- ID:
- ivo://CDS.VizieR/J/AJ/160/104
- Title:
- {Epsilon} CrA components radial & orbital velocity
- Short Name:
- J/AJ/160/104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution spectroscopic observations of the W UMa-type binary {Epsilon}CrA obtained as a time-monitoring sequence on four full and four partial nights within two weeks have been used to derive orbital elements of the system and discuss the validity of the Lucy model for description of the radial-velocity data. The observations had more extensive temporal coverage and better quality than similar time-sequence observations of the contact binary AW UMa. The two binaries share several physical properties and show very similar deviations from the Lucy model: the primary component is a rapidly rotating star almost unaffected by the presence of the secondary component, while the latter is embedded in a complex gas flow and appears to have its own rotation-velocity field, in contradiction to the model. The spectroscopic mass ratio is found to be larger than the one derived from the light-curve analysis, as in many other W UMa-type binaries, but the discrepancy for {Epsilon} CrA is relatively minor, much smaller than for AW UMa. The presence of the complex velocity flows contradicting the assumption of solid-body rotation suggests a necessity of modification to the Lucy model, possibly along the lines outlined by Stepien in his concept of energy transfer between the binary components.
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- ID:
- ivo://CDS.VizieR/J/A+A/377/123
- Title:
- Equivalent widths of 6 binaries
- Short Name:
- J/A+A/377/123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed a careful differential abundance analysis of individual components of six main sequence binaries with separations of a few hundreds of AU. To reduce analysis concerns, we selected systems with almost equal mass components. We were able to derive differential abundances of several elements with errors down to 0.01dex in the best cases. We found that in four systems the two components have the same chemical composition, within these very severe limits. However, clear differences were found for the two remaining systems (HD 219542 and HD 200466), in both cases the primaries being more Fe-rich than the secondaries, by 0.091+/-0.009 and 0.053+/-0.024dex respectively. Similar differences were found for most of the elements considered in our analysis; however, we found no appreciable difference for volatile elements and a trend for increasing abundance differences with increasing condensation temperature for individual elements, a result similar to that found for some single stars with planets by Smith et al. (2001AJ....121.3207S). Finally, we note that HD 219542A has a Li-abundance comparable to those of Li-rich stars in old open clusters, while no Li is detected in the slightly cooler HD 219542B. We suggest that the primaries of these two systems have accreted rocky planets or the inner dust-rich part of a protoplanetary disk, likely due to gravitational perturbation caused by the presence of the companion.
- ID:
- ivo://CDS.VizieR/J/ApJ/819/19
- Title:
- Equivalent widths of WASP-94A and WASP-94B
- Short Name:
- J/ApJ/819/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Binary stars provide an ideal laboratory for investigating the potential effects of planet formation on stellar composition. Assuming that the stars formed in the same environment/from the same material, any compositional anomalies between binary components might indicate differences in how material was sequestered in planets, or accreted by the star in the process of planet formation. We present here a study of the elemental abundance differences between WASP-94A and B, a pair of stars that each host a hot Jupiter exoplanet. The two stars are very similar in spectral type (F8 and F9), and their ~2700AU separation suggests that their protoplanetary disks were likely not influenced by stellar interactions, but WASP-94Ab's orbit --misaligned with the host star spin axis and likely retrograde-- points toward a dynamically active formation mechanism, perhaps different from that of WASP-94Bb, which is not misaligned and has a nearly circular orbit. Based on our high-quality spectra and strictly relative abundance analysis, we detect a depletion of volatiles (~-0.02dex, on average) and enhancement of refractories (~0.01dex) in WASP-94A relative to B (standard errors are ~0.005dex). This is different from every other published case of binary host star abundances, in which either no significant abundance differences are reported or there is some degree of enhancement in all elements, including volatiles. Several scenarios that may explain the abundance trend are discussed, but none can be definitively accepted or rejected. Additional high-contrast imaging observations to search for companions that may be dynamically affecting the system, as well as a larger sample of binary host star studies, are needed to better understand the curious abundance trends we observe in WASP-94A and B.
