26 research outputs found

    The CARMENES search for exoplanets around M dwarfs: Two planets on opposite sides of the radius gap transiting the nearby M dwarf LTT 3780

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    We present the discovery and characterisation of two transiting planets observed by the Transiting Exoplanet Survey Satellite (TESS) orbiting the nearby (d∗ ≈ 22 pc), bright (J ≈ 9 mag) M3.5 dwarf LTT 3780 (TOI-732). We confirm both planets and their association with LTT 3780 via ground-based photometry and determine their masses using precise radial velocities measured with the CARMENES spectrograph. Precise stellar parameters determined from CARMENES high-resolution spectra confirm that LTT 3780 is a mid-M dwarf with an effective temperature of Teff = 3360 ± 51 K, a surface gravity of log g∗ = 4.81 ± 0.04 (cgs), and an iron abundance of [Fe/H] = 0.09 ± 0.16 dex, with an inferred mass of M∗ = 0.379 ± 0.016M· and a radius of R∗ = 0.382 ± 0.012R·. The ultra-short-period planet LTT 3780 b (Pb = 0.77 d) with a radius of 1.35-0.06+0.06 R·, a mass of 2.34-0.23+0.24 M·, and a bulk density of 5.24-0.81+0.94 g cm-3 joins the population of Earth-size planets with rocky, terrestrial composition. The outer planet, LTT 3780 c, with an orbital period of 12.25 d, radius of 2.42-0.10+0.10 R·, mass of 6.29-0.61+0.63 M·, and mean density of 2.45-0.37+0.44 g cm-3 belongs to the population of dense sub-Neptunes. With the two planets located on opposite sides of the radius gap, this planetary system is anexcellent target for testing planetary formation, evolution, and atmospheric models. In particular, LTT 3780 c is an ideal object for atmospheric studies with the James Webb Space Telescope (JWST)

    Complexity, chaos and catastrophe: Modeling psychopathology as a dynamic system

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    In recent years, the notion that correlations between questionnaire items are the result of direct interactions between these variables has grown in popularity. Various methods exist for estimating the connectivity of a network. Networks can be estimated for an entire group or for individuals. All three methods control for such potentially spurious edges by using the least absolute shrinkage and selection operator. Essentially, the IsingFit method regresses one node on all other nodes in an iterative manner, using the optimal penalty parameter. Both networks are equally important and interesting: when collecting time-series data, one is often interested in the progression of an individual throughout time. There is evidence for the hypothesis that all catastrophic systems, from financial systems to the climate, display early warning signals that the system is approaching a tipping point. The empirical mean field approximation is based on the work of Waldorp and Kossakowski.
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