- ID:
- ivo://CDS.VizieR/J/A+A/310/164
- Title:
- Line profile variations in eta Ori
- Short Name:
- J/A+A/310/164
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Eta Orionis (HD35411) is a multiple system which consists of at least four early B-type stars. In the present paper we focus on the double-lined spectroscopic eclipsing pair Aab, and in particular on component Ab, which is a remarkable intrinsically variable star. The presence of this variable in an eclipsing system enables us to determine accurately its mass, radius, inclination angle and rotation period.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/135/2424
- Title:
- Line strengths of early-type galaxies
- Short Name:
- J/AJ/135/2424
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present measurements of velocity dispersions and Lick indices for 509 galaxies in the local universe, based on high signal-to-noise, long-slit spectra obtained with the 1.52m ESO telescope at La Silla.
- ID:
- ivo://CDS.VizieR/J/A+A/639/A7
- Title:
- Li-rich and non-Li-rich K giants RVs
- Short Name:
- J/A+A/639/A7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The origin of the Li-rich K giants is still highly debated. Here, we investigate the incidence of binarity among this family from a nine-year radial-velocity monitoring of a sample of 11 Li-rich K giants using the HERMES spectrograph attached to the 1.2m Mercator Telescope. A sample of 13 non-Li-rich giants (8 of them being surrounded by dust according to IRAS, WISE, and ISO data) was monitored alongside. When compared to the binary frequency in a reference sample of 190K giants (containing 17.4% of definite spectroscopic binaries - SB - and 6.3% of possible spectroscopic binaries - SB?), the binary frequency appears normal among the Li-rich giants (2/11 definite binaries plus 2 possible binaries, or 18.2% SB + 18.2% SB?), after taking account of the small sample size through the hypergeometric probability distribution. Therefore, there appears to be no causal relationship between Li enrichment and binarity. Moreover, there is no correlation between Li enrichment and the presence of circumstellar dust, and the only correlation that could be found between Li enrichment and rapid rotation is that the most Li-enriched K giants appear to be fast-rotating stars. However, among the dusty K giants, the binary frequency is much higher (4/8 definite binaries plus 1 possible binary). The remaining 3 dusty K giants suffer from a radial-velocity jitter, as is expected for the most luminous K giants, which these are.
- ID:
- ivo://CDS.VizieR/J/A+A/538/A36
- Title:
- Lithium abundances of bulge RGB stars
- Short Name:
- J/A+A/538/A36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A small number of K-type giants on the red giant branch (RGB) is known to be very rich in lithium (Li). This fact is not accounted for by standard stellar evolution theory. The exact phase and mechanism of Li enrichment is still a matter of debate. Our goal is to probe the abundance of Li along the RGB, from its base to the tip, to confine Li-rich phases that are supposed to occur on the RGB. For this end, we obtained medium-resolution spectra with the FLAMES spectrograph at the VLT in GIRAFFE mode for a large sample of 401 low-mass RGB stars located in the Galactic bulge. The Li abundance was measured in the stars with a detectable Li 670.8 nm line by means of spectral synthesis with COMARCS model atmospheres. A new 2MASS J-K-Teff calibration from COMARCS models is presented in the Appendix. Thirty-one stars with a detectable Li line were identified, three of which are Li-rich according to the usual criterion (log{epsilon}_Li_>1.5). The stars are distributed all along the RGB, not concentrated in any particular phase of the red giant evolution (e.g. the luminosity bump or the red clump). The three Li-rich stars are clearly brighter than the luminosity bump and red clump, and do not show any signs of enhanced mass loss. We conclude that the Li enrichment mechanism cannot be restricted to a clearly defined phase of the RGB evolution of low-mass stars (M~1M_{sun}_), contrary to earlier suggestions from disk field stars.
- ID:
- ivo://CDS.VizieR/J/A+A/653/A13
- Title:
- Lithium in NGC 2243 and NGC 104
- Short Name:
- J/A+A/653/A13
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We aim to determine the initial Li content of two clusters of similar metallicity but very different age, the old open cluster NGC 2243 and the metal-rich globular cluster NGC 104. We compare the lithium abundances derived for a large sample of stars (from the turn-off to the red giant branch) in each cluster. For NGC 2243, the Li abundances are taken from the catalogues released by the Gaia-ESO Public Spectroscopic Survey, while for NGC 104 we measured the Li abundance using FLAMES/GIRAFFE spectra, which include both archival data and new observations.
