J/ApJ/659/1241 Stellar variability in Galactic Center (Rafelski+, 2007)
Photometric stellar variability in the Galactic Center.
Rafelski M., Ghez A.M., Hornstein S.D., Lu J.R., Morris M.
<Astrophys. J., 659, 1241-1256 (2007)>
=2007ApJ...659.1241R 2007ApJ...659.1241R
ADC_Keywords: Stars, variable ; Photometry, infrared
Keywords: Galaxy: center - infrared: stars - stars: variables: other
Abstract:
We report the results of a diffraction-limited, photometric
variability study of the central 5"x5" of the Galaxy conducted over
the past 10-years using speckle imaging techniques on the W.M. Keck I
10 m telescope. Within our limiting magnitude of mK<16mag for images
made from a single night of data, we find a minimum of 15K[2.2um]-band
variable stars out of 131 monitored stars. The only periodic source in
our sample is the previously identified variable IRS 16SW, for which
we measure an orbital period of 19.448±0.002-days.
Description:
K-band (λ0=2.2um, {DELTA}λ=0.4um) speckle imaging
observations of the Galaxy's central stellar cluster were obtained
with the W.M. Keck I 10m telescope using the facility near-infrared
camera (NIRC). Observations taken from 1995 to 2004 have been
described in detail elsewhere (Ghez et al., 1998ApJ...509..678G 1998ApJ...509..678G,
2000Natur.407..349G 2000Natur.407..349G, 2005ApJ...620..744G 2005ApJ...620..744G; Lu et al.,
2005ApJ...625L..51L 2005ApJ...625L..51L), and new observations on 2005 April 24-25 were
conducted in a similar manner, resulting in diffraction-limited
images.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 90 16 List of variable stars
table3.dat 92 115 List of nonvariable stars
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See also:
J/ApJ/523/248 : Variable stars in the Galactic center (Ott+, 1999)
J/ApJ/643/1011 : Early-type stars in the center of the Galaxy (Paumard+, 2006)
Byte-by-byte Description of file: table[23].dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Star name (SN-NN = [GKM98] SN-NN in Simbad)
11 A1 --- n_Name [h] least variable (1)
13- 29 A17 --- OName ?=--- Other name (2)
31- 35 F5.2 mag Kmag K magnitude (3)
37- 40 F4.2 mag e_Kmag rms uncertainty on Kmag
42- 45 F4.2 mag var ? Internal variation (table2 only)
47- 50 F4.2 arcsec p Projected distance from Sgr A* (4)
52- 56 F5.2 arcsec DRA Offet in right ascension from Sgr A* (4)
58- 62 F5.2 arcsec DDE Offset in declination from Sgr A* (4)
64- 70 E7.2 --- Prob ? K-S non-variable probability (table2 only) (5)
72- 73 I2 d N Number of nights
75- 86 A12 --- Type ?=--- Stellar spectral type
88- 92 A5 --- Notes Notes (6)
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Note (1): h indicates the seven least variable bright stars detected in
all images used for scaling of the photometry in order to reduce the
fluctuations induced by measurement errors on IRS 16C (see Sect. 3.1).
Note (2): Other IDs are from Paumard et al. (2006, Cat. J/ApJ/643/1011,
[PGM2006] +x.xx+y.yy, [PGM2006] ENN) and Genzel et al.
(2000MNRAS.317..348G 2000MNRAS.317..348G, [GEO97] WNN), respectively.
Note (3): The magnitudes are Qj corrected using seven bright nonvariable
stars, and the uncertainties do not include the 5% absolute
calibration uncertainties. Comparison to other sources requires adding
them in quadrature. Uncertainties are calculated as the standard
deviation of the mean.
Note (4): Positions are in arcseconds offset from Sgr A* in 1999.56
Note (5): The K-S probability is equal to 1 for an ideal nonvariable
source, and approaches zero for a very variable source
Note (6): Notes as follows:
a = Identified as nonvariable by Ott et al. (1999, Cat. J/ApJ/523/248).
b = Spectroscopic identification by Paumard et al. 2006 (J/ApJ/643/1011).
c = Identified as possibly variable by Ott et al. 1999 (J/ApJ/523/248).
f = Spectroscopic identification by Ott (2003, Ph.D. thesis,
Max-Planck-Institut fur extraterrestrische Physik).
We denote sources with clear CO or He lines as early and late,
respectively.
g = Identification based on the interpretation by Genzel et al.
(2003ApJ...594..812G 2003ApJ...594..812G) of m(CO) index of Ott (2003, Ph.D. thesis,
Max-Planck-Institut fur extraterrestrische Physik), where Genzel
et al. (2003ApJ...594..812G 2003ApJ...594..812G) identify stars with m(CO)≥0.04 as
late-type stars and stars with m(CO)0.04 as early-type stars.
d = This is our main calibration star and is included in this table
only for completeness.
e = Spectroscopic identification by Figer et al. (2003ApJ...599.1139F 2003ApJ...599.1139F).
i = Identified as possibly variable by Ott et al. 1999 (J/ApJ/523/248).
j = Spectroscopic identification by Eisenhauer et al.i
(2005ApJ...628..246E 2005ApJ...628..246E).
k = IRS 16CC appears to be variable in the L band, as discussed in
Sect. 3.1.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 05-Jun-2010