Detailed X-ray spectroscopy of the magnetar 1E 2259+586. (arXiv:1904.07553v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Pizzocaro_D/0/1/0/all/0/1">D. Pizzocaro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tiengo_A/0/1/0/all/0/1">A. Tiengo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mereghetti_S/0/1/0/all/0/1">S. Mereghetti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Turolla_R/0/1/0/all/0/1">R. Turolla</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Esposito_P/0/1/0/all/0/1">P. Esposito</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stella_L/0/1/0/all/0/1">L. Stella</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zane_S/0/1/0/all/0/1">S. Zane</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rea_N/0/1/0/all/0/1">N. Rea</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zelati_F/0/1/0/all/0/1">F. Coti Zelati</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Israel_G/0/1/0/all/0/1">G. Israel</a>
Magnetic field geometry is expected to play a fundamental role in magnetar
activity. The discovery of a phase-variable absorption feature in the X-ray
spectrum of SGR 0418+5729, interpreted as cyclotron resonant scattering,
suggests the presence of very strong non-dipolar components in the magnetic
fields of magnetars. We performed a deep XMM-Newton observation of pulsar 1E
2259+586, to search for spectral features due to intense local magnetic fields.
In the phase-averaged X-ray spectrum, we found evidence for a broad absorption
feature at very low energy (0.7 keV). If the feature is intrinsic to the
source, it might be due to resonant scattering/absorption by protons close to
star surface. The line energy implies a magnetic field of ~ 10^14 G, roughly
similar to the spin-down measure, ~ 6×10^13 G. Examination of the X-ray
phase-energy diagram shows evidence for a further absorption feature, the
energy of which strongly depends on the rotational phase (E >~ 1 keV ). Unlike
similar features detected in other magnetar sources, notably SGR 0418+5729, it
is too shallow and limited to a small phase interval to be modeled with a
narrow phase-variable cyclotron absorption line. A detailed phase-resolved
spectral analysis reveals significant phase-dependent variability in the
continuum, especially above 2 keV. We conclude that all the variability with
phase in 1E 2259+586 can be attributed to changes in the continuum properties
which appear consistent with the predictions of the Resonant Compton Scattering
model.
Magnetic field geometry is expected to play a fundamental role in magnetar
activity. The discovery of a phase-variable absorption feature in the X-ray
spectrum of SGR 0418+5729, interpreted as cyclotron resonant scattering,
suggests the presence of very strong non-dipolar components in the magnetic
fields of magnetars. We performed a deep XMM-Newton observation of pulsar 1E
2259+586, to search for spectral features due to intense local magnetic fields.
In the phase-averaged X-ray spectrum, we found evidence for a broad absorption
feature at very low energy (0.7 keV). If the feature is intrinsic to the
source, it might be due to resonant scattering/absorption by protons close to
star surface. The line energy implies a magnetic field of ~ 10^14 G, roughly
similar to the spin-down measure, ~ 6×10^13 G. Examination of the X-ray
phase-energy diagram shows evidence for a further absorption feature, the
energy of which strongly depends on the rotational phase (E >~ 1 keV ). Unlike
similar features detected in other magnetar sources, notably SGR 0418+5729, it
is too shallow and limited to a small phase interval to be modeled with a
narrow phase-variable cyclotron absorption line. A detailed phase-resolved
spectral analysis reveals significant phase-dependent variability in the
continuum, especially above 2 keV. We conclude that all the variability with
phase in 1E 2259+586 can be attributed to changes in the continuum properties
which appear consistent with the predictions of the Resonant Compton Scattering
model.
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