Searching for Faint Comoving Companions to the $\alpha$ Centauri system in the VVV Survey Infrared Images

TL;DR

This study used infrared VVV survey data to search for faint, wide-orbit companions around alpha Centauri, finding none and setting new upper limits on possible companion masses and temperatures.

Contribution

First to utilize VVV survey data to place stringent limits on faint, wide companions to alpha Centauri in the infrared, extending previous constraints.

Findings

No new companions detected around alpha Centauri.

Companions warmer than 325K and above 11 Jupiter masses are ruled out.

Limits extend to projected distances of 7,000 AU from alpha Centauri.

Abstract

The VVV survey has observed the southern disk of the Milky Way in the near infrared, covering 240 deg$^{2}$ in the $ZYJHK_S$ filters. We search the VVV Survey images in a $\sim$19 deg$^{2}$ field around $\alpha$ Centauri, the nearest stellar system to the Sun, to look for possible overlooked companions that the baseline in time of VVV would be able to uncover. The photometric depth of our search reaches $Y\sim$19.3 mag, $J\sim$19 mag, and $K_S\sim$17 mag. This search has yielded no new companions in $\alpha$ Centauri system, setting an upper mass limit for any unseen companion well into the brown dwarf/planetary mass regime. The apparent magnitude limits were turned into effective temperature limits, and the presence of companion objects with effective temperatures warmer than 325K can be ruled out using different state-of-the-art atmospheric models. These limits were transformed into mass limits using evolutionary models, companions with masses above 11 M$_{Jup}$ were discarded, extending the constraints recently provided in the literature up to projected distances of d<7 000 AU from $\alpha$ Cen AB and $\sim$1200 AU from Proxima. In the next few years, the VVV extended survey (VVVX) will allow to extend the search and place similar limits on brown dwarfs/planetary companions to $\alpha$ Cen AB for separations up to 20 000AU.