- ID:
- ivo://CDS.VizieR/J/AJ/154/184
- Title:
- Multiplicity of RV exoplanet host stars
- Short Name:
- J/AJ/154/184
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Given the frequency of stellar multiplicity in the solar neighborhood, it is important to study the impacts this can have on exoplanet properties and orbital dynamics. There have been numerous imaging survey projects established to detect possible low-mass stellar companions to exoplanet host stars. Here, we provide the results from a systematic speckle imaging survey of known exoplanet host stars. In total, 71 stars were observed at 692 and 880 nm bands using the Differential Speckle Survey Instrument at the Gemini-north Observatory. Our results show that all but two of the stars included in this sample have no evidence of stellar companions with luminosities down to the detection and projected separation limits of our instrumentation. The mass-luminosity relationship is used to estimate the maximum mass a stellar companion can have without being detected. These results are used to discuss the potential for further radial velocity follow-up and interpretation of companion signals.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/749/77
- Title:
- MW halo. III. Statistical chemical abundances
- Short Name:
- J/ApJ/749/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We find that the relative contribution of satellite galaxies accreted at high redshift to the stellar population of the Milky Way's smooth halo increases with distance, becoming observable relative to the classical smooth halo about 15 kpc from the Galactic center. In particular, we determine line-of-sight-averaged [Fe/H] and [{alpha}/Fe] in the metal-poor main-sequence turnoff (MPMSTO) population along every Sloan Extension for Galactic Understanding and Exploration (SEGUE) spectroscopic line of sight. Restricting our sample to those lines of sight along which we do not detect elements of cold halo substructure (ECHOS), we compile the largest spectroscopic sample of stars in the smooth component of the halo ever observed in situ beyond 10 kpc. We find significant spatial autocorrelation in [Fe/H] in the MPMSTO population in the distant half of our sample beyond about 15 kpc from the Galactic center. Inside of 15 kpc however, we find no significant spatial autocorrelation in [Fe/H]. At the same time, we perform SEGUE-like observations of N-body simulations of Milky Way analog formation. While we find that halos formed entirely by accreted satellite galaxies provide a poor match to our observations of the halo within 15 kpc of the Galactic center, we do observe spatial autocorrelation in [Fe/H] in the simulations at larger distances. This observation is an example of statistical chemical tagging and indicates that spatial autocorrelation in metallicity is a generic feature of stellar halos formed from accreted satellite galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/589/A115
- Title:
- Na and Al abundances of 1303 stars
- Short Name:
- J/A+A/589/A115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar evolution models predict that internal mixing should cause some sodium overabundance at the surface of red giants more massive than ~1.5-2.0M_{aun}_. The surface aluminium abundance should not be affected. Nevertheless, observational results disagree about the presence and/or the degree of Na and Al overabundances. In addition, Galactic chemical evolution models adopting different stellar yields lead to very different predictions for the behavior of [Na/Fe] and [Al/Fe] versus [Fe/H]. Overall, the observed trends of these abundances with metallicity are not well reproduced. We re-address both issues, using new Na and Al abundances determined within the Gaia-ESO Survey. Our aim is to obtain better observational constraints on the behavior of these elements using two samples: i) more than 600 dwarfs of the solar neighborhood and of open clusters and ii) low- and intermediate-mass clump giants in six open clusters. Abundances were determined using high-resolution UVES spectra. The individual Na abundances were corrected for nonlocal thermodynamic equilibrium effects. For the Al abundances, the order of magnitude of the corrections was estimated for a few representative cases. For giants, the abundance trends with stellar mass are compared to stellar evolution models. For dwarfs, the abundance trends with metallicity and age are compared to detailed chemical evolution models.
- ID:
- ivo://CDS.VizieR/J/A+A/510/A54
- Title:
- NaI and CaII interstellar absorption
- Short Name:
- J/A+A/510/A54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new high resolution (R>50000) absorption measurements of the NaI doublet (5889-5895{AA}) along 482 nearby sight-lines, in addition to 807 new measurements of the CaII K (3933{AA}) absorption line. We have combined these new data with previously reported measurements to produce a catalog of absorptions towards a total of 1857 early-type stars located within 800pc of the Sun. Using these data we have determined the approximate 3-dimensional spatial distribution of neutral and partly ionized interstellar gas density within a distance-cube of 300pc from the Sun.
1195. NaI in Local Bubble
- ID:
- ivo://CDS.VizieR/J/A+A/346/785
- Title:
- NaI in Local Bubble
- Short Name:
- J/A+A/346/785
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present preliminary results form a long-term program of mapping the neutral absorption characteristics of the local interstellar medium, taking advantage of Hipparcos stellar distances. Equivalent width of the NaI D-line doublet at 5890{AA} are presented for the lines-of-sight towards some 143 new target stars lying within 300pc of the Sun.
