We perform a study of stellar flares for the 24,809 stars observed with 2 minute cadence during the first two months of the TESS mission. Flares may erode exoplanets' atmospheres and impact their ...habitability, but might also trigger the genesis of life around small stars. TESS provides a new sample of bright dwarf stars in our galactic neighborhood, collecting data for thousands of M dwarfs that might host habitable exoplanets. Here, we use an automated search for flares accompanied by visual inspection. Then, our public allesfitter code robustly selects the appropriate model for potentially complex flares via Bayesian evidence. We identify 1228 flaring stars, 673 of which are M dwarfs. Among 8695 flares in total, the largest superflare increased the stellar brightness by a factor of 16.1. Bolometric flare energies range from 1031.0 to 1036.9 erg, with a median of 1033.1 erg. Furthermore, we study the flare rate and energy as a function of stellar type and rotation period. We solidify past findings that fast rotating M dwarfs are the most likely to flare and that their flare amplitude is independent of the rotation period. Finally, we link our results to criteria for prebiotic chemistry, atmospheric loss through coronal mass ejections, and ozone sterilization. Four of our flaring M dwarfs host exoplanet candidates alerted on by TESS, for which we discuss how these effects can impact life. With upcoming TESS data releases, our flare analysis can be expanded to almost all bright small stars, aiding in defining criteria for exoplanet habitability.
We present the discovery of a transiting hot Jupiter orbiting HIP 67522 (Teff ∼ 5650 K; M* ∼ 1.2M ) in the 10-20 Myr old Sco-Cen OB association. We identified the transits in the TESS data using our ...custom notch filter planet search pipeline and characterize the system with additional photometry from Spitzer; spectroscopy from SOAR/Goodman, SALT/HRS, LCOGT/NRES, and SMARTS/CHIRON; and speckle imaging from SOAR/HRCam. We model the photometry as a periodic Gaussian process with transits to account for stellar variability and find an orbital period of days and radius of R⊕. We also identify a single transit of an additional candidate planet with radius R⊕ that has an orbital period of 23 days. The validated planet HIP 67522b is currently the youngest transiting hot Jupiter discovered and is an ideal candidate for transmission spectroscopy and radial velocity follow-up studies, while also demonstrating that some young giant planets either form in situ at small orbital radii or else migrate promptly from formation sites farther out in the disk.
Abstract
We present the results of a spectroscopic monitoring program of the Pleiades region aimed at completing the census of spectroscopic binaries in the cluster, extending it to longer periods ...than previously reachable. We gathered 6104 spectra of 377 stars between 1981 and 2021, and merged our radial velocities with 1151 measurements from an independent survey by others started three years earlier. With the combined data spanning more than 43 yr, we have determined orbits for some 30 new binary and multiple systems, more than doubling the number previously known in the Pleiades. The longest period is 36.5 yr. A dozen additional objects display long-term trends in their velocities, implying even longer periods. We examine the collection of orbital elements for cluster members, and find that the shape of the incompleteness-corrected distribution of periods (up to 10
4
days) is similar to that of solar-type binaries in the field, while that of the eccentricities is different. The mass-ratio distribution is consistent with being flat. The binary frequency in the Pleiades for periods up to 10
4
days is 25% ± 3% after corrections for undetected binaries, which is nearly double that of the field up to the same period. The total binary frequency including known astrometric binaries is at least 57%. We estimate the internal radial velocity dispersion in the cluster to be 0.48 ± 0.04 km s
−1
. We revisit the determination of the tidal circularization period, and confirm its value to be 7.2 ± 1.0 days, with an improved precision compared to an earlier estimate.
Planets in young clusters are powerful probes of the evolution of planetary systems. Here we report the discovery of three planets transiting EPIC 247589423, a late-K dwarf in the Hyades ( 800 Myr) ...cluster, and robust detection limits for additional planets in the system. The planets were identified from their K2 light curves as part of our survey of young clusters and star-forming regions. The smallest planet has a radius comparable to Earth ( ), making it one of the few Earth-sized planets with a known, young age. The two larger planets are likely a mini-Neptune and a super-Earth, with radii of and , respectively. The predicted radial velocity signals from these planets are between 0.4 and 2 m s−1, achievable with modern precision RV spectrographs. Because the target star is bright (V = 11.2) and has relatively low-amplitude stellar variability for a young star (2-6 mmag), EPIC 247589423 hosts the best known planets in a young open cluster for precise radial velocity follow-up, enabling a robust test of earlier claims that young planets are less dense than their older counterparts.
