Convergent disk migration has long been suspected to be responsible for forming planetary systems with a chain of mean-motion resonances (MMR). Dynamical evolution over time could disrupt the ...delicate resonant configuration. We present TOI-1136, a 700-Myr-old G star hosting at least 6 transiting planets between \(\sim\)2 and 5 \(R_\oplus\). The orbital period ratios deviate from exact commensurability by only \(10^{-4}\), smaller than the \(\sim\)\,\(10^{-2}\) deviations seen in typical Kepler near-resonant systems. A transit-timing analysis measured the masses of the planets (3-8\(M_\oplus\)) and demonstrated that the planets in TOI-1136 are in true resonances with librating resonant angles. Based on a Rossiter-McLaughlin measurement of planet d, the star's rotation appears to be aligned with the planetary orbital planes. The well-aligned planetary system and the lack of detected binary companion together suggest that TOI-1136's resonant chain formed in an isolated, quiescent disk with no stellar fly-by, disk warp, or significant axial asymmetry. With period ratios near 3:2, 2:1, 3:2, 7:5, and 3:2, TOI-1136 is the first known resonant chain involving a second-order MMR (7:5) between two first-order MMR. The formation of the delicate 7:5 resonance places strong constraints on the system's migration history. Short-scale (starting from \(\sim\)0.1 AU) Type-I migration with an inner disk edge is most consistent with the formation of TOI-1136. A low disk surface density (\(\Sigma_{\rm 1AU}\lesssim10^3\)g~cm\(^{-2}\); lower than the minimum-mass solar nebula) and the resultant slower migration rate likely facilitated the formation of the 7:5 second-order MMR. TOI-1136's deep resonance suggests that it has not undergone much resonant repulsion during its 700-Myr lifetime. One can rule out rapid tidal dissipation within a rocky planet b or obliquity tides within the largest planets d and f.
We report the discovery and analysis of a massive, compact, hierarchical triple system (TIC 470710327) initially identified by citizen scientists in data obtained by NASA's Transiting Exoplanet ...Survey Satellite (TESS). Spectroscopic follow-up observations obtained with the HERMES spectrograph, combined with eclipse timing variations (ETVs), confirm that the system is comprised of three OB stars, with a compact 1.10 d eclipsing binary and a non-eclipsing tertiary on a 52.04 d orbit. Dynamical modelling of the system (from radial velocity and ETVs) reveal a rare configuration wherein the tertiary star (O9.5-B0.5V; 14-17 M\(_{\odot}\)) is more massive than the combined mass of the inner binary (10.9-13.2 M\(_{\odot}\)). Given the high mass of the tertiary, we predict that this system will undergo multiple phases of mass transfer in the future, and likely end up as a double neutron star gravitational wave progenitor or an exotic Thorne-Zytkow object. Further observational characterisation of this system promises constraints on both formation scenarios of massive stars as well as their exotic evolutionary end-products.
We report the discovery of 14 new transiting planet candidates in the Kepler field from the Planet Hunters citizen science program. None of these candidates overlapped with Kepler Objects of Interest ...(KOIs) at the time of submission. We report the discovery of one more addition to the six planet candidate system around KOI-351, making it the only seven planet candidate system from Kepler. Additionally, KOI-351 bears some resemblance to our own solar system, with the inner five planets ranging from Earth to mini-Neptune radii and the outer planets being gas giants; however, this system is very compact, with all seven planet candidates orbiting lap1 AU from their host star. A Hill stability test and an orbital integration of the system shows that the system is stable. Furthermore, we significantly add to the population of long period transiting planets; periods range from 124 to 904 days, eight of them more than one Earth year long. Seven of these 14 candidates reside in their host star's habitable zone.
