J/ApJS/269/7 Chandra Cygnus OB2 Legacy Survey: X-ray Catalog (Wright+ 2023)
The Chandra Cygnus OB2 Legacy Survey: Design and X-ray Point Source Catalog.
Wright N.J., Drake J.J., Guarcello M.G., Aldcroft T.L., Kashyap V.L.,
Damiani F., DePasquale J., Fruscione A.
<Astrophys. J. Suppl. Ser. 269, 7 (2023)>
=2023ApJS..269....7W 2023ApJS..269....7W (SIMBAD/NED BibCode)
ADC_Keywords: Associations, stellar ; X-ray sources
Keywords: open clusters and associations: individual: Cygnus OB2 -
stars: pre-main sequence - X-rays: stars
Abstract:
The Cygnus OB2 association is the largest concentration of young and
massive stars within 2kpc 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 onboard the Chandra X-ray Observatory. The survey
has imaged the central 0.5deg2 of the Cyg OB2 association with an
effective exposure of 120ks and an outer 0.35 deg2 area with an
exposure of 60ks. Here we describe the survey design and observations,
the data reduction and source detection, and present a catalog of
8,000 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 0.5deg2. The full X-ray catalog is described
here and is made available online.
Description:
X-ray detections, broad-band fluxes and mean energies for 7924 sources
towards the Cygnus OB2 association.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 353 7924 Chandra Cygnus OB2 Legacy Survey Catalog
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See also:
J/ApJS/149/123 : WSRT survey of Cygnus OB2 (Setia Gunawan+, 2003)
J/A+A/464/211 : Chandra & near-IR obs. of Cyg OB2 (Albacete Colombo+, 2007)
J/A+A/472/557 : Cygnus OB2 region 610MHz sources (Marti+, 2007)
J/A+A/474/495 : X-ray flares from Cygnus OB2 young stars
(Albacete Colombo+, 2007)
J/ApJS/184/84 : X-ray sources in Cyg OB2 region (Wright+, 2009)
J/MNRAS/460/2593 : Cygnus OB2 DANCe: Proper motion study (Wright+, 2016)
J/MNRAS/502/6080 : New members of Cygnus OB2 from Gaia DR2 (Orellana+, 2021)
J/A+A/637/A64 : Cygnus OB2 e-MERLIN 21cm survey (COBRaS) (Morford+, 2020)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Number [1/7924] X-ray source number within the
Chandra Cygnus OB2 Legacy Survey
6- 32 A27 --- Name IAU source name,
CXOCOB2 JHHMMSS.ss+DDMMSS.s
34- 43 F10.6 deg RAdeg Right ascension (J2000.0)
45- 53 F9.6 deg DEdeg Declination (J2000.0)
55- 59 F5.3 arcsec PosErr 1 sigma error circle around source position
61- 74 A14 --- PosType Method used to estimate source position (1)
76 I1 --- SusFlag [0] Flag indicating the source is close to
known PSF feature (2)
78- 82 F5.1 --- Signif Source significance (from full band)
84- 88 F5.2 --- PrbNoSrc Base 10 logarithm of the p-value for
no-source null hypothesis
90- 93 A4 --- PrbBand Band used for PrbNoSrc (3)
95 I1 --- DetMeth [0/5] Method used for detecting the
candidate source (4)
97-104 F8.1 s ExpTmTot Total exposure time in all observations
106-113 F8.1 s ExpTmNom Exposure time in all merged observations
used for photometry
115-120 F6.4 --- ExpTmFra Fration of ExpTmTot used for photometry
122-123 I2 --- NumObTot Total number of observations of the source
125-126 I2 --- NumObNom Number of observations of the source merged
for photometry
128-132 F5.2 arcmin b_Theta Smallest off-axis angle for merged
observations
134-138 F5.2 arcmin Theta Average off-axis angle for merged
observations
140-144 F5.2 arcmin B_Theta Largest off-axis angle for merged
observations
146-150 F5.3 --- PSFFrac Average PSF fraction (at 1.5keV) for merged
observations
152-155 I4 pix+2 SrcArea Average aperture area for merged
observations
157-162 F6.4 --- ProbKSs Smallest p-value for the non-variable null
hypothesis from a single observation
164-169 F6.4 --- ProbKSm Smallest p-value for the non-variable null
hypothesis from all merged observations
171-175 I5 ct SCntFull Observed counts in merged source apertures
(full band)
177-181 I5 ct SCntSoft Observed counts in merged source apertures
(soft band)
183-187 I5 ct SCntHard Observed counts in merged source apertures
(hard band)
189-193 I5 ct BCntFull Observed counts in merged background
regions (full band)
195-199 I5 ct BCntSoft Observed counts in merged background
regions (soft band)
201-205 I5 ct BCntHard Observed counts in merged background
regions (hard band)
207-212 F6.1 --- BkgScale Scaling of the background extraction region
214-221 F8.2 ct NCntFull Net counts in merged source apertures
(full band)
223-230 F8.2 ct NCntSoft Net counts in merged source apertures
(soft band)
232-239 F8.2 ct NCntHard Net counts in merged source apertures
(hard band)
241-245 F5.1 10-7J/cm2/ph ARFFull Mean ARF value (full band)
(in erg/cm2/ph) (5)
247-251 F5.1 10-7J/cm2/ph ARFSoft Mean ARF value (soft band)
(in erg/cm2/ph) (5)
253-257 F5.1 10-7J/cm2/ph ARFHard Mean ARF value (hard band)
(in erg/cm2/ph) (5)
259-262 F4.2 keV MedEFull Median energy of the observed spectrum
(full band)
264-267 F4.2 keV MedESoft ? Median energy of the observed spectrum
(soft band)
269-272 F4.2 keV MedEHard ? Median energy of the observed spectrum
(hard band)
274-281 E8.2 mW/m2 FluxFull Energy flux of the observed spectrum
(full band) (in erg/cm2/s)
283-290 E8.2 mW/m2 FluxSoft ? Energy flux of the observed spectrum
(soft band) (in erg/cm2/s)
292-299 E8.2 mW/m2 FluxHard ? Energy flux of the observed spectrum
(hard band) (in erg/cm2/s)
301-308 F8.2 ct b_NCntFull 1 sigma lower bound on NCntFull
310-317 F8.2 ct B_NCntFull 1 sigma upper bound on NCntFull
319-326 F8.2 ct b_NCntSoft ? 1 sigma lower bound on NCntSoft
328-335 F8.2 ct B_NCntSoft 1 sigma upper bound on NCntSoft
337-344 F8.2 ct b_NCntHard ? 1 sigma lower bound on NCntHard
346-353 F8.2 ct B_NCntHard 1 sigma upper bound on NCntHard
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Note (1): Methods used to estimate source position include "correlation", "mean
data" and "reconstruction". See Section 4.1.4 for more details.
Note (2): Flag as follows (See Section 4.2 for more details):
1 = the source is coincident with the known PSF feature
0 = the source is not coincident with the known PSF feature
Note (3): Bands include "full", "soft" and "hard".
Note (4): Source detection methods are as follows:
0 = CIAO Wavdetect
1 = PW detect
2 = Both CIAO Wavdetect and PW detect
3 = Enhanced Wavdetect
4 = Visually identified sources
5 = Known sources
Note (5): In Chandra ACIS data analysis the ARF incorporates both the effective
area of the observatory and the fraction of the observation for which
data were actually collected for the source.
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Acknowledgements:
Nicholas J. Wright, n.j.wright(at)keele.ac.uk
(End) Nicholas Wright [Keele, UK], Patricia Vannier [CDS] 07-Nov-2023