J/other/Sci/292.2290 Chandra compact binaries in 47 Tuc (Grindlay+, 2001)
High-resolution X-ray imaging of a globular cluster core:
compact binaries in 47 Tuc
Grindlay J.E., Heinke C., Edmonds P.D., Murray S.S.
<Science, 292, 2290 (2001)>
=2001Sci...292.2290G 2001Sci...292.2290G
ADC_Keywords: Clusters, globular ; X-ray sources ; Binaries, X-ray
Mission_Name: Chandra
Abstract:
We have obtained high-resolution (≲1") deep X-ray images of the
globular cluster 47 Tucanae (NGC 104) with the Chandra X-ray
Observatory to study the population of compact binaries in the high
stellar density core. A 70-kilosecond exposure of the cluster reveals
a centrally concentrated population of faint (LX∼1030-33ergs/s)
X-ray sources, with at least 108 located within the central 2'x2.5'
and ≳half with LX≲1030.5ergs/s. All 15 millisecond pulsars
(MSPs) recently located precisely by radio observations are
identified, though 2 are unresolved by Chandra. The X-ray spectral and
temporal characteristics, as well as initial optical identifications
with the Hubble Space Telescope, suggest that ≳50 percent are MSPs,
about 30 percent are accreting white dwarfs, about 15 percent are
main-sequence binaries in flare outbursts, and only two to three are
quiescent low-mass X-ray binaries containing neutron stars, the
conventional progenitors of MSPs. An upper limit of about 470 times
the mass of the sun is derived for the mass of an accreting central
black hole in the cluster. These observations provide the first X-ray
``color-magnitude'' diagram for a globular cluster and census of its
compact object and binary population.
Observations were made on UT 16.31 - 17.22 March, 2000.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 85 108 47 Tuc X-Ray Source Parameters (MS 61135)
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- [GHE2001] Chandra source number (WNNN)
6 I1 h RAh Right ascension (J2000)
8- 9 I2 min RAm Right ascension (J2000)
11- 16 F6.3 s RAs Right ascension (J2000)
18- 22 F5.3 s e_RAs ? rms uncertainty on RA (1)
24 A1 --- DE- Declination sign (J2000)
25- 26 I2 deg DEd Declination (J2000)
28- 29 I2 arcmin DEm Declination (J2000)
31- 35 F5.2 arcsec DEs DEclination (J2000)
37- 40 F4.2 arcsec e_DEs ? rms uncertainty on DE (1)
42- 48 F7.1 ct Medcts Counts in 0.5-4.5 keV band (2)
50- 55 F6.1 ct Sfcts Counts in 0.5-1.5 keV band (2)
57- 62 F6.1 ct Hdcts Counts in 1.5-6 keV band (2)
64- 68 F5.2 --- Sf/Hd Softness ratio, defined as Sfcts/Hdcts
70- 75 E6.2 10-7W LX Intrinsic luminosities in ROSAT (0.5-2.5keV)
band (3)
77- 86 A10 --- ID Identification (4)
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Note (1): Errors are formal 1σ centroiding errors from Chandra
X-ray detection routine wavdetect. The final five millisecond pulsars
were not formally detected by wavdetect, so the radio positions of
Freire et al., 2001MNRAS.326..901F 2001MNRAS.326..901F are given without errors.
Note (2): Values of 0.5 counts are estimated upper limits.
Note (3): Intrinsic luminosities in ROSAT (0.5-2.5 keV) band, with
multiplicative exposure corrections (=1.4, 2.0, 1.7, 2.6, 1.2, 2.5 and
1.9 for sources W63(MSPJ), W65, W88, W89, W90, MSPC and MSPM,
respectively), based on 1keV thermal bremsstrahlung
spectrum,NH=2.4x1020cm-2, d=5.0kpc
Note (4): X number from ROSAT (Verbunt & Hasinger, 1998A&A...336..895V 1998A&A...336..895V)
observations (e.g. X5), certain optical or radio counterparts (e.g.
V1, AKO9, MSP-D), and class identifications:
qLMXB=quiescent LMXB,
M-S=main sequence binary,
CV=cataclysmic variable.
Detailed discussion of individual X-ray source spectra and variability
is deferred to Heinke et al. (2003ApJ...588..452H 2003ApJ...588..452H) and probable
optical counterparts are discussed by Edmonds et al.
(2002ApJ...579..741E 2002ApJ...579..741E)
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History:
From electronic version of the journal
(End) Patricia Bauer [CDS] 31-Jan-2002