- ID:
- ivo://CDS.VizieR/J/A+A/543/A160
- Title:
- Normalized spectra of 82 Kepler red giants
- Short Name:
- J/A+A/543/A160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate fundamental parameters of stars are essential for the asteroseismic analysis of data from the NASA Kepler mission. We aim at determining accurate atmospheric parameters and the abundance pattern for a sample of 82 red giants that are targets for the Kepler mission. We have used high-resolution, high signal-to-noise spectra from three different spectrographs. We used the iterative spectral synthesis method VWA to derive the fundamental parameters from carefully selected high-quality iron lines. After determination of the fundamental parameters, abundances of 13 elements were measured using equivalent widths of the spectral lines. Results: We identify discrepancies in logg and [Fe/H], compared to the parameters based on photometric indices in the Kepler Input Catalogue, Cat. V/133 (larger than 2.0dex for logg and [Fe/H] for individual stars). The Teff found from spectroscopy and photometry shows good agreement within the uncertainties. We find good agreement between the spectroscopic logg and the logg derived from asteroseismology. Also, we see indications of a potential metallicity effect on the stellar oscillations. We have determined the fundamental parameters and element abundances of 82 red giants. The large discrepancies between the spectroscopic logg and [Fe/H] and values in the Kepler Input Catalogue emphasize the need for further detailed spectroscopic follow-up of the Kepler targets in order to produce reliable results from the asteroseismic analysis.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/528/A121
- Title:
- Normalized spectra of 20 red giants
- Short Name:
- J/A+A/528/A121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate fundamental parameters of stars are mandatory for the asteroseismic investigation of the Kepler mission to succeed. We determine the atmospheric parameters for a sample of six well-studied bright K giants to confirm that our method produces reliable results. We then apply the same method to 14 K giants that are targets of the Kepler mission.
- ID:
- ivo://CDS.VizieR/J/BaltA/18/141
- Title:
- North America/Pelican red clump giants ugriJHK
- Short Name:
- J/BaltA/18/141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A possibility of applying 2MASS J, H, Ks, IPHAS r, i and Mega-Cam u, g photometry of red giants for determining distances to dark clouds is investigated. Red clump giants with a small admixture of G5-K1 and M2-M3 stars of the giant branch can be isolated and used in determining distances to separate clouds or spiral arms. Interstellar extinctions of background red giants can be also used for mapping dust surface density in the cloud.
- ID:
- ivo://CDS.VizieR/J/AcA/62/33
- Title:
- OGLE II detached red giant eclipsing binary twins
- Short Name:
- J/AcA/62/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify 34 highly-probable detached, red giant eclipsing binary pairs among 315 candidates in Devor's catalog of ~10000 OGLE-II eclipsing binaries. We estimate that there should be at least 200 such systems in OGLE-III. We show that spectroscopic measurements of the metallicities and radial-velocity-derived masses of these systems would independently constrain both the age-metallicity and helium-metallicity relations of the Galactic bulge, potentially breaking the age-helium degeneracy that currently limits our ability to characterize the bulge stellar population.
- ID:
- ivo://CDS.VizieR/J/ApJ/886/61
- Title:
- OGLE-III, MCPS and HST VI obs. of LMC & SMC
- Short Name:
- J/ApJ/886/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a calibration of the tip of the red giant branch (TRGB) in the Large Magellanic Cloud (LMC) on the Hubble Space Telescope (HST)/ACS F814W system. We use archival HST observations to derive blending corrections and photometric transformations for two ground-based wide-area imaging surveys of the Magellanic Clouds. We show that these surveys are biased bright by up to ~0.1mag in the optical due to blending, and that the bias is a function of local stellar density. We correct the LMC TRGB magnitudes from Jang & Lee (2017ApJ...835...28J) and use the geometric distance from Pietrzynski+ (2019Natur.567..200P) to obtain an absolute TRGB magnitude of M_F814W_=-3.97+/-0.046mag. Applying this calibration to the TRGB magnitudes from Freedman+ (2019ApJ...882...34F) in SN Ia hosts yields a value for the Hubble constant of H_0_=72.4+/-2.0km/s/Mpc for their TRGB+SNe Ia distance ladder. The difference in the TRGB calibration and the value of H_0_ derived here and by Freedman+ primarily results from their overestimate of the LMC extinction, caused by inconsistencies in their different sources of TRGB photometry for the Magellanic Clouds. Using the same source of photometry (OGLE) for both Clouds and applying the aforementioned corrections yields a value for the LMC I-band TRGB extinction that is lower by 0.06mag, consistent with independent OGLE reddening maps used by us and by Jang & Lee to calibrate TRGB and determine H0.
- ID:
- ivo://CDS.VizieR/J/A+A/394/975
- Title:
- OH 5-cm line survey in late-type stars
- Short Name:
- J/A+A/394/975
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have undertaken a comprehensive search for 5-cm excited OH maser emission from evolved stars representative of various stages of late stellar evolution. Observed sources were selected from known 18-cm OH sources. This survey was conducted with the 100-m Effelsberg telescope, at 6.0GHz in Sep 2000, to achieve high signal to noise ratio observations and a sensitivity limit of about 0.05 to 0.1Jy. A total of 65 stellar sources were searched for both main line and satellite line emission. We confirm the previous detection of 5 cm OH in Vy 2-2, do not confirm emission from NML-Cyg and do not report any other new detection within the above sensitivity limit. The number of observed sources is 67.
