NGC 6231: Chandra X-Ray and Infrared Catalog of Young Stellar Cluster Members

A 2005 Chandra X-ray observation combined with multi-epoch VISTA near-infrared photometry provides a catalog of 2148 probable stellar members in the young cluster NGC 6231. This catalog, which is 70% larger than previous censuses, includes low-mass stars and B stars with newly identified X-ray counterparts. The work estimates a total population of 5700-7500 members down to 0.08 solar masses within the Chandra field.

Use Cases

• Study stellar X-ray luminosity evolution by comparing data from this ~2-7 Myr cluster with younger clusters.
• Identify pre-main-sequence stars based on near-infrared variability, with about half of the 295 NIR variables expected to be such stars.
• Distinguish X-ray generation mechanisms in B stars by analyzing X-ray spectral hardness mentioned in the description.
• Investigate the effects of circumstellar disks by examining members with unusually high X-ray median energies or reddened NIR colors.

Strengths

• Catalog contains 2148 probable cluster members, representing a 70% increase over previous censuses.
• Integrates multi-wavelength data from Chandra X-ray, VISTA near-infrared, and optical catalogs.
• Provides an estimated total population range of 5700-7500 members down to 0.08 solar masses.

Limitations

• Column-level documentation is absent; field semantics must be inferred after download.
• Row count is unknown, which may limit suitability assessment.
• Completeness limit is noted at 0.5 solar masses, with lower-mass estimates based on an assumed universal initial mass function.

Provenance

Source

National Aeronautics and Space Administration

Collection Method

Reanalysis of archival Chandra ACIS-I data from 2005 combined with VISTA Variables in the Via Lactea (VVV) survey near-infrared photometry.

Time Range

Observations from 2005 July (Chandra), with near-infrared data from the multi-epoch VVV survey.

Freshness

Last updated 2026-03-13 17:12:57.397990; freshness should be verified.

Geography

Target is the NGC 6231 star cluster in the Sco OB1 association at a distance of approximately 1.59 kiloparsecs.