Related papers: The Structure of the Young Star Cluster NGC 6231. …
NGC6231 is a massive young star cluster, near the center of the Sco OB1 association. While its OB members are well studied, its low-mass population has received little attention. We present high-spatial resolution Chandra ACIS-I X-ray data,…
The young cluster NGC 6231 (stellar ages ~2-7 Myr) is observed shortly after star-formation activity has ceased. Using the catalog of 2148 probable cluster members obtained from Chandra, VVV, and optical surveys (Paper I), we examine the…
The low-mass members of OB associations, expected to be a major component of their total population, are in most cases poorly studied because of the difficulty of selecting these faint stars in crowded sky regions. Our knowledge of many OB…
In this second paper, we pursue the analysis of the 180 ks XMM-Newton campaign towards the young open cluster NGC 6231 and we focus on its rich OB star population. We present a literature-based census of the OB stars in the field of view…
Considered as the core of the Sco OB1 association, the young open cluster NGC 6231 harbours a rich O-type star population. In 2001, the XMM-Newton satellite targeted the cluster for a nominal duration of about 180 ks. Thanks to the detector…
We present the results of a long-term high-resolution spectroscopy campaign on the O-type stars in NGC 6231. We revise the spectral classification and multiplicity of these objects and we constrain the fundamental properties of the O-star…
Based on a deep XMM-Newton observation of the young open cluster NGC 6231, we derive the main X-ray properties of its early-type star population. Among the 610 X-ray sources detected in the field, 42 are associated with early-type stars. We…
We characterize the stellar population of the poorly explored young stellar cluster NGC 3293 at the northwestern periphery of the Carina Nebula Complex, in order to evaluate the cluster age and the mass function, and to test claims of an…
We present the first high spatial resolution Chandra X-ray study of NGC 2244, the 2 Myr old stellar cluster immersed in the Rosette Nebula. Over 900 X-ray sources are detected; 77% have optical or FLAMINGOS near-infrared (NIR) stellar…
The full stellar population of NGC 6334, one of the most spectacular regions of massive star formation in the nearby Galaxy, have not been well-sampled in past studies. We analyze here a mosaic of two Chandra X-ray Observatory images of the…
It is well known that massive O-stars are frequently (if not always) found in binary or higher-order multiple systems, but this fact has been less robustly investigated for the lower mass range of the massive stars, represented by the…
Open clusters belonging to star-forming complexes are the leftovers from the initial stellar generations. The study of these young systems provides constraints to models of star formation and evolution as well as to the properties of the…
This paper is the first of a series dedicated to the X-ray properties of the young open cluster NGC 6231. Our data set relies on an XMM-Newton campaign of a nominal duration of 180 ks and reveals that NGC 6231 is very rich in the X-ray…
NGC 2264 is a young Galactic cluster and the dominant component of the Mon OB1 association lying approximately 760 pc distant within the local spiral arm. The cluster is hierarchically structured, with subclusters of suspected members…
We present an updated catalog of 1300 objects in the field of M31, including 670 likely star clusters of various types. Archival images were inspected to confirm cluster classifications where possible, but most of the classifications were…
We present and discuss photometric optical data in the area of the OB association Sco OB1 covering about 1 squared degree. UBVI photometry is employed in tandem with Gaia DR2 data to investigate the 3 dimensional structure and the star…
We discuss the properties of the X-ray sources with faint optical counterparts in the very young open cluster NGC 6231. From their positions in the H-R diagram, we find that the bulk of these objects probably consists of low-mass pre-main…
Recent evolutionary computations predict that a few percent of massive OB stars in binary systems should have a dormant BH companion. Despite several reported X-ray quiet OB+BH systems over the last couple of years, finding them with…
We present Chandra X-ray images of the NGC 2237 young star cluster on the periphery of the Rosette Nebula. We detect 168 X-ray sources, 80% of which have counterparts in USNO, 2MASS, and deep FLAMINGOS images. These constitute the first…
By studying young open clusters, the mechanisms important for star formation over several Myr can be examined. For example, accretion rate as a function of rotational velocity can be investigated. Similarly, sequential star formation…