Einstein Two-Sigma Catalog: X-ray Sources from HEAO-2

46,000 X-ray source detections from the Einstein Observatory (HEAO-2) Imaging Proportional Counter, compiled by NASA HEASARC. The catalog covers 1850 square degrees of the sky, excluding regions with diffuse emission like the galactic plane and bright clusters. According to the authors, only about 13,000 (28%) of the listed sources are estimated to be real astrophysical objects, with the remainder being spurious.

Use Cases

• Statistical analysis of X-ray source populations based on 2-sigma intensity thresholds.
• Cross-correlation with other catalogs to identify probable real sources, as suggested by the authors.
• Studying the spatial distribution of faint X-ray sources across 1850 square degrees of sky.
• Investigating the characteristics of spurious detections in X-ray astronomy surveys.

Strengths

• Covers 1850 square degrees of the sky, providing a large survey area.
• Contains 46,000 source detections, offering a substantial sample for analysis.
• Explicitly documents the estimated 28% real source rate, providing clear context for data quality.

Limitations

• By design, the catalog contains a significant number of spurious sources; only an estimated 13,000 are real.
• Column-level documentation is absent; field semantics must be inferred after download.
• Row count is unknown, which may limit suitability assessment.

Provenance

Source

NASA HEASARC, based on Einstein Observatory (HEAO-2) data.

Collection Method

Compiled from observations made with the Imaging Proportional Counter (IPC).

Freshness

Last updated 2026-03-13 17:14:09.527347; freshness should be verified.

Geography

Covers 1850 sq. degrees of the sky, excluding regions within 10 degrees of the galactic plane, the Magellanic Clouds, and crowded fields like Orion and Pleiades.