TOI-1452 b: SPIRou and TESS reveal a super-Earth in a temperate orbit transiting an M4 dwarf

TL;DR

This paper reports the discovery and characterization of TOI-1452 b, a temperate super-Earth orbiting an M4 dwarf, with detailed measurements suggesting a rocky core and volatile-rich envelope, making it a promising target for atmospheric studies.

Contribution

First detailed characterization of TOI-1452 b, combining TESS photometry and SPIRou velocimetry, revealing its composition and potential for atmospheric exploration.

Findings

TOI-1452 b is a super-Earth with 1.67 R⊕ and 4.8 M⊕ in a 11.1-day orbit.

The planet has a bulk density of approximately 5.6 g/cm³, indicating a rocky core with volatiles.

It is a prime target for JWST atmospheric studies due to its favorable properties.

Abstract

Exploring the properties of exoplanets near or inside the radius valley provides insights on the transition from the rocky super-Earths to the larger, hydrogen-rich atmosphere mini-Neptunes. Here, we report the discovery of TOI-1452 b, a transiting super-Earth ($R_{\rm p} = 1.67 \pm 0.07$ R$_{\oplus}$) in an 11.1--day temperate orbit ($T_{\rm eq} = 326 \pm 7$ K) around the primary member ($H = 10.0$, $T_{\rm eff} = 3185 \pm 50$ K) of a nearby visual binary M dwarf. The transits were first detected by TESS, then successfully isolated between the two $3.2^{\prime\prime}$ companions with ground-based photometry from OMM and MuSCAT3. The planetary nature of TOI-1452 b was established through high-precision velocimetry with the near-infrared SPIRou spectropolarimeter as part of the ongoing SPIRou Legacy Survey. The measured planetary mass ($4.8 \pm 1.3$ M$_{\oplus}$) and inferred bulk density ($5.6^{+1.8}_{-1.6}$ g/cm$^3$) is suggestive of a rocky core surrounded by a volatile-rich envelope. More quantitatively, the mass and radius of TOI-1452 b, combined with the stellar abundance of refractory elements (Fe, Mg and Si) measured by SPIRou, is consistent with a core mass fraction of $18\pm6$ % and a water mass fraction of $22^{+21}_{-13}$%. The water world candidate TOI-1452 b is a prime target for future atmospheric characterization with JWST, featuring a Transmission Spectroscopy Metric similar to other well-known temperate small planets such as LHS 1140 b and K2-18 b. The system is located near Webb's northern Continuous Viewing Zone, implying that is can be followed at almost any moment of the year.