Discovery of a substellar companion in the TESS light curve of the δ Scuti/γ Doradus hybrid pulsator HD 31221

Kálmán, Sz.; Derekas, A.; Csizmadia, Sz.; Szabó, Gy. M.; Hegedűs, V.; Smith, A. M. S.; Kovács, J.; Ziegler, C.; Pál, A.; Szabó, R.; Parviainen, H.; Murgas, F.
Referencia bibliográfica

Astronomy and Astrophysics

Fecha de publicación:
5
2023
Número de autores
12
Número de autores del IAC
2
Número de citas
1
Número de citas referidas
0
Descripción
Context. Close-in, sub-stellar companions to δ Scuti type stars present a highly suitable testbed for examining how planetary-mass objects can influence stellar pulsations.
Aims: We aim to constrain the mass of HD 31221 b, probe its atmosphere, and demonstrate how it affects the pulsational pattern of its host, HD 31221.
Methods: We made use of the available data from the short-cadence Transiting Exoplanet Survey Satellite (TESS). We modeled the nine observed transits and the out-of-phase variations, including Doppler beaming, ellipsoidal variations, and the reflection effect. We also incorporated ground-based photometry from the MuSCAT2 imager installed at the 1.52 m Telescopio Carlos Sanchez in the Teide Observatory, Spain, as well as speckle interferometry from the Southern Astrophysical Research telescope.
Results: We found HD 31221 b to have an orbital period of 4.66631 ± 0.00011 days, with a radius of 1.32 ± 0.14 RJ and a mass of 11.5 ± 10.3 MJ (from the ellipsoidal effect), making it consistent with either a brown dwarf or a giant planet. As HD 31221 is a rapid rotator (v sin I⋆ = 175.31 ± 1.74 km s−1), we deduced the spin-orbit misalignment to be λ = −121.6 ± 14.4° and I⋆ = 55.9 ± 11.3°. The phase curve is dominated by the reflection effect, with a geometric albedo of 1.58 ± 0.50. We also found evidence that HD 31221 is a δ Scuti/γ Doradus hybrid pulsator. There are three cases for which the 3rd, 85th, and 221st orbital harmonics almost exactly coincide with peaks in the Fourier spectrum of the star, hinting at tidally perturbed stellar oscillations.
Conclusions: HD 31221 b is the third substellar object that is found to be disrupting the pulsations of its host, following HAT-P-2 and WASP-33. Additional photometric observations by CHEOPS and/or PLATO can be used to further constrain its mass and provide a more in-depth analysis of its atmosphere.
Proyectos relacionados
Image withthe projects' name
Exoplanetas y Astrobiología

La búsqueda de vida en el Universo se ha visto impulsada por los recientes descubrimientos de planetas alrededor de otras estrellas (los llamados exoplanetas), convirtiéndose en uno de los campos más activos dentro de la Astrofísica moderna. En los últimos años los descubrimientos cada vez más numerosos de nuevos exoplanetas y los últimos avances

Enric
Pallé Bago