J/ApJ/932/66 Insight-HXMT high energy X-ray obs. of EXO1846-031 (Ren+, 2022)
Insight-HXMT study of the inner accretion disk in the black hole candidate
EXO 1846-031.
Ren X.Q., Wang Y., Zhang S.N., Soria R., Tao L., Ji L., Yang Y.J.,
Qu J.L., Zhang S., Song L.M., Ge M.Y., Huang Y., Li X.B., Liao J.Y.,
Liu H.X., Ma R.C., Tuo Y.L., Wang P.J., Zhang W., Zhou D.K.
<Astrophys. J., 932, 66 (2022)>
=2022ApJ...932...66R 2022ApJ...932...66R
ADC_Keywords: X-ray sources; Black holes; Binaries, X-ray
Keywords: Black hole physics ; High energy astrophysics ; Accretion
Abstract:
We study the spectral evolution of the black hole candidate
EXO1846-031 during its 2019 outburst, in the 1-150keV band, with the
Hard X-ray Modulation Telescope. The continuum spectrum is well
modeled with an absorbed disk-blackbody plus cutoff power law, in the
hard, intermediate, and soft states. In addition, we detect an ∼6.6keV
Fe emission line in the hard intermediate state. Throughout the soft
intermediate and soft states, the fitted inner disk radius remains
almost constant; we suggest that it has settled at the innermost
stable circular orbit (ISCO). However, in the hard and hard
intermediate states, the apparent inner radius was unphysically small
(smaller than the ISCO), even after accounting for the Compton
scattering of some of the disk photons by the corona in the fit. We
argue that this is the result of a high hardening factor,
fcol∼2.0-2.7, in the early phases of the outburst evolution, well
above the canonical value of 1.7 suitable for a steady disk. We
suggest that the inner disk radius was already close to the ISCO in
the low/hard state. Furthermore, we propose that this high value of
the hardening factor in the relatively hard state was probably caused
by the additional illuminating of the coronal irradiation onto the
disk. Additionally, we estimate the spin parameter using the
continuum-fitting method, over a range of plausible black hole masses
and distances. We compare our results with the spin measured using the
reflection-fitting method and find that the inconsistency of the two
results is partly caused by different choices of fcol.
Description:
Following the MAXI/GSC (Negoro+ 2019ATel12968....1N 2019ATel12968....1N) discovery of a
new outburst of EXO 1846-031, we triggered the Hard X-ray Modulation
Telescope (Insight-HXMT) ToO observations, which covered 85 days, from
2019 August 2 to October 25 (Table 1).
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
18 49 17.10 -03 03 43.9 EXO 1846-031 = INTREF 939
----------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 86 82 Insight-HXMT observations of EXO 1846-031
table2.dat 158 80 Spectral fitting results of EXO 1846-031 using
TBabs*(cutoffpl+diskbb) model, NH fixed
at 5.34e+22cm-2
table3.dat 174 80 Spectral fitting results of EXO 1846-031 using
TBabs*(simplcut+diskbb) model, NH fixed
at 5.25e+22cm-2
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See also:
J/MNRAS/415/292 : MAXI J1659-152 2010 outburst analysis (Munoz-Darias+, 2011)
J/A+A/587/A61 : BlackCAT, stellar-mass BH in X-ray (Corral-Santana+, 2016)
J/ApJ/822/60 : RXTE observations of GRS 1915+105 (Peris+, 2016)
J/ApJS/222/15 : WATCHDOG: all-sky database of Gal. BHXBs (Tetarenko+, 2016)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I04 --- ExpID Exposure identifier (1)
6- 24 A19 "datime" Time Start time; YYYY-MM-DDThh:mm:ss.ss
26- 33 F8.2 d MJD [58697.35/58781.57] Modified Julian Date of
start time
35- 40 F6.2 ct/s HE [1.37/263.6] High energy, 25-150keV, count rate
42- 45 F4.2 ct/s e_HE [0.02/0.6] Uncertainty in HE
47- 51 F5.2 ct/s ME [0.9/52] Medium energy, 10-20keV, count rate
53- 56 F4.2 ct/s e_ME [0.02/0.5] Uncertainty in ME
58- 62 F5.1 ct/s LE [67.8/220.5] Low energy, 1-10keV, count rate
64- 66 F3.1 ct/s e_LE [0.2/1] Uncertainty in LE
68- 71 I4 s HEExp [264/4988] High energy band exposure time
73- 76 I4 s MEExp [287/3967] Medium energy band exposure time
78- 81 I4 s LEExp [239/2858] Low energy band exposure time
83- 86 A4 --- State Source state (2)
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Note (1): For example, 0101: P0214050XXXX, where XXXX=0101.
