J/A+A/344/521 LMC variable X-ray sources (Haberl+, 1999)
Variable X-ray sources in the LMC region observed by the ROSAT PSPC.
Haberl F., Pietsch W.
<Astron. Astrophys. 344, 521 (1999)>
=1999A&A...344..521H 1999A&A...344..521H
ADC_Keywords: X-ray sources ; Magellanic Clouds
Mission_Name: ROSAT
Keywords: stars: variables: general - X-rays: stars -
galaxies: stellar content - galaxies: Magellanic Clouds
Abstract:
The ROSAT PSPC (Cat. IX/11) performed more than 200 pointed
observations of the Large Magellanic Cloud (LMC) between 1990 and
1994. Most of the LMC was covered more than once and a large fraction
at least ten times, making the PSPC observations an in valuable
archive to study long-term time variability in the LMC. We performed a
systematic search for variable X-ray sources in the LMC and found 27
sources which showed flux variations by factors between 3 and more
than 1000. A comparison of the temporal and spectral characteristics
of 15 X-ray sources which are not yet identified optically with those
of the previously known sources in our sample allows to draw first
conclusions about their nature. Up to six of the unidentified sources
are promising candidates for high mass X-ray binaries in the LMC. Six
sources are probably foreground stars, two soft objects might be
supersoft sources and one source could be a black hole candidate. Most
of the X-ray binary candidates are found in the area of the LMC 4
supergiant shell leading to a significant concentration of such
systems in that region, consistent with the idea of being born in the
stellar formation event which created the shell.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 100 28 Variable sources in the LMC region. I.
table2.dat 91 28 Variable sources in the LMC region II.
tables.tex 130 135 LaTeX version of the tables
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See also:
IX/11 : ROSAT PSPC Source Catalog (Voges+ 1994)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- [HP99] Catalogue entry
6- 7 I2 h RAh Right ascension (J2000.0)
9- 10 I2 min RAm Right ascension (J2000.0)
12- 15 F4.1 s RAs Right ascension (J2000.0)
17 A1 --- DE- Declination sign (J2000.0)
18- 19 I2 deg DEd Declination (J2000.0)
21- 22 I2 arcmin DEm Declination (J2000.0)
24- 25 I2 arcsec DEs Declination (J2000.0)
26 A1 --- Note [a] Note on coordinates and r90 (1)
28- 31 F4.1 arcsec r90 90% statistical position uncertainty, the
systematic error is ∼7"
33 I1 --- E Energy band of detection (2)
35- 41 E7.2 ct/s CountRate Count rate in broad band E
43- 48 E6.1 ct/s e_CountRate rms uncertainty on CountRate
50- 54 F5.2 --- HR1 Hardness ratios HR1=(hard-soft)/(hard+soft)
56- 59 F4.2 --- e_HR1 ? rms uncertainty on HR1
60 A1 --- n_HR1 [b] Note on HR1 (3)
61- 65 F5.2 --- HR2 ? Hardness ratio
HR2=(hard2-hard1)/(hard2+hard1)
67- 70 F4.2 --- e_HR2 ? rms uncertainty on HR2
72- 75 F4.1 arcmin Off Off-axis angle
77- 85 A9 --- Obs ROSAT Observation identifier
87- 93 E7.2 ct/s SRate Survey count rate from Pietsch et al. (1999,
in prep.)
95-100 E6.1 ct/s e_SRate ? rms uncertainty on SRate (4)
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Note (1): a: Improved coordinates derived from HRI observation
Note (2): the bands are coded as follows:
1: soft, 0.1-0.4keV
2: hard, 0.5-2.0keV
3: hard1, 0.5-0.9keV
4: hard2, 0.9-2.0keV
5: broad, 0.1-2.4keV
Note (3): b: Only counts in soft band
Note (4): Rates without errors are 2σ upper limits
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- [HP99] Catalogue entry
6- 9 F4.2 10-2ct/s Ul ? Lowest upper limit
11- 15 F5.3 ct/s Min ? Detection minimum
17- 22 F6.3 ct/s Max ? Detection maximum
24- 29 F6.3 ct/s Sup ? Highest detection influenced by support
structure (which gives a lower limit)
31 A1 --- l_Var Limit flag on Var
32- 36 F5.1 --- Var Variability
37 A1 --- n_Var [a] Note on Var (1)
39 A1 --- l_Prob Limit flag on Prob
40- 42 F3.1 --- Prob ? Probability for variability in σ
(not given if higher than 6)
44- 45 I2 --- Ng Number of good detections, used for the
variability study
47 I1 --- Ns Number of detections near WSS, used for the
variability study
49- 50 I2 --- Nu Number of upper limits, used for the
variability study
52- 91 A40 --- Rem Remarks (2)
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Note (1): Variability amplitude (and also the confidence of the variability)
increases when including survey detections (source 436: var = 1240;
1093: 16) or HRI results (569: 44; 914: 16; 1225: 11)
Note (2): The RASS numbers denote the source number from the all-sky
LMC source catalogue of Pietsch et al. (1999, in prep.), Fg stands for
Foreground.
References:
D96: Dennerl et al., 1996, in Proceedings of "Roentgenstrahlung
from the Universe", Sept. 25-29 1995, MPE Report 263, 131
H95a: Haberl et al., 1995A&A...302L...1H 1995A&A...302L...1H
H95b: Haberl et al., 1995A&A...303L..49H 1995A&A...303L..49H
H97: Haberl et al., 1997A&A...318..490H 1997A&A...318..490H
M93: Mavromatakis & Haberl, 1993A&A...274..304M 1993A&A...274..304M
S94: Schmidtke et al., 1994PASP..106..843S 1994PASP..106..843S
W91: Wang et al., 1991ApJ...374..475W 1991ApJ...374..475W
O97: Orio et al., 1997A&A...325L...1O 1997A&A...325L...1O
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Acknowledgements: Frank Haberl
(End) Patricia Bauer [CDS] 10-Jun-1999