We report the discovery of two intermediate-mass transiting brown dwarfs (BDs), TOI-569b and TOI-1406b, from NASA's Transiting Exoplanet Survey Satellite mission. TOI-569b has an orbital period of P ...= 6.55604 0.00016 days, a mass of Mb = 64.1 1.9 , and a radius of Rb = 0.75 0.02 . Its host star, TOI-569, has a mass of M = 1.21 0.05 , a radius of R = 1.47 0.03 , dex, and an effective temperature of Teff = 5768 110 K. TOI-1406b has an orbital period of P = 10.57415 0.00063 days, a mass of Mb = 46.0 2.7 , and a radius of Rb = 0.86 0.03 . The host star for this BD has a mass of M = 1.18 0.09 , a radius of R = 1.35 0.03 , dex, and an effective temperature of Teff = 6290 100 K. Both BDs are in circular orbits around their host stars and are older than 3 Gyr based on stellar isochrone models of the stars. TOI-569 is one of two slightly evolved stars known to host a transiting BD (the other being KOI-415). TOI-1406b is one of three known transiting BDs to occupy the mass range of 40-50 and one of two to have a circular orbit at a period near 10 days (with the first being KOI-205b). Both BDs have reliable ages from stellar isochrones, in addition to their well-constrained masses and radii, making them particularly valuable as tests for substellar isochrones in the BD mass-radius diagram.
Abstract
While secondary mass inferences based on single-lined spectroscopic binary (SB1) solutions are subject to
sin
i
degeneracies, this degeneracy can be lifted through the observations of ...eclipses. We combine the subset of Gaia Data Release 3 SB1 solutions consistent with brown dwarf-mass secondaries with the Transiting Exoplanet Survey Satellite (TESS) Object of Interest (TOI) list to identify three candidate transiting brown dwarf systems. Ground-based precision radial velocity follow-up observations confirm that TOI-2533.01 is a transiting brown dwarf with
M
=
72
−
3
+
3
M
Jup
=
0.069
−
0.003
+
0.003
M
⊙
orbiting TYC 2010-124-1 and that TOI-5427.01 is a transiting very low-mass star with
M
=
93
−
2
+
2
M
Jup
=
0.088
−
0.002
+
0.002
M
⊙
orbiting UCAC4 515-012898. We validate TOI-1712.01 as a very low-mass star with
M
=
82
−
7
+
7
M
Jup
=
0.079
−
0.007
+
0.007
M
⊙
transiting the primary in the hierarchical triple system BD+45 1593. Even after accounting for third light, TOI-1712.01 has a radius nearly a factor of 2 larger than predicted for isolated stars with similar properties. We propose that the intense instellation experienced by TOI-1712.01 diminishes the temperature gradient near its surface, suppresses convection, and leads to its inflated radius. Our analyses verify Gaia DR3 SB1 solutions in the low Doppler semiamplitude limit, thereby providing the foundation for future joint analyses of Gaia radial velocities and Kepler, K2, TESS, and PLAnetary Transits and Oscillations light curves for the characterization of transiting massive brown dwarfs and very low-mass stars.
Abstract
We report initial results of a large radial velocity survey of K dwarfs up to a distance of 50 pc from the solar system, to look for stellar, brown dwarf, and Jovian planets using radial ...velocities from the CHIRON spectrograph on the CTIO/SMARTS 1.5 m telescope. We identify three new exoplanet candidates orbiting host stars in the K dwarf survey and confirm a hot Jupiter from TESS orbiting TOI 129. Our techniques are confirmed via five additional known exoplanet orbiting K dwarfs, bringing the number of orbital solutions presented here to 9, each hosting an exoplanet candidate with a minimum mass of 0.5–3.0
M
Jup
. In addition, we provide a list of 186 nearby K dwarfs with no detected close companions that are ideal for more sensitive searches for lower-mass planets. This set of stars is used to determine CHIRON’s efficiency, stability, and performance for radial velocity work. For K dwarfs with
V
= 7–12, we reach radial velocity precisions of 5–20 ms
−1
under a wide range of observing conditions. We demonstrate the stability of CHIRON over hours, weeks, and years using radial velocity standards, and describe instrumental capabilities and operation modes available for potential users.
