J/AJ/160/115 JHK observation of 75 OB stars in Cyg OB2 (Caballero-Nieves+, 2020)
A high angular resolution survey of massive stars in Cygnus OB2: JHK adaptive
optics results from the Gemini Near-Infrared Imager.
Caballero-Nieves S.M., Gies D.R., Baines E.K., Bouchez A.H., Dekany R.G.,
Goodwin S.P., Rickman E.L., Roberts L.C., Taggart K., ten Brummelaar T.A.,
Turner N.H.
<Astron. J., 160, 115 (2020)>
=2020AJ....160..115C 2020AJ....160..115C
ADC_Keywords: Surveys; Stars, OB; Stars, double and multiple;
Photometry, infrared; Spectral types
Keywords: Massive stars ; Early-type stars ; Wide binary stars ;
OB associations ; OB stars
Abstract:
We present results of a high angular resolution survey of massive OB
stars in the Cygnus OB2 association that we conducted with the
Near-Infrared Imager camera and ALTAIR adaptive optics system of the
Gemini North telescope. We observed 74 O- and early-B-type stars in
Cyg OB2 in the JHK infrared bands in order to detect binary and
multiple companions. The observations are sensitive to
equal-brightness pairs at separations as small as 0.08", and
progressively fainter companions are detectable out to ΔK=9mag
at a separation of 2". This faint contrast limit due to read noise
continues out to 10" near the edge of the detector. We assigned a
simple probability of chance alignment to each companion based upon
its separation and magnitude difference from the central target star
and upon areal star counts for the general star field of Cyg OB2.
Companion stars with a field membership probability of less than 1%
are assumed to be physical companions. This assessment indicates that
47% of the targets have at least one resolved companion that is
probably gravitationally bound. Including known spectroscopic
binaries, our sample includes 27 binary, 12 triple, and 9 systems with
4 or more components. These results confirm studies of high-mass stars
in other environments that find that massive stars are born with a
high-multiplicity fraction. The results are important for the
placement of the stars in the Hertzsprung-Russell diagram, the
interpretation of their spectroscopic analyses, and for future mass
determinations through measurement of orbital motion.
Description:
We were able to observe 74 of the brightest O- and B-type stars in Cyg
OB2 and one misidentified nonmember using the infrared ALTtitude
conjugate Adaptive optics for the InfraRed (ALTAIR) Adaptative Optic
(AO) system at the Gemini North Observatory.
Our observations were made in three queue observing programs at the
8.1m Gemini North Observatory during the 2005B, 2008A, and 2008B
observing semesters. Using the Near-Infrared Imager (NIRI) with the
ALTAIR AO system, we collected high-resolution images.
For these observations, NIRI was held fixed and the exposure times for
each frame ranged between 0.02s and 800s in K and between 0.1s and
1869s in J, depending of the brightness of the target star in each
band in order to reach about half of the full well depth of the
detector and achieve uniform signal-to-noise ratio (S/N) measurements
of the target stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 107 75 Sample of stars in Cygnus OB2
table3.dat 44 135 Observations of stars in Cyg OB2
table4.dat 142 621 Stars detected in the sample
table5.dat 29 75 Multiplicity properties
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See also:
B/wds : The Washington Visual Double Star Catalog (Mason+, 2001-2020)
III/215 : 7th Catalog of Galactic Wolf-Rayet stars (van der Hucht, 2001)
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/314 : UKIDSS-DR8 LAS, GCS and DXS Surveys (Lawrence+ 2012)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/AJ/101/1408 : Massive stars in Cyg OB2. (Massey+ 1991)
J/A+A/474/495 : X-ray flares Cygnus OB2 young stars (Albacete-Colombo+, 2007)
J/ApJ/664/1102 : Radial velocity survey of Cyg OB2 association (Kiminki+,2007)
J/MNRAS/374/372 : ZYJHK photometry in Upper Sco (Lodieu+, 2007)
J/A+A/486/453 : NIR photometry of early-type stars in Cyg OB2 (Comeron+,2008)
J/AJ/137/3358 : Speckle interferometry of massive stars (Mason+, 2009)
J/ApJS/184/84 : X-ray sources in Cyg OB2 region (Wright+, 2009)
J/A+A/518/A1 : Galactic massive stars with AstraLux (Maiz Apellaniz, 2010)
J/ApJS/190/1 : A survey of stellar families (Raghavan+, 2010)
J/A+A/538/A74 : Massive binaries in Cepheus OB2/3 region (Peter+, 2012)
J/other/Sci/337.444 : RV curves of Galactic massive O stars (Sana+, 2012)
J/A+A/550/A107 : RV catalogue of O stars in 30 Doradus (Sana+, 2013)
J/ApJS/213/34 : Velocities of Cygnus OB2 massive binaries (Kobulnicky+, 2014)
J/ApJ/785/47 : Sources around stars in Upper Scorpius (Lafreniere+, 2014)
J/ApJS/215/15 : SMaSH+: observations and companion detection (Sana+, 2014)
J/AJ/149/26 : Massive binary stars from an HST/FGS survey (Aldoretta+,2015)
J/ApJ/811/85 : RVs & V-band LCs of probable mem. of Cyg OB2 (Kiminki+, 2015)
