The eROSITA extragalactic CalPV serendipitous catalog

TL;DR

This paper presents a catalog of 9515 extragalactic X-ray sources detected during eROSITA's calibration phase, including multiband counterparts, variability analysis, and insights into source populations, providing valuable data ahead of the main sky survey.

Contribution

It introduces a new source detection method optimized for point-like X-ray sources, including extended emission, and provides the first public catalog from eROSITA's CalPV observations with multiband counterparts.

Findings

Catalog contains 9515 X-ray sources with spectral flux measurements.

77% of sources have identified multiband counterparts from CatWISE.

99 sources show significant variability.

Abstract

The eROSITA X-ray telescope on board the Spectrum-Roentgen-Gamma (SRG) observatory performed calibration and performance verification (CalPV) observations between September 2019 and December 2019, ahead of the planned four-year all-sky surveys. Most of them were deep, pointing-mode observations. We present here the X-ray catalog detected from the set of extra-galactic CalPV observations released to the public by the German eROSITA consortium, and the multiband counterparts of these X-ray sources. We developed a source detection method optimized for point-like X-ray sources by including extended X-ray emission in the background measurement. The multiband counterparts were identified using a Bayesian method from the CatWISE catalog. Combining 11 CalPV fields, we present a catalog containing 9515 X-ray sources, whose X-ray fluxes were measured through spectral fitting. CatWISE counterparts are presented for 77% of the sources. Significant variabilities are found in 99 of the sources, which are also presented with this paper. Most of these fields show similar number counts of point sources as typical extragalactic fields, and a few harbor particular stellar populations.