The Perkins INfrared Exosatellite Survey (PINES) II. Transit Candidates and Implications for Planet Occurrence around L and T Dwarfs

TL;DR

This paper introduces a new transit detection algorithm for L and T dwarfs, reports two candidates, and discusses implications for planet occurrence rates around these objects, potentially challenging existing planet formation theories.

Contribution

The paper presents a novel transit detection algorithm tailored for discontinuous infrared observations and applies it to identify candidate planets around L and T dwarfs, with implications for planet occurrence rates.

Findings

Identified two transit candidates in PINES data.

Estimated planet radii between 4.2 and 5.8 Earth radii.

Detection rates suggest possible higher occurrence of short-period planets around L and T dwarfs.

Abstract

We describe a new transit detection algorithm designed to detect single transit events in discontinuous Perkins INfrared Exosatellite Survey (PINES) observations of L and T dwarfs. We use this algorithm to search for transits in 131 PINES light curves and identify two transit candidates: 2MASS J18212815+1414010 (2MASS J1821+1414) and 2MASS J08350622+1953050 (2MASS J0835+1953). We disfavor 2MASS J1821+1414 as a genuine transit candidate due to the known variability properties of the source. We cannot rule out the planetary nature of 2MASS J0835+1953's candidate event and perform follow-up observations in an attempt to recover a second transit. A repeat event has yet to be observed, but these observations suggest that target variability is an unlikely cause of the candidate transit. We perform a Markov chain Monte Carlo simulation of the light curve and estimate a planet radius ranging from $4.2^{+3.5}_{-1.6}R_\oplus$ to $5.8^{+4.8}_{-2.1}R_\oplus$, depending on the host's age. Finally, we perform an injection and recovery simulation on our light curve sample. We inject planets into our data using measured M dwarf planet occurrence rates and attempt to recover them using our transit search algorithm. Our detection rates suggest that, assuming M dwarf planet occurrence rates, we should have roughly a 1$\%$ chance of detecting a candidate that could cause the transit depth we observe for 2MASS J0835+1953. If 2MASS J0835+1953 b is confirmed, it would suggest an enhancement in the occurrence of short-period planets around L and T dwarfs in comparison to M dwarfs, which would challenge predictions from planet formation models.