J/MNRAS/470/3427 Variable Stars in the Galactic Center (Dong+, 2017)
Near-infrared variability study of the central 2.3 arcmin x 2.3 arcmin of the
Galactic Centre.
I. Catalog of variable sources.
Dong H., Schodel R., William B.F., Nogueras-Lara F., Gallego-Cano E.,
Gallego-Calvente T., Wang Q.D., Morris R.M., Do T., Ghez A.
<Mon. Not. R. Astron. Soc. 470, 3427 (2017)>
=2017MNRAS.470.3427D 2017MNRAS.470.3427D (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, variable ; Photometry, infrared
Keywords: stars: variables: general - Galaxy: centre - infrared: stars
Abstract:
We used four-year baseline HST/WFC3 IR observations of the Galactic
Centre in the F153M band (1.53 micron) to identify variable stars in
the central ∼2.3'x2.3' field. We classified 3845 long-term (periods
from months to years) and 76 short-term (periods of a few days or
less) variables among a total sample of 33070 stars. For 36 of the
latter ones, we also derived their periods (<3 days). Our catalog not
only confirms bright long period variables and massive eclipsing
binaries identified in previous works, but also contains many newly
recognized dim variable stars. For example, we found delta Scuti and
RR Lyrae stars towards the Galactic Centre for the first time, as well
as one BL Her star (period < 1.3d). We cross-correlated our catalog
with previous spectroscopic studies and found that 319 variables have
well-defined stellar types, such as Wolf-Rayet, OB main sequence,
supergiants and asymptotic giant branch stars. We used colours and
magnitudes to infer the probable variable types for those stars
without accurately measured periods or spectroscopic information. We
conclude that the majority of unclassified variables could potentially
be eclipsing/ellipsoidal binaries and Type II Cepheids. Our source
catalog will be valuable for future studies aimed at constraining the
distance, star formation history and massive binary fraction of the
Milky Way nuclear star cluster.
Description:
We use the 'DOLPHOT' to detect sources and extract photometry from the
HST WFC3/IR observations at the F127M and F135M bands of the Galactic
Centre from 2010 to 2014. The F153M observations, which are used to
identify variable stars, include 290 dithered exposures from six HST
programs.
The detailed description of the HST dataset are given in Table 1 of
the paper.
We identified 33070 sources. Their F127M and F153M magnitudes, as well
as their uncertainties, are given in Table 3. For each star, we used
the least chi square method to identify whether it is variable or not.
The output from the least chi square method are chi^2_y and chi^2_d,
which are calculated from all the 290 dithered exposures and the
exposures in March and April, 2014, respectively, to examine whether
the star varies among years and/or days. In order to reduce the
potential variation among dithered exposures, which could be
potentially introduced by instrument effects, we also bin the dithered
exposures and use the least chi square method to calculate chi^2_{y,b}
and chi^2_{d,b}. We classify stars with chi^2_y>3 and chi^2_{y,b}>2 are
variables among years and stars with chi^2_d>3 and chi^2_{d,b}>2 are
variables among days. The detailed description about the data analysis
is given in the paper.
In Table 4, we gives the magnitudes of sources in individual dithered
exposures, as well as the photometric uncertainties and the quality
control parameters provided by 'DOLPHOT', such as signal-to-noise
ratio, sharpness^2, crowd and flag.
We also cross-correlated our variables with previous variable studies
taken by ground-based telescopes in Table 8 and spectroscopic
observations in Table 9.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 87 33070 List of detected stars
table4.dat 52 9590300 The magnitudes in individual dithered exposures
table8.dat 95 302 The counterparts of our variables stars in
previous variability studies
table9.dat 141 319 The counterparts of our variables stars in
previous spectroscopy studies
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 5 I05 --- ID Source ID
7- 15 F9.5 deg RAdeg Right ascension (J2000)
17- 25 F9.5 deg DEdeg Declination (J2000)
27- 31 F5.2 mag F153M ?=99.9 Magnitude at the F153M band (1)
32 A1 --- n_F153M [s] s for saturated
33- 37 F5.3 mag s_F153M ?=9.9 Systematic error at the F153M band (2)
39- 43 F5.3 mag e_F153M ?=9.9 Statistic error at the F153M band
45- 49 F5.2 mag F127M ?=99.9 Magnitude at the F127M band (1)
50 A1 --- n_F127M [s] s for saturated
51- 55 F5.3 mag s_F127M ?=9.9 Systematic error at the F127M band (2)
57- 61 F5.3 mag e_F127M ?=9.9 Statistic error at the F127M band
63- 67 F5.1 --- chi2y chi2y value
69- 73 F5.1 --- chi2yb chi2{y,b} value
75- 79 F5.1 --- chi2d chi2d value
81- 85 F5.1 --- chi2db chi2{d,b} value
87 I1 --- Vindex [0/3] Variable index (3)
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Note (1): If the source is saturated, its magnitude is 99.90 and flag is s.
If the source is undetected, its magnitude is 99.90.
