The Chandra Cygnus OB2 Legacy Survey: Design and X-Ray Point-source Catalog

The Cygnus OB2 association is the largest concentration of young and massive stars within 2 kpc of the Sun, including an estimated similar to 65 O-type stars and hundreds of OB stars. The Chandra Cygnus OB2 Legacy Survey is a large imaging program undertaken with the Advanced CCD Imaging Spectrometer on board the Chandra X-ray Observatory. The survey has imaged the central 0.5 deg2 of the Cyg OB2 association with an effective exposure of similar to 120 ks and an outer 0.35 deg2 area with an exposure of similar to 60 ks. Here we describe the survey design and observations, discuss the data reduction and source detection, and present a catalog of similar to 8000 X-ray point sources. The survey design employs a grid of 36 heavily (similar to 50%) overlapping pointings, a method that overcomes Chandra's low off-axis sensitivity and produces a highly uniform exposure over the inner 0.5 deg2. The full X-ray catalog is described here and is made available online.

Automated summary

The Cygnus OB2 association is a major concentration of young and massive stars near the Sun, and a Chandra X-ray Observatory survey has provided a catalog of 8000 X-ray point sources. The survey design utilized a grid of overlapping pointings to overcome low off-axis sensitivity.