- ID:
- ivo://CDS.VizieR/J/ApJ/800/135
- Title:
- HARPS-N radial velocities of KOI-69
- Short Name:
- J/ApJ/800/135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Kepler-93b is a 1.478+/-0.019R_{Earth}_ planet with a 4.7day period around a bright (V=10.2), astroseismically characterized host star with a mass of 0.911+/-0.033M_{sun}_ and a radius of 0.919+/-0.011R_{sun}_. Based on 86 radial velocity observations obtained with the HARPS-N spectrograph on the Telescopio Nazionale Galileo and 32 archival Keck/HIRES observations, we present a precise mass estimate of 4.02+/-0.68M_{Earth}_. The corresponding high density of 6.88+/-1.18g/cm3 is consistent with a rocky composition of primarily iron and magnesium silicate. We compare Kepler-93b to other dense planets with well-constrained parameters and find that between 1 and 6M_{Earth}_, all dense planets including the Earth and Venus are well-described by the same fixed ratio of iron to magnesium silicate. There are as of yet no examples of such planets with masses >6M_{Earth}_. All known planets in this mass regime have lower densities requiring significant fractions of volatiles or H/He gas. We also constrain the mass and period of the outer companion in the Kepler-93 system from the long-term radial velocity trend and archival adaptive optics images. As the sample of dense planets with well-constrained masses and radii continues to grow, we will be able to test whether the fixed compositional model found for the seven dense planets considered in this paper extends to the full population of 1-6M_{Earth}_ planets.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/152/160
- Title:
- HARPS-N radial velocities of KOI-70
- Short Name:
- J/AJ/152/160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Kepler-20 is a solar-type star (V=12.5) hosting a compact system of five transiting planets, all packed within the orbital distance of Mercury in our own solar system. A transition from rocky to gaseous planets with a planetary transition radius of ~1.6R_{Earth}_ has recently been proposed by several articles in the literature. Kepler-20b (R_p_~1.9R_{Earth}_) has a size beyond this transition radius; however, previous mass measurements were not sufficiently precise to allow definite conclusions to be drawn regarding its composition. We present new mass measurements of three of the planets in the Kepler-20 system that are facilitated by 104 radial velocity measurements from the HARPS-N spectrograph and 30 archival Keck/HIRES observations, as well as an updated photometric analysis of the Kepler data and an asteroseismic analysis of the host star (M_*_=0.948+/-0.051M_{Sun}_ and R_*_=0.964+/-0.018R_{Sun}_). Kepler-20b is a 1.868_-0.034_^+0.066^R_{Earth}_ planet in a 3.7day period with a mass of 9.70_-1.44_^+1.41^M_{Earth}_, resulting in a mean density of 8.2_-1.3_^+1.5^g/cm^3^, indicating a rocky composition with an iron-to-silicate ratio consistent with that of the Earth. This makes Kepler-20b the most massive planet with a rocky composition found to date. Furthermore, we report the discovery of an additional non-transiting planet with a minimum mass of 19.96_-3.61_^+3.08^M_{Earth}_ and an orbital period of ~34days in the gap between Kepler-20f (P~11days) and Kepler-20d (P~78days).
- ID:
- ivo://CDS.VizieR/J/AJ/154/237
- Title:
- HARPS-N radial velocities of WASP-47
- Short Name:
- J/AJ/154/237
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present precise radial velocity observations of WASP-47, a star known to host a hot Jupiter, a distant Jovian companion, and, uniquely, two additional transiting planets in short-period orbits: a super-Earth in a ~19 hr orbit, and a Neptune in a ~9 day orbit. We analyze our observations from the HARPS-N spectrograph along with previously published data to measure the most precise planet masses yet for this system. When combined with new stellar parameters and reanalyzed transit photometry, our mass measurements place strong constraints on the compositions of the two small planets. We find that, unlike most other ultra-short-period planets, the inner planet, WASP-47 e, has a mass (6.83+/-0.66 M_{Earth}_) and a radius (1.810+/-0.027 R_{Earth}_) that are inconsistent with an Earth-like composition. Instead, WASP-47 e likely has a volatile-rich envelope surrounding an Earth-like core and mantle. We also perform a dynamical analysis to constrain the orbital inclination of WASP-47 c, the outer Jovian planet. This planet likely orbits close to the plane of the inner three planets, suggesting a quiet dynamical history for the system. Our dynamical constraints also imply that WASP-47 c is much more likely to transit than a geometric calculation would suggest. We calculate a transit probability for WASP-47 c of about 10%, more than an order of magnitude larger than the geometric transit probability of 0.6%.
