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Start Over Subject s stars Publisher CDS Content Level Research
1. A grid of MARCS model atmospheres for S stars
ID:
ivo://CDS.VizieR/J/A+A/601/A10
Title:
A grid of MARCS model atmospheres for S stars
Short Name:
J/A+A/601/A10
Date:
21 Oct 2021
Publisher:
CDS
Description:
S-type stars are late-type giants whose atmospheres are enriched in carbon and s-process elements because of either extrinsic pollution by a binary companion or intrinsic nucleosynthesis and dredge-up on the thermally-pulsing asymptotic giant branch. A grid of MARCS model atmospheres has been computed for S stars, covering the range 2700<=Teff(K)<=4000, 0.50<=C/O<0.99, 0<=logg<=5, [Fe/H]=0., -0.5dex, and [s/Fe]= 0, 1, and 2 dex (where the latter quantity refers to the global overabundance of s-process elements). The MARCS models make use of a new ZrO line list. Synthetic spectra computed from these models are used to derive photometric indices in the Johnson and Geneva systems, as well as TiO and ZrO band strengths. A method is proposed to select the model best matching any given S star, a non-trivial operation since the grid contains more than 3500 models covering a five-dimensional parameter space. The method is based on the comparison between observed and synthetic photometric indices and spectral band strengths, and has been applied on a vast subsample of the Henize sample of S stars. Our results confirm the old claim by Piccirillo (1980MNRAS.190..441P) that ZrO bands in warm S stars (Teff > 3200K) are not caused by the C/O ratio being close to unity, as traditionally believed, but rather by some Zr overabundance. The TiO and ZrO band strengths, combined with V-K and J-K photometric indices, are used to select Teff, C/O, [Fe/H] and [s/Fe]. The Geneva U-B_1 and B_2-V_1 indices (or any equivalent) are good at selecting the gravity. The defining spectral features of dwarf S stars are outlined, but none is found among the Henize S stars. More generally, it is found that, at Teff=3200K, a change of C/O from 0.5 to 0.99 has a strong impact on V-K (2mag). Conversely, a range of 2 mag in V-K corresponds to a 200K shift along the (Teff, V-K) relationship (for a fixed C/O value). Hence, the use of a (Teff, V-K) calibration established for M stars will yield large errors for S stars, so that a specific calibration must be used, as provided in the present paper. Using the atmospheric parameters derived by our method for the sample of Henize S stars, we show that the extrinsic-intrinsic dichotomy among S stars reveals itself very clearly as a bimodal distribution in the effective temperatures. Moreover, the increase of s-process element abundances with increasing C/O ratios and decreasing temperatures is apparent among intrinsic stars, confirming theoretical expectations.
2. A Jupiter-mass companion around HD 109246
ID:
ivo://CDS.VizieR/J/A+A/523/A88
Title:
A Jupiter-mass companion around HD 109246
Short Name:
J/A+A/523/A88
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the detection of a Jupiter-mass planet discovered with the SOPHIE spectrograph mounted on the 1.93-m telescope at the Haute-Provence Observatory. The new planet orbits HD 109246, a G0V star slightly more metallic than the Sun. HD 109246b has a minimum mass of 0.77M_{jup}_, an orbital period of 68 days, and an eccentricity of 0.12. It is placed in a sparsely populated region of the period distribution of extrasolar planets. We also present a correction method for the so-called seeing effect that affects the SOPHIE radial velocities. We complement this discovery announcement with a description of some calibrations that are implemented in the SOPHIE automatic reduction pipeline. These calibrations allow the derivation of the photon-noise radial velocity uncertainty and some useful stellar properties (vsini, [Fe/H], log R'hk) directly from the SOPHIE data.
