- ID:
- ivo://CDS.VizieR/J/A+A/546/A5
- Title:
- eps CrB radial velocity curve
- Short Name:
- J/A+A/546/A5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our aim is to search for and study the origin of the low-amplitude and long-periodic radial velocity (RV) variations in K giants. We present high-resolution RV measurements of K2 giant epsilon CrB from February 2005 to January 2012 using the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) at the Bohyunsan Optical Astronomy Observatory (BOAO). We find that the RV measurements for epsilon CrB exhibit a periodic variation of 417.9+/-0.5days with a semi-amplitude of 129.4+/-2.0m/s. There is no correlation between RV measurements and chromospheric activity in the Ca II H region, the Hipparcos photometry, or bisector velocity span. Keplerian motion is the most likely explanation, with the RV variations arising from an orbital motion. Assuming a possible stellar mass of 1.7+/-0.1M_{sun}_ for epsilon CrB, we obtain a minimum mass for the planetary companion of 6.7+/-0.3M_Jup_ with an orbital semi-major axis of 1.3AU and eccentricity of 0.11. We also discuss the implications of our observations for stellar metallicity versus planet occurrence rate and stellar mass versus planetary mass relations.
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Search Results
- 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/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/485/293
- Title:
- Events of Saturn satellites during 2009 equinox
- Short Name:
- J/A+A/485/293
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Saturnian equinox will occur in 2009; i.e., the Sun (and the Earth, very close to the Sun as seen from Saturn) will be in the equatorial plane of Saturn. Eclipses of the satellites by Saturn or mutual eclipses and occultations will occur among the seven first satellites orbiting in the Saturnian equatorial plane. This paper provides predictions of these events, along with information useful for observing them. Such events are uncommon, since they only occur every 15 years during the Saturnian equinox. The present dynamical models of motion of the Saturnian satellites include many effects on their motion. One needs accurate observations, such as mutual events, to determine all the relevant parameters.
- 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+A/557/A70
- Title:
- Evolved planet hosts - stellar parameters
- Short Name:
- J/A+A/557/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is still being debated whether the well-known metallicity - giant planet correlation for dwarf stars is also valid for giant stars. For this reason, having precise metallicities is very important. Precise stellar parameters are also crucial to planetary research for several other reasons. Different methods can provide different results that lead to discrepancies in the analysis of planet hosts. To study the impact of different analyses on the metallicity scale for evolved stars, we compare different iron line lists to use in the atmospheric parameter derivation of evolved stars. Therefore, we use a sample of 71 evolved stars with planets. With these new homogeneous parameters, we revisit the metallicity - giant planet connection for evolved stars. A spectroscopic analysis based on Kurucz models in local thermodynamic equilibrium (LTE) was performed through the MOOG code to derive the atmospheric parameters. Two different iron line list sets were used, one built for cool FGK stars in general, and the other for giant FGK stars. Masses were calculated through isochrone fitting, using the Padova models. Kolmogorov-Smirnov tests (K-S tests) were then performed on the metallicity distributions of various different samples of evolved stars and red giants. All parameters compare well using a line list set, designed specifically for cool and solar-like stars to provide more accurate temperatures. All parameters derived with this line list set are preferred and are thus adopted for future analysis. We find that evolved planet hosts are more metal-poor than dwarf stars with giant planets. However, a bias in giant stellar samples that are searched for planets is present. Because of a colour cut-off, metal-rich low-gravity stars are left out of the samples, making it hard to compare dwarf stars with giant stars. Furthermore, no metallicity enhancement is found for red giants with planets (logg<3.0dex) with respect to red giants without planets.
- ID:
- ivo://CDS.VizieR/J/A+A/586/A94
- Title:
- Exoplanetary parameters for 18 bright stars
- Short Name:
- J/A+A/586/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the interferometric angular diameters of 18 bright stars: HD3651 , HD9826, HD19994, HD75732, HD167042, HD170693, HD173416, HD185395, HD190360, HD217014, HD221345, HD1367, HD1671, HD154633, HD161178, HD161151, HD209369, HD218560. The first 11 host exoplanets (except HD185395). We combined these angular diameters {theta}_LD_ with the stellar distances to estimate the stellar radii. We perform SED fitting of the photometry to derive the stars bolometric flux Fbol with and without stellar extinction Av. We then give the effective temperature Teff_SED_ and angular diameter {theta}_SED_ from this SED fit, considering fixed Av, metallicity [Fe/H] and gravity log(g). Then, taking into account the stellar extinction, we derived from the bolometric flux and the measured angular diameters the effective temperature and luminosity to place the stars on the H-R diagram. We then used the PARSEC models to derive the best fit ages and masses of the stars, with error bars derived from Monte Carlo calculations. Typically, for main sequence stars, two distinct sets of solutions appear (an old and a young age). For stars that host known exoplanets, we also derive the exoplanets parameters considering the two different solutions (old and young): semi-major axis, planetary minimum mass and habitable zone of the host stars. Finally, we give the true mass, radius and density of the transiting exoplanet 55 Cnc e using the inteferometric radius and photometry.
- ID:
- ivo://CDS.VizieR/J/MNRAS/463/1780
- Title:
- Exoplanet candidates in Praesepe (M 44)
- Short Name:
- J/MNRAS/463/1780
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work we keep pushing K2 data to a high photometric precision, close to that of the Kepler main mission, using a PSF-based, neighbour-subtraction technique, which also overcome the dilution effects in crowded environments. We analyse the open cluster M 44 (NGC 2632), observed during the K2 Campaign 5, and extract light curves of stars imaged on module 14, where most of the cluster lies. We present two candidate exoplanets hosted by cluster members and five by field stars. As a by-product of our investigation, we find 1680 eclipsing binaries and variable stars, 1071 of which are new discoveries. Among them, we report the presence of a heartbeat binary star. Together with this work, we release to the community a catalogue with the variable stars and the candidate exoplanets found, as well as all our raw and detrended light curves.