J/ApJ/871/103 Catalog of 563 stars in the Galactic Center (Gautam+, 2019)
An adaptive optics survey of stellar variability at the Galactic center.
Gautam A.K., Do T., Ghez A.M., Morris M.R., Martinez G.D., Hosek M.W.,
Lu J.R., Sakai S., Witzel G., Jia S., Becklin E.E., Matthews K.
<Astrophys. J., 871, 103 (2019)>
=2019ApJ...871..103G 2019ApJ...871..103G
ADC_Keywords: Galactic center; Photometry, infrared; Stars, early-type;
Stars, late-type; Magnitudes, absolute; Binaries, eclipsing
Keywords: binaries: eclipsing ; Galaxy: center ; stars: variables: general ;
techniques: photometric
Abstract:
We present an ∼11.5yr adaptive optics (AO) study of stellar
variability and search for eclipsing binaries in the central ∼0.4pc
(∼10") of the Milky Way nuclear star cluster. We measure the
photometry of 563 stars using the Keck II Near Infrared Camera 2
(NIRC2) imager (K'-band, λ0=2.124µm). We achieve a
photometric uncertainty floor of ΔmK'∼0.03 (∼3%), comparable
to the highest precision achieved in other AO studies. Approximately
half of our sample (50%±2%) shows variability: 52%±5% of known
early-type young stars and 43%±4% of known late-type giants are
variable. These variability fractions are higher than those of other
young, massive star populations or late-type giants in globular
clusters, and can be largely explained by two factors. First, our
experiment time baseline is sensitive to long-term intrinsic stellar
variability. Second, the proper motion of stars behind spatial
inhomogeneities in the foreground extinction screen can lead to
variability. We recover the two known Galactic center eclipsing binary
systems: IRS16SW and S4-258(E60). We constrain the Galactic center
eclipsing binary fraction of known early-type stars to be at least
2.4%±1.7%. We find no evidence of an eclipsing binary among the
young S-stars nor among the young stellar disk members. These results
are consistent with the local OB eclipsing binary fraction. We
identify a new periodic variable, S2-36, with a 39.43days period.
Further observations are necessary to determine the nature of this
source.
Description:
We used laser guide star adaptive optics (LGSAO) high-resolution
imaging of the Galactic center obtained at the 10m W. M. Keck II
telescope with the Near Infrared Camera 2 (NIRC2) NIR facility imager
(PI: K. Matthews) through the K' bandpass (λ0=2.124µm,
Δλ=0.351µm).
Observations were centered near the location of SgrA* in the nuclear
star cluster, with a field of view of the NIRC2 images extending about
10"x10" (10"∼0.4pc at SgrA*'s distance of R0∼8kpc) and a plate scale
of 9.952mas/pix or 9.971mas/pix.
Observations used in this work were obtained over 45 nights spanning
2006 May-2017 August. We list details about individual observations in
Table 1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 65 45 Observations used in this work
table12.dat 77 563 Catalog of stars in sample
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See also:
J/ApJ/470/864 : JHKL photometry of the Galactic Center (Blum+, 1996)
J/ApJ/523/248 : Variable stars in the Galactic center (Ott+, 1999)
J/A+A/373/608 : Early-type stars towards Galactic Center. II. (Dufton+,2001)
J/A+A/426/81 : Kinematic analysis of the Minispiral (Paumard+, 2004)
J/A+A/433/117 : L- & M-band imaging of the Galactic Center (Viehmann+, 2005)
J/MNRAS/370/1979 : JHKs photometry T2Cs in globular clusters (Matsunaga+, 2006)
J/ApJ/643/1011 : Early-type stars in the center of the Galaxy (Paumard+,2006)
J/ApJ/659/1241 : Stellar variability in Galactic Center (Rafelski+, 2007)
J/ApJ/697/1741 : Warped disks of YSOs in Galactic center (Bartko+, 2009)
J/ApJ/703/1323 : Spectroscopy of stars in Galaxy's nuclear cluster (Do+ 2009)
J/MNRAS/399/1709 : Near-infrared survey of Miras (Matsunaga+, 2009)
J/ApJ/723/1195 : SAGE AGB candidates (Riebel+, 2010)
J/A+A/511/A18 : NIR observations of stars near SgrA* (Schoedel+, 2010)
J/ApJ/725/331 : Astrometry in the Galactic Center (Yelda+, 2010)
J/A+A/537/A146 : Stellar models (rotation 0.8<M<120, Z=0.014) (Ekstrom+,2012)
J/ApJ/764/154 : Stellar populations in the central 0.5pc. I. (Do+, 2013)
J/ApJ/779/L6 : 3D kinematic obs. of stars in Galactic Centre (Do+, 2013)
J/A+A/562/A125 : OGLE-III SMC tars VI light curves (Kourniotis+, 2014)
