# RV-detected planets around M dwarfs: Challenges for core accretion models

**Authors:** Martin Schlecker, Remo Burn, Silvia Sabotta, Antonia Seifert, Thomas Henning, Alexandre Emsenhuber, Christoph Mordasini, Sabine Reffert, Yutong Shan, Hubert Klahr  
**arXiv:** [2205.12971](https://arxiv.org/abs/2205.12971)  
**Date:** 2022-05-25  
**Summary page:** https://www.summarizepaper.com/en/paper/2205.12971v1/

## Key points

- The article explores the formation of planets around low-mass stars
- Investigates whether known scaling laws can explain observed population of planets or if separate formation channels are required
- State-of-the-art planet population synthesis model is used to test hypothesis
- Simulations reveal that rocky planets around M dwarfs occur at a high frequency and generally agree with their planetary mass function
- Cannot reproduce a population of giant planets around stars less massive than 0.5 solar masses, suggesting an alternative formation channel for these planets
- Stellar mass dependency in the detection rate of short-period planets, indicating dissimilar planet migration barriers in disks of different spectral subtypes
- Lack of close-in planets around earlier-type stars ($M_\star \gtrsim 0.4\, M_\odot$) remains unexplained by their model
- Importance of considering differences in conditions around young stars of different spectral subtypes when studying planet formation
- Gaps in our understanding of planet migration in nascent M dwarf systems need further investigation to fully comprehend how these celestial bodies form

## Summary

This article explores the formation of planets around low-mass stars and investigates whether the observed population of planets can be explained by known scaling laws or if separate formation channels are required. The authors use a state-of-the-art planet population synthesis model to test their hypothesis, which is confronted with a sample of 35 confirmed exoplanets orbiting M dwarf stars from the HARPS and CARMENES radial velocity surveys. To account for detection biases, the authors perform injection and retrieval experiments on actual RV data to produce synthetic observations of planets that they simulate following the core accretion paradigm. The simulations reveal that rocky planets around M dwarfs occur at a high frequency and generally agree with their planetary mass function. However, the simulations cannot reproduce a population of giant planets around stars less massive than 0.5 solar masses, suggesting an alternative formation channel for these planets that cannot be explained by current core accretion theories. Additionally, the authors find a stellar mass dependency in the detection rate of short-period planets, indicating dissimilar planet migration barriers in disks of different spectral subtypes. The paper presents statistical comparisons between observed and simulated samples in minimum mass-period-stellar mass space to show which CARMENES and HARPS planet detections their model can explain. The lack of close-in planets around earlier-type stars ($M_\star \gtrsim 0.4\, M_\odot$) in their sample remains unexplained by their model and indicates gaps in our understanding of planet migration in nascent M dwarf systems. Overall, this study highlights the importance of considering differences in conditions around young stars of different spectral subtypes when studying planet formation. It also underscores gaps in our understanding of planet migration in nascent M dwarf systems that need further investigation to fully comprehend how these celestial bodies form.