2SXPS: An improved and expanded Swift X-ray telescope point source catalog

TL;DR

The 2SXPS catalog significantly expands the Swift X-ray Telescope source database, introduces new techniques for stray light modeling and source localization, and provides detailed variability data for over 200,000 X-ray sources.

Contribution

This work presents the first application of stray light modeling in X-ray source detection, a new PSF model, and comprehensive variability analysis in the 2SXPS catalog.

Findings

Over 200,000 sources cataloged with variability info.

Stray light modeling reduces spurious detections.

Enhanced source localization and characterization methods.

Abstract

We present the 2SXPS (Swift-XRT Point Source) catalog, containing 206,335 point sources detected by the Swift X-ray Telescope (XRT) in the 0.3--10 keV energy range. This catalog represents a significant improvement over 1SXPS, with double the sky coverage (now 3,790 deg$^2$), and several significant developments in source detection and classification. In particular, we present for the first time techniques to model the effect of stray light -- significantly reducing the number of spurious sources detected. These techniques will be very important for future, large effective area X-ray mission such as the forthcoming Athena X-ray observatory. We also present a new model of the XRT point spread function, and a method for correctly localising and characterising piled up sources. We provide light curves -- in four energy bands, two hardness ratios and two binning timescales -- for every source, and from these deduce that over 80,000 of the sources in 2SXPS are variable in at least one band or hardness ratio. The catalog data can be queried or downloaded via a bespoke web interface at https://www.swift.ac.uk/2SXPS, via HEASARC, or in Vizier (IX/58).