# A Volume-Limited Radio Search for Magnetic Activity in 140 Exoplanets with the Very Large Array

**Authors:** Kevin N. Ortiz Ceballos, Yvette Cendes, Edo Berger, Peter K. G. Williams  
**arXiv:** [2404.16940](https://arxiv.org/abs/2404.16940)  
**Date:** 2024-04-25  
**Summary page:** https://www.summarizepaper.com/en/paper/2404.16940v1/

## Key points

- Ortiz Ceballos et al. conducted a study searching for radio emission in 77 stellar systems hosting 140 exoplanets within 17.5 parsecs.
- The investigation utilized the Very Large Array (VLA) at frequencies between 4 to 8 GHz, representing the most extensive exploration for radio signals from exoplanetary systems in the gigahertz range.
- The study focused on exoplanets with masses ranging from about 10^-3 to 10 Jupiter masses and semi-major axes from about 10^-2 to 10 astronomical units.
- GJ 3323, an M4 star, was found to host two exoplanets with minimum masses of 2 and 2.3 Earth masses, displaying a circular polarization fraction of around 40%.
- Stringent upper limits were established for other sources at a significance level of $3\sigma$, generally below $10^{12.5}$ erg s^-1 Hz^-1.
- The findings corroborated previous searches and expanded the sample size under scrutiny, highlighting the importance of future observations using advanced instruments like the Square Kilometer Array and Next Generation Very Large Array.

## Summary

In their study, Ortiz Ceballos et al. present the results of a comprehensive search for radio emission in 77 stellar systems hosting a total of 140 exoplanets, primarily located within 17.5 parsecs. Utilizing the Very Large Array (VLA) at frequencies ranging from 4 to 8 GHz, this investigation represents the most extensive and sensitive exploration to date for radio signals emanating from exoplanetary systems within the gigahertz frequency range. The researchers conducted new observations on 58 systems and analyzed archival data from an additional 19 systems. Their selection of frequency range and volume limit was influenced by previous radio detections of ultracool dwarfs (UCDs), including T dwarfs with masses near the threshold for exoplanet classification (~13 Jupiter masses). The surveyed exoplanets exhibited a mass spectrum spanning approximately 10^-3 to 10 Jupiter masses and semi-major axes ranging from about 10^-2 to 10 astronomical units. Among the observed targets, GJ 3323 (an M4 star) stood out as hosting two exoplanets with minimum masses of 2 and 2.3 Earth masses, displaying a circular polarization fraction of around 40%. While the radio luminosity detected in this system aligned with its known X-ray emissions and adhered to the Gudel-Benz relation for stellar activity—suggesting a probable stellar origin—the notably high circular polarization fraction hinted at potential star-planet interaction phenomena. For the remaining sources, stringent upper limits were established at a significance level of $3\sigma$, generally falling below $10^{12.5}$ erg s^-1 Hz^-1—a comparable range to the lowest radio luminosities observed in UCDs. These findings not only corroborated previous targeted searches focused on individual systems at gigahertz frequencies but also significantly expanded the sample size under scrutiny. The team's sensitivity levels closely matched predicted fluxes for certain systems identified as candidates for observable star-planet interactions, underscoring the importance of future observations using advanced instruments like the Square Kilometer Array and Next Generation Very Large Array to further elucidate emission mechanisms within exoplanetary systems operating at gigahertz frequencies.