- ID:
- ivo://CDS.VizieR/J/A+A/534/A95
- Title:
- LMC Cepheids radial velocities
- Short Name:
- J/A+A/534/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The extragalactic distance scale builds directly on the Cepheid Period-Luminosity (PL) relation as delineated by the sample of Cepheids in the Large Magellanic Cloud (LMC). However, the LMC is a dwarf irregular galaxy, quite different from the massive spiral galaxies used for calibrating the extragalactic distance scale. Recent investigations suggest that not only the zero-point but also the slope of the Milky Way PL relation differ significantly from that of the LMC, casting doubts on the universality of the Cepheid PL relation. We want to make a differential comparison of the PL relations in the two galaxies by delineating the PL relations using the same method, the infrared surface brightness method (IRSB), and the same precepts. The IRSB method is a Baade-Wesselink type method to determine individual distances to Cepheids. We apply a newly revised calibration of the method as described in an accompanying paper (Paper I, Cat. J/A+A/534/A94) to 36 LMC and five SMC Cepheids and delineate new PL relations in the V,I,J, & K bands as well as in the Wesenheit indices in the optical and near-IR. We present 509 new and accurate radial velocity measurements for a sample of 22 LMC Cepheids, enlarging our earlier sample of 14 stars to include 36 LMC Cepheids. The new calibration of the IRSB method is directly tied to the recent HST parallax measurements to ten Milky Way Cepheids, and we find a LMC barycenter distance modulus of 18.45+/-0.04 (random error only) from the 36 individual LMC Cepheid distances. In the J,K bands we find identical slopes for the LMC and Milky Way PL relations and only a weak metallicity effect on the zero points (consistent with a zero effect), metal poor stars being fainter. In the optical we find the Milky Way slopes are slightly shallower than the LMC slopes (but again consistent with no difference in the slopes) and small effects on the zero points. However, the important Wesenheit index in V,(V-I) shows a metallicity effect on the slope and on the zero point which is likely to be significant. We find a significant metallicity effect on the Wvi index gamma(Wvi)=-0.23+/-0.10mag/dex as well as an effect on the slope. The K-band PL relation on the other hand is found to be an excellent extragalactic standard candle being metallicity insensitive in both slope and zero-point and at the same time being reddening insensitive and showing the least internal dispersion.
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/1468
- Title:
- LMC post-AGB, post-RGB star and YSOs
- Short Name:
- J/MNRAS/454/1468
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out a search for optically visible post-Asymptotic Giant Branch (post- AGB) stars in the Large Magellanic Cloud (LMC). First, we selected candidates with a mid-IR excess and then obtained their optical spectra. We disentangled contaminants with unique spectra such as M-stars, C-stars, planetary nebulae, quasi-stellar objects and background galaxies. Subsequently, we performed a detailed spectroscopic analysis of the remaining candidates to estimate their stellar parameters such as effective temperature, surface gravity (logg), metallicity ([Fe/H]), reddening and their luminosities. This resulted in a sample of 35 likely post-AGB candidates with late-G to late-A spectral types, low logg, and [Fe/H]<-0.5. Furthermore, our study con- firmed the existence of the dusty post-Red Giant Branch (post-RGB) stars, discovered previously in our SMC survey, by revealing 119 such objects in the LMC. These objects have mid-IR excesses and stellar parameters (Teff, logg, [Fe/H]) similar to those of post-AGB stars except that their luminosities (<2500L_{sun}_), and hence masses and radii, are lower. These post-RGB stars are likely to be products of binary interaction on the RGB. The post-AGB and post-RGB objects show SED properties similar to the Galactic post-AGB stars, where some have a surrounding circumstellar shell, while some others have a surrounding stable disc similar to the Galactic post-AGB binaries. This study also resulted in a new sample of 162 young stellar objects, identified based on a robust logg criterion. Other interesting outcomes include objects with an UV continuum and an emission line spectrum; luminous supergiants; hot main-sequence stars; and 15 B[e] star candidates, 12 of which are newly discovered in this study.
- ID:
- ivo://CDS.VizieR/J/MNRAS/399/2063
- Title:
- LMC red giants in D sequence
- Short Name:
- J/MNRAS/399/2063
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of a sample of Large Magellanic Cloud red giants exhibiting Long Secondary Periods (LSPs). We use radial velocities obtained from VLT spectral observations and MACHO and OGLE light curves to examine properties of the stars and to evaluate models for the cause of LSPs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/405/1770
- Title:
- LMC red giants in E sequence
- Short Name:
- J/MNRAS/405/1770
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have studied a sample of Large Magellanic Cloud red giant binaries that lie on sequence E in the period-luminosity plane. We show that their combined light and velocity curves unambiguously demonstrate that they are binaries showing ellipsoidal variability. By comparing the phased light and velocity curves of both sequence D and E variables, we show that the sequence D variation - the long secondary period - is not caused by ellipsoidal variability. We also demonstrate several further differences between stars on sequences D and E. These include differences in velocity amplitude, in the distribution of eccentricity and in the correlations of velocity amplitude with luminosity and period. We also show that the sequence E stars, unlike stars on sequence D, do not show any evidence of a mid-infrared excess that would indicate circumstellar dust.
- ID:
- ivo://CDS.VizieR/J/A+A/423/97
- Title:
- LMC RR Lyrae radial velocities
- Short Name:
- J/A+A/423/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the radial velocities, metallicities and the K-band magnitudes of 74 RR Lyrae stars in the inner regions of the LMC. The intermediate resolution spectra and infrared images were obtained with FORS1 at the ESO VLT and with the SOFI infrared imager at the ESO NTT.
