M 31 Central Region: Chandra X-Ray Point Source Catalog

The central region of the M 31 (Andromeda) galaxy contains 204 X-ray point sources identified from eight Chandra ACIS-I observations taken between 1999 and 2001. The catalog, created by the HEASARC in October 2004, includes classifications for 22 globular clusters, two supernova remnants, nine planetary nebulae, and nine supersoft sources. A detection limit of ~2x10^35 erg/s was applied, and about 50% of sources were found to be variable on timescales of months.

Use Cases

• Analyzing X-ray source variability based on the finding that about 50% of sources vary on monthly timescales.
• Classifying celestial objects based on identified source types like globular clusters, supernova remnants, and planetary nebulae.
• Studying transient X-ray events based on the 13 transients with varied light curve shapes mentioned in the description.
• Modeling X-ray spectra based on the power-law fits for the 20 brightest sources with a mean photon index of 1.8.
• Investigating source detection sensitivity across a field based on described variations in exposure time, background, and instrumental PSF.

Strengths

• Contains 204 distinct X-ray point sources with a signal-to-noise ratio (S/N) > 2.5 for all entries.
• Includes multi-epoch observations from 1999 to 2001, enabling variability analysis.
• Provides source classifications for 42 objects, including globular clusters and supernova remnants.
• Spectra for the 20 brightest sources are described as well-fitted by a power law.

Limitations

• Column-level documentation is absent; field semantics must be inferred after download.
• Row count is known (204), but the specific features per row are unknown from the provided metadata.
• Additional optical identifications and cross-correlated ROSAT sources are not in this table but in separate published files.

Provenance

Source

NASA HEASARC, based on CDS Catalog J/ApJ/577/738/table2.

Collection Method

Combined analysis of eight Chandra ACIS-I observations.

Time Range

Observations taken between 1999 and 2001.

Freshness

Last updated 2026-03-13 17:11:42.734571; freshness should be verified.

Geography

Central ~17'x17' region of the M 31 (Andromeda) galaxy.