- ID:
- ivo://CDS.VizieR/III/25A
- Title:
- Na, Mg, Ca abundances in K-type giants
- Short Name:
- III/25A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Narrow-band photometric measures of the strengths of the Mg b, Ca triplet, and Na D lines on 312 G and K type giant stars have been analysed with a model atmosphere technique to determine abundances of Mg, Ca and Na.
- ID:
- ivo://CDS.VizieR/J/A+A/517/A81
- Title:
- 2nd and 3d parameters of HB of globular clusters
- Short Name:
- J/A+A/517/A81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The second parameter (the first being metallicity) defining the distribution of stars on the horizontal branch (HB) of globular clusters (GCs) has long been one of the major open issues in our understanding of the evolution of normal stars. Large photometric and spectroscopic databases are now available: they include large and homogeneous sets of colour-magnitude diagrams, cluster ages, and homogeneous data about chemical compositions from our FLAMES survey. We use these databases to re-examine this issue. Methods. We use the photometric data to derive median and extreme (i.e., the values including 90% of the distribution) colours and magnitudes of stars along the HB for about a hundred GCs. We transform these into median and extreme masses of stars on the HB, using the models developed by the Pisa group, and taking into account evolutionary effects. We compare these masses with those expected at the tip of the red giant branch (RGB) to derive the total mass lost by the stars.
- ID:
- ivo://CDS.VizieR/J/A+A/539/A143
- Title:
- Nearby B-stars stellar parameters and abundances
- Short Name:
- J/A+A/539/A143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Early B-type stars are ideal indicators for present-day cosmic abundances since they preserve their pristine abundances and typically do not migrate far beyond their birth environments over their short lifetimes, in contrast to older stars like the Sun. They are also unaffected by depletion onto dust grains, unlike the cold/warm interstellar medium (ISM) or HII regions. A carefully selected sample of early B-type stars in OB associations and the field within the solar neighbourhood is studied comprehensively. Quantitative spectroscopy is used to characterise their atmospheric properties in a self-consistent way. Present-day abundances for the astrophysically most interesting chemical elements are derived in order to investigate whether a present-day cosmic abundance standard can be established.
- ID:
- ivo://CDS.VizieR/J/A+A/487/307
- Title:
- Nearby B-type stars abundances
- Short Name:
- J/A+A/487/307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The recent downward revision of the solar photospheric abundances now leads to severe inconsistencies between the theoretical predictions for the internal structure of the Sun and the results of helioseismology. There have been claims that the solar neon abundance may be underestimated and that an increase in this poorly-known quantity could alleviate (or even completely solve) this problem. Early-type stars in the solar neighbourhood are well-suited to testing this hypothesis because they are the only stellar objects whose absolute neon abundance can be derived from the direct analysis of photospheric lines. Here we present a fully homogeneous NLTE abundance study of the optical Ne I and Ne II lines in a sample of 18 nearby, early B-type stars, which suggests log[epsilon(Ne)]=7.97+/-0.07dex (on the scale in which log[epsilon(H)=12)]) for the present-day neon abundance of the local ISM. Chemical evolution models of the Galaxy only predict a very small enrichment of the nearby interstellar gas in neon over the past 4.6Gyr, implying that our estimate should be representative of the Sun at birth. Although higher by about 35% than the new recommended solar abundance, such a value appears insufficient by itself to restore the past agreement between the solar models and the helioseismological constraints.
- ID:
- ivo://CDS.VizieR/J/A+A/463/455
- Title:
- Nearby early-type gal. with ionized gas. III.
- Short Name:
- J/A+A/463/455
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper is devoted to the study of the underlying stellar population of a sample of 62 nearby early-type galaxies, predominantly located in low density environments, a large fraction of which showing emission lines. Ages, metallicities and [{alpha}/Fe] ratios have been derived through the comparison of Lick indices measured at different galacto-centric distances (7 apertures and 4 gradients) with new Simple Stellar Population (SSP) models which account for the presence of alpha/Fe-enhancement. The SSPs cover a wide range of ages (10^8^-16x10^9^yr), metallicities (0.0004<=Z<=0.05) and [{alpha}/Fe] ratios (0-0.8). To derive the stellar population parameters we use an algorithm that provides, together with the most likely solution in the (age, Z, [{alpha}/Fe]) space, also the probability density function along the age-metallicity degeneracy. We derive a large spread in age, with SSP-equivalent ages ranging from a few to 15Gyrs. Age does not show any significant trend with central velocity dispersion sigma_c_ but E galaxies appear on average older than lenticulars.
