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Simulating the Sensitivity to Stellar Point Sources of Chandra X-Ray Observations

Wright, Nicholas J.; Drake, Jeremy J.; Guarcello, Mario G.; Kashyap, Vinay L.; Zezas, Andreas


Jeremy J. Drake

Mario G. Guarcello

Vinay L. Kashyap

Andreas Zezas


The Chandra Cygnus OB2 Legacy Survey is a wide and deep X-ray survey of the nearby and massive Cygnus OB2 association. The survey has detected ∼8000 X-ray sources, the majority of which are pre-main-sequence X-ray-emitting young stars in the association itself. To facilitate quantitative scientific studies of these sources, as well as the underlying OB association, it is important to understand the sensitivity of the observations and the level of completeness the observations have obtained. Here we describe the use of a hierarchical Monte Carlo simulation to achieve this goal by combining the empirical properties of the observations, analytic estimates of the source verification process, and an extensive set of source detection simulations. We find that our survey reaches a 90% completeness level for a pre-main-sequence population at the distance of Cyg OB2 at an X-ray luminosity of 4 × 1030 erg s−1 and a stellar mass of 1.3 M ⊙ for a randomly distributed population. For a spatially clustered population such as Cyg OB2 the 90% completeness level is reached at 1.1 M ⊙ instead, as the sources are more concentrated in areas of our survey with a high exposure. These simulations can easily be adapted for use with other X-ray observations and surveys, and we provide X-ray detection efficiency curves for a very wide array of source and background properties to allow these simulations to be easily exploited by other users.

Journal Article Type Article
Acceptance Date Feb 2, 2017
Online Publication Date Oct 25, 2023
Publication Date Nov 1, 2023
Deposit Date Oct 30, 2023
Publicly Available Date Oct 30, 2023
Journal The Astrophysical Journal Supplement Series
Print ISSN 0067-0049
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 269
Issue 1
Article Number 8
Keywords Pre-main sequence stars, X-ray stars


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Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

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