We present the obliquity of the warm Neptune HD 106315c measured via a series of spectroscopic transit observations. HD 106315c is a 4.4 REarth warm Neptune orbiting a moderately rotating late F star ...with a period of 21.05 days. HD 106315 also hosts a 2.5 REarth super-Earth on a 9.55 day orbit. Our Doppler tomographic analyses of four transits observed by the Magellan/MIKE, HARPS, and TRES facilities find HD 106315c to be in a low stellar obliquity orbit, consistent with being well aligned with the spin axis of the host star at . We suggest, via dynamical N-body simulations, that the two planets in the system must be coplanar, and thus are both well aligned with the host star. HD 106315 is only the fourth warm Neptune system with obliquities measured. All warm Neptune systems have been found in well aligned geometries, consistent with the interpretation that these systems are formed in situ in the inner protoplanetary disk, and also consistent with the majority of Kepler multi-planet systems that are in low obliquity orbits. With a transit depth of 1.02 mmag, HD 106315c is among the smallest planets to have been detected in transit spectroscopy, and we discuss its detection in the context of TESS and the next generations of spectrographs.
The detection and characterization of young planetary systems offer a direct path to study the processes that shape planet evolution. We report on the discovery of a sub-Neptune-sized planet orbiting ...the young star HD 110082 (TOI-1098). Transit events we initially detected during TESS Cycle 1 are validated with time-series photometry from Spitzer. High-contrast imaging and high-resolution, optical spectra are also obtained to characterize the stellar host and confirm the planetary nature of the transits. The host star is a late-F dwarf (M⁎ = 1.2Mꙩ) with a low-mass, M dwarf binary companion (M⁎ = 0.26Mꙩ) separated by nearly one arcminute (∼6200 au). Based on its rapid rotation and Lithium absorption, HD 110082 is young, but is not a member of any known group of young stars (despite proximity to the Octans association). To measure the age of the system, we search for coeval, phase-space neighbors and compile a sample of candidate siblings to compare with the empirical sequences of young clusters and to apply quantitative age-dating techniques. In doing so, we find that HD 110082 resides in a new young stellar association we designate MELANGE-1, with an age of 250(+50, -70) Myr. Jointly modeling the TESS and Spitzer light curves, we measure a planetary orbital period of 10.1827 days and radius of R(p) = 3.2 ± 0.1Rꚛ. HD 110082 b’s radius falls in the largest 12% of field-age systems with similar host-star mass and orbital period. This finding supports previous studies indicating that young planets have larger radii than their field-age counterparts.
Kepler constraints on planets near hot Jupiters Steffen, Jason H; Ragozzine, Darin; Fabrycky, Daniel C ...
Proceedings of the National Academy of Sciences - PNAS,
05/2012, Letnik:
109, Številka:
21
Journal Article
Recenzirano
Odprti dostop
We present the results of a search for planetary companions orbiting near hot Jupiter planet candidates (Jupiter-size candidates with orbital periods near 3 d) identified in the Kepler data through ...its sixth quarter of science operations. Special emphasis is given to companions between the 2:1 interior and exterior mean-motion resonances. A photometric transit search excludes companions with sizes ranging from roughly two-thirds to five times the size of the Earth, depending upon the noise properties of the target star. A search for dynamically induced deviations from a constant period (transit timing variations) also shows no significant signals. In contrast, comparison studies of warm Jupiters (with slightly larger orbits) and hot Neptune-size candidates do exhibit signatures of additional companions with these same tests. These differences between hot Jupiters and other planetary systems denote a distinctly different formation or dynamical history.
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