- ID:
- ivo://CDS.VizieR/J/A+A/398/647
- Title:
- Rotational velocities of F and G stars
- Short Name:
- J/A+A/398/647
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed study of rotation and differential rotation analyzing high resolution high S/N spectra of 142 F-, G- and early K-type field stars. Using Least Squares Deconvolution we obtain broadening profiles for our sample stars and use the Fourier transform method to determine projected rotational velocities vsini. Distributions of rotational velocities and periods are studied in the HR-diagram. For a subsample of 32 stars of spectral type F0-G0 we derive the amount of differential rotation. We find evidence for differential rotation in ten of the 32 stars. The observations were done with the ESO 3.6m telescope at La Silla, Chile, in October 2000, October 2001 and April 2002. The CES instrument (resolution 235000) was used, in the wavelength regions 577-581nm and 322.5-627nm.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/858/92
- Title:
- RPA Southern Pilot Search of 107 Stars
- Short Name:
- J/ApJ/858/92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The recent detection of a binary neutron star merger and the clear evidence for the decay of radioactive material observed in this event have, after 60 years of effort, provided an astrophysical site for the rapid neutron- capture (r-) process which is responsible for the production of the heaviest elements in our universe. However, observations of metal-poor stars with highly-enhanced r-process elements have revealed abundance patterns suggesting that multiple sites may be involved. To address this issue and to advance our understanding of the r-process, we have initiated an extensive search for bright (V<13.5), very metal-poor ([Fe/H]<-2) stars in the Milky Way halo exhibiting strongly-enhanced r-process signatures. This paper presents the first sample collected in the southern hemisphere using the echelle spectrograph on du Pont 2.5m telescope at Las Campanas Observatory. We have observed and analyzed 107 stars with -3.13<[Fe/H]<-0.79. Of those, 12 stars are strongly enhanced in heavy r-process elements (r-II), 42 stars show moderate enhancements of heavy r-process material (r-I), and 20 stars exhibit low abundances of the heavy r-process elements and higher abundances of the light r-process elements relative to the heavy ones (limited-r). This search is more successful at finding r- process-enhanced stars compared to previous searches, primarily due to a refined target-selection procedure.
- ID:
- ivo://CDS.VizieR/J/ApJS/249/30
- Title:
- R-Process Alliance: metal-poor star spectroscopy
- Short Name:
- J/ApJS/249/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This compilation is the fourth data release from the R-Process Alliance (RPA) search for r-process-enhanced stars and the second release based on "snapshot" high-resolution (R~30000) spectra collected with the du Pont 2.5m Telescope. In this data release, we propose a new delineation between the r-I and r-II stellar classes at [Eu/Fe]=+0.7, instead of the empirically chosen [Eu/Fe]=+1.0 level previously in use, based on statistical tests of the complete set of RPA data released to date. We also statistically justify the minimum level of [Eu/Fe] for definition of the r-I stars, [Eu/Fe]>+0.3. Redefining the separation between r-I and r-II stars will aid in the analysis of the possible progenitors of these two classes of stars and determine whether these signatures arise from separate astrophysical sources at all. Applying this redefinition to previous RPA data, the number of identified r-II and r-I stars changes to 51 and 121, respectively, from the initial set of data releases published thus far. In this data release, we identify 21 new r-II, 111 new r-I (plus 3 re-identified), and 7 new (plus 1 re-identified) limited-r stars out of a total of 232 target stars, resulting in a total sample of 72 new r-II stars, 232 new r-I stars, and 42 new limited-r stars identified by the RPA to date.
- ID:
- ivo://CDS.VizieR/J/ApJ/868/110
- Title:
- R-Process Alliance: 1st release in Galactic halo
- Short Name:
- J/ApJ/868/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the detailed abundances and r-process classifications of 125 newly identified metal-poor stars as part of an ongoing collaboration, the R-Process Alliance. The stars were identified as metal-poor candidates from the RAdial Velocity Experiment (RAVE) and were followed up at high spectral resolution (R~31500) with the 3.5m telescope at Apache Point Observatory. The atmospheric parameters were determined spectroscopically from FeI lines, taking into account <3D> non-LTE corrections and using differential abundances with respect to a set of standards. Of the 125 new stars, 124 have [Fe/H]{<}-1.5, 105 have [Fe/H]{<}-2.0, and 4 have [Fe/H]{<}-3.0. Nine new carbon-enhanced metal-poor stars have been discovered, three of which are enhanced in r-process elements. Abundances of neutron-capture elements reveal 60 new r-I stars (with +0.3<=[Eu/Fe]<=+1.0 and [Ba/Eu]<0) and 4 new r-II stars (with [Eu/Fe]>+1.0). Nineteen stars are found to exhibit a "limited-r" signature ([Sr/Ba]>+0.5, [Ba/Eu]<0). For the r-II stars, the second- and third-peak main r-process patterns are consistent with the r-process signature in other metal-poor stars and the Sun. The abundances of the light, {alpha}, and Fe-peak elements match those of typical Milky Way (MW) halo stars, except for one r-I star that has high Na and low Mg, characteristic of globular cluster stars. Parallaxes and proper motions from the second Gaia data release yield UVW space velocities for these stars that are consistent with membership in the MW halo. Intriguingly, all r-II and the majority of r-I stars have retrograde orbits, which may indicate an accretion origin.