In this paper we present a catalog of 4584 eclipsing binaries observed during the first two years (26 sectors) of the TESS survey. We discuss selection criteria for eclipsing binary candidates, ...detection of hither-to unknown eclipsing systems, determination of the ephemerides, the validation and triage process, and the derivation of heuristic estimates for the ephemerides. Instead of keeping to the widely used discrete classes, we propose a binary star morphology classification based on a dimensionality reduction algorithm. Finally, we present statistical properties of the sample, we qualitatively estimate completeness, and discuss the results. The work presented here is organized and performed within the TESS Eclipsing Binary Working Group, an open group of professional and citizen scientists; we conclude by describing ongoing work and future goals for the group. The catalog is available from http://tessEBs.villanova.edu and from MAST.
We report the discovery of TOI-2180 b, a 2.8 \(M_{\rm J}\) giant planet orbiting a slightly evolved G5 host star. This planet transited only once in Cycle 2 of the primary Transiting Exoplanet Survey ...Satellite (TESS) mission. Citizen scientists identified the 24 hr single-transit event shortly after the data were released, allowing a Doppler monitoring campaign with the Automated Planet Finder telescope at Lick Observatory to begin promptly. The radial velocity observations refined the orbital period of TOI-2180 b to be 260.8\(\pm\)0.6 days, revealed an orbital eccentricity of 0.368\(\pm\)0.007, and discovered long-term acceleration from a more distant massive companion. We conducted ground-based photometry from 14 sites spread around the globe in an attempt to detect another transit. Although we did not make a clear transit detection, the nondetections improved the precision of the orbital period. We predict that TESS will likely detect another transit of TOI-2180 b in Sector 48 of its extended mission. We use giant planet structure models to retrieve the bulk heavy-element content of TOI-2180 b. When considered alongside other giant planets with orbital periods over 100 days, we find tentative evidence that the correlation between planet mass and metal enrichment relative to stellar is dependent on orbital properties. Single-transit discoveries like TOI-2180 b highlight the exciting potential of the TESS mission to find planets with long orbital periods and low irradiation fluxes despite the selection biases associated with the transit method.
In the present work, the study of the unusual interaction between copper hexafluoroacetylacetonate and the diacetyliminoxyl radical resulted in two discoveries from different fields: the ...determination of the oxime radical spatial structure and the introduction of an oxime radical into the field of molecular magnetic material design. Oxime radicals are key plausible intermediates in the processes of oxidative CH-functionalization and in the synthesis of functionalized isoxazolines from oximes. Due to the lack of X-ray diffraction data for oxime radicals, the knowledge about their structure is based mainly on indirect approaches, spectroscopic methods (electron paramagnetic resonance and IR), and quantum chemical calculations. The structure of the oxime radical was determined for the first time by stabilizing the diacetyliminoxyl radical in the form of its complex with copper (II) hexafluoroacetylacetonate (Cu(hfac)2), followed by single-crystal X-ray diffraction analysis. Although oxime radicals are known to undergo oxidative coupling with acetylacetonate ligands in transition-metal complexes, a complex is formed with intact hfac ligands. X-ray diffraction studies have shown that the oxime radical is coordinated with copper ions through the oxygen atoms of the carbonyl groups without the direct involvement of the CN–O• radical moiety. The structure of the coordinated diacetyliminoxyl is in good agreement with the density functional theory (DFT) prediction for free diacetyliminoxyl due to the very weak interaction of the radical molecule with copper ions. Remarkably, both weak ferromagnetic and antiferromagnetic interactions between Cu (II) and oxime radicals have been revealed by modeling the temperature dependence of magnetic susceptibility and confirmed by DFT calculations, rendering diacetyliminoxyl a promising building block for the design of molecular magnets.
