- ID:
- ivo://CDS.VizieR/J/A+AS/139/425
- Title:
- CCD photometry and astrometry of double stars
- Short Name:
- J/A+AS/139/425
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photometric and astrometric data of about 280 visual double stars of the "intermediate" class, i.e. with angular separations mainly in the range 2"<{rho}<12". The observations have been obtained in 1991-92 with a CCD camera attached to the 91cm Dutch telescope at ESO La Silla, Chile. Differential magnitudes of the double star components as well as magnitudes and colour indices of the individual components have been determined in the Cousins V and I passbands with an internal error of about 0.005mag and an external accuracy of less than 0.03mag. In addition, angular separations have been secured to an internal accuracy of 0.004" and position angles to about 0.05{deg}.
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- ID:
- ivo://CDS.VizieR/J/A+A/374/132
- Title:
- CCD photometry and astrometry of double stars
- Short Name:
- J/A+A/374/132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new astrometric and photometric data for 253 visual double stars of the "intermediate" class, i.e. with angular separations in the range 1 to 15 arcsec. The multi-colour observations were obtained in 1992-94 as part of the ESO Key Programme "Visual Double Stars" performed at La Silla Observatory (Chile). Differential magnitudes and colours have been secured in a systematic way while component magnitudes and colour indices have been determined in the V and I passbands of the Cousins standard system in good photometric conditions only. Internal and mean external errors are respectively smaller than 0.01mag and a few hundred of a magnitude (0.02 to 0.03mag). Relative positions are obtained as a by-product with internal errors of the order of 0.006arcsec in angular separation and 0.08{deg} in position angle. Final accuracies are thoroughly discussed: we illustrate the overall excellent quality of the data and estimate the quality degradation for angular separations barely larger than the width of the seeing disk.
- ID:
- ivo://CDS.VizieR/J/AJ/120/2638
- Title:
- CCD speckle obs. of binary stars. II.
- Short Name:
- J/AJ/120/2638
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Speckle observations of 145 double stars and suspected double stars are presented and discussed. On the basis of multiple observations, a total of 280 position angle and separation measures are determined, as well as 23 high-quality nondetections. All observations were taken with the (unintensified) Rochester Institute of Technology fast-readout CCD camera mounted on the Lowell-Tololo 61 cm telescope at the Cerro Tololo Inter-American Observatory during 1999 October. We find that the measures, when judged as a whole against ephemeris positions of binaries with very well-known orbits, have root mean square deviations of 18+/-03{deg} in position angle and 13+/-2mas in separation. Eleven double stars discovered by Hipparcos were also successfully observed, and the change in position angle and/or separation since the Hipparcos observations was substantial in three cases.
- ID:
- ivo://CDS.VizieR/J/A+AS/124/353
- Title:
- CCD UBV photometry of close visual doubles
- Short Name:
- J/A+AS/124/353
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present V magnitudes, (B-V) and (U-B) colours of close visual double star components, and their differences as well as separations and position angles of 40 visual double stars. The common properties of the members of this sample are the small angular separation {rho}, which is less than 7", and the common spectral type of the primaries, which are of G-type. The observations made with the Bessel U, B and V filters, while the astrometry was performed in the V filter only. For the observations, the CCD camera attached to the Cassegrain focus of the 90 cm Dutch telescope, at La Silla, Chile, had been used. From the analysis of the data we concluded that from the sample of the fourty double stars observed seven proved to be physical pairs, while the rest must have common origin components.
