- 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.
« Previous |
1 - 10 of 84
|
Next »
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/368/247
- Title:
- Abundances of 6 suspected CP stars
- Short Name:
- J/MNRAS/368/247
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The abundance pattern of six stars classified as suspected chemically peculiar in the General Catalogue of Ap and Am stars (<III/162>) by Renson has been derived to ascertain the real nature of these objects. Spectroscopic observations in the range {lambda}{lambda}4800-5600{AA} have been carried out at the stellar station of the INAF Catania Astrophysical Observatory. Among the studied stars, for only three of them we confirmed their peculiarity, HD 155102 being a silicon star, HD 159082 a mercury-manganese star and HD 162132 a moderate metallic A-type star. The other three objects have chemical abundances not so different from the standard values derived in the literature for A-type stars and, furthermore, they do not show light variability. Hence, we suggest that they could be ruled out from Renson's catalogue.
- ID:
- ivo://CDS.VizieR/J/A+A/656/A125
- Title:
- ACV variables in the Zwicky Transient Facility
- Short Name:
- J/A+A/656/A125
- Date:
- 16 Mar 2022 00:55:18
- Publisher:
- CDS
- Description:
- The present work presents a case study of known variables from the Zwicky Transient Facility (ZTF) survey, with the aim of investigating the survey's suitability for the detection and study of new ACV variables. Using suitable selection criteria based on the known characteristics of ACV variables, candidate ACV stars were selected from the ZTF Catalog of Periodic Variable Stars. All light curves were inspected in detail to select the most promising candidates. Where available, low-resolution spectra from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) were employed to classify the stars on the MK system and confirm their status as mCP stars. We have identified 86 new promising ACV star candidates. 15 of these stars have LAMOST spectra available, which, in all cases, confirm them as classical mCP stars, which highlights the viability of our approach. We present astrophysical parameters for all sample stars, which can be sorted into four subgroups characterized by distinct light curve shapes. Anti-phase variations in different photometric passbands, in particular, is a unique characteristic of a subset of ACV stars readily usable for their identification. The availability of data in three different passbands (g, r, and i) is a major advantage of the ZTF survey. On the basis of our experience with other photometric surveys and the analysis of light curves, we conclude that the ZTF is well suited for the search for, and the analysis of, ACV variables, which, however, are not considered in the available ZTF variable star catalogues. Further work will be concerned with the development and refinement of a search algorithm to correctly identify these stars in ZTF data and, subsequently, in massive photometric time-series databases in general.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/501
- Title:
- APOGEE N-rich stars in inner Galaxy
- Short Name:
- J/MNRAS/465/501
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Formation of globular clusters (GCs), the Galactic bulge, or galaxy bulges in general is an important unsolved problem in Galactic astronomy. Homogeneous infrared observations of large samples of stars belonging to GCs and the Galactic bulge field are one of the best ways to study these problems. We report the discovery by APOGEE (Apache Point Observatory Galactic Evolution Experiment) of a population of field stars in the inner Galaxy with abundances of N, C, and Al that are typically found in GC stars. The newly discovered stars have high [N/Fe], which is correlated with [Al/Fe] and anticorrelated with [C/Fe]. They are homogeneously distributed across, and kinematically indistinguishable from, other field stars within the same volume. Their metallicity distribution is seemingly unimodal, peaking at [Fe/H]~-1, thus being in disagreement with that of the Galactic GC system. Our results can be understood in terms of different scenarios. N-rich stars could be former members of dissolved GCs, in which case the mass in destroyed GCs exceeds that of the surviving GC system by a factor of ~8. In that scenario, the total mass contained in so-called 'first-generation' stars cannot be larger than that in 'second-generation' stars by more than a factor of ~9 and was certainly smaller. Conversely, our results may imply the absence of a mandatory genetic link between 'second-generation' stars and GCs. Last, but not least, N-rich stars could be the oldest stars in the Galaxy, the by-products of chemical enrichment by the first stellar generations formed in the heart of the Galaxy.
