with giant planets are systematically enriched in [X/H] for all the analyzed elements, except for O and Ba (the former due to limitations of statistics), confirming previous findings in the literature that not only iron has an important relation with the planetary formation; and iv) giant planet hosts are also significantly overabundant for the same metallicity when the elements from Mg to Cu are combined together.
- ID:
- ivo://CDS.VizieR/J/ApJ/662/15
- Title:
- Abundances in extragalactic HII regions
- Short Name:
- J/ApJ/662/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We determine the primordial helium mass fraction Yp using 93 spectra of 86 low-metallicity extragalactic HII regions. This sample constitutes the largest and most homogeneous high-quality data set in existence for the determination of Yp. For comparison, and to improve the statistics in our investigation of systematic effects affecting the Yp determination, we have also considered a sample of 271 low-metallicity HII regions selected from Data Release 5 of the Sloan Digital Sky Survey. Although this larger sample shows more scatter, it gives results that are consistent at the 2{sigma} level with our original sample. We have considered known systematic effects that may affect the ^4^He abundance determination.
- ID:
- ivo://CDS.VizieR/J/AZh/93/49
- Title:
- Abundances in Galactic open clusters
- Short Name:
- J/AZh/93/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalog compiling the parameters of 346 open clusters, including their metallicities, positions, ages, and velocities has been composed. The elements of the Galactic orbits for 272 of the clusters have been calculated. Spectroscopic determinations of the relative abundances, [el/Fe], for 14 elements synthesized in various nuclear processes averaged over data from 109 publications are presented for 90 clusters. The compiled data indicate that the relative abundances of primary {alpha} elements (oxygen and magnesium) exhibit different dependences on metallicity, age, Galactocentric distance, and the elements of the Galactic orbits in clusters with high, elongated orbits satisfying the criterion (Z_max_^2^+4e^2^)^1/2^>0.40 and in field stars of the Galactic thin disk (Zmax is the maximum distance of the orbit from the Galactic plane in kiloparsec and e is the eccentricity of the Galactic orbit). Since no systematic effects distorting the relative abundances of the studied elements in these clusters have been found, these difference suggest real differences between clusters with high, elongated orbits and field stars. In particular, this supports the earlier conclusion, based on an analysis of the elements of the Galactic orbits, that some clusters formed as a result of interactions between high-velocity,metal-poor clouds and the interstellar medium of the Galactic thin disk. On average, clusters with high, elongated orbits and metallicities [Fe/H]<-0.1 display lower relative abundances of the primary {alpha} elements than do field stars. The low [O, Mg/Fe] ratios of these clusters can be understood if the high-velocity clouds that gave rise to them were formed of interstellar material from regions where the star-formation rate and/or the masses of Type II supernovae were lower than near the Galactic plane. It is also shown that, on average, the relative abundances of the primary {alpha} elements are higher in relatively metal-rich clusters with high, elongated orbits than in field stars. This can be understood if clusters with [Fe/H]>-0.1 formed as a result of interactions between metal-rich clouds with intermediate velocities and the interstellar medium of the Galactic disk; such clouds could form from returning gas in a so-called "Galactic fountain".
- ID:
- ivo://CDS.VizieR/J/A+A/506/729
- Title:
- Abundances in globular cluster Pal 3
- Short Name:
- J/A+A/506/729
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Chemical abundances of 25 alpha-, iron peak-, and neutron-capture elements in the remote (R=90kpc) outer halo globular cluster have been determined for 4 red giants observed with the Magellan/MIKE spectrograph and from integrated spectra of 19 stars obtained with the Keck/HIRES instrument. The resulting abundance ratios show that Pal 3 is very similar to globular clusters of the inner halo and very dissimilar from dwarf spheroidal galaxy stars. Its neutron capture element ratios are compatible with a pure r-process enrichment.
