We present the largest sample of flares ever compiled for a single M dwarf, the active M4 star GJ 1243. Over 6100 individual flare events, with energies ranging from 10 super(29) to 10 super(33) erg, ...are found in 11 months of 1 minute cadence data from Kepler. This sample is unique for its completeness and dynamic range. We have developed automated tools for finding flares in short-cadence Kepler light curves, and performed extensive validation and classification of the sample by eye. From this pristine sample of flares we generate a median flare template. This template shows that two exponential cooling phases are present during the white-light flare decay, providing fundamental constraints for models of flare physics. The template is also used as a basis function to decompose complex multi-peaked flares, allowing us to study the energy distribution of these events. Only a small number of flare events are not well fit by our template. We find that complex, multi-peaked flares occur in over 80% of flares with a duration of 50 minutes or greater. Uie underlying distribution of flare durations for events 10 minutes and longer appears to follow a broken power law. Our results support the idea that sympathetic flaring may be responsible for some complex flare events.
ABSTRACT
We report the detection of the full orbital phase curve and occultation of the hot-Jupiter WASP-100b using TESS photometry. The phase curve is isolated by suppressing low-frequency stellar ...and instrumental modes using both a non-parametric harmonic notch filter (phasma) and semi-sector long polynomials. This yields a phase-curve signal of (73 ± 9) ppm amplitude, preferred over a null-model by ΔBIC = 25, indicating very strong evidence for an observed effect. We recover the occultation event with a suite of five temporally localized tools, including Gaussian processes and cosine filtering. This allows us to infer an occultation depth of (100 ± 14) ppm, with an additional ±16 ppm systematic error from the differences between methods. We regress a model including atmospheric reflection, emission, ellipsoidal variations, and Doppler beaming to the combined phase-curve and occultation data. This allows us to infer that WASP-100b has a geometric albedo of $A_g = 0.16^{+0.04}_{-0.03}$ in the TESS bandpass, with a maximum dayside brightness temperature of (2710 ± 100) K and a warm nightside temperature of $(2380^{+170}_{-200})$ K. Additionally, we find evidence that WASP-100b has a high thermal redistribution efficiency, manifesting as a substantial eastward hotspot offset of $(71^{+2}_{-4})^{\circ }$. These results present the first measurement of a thermal phase shift among the phase curves observed by TESS so far, and challenge the predicted efficiency of heat transport in the atmospheres of ultra-hot-Jupiters.
ABSTRACT
We present the discovery of a pair of transiting giant planets using four sectors of TESS photometry. TOI-216 is a 0.87 M⊙ dwarf orbited by two transiters with radii of 8.2 and 11.3 R⊕, and ...periods of 17.01 and 34.57 d, respectively. Anticorrelated TTVs are clearly evident indicating that the transiters orbit the same star and interact via a near 2:1 mean motion resonance. By fitting the TTVs with a dynamical model, we infer masses of $30_{-14}^{+20}$ and $200_{-100}^{+170}$ M⊕, establishing that the objects are planetary in nature and have likely sub-Kronian and Kronian densities. TOI-216 lies close to the southern ecliptic pole and thus will be observed by TESS throughout the first year, providing an opportunity for continuous dynamical monitoring and considerable refinement of the dynamical masses presented here. TOI-216 closely resembles Kepler-9 in architecture, and we hypothesize that in such systems these Saturn analogues failed to fully open a gap and thus migrated far deeper into the system before becoming trapped into resonance, which would imply that future detections of new analogues may also have sub-Jupiter masses.
ABSTRACT Direct imaging of extrasolar planets with future space-based coronagraphic telescopes may provide a means of detecting companion moons at wavelengths where the moon outshines the planet. We ...propose a detection strategy based on the positional variation of the center of light with wavelength, "spectroastrometry." This new application of this technique could be used to detect an exomoon, to determine the exomoon's orbit and the mass of the host exoplanet, and to disentangle the spectra of the planet and moon. We consider two model systems, for which we discuss the requirements for detection of exomoons around nearby stars. We simulate the characterization of an Earth-Moon analog system with spectroastrometry, showing that the orbit, the planet mass, and the spectra of both bodies can be recovered. To enable the detection and characterization of exomoons we recommend that coronagraphic telescopes should extend in wavelength coverage to 3 m, and should be designed with spectroastrometric requirements in mind.
