Coronae in the Coronet: A very deep X-ray look into a stellar nursery

TL;DR

This study uses deep Chandra X-ray observations to analyze the X-ray properties of young stellar objects in the Coronet cluster, revealing their coronal activity, variability, and some diffuse emission, with implications for stellar evolution.

Contribution

It provides one of the most sensitive X-ray datasets for a star-forming region, enabling detailed analysis of YSO X-ray properties and their relation to evolutionary stages.

Findings

X-ray emission detected from all known late-type cluster members.

Diffuse X-ray emission observed near R CrA / IRS 7.

X-ray properties consistent with coronal activity, no accretion shock signatures.

Abstract

In order to study the X-ray properties of young stellar objects (YSOs), we analyze an exceptionally sensitive Chandra dataset of the Coronet cluster in the CrA star-forming region, achieving a limiting luminosity of LXmin=5E26 erg/sec for lightly absorbed sources. This dataset represents one of the most sensitive X-ray observations ever obtained of a star-forming region. The X-ray data are used to investigate the membership status of tentative members of the region, to derive plasma temperatures and X-ray luminosities of the YSOs, and to investigate variability on the timescale of several years. 46 of the 92 X-ray sources in the merged Chandra image can be identified with optical or near/mid-infrared counterparts. X-ray emission is detected from all of the previously known optically visible late-type (spectral types G to M) stellar cluster members, from five of the eight brown dwarf candidates, and from nine embedded objects ("protostars") with class 0, class I, or flat-spectrum SEDs in the field of view. While the Herbig Ae/Be stars TY CrA and R CrA, a close companion of the B9e star HD 176386, and the F0e star T CrA are detected, no X-ray emission is found from any of the Herbig-Haro (HH) objects or the protostellar cores without infrared source. We find indications for diffuse X-ray emission near R CrA / IRS 7. The observed X-ray properties of the Coronet YSOs are consistent with coronal activity; no soft spectral components hinting towards X-ray emission from accretion shocks were found. The X-ray emission of the AeBe stars TY CrA and HD 176386 originates probably from close late-type companions. The Ae star R Cra shows a peculiar X-ray spectrum and an extremely hot plasma temperature. Finally, we discuss the differences of the X-ray properties of YSOs in different evolutionary stages.