arXiv subjects

Inês Rolo

Publications and source records attributed to Inês Rolo.

3 recordsLinked to original sources

arXiv2026

Rapidly oscillating Ap stars observed with TESS. The LAMOST Ap sample and 49 Cam

The rapidly oscillating chemically peculiar A-type (roAp) stars offer valuable insights into the internal physical processes of all stars, but their study is challenged by their rarity. The large-scale TESS surveys have allowed for the collection of data for a sizeable dataset of roAp stars. Nevertheless, asteroseismic data obtained with TESS and Gaia has not been explored to its full potential. We develop an algorithm capable of analysing large quantities of data to search for new roAp stars and increase the current sample. We focus on data products that have not been previously explored for the search of roAp stars, namely the 200-s FFIs and 20-s cadence light curves. 20-s and 200-s cadence light curves of target stars are retrieved from the MAST server and cleaned. DFTs are computed for each light curve which are used to pre-whiten the data to remove any low frequency signals. A final DFT is calculated which is used to classify stars as non-pulsating (NP), delta Scuti or roAp based on the remaining signal. We apply our algorithm to two independent datasets: i) ~2700 Ap stars spectroscopically classified with LAMOST and observed by TESS in the 200-s FFIs and ii) all TESS 20-s cadence light curves available for known or candidate roAp stars. These two samples have no overlap, i.e. none of the LAMOST stars have been observed with 20-s cadence. We identify four new roAp stars: TIC 312111544, TIC 252881095, TIC 46054683, and 49 Cam (TIC 393276640). We find evidence in TESS data that TIC 252881095 may be part of a binary system. If the tentative ~30-d orbital signal is confirmed, TIC 252881095 could be one of the shortest-period roAp binary currently known. Furthermore, the detection of high-frequency pulsations in 49 Cam is particularly relevant, as this well-known roAp candidate star is here confirmed to be roAp based on TESS 20-s cadence data.

astro-ph.SR↗

arXiv2026

Variability classification of TESS targets in LOPS2, the first long-term pointing field of PLATO. Version 1 of the public variability catalogue

The PLAnetary Transits and Oscillations of stars (PLATO) mission is expected to launch in January 2027. A total of 8\% of its data rate will be dedicated to complementary science targets selected from approved Guest Observer proposals. We seek to provide an open-source catalogue of variable stars in PLATO's first long-term observing field, LOPS2. We want to use existing observations from the Transiting Exoplanet Survey Satellite (TESS), which has observed many stars in LOPS2. We classified 38 million calibrated aperture light curves from the TESS-Gaia Light Curve pipeline (TGLC, $G\lesssim17$) for 6 million unique sources in LOPS2 with two machine learning frameworks -- a deep neural network and a feature-based gradient-boosted decision-tree ensemble. We combined their predictions to create this first version of the LOPS2 variability catalogue, performed manual vetting of a sub-sample classified light curves, and a statistical analysis of the results to validate our methodology and to assess the variability properties and parameters of the stars in the catalogue. Our classification resulted in the identification of approximately 72% of the light curves having dominant instrument- or pipeline-induced signal, with the remaining 28% representing 3.6 million individual candidate variable stars, including pulsating, rotating, and eclipsing stars. Candidate pulsators exhibit varied behaviour in terms of their frequencies, amplitudes, rotation, and fundamental parameters. To ensure purity of the samples, filtering on colour, luminosity, the dominant frequency and its amplitude, and presence of close neighbours is helpful. We provide the first version of our PLATO LOPS2 variability catalogue to the community for further study and scrutiny. It is to date one of the largest catalogues of variable stars from an automated classification pipeline.

astro-ph.SR↗

arXiv2024

The enigma of Li-rich giants and its relation with temporal variations observed in radial velocity and stellar activity signals

Despite the large number of studies focused on the characterisation of Li-rich stars and understanding the mechanisms leading to such enrichment, their origin remains a mystery. Magnetic activity, particularly the phenomena usually associated with it, and the Li abundance (A(Li)) of stars, are in general thought to be connected. As of today, however, just how they are connected is unclear. In this work, we study a sample of young but evolved intermediate-mass red giants that are inhabitants of open clusters where planets have been searched for. Our aim is to use radial velocity (RV) and stellar activity indicator signals to look for relations between Li abundances and stellar activity or variability. We explored how the standard deviation (STD), peak-to-peak amplitude (PTP), mean, and median of typical stellar activity indicators (BIS, FWHM, $T_\textrm{eff}$, and H$α$ index) change as a function of the Li content of 82 red giants. Furthermore, we computed weighted Pearson correlation coefficients ($ρ_w$) between time series of RV measurements and the stellar activity indicators for the stars in our sample. To aid our results, we also studied generalized Lomb-Scargle periodograms (GLSP) to capture possible significant periodic temporal variations in our data. Our analysis indicates that the STD and PTP of BIS and FWHM, the mean and median of the H$α$ index, and $v\sin(i)$ increase exponentially with A(Li) in our sample of red giants. Significant temporal variations and correlations between RVs and activity indicators also tend to be found preferentially for stars where high A(Li) is observed. Most of the Li-rich stars in our sample either show strong correlations of RV with at least one of the stellar activity indicators or reveal significant periodic temporal variations in their GLSPs of stellar activity indicators that are consistent with those found for RV.

astro-ph.SR↗