- ID:
- ivo://CDS.VizieR/J/A+A/420/683
- Title:
- Equivalent widths of 23 wide binaries
- Short Name:
- J/A+A/420/683
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present iron abundance analysis for 23 wide binaries with main sequence components in the temperature range 4900-6300K, taken from the sample of the pairs currently included in the radial velocity planet search on going at the Telescopio Nazionale Galileo (TNG) using the high resolution spectrograph SARG. The use of a line-by-line differential analysis technique between the components of each pair allows us to reach errors of about 0.02dex in the iron content difference. Most of the pairs have abundance differences lower than 0.02dex and there are no pairs with differences larger than 0.07dex. The four cases of differences larger than 0.02dex may be spurious because of the larger error bars affecting pairs with large temperature difference, cold stars and rotating stars.
- ID:
- ivo://CDS.VizieR/J/other/Sci/350.64
- Title:
- 51 Eri b near-infrared spectrum
- Short Name:
- J/other/Sci/350.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Directly detecting thermal emission from young extrasolar planets allows measurement of their atmospheric composition and luminosity, which is influenced by their formation mechanism. Using the Gemini Planet Imager, we discovered a planet orbiting the ~20Myr-old star 51 Eridani at a projected separation of 13 astronomical units. Near-infrared observations show a spectrum with strong methane and water vapor absorption. Modeling of the spectra and photometry yields a luminosity of L/LS=1.6-4.0x10^-6^ and an effective temperature of 600-750K. For this age and luminosity, "hot-start" formation models indicate a mass twice that of Jupiter. This planet also has a sufficiently low luminosity to be consistent with the "cold- start" core accretion process that may have formed Jupiter.
- ID:
- ivo://CDS.VizieR/J/A+A/603/A57
- Title:
- 51 Eri b SPHERE/IFS spectra & atmosphere models
- Short Name:
- J/A+A/603/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 51 Eridani b is an exoplanet around a young (20Myr) nearby (29.4pc) F0-type star, which was recently discovered by direct imaging. It is one of the closest direct imaging planets in angular and physical separation (~0.5", ~13AU) and is well suited for spectroscopic analysis using integral field spectrographs. We aim to refine the atmospheric properties of the known giant planet and to constrain the architecture of the system further by searching for additional companions. We used the extreme adaptive optics instrument SPHERE at the Very Large Telescope (VLT) to obtain simultaneous dual-band imaging with IRDIS and integral field spectra with IFS, extending the spectral coverage of the planet to the complete Y- to H-band range and providing additional photometry in the K12-bands (2.11, 2.25 micron). We present the first spectrophotometric measurements in the Y and K bands for the planet and revise its J-band flux to values 40% fainter than previous measurements. Cloudy models with uniform cloud coverage provide a good match to the data. We derive the temperature, radius, surface gravity, metallicity, and cloud sedimentation parameter fsed. We find that the atmosphere is highly super-solar ([Fe/H]~1.0), and the low fsed~1.26 value is indicative of a vertically extended, optically thick cloud cover with small sized particles. The model radius and surface gravity estimates suggest higher planetary masses of M_gravity_=9.1^+4.9^_-3.3_. The evolutionary model only provides a lower mass limit of >2M_jupiter_ (for pure hot-start). The cold-start model cannot explain the luminosity of the planet. The SPHERE and NACO/SAM detection limits probe the 51 Eri system at solar system scales and exclude brown-dwarf companions more massive than 20M_jupiter_ beyond separations of ~2.5AU and giant planets more massive than 2M_jupiter_ beyond 9 au.
- ID:
- ivo://CDS.VizieR/J/A+A/629/A80
- Title:
- ESPRESSO blind RV exoplanet survey catalog
- Short Name:
- J/A+A/629/A80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One of the main scientific drivers for ESPRESSO, Echelle SPectrograph, is the detection and characterization of Earth-class exoplanets. With this goal in mind, the ESPRESSO guaranteed time observations (GTO) Catalog identifies the best target stars for a blind search for the radial velocity (RV) signals caused by Earth-class exoplanets. Using the most complete stellar catalogs available, we screened for the most suitable G, K, and M dwarf stars for the detection of Earth-class exoplanets with ESPRESSO. For most of the stars, we then gathered high-resolution spectra from new observations or from archival data. We used these spectra to spectroscopically investigate the existence of any stellar binaries, both bound or background stars. We derived the activity level using chromospheric activity indexes using log (R'_HK_), as well as the projected rotational velocity vsini. For the cases where planet companions are already known, we also looked at the possibility that additional planets may exist in the host's habitable zone using dynamical arguments. We estimated the spectroscopic contamination level, vsini, activity, stellar parameters and chemical abundances for 249 of the most promising targets. Using these data, we selected 45 stars that match our criteria for detectability of a planet like Earth. The stars presented and discussed in this paper constitute the ESPRESSO GTO catalog for the RV blind search for Earth-class planets. They can also be used for any other work requiring a detailed spectroscopic characterization of stars in the solar neighborhood.
