The Corona-Australis star-forming region: New insights on its formation history from detailed stellar and disk analysis

TL;DR

This study investigates the formation history of the Corona Australis star-forming region through detailed analysis of stellar populations, disks, and multiplicity, revealing a complex sequence of events influenced by supernova explosions over the past 18 million years.

Contribution

It provides a new, detailed formation scenario for the Corona Australis complex based on stellar ages, spatial configurations, and supernova triggers, refining previous models.

Findings

CrA-Main is approximately 3 million years old and still gas-bound.

CrA-North is about 6.7 million years old and expanding.

Star formation was triggered by supernova explosions in the past.

Abstract

The star-forming complex of Corona Australis (CrA) is one of the closest and most isolated molecular clouds. It belongs to a chain of clusters that show age gradients with distance from the galactic plane. We aim to provide suggestions regarding its formation history by examining the stellar and disk populations, stellar multiplicity, and interstellar absorption. We made a census of stars and disks using Gaia DR3 and infrared data. Interstellar absorption in the direction of each star was derived by comparing SpTy from the literature and Gaia colors. Stellar multiplicity analysis accounts for both direct observation of visual companions (Gaia data and high-contrast imaging) and indirect detection of the presence of companions (eclipsing and spectroscopic binaries, and astrometry). The properties of the disks were obtained from the slopes of the spectral energy distributions. As found in previous studies, the CrA complex can be divided into two regions: a younger region (CrA-Main: 3+/-1Myr) and an older one (CrA-North: 6.7+/-0.3Myr), slightly younger than previously thought. While CrA-Main still appears bound to the gas, CrA-North is unbound and expanding. The stars that belong to CrA-North were in the most compact configuration 3.72Myr ago. At that time, CrA-Main and CrA-North were much closer to each other than they appear now. The fraction of disk-bearing stars is higher in Main than in North, as also expected due to the younger age of CrA-Main. We propose a formation history scenario for the CrA-complex. It started between 15 and 18 Myr ago with SNe explosions in the Upper Centaurus-Lupus complex, followed by a quiescent phase with little star formation. A star formation episode about 7Myr ago formed CrA-North stars. About 3.7Myr ago, a second SN explosion south of CrA-North triggered star formation in CrA-Main. This last SN might have been the origin of the pulsar RX J1856.5-3754.