Browsing by Author "Oyarce Leal, María Laura"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    In-depth Investigation of a Type II Cepheid in a Binary System
    (2025) Oyarce Leal, María Laura; Catelan, Márcio; Pilecki, Bogumił; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
    Type II Cepheids are old, low-mass variable stars that are essential for mapping old stellar populations, thanks to their greater brightness compared to RR Lyrae. They play a key role in calibrating cosmic distances. OGLE-GD-T2CEP-0178, a type II Cepheid located in the Galactic disk, is part of an eclipsing binary system, which allows its mass to be directly measured and to study its evolutionary status.The main goal of this thesis was to determine the masses of OGLE-GD-T2CEP-0178 and its companion and to characterize the binary system. Spectroscopic data obtained with HARPS and photometric data from six surveys in different bands were used. Through light and radial velocity curves modeling with PHOEBE, the physical parameters of each component and the key orbital parameters of the system were derived.The results reveal that the binary system (P_orb=81.72 days) is composed of a type II Cepheid with a pulsation period of P_puls=3.833 days, a mass of M_ cep=1.16 +- 0.09 Msun and a radius of R_cep=14.12 +- 1.73 Rsun, along with a more massive companion of M_ comp=5.5 +- 0.3 Msun. The system also has a disk with a radius of R_disk=174 +- 42 Rsun. The complexity of the system suggests that some companion parameters could be underestimated.These results support the hypothesis that the current Cepheid underwent a past mass transfer event during which it lost part of its hydrogen envelope. As a consequence, the Cepheid's pulsation properties may have been affected. To confirm this scenario, a detailed binary evolution analysis must be performed to understand how mass transfer shaped the system's current configuration.