3. A new IR study of intrinsic and extrinsic S-type stars
ID:
ivo://CDS.VizieR/J/AJ/158/22
Title:
A new IR study of intrinsic and extrinsic S-type stars
Short Name:
J/AJ/158/22
Date:
21 Oct 2021
Publisher:
CDS
Description:
We collect all known intrinsic and extrinsic S-type stars to discuss their infrared properties and find their difference in the infrared using photometric data from the Two Micron All Sky Survey, Wide Field Infrared Survey Explorer, and Infrared Astronomical Satellite missions. Then we look for the diagnosis to extract intrinsic S-type stars from the large unclassified sample. We found that, statistically, intrinsic S-type stars have larger infrared excesses than extrinsic S-type stars in the wavelength region of 1-60 {mu}m due to thicker dusty circumstellar envelopes. We also found that only intrinsic S-type stars occupy the reddest color areas in all of the two-color diagrams we presented. Finally, 172 new intrinsic S-type stars are presented in this paper. This makes the number of known intrinsic S-type stars almost double. In addition, some intrinsic and extrinsic S-type stars have power-law distributions in some two-color diagrams with the wavelength longer than 5 {mu}m. The possible reason for this is also discussed.
4. Barium and related stars and WD companions
ID:
ivo://CDS.VizieR/J/A+A/626/A127
Title:
Barium and related stars and WD companions
Short Name:
J/A+A/626/A127
Date:
21 Oct 2021
Publisher:
CDS
Description:
This paper provides long-period and revised orbits for barium and S stars adding to previously published ones. The sample of barium stars with strong anomalies comprise all such stars present in the Lu et al. catalogue. We find orbital motion for all barium and extrinsic S stars monitored. We obtain the longest period known so far for a spectroscopic binary involving an S star, namely 57 Peg with a period of the order of 100-500yr. We present the mass distribution for the barium stars, which ranges from 1 to 3M_{sun}_, with a tail extending up to 5M_{sun}_ in the case of mild barium stars. This high-mass tail comprises mostly high-metallicity objects ([Fe/H]>=-0.1). Mass functions are compatible with WD companions and we derive their mass distribution which ranges from 0.5 to 1 Msun. Using the initial - final mass relationship established for field WDs, we derived the distribution of the mass ratio q'=M_AGB,ini_/M_Ba_ (where M_AGB,ini_ is the WD progenitor initial mass, i.e., the mass of the system former primary component) which is a proxy for the initial mass ratio. It appears that the distribution of q' is highly non uniform, and significantly different for mild and strong barium stars, the latter being characterized by values mostly in excess of 1.4, whereas mild barium stars occupy the range 1-1.4. We investigate as well the correlation between abundances, orbital periods, metallicities, and masses (barium star and WD companion). The 105 orbits of post-mass-transfer systems presented in this paper pave the way for a comparison with binary-evolution models.
5. BV(RI)C photometry of 4 S-type AGB
ID:
ivo://CDS.VizieR/J/BaltA/14/41
Title:
BV(RI)C photometry of 4 S-type AGB
Short Name:
J/BaltA/14/41
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present FCAPT differential Johnson BV and Cousins RI photometry and radial velocities of the S-type AGB stars RS Cnc, ST Her, OP Her and HR Peg. We performed multiperiodic analyses of this photometry to learn about the frequencies of variability. The B, V, R, and I light curves are generally in phase. RS Cnc has periods of order 122 and 248 days. Repeating the analyses using our data with the extensive V and R photometry of Percy et al. (2001PASP..113..983P) shows several periods near 248 days and a period near 135 days. The primary period of ST Her appears to be about 144 days although it is manifested most readily by its 103 day alias. OP Her and HR Peg exhibit periods, respectively, of about 416 and 116 days and of 54 and 74 days. The differences between our data set and the larger one of Percy et al. (2001PASP..113..983P) for RS Cnc raises important questions about multiperiodic analyses for AGB stars.
