J/ApJ/678/102 BAT X-ray survey. I. (Ajello+, 2008)
BAT X-ray survey. I. Methodology and X-ray identification.
Ajello M., Greiner J., Kanbach G., Rau A., Strong A.W., Kennea J.A.
<Astrophys. J., 678, 102-115 (2008)>
=2008ApJ...678..102A 2008ApJ...678..102A
ADC_Keywords: Surveys ; X-ray sources ; Active gal. nuclei ; Gamma ray
Mission_Name: Swift
Keywords: galaxies: active - surveys - X-rays: binaries - X-rays: galaxies
Abstract:
We applied the maximum likelihood (ML) method, as an image
reconstruction algorithm, to the BAT (Burst Alert Telescope) X-Ray
Survey (BXS). This method was specifically designed to preserve the
full statistical information in the data and to avoid mosaicking of
many exposures with different pointing directions, thus reducing
systematic errors when co-adding images. We reconstructed, in the
14-170keV energy band, the image of a 90x90deg2 sky region, centered
on (RA, DE)=(105°, -25°), which BAT surveyed with an exposure
time of ∼1Ms (in 2005 November). The best sensitivity in our image is
∼0.85mCrab or 2.0x10-11ergs/cm2. We detect 49 hard X-ray sources
above the 4.5σ level; of these, only 12 were previously known as
hard X-ray sources (>15keV). Swift XRT observations allowed us to
firmly identify the counterparts for 15 objects, while 2 objects have
Einstein IPC counterparts (Harris et al., 1990, in Imaging X-Ray
Astronomy. A Decade of Achievements, ed. M. Elvis (Cambridge:
Cambridge Univ. Press), 309); in addition to those, we found a likely
counterpart for 13 objects by correlating our sample with the ROSAT
All-Sky Survey Bright Source Catalog (Voges et al., 1999, Cat.
IX/10). Seven objects remain unidentified.
Description:
We used 8 months of data, from 2005 April (when BAT data became
public) to 2005 November. In order to secure optical follow-up with a
dedicated observing campaign at La Silla, Chile, in 2006 January, we
selected only observations with angular separation less than 45°
from the zenith (RA, DE)=(105°, -25°).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 114 45 Detected hard X-ray sources
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See also:
J/ApJ/633/L77 : SWIFT/BAT detections of AGN (Markwardt+, 2005)
J/ApJ/673/96 : BAT X-ray Survey - III (Ajello+, 2008)
J/ApJ/681/113 : a faire
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- SWIFT Swift identification (JHHMM.m+DDMM)
14- 21 F8.4 deg RAdeg Right Ascension in degrees (J2000)
23- 30 F8.4 deg DEdeg Declination in degrees (J2000)
32- 36 F5.2 10-14W/m2 Flux Observed flux (14-170keV) (10-11erg/cm2/s)
38- 42 F5.2 --- S/N Signal-to-Noise ratio
44- 46 I3 100ks Exp Exposure time
48- 65 A18 --- OID Counterpart identification
67 A1 --- f_OID [b] Source identified from ROSAT (1)
69- 71 F3.1 arcmin Off ? Offset from Swift and other
identification positions
73- 79 A7 --- Type Source type
81- 87 A7 --- Cat Catalog/Instrument used for identification (2)
89 A1 --- n_Cat [cde] Notes about associations (3)
91- 92 I2 h RAXh ? X-ray telescope (XRT) Right Ascension (J2000)
94- 95 I2 min RAXm ? X-ray telescope (XRT) Right Ascension (J2000)
97-100 F4.1 s RAXs ? X-ray telescope (XRT) Right Ascension (J2000)
102 A1 --- DEX- X-ray telescope (XRT) Declination sign (J2000)
103-104 I2 deg DEXd ? X-ray telescope (XRT) Declination (J2000)
106-107 I2 arcmin DEXm ? X-ray telescope (XRT) Declination (J2000)
109-112 F4.1 arcsec DEXs ? X-ray telescope (XRT) Declination (J2000)
114 A1 --- Ref Reference code for XRT position (4)
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Note (1): b = Source identified thanks to its proximity to a ROSAT Bright
Source (Cat. IX/10) with the method described in the text
Note (2): Sources are abbreviated as follows:
R = ROSAT catalog
I = INTEGRAL catalog
H = HEAO-1 catalog
E = Einstein IPC catalog
X = X-ray telescope onbard Swifth observations
Note (3): Flag on Cat as follows:
c = 3C 227 was detected in a long (11ks) ROSAT-PSPC observations
(Crawford & Fabian, 1995MNRAS.273..827C 1995MNRAS.273..827C)
d = Source J0811.5+0937 has a ROSAT counterpart, 1WGA J0811.5+0933,
reported in the WGA catalog (White et al., 1994BAAS...26.1372W 1994BAAS...26.1372W).
This source coincides with RX J081132.4+093403.
e = Object has a ROSAT source in the error box, however the
association has to be proven.
Note (4): Reference code as follows:
1 = Tueller et al. (2005ATel..668....1T 2005ATel..668....1T, 2005ATel..669....1T 2005ATel..669....1T)
2 = Kennea et al. (2005ATel..677....1K 2005ATel..677....1K)
3 = Ajello et al. (2006ATel..697....1A 2006ATel..697....1A)
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 18-Sep-2009