- ID:
- ivo://CDS.VizieR/J/A+A/627/A117
- Title:
- Equivalent widths for six M67 stars
- Short Name:
- J/A+A/627/A117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The benchmark open cluster M67 is known to have solar metallicity and similar age as the Sun. It thus provides us a great opportunity to study the properties of solar twins, as well as the evolution of Sun-like stars. Previous spectroscopic studies claimed to detect possible subtle changes in stellar surface abundances throughout the stellar evolutionary phase, namely the effect of atomic diffusion, in M67. In this study we attempt to confirm and quantify the effect of atomic diffusion, as well as to explore the level of chemical (in)homogeneity in M67. We presented a strictly line-by-line differential chemical abundance analysis of two groups of stars in M67: three turn-off stars and three sub-giants. Stellar atmospheric parameters and elemental abundances were obtained with very high precision using the Keck/HIRES spectra. The sub-giants in our sample show negligible abundance variations (<=0.02dex), which implies that M67 was born chemically homogeneous. We note there is a significant abundance difference (~0.1-0.2dex) between sub-giants and turn-off stars, which can be interpreted as the signature of atomic diffusion. Qualitatively stellar models with diffusion agree with the observed abundance results. Some turn-off stars do not follow the general pattern, which suggests that in some cases diffusion can be inhibited. Our results thus pose a challenge for chemical tagging using the turn-off stars since they are likely not chemically homogeneous. Meanwhile, our results suggest that the effect of atomic diffusion could be as large as 0.1-0.2dex, and must be taken into account when using the current surface abundances of stars for chemical tagging.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/751/73
- Title:
- Equivalent widths in {eta} Cat in 1998-2012
- Short Name:
- J/ApJ/751/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar wind-emission features in the spectrum of eta Carinae have decreased by factors of 1.5-3 relative to the continuum within the last 10 years. We investigate a large data set from several instruments (STIS, GMOS, UVES) obtained between 1998 and 2011 and analyze the progression of spectral changes in direct view of the star, in the reflected polar-on spectra at FOS4, and at the Weigelt knots. We find that the spectral changes occurred gradually on a timescale of about 10 years and that they are dependent on the viewing angle. The line strengths declined most in our direct view of the star. About a decade ago, broad stellar wind-emission features were much stronger in our line-of-sight view of the star than at FOS4. After the 2009 event, the wind-emission line strengths are now very similar at both locations. High-excitation He I and N II absorption lines in direct view of the star strengthened gradually. The terminal velocity of Balmer P Cyg absorption lines now appears to be less latitude dependent, and the absorption strength may have weakened at FOS4. Latitude-dependent alterations in the mass-loss rate and the ionization structure of eta Carinae's wind are likely explanations for the observed spectral changes.
- ID:
- ivo://CDS.VizieR/J/A+A/588/A120
- Title:
- Equivalent widths in 10 open clusters
- Short Name:
- J/A+A/588/A120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Open clusters are distributed all across the disk and are convenient tracers of its properties. In particular, outer disk clusters bear a key role for the investigation of the chemical evolution of the Galactic disk. The goal of this study is to derive homogeneous elemental abundances for a sample of ten outer disk OCs, and investigate possible links with disk structures such as the Galactic Anticenter Stellar Structure. We analyse high-resolution spectra of red giants, obtained from the HIRES@Keck and UVES@VLT archives. We derive elemental abundances and stellar atmosphere parameters by means of the classical equivalent width method. We also performed orbit integrations using proper motions. The Fe abundances we derive trace a shallow negative radial metallicity gradient of slope -0.027+/-0.007dex/kpc in the outer 12kpc of the disk. The [alpha/Fe] gradient appears flat, with a slope of 0.006+/-0.007dex/kpc. The two outermost clusters (Be 29 and Sau 1) appear to follow elliptical orbits. Be 20 also exhibits a peculiar orbit with a large excursion above the plane. The irregular orbits of the three most metal-poor clusters (two of which are located at the edge of the Galactic disk), if confirmed by more robust astrometric measurements such as those of the Gaia mission, are compatible with an inside-out formation scenario for the Milky Way, in which extragalactic material is accreted onto the outer disk. We cannot determine if Be 20, Be 29, and Sau 1 are of extragalactic origin, as they may be old genuine Galactic clusters whose orbits were perturbed by accretion events or minor mergers in the past 5Gyr, or they may be representants of the thick disk population. The nature of these objects is intriguing and deserves further investigations in the near future.
- ID:
- ivo://CDS.VizieR/J/A+AS/42/391
- Title:
- Equivalent Widths in Pollux
- Short Name:
- J/A+AS/42/391
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/AZh/81/658
- Title:
- Equivalent widths of 9 barium stars
- Short Name:
- J/AZh/81/658
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our analysis of elemental abundances in the atmospheres of 16 classical barium stars derived from high-resolution spectra and model atmospheres. Comparison of the results with analogous data for moderate barium stars and normal red giants shows that the abundance patterns for elements before the iron peak are the same for all three groups of red giants, testifying to a similar origin. For binary systems, we confirm the influence of the orbital period and, hence, the component separation, on the overabundance of s-process elements. The amount of enrichment in s-process elements is also in influenced by mass, metallicity, and evolutionary phase. Any of these parameters can be important in individual objects.
