Small planets on close-in orbits tend to exhibit envelope mass fractions of either effectively zero or up to a few percent depending on their size and orbital period. Models of thermally-driven ...atmospheric mass loss and of terrestrial planet formation in a gas-poor environment make distinct predictions regarding the location of this rocky/non-rocky transition in period-radius space. Here we present the confirmation of TOI-1235 b (\(P=3.44\) days, \(r_p=1.738^{+0.087}_{-0.076}\) R\(_{\oplus}\)), a planet whose size and period are intermediate between the competing model predictions thus making the system an important test case for emergence models of the rocky/non-rocky transition around early M dwarfs (\(R_s=0.630\pm 0.015\) R\(_{\odot}\), \(M_s=0.640\pm 0.016\) M\(_{\odot}\)). We confirm the TESS planet discovery using reconnaissance spectroscopy, ground-based photometry, high-resolution imaging, and a set of 38 precise radial-velocities from HARPS-N and HIRES. We measure a planet mass of \(6.91^{+0.75}_{-0.85}\) M\(_{\oplus}\), which implies an iron core mass fraction of \(20^{+15}_{-12}\)% in the absence of a gaseous envelope. The bulk composition of TOI-1235 b is therefore consistent with being Earth-like and we constrain a H/He envelope mass fraction to be \(<0.5\)% at 90% confidence. Our results are consistent with model predictions from thermally-driven atmospheric mass loss but not with gas-poor formation, suggesting that the former class of processes remain efficient at sculpting close-in planets around early M dwarfs. Our RV analysis also reveals a strong periodicity close to the first harmonic of the photometrically-determined stellar rotation period that we treat as stellar activity, despite other lines of evidence favoring a planetary origin (\(P=21.8^{+0.9}_{-0.8}\) days, \(m_p\sin{i}=13.0^{+3.8}_{-5.3}\) M\(_{\oplus}\)) that cannot be firmly ruled out by our data.
We report the discovery of two transiting exoplanets from the WASP survey, WASP-150b and WASP-176b. WASP-150b is an eccentric (\(e\) = 0.38) hot Jupiter on a 5.6 day orbit around a \(V\) = 12.03, F8 ...main-sequence host. The host star has a mass and radius of 1.4 \(\rm M_{\odot}\) and 1.7 \(\rm R_{\odot}\) respectively. WASP-150b has a mass and radius of 8.5 \(\rm M_J\) and 1.1 \(\rm R_J\), leading to a large planetary bulk density of 6.4 \(\rm \rho_J\). WASP-150b is found to be \(\sim3\) Gyr old, well below its circularisation timescale, supporting the eccentric nature of the planet. WASP-176b is a hot Jupiter planet on a 3.9 day orbit around a \(V\) = 12.01, F9 sub-giant host. The host star has a mass and radius of 1.3 \(\rm M_{\odot}\) and 1.9 \(\rm R_{\odot}\). WASP-176b has a mass and radius of 0.86 \(\rm M_J\) and 1.5 \(\rm R_J\) respectively, leading to a planetary bulk density of 0.23 \(\rm \rho_J\).
K2-291 (EPIC 247418783) is a solar-type star with a radius of R_star = 0.899 \(\pm\) 0.034 R_sun and mass of M_star=0.934 \(\pm\) 0.038 M_sun. From K2 C13 data, we found one super-Earth planet (R_p = ...1.589+0.095-0.072 R_Earth) transiting this star on a short period orbit (P = 2.225177 +6.6e-5 -6.8e-5 days). We followed this system up with adaptive-optic imaging and spectroscopy to derive stellar parameters, search for stellar companions, and determine a planet mass. From our 75 radial velocity measurements using HIRES on Keck I and HARPS-N on Telescopio Nazionale Galileo, we constrained the mass of EPIC 247418783b to M_p = 6.49 \(\pm\) 1.16 M_Earth. We found it necessary to model correlated stellar activity radial velocity signals with a Gaussian process in order to more accurately model the effect of stellar noise on our data; the addition of the Gaussian process also improved the precision of this mass measurement. With a bulk density of 8.84+2.50-2.03 g cm-3, the planet is consistent with an Earth-like rock/iron composition and no substantial gaseous envelope. Such an envelope, if it existed in the past, was likely eroded away by photo-evaporation during the first billion years of the star's lifetime.