- ID:
- ivo://CDS.VizieR/J/MNRAS/459/4299
- Title:
- Barium stars abundances and kinematics
- Short Name:
- J/MNRAS/459/4299
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present an homogeneous analysis of photospheric abundances based on high-resolution spectroscopy of a sample of 182 barium stars and candidates. We determined atmospheric parameters, spectroscopic distances, stellar masses, ages, luminosities and scaleheight, radial velocities, abundances of the Na, Al, {alpha}-elements, iron-peak elements, and s-process elements Y, Zr, La, Ce, and Nd. We employed the local thermodynamic equilibrium model atmospheres of Kurucz and the spectral analysis code MOOG. We found that the metallicities, the temperatures and the surface gravities for barium stars cannot be represented by a single Gaussian distribution. The abundances of {alpha}-elements and iron peak elements are similar to those of field giants with the same metallicity. Sodium presents some degree of enrichment in more evolved stars that could be attributed to the NeNa cycle. As expected, the barium stars show overabundance of the elements created by the s-process. By measuring the mean heavy-element abundance pattern as given by the ratio [s/Fe], we found that the barium stars present several degrees of enrichment. We also obtained the [hs/ls] ratio by measuring the photospheric abundances of the Ba-peak and the Zr-peak elements. Our results indicated that the [s/Fe] and the [hs/ls] ratios are strongly anticorrelated with the metallicity. Our kinematical analysis showed that 90 per cent of the barium stars belong to the thin disc population. Based on their luminosities, none of the barium stars are luminous enough to be an asymptotic giant branch star, nor to become self-enriched in the s-process elements. Finally, we determined that the barium stars also follow an age-metallicity relation.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A67
- Title:
- Blue and yellow straggler stars in open clusters
- Short Name:
- J/A+A/650/A67
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Blue straggler stars are exotic objects present in all stellar environments whose nature and formation channels are still partially unclear. They seem to be particularly abundant in open clusters (OCs), thus offering a unique chance to tackle these problems statistically. We aim at building up a new and homogeneous catalogue of blue straggler stars (BSS) in Galactic OCs using Gaia to provide a more solid assessment of these stars membership. Then, we aim at exploring possible relationships of the straggler abundance with the parent cluster structural and dynamical parameters. As a by-product, we also search for possible yellow straggler stars (YSS), which are believed to be stragglers in a more advanced evolution stage. We employ photometry, proper motions, and parallaxes extracted from Gaia DR2 for 408 Galactic star clusters and searched for stragglers within them after performing a careful membership analysis. The number of BBS emerging from our more stringent, selection criteria turns out to be significantly smaller than in previous versions of this catalogue. OCs are therefore not anymore a preferable environment for this kind of stars. Besides, we found that BSS start to appear in clusters with ages larger than log(t)~8.7 and are therefore absent in very young star clusters. The present catalogue supersedes the previous one from Ahumada et al. (2007A&A...463..789A, Cat. J/A+A/463/789) in several ways: membership assessment, number of stragglers found, and so forth. The new list includes 889 BSS and 77 YSS candidates in 408 OCs. We expect this catalogue to be the basis for a new round of studies of blue and yellow straggler stars.
- ID:
- ivo://CDS.VizieR/J/A+AS/109/375
- Title:
- Blue stragglers in open clusters
- Short Name:
- J/A+AS/109/375
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An amount of 959 blue straggler candidates were selected from their position in the colour-magnitude diagram in 390 open clusters of all ages. A set of basic data is given for every cluster and blue straggler.
- ID:
- ivo://CDS.VizieR/J/A+A/463/789
- Title:
- Blue stragglers in open clusters
- Short Name:
- J/A+A/463/789
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of blue-straggler candidates in galactic open clusters. It is based on the inspection of the colour-magnitude diagrams of the clusters, and it updates and supersedes the first version (Ahumada & Lapasset, 1995, Cat. <J/A+AS/109/375>). A new bibliographical search was made for each cluster, and the resulting information is organised into two tables. Some methodological aspects have been revised, in particular those concerning the delimitation of the area in the diagrams where the stragglers are selected. A total of 1887 blue-straggler candidates have been found in 427 open clusters of all ages, doubling the original number. The catalogued stars are classified into two categories mainly according to membership information.
- ID:
- ivo://CDS.VizieR/J/A+A/459/489
- Title:
- Blue straggler stars in open clusters
- Short Name:
- J/A+A/459/489
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents a new homogeneous catalogue of blue straggler stars (BSS) in Galactic open clusters. Photometric data for 216 clusters were collected from the literature and 2782 BSS candidates were extracted from 76 of them. We found that the anticorrelation of BSS frequency vs. total magnitude identified in similar studies conducted on Galactic globular clusters extends to the open cluster regime: clusters with smaller total magnitude tend to have higher BSS frequencies. Moreover, a clear correlation between the BSS frequency (obtained normalising the total number of BSS either to the total cluster mass or, for the older clusters, to the total number of clump stars) and the age of the clusters was found. A simple model is developed here to try to explain this last and new result. The model allows us to ascertain the important effect played by mass loss in the evolution of open clusters.
- ID:
- ivo://CDS.VizieR/III/59
- Title:
- Catalogue and Bibliography of Mn-Hg Stars
- Short Name:
- III/59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the present catalogue all Ap stars of the type Mn-Hg, Mn or Hg are summarized. Also, the stars which are suspected to be of this type are included. If in the literature two or more classifications of a star indicate the same type (or one with high dispersion) it is listed as of known type. If only doubtful or different classifications exist for a star, it is indicated as suspected.
