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We report on the detailed characterization of the HD 77946 planetary system. HD 77946 is an F5 (M *  = 1.17 M⊙, R *  = 1.31 R⊙) star, which hosts a transiting planet recently discovered by NASA's Transiting Exoplanet Survey Satellite (TESS), classified as TOI-1778 b. Using TESS photometry, high-resolution spectroscopic data from HARPS-N, and photometry from CHEOPS , we measure the radius and mass from the transit and radial velocity observations, and find that the planet, HD 77946 b, orbits with period P b  =  |$6.527282_{-0.000020}^{+0.000015}$| d, has a mass of M b = 8.38 ± 1.32 M⊕, and a radius of |$R_{\rm b} = 2.705_{-0.081}^{+0.086}$| R⊕. From the combination of mass and radius measurements, and the stellar chemical composition, the planet properties suggest that HD 77946 b is a sub-Neptune with a ∼1  per cent H/He atmosphere. However, a degeneracy still exists between water-world and silicate/iron-hydrogen models, and even though interior structure modelling of this planet favours a sub-Neptune with a H/He layer that makes up a significant fraction of its radius, a water-world composition cannot be ruled out, as with |$T_{\rm eq}~= 1248^{+40}_{-38}~$| K, water may be in a supercritical state. The characterization of HD 77946 b, adding to the small sample of well-characterized sub-Neptunes, is an important step forwards on our journey to understanding planetary formation and evolution pathways. Furthermore, HD 77946 b has one of the highest transmission spectroscopic metrics for small planets orbiting hot stars, thus transmission spectroscopy of this key planet could prove vital for constraining the compositional confusion that currently surrounds small exoplanets. [ABSTRACT FROM AUTHOR]

We present the characterization of an inner mini-Neptune in a 9.2292005 ± 0.0000063 d orbit and an outer mono-transiting sub-Saturn planet in a 95.50 |$^{+0.36}_{-0.25}$| d orbit around the moderately active, bright (mv  = 8.9 mag) K5V star TOI-2134. Based on our analysis of five sectors of TESS data, we determine the radii of TOI-2134b and c to be 2.69 ± 0.16 R⊕ for the inner planet and 7.27 ± 0.42 R⊕ for the outer one. We acquired 111 radial-velocity (RV) spectra with HARPS-N and 108 RV spectra with SOPHIE. After careful periodogram analysis, we derive masses for both planets via Gaussian Process regression: 9.13 |$^{+0.78}_{-0.76}$| M⊕ for TOI-2134b and 41.89 |$^{+7.69}_{-7.83}$| M⊕ for TOI-2134c. We analysed the photometric and RV data first separately, then jointly. The inner planet is a mini-Neptune with density consistent with either a water-world or a rocky core planet with a low-mass H/He envelope. The outer planet has a bulk density similar to Saturn's. The outer planet is derived to have a significant eccentricity of 0.67 |$^{+0.05}_{-0.06}$| from a combination of photometry and RVs. We compute the irradiation of TOI-2134c as 1.45 ± 0.10 times the bolometric flux received by Earth, positioning it for part of its orbit in the habitable zone of its system. We recommend further RV observations to fully constrain the orbit of TOI-2134c. With an expected Rossiter–McLaughlin (RM) effect amplitude of 7.2 ± 1.3 |$\rm m\, s^{-1}$|⁠ , we recommend TOI-2134c for follow-up RM analysis to study the spin–orbit architecture of the system. We calculate the Transmission Spectroscopy Metric, and both planets are suitable for bright-mode Near Infrared Camera (NIRCam) atmospheric characterization. [ABSTRACT FROM AUTHOR]

This paper reports on the detailed characterization of the K2-111 planetary system with K2 , WASP, and ASAS-SN photometry, as well as high-resolution spectroscopic data from HARPS-N and ESPRESSO. The host, K2-111, is confirmed to be a mildly evolved (log  g = 4.17), iron-poor ([Fe/H] = −0.46), but alpha-enhanced ([α/Fe]=0.27), chromospherically quiet, very old thick disc G2 star. A global fit, performed by using PyORBIT , shows that the transiting planet, K2-111 b, orbits with a period Pb = 5.3518 ± 0.0004 d and has a planet radius of |$1.82^{+0.11}_{-0.09}$|  R⊕ and a mass of |$5.29^{+0.76}_{-0.77}$|  M⊕, resulting in a bulk density slightly lower than that of the Earth. The stellar chemical composition and the planet properties are consistent with K2-111 b being a terrestrial planet with an iron core mass fraction lower than the Earth. We announce the existence of a second signal in the radial velocity data that we attribute to a non-transiting planet, K2-111 c, with an orbital period of 15.6785 ± 0.0064 d, orbiting in near-3:1 mean motion resonance with the transiting planet, and a minimum planet mass of 11.3 ± 1.1 M⊕. Both planet signals are independently detected in the HARPS-N and ESPRESSO data when fitted separately. There are potentially more planets in this resonant system, but more well-sampled data are required to confirm their presence and physical parameters. [ABSTRACT FROM AUTHOR]

