J/AcA/69/339 Hyperluminous X-ray source candidates (Singha+, 2019)
Bimodal distribution of the hyperluminous X-ray sources.
Singha A.C., Devi A.S.
<Acta Astron., 69, 339-360 (2019)>
=2019AcA....69..339S 2019AcA....69..339S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Binaries, X-ray
Keywords: galaxies: general - X-rays: binaries
Abstract:
163 X-ray point sources having luminosities in excess of 1038erg/s
within the energy range 0.3-10.0keV are identified in a sample of 50
galaxies observed by Chandra ACIS-S. 18 sources are found to have a
total (time integrated) background flux greater than 2 cts/arcsec2
and hence excluded from the analysis to avoid any possible
background/foreground contamination. The spectra of the remaining 145
sources are fitted using two spectral models - an absorbed power law
and an absorbed disk blackbody. We report the discovery of four
hyperluminous X-ray source candidates (X-ray luminosity:
LX>1041erg/s) - Src1, Src2, Src3 and Src22. In this study, a total
of 17 hyperluminous X-ray sources were identified. The spectra of 13
sources were found to be equally represented by both the models except
for three sources preferring the power law model and one source
preferring the disk blackbody model. It is found that the spectra of
seven hyperluminous X-ray sources are in the soft state with their
inner disk temperature (kTin) lying in the range of 0.19-0.56keV
(or power law photon index, Γ>3) and the remaining 10
hyperluminous X-ray sources are in hard state with kTin around
1.0-2.0keV (or power law photon index, Γ~=1.6). This shows a
clear bimodal distribution of the high luminosity X-ray sources and
hence they can be grouped into two distinct spectral classes. From the
disk blackbody model, the black hole masses of the soft hyperluminous
X-ray sources are estimated (assuming the inner disk radius,
Rin~=10GM/c2) to be within ~=103-104M☉. Also considering
an anisotropic emission, for maximum beaming (η=5) with no color
correction, the estimated black hole masses lie within
~=102-103M☉ , which is in the intermediate mass black hole
range.
Description:
The Chandra Advanced CCD Imaging Spectrometer (ACIS) offers the
capability to simultaneously acquire high-resolution images and
spectra. For the present work, we have used data from the Chandra
public data archive observed by the Chandra ACIS-S. A sample of 50
galaxies was selected, some of which have been chosen as the ones that
are released recently. Table 1 shows the list of the sample galaxies
and the observation details.
163 off-nuclear point sources having counts ∼100 or above were
detected from the sample of 50 galaxies. The properties of the X-ray
point sources are listed in Table 2.
145 X-ray point sources having counts ~=100 or above were considered
for the spectral analysis. Table 3 shows pile-up fraction and spectral
properties of the 14 pile-up affected sources. The spectral
parameters, derived with one-sigma confidence level for the remaining
131 sources fitted with both the absorbed power law and the absorbed
disk blackbody models, are listed in Table 4.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 96 50 Chandra ACIS-S galaxy observations
table2.dat 65 163 Properties of the X-ray point sources
table3.dat 97 14 Spectral properties of the pile-up
corrected sources
table4.dat 110 131 Spectral properties of the point sources
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- Target Target name
25- 29 I5 --- ObsID Observation ID
31- 40 A10 "date" Obs.date Observation date
42- 46 F5.1 ks Texp Exposure time
48- 52 F5.1 Mpc Dist Distance
54- 96 A43 --- Ref Reference
