J/ApJS/194/27 Variable stars in Cygnus OB2 (Henderson+, 2011)
An R- and I-band photometric variability survey of the Cygnus OB2 association.
Henderson C.B., Stanek K.Z., Pejcha O., Prieto J.L.
<Astrophys. J. Suppl. Ser., 194, 27 (2011)>
=2011ApJS..194...27H 2011ApJS..194...27H
ADC_Keywords: Stars, variable ; Photometry, RI ; Photometry, infrared ;
Associations, stellar ; Surveys
Keywords: binaries: eclipsing - binaries: general - open clusters and
associations: individual (Cygnus OB2) - stars: massive -
stars: variables: T Tauri, Herbig Ae/Be
Abstract:
We present a catalog of photometrically variable stars discovered
within two 21.3'x21.3' fields centered on the Cygnus OB2 association
(Cyg OB2). There have hitherto been no deep optical variability
studies of Cyg OB2, despite it being replete with early-type massive
stars, likely due to the high and variable extinction (up to AV∼20)
that permeates much of the region. Here, we provide results of the
first variability study with this combination of spatial coverage
(∼0.5deg) and photometric depth (R∼21mag). We find 121 stars to be
variable in both R and I bands, 115 of them newly discovered. Of the
121 variables, we identify 27 eclipsing binaries and eclipsing-binary
candidates, 52 pulsating variables, and 20 potential Herbig Ae/Be
stars. Confirming both the status and the cluster membership of the
Herbig Ae/Be stars would address the uncertainty regarding the age and
star formation history of Cyg OB2. We match our catalog to known
variables and binaries in the region, Two Micron All Sky Survey
near-IR data, and Chandra X-ray observations to find counterparts to
new variables in other wavelengths.
Description:
The data were obtained on the MDM 1.3m McGraw-Hill telescope using
the 4K imager. The observations consist of 60s exposures taken through
the Cousins R filter and 10s exposures taken through the Cousins I
filter. The data were collected over 19 nights during the fall of
2007, spanning September 12-October 24, and 18 nights during the
summer of 2009, spanning May 30-June 25.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 103 121 Parameters of the 121 variable stars identified
in this study
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/ApJS/184/84 : X-ray sources in Cyg OB2 region (Wright+, 2009)
J/A+A/486/453 : NIR photometry of early-type stars in Cyg OB2 (Comeron+,
2008)
J/A+A/464/211 : Chandra and near-IR obs. of Cyg OB2 (Albacete Colombo+, 2007)
J/A+A/472/557 : Cygnus OB2 region 610MHz sources (Marti+, 2007)
J/ApJ/643/238 : Chandra/2MASS sources in Cygnus OB2 (Butt+, 2006)
J/ApJS/149/123 : WSRT survey of Cygnus OB2 (Setia Gunawan+, 2003)
J/MNRAS/298/753 : Variables in Cygnus OB2 (Pigulski+ 1998)
J/AJ/107/1433 : Cygnus OB2 polarimetry (Kobulnicky+, 1994)
http://www.astronomy.ohio-state.edu/~henderson/cygnusvariability/ : light
curves data access
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID Variable identification
(<[HSP2011] NNN> in Simbad)
5- 6 I2 h RAh Hour of right ascension (J2000)
8- 9 I2 min RAm Minute of right ascension (J2000)
11- 15 F5.2 s RAs Second of right ascension (J2000)
17 A1 --- DE- Sign of declination (J2000)
18- 19 I2 deg DEd Degree of declination (J2000)
21- 22 I2 arcmin DEm Arcminute of declination (J2000)
24- 28 F5.2 arcsec DEs Arcsecond of declination (J2000)
30- 33 A4 --- Type Variable type (3)
35 A1 --- u_Per [~] Uncertainty flag on Per
36- 44 F9.6 d Per ? Period
45 A1 --- f_Per [i] i: Irregular period
47- 49 F3.1 mag Ramp R-band peak-to-peak amplitude
51- 66 A16 --- 2MASS 2MASS identification (HHMMSSss+DDMMSSs)
68- 72 F5.2 mag Rcmag Mean Cousins R-band magnitude
74- 78 F5.2 mag Icmag Mean Cousins I-band magnitude
80- 85 F6.3 mag Jmag ? 2MASS J-band magnitude
87- 92 F6.3 mag Hmag ? 2MASS H-band magnitude
94- 99 F6.3 mag Ksmag ? 2MASS Ks-band magnitude
101 A1 --- X [YNO] Chandra X-ray match (1)
103 A1 --- Xv [CVP] X-ray variability (2)
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Note (1): Chandra X-ray match flag as follows:
O = outside our FOV;
N = within our FOV and unsaturated but unmatched;
Y = matched
Note (2): X-ray variability code as follows:
V = variable in X-rays;
P = possibly variable;
C = constant
Note (3): variability types are:
CV? = possible cataclysmic variable
EB = eclipsing binary
Her? = possible Herbig-Haro Ae/Be stars
Irr = Irregular variable
LPV = Long-Period Variable
Per? = possible periodic variables
Pul = Pulsating variable
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 19-Sep-2011