X-ray properties of the young open clusters HM1 and IC2944/2948

TL;DR

This study uses XMM data to analyze the X-ray emissions of young open clusters HM1 and IC2944/2948, revealing properties of low-mass pre-main-sequence stars and contrasting behaviors of massive stars, with implications for understanding stellar wind interactions.

Contribution

First X-ray analysis of HM1 and IC2944/2948, highlighting differences in stellar emissions and cluster substructure, with insights into massive star behaviors.

Findings

Detection of low-mass pre-main-sequence stars in both clusters.

Most massive stars show typical high-energy X-ray properties, with lower Lx/Lbol in HM1.

Contrasting X-ray behaviors of Wolf-Rayet stars WR89 and WR87.

Abstract

Using XMM data, we study for the first time the X-ray emission of HM1 and IC2944/2948. Low-mass, pre-main-sequence objects with an age of a few Myr are detected, as well as a few background or foreground objects. Most massive stars in both clusters display the usual high-energy properties of that type of objects, though with log(Lx/Lbol) apparently lower in HM1 than in IC2944/2948. Compared with studies of other clusters, it seems that a low signal-to-noise ratio at soft energies, due to the high extinction, may be the main cause of this difference. In HM1, the two Wolf-Rayet stars show contrasting behaviors: WR89 is extremely bright, but much softer than WR87. It remains to be seen whether wind-wind collisions or magnetically confined winds can explain these emissions. In IC2944/2948, the X-ray sources concentrate around HD101205; a group of massive stars to the north of this object is isolated, suggesting that there exist two subclusters in the field-of-view.