6. BVRI light curves of some cool giant stars
ID:
ivo://CDS.VizieR/J/other/JAD/13.3
Title:
BVRI light curves of some cool giant stars
Short Name:
J/other/JAD/13.3
Date:
21 Oct 2021
Publisher:
CDS
Description:
We examine Johnson BV and Cousins RI photometry of the cool giant stars HR 1105, HD 35155, HR 4088, TU CVn, IT Vir, and HR 7442, that the first author obtained with the Four College Automated Photoelectric Telescope. The new data for HR 1105 show that its variability is more complex than previously thought. Except a 0.3 phase gap in the photometry of HD 35155, the amplitude of variability is fairly constant. For HR 4088, except for one season, we did not find any periods shorter than 100 days. For the barium star IT Vir assuming the orbital period is the photometric period, the light curves consist of two similar subparts each one-half of the orbital period long. But there are problems with concluding that this star is an ellipsoidal variable. For HR 7442, more data is needed to derive an accurate period. A few observations are also presented of HR 1556, HR 363, HD 58521, and HD 49368.
7. BVRI photometry of HR 1105
ID:
ivo://CDS.VizieR/J/A+A/333/952
Title:
BVRI photometry of HR 1105
Short Name:
J/A+A/333/952
Date:
21 Oct 2021
Publisher:
CDS
Description:
BVRI photometry of the extrinsic S star HR 1105 shows a stable periodic light variability with a period of 24.76 days superimposed upon long term changes presumably related to the orbital period. The variations are in phase for all four magnitudes with the amplitude of this variability being about the same for B and V, but smaller for R and even smaller for I. As the primary is a M3 III star, these brightness changes are mostly likely due to the pulsation of the primary star.
8. Extrasolar planets. Radial velocities of 5 stars
ID:
ivo://CDS.VizieR/J/A+A/545/A55
Title:
Extrasolar planets. Radial velocities of 5 stars
Short Name:
J/A+A/545/A55
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present radial-velocity measurements obtained in one of a number of programs underway to search for extrasolar planets with the spectrograph SOPHIE at the 1.93-m telescope of the Haute-Provence Observatory. Targets were selected from catalogs observed with ELODIE, which had been mounted previously at the telescope, in order to detect long-period planets with an extended database close to 15 years.
9. Gaia-ESO Survey: Li-rich stars in NGC2547
ID:
ivo://CDS.VizieR/J/A+A/574/L7
Title:
Gaia-ESO Survey: Li-rich stars in NGC2547
Short Name:
J/A+A/574/L7
Date:
21 Oct 2021
Publisher:
CDS
Description:
The nearby (distance ~350-400pc), rich Vela OB2 association, includes gamma^2^ Velorum, one of the most massive binaries in the solar neighborhood, and is an excellent laboratory for investigating the formation and early evolution of young clusters. Recent Gaia-ESO survey observations led to the discovery of two kinematically distinct populations in the young (10-15Myr) cluster immediately surrounding gamma^2^ Velorum. Here we analyse the results of Gaia-ESO survey observations of NGC 2547, a 35Myr cluster located two degrees south of gamma^2^ Velorum. The radial velocity distribution of lithium-rich pre-main sequence stars shows a secondary population, kinematically distinct and younger than NGC 2547. The radial velocities, lithium absorption lines, and the positions in a color-magnitude diagram of this secondary population are consistent with those of one of the components discovered around gamma^2^ Velorum. This result shows that there is a young, low-mass stellar population spread over at least several square degrees in the Vela OB2 association. This population could have originally been part of a cluster around gamma^2^ Velorum that expanded after gas expulsion, or formed in a less dense environment spread over the whole Vela OB2 region.
10. General Catalog of S Stars, second edition
ID:
ivo://CDS.VizieR/III/168
Title:
General Catalog of S Stars, second edition
Short Name:
III/168
Date:
21 Oct 2021
Publisher:
CDS
Description:
This catalog is intended to list all Galactic S stars having known positions of at least roughly the precision of the Henry Draper catalog. An S star is a star in whose spectrum the bands of the ZrO molecule are detectable, ordinarily without needing sufficient spectral resolution to resolve the individual rotational lines of a band. In addition, stars exhibiting readily detectable LaO in the photographic infrared, where there is no significant ZrO, are known to form a subset of S stars (more extreme in abundances or low temperature), and this catalog includes stars classified only from the infrared. The majority of the stars were, however, discovered on the basis of the (0,0) band, with head near 6474Angstroem, of the red system of ZrO.

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