We analyze space-based time-series photometry of Sun-like stars, mostly in the Pleiades, but also field stars and the Sun itself. We focus on timescales between roughly 1 hr and 1 day. In the corresponding frequency band these stars display brightness fluctuations with a decreasing power-law continuous spectrum. K2 and Kepler observations show that the rms flicker due to this mid-frequency continuum (MFC) can reach almost 1%, approaching the modulation amplitude from active regions. The MFC amplitude varies by a factor up to 40 among Pleiades members with similar T eff, depending mainly on the stellar Rossby number Ro. For Ro ≤ 0.04, the mean amplitude is roughly constant at about 0.4%; at larger Ro the amplitude decreases rapidly, shrinking by about two orders of magnitude for Ro ≃ 1. Among stars, the MFC amplitude correlates poorly with that of modulation from rotating active regions. Among field stars observed for 3 yr by Kepler, the quarterly average modulation amplitudes from active regions are much more time variable than the quarterly MFC amplitudes. We argue that the process causing the MFC is largely magnetic in nature and that its power-law spectrum comes from magnetic processes distinct from the star’s global dynamo, with shorter timescales. By analogy with solar phenomena, we hypothesize that the MFC arises from a (sometimes energetic) variant of the solar magnetic network, perhaps combined with rotation-related changes in the morphology of supergranules.

Asteroseismology probes the internal structures of stars by using their natural pulsation frequencies1. It relies on identifying sequences of pulsation modes that can be compared with theoretical models, which has been done successfully for many classes of pulsators, including low-mass solar-type stars2, red giants3, high-mass stars4 and white dwarfs5. However, a large group of pulsating stars of intermediate mass—the so-called δ Scuti stars—have rich pulsation spectra for which systematic mode identification has not hitherto been possible6,7. This arises because only a seemingly random subset of possible modes are excited and because rapid rotation tends to spoil regular patterns8–10. Here we report the detection of remarkably regular sequences of high-frequency pulsation modes in 60 intermediate-mass main-sequence stars, which enables definitive mode identification. The space motions of some of these stars indicate that they are members of known associations of young stars, as confirmed by modelling of their pulsation spectra. The pulsation spectra of intermediate-mass stars (so-called δ Scuti stars) have been challenging to analyse, but new observations of 60 such stars reveal remarkably regular sequences of high-frequency pulsation modes.

We present the discovery of two new 10 day period giant planets from the Transiting Exoplanet Survey Satellite mission, whose masses were precisely determined using a wide diversity of ground-based facilities. TOI-481 b and TOI-892 b have similar radii (0.99 ± 0.01 RJ and 1.07 ± 0.02 RJ , respectively), and orbital periods (10.3311 days and 10.6266 days, respectively), but significantly different masses (1.53 ± 0.03 MJ versus 0.95 ± 0.07 MJ , respectively). Both planets orbit metal-rich stars ( [Fe/H] = +0.26±0.05 dex and [Fe/H] = +0.24±0.05 for TOI-481 and TOI-892, respectively) but at different evolutionary stages. TOI-481 is a M⋆ = 1.14 ± 0.02 M⊙ , R⋆ = 1.66 ± 0.02 R⊙ G-type star ( Teff = 5735±72 K), that with an age of 6.7 Gyr, is in the turn-off point of the main sequence. TOI-892 on the other hand, is a F-type dwarf star ( Teff = 6261±80 K), which has a mass of M⋆ = 1.28 ± 0.03 M⊙ and a radius of R⋆ = 1.39 ± 0.02 R⊙ . TOI-481 b and TOI-892 b join the scarcely populated region of transiting gas giants with orbital periods longer than 10 days, which is important to constrain theories of the formation and structure of hot Jupiters.

