TOI-421 Archives

The ATREIDES Program In Search Of Lost Exo-Neptunes

by Keith CowingSeptember 17, 2025September 17, 2025

An international team led by the University of Geneva (UNIGE), including scientists from the National Centre of Competence in Research PlanetS, the University of Warwick, and the Canary Islands Institute […]

Schematic view of the seven planetary systems studied in this work. In the upper panel, the location on the x-axis shows the orbital semi-major axis of the planets in question, on a linear scale, with the horizontal lines reaching out from the planet showing the range of its orbit from pericentre to apocentre. The size of the marker for each planet gives the observed radius, as presented in the discovery work, whilst the colour of the marker gives the measured mass for the planet. In the case of the planets orbiting HD 63433, no measured mass has been obtained to date, and we therefore plot an estimated mass for the two planets in that system, based on Figure 3 of Chen & Kipping (2017). In the case of TOI 1670 b, the mass given is an upper limit. The lower panel presents most of the same information (mass, radius, etc.), but shows the separation of the planetary systems in terms of their orbital periods, with the period of the inner planet in each system set to unity. The parent stars are shown sized relative to one another, but not to scale with their planets, and their colour in the plot denotes their effective temperatures, Teff. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

The Search For The Inbetweeners: How Packed Are TESS Planetary Systems?

by Keith CowingNovember 7, 2024November 7, 2024

In this work, we examine seven systems discovered by TESS, to see whether there is any room in those systems for an additional planet (or several) to lurk unseen between […]

Stability analysis of the TOI-421 planetary system. For fixed initial conditions (Table 6), the parameter space of the system was explored by varying the orbital period Pb and the eccentricity eb of planet-b (left panel) and the eccentricities of both planets (right panel). The step size was 10−3 day in orbital period and 0.0025 in eccentricity. For each initial condition, the system was integrated over 5000 yr and a stability indicator was calculated, which involved a frequency analysis of the mean longitude of the inner planet. The chaotic diffusion was measured by the variation in the frequency (see text). Red points correspond to highly unstable orbits, while blue points correspond to orbits which are likely to be stable on a billion-years timescale. The black dots show the values of the best fit solution (Table 6). -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Characterisation Of The TOI-421 Planetary System Using CHEOPS, TESS, and Archival Radial Velocity Data

by Keith CowingApril 20, 2024

The TOI-421 planetary system contains two sub-Neptune-type planets and is a prime target to study the formation and evolution of planets and their atmospheres.