J/MNRAS/442/2381 : Variable stars in M4 primary field (Nascimbeni+, 2014)
J/ApJ/783/131 : Kinematic of stars in Galactic center (Yelda+, 2014)
J/AJ/150/132 : JHK photometry of 1203 variables in ONC (Rice+, 2015)
J/ApJ/808/106 : NIR spectroscopic obs. in Galactic Center (Stostad+, 2015)
J/ApJ/830/17 : Galactic Center secondary IR astrometric std (Boehle+, 2016)
J/A+A/585/A141 : Galactic center early-type stars catalog (Grosboel, 2016)
J/A+A/592/A120 : Variable stars in NGC 6715 (Figuera Jaimes+, 2016)
J/A+A/588/A128 : Variable stars in globular clusters (Figuera Jaimes+, 2016)
J/MNRAS/470/3427 : Variable Stars in the Galactic Center (Dong+, 2017)
J/ApJ/854/12 : 16yrs of radial velocity measurements of S0-2 (Chu+, 2018)
J/A+A/609/A26 : Galactic Center old stars distribution (Gallego-Cano+, 2018)
J/A+A/610/A83 : GALACTICNUCLEUS: JHKs imaging survey (Nogueras-Lara+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 yr Obs.Y [2006/2017] UTC year of observation
6- 8 A3 "month" Obs.M UTC month of observation
10-11 I2 "day" Obs.D UTC day of observation
13 A1 --- f_Obs.D [a] Flag on Obs.D (1)
15- 23 F9.3 d MJD [53858/57992] Modified Julian Date of observation
25- 27 I3 --- Frame [9/193] Frame number
29- 32 I4 --- Ndet [652/2514] Number of stars detected
34- 36 I3 --- Ns [361/524] Number of stars in sample
38- 42 F5.3 mag eKMAG [0.15/0.22] Error on absolute K' magnitude (2)
44- 48 F5.3 mag eKmag [0.01/0.08] Error on relative K' magnitude (2)
50- 54 F5.3 mas eAstro [0.29/1.35] Error on astrometric data (2)
56- 60 F5.2 mas FWHM [53.1/88.3] Full Width at Half Maximum (3)
62- 65 F4.2 --- Strehl [0.15/0.43] Strehl ratio (3)
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Note (1): Flag as follows:
a = Denotes consecutive nights of observations that were combined into
single epochs in previous publications from our group for
astrometric study. In this work, we split multiple night combined
epochs into single night epochs for greater time precision.
Note (2): Median astrometric and photometric errors were computed for stars in
our study's sample detected in the corresponding observation.
Absolute photometric zero-point errors were calculated after
conducting initial calibration, using bandpass corrected reference
fluxes for non-variable stars from Blum+, (1996, J/ApJ/470/864) in
our experiment's field of view. Relative photometric errors were
determined after our calibration and local correction method were
applied.
Note (3): The median FWHM and Strehl quantities were calculated for IRS33N
across all frames used to construct the final image for the
corresponding observation.
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Byte-by-byte Description of file: table12.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- ID Star identifier
12- 16 F5.2 mag Kmag [9.9/16] Mean K' band magnitude
18- 24 A7 --- SpType Spectral type; early (85 occurrences) or
late (143 occurrences)
26- 27 I2 --- Night [16/45] Nights detected
29- 34 F6.2 --- chi2 [0.13/515] Reduced χ2 value
36- 38 A3 --- Var? Variable source ? yes (280 occurrences) or
no (283 occurrences)
40 A1 --- VarType Variable type (1)
42- 46 F5.2 arcsec x0 [-5.3/5.6] Position East of Sgr A*
48- 52 F5.2 arcsec y0 [-6.5/4.2] Position North of Sgr A*
54- 61 F8.3 --- Obs.Y [2006/2017] Time (Julian Epoch year)
63- 66 F4.2 --- rms [0.01/1.6] Root mean square (2)
68- 71 F4.2 --- IQR [0.01/3] The interquartile range (3)
73- 77 F5.2 --- 1/eta [0.39/26.58] The inverse von Neumann ratio
(1/η) (4)
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Note (1): Types as follows:
C = variability likely caused by confusion (1 occurrence)
L = variability on timescales ~>1year (42 occurrences)
Variability type is determined for highly variable stars
(χ2red≥10.0) by visual inspection of the star's
light curve and local field of the star in the images.
Note (2): Calculated is that of the observed magnitude differences from
the mean magnitude.
Note (3): The difference between the median of the half brightest and
half dimmest observations.
Note (4): The ratio of mean square of differences in successive
observations to the variance of all observations.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 06-Apr-2020