We report a spectroscopic orbit with period P = 3.52433 ± 0.00027 days for the planetary companion that transits the solar-type star HD 209458. For the metallicity, mass, and radius of the star, we derive [Fe/H] = 0.00 ± 0.02, M* = 1.1 ± 0.1 M☉, and R* = 1.2 ± 0.1 R☉. This is based on a new analysis of the iron lines in our HIRES template spectrum and also on the absolute magnitude, effective temperature, and color of the star, and it uses isochrones from four different sets of stellar evolution models. Using these values for the stellar parameters, we reanalyze the transit data and derive an orbital inclination of i = 86fdg1 ± 1fdg6. For the planet, we derive a mass of Mp = 0.69 ± 0.05 MJup, a radius of Rp = 1.40 ± 0.17 RJup, and a density of ρ = 0.31 ± 0.07 g cm−3. MAZEH, Tsevi, et al. The Spectroscopic Orbit of the Planetary Companion Transiting HD 209458. Astrophysical Journal Letters, 2000, vol. 532, no. 1, p. L55-L58 DOI : 10.1086/312558

Transiting Exoplanet Survey Satellite (TESS) observations have revealed a compact multi-planet system around the sixth-magnitude star HR 858 (TIC 178155732, TOI 396), located 32 parsecs away. Three planets, each about twice the size of Earth, transit this slightly-evolved, late F-type star, which is also a member of a visual binary. Two of the planets may be in mean motion resonance. We analyze the TESS observations, using novel methods to model and remove instrumental systematic errors, and combine these data with follow-up observations taken from a suite of ground-based telescopes to characterize the planetary system. The HR 858 planets are enticing targets for precise radial velocity observations, secondary eclipse spectroscopy, and measurements of the Rossiter-McLaughlin effect.

We report the first confirmation of a hot Jupiter discovered by the Transiting Exoplanet Survey Satellite (TESS) mission: HD 202772A b. The transit signal was detected in the data from TESS Sector 1, and was confirmed to be of planetary origin through radial-velocity measurements. HD 202772A b is orbiting a mildly evolved star with a period of 3.3 days. With an apparent magnitude of V = 8.3, the star is among the brightest known to host a hot Jupiter. Based on the 27days of TESS photometry, and radial velocity data from the CHIRON and HARPS spectrographs, the planet has a mass of 1.008+/-0.074 M_J and radius of 1.562+/-0.053 R_J , making it an inflated gas giant. HD 202772A b is a rare example of a transiting hot Jupiter around a quickly evolving star. It is also one of the most strongly irradiated hot Jupiters currently known.

The future of exoplanet science is bright, as Transiting Exoplanet Survey Satellite (TESS) once again demonstrates with the discovery of its longest-period confirmed planet to date. We hereby present HD 21749b (TOI 186.01), a sub-Neptune in a 36 day orbit around a bright (V = 8.1) nearby (16 pc) K4.5 dwarf. TESS measures HD 21749b to be R⊕, and combined archival and follow-up precision radial velocity data put the mass of the planet at M⊕. HD 21749b contributes to the TESS Level 1 Science Requirement of providing 50 transiting planets smaller than 4 R⊕ with measured masses. Furthermore, we report the discovery of HD 21749c (TOI 186.02), the first Earth-sized ( ) planet from TESS. The HD 21749 system is a prime target for comparative studies of planetary composition and architecture in multi-planet systems.

going. We have done initial examinations of all the data but more detailed analysis is definitely required. a) A comprehensive reduction of the LCOGT data will conducted using standard star field observations that we obtained as part of our campaign – this should provide a larger improved set of comparison stars and allow calibration of the Sloan u filter data. This would then provide 3 colors for grain modeling. b) Improved binning and treatment of spectral overlap will enable better NUV/optical SED fitting from the STIS and COS spectra. This fitting will include the photometric color-magnitude behavior as a constraint. c) The COS FUV spectra show both emission features that are mildly variable and others (particularly molecular features) that are constant. By studying which emission vary and which do not, we shall localize the emissions from the stellar surface and those from the extensive unobscured inner disk. d) Changes in our extensive set of H alpha profiles will be correlated with the optical photometric variability (see Walter et al. poster) UV and Optical Variability of the Young Star T Cha Produced by Inner Disk Obscuration