- ID:
- ivo://CDS.VizieR/J/A+A/377/123
- Title:
- Equivalent widths of 6 binaries
- Short Name:
- J/A+A/377/123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed a careful differential abundance analysis of individual components of six main sequence binaries with separations of a few hundreds of AU. To reduce analysis concerns, we selected systems with almost equal mass components. We were able to derive differential abundances of several elements with errors down to 0.01dex in the best cases. We found that in four systems the two components have the same chemical composition, within these very severe limits. However, clear differences were found for the two remaining systems (HD 219542 and HD 200466), in both cases the primaries being more Fe-rich than the secondaries, by 0.091+/-0.009 and 0.053+/-0.024dex respectively. Similar differences were found for most of the elements considered in our analysis; however, we found no appreciable difference for volatile elements and a trend for increasing abundance differences with increasing condensation temperature for individual elements, a result similar to that found for some single stars with planets by Smith et al. (2001AJ....121.3207S). Finally, we note that HD 219542A has a Li-abundance comparable to those of Li-rich stars in old open clusters, while no Li is detected in the slightly cooler HD 219542B. We suggest that the primaries of these two systems have accreted rocky planets or the inner dust-rich part of a protoplanetary disk, likely due to gravitational perturbation caused by the presence of the companion.
- ID:
- ivo://CDS.VizieR/J/A+A/549/A129
- Title:
- Equivalent widths of cool stars
- Short Name:
- J/A+A/549/A129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The near-infrared (NIR) wavelength range offers some unique spectral features, and it is less prone to the extinction than the optical one. Recently, the first flux calibrated NIR library of cool stars from the NASA Infrared Telescope Facility (IRTF) have become available, and it has not been fully exploited yet. We want to develop spectroscopic diagnostics for stellar physical parameters based on features in the wavelength range 1-5um. In this work we test the technique in the I and K bands. The study of the Y, J, H, and L bands will be presented in the following paper. An objective method for semi-empirical definition of spectral features sensitive to various physical parameters is applied to the spectra. It is based on sensitivity map - i.e., derivative of the flux in the spectra with respect to the stellar parameters at a fixed wavelength. New optimized indices are defined and their equivalent widths (EWs) are measured.
- ID:
- ivo://CDS.VizieR/J/ApJ/850/194
- Title:
- Equivalent widths of 8 DIBs for 186 O & B stars
- Short Name:
- J/ApJ/850/194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the behavior of eight diffuse interstellar bands (DIBs) in different interstellar environments, as characterized by the fraction of hydrogen in molecular form (f_H2_), with comparisons to the corresponding behavior of various known atomic and molecular species. The equivalent widths of the five "normal" DIBs ({lambda}{lambda}5780.5, 5797.1, 6196.0, 6283.8, and 6613.6), normalized to E_B-V_, show a "lambda-shaped" behavior: they increase at low f_H2_, peak at f_H2_~0.3, and then decrease. The similarly normalized column densities of Ca, Ca+, Ti+, and CH+ also decline for f_H2_>0.3. In contrast, the normalized column densities of Na, K, CH, CN, and CO increase monotonically with fH2, and the trends exhibited by the three C_2_ DIBs ({lambda}{lambda}4726.8, 4963.9, and 4984.8) lie between those two general behaviors. These trends with f_H2_ are accompanied by cosmic scatter, the dispersion at any given f_H2_ being significantly larger than the individual errors of measurement. The lambda-shaped trends suggest the balance between creation and destruction of the DIB carriers differs dramatically between diffuse atomic and diffuse molecular clouds; additional processes aside from ionization and shielding are needed to explain those observed trends. Except for several special cases, the highest W{lambda}(5780)/W{lambda}(5797) ratios, characterizing the so-called "sigma-zeta effect," occur only at f_H2_<0.2. We propose a sequence of DIBs based on trends in their pair-wise strength ratios with increasing f_H2_. In order of increasing environmental density, we find the {lambda}6283.8 and {lambda}5780.5 DIBs, the {lambda}6196.0 DIB, the {lambda}6613.6 DIB, the {lambda}5797.1 DIB, and the C_2_ DIBs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/396/2061
- Title:
- Equivalent widths of EP UMA (HR 4330)
- Short Name:
- J/MNRAS/396/2061
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The chemically peculiar star HR 4330 (=HD 96707, EP UMa) was observed using the 2-m Himalayan Chandra Telescope at the Indian Astronomical Observatory, Hanle, India, for studying the variations in its spectral features. It was found that the spectral features of CaII 3933{AA} and SrII 4077{AA} were showing rapid variations in their equivalent widths with a periodicity of 0.28+/-0.02d. Such short-term variations suggest that there could be a dynamically active surface with rapid variation in the conditions of the stellar atmosphere.
- ID:
- ivo://CDS.VizieR/J/AJ/130/652
- Title:
- Equivalent widths of 4 giants in Be22 and Be66
- Short Name:
- J/AJ/130/652
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on high-resolution spectroscopy of four giant stars in the Galactic old open clusters Berkeley 22 and Berkeley 66 obtained with HIRES at the Keck telescope.
