J/ApJS/214/10 Optical counterparts of Chandra GBS sources (Britt+, 2014)
Variability of optical counterparts in the Chandra Galactic Bulge Survey.
Britt C.T., Hynes R.I., Johnson C.B., Baldwin A., Jonker P.G., Nelemans G.,
Torres M.A.P., Maccarone T., Steeghs D., Greiss S., Heinke C., Bassa C.G.,
Collazzi A., Villar A., Gabb M., Gossen L.
<Astrophys. J. Suppl. Ser., 214, 10 (2014)>
=2014ApJS..214...10B 2014ApJS..214...10B
ADC_Keywords: Photometry, RI ; Stars, variable ; X-ray sources ; Surveys
Keywords: accretion, accretion disks; Galaxy: bulge; stars: black holes;
stars: dwarf novae; stars: flare; stars: neutron;
stars: variables: general; surveys; X-rays: binaries
Abstract:
We present optical light curves of variable stars consistent with the
positions of X-ray sources identified with the Chandra X-ray
Observatory for the Chandra Galactic Bulge Survey (GBS). Using data
from the Mosaic-II instrument on the Blanco 4m Telescope at CTIO, we
gathered time-resolved photometric data on timescales from ∼2hr to
8 days over the 3/4 of the X-ray survey containing sources from the
initial GBS catalog. Among the light curve morphologies we identify
are flickering in interacting binaries, eclipsing sources, dwarf nova
outbursts, ellipsoidal variations, long period variables, spotted
stars, and flare stars. Eighty-seven percent of X-ray sources have at
least one potential optical counterpart. Twenty-seven percent of these
candidate counterparts are detectably variable; a much greater
fraction than expected for randomly selected field stars, which
suggests that most of these variables are real counterparts. We
discuss individual sources of interest, provide variability
information on candidate counterparts, and discuss the characteristics
of the variable population.
Description:
We acquired eight nights of photometry, from 2010 July 8-15, with the
Blanco 4.0m telescope at the Cerro Tololo Inter-American Observatory
(CTIO). Using the Mosaic-II instrument, we observed the 9deg2 area
containing the X-ray sources identified by the first Galactic Bulge
Survey (GBS) X-ray observations (Jonker et al. 2011, Cat. J/ApJS/194/18;
superseded by 2014, Cat. J/ApJS/210/18).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 89 167 Each Galactic Bulge Survey (GBS) source with a
likely variable optical counterpart
table3.dat 31 4400 Lightcurves of variable optical counterparts
to GBS sources
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
II/316 : UKIDSS-DR6 Galactic Plane Survey (Lucas+ 2012)
J/ApJS/210/18 : X-ray survey of the Galactic Bulge (CXOGBS) (Jonker+, 2014)
J/ApJ/761/162 : Tycho-2 stars in Galactic Bulge Survey (Hynes+, 2012)
J/AcA/62/133 : Optical counterparts of X-ray sources in OGLE (Udalski+, 2012)
J/AcA/61/285 : VI light curves of Galactic Bulge Cepheids (Soszynski+, 2011)
J/AcA/61/1 : VI light curves of Galactic Bulge RR Lyrae (Soszynski+, 2011)
J/ApJS/194/18 : The Galactic Bulge Survey: X-ray observations (Jonker+, 2011)
J/ApJ/721/1663 : NIR matches of X-ray sources in Gal. Center (DeWitt+, 2010)
J/ApJ/703/30 : NIR counterparts to Chandra X-ray sources. (Mauerhan+, 2009)
J/ApJ/700/1702 : ChaMPlane deep galactic bulge survey. I. (van den Berg+, 2009)
J/MNRAS/351/31 : XMM-Newton Galactic Plane Survey (XGPS) (Hands+, 2004)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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2- 5 I4 --- [JBN2011] [2/1232] Chandra Catalog identifier (1)
7- 15 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000)
17- 25 F9.5 deg DEdeg Declination in decimal degrees (J2000)
27- 31 F5.2 mag r'mag [15.5/23.5] The r' band magnitude
33- 37 F5.3 mag e_r'mag [0.001/0.3] Average relative photometric
error in r'mag
39- 43 F5.3 mag RMS RMS variation of lightcurve
45- 49 F5.3 arcsec Sep [0.03/6.5] Distance to star from X-ray position
51- 56 F6.3 arcsec CR95 [0.3/13] 95% confidence radius of X-ray position
58- 59 I2 --- Num [7/70] Number of observations in lightcurve
61- 64 F4.1 [-] logx/o [-1.8/2] log of X-ray to optical fluxes
without correcting for extinction
66- 69 F4.2 mag E(B-V) [1/4.3] The (B-V) color excess (2)
71- 74 F4.1 [-] logxoc [-5.4/0.3] Corrected X-ray to optical flux (3)
76- 80 F5.2 --- HR [-1.2/1] X-ray hardness ratio (4)
82- 89 E8.3 --- FAP False Alarm Probability (5)
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Note (1): Designation as given by Jonker et al. 2011 (J/ApJS/194/18).
Objects 884 and 1004 are not included in table 3 as they were
reclassified as non-variables because they failed to meet the
definition laid out in the paper.
Note (2): For the line of sight at Bulge distance using the reddening maps
from Gonzalez et al. (2012A&A...543A..13G 2012A&A...543A..13G).
Note (3): After correcting for reddening, assuming Bulge distance.
Note (4): As calculated in Jonker et al. (2011, Cat. J/ApJS/194/18), only
presented for sources with >20 photons.
Note (5): For a variable star at the given distance from the X-ray position,
as calculated in Section 3.
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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- 4 I4 --- [JBN2011] [2/1232] Chandra Catalog identifier
6- 18 F13.5 d HJD Heliocentric Julian Date
20- 25 F6.3 mag r'mag [15.3/26.2] The r' band magnitude
27- 31 F5.3 mag e_r'mag [0/2.5] Average relative photometric error
in r'mag
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History:
From electronic version of the journal
22-Oct-2014: Insert into VizieR
24-Oct-2014: Note (1) added in table 2 for CX884 and CX1004
thanks to Chris Britt.
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 08-Oct-2014