Year: 2024
Type: article
Abstract: Context. To date, puzzlingly few bona fide RR Lyrae stars have been identified in binaries. Binarity in pulsating stars can be revealed through well-timed photometric data over sufficiently long time bases because of the light travel time effect (LTTE) on the pulsations, which manifests as variation in the timings of maximum light in the O−C (observed minus calculated) diagram. However, O−C variations can also have other causes, such as the Blazhko effect or a sudden or gradual change in the main pulsation period. Aims. We approach this challenge by disentangling the Blazhko effect and period changes from the potential LTTE on V1109 Cas, an RR Lyrae star suspected to be part of a binary system based on its O−C data in the GEOS database. In doing so, we aim to uncover the subtler signals indicative of a companion (LTTE). Methods. We analysed nine years of ground-based photometric data, using Fourier analysis to model the pulsation modulated by the Blazhko effect. From the fit to the observed light curves, we constructed a refined O−C diagram without the scatter caused by Blazhko modulation. Subsequently, we considered different possible scenarios, because distinguishing intrinsic period changes or breaks from the LTTE is challenging. Results. If the remaining O−C variation is due to a period break, refining the O−C diagram can almost entirely remove the trends. If we interpret the variation as an LTTE, we can consider possible configurations. While we currently favour a period break as the explanation for the residual O−C variations, more data on the star in the forthcoming years will help reveal whether the O−C variations are due to the LTTE or intrinsic period changes. Conclusions. Our study, based on a detailed light-curve fitting of V1109 Cas, offers insights into the discernment between Blazhko modulation, intrinsic period breaks, and the LTTE in binary systems. Our results highlight the complexity of determining binarity from O−C data traditionally used for detecting binary motion, calling for caution in this process.
Source: Astronomy and Astrophysics
Institutions: Centre National de la Recherche Scientifique, University of Antwerp, Université de Lille, Université Paris Sciences et Lettres, Observatoire de Paris, Sorbonne Université, Institut Sénégalais de Recherches Agricoles, Institut de Mécanique Céleste et de Calcul des Éphémérides, Cheikh Anta Diop University, Vrije Universiteit Brussel, Center for Astrophysics Harvard & Smithsonian, KU Leuven, Université Toulouse III - Paul Sabatier, Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, Observatoire Midi-Pyrénées, Géosciences Environnement Toulouse, Institut de Recherche pour le Développement, Université Félix Houphouët-Boigny, Laboratoire d’Astrophysique de Marseille, Cadi Ayyad University, ECAM Rennes Louis de Broglie
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,732
Funders: Vlaamse Interuniversitaire Raad, VLIRUOS
OpenAlex ID: W4402915078