This paper reports on the validation and mass measurement of K2-263 b, a sub-Neptune orbiting a quiet G9V star. Using K2 data from campaigns C5 and C16, we find this planet to have a period of 50.818947 ± 0.000094 d and a radius of 2.41 ± 0.12 R⊕. We followed this system with HARPS-N to obtain 67 precise radial velocities (RVs). A combined fit of the transit and radial velocity data reveals that K2-263 b has a mass of 14.8 ± 3.1 M⊕. Its bulk density (⁠|$5.7_{-1.4}^{+1.6}\, {\rm g}\,\,{\rm cm}^{-3}$|⁠) implies that this planet has a significant envelope of water or other volatiles around a rocky core. K2-263 b likely formed in a similar way as the cores of the four giant planets in our own Solar System, but for some reason, did not accrete much gas. The planetary mass was confirmed by an independent Gaussian process-based fit to both the RVs and the spectroscopic activity indicators. K2-263 b belongs to only a handful of confirmed K2 exoplanets with periods longer than 40 d. It is among the longest periods for a small planet with a precisely determined mass using RVs. [ABSTRACT FROM AUTHOR]

We report the discovery of HATS-2b, the second transiting extrasolar planet detected by the HATSouth survey. HATS-2b is moving on a circular orbit around a V = 13:6 mag, K-type dwarf star (GSC 6665-00236), at a separation of 0:0230 ± 0:0003 AU and with a period of 1:3541 days. The planetary parameters have been robustly determined using a simultaneous fit of the HATSouth, MPG/ESO 2.2m/GROND, Faulkes Telescope South/Spectral transit photometry, and MPG/ESO 2.2m/FEROS, Euler 1.2m/CORALIE, AAT 3.9m/CYCLOPS radial-velocity measurements. HATS-2b has a mass of 1:37 ± 0:16 MJ, a radius of 1:14 ± 0:03 RJ, and an equilibrium temperature of 1567 ± 30 K. The host star has a mass of 0:88 ± 0:04 M☉ and a radius of 0:89 ± 0:02 R☉, and it shows starspot activity. We characterized the stellar activity by analyzing two photometric follow-up transit light curves taken with the GROND instrument, both obtained simultaneously in four optical bands (covering the wavelength range of 3860-9520 Å). The two light curves contain anomalies compatible with starspots on the photosphere of the host star along the same transit chord. [ABSTRACT FROM AUTHOR]

Aims. We announce the discovery of two new transiting planets, and provide their accurate initial characterization. Methods. First identified from the HATNet wide-field photometric survey, these candidate transiting planets were then followed-up with a variety of photometric observations. Determining the planetary nature of the objects and characterizing the parameters of the systems were mainly done with the SOPHIE spectrograph at the 1.93m telescope at OHP and the TRES spectrograph at the 1.5m telescope at FLWO. Results. HAT-P-42b and HAT-P-43b are typical hot Jupiters on circular orbits around early-G/late-F main sequence host stars, with periods of 4.641878 ± 0.000032 and 3.332687 ± 0.000015 days, masses of 1.044 ± 0.083 and 0.662 ± 0.060 MJ, and radii of 1.280 ± 0.153 and 1.281+0.062 -0.033 RJ, respectively. These discoveries increase the sample of planets with measured mean densities, which are needed to constrain theories of planetary interiors and atmospheres. Moreover, their hosts are relatively bright (V < 13.5), which facilitates further follow-up studies. [ABSTRACT FROM AUTHOR]