We report the discovery of a sextuply-eclipsing sextuple star system from TESS data, TIC 168789840, also known as TYC 7037-89-1, the first known sextuple system consisting of three eclipsing ...binaries. The target was observed in Sectors 4 and 5 during Cycle 1, with lightcurves extracted from TESS Full Frame Image data. It was also previously observed by the WASP survey and ASAS-SN. The system consists of three gravitationally-bound eclipsing binaries in a hierarchical structure of an inner quadruple system with an outer binary subsystem. Follow-up observations from several different observatories were conducted as a means of determining additional parameters. The system was resolved by speckle interferometry with a 0."42 separation between the inner quadruple and outer binary, inferring an estimated outer period of ~2 kyr. It was determined that the fainter of the two resolved components is an 8.217 day eclipsing binary, which orbits the inner quadruple that contains two eclipsing binaries with periods of 1.570 days and 1.306 days. MCMC analysis of the stellar parameters has shown that the three binaries of TIC 168789840 are "triplets", as each binary is quite similar to the others in terms of mass, radius, and Teff. As a consequence of its rare composition, structure, and orientation, this object can provide important new insight into the formation, dynamics, and evolution of multiple star systems. Future observations could reveal if the intermediate and outer orbital planes are all aligned with the planes of the three inner eclipsing binaries.
We report the discovery and validation of four extrasolar planets hosted by the nearby, bright, Sun-like (G3V) star HD~108236 using data from the Transiting Exoplanet Survey Satellite (TESS). We ...present transit photometry, reconnaissance and precise Doppler spectroscopy as well as high-resolution imaging, to validate the planetary nature of the objects transiting HD~108236, also known as the TESS Object of Interest (TOI) 1233. The innermost planet is a possibly-rocky super-Earth with a period of \(3.79523_{-0.00044}^{+0.00047}\) days and has a radius of \(1.586\pm0.098\) \(R_\oplus\). The outer planets are sub-Neptunes, with potential gaseous envelopes, having radii of \(2.068_{-0.091}^{+0.10}\) \(R_\oplus\), \(2.72\pm0.11\) \(R_\oplus\), and \(3.12_{-0.12}^{+0.13}\) \(R_\oplus\) and periods of \(6.20370_{-0.00052}^{+0.00064}\) days, \(14.17555_{-0.0011}^{+0.00099}\) days, and \(19.5917_{-0.0020}^{+0.0022}\) days, respectively. With V and K\(_{\rm s}\) magnitudes of 9.2 and 7.6, respectively, the bright host star makes the transiting planets favorable targets for mass measurements and, potentially, for atmospheric characterization via transmission spectroscopy. HD~108236 is the brightest Sun-like star in the visual (V) band known to host four or more transiting exoplanets. The discovered planets span a broad range of planetary radii and equilibrium temperatures, and share a common history of insolation from a Sun-like star (\(R_\star = 0.888 \pm 0.017\) R\(_\odot\), \(T_{\rm eff} = 5730 \pm 50\) K), making HD 108236 an exciting, opportune cosmic laboratory for testing models of planet formation and evolution.
Exoplanets can evolve significantly between birth and maturity, as their atmospheres, orbits, and structures are shaped by their environment. Young planets (\(<\)1 Gyr) offer an opportunity to probe ...the critical early stages of this evolution, where planets evolve the fastest. However, most of the known young planets orbit prohibitively faint stars. We present the discovery of two planets transiting HD 63433 (TOI 1726, TIC 130181866), a young Sun-like (\(M_*=0.99\pm0.03\)) star. Through kinematics, lithium abundance, and rotation, we confirm that HD 63433 is a member of the Ursa Major moving group (\(\tau=414\pm23\) Myr). Based on the TESS light curve and updated stellar parameters, we estimate the planet radii are \(2.15\pm0.10R_\oplus\) and \(2.67\pm0.12R_\oplus\), the orbital periods are 7.11 and 20.55 days, and the orbital eccentricities are lower than about 0.2. Using HARPS-N velocities, we measure the Rossiter-McLaughlin signal of the inner planet, demonstrating that the orbit is prograde. Since the host star is bright (V=6.9), both planets are amenable to transmission spectroscopy, radial velocity measurements of their masses, and more precise determination of the stellar obliquity. This system is therefore poised to play an important role in our understanding of planetary system evolution in the first billion years after formation.
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