Las Cumbres Observatory Global Telescope Network (LCOGT) has built the Network of Robotic Echelle Spectrographs (NRES), consisting of four identical, high-resolution optical spectrographs, each fiber-fed simultaneously by up to two 1-meter telescopes and a calibration source. Two units have been installed and are currently executing scientific observations. A third unit has been installed and is presently in commissioning. A fourth unit has been shipped to site and will be installed in mid 2018. Operating on four separate continents in both the Northern and Southern hemispheres, these instruments comprise a globally-distributed, autonomous spectrograph facility for stellar classification and high-precision radial velocity of bright stars. Simulations suggest we will achieve long-term radial velocity precision of 3 m/s in less than an hour for stars with V < 12. Radial velocity precision of 75 m/s has already been demonstrated with our automatic data-processing pipeline across multiple sites. Work is ongoing to improve several NRES system components including telescope control (robotic source acquisition in particular) and the data-processing pipeline. In this document we briefly overview the NRES design, its purpose and goals, results achieved to date in the field, and the ongoing development effort to improve instrument performance.

We outline the important role that ground-based, Doppler monitoring of exoplanetary systems will play in advancing our theories of planet formation and dynamical evolution. A census of planetary systems requires a well designed survey to be executed over the course of a decade or longer. A coordinated survey to monitor several thousand targets each at ~1000 epochs (~3-5 million new observations) will require roughly 40 dedicated spectrographs. We advocate for improvements in data management, data sharing, analysis techniques, and software testing, as well as possible changes to the funding structures for exoplanet science.

We present an analysis of a slightly eccentric ( e = 0.05), partially eclipsing, long-period ( P = 69.73 days) main-sequence binary system (WOCS 12009, Sanders 1247) in the benchmark old open cluster M67. Using Kepler K2 and ground-based photometry, along with a large set of new and reanalyzed spectra, we derived highly precise masses (1.111 ± 0.015 and 0.748 ± 0.005 M ⊙ ) and radii (1.071 ± 0.008 ± 0.003 and 0.713 ± 0.019 ± 0.026 R ⊙ , with statistical and systematic error estimates) for the stars. The radius of the secondary star is in agreement with theory. The primary, however, is approximately 15% smaller than reasonable isochrones for the cluster predict. Our best explanation is that the primary star was produced from the merger of two stars, as this can also account for the nondetection of photospheric lithium and its higher temperature relative to other cluster main-sequence stars at the same V magnitude. To understand the dynamical characteristics (low measured rotational line broadening of the primary star and low eccentricity of the current binary orbit), we believe that the most probable (but not the only) explanation is the tidal evolution of a close binary within a primordial triple system (possibly after a period of Kozai–Lidov oscillations), leading to merger approximately 1 Gyr ago. This star appears to be a future blue straggler that is being revealed as the cluster ages and the most massive main-sequence stars die out.

The Transiting Exoplanet Survey Satellite (TESS) will search for planets transiting bright and nearby stars. TESS has been selected by NASA for launch in 2017 as an Astrophysics Explorer mission. The spacecraft will be placed into a highly elliptical 13.7-day orbit around the Earth. During its two-year mission, TESS will employ four wide-field optical CCD cameras to monitor at least 200,000 main-sequence dwarf stars with I = 4-13 for temporary drops in brightness caused by planetary transits. Each star will be observed for an interval ranging from one month to one year, depending mainly on the star's ecliptic latitude. The longest observing intervals will be for stars near the ecliptic poles, which are the optimal locations for follow-up observations with the James Webb Space Telescope. Brightness measurements of preselected target stars will be recorded every 2 min, and full frame images will be recorded every 30 min. TESS stars will be 10-100 times brighter than those surveyed by the pioneering Kepler mission. This will make TESS planets easier to characterize with follow-up observations. TESS is expected to find more than a thousand planets smaller than Neptune, including dozens that are comparable in size to the Earth. Public data releases will occur every four months, inviting immediate community-wide efforts to study the new planets. The TESS legacy will be a catalog of the nearest and brightest stars hosting transiting planets, which will endure as highly favorable targets for detailed investigations.