From the list of 2321 transiting planet candidates announced by the Kepler Mission, we select seven targets with favorable properties for the capacity to dynamically maintain an exomoon and present a detectable signal. These seven candidates were identified through our automatic target selection (TSA) algorithm and target selection prioritization (TSP) filtering, whereby we excluded systems exhibiting significant time-correlated noise and focused on those with a single transiting planet candidate of radius less than 6 R⊕. We find no compelling evidence for an exomoon around any of the seven Kepler Objects of Interest (KOIs) but constrain the satellite-to-planet mass ratios for each. For four of the seven KOIs, we estimate a 95% upper quantile of MS/MP < 0.04, which given the radii of the candidates, likely probes down to sub-Earth masses.We also derive precise transit times and durations for each candidate and find no evidence for dynamical variations in any of the KOIs. With just a few systems analyzed thus far in the ongoing "Hunt for Exomoons with Kepler" (HEK) project, projections on η... would be premature, but a high frequency of large moons around Super-Earths/Mini-Neptunes would appear to be incommensurable with our results so far. [ABSTRACT FROM AUTHOR]

Two decades ago, empirical evidence concerning the existence and frequency of planets around stars, other than our own, was absent. Since that time, the detection of extrasolar planets from Jupiter-sized to, most recently, Earth-sized worlds has blossomed and we are finally able to shed light on the plurality of Earth-like, habitable planets in the cosmos. Extrasolar moons may also be frequently habitable worlds, but their detection or even systematic pursuit remains lacking in the current literature. Here, we present a description of the first systematic search for extrasolar moons as part of a new observational project called "The Hunt for Exomoons with Kepler" (HEK). The HEK project distills the entire list of known transiting planet candidates found by Kepler (2326 at the time of writing) down to the most promising candidates for hosting a moon. Selected targets are fitted using a multimodal nested sampling algorithm coupled with a planet-with-moon light curve modeling routine. By comparing the Bayesian evidence of a planet-only model to that of a planet-with-moon, the detection process is handled in a Bayesian framework. In the case of null detections, upper limits derived from posteriors marginalized over the entire prior volume will be provided to inform the frequency of large moons around viable planetary hosts, ... . After discussing our methodologies for target selection, modeling, fitting, and vetting, we provide two example analyses. [ABSTRACT FROM AUTHOR]

We report the discovery of HAT-P-25b, a transiting extrasolar planet orbiting the V = 13.19 G5 dwarf star GSC 1788-01237, with a period P = 3.652836 ± 0.000019 days, transit epoch Tc = 2455176.85173 ± 0.00047 (BJD— barycentric Julian dates throughout the paper are calculated from Coordinated Universal Time, UTC), and transit duration 0,1174 ± 0.0017 days. The host star has a mass of 1.01 ± 0.03 Mʘ, radius of 0.96 Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. Rʘ, effective temperature 5500 ± 80 K, and metallicity [Fe/H] = +0.31 ± 0.08. The planetary companion has a mass of 0.567 ± 0.022 Mj and radius of 1.190 Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. Rj yielding a mean density of 0.42 ± 0.07 gcm-3. [ABSTRACT FROM AUTHOR]

We report the discovery of four relatively massive (2-7 MJ) transiting extrasolar planets. HAT-P-20b orbits the moderately bright V = 11.339 K3 dwarf star GSC 1910-00239 on a circular orbit, with a period P = 2.875317 ± 0.000004 days, transit epoch Tc = 2455080.92661 ± 0.00021 (BJDUTC), and transit duration 0.0770 ± 0.0008 days. The host star has a mass of 0.76 ± 0.03 M⊙, radius of 0.69 ± 0.02 R⊙, effective temperature 4595 ± 80 K, and metallicity [Fe/H] = +0.35 ± 0.08. The planetary companion has a mass of 7.246 ± 0.187 MJ and a radius of 0.867 ± 0.033 RJ yielding a mean density of 13.78 ± 1.50 g cm-3. HAT-P-21b orbits the V = 11.685 G3 dwarf star GSC 3013-01229 on an eccentric (e = 0.228 ± 0.016) orbit, with a period P = 4.124481 ± 0.000007 days, transit epoch Tc = 2454996.41312 ± 0.00069, and transit duration 0.1530 ± 0.0027 days. The host star has a mass of 0.95 ± 0.04 M⊙, radius of 1.10 ± 0.08 R⊙, effective temperature 5588 ± 80 K, and metallicity [Fe/H] = +0.01 ± 0.08. The planetary companion has a mass of 4.063 ± 0.161 MJ and a radius of 1.024 ± 0.092 RJ yielding a mean density of Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. HAT-P-21b is a borderline object between the pM and pL class planets, and the transits occur near apastron. HAT-P-22b orbits the bright V = 9.732 G5 dwarf star HD 233731 on a circular orbit, with a period P = 3.212220 ± 0.000009 days, transit epoch Tc = 2454930.22001 ± 0.00025, and transit duration 0.1196 ± 0.0014 days. The host star has a mass of 0.92 ±0.03 M⊙, radius of 1.04 ± 0.04 R⊙, effective temperature 5302 ± 80 K, and metallicity [Fe/H] = +0.24 ± 0.08. The planet has a mass of 2.147 ± 0.061 MJ and a compact radius of 1.080 ± 0.058 RJ yielding a mean density of Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. The host star also harbors an M-dwarf companion at a wide separation. Finally, HAT-P-23b orbits the V = 12.432 G0 dwarf star GSC 1632-01396 on a close to circular orbit, with a period P = 1.212884 ± 0.000002 days, transit epoch Tc = 2454852.26464 ± 0.00018, and transit duration 0.0908 ± 0.0007 days. The host star has a mass of 1.13 ± 0.04 M⊙, radius of 1.20 ± 0.07 R⊙, effective temperature 5905 ± 80 K, and metallicity [Fe/H] = +0.15 ± 0.04. The planetary companion has a mass of 2.090 ± 0.111 MJ and a radius of 1.368 ± 0.090 RJ yielding a mean density of 1.01 ± 0.18 g cm-3. HAT-P-23b is an inflated and massive hot Jupiter on a very short period orbit, and has one of the shortest characteristic infall times (Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed Myr) before it gets engulfed by the star. [ABSTRACT FROM AUTHOR]

