Optical and Infrared Counterparts of the X-Ray Sources Detected in the Chandra Cygnus OB2 Legacy Survey

Guarcello, M. G.; Drake, J. J.; Wright, N. J.; Naylor, T.; Flaccomio, E.; Kashyap, V. L.; García-Alvarez, D.

doi:10.3847/1538-4365/acdd64

Cited by 7 publications

(17 citation statements)

References 54 publications

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“…In the following, we will make use of optical and IR data for our X-ray sources. The cross-identification process and the adopted optical/IR catalogs are described by Guarcello et al (2023b). When using optical/IR data, or derived quantities such as stellar masses, we will only consider the 5418 X-ray sources with a single optical/IR likely counterpart.…”

Section: Data and Sample Selectionmentioning

confidence: 99%

“…The observations and resulting source catalog are described in Wright et al (2023a), with an analysis of the sensitivity and completeness of the observations in Wright et al (2023b). Guarcello et al (2023b) correlate the X-ray catalog with available optical and infrared (IR) photometric catalogs, together with new deep optical photometry. Kashyap et al (2023) exploit the X-ray and optical/IR information to assess the relation of the X-ray sources with the Cyg OB2 region.…”

Section: Introductionmentioning

confidence: 99%

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X-Ray Spectral Characterization of the Young Cygnus OB2 Population

Flaccomio,

Albacete-Colombo,

Drake

et al. 2023

ApJS

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We analyze the X-ray spectra of the ∼8000 sources detected in the Cygnus OB2 Chandra Legacy Survey (this focus issue), with the goals of characterizing the coronal plasma of the young low-mass stars in the region and estimating their intrinsic X-ray luminosities. We adopt two different strategies for X-ray sources for which more or less than 20 photons were detected. For the brighter sample we fit the spectra with absorbed isothermal models. In order to limit uncertainties, for most of the fainter Cygnus OB2 members in this sample we constrain the spectral parameters to characteristic ranges defined from the brightest stars. For X-ray sources with <20 net photons we adopt a conversion factor from detected photon flux to intrinsic flux. This was defined, building on the results for the previous sample, as a function of the 20% quantile of the detected photon energy distributions, which we prove to also correlate well with extinction. We then use the X-ray extinction from the spectral fits to constrain the ratio between optical and X-ray extinction toward Cyg OB2, finding it consistent with standard “Galactic” values, when properly accounting for systematics. Finally, we exploit the large number of sources to constrain the average coronal abundances of several elements, through two different ensemble analyses of the X-ray spectra of low-mass Cyg OB2 members. We find the pattern of abundances to be largely consistent with that derived for the young stellar coronae in the Orion Nebula Cluster.

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Section: Data and Sample Selectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

X-Ray Spectral Characterization of the Young Cygnus OB2 Population

Flaccomio,

Albacete-Colombo,

Drake

et al. 2023

ApJS

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“…An analysis of the sensitivity of our survey to a number of observational and stellar parameters is presented in Wright et al (2023). Optical and infrared counterparts to these sources are presented in Guarcello et al (2023), and an analysis of the likely Cyg OB2 members and contaminants is presented in Kashyap et al (2023). X-ray spectroscopy of the low- (Flaccomio et al 2023) and high-mass (Rauw et al 2015) members of the association is presented elsewhere, along with analysis and discussion.…”

Section: Discussionmentioning

confidence: 99%

“…An analysis of the completeness limits of the survey as a function of various observational and stellar parameters is presented in Wright et al (2023). Other papers in this series present a catalog of optical and near-IR counterparts to the X-ray catalog (Guarcello et al 2023) and an analysis of Cyg OB2 members and contaminants in the X-ray catalog (Kashyap et al 2023).…”

Section: Introductionmentioning

confidence: 99%

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

Wright,

Drake,

Guarcello

et al. 2023

ApJS

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The Cygnus OB2 association is the largest concentration of young and massive stars within 2 kpc of the Sun, including an estimated ∼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 ∼120 ks and an outer 0.35 deg2 area with an exposure of ∼60 ks. Here we describe the survey design and observations, discuss the data reduction and source detection, and present a catalog of ∼8000 X-ray point sources. The survey design employs a grid of 36 heavily (∼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.

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“…For the Chandra Cygnus OB2 Legacy Survey (Guarcello et al 2023a;Wright et al 2023), which is devoted to uncovering the pre-main-sequence (PMS) population of Cyg OB2, the largest group of young stars within 2 kpc of the Sun (Massey & Thompson 1991;Hanson 2003), this issue is further complicated by the observational tiling strategy adopted (see Figure 1 of Wright et al 2023). Compared to other X-ray surveys, where either different pointings do not overlap considerably (e.g., Wright & Drake 2009;Guarcello et al 2012) or the pointings are coaxial but vary in roll angle (e.g., Günther et al 2012), the different observations in our survey are both heavily overlapping and not coaxial.…”

Section: Introductionmentioning

confidence: 99%

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

Wright,

Drake,

Guarcello

et al. 2023

ApJS

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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.

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Optical and Infrared Counterparts of the X-Ray Sources Detected in the Chandra Cygnus OB2 Legacy Survey

Cited by 7 publications

References 54 publications

X-Ray Spectral Characterization of the Young Cygnus OB2 Population

X-Ray Spectral Characterization of the Young Cygnus OB2 Population

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

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

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