TOI-2407 b: a warm Neptune in the desert

TL;DR

This paper reports the validation of TOI-2407 b, a warm Neptune-sized exoplanet orbiting an M-type star, highlighting the use of CMOS infrared detectors for improved exoplanet detection and characterization.

Contribution

It introduces the validation of a Neptune-sized planet within the Neptune desert using novel CMOS-based infrared observations, demonstrating their potential in exoplanet studies.

Findings

TOI-2407 b has a radius of 4.26 R⊕ and orbits its star every 2.7 days.

The planet lies within the Neptune desert, an area of scarcity for such planets.

CMOS detectors show promise for infrared exoplanet detection and characterization.

Abstract

We present the validation of TOI-2407 b, a warm Neptune-sized planet with a radius of 4.26 $\pm$ 0.26 R$_\oplus$, orbiting an early M-type star with a period of 2.7 days and an equilibrium temperature of 705 $\pm$ 12 K. The planet was identified by TESS photometry and validated in this work through multi-wavelength ground-based follow-up observations. We include an observation with the novel CMOS-based infrared instrument SPIRIT at the SPECULOOS Southern Observatory. The high-precision transit data enabled by CMOS detectors underscore their potential for improving the detection and characterisation of exoplanets orbiting M-dwarfs, particularly in the infrared, where these stars emit most of their radiation. TOI-2407 b lies within the boundaries of the period-radius Neptune desert, an apparent scarcity of Neptune-sized planets at short orbits. Further characterisation of TOI-2407 b, such as radial velocity measurements, will refine its position within planetary demographic trends. This system also provides a comparison case for the well-studied Neptune-sized planet Gliese 436 b, of similar radius, period and stellar type. Comparison studies could aid the understanding of the formation and evolution of Neptune-like planets around M-dwarfs.