Measures of exoplanet bulk densities indicate that small exoplanets with radius less than 3 Earth radii (\(R_\oplus\)) range from low-density sub-Neptunes containing volatile elements to higher ...density rocky planets with Earth-like or iron-rich (Mercury-like) compositions. Such astonishing diversity in observed small exoplanet compositions may be the product of different initial conditions of the planet-formation process and/or different evolutionary paths that altered the planetary properties after formation. Planet evolution may be especially affected by either photoevaporative mass loss induced by high stellar X-ray and extreme ultraviolet (XUV) flux or giant impacts. Although there is some evidence for the former, there are no unambiguous findings so far about the occurrence of giant impacts in an exoplanet system. Here, we characterize the two innermost planets of the compact and near-resonant system Kepler-107. We show that they have nearly identical radii (about \(1.5-1.6~R_\oplus\)), but the outer planet Kepler-107c is more than twice as dense (about \(12.6~\rm g\,cm^{-3}\)) as the innermost Kepler-107b (about \(5.3~\rm g\,cm^{-3}\)). In consequence, Kepler-107c must have a larger iron core fraction than Kepler-107b. This imbalance cannot be explained by the stellar XUV irradiation, which would conversely make the more-irradiated and less-massive planet Kepler-107b denser than Kepler-107c. Instead, the dissimilar densities are consistent with a giant impact event on Kepler-107c that would have stripped off part of its silicate mantle. This hypothesis is supported by theoretical predictions from collisional mantle stripping, which match the mass and radius of Kepler-107c.
Ultra-short period (USP) planets are a class of low mass planets with periods shorter than one day. Their origin is still unknown, with photo-evaporation of mini-Neptunes and in-situ formation being ...the most credited hypotheses. Formation scenarios differ radically in the predicted composition of USP planets, it is therefore extremely important to increase the still limited sample of USP planets with precise and accurate mass and density measurements. We report here the characterization of an USP planet with a period of 0.28 days around K2-141 (EPIC 246393474), and the validation of an outer planet with a period of 7.7 days in a grazing transit configuration. We derived the radii of the planets from the K2 light curve and used high-precision radial velocities gathered with the HARPS-N spectrograph for mass measurements. For K2-141b we thus inferred a radius of \(1.51\pm0.05~R_\oplus\) and a mass of \(5.08\pm0.41~M_\oplus\), consistent with a rocky composition and lack of a thick atmosphere. K2-141c is likely a Neptune-like planet, although due to the grazing transits and the non-detection in the RV dataset, we were not able to put a strong constraint on its density. We also report the detection of secondary eclipses and phase curve variations for K2-141b. The phase variation can be modeled either by a planet with a geometric albedo of \(0.30 \pm 0.06\) in the Kepler bandpass, or by thermal emission from the surface of the planet at \(\sim\)3000K. Only follow-up observations at longer wavelengths will allow us to distinguish between these two scenarios.
In the context of the ESA M5 (medium mission) call we proposed a new satellite mission, Theia, based on relative astrometry and extreme precision to study the motion of very faint objects in the ...Universe. Theia is primarily designed to study the local dark matter properties, the existence of Earth-like exoplanets in our nearest star systems and the physics of compact objects. Furthermore, about 15 \(\%\) of the mission time was dedicated to an open observatory for the wider community to propose complementary science cases. With its unique metrology system and "point and stare" strategy, Theia's precision would have reached the sub micro-arcsecond level. This is about 1000 times better than ESA/Gaia's accuracy for the brightest objects and represents a factor 10-30 improvement for the faintest stars (depending on the exact observational program). In the version submitted to ESA, we proposed an optical (350-1000nm) on-axis TMA telescope. Due to ESA Technology readiness level, the camera's focal plane would have been made of CCD detectors but we anticipated an upgrade with CMOS detectors. Photometric measurements would have been performed during slew time and stabilisation phases needed for reaching the required astrometric precision.
Substitution of calcium carbonate for aluminum hydroxide in patients on dialysis: effects on acidosis, parathyroid function, and calcemia. We studied the effects of substituting CaCO3 for ...aluminum-containing gels on metabolic acidosis and on the response of the parathyroid glands in 11 patients treated with chronic hemodialysis. The 8 men and 3 women were clinically stable, were known to be compliant, and had no clinical evidence of aluminum overload; they were not receiving vitamin D supplements; and they had been on dialysis for an average of 65.6 months (range: 13-188 months). After 3 weeks of CaCO3 administration plasma phosphate concentration remained well controlled, and plasma calcium concentration increased from 9.2 +/- 0.2 (2.3 +/- 0.1 mmol/l) to 10.1 +/- 0.2 mg/dl (2.5 +/- 0.1 mmol/l). Predialysis plasma bicarbonate concentration increased from 19.7 +/- 0.6 to 21.9 +/- 0.6 mmol/l. Plasma aluminum concentration decreased from 78.7 +/- 12.5 to 48.5 +/- 3.9 micrograms/l. Plasma PTH level increased from 2.0 +/- 0.7 to 3.3 +/- 0.8 ng/ml despite the concurrent increase in plasma calcium levels. All values returned to control levels following discontinuation of CaCO3 and resumption of aluminum gels. We conclude: (1) In addition to controlling hyperphosphatemia and increasing plasma calcium concentration, CaCO3 ameliorates metabolic acidosis. (2) Avoidance of oral aluminum intake is followed by prompt lowering of plasma aluminum levels. (3) PTH levels paradoxically increase despite the increment in plasma calcium concentration. The hypercalcemia seen with CaCO3 administration may be due, in part, to transient parathyroid hypersecretion that develops when aluminum administration is discontinued.
