BANYAN. X. Discovery of a wide, low-gravity L-type companion to a fast-rotating M3 dwarf

TL;DR

This paper reports the discovery of a wide, low-gravity L-type substellar companion to a young M3 dwarf, using astrometry and spectroscopy, contributing to understanding of young planetary-mass objects in stellar groups.

Contribution

It presents the first identification of a wide, low-gravity L-type companion to an M3 dwarf in the AB Doradus Moving Group, expanding knowledge of young substellar companions.

Findings

Companion mass estimated at 30 Mj with uncertainties.

Confirmed co-moving status through follow-up astrometry and spectroscopy.

System is a spatial outlier within the AB Doradus Moving Group.

Abstract

We report the discovery of a substellar-mass co-moving companion to 2MASS J22501512+2325342, an M3 candidate member of the young (130--200 Myr) AB Doradus Moving Group (ABDMG). This L3 beta companion was discovered in a 2MASS search for companions at separations of 3--18" from a list of 2 812 stars suspected to be young (< 500 Myr) in the literature, and was confirmed with follow-up astrometry and spectroscopy. Evolutionary models yield a companion mass of 30 (-4,+11) Mj at the age of ABDMG. The 2MASS J22501512+2325342 AB system appears to be a spatial outlier to the bulk of ABDMG members, similarly to the young 2MASS J22362452+4751425 AB system. Future searches for young objects around these two systems would make it possible to determine whether they are part of a spatial extension of the known ABDMG distribution.