J/ApJS/194/18 The Galactic Bulge Survey: X-ray observations (Jonker+, 2011)
The Galactic Bulge Survey: outline and X-ray observations.
Jonker P.G., Bassa C.G., Nelemans G., Steeghs D., Torres M.A.P.,
Maccarone T.J., Hynes R.I., Greiss S., Clem J., Dieball A., Mikles V.J.,
Britt C.T., Gossen L., Collazzi A.C., Wijnands R., In't Zand J.J.M.,
Mendez M., Rea N., Kuulkers E., Ratti E.M., van Haaften L.M., Heinke C.,
Ozel F., Groot P.J., Verbunt F.
<Astrophys. J. Suppl. Ser., 194, 18 (2011)>
=2011ApJS..194...18J 2011ApJS..194...18J
ADC_Keywords: Binaries, X-ray ; Surveys
Keywords: accretion, accretion disks - binaries: close - X-rays: binaries
Abstract:
We introduce the Galactic Bulge Survey (GBS) and we provide the
Chandra source list for the region that has been observed to date.
Among the goals of the GBS are constraining the neutron star (NS)
equation of state and the black hole (BH) mass distribution via the
identification of eclipsing NS and BH low-mass X-ray binaries (LMXBs).
The GBS targets two strips of 6°x1° (12deg2 in total), one
above (1°<b<2°) and one below (-2°<b←1°) the Galactic
plane in the direction of the Galactic center at both X-ray and
optical wavelengths. By avoiding the Galactic plane (-1°<b<1°)
we limit the influence of extinction on the X-ray and optical emission
but still sample relatively large number densities of sources. The
survey is designed such that a large fraction of the X-ray sources can
be identified from their optical spectra. The X-ray survey, by design,
covers a large area on the sky while the depth is shallow using 2ks
per Chandra pointing. In this way we maximize the predicted number
ratio of (quiescent) LMXBs to cataclysmic variables. The survey is
approximately homogeneous in depth to a 0.5-10keV flux of
7.7x10-14erg/cm2/s. So far, we have covered about two-thirds
(8.3deg2) of the projected survey area with Chandra providing over
1200 unique X-ray sources. We discuss the characteristics and the
variability of the brightest of these sources.
Description:
The Chandra observations have been performed using the I0 to I3 CCDs
of the Advanced CCD Imaging Spectrometer (ACIS) detector. The
observation identification (ID) numbers for the data presented here
are 8643-8774 and 9977-10024. We also reprocessed and reanalyzed the
data that were obtained as part of the Bulge Latitude Survey (Grindlay
et al. 2005ApJ...635..920G 2005ApJ...635..920G; Hong et al. 2009ApJ...706..223H 2009ApJ...706..223H;
observation IDs 7160-7162, 7166-7168, 8199-8204, 9562-9564)
Optical imaging observations covering the full GBS area have been
obtained using the prime focus MOSAIC II instrument mounted on the 4m
Victor M. Blanco telescope at the Cerro Tololo Inter-American (CTIO)
observatory. We employed the Sloan r', i', and Hα filters with
exposures of 120, 180, and 480s, respectively.
For the optical astrometry we used the UCAC2 catalog (Zacharias et al.
2004, Cat. I/289, obsoleted by I/315).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 97 1234 The GBS X-ray source list
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-)
II/304 : UKIDSS-DR5 (Lawrence+ 2011)
II/293 : GLIMPSE Source Catalog (I + II + 3D) (IPAC 2008)
I/289 : UCAC2 Catalogue (Zacharias+ 2004)
IX/10 : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1999)
II/213 : OGLE Galactic Bulge periodic variables (Udalski+ 1996)
J/ApJ/685/463 : ChaMPlane X-ray sources in the Galactic bulge (Koenig+, 2008)
J/AN/324/437 : Hα emission stars toward Bulge (Kohoutek+, 2003)
J/AcA/52/217 : OGLE II. VI photometry of Galactic Bulge (Udalski+, 2002)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- --- [CXOGBS]
8- 23 A16 --- CXOGBS Source name (JHHMMSS.s+DDMMSS)
25- 28 I4 --- Seq [1/1234] Source index number
30- 41 F12.8 deg RAdeg Right Ascension in decimal degrees (J2000)
43- 55 F13.9 deg DEdeg Declination in decimal degrees (J2000)
57- 61 F5.3 arcsec e_RAdeg Error in RAdeg
63- 67 F5.3 arcsec e_DEdeg Error in DEdeg
69- 72 I4 ct Total Number of counts detected
74- 78 I5 --- ObsID Chandra observation identification number
80- 84 F5.2 arcmin OAxis Off-axis angle source detected
86 I1 --- Ndet Number of detections
88- 92 F5.2 --- HR ? Hardness ratio (1)
94- 97 F4.2 --- e_HR ? Error in HR
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Note (1): The HR is calculated for the detection where the off-axis angle
was smallest if the source was detected multiple times. HR is the
ratio between the count rate in the 2.5-8keV minus that in the
0.3-2.5keV band to the count rate in the full 0.3-8keV energy band.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 08-Aug-2011