A1 Vertaisarvioitu alkuperäisartikkeli tieteellisessä lehdessä
High-energy characteristics of the accretion-powered millisecond pulsar IGR J17591-2342 during its 2018 outburst: XMM-Newton, NICER, NuSTAR, and INTEGRAL view of the 0.3-300 keV X-ray band
Tekijät: L. Kuiper, S.S. Tsygankov, M. Falanga, I.A. Mereminskiy, D.K. Galloway, J. Poutanen, Z. Li
Kustantaja: EDP SCIENCES S A
Julkaisuvuosi: 2020
Journal: Astronomy and Astrophysics
Tietokannassa oleva lehden nimi: ASTRONOMY & ASTROPHYSICS
Lehden akronyymi: ASTRON ASTROPHYS
Artikkelin numero: ARTN A37
Vuosikerta: 641
Sivujen määrä: 15
ISSN: 0004-6361
eISSN: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202037812
Rinnakkaistallenteen osoite: https://research.utu.fi/converis/portal/detail/Publication/51022207
IGR J17591−2342 is an accreting millisecond X-ray pulsar, discovered with INTEGRAL, which went into outburst around July 21,
2018. To better understand the physics acting in these systems during the outburst episode, we performed detailed temporal-, timing-,
and spectral analyses across the 0.3–300 keV band using data from NICER, XMM-Newton, NuSTAR, and INTEGRAL. The hard
X-ray 20–60 keV outburst profile covering ∼85 days is composed of four flares. Over the course of the maximum of the last flare,
we discovered a type-I thermonuclear burst in INTEGRAL JEM-X data, posing constraints on the source distance. We derived a
distance of 7.6±0.7 kpc, adopting Eddington-limited photospheric radius expansion and assuming anisotropic emission. In the timing
analysis, using all NICER 1–10 keV monitoring data, we observed a rather complex set of behaviours starting with a spin-up period
(MJD 58345–58364), followed by a frequency drop (MJD 58364–58370), an episode of constant frequency (MJD 58370–58383),
concluded by irregular behaviour till the end of the outburst. The 1–50 keV phase distributions of the pulsed emission, detected
up to ∼120 keV using INTEGRAL ISGRI data, was decomposed in three Fourier harmonics showing that the pulsed fraction of
the fundamental increases from ∼10% to ∼17% going from ∼1.5 to ∼4 keV, while the harder photons arrive earlier than the soft
photons for energies .10 keV. The total emission spectrum of IGR J17591−2342 across the 0.3–150 keV band could adequately be
fitted in terms of an absorbed compPS model yielding as best fit parameters a column density of NH = (2.09 ± 0.05) × 1022 cm−2
, a
blackbody seed photon temperature kTbb,seed of 0.64±0.02 keV, electron temperature kTe = 38.8±1.2 keV and Thomson optical depth
τT = 1.59 ± 0.04. The fit normalisation results in an emission area radius of 11.3 ± 0.5 km adopting a distance of 7.6 kpc. Finally, the
results are discussed within the framework of accretion physics- and X-ray thermonuclear burst theory
Ladattava julkaisu This is an electronic reprint of the original article. |  |