- ID:
- ivo://CDS.VizieR/J/ApJ/736/87
- Title:
- Abundances in G-type stars with exoplanets
- Short Name:
- J/ApJ/736/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We confirm the difference in chemical abundance between stars with and without exoplanets and present the relation between chemical abundances and physical properties of exoplanets, such as planetary mass and the semimajor axis of planetary orbit. We obtained the spectra of 52 G-type stars from the Bohyunsan Optical Astronomy Observatory (BOAO) Echelle Spectrograph and carried out abundance analyses for 12 elements: Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, and Ni. We first found that the [Mn/Fe] ratios of planet-host stars are higher than those of comparison stars over the entire metallicity range, and we then found that in metal-poor stars of [Fe/H]<-0.4 the abundance difference was larger than in metal-rich samples, especially for the elements of Mg, Al, Sc, Ti, V, and Co. After examining the relation between planet properties and metallicities of planet-host stars, we observed that planet-host stars with low metallicities tend to have several low-mass planets (<M_J_) instead of a massive gas-giant planet.
- ID:
- ivo://CDS.VizieR/J/MNRAS/424/2316
- Title:
- Abundances in HII regions
- Short Name:
- J/MNRAS/424/2316
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We suggest a new way of determining abundances and electron temperatures in HII regions from strong emission lines. Our approach is based on the standard assumption that HII regions with similar intensities of strong emission lines have similar physical properties and abundances. A 'counterpart' for a studied HII region may be chosen among HII regions with well-measured abundances (reference HII regions) by comparison of carefully chosen combinations of strong-line intensities. Then the abundances in the investigated HII region can be assumed to be the same as those in its counterpart. In other words, we suggest to determine the abundances in HII regions 'by precedent'. To get more reliable abundances for the considered HII region, a number of reference HII regions are selected and then the abundances in the target HII region are estimated through extrapolation/interpolation. We will refer to this method of abundance determination as the counterpart method or, for brevity, the C method. We define a sample of reference HII regions and verify the validity of the C method. We find that this method produces reliable abundances. Finally, the C method is used to obtain the radial abundance distributions in the extended discs of the spiral galaxies M83, NGC 4625 and NGC 628.
- ID:
- ivo://CDS.VizieR/J/A+A/464/885
- Title:
- Abundances in 53 HII regions
- Short Name:
- J/A+A/464/885
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Continuing the systematic determination of the electron temperature of HII regions using the Balmer and/or Paschen discontinuities by Guseva et al. (2006ApJ...644..890G) we focus here on 3.6m ESO telescope observations of a large new sample of 69 HII regions in 45 blue compact dwarf (BCD) galaxies. This data set spans a wide range in metallicity (Z_{sun}_/60<Z<Z_{sun}_/3) and, combined with the sample of 47 HII regions from Guseva et al. (2006ApJ...644..890G), yields the largest spectroscopic data set ever used to derive the electron temperature in the H^+^ zone. In the same way as in Guseva et al. (2006ApJ...644..890G) we have used a Monte Carlo technique to vary free parameters and to calculate a series of model spectral energy distributions (SEDs) for each HII region. The electron temperature in the H^+^ zones was derived from the best fitting synthetic and observed SEDs in the wavelength range ~3200-5100{AA}, which includes the Balmer jump. On the base of the present large spectroscopic sample we find that in hot (Te(H^+^)>11000K) HII regions the temperature of the O^2+^ zone, determined from doubly ionised oxygen forbidden lines, does not differ statistically from the temperature of the H^+^ zone. Thus, we confirm and strengthen the finding by Guseva et al. (2006ApJ...644..890G). We emphasize that due to a number of modelling assumptions and the observational uncertainties for individual objects, only a large, homogeneous sample, as the one used here, can enable a conclusive study of the relation between Te(H^+^) and Te(OIII).
- ID:
- ivo://CDS.VizieR/J/A+A/521/A3
- Title:
- Abundances in HII regions and PNe of M81
- Short Name:
- J/A+A/521/A3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- M81 is an ideal laboratory to investigate the galactic chemical and dynamical evolution through the study of its young and old stellar populations. We analyze the chemical abundances of planetary nebulae and HII regions in the M81 disk for insight on galactic evolution, and compare it with that of other galaxies, including the Milky Way.