- ID:
- ivo://CDS.VizieR/J/A+A/603/A30
- Title:
- Evidence for two distinct giant planet population
- Short Name:
- J/A+A/603/A30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Analysis of the statistical properties of exoplanets, together with those of their host stars, are providing a unique view into the process of planet formation and evolution. In this paper we explore the properties of the mass distribution of giant planet companions to solar-type stars, in a quest for clues about their formation process. With this goal in mind we studied, with the help of standard statistical tests, the mass distribution of giant planets using data from the exoplanet.eu catalog and the SWEET-Cat database of stellar parameters for stars with planets. We show that the mass distribution of giant planet companions is likely to present more than one population with a change in regime around 4M_{Jup}_. Above this value host stars tend to be more metal poor and more massive and have [Fe/H] distributions that are statistically similar to those observed in field stars of similar mass. On the other hand, stars that host planets below this limit show the well-known metallicity-giant planet frequency correlation. We discuss these results in light of various planet formation models and explore the implications they may have on our understanding of the formation of giant planets. In particular, we discuss the possibility that the existence of two separate populations of giant planets indicates that two different processes of formation are at play.
- ID:
- ivo://CDS.VizieR/J/ApJ/745/174
- Title:
- Evolutionary models of young gas-giant planets
- Short Name:
- J/ApJ/745/174
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gas-giant planets that form via core accretion might have very different characteristics from those that form via disk instability. Disk-instability objects are typically thought to have higher entropies, larger radii, and (generally) higher effective temperatures than core-accretion objects. In this paper, we provide a large set of models exploring the observational consequences of high-entropy (hot) and low-entropy (cold) initial conditions, in the hope that this will ultimately help to distinguish between different physical mechanisms of planet formation. However, the exact entropies and radii of newly formed planets due to these two modes of formation cannot, at present, be precisely predicted. It is possible that the distribution of properties of core-accretion-formed planets and the distribution of properties of disk-instability-formed planets overlap. We, therefore, introduce a broad range of "warm-start" gas-giant planet models. Between the hottest and the coldest models that we consider, differences in radii, temperatures, luminosities, and spectra persist for only a few million to a few tens of millions of years for planets that are a few times Jupiter's mass or less. For planets that are ~five times Jupiter's mass or more, significant differences between hottest-start and coldest-start models persist for on the order of 100 Myr. We find that out of the standard infrared bands (J, H, K, L', M, N) the K and H bands are the most diagnostic of the initial conditions. A hottest-start model can be from ~4.5 mag brighter (at Jupiter's mass) to ~9 mag brighter (at 10 times Jupiter's mass) than a coldest-start model in the first few million years. In more massive objects, these large differences in luminosity and spectrum persist for much longer than in less massive objects. Finally, we consider the influence of atmospheric conditions on spectra, and find that the presence or absence of clouds, and the metallicity of an atmosphere, can affect an object's apparent brightness in different bands by up to several magnitudes.
- ID:
- ivo://CDS.VizieR/J/A+AS/103/67
- Title:
- Evolutionary sequences with MC metallicities
- Short Name:
- J/A+AS/103/67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Tables of evolutionary sequences for massive stars with metallicities Z=0.002 and Z=0.01 in the mass range 9 to 40 M_{sun}_ and mass ratios 0.9 and 0.6 are presented. The orbital periods are chosen such that mass transfer according to case B occurs, i.e. mass exchange after core hydrogen exhaustion, during semi-detached and contact phases. The evolutionary code used by de Loore & De Greve (1992A&AS...94..453D) for galactic massive close binaries was updated, i.e. new thermodynamic quantities and new opacities were installed. The evolution of both components is followed simultaneously. Stellar wind mass loss rates during the OB phase are scaled according to the radiatively driven wind theory. Wolf-Rayet mass loss rates are assumed to be independent of metallicity. The models presented here may be used to interpret and evaluate the observations of Wolf-Rayet stars and massive binary X-ray sources in the Small and Large Magellanic Clouds.