- ID:
- ivo://CDS.VizieR/J/A+A/581/A22
- Title:
- 67 CEMP-s stars model analysis
- Short Name:
- J/A+A/581/A22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Many of the carbon-enhanced metal-poor (CEMP) stars that we observe in the Galactic halo are found in binary systems and show enhanced abundances of elements produced by the slow neutron-capture process (s-elements). The origin of the peculiar chemical abundances of these CEMP-s stars is believed to be accretion in the past of enriched material from a primary star in the asymptotic giant branch (AGB) phase of its evolution. We investigate the mechanism of mass transfer and the process of nucleosynthesis in low-metallicity AGB stars by modelling the binary systems in which the observed CEMP-s stars were formed. For this purpose we compare a sample of 67 CEMP-s stars with a grid of binary stars generated by our binary evolution and nucleosynthesis model. We classify our sample CEMP-s stars in three groups based on the observed abundance of europium. In CEMP-s/r stars the europium-to-iron ratio is more than ten times higher than in the Sun, whereas it is lower than this threshold in CEMP-s/nr stars. No measurement of europium is currently available for CEMP-s/ur stars. On average our models reproduce the abundances observed in CEMP-s/nr stars well, whereas in CEMP-s/r stars and CEMP-s/ur stars the abundances of the light-s elements (strontium, yttrium, zirconium) are systematically overpredicted by our models, and in CEMP-s/r stars the abundances of the heavy-s elements (barium, lanthanum) are underestimated. In all stars our modelled abundances of sodium overestimate the observations. This discrepancy is reduced only in models that underestimate the abundances of most of the s-elements. Furthermore, the abundance of lead is underpredicted in most of our model stars, independent of the metallicity. These results point to the limitations of our AGB nucleosynthesis model, particularly in the predictions of the element-to-element ratios. In our models CEMP-s stars are typically formed in wide systems with periods above 10000-days, while most of the observed CEMP-s stars are found in relatively close orbits with periods below 5000-days. This evidence suggests that either the sample of CEMP-s binary stars with known orbital parameters is biased towards short periods or that our wind mass-transfer model requires more efficient accretion in close orbits.
- ID:
- ivo://CDS.VizieR/J/ApJ/799/163
- Title:
- Chandra observations of solar analogs
- Short Name:
- J/ApJ/799/163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate whether magnetic interaction between close-in giant planets and their host stars produce observable statistical enhancements in stellar coronal or chromospheric activity. New Chandra observations of 12 nearby (d<60pc) planet-hosting solar analogs are combined with archival Chandra, XMM-Newton, and ROSAT coverage of 11 similar stars to construct a sample inoculated against inherent stellar class and planet-detection biases. Survival analysis and Bayesian regression methods (incorporating both measurements errors and X-ray upper limits; 13/23 stars have secure detections) are used to test whether "hot Jupiter" hosts are systematically more X-ray luminous than comparable stars with more distant or smaller planets. No significant correlations are present between common proxies for interaction strength (M_P_/a^2^ or 1/a) versus coronal activity (L_X_ or L_X_/L_bol_). In contrast, a sample of 198 FGK main-sequence stars does show a significant (~99% confidence) increase in X-ray luminosity with M_P_/a^2^. While selection biases are incontrovertibly present within the main-sequence sample, we demonstrate that the effect is primarily driven by a handful of extreme hot-Jupiter systems with M_P_/a^2^>450M_Jup_AU^-2^, which here are all X-ray luminous but to a degree commensurate with their Ca II H and K activity, in contrast to presented magnetic star-planet interaction scenarios that predict enhancements relatively larger in L_X_. We discuss these results in the context of cumulative tidal spin-up of stars hosting close-in gas giants (potentially followed by planetary infall and destruction). We also test our main-sequence sample for correlations between planetary properties and UV luminosity or Ca II H and K emission, and find no significant dependence.