Note (2): Source state as follows:
LHS = low-hard state (8 occurrences)
HIMS = hard intermediate state (20 occurrences)
SIMS = soft intermediate state (8 occurrences)
HSS = high soft state (46 occurrences)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I04 --- ExpID [101/4903] Exposure identifier
6- 8 A3 --- Model Model identifier (G1)
10- 13 F4.2 --- Gamma [1.39/3] Photon index
15- 18 F4.2 --- E_Gamma [0.03/0.7] Upper uncertainty in Gamma
20- 23 F4.2 --- e_Gamma [0.04/0.6] Lower uncertainty in Gamma
25- 27 I3 keV Ecut [40/500] Energy cutoff
28 A1 --- f_Ecut [f] Flag on Ecut (G2)
30- 32 I3 keV E_Ecut [3/200]? Upper uncertainty in Ecut
33 A1 --- n_Ecut [p] Ecut is pagged at its upper limit
35- 37 I3 keV e_Ecut [3/300]? Lower uncertainty in Ecut
39- 43 F5.3 keV kTin [0.78/1.8] Color temperature
45- 49 F5.3 keV E_kTin [0.003/0.3] Upper uncertainty in kTin
51- 55 F5.3 keV e_kTin [0.003/0.3] Lower uncertainty in kTin
57- 60 I4 --- Ndbb [4/1300] Diskbb normalization
62- 63 I2 --- E_Ndbb [2/80] Upper uncertainty in Ndbb
65- 66 I2 --- e_Ndbb [2/80] Lower uncertainty in Ndbb
68- 70 F3.1 keV Egau [6.4/7]? Central energy of gaussian model
72- 74 F3.1 keV E_Egau [0.1/0.4]? Upper uncertainty in Egau
76- 78 F3.1 keV e_Egau [0.1/0.4]? Lower uncertainty in Egau
79 A1 --- n_Egau [p] Egau is pagged at its lower limit
81- 83 F3.1 keV sigma [0.4/1.6]? Line width of gaussian model
85- 87 F3.1 keV E_sigma [0.1/0.7]? Upper uncertainty in sigma
89- 91 F3.1 keV e_sigma [0.2/0.6]? Lower uncertainty in sigma
92 A1 --- n_sigma [u] Indicates sigma is unconstrained
94-104 A11 --- chi2/dof Model χ2/degrees of freedom
106-110 F5.3 10-8mW/m2 Fdbb [0.04/2.1] Disk component flux (G3)
112-116 F5.3 10-8mW/m2 E_Fdbb [0.006/0.1] Upper uncertainty in Fdbb
118-122 F5.3 10-8mW/m2 e_Fdbb [0.006/0.1] Lower uncertainty in Fdbb
124-128 F5.3 10-8mW/m2 Fpl [0.03/1.3] Power-law component flux (G3)
130-134 F5.3 10-8mW/m2 E_Fpl [0.005/0.5] Uncertainty in Fpl
136-140 F5.3 10-8mW/m2 e_Fpl [0.005/0.2] Uncertainty in Fpl
142-146 F5.3 --- fdbb [0.05/1] Disk flux fraction
148-152 F5.3 --- E_fdbb [0.005/0.1] Upper uncertainty in fdbb
154-158 F5.3 --- e_fdbb [0.005/0.06] Lower uncertainty in fdbb
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I04 --- ExpID [101/4903] Exposure identifier
6- 8 A3 --- Model Model identifier (G1)
10- 13 F4.2 --- Gamma [1.4/3] Photon index
