The 2019 super-Eddington outburst of RX J0209.6-7427: Detection of pulsations and constraints on the magnetic field strength. (arXiv:2004.03022v1 [astro-ph.HE])

The 2019 super-Eddington outburst of RX J0209.6-7427: Detection of pulsations and constraints on the magnetic field strength. (arXiv:2004.03022v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Vasilopoulos_G/0/1/0/all/0/1">G. Vasilopoulos</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ray_P/0/1/0/all/0/1">P. S. Ray</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gendreau_K/0/1/0/all/0/1">K. C. Gendreau</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jenke_P/0/1/0/all/0/1">P. A. Jenke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jaisawal_G/0/1/0/all/0/1">G. K. Jaisawal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wilson_Hodge_C/0/1/0/all/0/1">C. A. Wilson-Hodge</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Strohmayer_T/0/1/0/all/0/1">T. E. Strohmayer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Altamirano_D/0/1/0/all/0/1">D. Altamirano</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Iwakiri_W/0/1/0/all/0/1">W. B. Iwakiri</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wolff_M/0/1/0/all/0/1">M. T. Wolff</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Guillot_S/0/1/0/all/0/1">S. Guillot</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Malacaria_C/0/1/0/all/0/1">C. Malacaria</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stevens_A/0/1/0/all/0/1">A. L. Stevens</a>

In November 2019, MAXI detected an X-ray outburst from the known Be X-ray
binary system RX J0209.6-7427 located in the outer wing of the Small Magellanic
Cloud. We followed the outburst of the system with NICER which led to the
discovery of X-ray pulsations with a period of 9.3 s. We analyzed simultaneous
X-ray data obtained with NuSTAR and NICER allowing us to characterize the
spectrum and provide an accurate estimate of its bolometric luminosity. During
the outburst the maximum broadband X-ray luminosity of the system reached
$1-2times10^{39}$ erg/s, thus exceeding by about one order of magnitude the
Eddington limit for a typical 1.4 $M_{odot}$ mass neutron star (NS).
Monitoring observations with Fermi/GBM and NICER allowed us to study the spin
evolution of the NS and compare it with standard accretion torque models. We
found that the NS magnetic field should be of the order of $3times10^{12}$ G.
We conclude that RX J0209.6-7427 exhibited one of the brightest outbursts
observed from a Be X-ray binary pulsar in the Magellanic Clouds, reaching
similar luminosity level to the 2016 outburst of SMC X-3. Despite the
super-Eddington luminosity of RX J0209.6-7427, the NS appears to have only a
moderate magnetic field strength.

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