- ID:
- ivo://CDS.VizieR/J/A+A/599/A90
- Title:
- Characterization of HD 108874 system
- Short Name:
- J/A+A/599/A90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to understand the observed physical and orbital diversity of extrasolar planetary systems, a full investigation of these objects and of their host stars is necessary. Within this field, one of the main purposes of the GAPS observing project with HARPS-N@TNG is to provide a more detailed characterisation of already known systems. In this framework we monitored the star, hosting two giant planets, HD108874, with HARPS-N for three years in order to refine the orbits, to improve the dynamical study and to search for additional low-mass planets in close orbits. We subtracted the radial velocity (RV) signal due to the known outer planets, finding a clear modulation of 40.2d period. We analysed the correlation between RV residuals and the activity indicators and modelled the magnetic activity with a dedicated code. Our analysis suggests that the 40.2d periodicity is a signature of the rotation period of the star. A refined orbital solution is provided, revealing that the system is close to a mean motion resonance of about 9:2, in a stable configuration over 1Gyr. Stable orbits for low-mass planets are limited to regions very close to the star or far from it. Our data exclude super-Earths with Msini>~5M_{earth}_ within 0.4AU and objects with Msini>~2M_{earth}_ with orbital periods of a few days. Finally we put constraints on the habitable zone of the system, assuming the presence of an exomoon orbiting the inner giant planet.
- ID:
- ivo://CDS.VizieR/J/A+A/475/1125
- Title:
- Characterization of the hot Neptune GJ 436b
- Short Name:
- J/A+A/475/1125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Spitzer Space Telescope infrared photometry of a secondary eclipse as well as ground-based photometric and spectroscopic measurements of the hot Neptune GJ 436b.
- ID:
- ivo://CDS.VizieR/J/AJ/148/48
- Title:
- CHARA obs. of omega And, HD 178911, xi Cep
- Short Name:
- J/AJ/148/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- When observed with optical long-baseline interferometers, components of a binary star that are sufficiently separated produce their own interferometric fringe packets; these are referred to as separated fringe packet (SFP) binaries. These SFP binaries can overlap in angular separation with the regime of systems resolvable by speckle interferometry at single, large-aperture telescopes and can provide additional measurements for preliminary orbits lacking good phase coverage, help constrain elements of already established orbits, and locate new binaries in the undersampled regime between the bounds of spectroscopic surveys and speckle interferometry. In this process, a visibility calibration star is not needed, and the SFPs can provide an accurate vector separation. In this paper, we apply the SFP approach to {omega} Andromeda, HD 178911, and {xi} Cephei with the CLIMB three-beam combiner at the CHARA Array. For these systems we determine component masses and parallax of 0.963+/-0.049M_{sun}_ and 0.860+/-0.051M_{sun}_ and 39.54+/-1.85mas for {omega} Andromeda, for HD 178911 of 0.802+/-0.055M_{sun}_and 0.622+/-0.053M_{sun}_with 28.26+/-1.70mas, and masses of 1.045+/-0.031M_{sun}_and 0.408+/-0.066M_{sun}_and 38.10+/-2.81mas for {xi} Cephei.
- ID:
- ivo://CDS.VizieR/J/A+A/599/A96
- Title:
- [C/H] Chemical abundances of 1110 stars
- Short Name:
- J/A+A/599/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Carbon, oxygen and nitrogen (CNO) are key elements in stellar formation and evolution, and their abundances should also have a significant impact on planetary formation and evolution. We aim to present a detailed spectroscopic analysis of 1110 solar-type stars, 143 of which are known to have planetary companions. We have determined the carbon abundances of these stars and investigate a possible connection between C and the presence of planetary companions. We used the HARPS spectrograph to obtain high-resolution optical spectra of our targets. Spectral synthesis of the CH band at 4300{AA} was performed with the spectral synthesis codes MOOG and FITTING. We have studied carbon in several reliable spectral windows and have obtained abundances and distributions that show that planet host stars are carbon rich when compared to single stars, a signature caused by the known metal-rich nature of stars with planets. We find no different behaviour when separating the stars by the mass of the planetary companion. We conclude that reliable carbon abundances can be derived for solar-type stars from the CH band at 4300{AA}. We confirm two different slope trends for [C/Fe] with [Fe/H] because the behaviour is opposite for stars above and below solar values. We observe a flat distribution of the [C/Fe] ratio for all planetary masses, a finding that apparently excludes any clear connection between the [C/Fe] abundance ratio and planetary mass.
