Searching for close-in planets around TWA 7 with SPIRou

¹ Univ. de Toulouse, CNRS, IRAP, 14 avenue Belin, 31400 Toulouse, France
² Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
³ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
⁴ Departamento de Física – ICEx – UFMG, Av. Antônio Carlos, 6627, 30270-901 Belo Horizonte, MG, Brazil

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 19 September 2025
Accepted: 19 November 2025

Abstract

We outline in this paper observations of the young pre-main-sequence low-mass star TWA 7 hosting a debris disk and a distant planet. Using data collected with the near-infrared SPIRou spectropolarimeter and precision velocimeter at the Canada-France-Hawaii Telescope from early 2019 to mid 2021, we detected the magnetic field of TWA 7 from the circularly polarized Zeeman signatures and Zeeman broadening of atomic spectral lines and the rotational modulation of its longitudinal component at the known stellar rotation period (of 5.012 ± 0.007 d). We then modeled the large-scale and small-scale magnetic properties of TWA 7 using Zeeman-Doppler imaging. We find that TWA 7 hosted a mainly poloidal field that significantly evolved from 2019 to 2021 and that the dipole component became stronger (increasing from 0.5 kG in 2019 to 0.7 kG in 2021) and less inclined to the stellar rotation axis (from 22^° in 2019 to 15^° in 2021). We also analyzed the radial velocities of TWA 7 derived from the SPIRou data and found a tentative planet signature at a period of 15.2 d (with aliases at 20.8 and 30.4 d), which is very close to the detection limit of our data and would correspond to a 0.17 M_♃ planet at a distance of 0.09 au if confirmed. Finally, we report that the 1083 nm He I and 1282 nm Paβ lines of TWA 7 are modulated with a period of 6.6 d, different from the rotation period. This potentially hints at the presence of a close-in planet triggering star-planet interactions.