15- 18 F4.2 --- E_Gamma [0.02/0.6] Upper uncertainty in Gamma
20- 23 F4.2 --- e_Gamma [0.02/0.7] Lower uncertainty in Gamma
25- 27 I3 keV Ecut [50/500] Energy cutoff
28 A1 --- f_Ecut [f] Flag on Ecut (G2)
30- 32 I3 keV E_Ecut [3/190]? Upper uncertainty in Ecut
33 A1 --- n_Ecut [p] Ecut is pagged at its upper limit
35- 37 I3 keV e_Ecut [3/300]? Lower uncertainty in Ecut
39- 43 F5.3 keV kTin [0.67/1.2] Color temperature
45- 49 F5.3 keV E_kTin [0.003/0.2] Upper uncertainty in kTin
51- 55 F5.3 keV e_kTin [0.003/0.3] Lower uncertainty in kTin
57- 60 I4 --- Ndbb [150/1400] Diskbb normalization
62- 64 I3 --- E_Ndbb [17/600] Upper uncertainty in Ndbb
66- 68 I3 --- e_Ndbb [16/300] Lower uncertainty in Ndbb
70- 74 F5.3 --- fsc [0.003/1] Scattered fraction
76- 80 F5.3 --- E_fsc [0.001/0.11] Upper uncertainty in fsc
82- 86 F5.3 --- e_fsc [0.001/0.12] Lower uncertainty in fsc
88- 90 F3.1 keV Egau [6.4/6.8]? Central energy of gaussian model
92- 94 F3.1 keV E_Egau [0.1/0.4]? Upper uncertainty in Egau
96- 98 F3.1 keV e_Egau [0.1/0.4]? Lower uncertainty in Egau
99 A1 --- n_Egau [p] Egau is pagged at its lower limit
101-103 F3.1 keV sigma [0.1/1.6]? Line width of gaussian model
105-107 F3.1 keV E_sigma [0.1/4.2]? Upper uncertainty in sigma
109-111 F3.1 keV e_sigma [0.1/0.6]? Lower uncertainty in sigma
113-123 A11 --- chi2/dof Model χ2/degrees of freedom
125-129 F5.3 10-8mW/m2 Fdbb [0.2/2.3] Disk component flux (G3)
131-135 F5.3 10-8mW/m2 E_Fdbb [0.007/0.12] Upper uncertainty in Fdbb
137-141 F5.3 10-8mW/m2 e_Fdbb [0.007/0.1] Lower uncertainty in Fdbb
143-147 F5.3 10-8mW/m2 Fpl [0.01/1.4] Power-law component flux (G3)
148-152 F5.3 10-8mW/m2 E_Fpl [0.02/0.12] Uncertainty in Fpl
153-157 F5.3 10-8mW/m2 e_Fpl [0.02/0.11] Uncertainty in Fpl
158-162 F5.3 --- fdbb [0.16/0.992] Disk flux fraction
164-168 F5.3 --- E_fdbb [0.007/0.07] Upper uncertainty in fdbb
170-174 F5.3 --- e_fdbb [0.008/0.05] Lower uncertainty in fdbb
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Global notes:
Note (G1): Model (see Section 3.2) as follows:
CD = cutoffpl+diskbb model
CDG = cutoffpl+diskbb+Gaussian model
SD = simplcut*diskbb model
SDG = simplcut*diskbb+gaussian model
Note (G2): Flag as follows:
f = fixed at 500keV in the soft intermediate state (SIMS) and the high
soft state (HSS).
Note (G3): Unabsorbed bolometric flux.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Mar-2025