Note (2): The systematic error is introduced by the crowding and should always
be positive
Note (3): Variable index shows whether the source is variable or not as follows:
0 = non-variable
1 = stars varying on yearly time scales
2 = stars with intraday variability
3 = stars varying on both yearly and daily time scales
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I05 --- ID Source IDs
7- 15 F9.3 d JD Julian day of the dithered exposures
(JD-2400000)
17- 21 F5.2 mag F153M ?=99.9 Magnitude at the F153M band at
individual dithered exposures (1)
22 A1 --- n_F153M [s] s for saturated
23- 27 F5.3 mag e_F153M ?=9.9 Error at the F153M band used in the
least chi square method to determine the
variability
29- 34 F6.1 --- S/N ?=0 Signal-to-noise ratio
36- 43 F8.4 --- Sharp2 ?=0 Square of DOLPHOT/ACS sharpness parameter
45- 49 F5.3 --- Crowd ?=0 DOLPHOT/ACS crowding parameter
51- 52 I2 --- FLAG ?=0 Flag defined in 'DOLPHOT' manual
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Note (1): If the magnitude is >90, the source is saturated (flag =s ) or
undetected.
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I05 --- ID Source IDs
7- 13 A7 --- GCIRS Name of counterparts in
Tamura et al. 1996ApJ...467..645T 1996ApJ...467..645T
15- 20 A6 --- Blum Name of counterparts in
Blum et al. 1996, Cat. J/ApJ/470/864
27- 29 I3 --- [OEG99] ?=- Name of counterparts in
Ott et al. 1999, Cat. J/ApJ/523/248
31- 37 A7 --- [GMC2001] Name of counterparts in
Glass et al. 2001, Cat. J/MNRAS/321/77
N-NNN, [GMC2001] N-NNN in Simbad
39- 60 A22 --- Peeples Name of counterparts in
Peeples et al. 2007AcA....57..173P 2007AcA....57..173P
(PSDJHHMMSS.ss+DDMMSS.s), not in Simbad
62- 68 A7 --- Reid Name of counterparts in
Reid et al. 2007ApJ...659..378R 2007ApJ...659..378R
SiONN, IRSNN, not in Simbad
70- 78 A9 --- Rafelski Name of counterparts in
Rafelski et al. 2007, Cat. J/ApJ/659/1241
IRSNNAA, SN-NN,
GCIRS NNAA, [GKM98] SN-NN in Simbad
85- 87 I3 --- [MKN2009] ?=- Name of counterparts in
Matsunaga et al. 2009, Cat. J/MNRAS/399/1709
NNN, [MKN2009] NNNN in Simbad
89- 95 A7 --- Pfuhl Name of counterparts in
Pfuhl et al. 2011ApJ...741..108P 2011ApJ...741..108P
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Byte-by-byte Description of file: table9.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I05 --- ID Source ID
7- 18 A12 --- Name Widely used name
20- 24 A5 --- n_Name Note on Name
30- 32 I3 --- [BSD96] ?=- Name of counterparts in
Blum et al. 2003, Cat. J/ApJ/597/323
[BSD96] NNN in Simbad
34- 46 A13 --- n_[BSD96] Note on [BSD96]
48- 50 I3 --- Maness ?=- Name of counterparts in
Maness et al. 2007ApJ...669.1024M 2007ApJ...669.1024M,
not in Simbad
51- 56 A6 --- n_Maness Note on Maness
58- 60 A3 --- [PGM2006] Name of counterparts in
Paumard et al. 2006, Cat. J/ApJ/643/1011
[PGM2006] ENN in Simbad
61- 73 A13 --- n_[PGM2006] Note on [PGM2006]
75- 76 I2 --- [BMF2009] ? Name of counterparts in
Bartko et al. 2009, Cat. J/ApJ/697/1741
[BMF2009] NN in Simbad
77- 83 A7 --- n_[BMF2009] Note on [BMF2009]
85- 90 A6 --- [GKM98] Name of counterparts in
Do et al. 2013, Cat. J/ApJ/764/154
GCIRS NNAA, [GKM98] SN-NN in Simbad
91- 93 A3 --- n_[GKM98] Note on [GKM98]
95-103 A9 --- Stostad Name of counterparts in
Stostad et al. 2015, Cat. J/ApJ/808/106
not in Simbad
104-106 A3 --- n_Stostad Note on Stostad
108-112 I5 --- [FNS2015] ?=- Name of counterparts in
Feldmeier-Krause et al. 2015, Cat.
J/A+A/584/A2, [FNS2015] NNNNN in Simbad
113-123 A11 --- n_[FNS2015] Note on [FNS2015]
125-126 I2 --- [NS2013] ?=- Name of counterparts in
Nishiyama et al. 2016A&A...588A..49N 2016A&A...588A..49N,
[NS2013] NN in Simbad
127-129 A3 --- n_[NS2013] Note on [NS2013]
131-135 I5 --- [FKN2017] ? the name of counterparts in
Feldmeier-Krause et al. 2017,
Cat. J/MNRAS/464/194, not yet in Simbad
136-141 A6 --- n_[FKN2017] Note on [FKN2017]
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Acknowledgements:
Hui Dong, hdong(at)iaa.es
(End) Hui Dong [IAA-CSIC, Spain], Patricia Vannier [CDS] 15-Jun-2017