- ID:
- ivo://CDS.VizieR/J/AJ/155/203
- Title:
- HARPS-N RVs & activity indicators for Kepler-1655
- Short Name:
- J/AJ/155/203
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the confirmation of a small, moderately irradiated (F=155+/-7 F_{Earth}_) Neptune with a substantial gas envelope in a P=11.8728787+/-0.0000085 day orbit about a quiet, Sun-like G0V star Kepler-1655. Based on our analysis of the Kepler light curve, we determined Kepler-1655b's radius to be 2.213+/-0.082 R_{Earth}_. We acquired 95 high-resolution spectra with Telescopio Nazionale Galileo/HARPS-N, enabling us to characterize the host star and determine an accurate mass for Kepler-1655b of 5.0_-2.8_^+3.1^ M_{Earth}_ via Gaussian-process regression. Our mass determination excludes an Earth-like composition with 98% confidence. Kepler-1655b falls on the upper edge of the evaporation valley, in the relatively sparsely occupied transition region between rocky and gas-rich planets. It is therefore part of a population of planets that we should actively seek to characterize further.
- ID:
- ivo://CDS.VizieR/J/ApJ/874/107
- Title:
- HARPS-N solar radial velocities and activity
- Short Name:
- J/ApJ/874/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- State-of-the-art radial-velocity (RV) exoplanet searches are currently limited by RV signals arising from stellar magnetic activity. We analyze solar observations acquired over a 3yr period during the decline of Carrington Cycle 24 to test models of RV variation of Sun-like stars. A purpose-built solar telescope at the High Accuracy Radial-velocity Planet Searcher for the Northern hemisphere (HARPS-N) provides disk-integrated solar spectra, from which we extract RVs and logR'_HK_. The Solar Dynamics Observatory (SDO) provides disk-resolved images of magnetic activity. The Solar Radiation and Climate Experiment (SORCE) provides near-continuous solar photometry, analogous to a Kepler light curve. We verify that the SORCE photometry and HARPS-N logR'_HK_ correlate strongly with the SDO-derived magnetic filling factor, while the HARPS-N RV variations do not. To explain this discrepancy, we test existing models of RV variations. We estimate the contributions of the suppression of convective blueshift and the rotational imbalance due to brightness inhomogeneities to the observed HARPS-N RVs. We investigate the time variation of these contributions over several rotation periods, and how these contributions depend on the area of active regions. We find that magnetic active regions smaller than 60Mm^2^ do not significantly suppress convective blueshift. Our area-dependent model reduces the amplitude of activity-induced RV variations by a factor of two. The present study highlights the need to identify a proxy that correlates specifically with large, bright magnetic regions on the surfaces of exoplanet-hosting stars.
- ID:
- ivo://CDS.VizieR/J/A+A/489/1255
- Title:
- HARPS observations of eight galactic Cepheids
- Short Name:
- J/A+A/489/1255
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We show that residual {gamma}-velocities (compared to a axisymmetric rotation model of the milky Way) are an intrinsic property of Cepheids. We observed eight galactic Cepheids with the HARPS spectroscope, focusing specifically on 17 spectral lines. For each spectral line of each star, we computed the {gamma}-velocity (resp. {gamma}-asymmetry) as an average value of the interpolated radial velocity (resp. line asymmetry) curve. For each Cepheid in our sample, a linear relation is found between the {gamma}-velocities of the various spectral lines and their corresponding {gamma}-asymmetries, showing that residual {gamma}-velocities stem from the intrinsic properties of Cepheids. We also provide a physical reference to the stellar {gamma}-velocity: it should be zero when the {gamma}-asymmetry is zero. Following this definition, we provide very precise and physically calibrated estimates of the {gamma}-velocities for all stars of our sample.