- ID:
- ivo://CDS.VizieR/J/AJ/123/2772
- Title:
- OH-selected AGB and post-AGB objects. I.
- Short Name:
- J/AJ/123/2772
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using 766 compact objects found in a systematic survey of the Galactic plane in the 1612MHz masing OH line, new light is cast on the IR properties of evolved stars on the thermally pulsing asymptotic giant branch (AGB) and beyond. The usual mid-IR selection criteria for post-AGB, based on IRAS colors, largely fail to distinguish early post-AGB stages. A two-color diagram from much narrower band MSX flux densities, with bimodal distributions, provides a better tool for doing this. Four mutually consistent selection criteria for OH-masing red protoplanetary nebulae are given, as well as two for early post-AGB masers and one for all post-AGB masers including the earliest ones. All these criteria miss a group of blue, high-outflow post-AGB sources with 60{mu}m excess; these will be discussed in detail in Paper II (Sevenster, 2002AJ....123.2772S). The majority of post-AGB sources show regular double-peaked spectra in the OH 1612MHz line, with fairly low outflow velocities, although the fractions of single peaks and irregular spectra may vary with age and mass. The OH flux density shows a fairly regular relation with the stellar flux and the envelope optical depth, with the maser efficiency increasing with IRAS color R_21_. The OH flux density is linearly correlated with the 60{mu}m flux density.
- ID:
- ivo://CDS.VizieR/J/A+A/390/235
- Title:
- OI and FeII equivalent widths in metal-poor stars
- Short Name:
- J/A+A/390/235
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The table gives equivalent widths (in m{AA}) of OI and FeII lines for 35 metal-poor main sequence and subgiant stars as measured from high resolution, high S/N spectra observed with the ESO VLT/UVES spectrograph, during three observing runs: April 8-12, 2000, July 22-24, 2000, and April 10-12, 2001.
- ID:
- ivo://CDS.VizieR/J/ApJ/722/1373
- Title:
- {omega} Centauri giants abundances
- Short Name:
- J/ApJ/722/1373
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present elemental abundances for 855 red giant branch (RGB) stars in the globular cluster Omega Centauri ({omega} Cen) from spectra obtained with the Blanco 4m telescope and Hydra multifiber spectrograph. The sample includes nearly all RGB stars brighter than V=13.5 and spans {omega} Cen's full metallicity range. The heavy {alpha} elements (Si, Ca, and Ti) are generally enhanced by +/-0.3 dex and exhibit a metallicity-dependent morphology that may be attributed to mass and metallicity-dependent Type II supernova (SN) yields. The heavy {alpha} and Fe-peak abundances suggest minimal contributions from Type Ia SNe. The light elements (O, Na, and Al) exhibit >0.5 dex abundance dispersions at all metallicities, and a majority of stars with [Fe/H]>-1.6 have [O/Fe], [Na/Fe], and [Al/Fe] abundances similar to those in monometallic globular clusters, as well as O-Na, O-Al anticorrelations and the Na-Al correlation in all but the most metal-rich stars. A combination of pollution from intermediate-mass asymptotic giant branch stars and in situ mixing may explain the light element abundance patterns. A large fraction (27%) of {omega} Cen stars are O-poor ([O/Fe]<0) and are preferentially located within 5'-10' of the cluster center. The O-poor giants are spatially similar, located in the same metallicity range, and are present in nearly equal proportions to blue main-sequence stars. This suggests that the O-poor giants and blue main-sequence stars may share a common origin. [La/Fe] increases sharply at [Fe/H]>~-1.6, and the [La/Eu] ratios indicate that the increase is due to almost pure s-process production.
- ID:
- ivo://CDS.VizieR/J/A+A/655/A23
- Title:
- Open cluster red clump stars Lithium abundances
- Short Name:
- J/A+A/655/A23
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- It has recently been suggested that all giant stars with masses below 2M_{sun}_ suffer an episode of surface lithium enrichment between the tip of the red giant branch (RGB) and the red clump (RC). We test if the above result can be confirmed in a sample of RC and RGB stars that are members of open clusters. We discuss Li abundances in six open clusters with ages between 1.5 and 4.9Gyr (turn-off masses between 1.1 and 1.7M_{sun}_). We compare these observations with the predictions of different models that include rotation-induced mixing, thermohaline instability, mixing induced by the first He flash, and energy losses by neutrino magnetic moment. In six clusters, we find close to 35% of RC stars have Li abundances that are similar or higher than those of upper RGB stars. This can be a sign of fresh Li production. Because of the extra-mixing episode connected to the luminosity bump, the expectation has been for RC stars to have systematically lower surface Li abundances. However, we cannot confirm that this possible Li production is ubiquitous. For about 65% of RC giants, we can only determine upper limits in abundances that could be hiding very low Li content. Our results indicate the possibility that Li is being produced in the RC, at levels that would not typically permit the classification of these the stars as Li rich. The determination of their carbon isotopic ratio would help to confirm that the RC giants have suffered extra mixing followed by subsequent Li enrichment. The Li abundances of the RC stars can be qualitatively explained by the models by using an additional mixing episode close to the He flash.