NASA's Kepler mission has provided several thousand transiting planet candidates during the 4 yr of its nominal mission, yet only a small subset of these candidates have been confirmed as true planets. Therefore, the most fundamental question about these candidates is the fraction of bona fide planets. Estimating the rate of false positives of the overall Kepler sample is necessary to derive the planet occurrence rate. We present the results from two large observational campaigns that were conducted with the Spitzer Space Telescope during the the Kepler mission. These observations are dedicated to estimating the false positive rate (FPR) among the Kepler candidates. We select a sub-sample of 51 candidates, spanning wide ranges in stellar, orbital, and planetary parameter space, and we observe their transits with Spitzer at 4.5 μm. We use these observations to measures the candidate's transit depths and infrared magnitudes. An authentic planet produces an achromatic transit depth (neglecting the modest effect of limb darkening). Conversely a bandpass-dependent depth alerts us to the potential presence of a blending star that could be the source of the observed eclipse: a false positive scenario. For most of the candidates (85%), the transit depths measured with Kepler are consistent with the transit depths measured with Spitzer as expected for planetary objects, while we find that the most discrepant measurements are due to the presence of unresolved stars that dilute the photometry. The Spitzer constraints on their own yield FPRs between 5% and depending on the Kepler Objects of Interest. By considering the population of the Kepler field stars, and by combining follow-up observations (imaging) when available, we find that the overall FPR of our sample is low. The measured upper limit on the FPR of our sample is 8.8% at a confidence level of 3σ. This observational result, which uses the achromatic property of planetary transit signals that is not investigated by the Kepler observations, provides an independent indication that Kepler's FPR is low.

National Aeronautics and Space Administration (Kepler Participating Scientist Program NNX12AC76G)

Las Cumbres Observatory Global Network (LCOGT) is building the Network of Robotic Echelle Spectrographs (NRES), which will consist of six identical, optical (390 - 860 nm) high-precision spectrographs, each fiber-fed simultaneously by two 1 meter telescopes and a thorium argon calibration source, one at each of our observatory sites in the Northern and Southern hemispheres. Thus, NRES will be a single, globally-distributed, autonomous observing facility using twelve 1-m telescopes. Simulations suggest we will achieve long-term precision of better than 3 m/s in less than an hour for stars brighter than V = 12. We have been fully funded with an NSF MRI grant, and expect our first spectrograph to be deployed in Spring of 2015, with the full network operation of all 6 units beginning in Spring of 2016. We discuss the NRES design, goals, and robotic operation, as well as the early results from our prototype spectrograph.

We report on the masses, sizes, and orbits of the planets orbiting 22 Kepler stars. There are 49 planet candidates around these stars, including 42 detected through transits and 7 revealed by precise Doppler measurements of the host stars. Based on an analysis of the Kepler brightness measurements, along with high-resolution imaging and spectroscopy, Doppler spectroscopy, and (for 11 stars) asteroseismology, we establish low false-positive probabilities (FPPs) for all of the transiting planets (41 of 42 have an FPP under 1%), and we constrain their sizes and masses. Most of the transiting planets are smaller than three times the size of Earth. For 16 planets, the Doppler signal was securely detected, providing a direct measurement of the planet's mass. For the other 26 planets we provide either marginal mass measurements or upper limits to their masses and densities; in many cases we can rule out a rocky composition. We identify six planets with densities above 5 g cm−3, suggesting a mostly rocky interior for them. Indeed, the only planets that are compatible with a purely rocky composition are smaller than ∼2 R⊕. Larger planets evidently contain a larger fraction of low-density material (H, He, and H2O).