J/MNRAS/449/741 : The massive star population of Cygnus OB2 (Wright+, 2015)
J/ApJS/224/4 : GOSSS III. 142 addit. O-type systems (Maiz-Apellaniz+, 2016)
J/A+A/601/A34 : Resolved astrometry of ten O-type binaries (Le Bouquin+,2017)
J/A+A/626/A20 : MONOS. I. Spectral classifications (Maiz Apellaniz+, 2019)
J/A+A/627/A2 : New V-band photometry of Cyg OB2 5 (V729 Cyg) (Rauw+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Stars designation
12- 12 A1 --- f_Name Flag on Name (1)
14- 22 A9 --- OName Schulte or other designation
24- 25 I2 h RAh [20/20] Hour of Right Ascension (J2000)
27- 28 I2 min RAm [30/36] Minute of Right Ascension (J2000)
30- 35 F6.3 s RAs Second of Right Ascension (J2000)
37 A1 --- DE- [+] Sign of the Declination (J2000)
38- 39 I2 deg DEd [40/42] Degree of Declination (J2000)
41- 42 I2 arcmin DEm Arcminute of Declination (J2000)
44- 48 F5.2 arcsec DEs Arcsecond of Declination (J2000)
50- 62 A13 --- SpType Spectral Classification
64 I1 --- r_SpType [1/6] Reference code for SpType (2)
66- 70 F5.2 mag Vmag [8.99/13.61]? Apparent V magnitude
73- 78 F6.3 mag Jmag [4.667/10.427] Apparent J magnitude
81- 86 F6.3 mag Hmag [3.512/10.15] Apparent H magnitude
88- 92 F5.3 mag Kmag [2.704/9.993] Apparent Ks magnitude
94- 97 F4.2 mag EJKmag [0.57/1.4]? Color excess in J-K
99-102 F4.2 mag EBVmag [1.28/3.44]? Color excess in B-V
104-107 F4.2 mag Ebymag [0.9/1.75]? Color excess in b-y
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Note (1): MT 140 appears to be an erroneous F-type star
(Maiz Apellaniz+, 2016, J/ApJS/224/4). We include the observations in
the tables but this object is not included in the final analysis of MF
and CF.
Note (2): References as follows:
1 = Kobulnicky+, 2012ApJ...756...50K 2012ApJ...756...50K
2 = Kiminki+, 2007, J/ApJ/664/1102
3 = Negueruela+, 2008A&A...487..575N 2008A&A...487..575N
4 = Muntean+, 2009MNRAS.399.1977M 2009MNRAS.399.1977M
5 = SIMBAD database, http://simbad.u-strasbg.fr/simbad/
6 = Mason+, 2001, B/wds
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Star designation
12- 19 F8.3 d Date [3613/5019] Julian Date; JD-2450000
21 A1 --- f_Name Notes on how the data was analyzed (1)
23- 31 A9 --- Filt Filter used
33- 36 F4.2 --- Strehl [0.01/0.43] Strehl ratio
38- 40 I3 mas FWHM [74/159] Full Width at Half Maximum
42- 44 I3 --- Number [17/130] Number of images combined for the analysis
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Note (1): For stars whose observations span multiple nights, the final data
for analysis were handled differently. C denotes that the combined
image from both nights was used for analysis. * denotes which
individual night was used for analysis.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Field Name
12- 16 F5.2 arcsec Sep [0.08/16.71]? Separation
18- 22 F5.1 deg PA [0.1/360]? Position Angle
24- 25 I2 h RAh [20] Hour of Right Ascension (J2000)
27- 28 I2 min RAm [30/36] Minute of Right Ascension (J2000)
30- 35 F6.3 s RAs Second of Right Ascension (J2000)
37 A1 --- DE- [+] Sign of the of Declination (J2000)
38- 39 I2 deg DEd [40/42] Degree of Declination (J2000)
41- 42 I2 arcmin DEm Arcminute of Declination (J2000)
44- 48 F5.2 arcsec DEs Arcsecond of Declination (J2000)
50- 54 F5.2 mag Jmag [-1.94/9.17]? Differential J magnitude (1)
56- 59 F4.2 mag e_Jmag [0.01/1.82]? Error in J magnitude
61- 64 F4.2 mag Hmag [0.04/9.17]? Differential H magnitude (1)
66- 69 F4.2 mag e_Hmag [0.01/0.31]? Error in H magnitude
71- 75 F5.2 mag Kmag [-1.07/9.37]? Differential K magnitude (1)
77- 80 F4.2 mag e_Kmag [0.01/2.73]? Error in K magnitude
82- 86 F5.3 --- Prob [0/0.832]? Probability of chance alignment
with background field star
88- 99 A12 --- UKIDSS UKIRT IR Deep Sky Survey identification number
101-118 A18 --- OName Other Name (2)
120-142 A23 --- Notes Additional notes
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Note (1): The 2MASS magnitude given for the target stars, all others are
relative magnitudes measured with respect to the target stars.
Note (2): For other names, correspondence in another field,
FITSTARS (FS) measurement.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Star designation
12- 13 I2 --- Niri [2/47] Total number of stars found in target field
15 I1 --- Cand [0/4] Number of high probability companion stars
from NIRI
17 I1 --- FGS [0/2]? Number of companions detected with FGS
19 I1 --- SB [0/2]? Spectroscopic binaries (3)
21 I1 --- Total [0/5]? Total number of unique companions from
columns 3-5
23 I1 --- New [0/3]? New companions detected during this work
25- 29 A5 --- Mass Mass of target star (4)
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Note (3): Companions found through radial velocity measurements taken from
Kobulnicky+, 2014, 2014ApJS..213...34K 2014ApJS..213...34K and references therein,
or Muntean+, 2009MNRAS.399.1977M 2009MNRAS.399.1977M for WR 145.
Note (4): From Wright+, 2015, J/MNRAS/449/741
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 23-Oct-2020