Planetary rotation rate has a significant effect on atmospheric circulation, where the strength of the Coriolis effect in part determines the efficiency of latitudinal heat transport, altering cloud ...distributions, surface temperatures, and precipitation patterns. In this study, we use the ROCKE-3D dynamic ocean general circulation model to study the effects of slow rotations and increased insolations on the "fractional habitability" and silicate weathering rate of an Earth-like world. Defining the fractional habitability fh to be the percentage of a planet's surface that falls in the 0 ≤ T ≤ 100 °C temperature regime, we find a moderate increase in fh with a 10% and 20% increase in insolation and a possible maximum in fh at sidereal day lengths between 8 and 32 times that of the modern Earth. By tracking precipitation and runoff, we further determine that there is a rotational regime centered on a 4 day period in which the silicate weathering rate is maximized and is particularly strongly peaked at higher overall insolations. Because of weathering's integral role in the long-term carbonate-silicate cycle, we suggest that climate stability may be strongly affected by the anticipated rotational evolution of temperate terrestrial-type worlds and should be considered a major factor in their study. In light of our results, we argue that planetary rotation period is an important factor to consider when determining the habitability of terrestrial worlds.
Planetary rotation rate has a significant effect on atmospheric circulation, where the strength of the Coriolis effect in part determines the efficiency of latitudinal heat transport, altering cloud ...distributions, surface temperatures, and precipitation patterns. In this study, we use the ROCKE-3D dynamic ocean general circulation model to study the effects of slow rotations and increased insolations on the "fractional habitability" and silicate weathering rate of an Earth-like world. Defining the fractional habitability f (h) to be the percentage of a planet's surface that falls in the 0 ≤ T ≤ 100 °C temperature regime, we find a moderate increase in f (h) with a 10% and 20% increase in insolation and a possible maximum in f (h) at sidereal day lengths between 8 and 32 times that of the modern Earth. By tracking precipitation and runoff, we further determine that there is a rotational regime centered on a 4 day period in which the silicate weathering rate is maximized and is particularly strongly peaked at higher overall insolations. Because of weathering's integral role in the long-term carbonate–silicate cycle, we suggest that climate stability may be strongly affected by the anticipated rotational evolution of temperate terrestrial-type worlds and should be considered a major factor in their study. In light of our results, we argue that planetary rotation period is an important factor to consider when determining the habitability of terrestrial worlds.
Abstract
Transiting compact multiplanet systems provide many unique opportunities to characterize the planets, including studies of size distributions, mean densities, orbital dynamics, and ...atmospheric compositions. The relatively short orbital periods in these systems ensure that events requiring specific orbital locations of the planets (such as primary transit and secondary eclipse points) occur with high frequency. The orbital motion and associated phase variations of the planets provide a means to constrain the atmospheric compositions through measurement of their albedos. Here we describe the expected phase variations of the TRAPPIST-1 system and times of superior conjunction when the summation of phase effects produce maximum amplitudes. We also describe the infrared flux emitted by the TRAPPIST-1 planets and the influence on the overall phase amplitudes. We further present the results from using the global circulation model
ROCKE-3D
to model the atmospheres of TRAPPIST-1e and TRAPPIST-1f assuming modern Earth and Archean atmospheric compositions. These simulations are used to calculate predicted phase curves for both reflected light and thermal emission components. We discuss the detectability of these signatures and the future prospects for similar studies of phase variations for relatively faint M stars.
We present two state-of-the-art models of the solar system, one corresponding to the present day and one to the Archean Eon 3.5 billion years ago. Each model contains spatial and spectral information ...for the star, the planets, and the interplanetary dust, extending to 50 au from the Sun and covering the wavelength range 0.3-2.5 m. In addition, we created a spectral image cube representative of the astronomical backgrounds that will be seen behind deep observations of extrasolar planetary systems, including galaxies and Milky Way stars. These models are intended as inputs to high-fidelity simulations of direct observations of exoplanetary systems using telescopes equipped with high-contrast capability. They will help improve the realism of observation and instrument parameters that are required inputs to statistical observatory yield calculations, as well as guide development of post-processing algorithms for telescopes capable of directly imaging Earth-like planets.
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