Dr Geert Jan Talens

Abstract:

Simulated PLATO light curves generated at the University of Oxford in 2025. The light curves were used to test light curve filtering and transit detection algorithms. The light curves were generated in python using the PLATO Solar-like Light curve Simulator (PSLS), PySpot, and PyTransit codes. The data are primarily stored in feather files, which in python can be read using the pandas and pyarrow packages. Detailed information on the included files and contents are provided in the README file.

Abstract:

The Hungarian-made Automated Telescope PI Steradians (HATPI) is a recently commissioned time-domain facility at Las Campanas Observatory, Chile, that uses 64 wide-angle, 9.6 cm diameter lenses and back-illuminated CCDs, yielding a mosaic field-of-view of 7100 square arcdegrees, observing the night sky at a cadence of 45 s and a spatial scale of 19 .″ 7 pixel−1. In this paper, we present moving object time-series photometry with this facility, focusing on the interstellar comet 3I/ATLAS, which was first robustly recovered by HATPI on the night of 2025 July 2 (one night after its discovery) at a Gaia G-band magnitude of G = 17.796 ± 0.082 mag (±0.030 mag systematic uncertainty). The comet then increased in brightness to G = 14.071 ± 0.073 mag ± 0.030 mag by 2025 September 13, after which it became unobservable by HATPI as it approached perihelion. Before 3I/ATLAS achieved a brightness of G = 16.396 ± 0.029 mag ± 0.030 mag on 2025 August 6, it could be detected when stacking all HATPI observations from a single night, while after this date it is sufficiently bright to detect in individual 45 s exposures. We do not detect evidence for significant short-time-scale variations in the brightness of 3I/ATLAS after August 6. Compared to other light curves in the literature, the HATPI photometry exhibits a somewhat steeper rise in brightness with decreasing heliocentric distance, rH. The HATPI magnitudes are well-fit as a power law function of rH, with an exponential index of n = 5.167 ± 0.095, over the range 2.14 au

Abstract:

We report the discovery and characterization of three transiting giant planets in the TIC 118798035 system. The three planets were identified as transiting candidates from data of the TESS mission and confirmed with ground-based photometric transit observations along with radial velocity variations obtained with FEROS, HARPS, and ESPRESSO. The three planets present transit timing variations (TTVs). We performed an N-body orbital fitting to the TTVs and radial velocities, finding that TIC 118798035 b is a warm low-density Neptune with a mass of 0.0250 ± 0.0023 MJ, a radius of 0.655 ± 0.018 RJ, and an orbital period of 11.507 days; TIC 118798035 c is a warm Saturn with a mass of 0.403 ± 0.024 MJ, a radius of 0.973 ± 0.023 RJ, and an orbital period of 22.564 days; and TIC 118798035 d is a warm Jupiter with a mass of 0.773 ± 0.052 MJ, a radius of 0.923 ± 0.044 RJ, and an orbital period of 48.925 days. The bulk metallicities of the three planets do not fully follow the mass–metallicity correlation found for the giant planets of the solar system, which hints at a somewhat different formation history for the planets of the TIC 118798035 system.

Abstract:

We present a method for computing upper and lower limits to the expected duration of planetary transits given a range for the parameters of the host star, while explicitly accounting for non-zero impact parameter and eccentricity, and placing a basic constraint on the orbital stability through a minimum planet–star separation at periastron. We find that, especially at longer periods, the transit can be considerably shorter or longer than previous searches have assumed. No transits are known with such short or long transit durations, but it is unclear whether this is a real feature of the planet population or a combination of transit probability, observational bias, and detection bias.

Abstract:

PLATO (PLAnetary Transits and Oscillations of stars) is ESA’s M3 mission designed to detect and characterise extrasolar planets and perform asteroseismic monitoring of a large number of stars. PLATO will detect small planets (down to <2REarth) around bright stars (<11 mag), including terrestrial planets in the habitable zone of solar-like stars. With the complement of radial velocity observations from the ground, planets will be characterised for their radius, mass, and age with high accuracy (5%, 10%, 10% for an Earth-Sun combination respectively). PLATO will provide us with a large-scale catalogue of well-characterised small planets up to intermediate orbital periods, relevant for a meaningful comparison to planet formation theories and to better understand planet evolution. It will make possible comparative exoplanetology to place our Solar System planets in a broader context. In parallel, PLATO will study (host) stars using asteroseismology, allowing us to determine the stellar properties with high accuracy, substantially enhancing our knowledge of stellar structure and evolution. The payload instrument consists of 26 cameras with 12cm aperture each. For at least four years, the mission will perform high-precision photometric measurements. Here we review the science objectives, present PLATO‘s target samples and fields, provide an overview of expected core science performance as well as a description of the instrument and the mission profile towards the end of the serial production of the flight cameras. PLATO is scheduled for a launch date end 2026. This overview therefore provides a summary of the mission to the community in preparation of the upcoming operational phases.