We report the discovery of HAT-P-27b, an exoplanet transiting the moderately bright G8 dwarf star GSC 0333-0035 1 (V = 12.214). The orbital period is 3.039586 ± 0.000012 days, the reference epoch of transit is 2455186.01879 ± 0.00054 (BJD), and the transit duration is 0.0705 ± 0.0019 days. The host star with its effective temperature 5300± 90 K is somewhat cooler than the Sun and is more metal-rich with a metallicity of +0.29±0.10. Its mass is 0.94 ± 0.04 M⊙ and radius is 0.90+0.05-0.04R⊙. For the planetary companion we determine a mass of 0.660 ± 0.033 MJ and radius of 1.038+0.077-0.058 RJ. For the 30 known transiting exoplanets between 0.3 MJ and 0.8 MJ, a negative correlation between host star metallicity and planetary radius and an additional dependence of planetary radius on equilibrium temperature are confirmed at a high level of statistical significance. [ABSTRACT FROM AUTHOR]

We know now from radial velocity surveys and transit space missions that planets only a few times more massive than our Earth are frequent around solar-type stars. Fundamental questions about their formation history, physical properties, internal structure, and atmosphere composition are, however, still to be solved. We present here the detection of a system of four low-mass planets around the bright (V = 5.5) and close-by (6.5 pc) star HD 219134. This is the first result of the Rocky Planet Search programme with HARPS-N on the Telescopio Nazionale Galileo in La Palma. The inner planet orbits the star in 3.0935 ± 0.0003 days, on a quasicircular orbit with a semi-major axis of 0.0382 ± 0.0003 AU. Spitzer observations allowed us to detect the transit of the planet in front of the star making HD 219134 b the nearest known transiting planet to date. From the amplitude of the radial velocity variation (2.25 ± 0.22 ms−1 ) and observed depth of the transit (359 ± 38 ppm), the planet mass and radius are estimated to be 4.36 ± 0.44 M⊕ and 1.606 ± 0.086 R⊕, leading to a mean density of 5.76 ± 1.09 g cm−3 , suggesting a rocky composition. One additional planet with minimum-mass of 2.78 ± 0.65 M⊕ moves on a close-in, quasi-circular orbit with a period of 6.767 ± 0.004 days. The third planet in the system has a period of 46.66 ± 0.08 days and a minimum-mass of 8.94 ± 1.13 M⊕, at 0.233 ± 0.002 AU from the star. Its eccentricity is 0.46 ± 0.11. The period of this planet is close to the rotational period of the star estimated from variations of activity indicators (42.3 ± 0.1 days). The planetary origin of the signal is, however, the preferred solution as no indication of variation at the corresponding frequency is observed for activity-sensitive parameters. Finally, a fourth additional longer-period planet of mass of 71 M⊕ orbits the star in 1842 days, on an eccentric orbit (e = 0.34 ± 0.17) at a distance of 2.56 AU., Astronomy