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Source Source Number (SrcNNN)
7- 8 A2 --- n_Source [* ] Note on Source (1)
11- 32 A22 --- Target Target galaxy name
34- 35 I2 h RAh Right ascension (J2000)
37- 38 I2 min RAm Right ascension (J2000)
40- 44 F5.2 s RAs Right ascension (J2000)
46 A1 --- DE- Declination sign (J2000)
47- 48 I2 deg DEd Declination (J2000)
50- 51 I2 arcmin DEm Declination (J2000)
53- 57 F5.2 arcsec DEs Declination (J2000)
59- 62 I4 ct Counts Counts
64- 65 I2 ct BkgCounts Background Counts
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Note (1): Note as follows:
* = Sources located in the region of diffuse emission
** = pile-up affected sources
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Source Source number (SrcNNN)
8- 11 F4.2 10+22cm-2 NHPL Power law Hydrogen column density
13- 18 F6.4 --- PufPL Power law pile-up fraction
20- 23 F4.2 --- GAMMAPL Power law photon index GAMMA
24 A1 --- --- [+]
25- 28 F4.2 --- E_GAMMAPL Power law photon index GAMMA upper error
29 A1 --- --- [-]
30- 33 F4.2 --- e_GAMMAPL Power law photon index GAMMA lower error
35- 39 F5.2 [10-7W] logLPL Power law luminosity
40 A1 --- --- [+]
41- 44 F4.2 [10-7W] E_logLPL Power law luminosity upper error
45 A1 --- --- [-]
46- 49 F4.2 [10-7W] e_logLPL Power law luminosity lower error
51- 54 F4.2 --- rchi2PL Power law reduced chi2
56- 61 F6.4 --- PufDB Pile-up fraction Disk blackbody
63- 66 F4.2 keV kTinDB Disk blackbody kTin temperature
67 A1 --- --- [+]
68- 71 F4.2 keV E_kTinDB Disk blackbody kTin temperature
upper error
72 A1 --- --- [-]
73- 76 F4.2 keV e_kTinDB Disk blackbody kTin temperature
lower error
78- 82 F5.2 [10-7W] logLDB Disk blackbody luminosity
83 A1 --- --- [+]
84- 87 F4.2 [10-7W] E_logLDB Disk blackbody luminosity upper error
88 A1 --- --- [-]
89- 92 F4.2 [10-7W] e_logLDB Disk blackbody luminosity lower error
94- 97 F4.2 --- rchi2DB Reduced chi Disk blackbody2
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Source Source Number (SrcNNN)
7 A1 --- n_Source [*] Note on source (1)
10- 13 F4.2 10+22cm-2 NHPL Power-law Hydrogen column density
14 A1 --- --- [+]
15- 18 F4.2 10+22cm-2 E_NHPL Power-law Hydrogen column density
upper error
19 A1 --- --- [-]
20- 23 F4.2 10+22cm-2 e_NHPL Power-law Hydrogen column density
lower error
25- 28 F4.2 --- GAMMAPL Power-law photon index GAMMA
29 A1 --- --- [+]
30- 33 F4.2 --- E_GAMMAPL Power-law photon index GAMMA upper error
34 A1 --- --- [-]
35- 38 F4.2 --- e_GAMMAPL Power-law photon index GAMMA lower error
40- 44 F5.2 [10-7W] logLPL Power-law luminosity
45 A1 --- --- [+]
46- 49 F4.2 [10-7W] E_logLPL Power-law luminosity upper error
50 A1 --- --- [-]
51- 54 F4.2 [10-7W] e_logLPL Power-law luminosity lower error
56- 59 F4.2 --- rC-statPL Power-law reduced C-stat
61- 64 F4.2 10+22cm-2 NHDB Disk blackbody Hydrogen column density
65 A1 --- --- [+]
66- 69 F4.2 10+22cm-2 E_NHDB Disk blackbody Hydrogen column density
upper error
70 A1 --- --- [-]
71- 74 F4.2 10+22cm-2 e_NHDB Disk blackbody Hydrogen column density
lower error
76- 79 F4.2 keV kTinDB Disk blackbody
80 A1 --- --- [+]
81- 84 F4.2 keV E_kTinDB Disk blackbody upper error
85 A1 --- --- [-]
86- 89 F4.2 keV e_kTinDB Disk blackbody lower error
91- 95 F5.2 [10-7W] logLDB Disk blackbody luminosity
96 A1 --- --- [+]
97-100 F4.2 [10-7W] E_logLDB Disk blackbody luminosity upper error
101 A1 --- --- [-]
102-105 F4.2 [10-7W] e_logLDB Disk blackbody luminosity lower error
107-110 F4.2 --- rC-statDB Disk blackbody reduced C-stat
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Note (1): Note as follows:
* = excluded Sources due to poor model fitting
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 22-May-2023