J/ApJ/896/124 MAXI GSC X-ray LCs of the ULX Swift J0243.6+6124 (Sugizaki+, 2020)
X-ray emission evolution of the Galactic ultraluminous X-ray pulsar
Swift J0243.6+6124 during the 2017-2018 outburst observed by the MAXI GSC.
Sugizaki M., Oeda M., Kawai N., Mihara T., Makishima K., Nakajima M.
<Astrophys. J., 896, 124 (2020)>
=2020ApJ...896..124S 2020ApJ...896..124S
ADC_Keywords: Pulsars; Binaries, X-ray; X-ray sources
Keywords: Neutron stars ; Binary pulsars ; Accretion ;
High mass x-ray binary stars
Abstract:
This paper reports on the X-ray emission evolution of the
ultraluminous Galactic X-ray pulsar Swift J0243.6+6124 during the
giant outburst from 2017 October to 2018 January as observed by the
MAXI GSC all-sky survey. The 2-30keV light curve and the energy
spectra confirm the source luminosity LX assuming an isotropic
emission reached 2.5x1039erg/s, 10 times higher than the Eddington
limit for a 1.4M☉ neutron star. When the source was luminous
with LX≳0.9x1038erg/s, it generally exhibited a negative
correlation on a hardness-intensity diagram. However, two hardness
ratios, a soft color (=4-10keV/2-4keV) and a hard color
(=10-20keV/4-10keV), showed somewhat different behavior across a
characteristic luminosity of Lc∼5x1038erg/s. The soft color
changed more than the hard color when LX<Lc, whereas the opposite
was observed above Lc. The spectral change above Lc was represented by
a broad enhanced feature at ∼6keV on top of the canonical cutoff
power-law continuum. The pulse profiles, derived daily, made the
transition from a single-peak to a double-peak as the source
brightened across Lc. These spectral and pulse-shape properties can be
interpreted by a scenario in which the accretion columns on the
neutron-star surface, producing the Comptonized X-ray emission,
gradually became taller as LX increases. The broad 6keV enhancement
could be a result of cyclotron-resonance absorption at ∼10keV,
corresponding to a surface magnetic field Bs∼1.1x1012G. The
spin-frequency derivatives calculated with the Fermi GBM data showed a
smooth positive correlation with LX up to the outburst peak, and its
linear coefficient is comparable to those of typical Be binary pulsars
whose Bs are (1-8)x1012G. These results suggest that the Bs of
Swift J0243.6+6124 is a few times 1012G.
Description:
Swift J0243.6+6124 is a Be X-ray binary pulsar (XBP) discovered on
2017 October 3.
The long-term X-ray activity of Swift J0243.6+6124 has been
continuously monitored by all-sky X-ray instruments in orbit, i.e.,
the Monitor of All-sky X-ray Image (MAXI) Gas Slit Camera (GSC),
Swift/BAT, and Fermi/GBM.
Since 2009 August, the MAXI GSC on the International Space Station
(ISS) has been scanning almost the whole sky every 92 minute orbital
cycle in the 2-30keV band.
The present paper describes the GSC observation and the data analysis
of Swift J0243.6+6124 during the giant outburst from 2017 October to
2018 January.
Objects:
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RA (ICRS) DE Designation(s) Porb
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02 43 40.42 +61 26 03.8 Swift J0243.6+6124 = GRB 171003A (P=27.70)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig1.dat 112 351 X-ray light curves and hardness ratios of
Swift J0243.6+6124 observed by the MAXI GSC
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See also:
B/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-2014)
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
VIII/76 : Leiden/Argentine/Bonn (LAB) Survey of Galactic HI (Kalberla+ 2005)
J/ApJS/238/32 : 3rd MAXI/GSC X-ray cat at high Galactic lat. (Kawamuro+, 2018)
J/A+A/645/A18 : SVOM-ECLAIRs known X-ray sources catalogue (Dagoneau+, 2021)
J/A+A/645/L8 : Plx & proper motions of OB stars from Gaia EDR3 (Xu+, 2021)
Byte-by-byte Description of file: fig1.dat
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Bytes Format Units Label Explanations
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1- 7 F7.1 d MJD [58001.5/58393.5] Modified Julian Date
9- 17 F9.6 ct/cm2/s F2-4keV [-0.22/14.4] Photon flux 2-4keV band
19- 26 F8.6 ct/cm2/s e_F2-4keV [0.007/0.61] F2-4keV uncertainty
28- 36 F9.6 ct/cm2/s F4-10keV [-0.4/13.8] Photon flux 4-10keV band
38- 45 F8.6 ct/cm2/s e_F4-10keV [0.007/0.4] F4-10keV uncertainty
47- 55 F9.6 ct/cm2/s F10-20keV [-0.4/4.2] Photon flux 10-20keV band
57- 64 F8.6 ct/cm2/s e_F10-20keV [0.01/0.4] F10-20keV uncertainty
66- 75 F10.6 --- sCol [-26/154] 4-10keV/2-4keV hardness ratio
77- 88 F12.6 --- e_sCol [0.01/80158] SCol uncertainty
90- 99 F10.6 --- hCol [-49.7/16.4] 10-20keV/4-10keV hardness ratio
101-110 F10.6 --- e_hCol [0.006/474] HCol uncertainty
112 I1 --- Flag [0/1] Data quality flag 1=good
(246 occurrences), 0=degraded
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 29-Oct-2021