Einstein IPC Ultrasoft Sources Catalog: 516 Objects with Soft X-ray Emission

A 1999 catalog from NASA HEASARC containing 516 astrophysical objects selected for strong ultrasoft X-ray emission from the Einstein IPC database of 5934 sources. Selection was based on X-ray 'color' ratios from three broad energy bands, with identified objects including active galactic nuclei, stellar objects, and Galactic sources. The catalog was created by the HEASARC based on tables provided to the CDS/ADC.

Use Cases

• Classifying astrophysical objects based on ultrasoft X-ray emission criteria described in the survey.
• Analyzing the distribution of X-ray 'colors' (C1, C2, C3 band ratios) for spectral modeling.
• Correlating identified ultrasoft sources (45% AGN, 28% stellar) with other astronomical databases.
• Studying the population of 'nonstellar' Galactic objects like cataclysmic variables and white dwarfs in soft X-rays.

Strengths

• Contains 516 specifically selected objects from a parent database of 5934 sources, providing a focused sample.
• 39% of objects (202) have been identified through correlations with other databases, adding context.
• Selection criteria (C1>0, R1<0.36) are explicitly defined and linked to physical spectral models.

Limitations

• Column-level documentation is absent; field semantics must be inferred after download.
• Row count is unknown, which may limit suitability assessment.
• Data may reflect temporal bias inherent to the original Einstein IPC survey period.

Provenance

Source

NASA HEASARC, based on tables from catalog authors to the CDS/ADC.

Collection Method

Survey of the Einstein IPC database using X-ray color ratio selection criteria.

Time Range

Based on the Einstein IPC database; specific observation dates are not provided.

Freshness

Last updated 2026-03-13 19:56:34.142930; freshness should be verified.

Geography

Astrophysical objects across the sky; no specific geographic coverage.