- ID:
- ivo://CDS.VizieR/J/ApJ/750/76
- Title:
- r-process peaks elements in HD 160617
- Short Name:
- J/ApJ/750/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first detection of elements at all three r-process peaks in the metal-poor halo star HD 160617. These elements include arsenic and selenium, which have not been detected previously in halo stars, and the elements tellurium, osmium, iridium, and platinum, which have been detected previously. Absorption lines of these elements are found in archive observations made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. We present up-to-date absolute atomic transition probabilities and complete line component patterns for these elements. Additional archival spectra of this star from several ground-based instruments allow us to derive abundances or upper limits of 45 elements in HD 160617, including 27 elements produced by neutron-capture reactions. The average abundances of the elements at the three r-process peaks are similar to the predicted solar system r-process residuals when scaled to the abundances in the rare earth element domain. This result for arsenic and selenium may be surprising in light of predictions that the production of the lightest r-process elements generally should be decoupled from the heavier r-process elements.
- ID:
- ivo://CDS.VizieR/J/MNRAS/412/843
- Title:
- SAGA extremely metal-poor stars
- Short Name:
- J/MNRAS/412/843
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the characteristics of known extremely metal-poor (EMP) stars in the Galaxy using the Stellar Abundances for Galactic Archaeology (SAGA) data base. We find the transition of the initial mass function to be at [Fe/H]~-2 from the viewpoint of the distribution of carbon abundance and the frequency of carbon-enhanced stars. Analyses of carbon-enhanced stars in our sample suggest that nucleosynthesis in asymptotic giant branch (AGB) stars can contribute to carbon enrichment in a different way depending on whether the metallicity is above or below [Fe/H]~-2.5, which is consistent with the current models of stellar evolution at low metallicity.
- ID:
- ivo://CDS.VizieR/J/ApJ/649/L61
- Title:
- SDSS J155810.16-003120.0 abundances
- Short Name:
- J/ApJ/649/L61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a measurement of the D/H abundance ratio in a metal-poor damped Ly{alpha}(DLA) system along the sight line of QSO SDSS 1558-0031.
- ID:
- ivo://CDS.VizieR/J/ApJ/648/L97
- Title:
- 2 SDSS QSOs supersolar super-Lyman limit systems
- Short Name:
- J/ApJ/648/L97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present abundance measurements for two super-Lyman limit systems (SLLSs; quasar absorption-line systems with 10^19^cm^-2^<N_HI_<10^20.3^cm^-2^) selected from a set of metal-strong absorbers in the SDSS quasar database.
- ID:
- ivo://CDS.VizieR/J/AJ/162/125
- Title:
- Searching transiting planets around halo stars. I.
- Short Name:
- J/AJ/162/125
- Date:
- 21 Mar 2022 00:52:16
- Publisher:
- CDS
- Description:
- By measuring the elemental abundances of a star, we can gain insight into the composition of its initial gas cloud-the formation site of the star and its planets. Planet formation requires metals, the availability of which is determined by the elemental abundance. In the case where metals are extremely deficient, planet formation can be stifled. To investigate such a scenario requires a large sample of metal-poor stars and a search for planets therein. This paper focuses on the selection and validation of a halo star sample. We select ~17000 metal-poor halo stars based on their Galactic kinematics, and confirm their low metallicities ([Fe/H]<-0.5), using spectroscopy from the literature. Furthermore, we perform high-resolution spectroscopic observations using LBT/PEPSI and conduct detailed metallicity ([Fe/H]) analyses on a sample of 13 previously-known halo stars that also have hot kinematics. We can use the halo star sample presented here to measure the frequency of planets and to test planet formation in extremely metal-poor environments. The result of the planet search and its implications will be presented and discussed in a companion paper by Boley et al.
- ID:
- ivo://CDS.VizieR/J/ApJ/860/125
- Title:
- Six warm metal-poor stars iron abundances
- Short Name:
- J/ApJ/860/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Neutral Fe lines in metal-poor stars yield conflicting abundances depending on whether and how deviations from local thermodynamic equilibrium (LTE) are considered. We have collected new high-resolution and high signal-to-noise ultraviolet (UV) spectra of three warm dwarf stars with [Fe/H]~-2.9 with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. We locate archival UV spectra for three other warm dwarfs with [Fe/H]~-3.3, -2.2, and -1.6, supplemented with optical spectra for all six stars. We calculate stellar parameters using methods that are largely independent of the spectra, adopting broadband photometry, color-temperature relations, Gaia parallaxes, and assumed masses. We use the LTE line analysis code MOOG to derive Fe abundances from hundreds of FeI and FeII lines with wavelengths from 2290 to 6430{AA}. The [Fe/H] ratios derived separately from FeI and FeII lines agree in all six stars, with [FeII/H]-[FeI/H] ranging from +0.00+/-0.07 to -0.12+/-0.09dex, when strong lines and FeI lines with lower excitation potential <1.2eV are excluded. This constrains the extent of any deviations from LTE that may occur within this parameter range. While our result confirms non-LTE calculations for some warm, metal-poor dwarfs, it may not be generalizable to more metal-poor dwarfs, where deviations from LTE are predicted to be larger. We also investigate trends of systematically lower abundances derived from FeI lines in the Balmer continuum region (~3100-3700{AA}), and we conclude that no proposed explanation for this effect can fully account for the observations presently available.