- ID:
- ivo://CDS.VizieR/J/A+A/453/309
- Title:
- HARPS observations of nine galactic Cepheids
- Short Name:
- J/A+A/453/309
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ratio of pulsation to radial velocity (the projection factor) is currently limiting the accuracy of the Baade-Wesselink method, and in particular of its interferometric version recently applied to several nearby Cepheids. This work aims at establishing a link between the line asymmetry evolution over the Cepheids' pulsation cycles and their projection factor, with the final objective to improve the accuracy of the Baade-Wesselink method for distance determinations. We present HARPS high spectral resolution observations (R=120000) of nine galactic Cepheids: R Tra, S Cru, Y Sgr, beta Dor, zeta Gem, Y Oph, RZ Vel, l Car and RS Pup, having a good period sampling (P=3.39d to P=41.52d). We fit spectral line profiles by an asymmetric bi-Gaussian to derive radial velocity, Full-Width at Half-Maximum in the line (FWHM) and line asymmetry for all stars.
- ID:
- ivo://CDS.VizieR/J/A+A/502/951
- Title:
- HARPS observations of nine galactic Cepheids
- Short Name:
- J/A+A/502/951
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed eight galactic Cepheids with the HARPS spectrograph. For each star, we derive an interpolated cross-correlated radial velocity curve using the HARPS pipeline. Pulsating phases and HARPS radial velocity measurements can be found in Table 1. The cross correlation method is widely used to derive the radial velocity curve of Cepheids when the signal to noise ratio of the spectra is low. However, if it is used with an inac curate projection factor, it might introduce some biases in the Baade-Wesselink (BW) methods of determining the distance of Cepheids. In addition, it might affect the average value of the radial velocity curve (or gamma-velocity) important for Galactic structure studies. See the paper for details and results.
- ID:
- ivo://CDS.VizieR/J/AJ/158/100
- Title:
- HARPS radial velocities for HD 181433
- Short Name:
- J/AJ/158/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed analysis of the orbital stability of the HD 181433 planetary system, finding it to exhibit strong dynamical instability across a wide range of orbital eccentricities, semimajor axes, and mutual inclinations. We also analyze the behavior of an alternative system architecture, proposed by Campanella, and find that it offers greater stability than the original solution, as a result of the planets being trapped in strong mutual resonance. We take advantage of more recent observations to perform a full refit of the system, producing a new planetary solution. The best-fit orbit for HD 181433 d now places the planet at a semimajor axis of 6.60+/-0.22 au, with an eccentricity of 0.469+/-0.013. Extensive simulations of this new system architecture reveal it to be dynamically stable across a broad range of potential orbital parameter space, increasing our confidence that the new solution represents the ground truth of the system. Our work highlights the advantage of performing dynamical simulations of candidate planetary systems in concert with the orbital fitting process, as well as supporting the continuing monitoring of radial velocity planet search targets.
- ID:
- ivo://CDS.VizieR/J/A+A/556/A110
- Title:
- HARPS radial velocities of GJ 163
- Short Name:
- J/A+A/556/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The meter-per-second precision achieved by today velocimeters enables the search for 1-10M_{earth}_ planets in the habitable zone of cool stars. This paper reports on the detection of 3 planets orbiting GJ 163 (HIP19394), a M3 dwarf monitored by our ESO/HARPS search for planets. We made use of the HARPS spectrograph to collect 150 radial velocities of GJ 163 over a period of 8 years. We searched the RV time series for coherent signals and found 5 distinct periodic variabilities.We investigated the stellar activity and casted doubts on the planetary interpretation for 2 signals. Before more data can be acquired we concluded that at least 3 planets are orbiting GJ 163. They have orbital periods of Pb=8.632+/-0.002, Pc=25:63+/-0.03 and Pd=604+/-8 days and minimum masses msini=10.6+/-0.6, 6.8+/-0.9, and 29+/-3, respectively. We hold our interpretations for the 2 additional signals with periods P(e)=19.4 and P(f)=108 days.
