Diffuse X-ray emission around an ultraluminous X-ray pulsar. (arXiv:1910.11876v1 [astro-ph.HE])

Diffuse X-ray emission around an ultraluminous X-ray pulsar. (arXiv:1910.11876v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Belfiore_A/0/1/0/all/0/1">Andrea Belfiore</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Esposito_P/0/1/0/all/0/1">Paolo Esposito</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pintore_F/0/1/0/all/0/1">Fabio Pintore</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Novara_G/0/1/0/all/0/1">Giovanni Novara</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Salvaterra_R/0/1/0/all/0/1">Ruben Salvaterra</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Luca_A/0/1/0/all/0/1">Andrea De Luca</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tiengo_A/0/1/0/all/0/1">Andrea Tiengo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Caraveo_P/0/1/0/all/0/1">Patrizia Caraveo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fuerst_F/0/1/0/all/0/1">Felix Fuerst</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Israel_G/0/1/0/all/0/1">Gian Luca Israel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Magistrali_D/0/1/0/all/0/1">Danilo Magistrali</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Marelli_M/0/1/0/all/0/1">Martino Marelli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mereghetti_S/0/1/0/all/0/1">Sandro Mereghetti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Papitto_A/0/1/0/all/0/1">Alessandro Papitto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Castillo_G/0/1/0/all/0/1">Guillermo Rodriguez Castillo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Salvaggio_C/0/1/0/all/0/1">Chiara Salvaggio</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stella_L/0/1/0/all/0/1">Luigi Stella</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Walton_D/0/1/0/all/0/1">Dominic Walton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wolter_A/0/1/0/all/0/1">Anna Wolter</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zampieri_L/0/1/0/all/0/1">Luca Zampieri</a>

Ultraluminous X-ray sources (ULXs) are extragalactic X-ray emitters located
off-center of their host galaxy and with a luminosity in excess of a few
${10^{39}text{ erg s}^{-1}}$, if emitted isotropically. The discovery of
periodic modulation revealed that in some ULXs the accreting compact object is
a neutron star, indicating luminosities substantially above their Eddington
limit. The most extreme object in this respect is ${NGC 5907~ULX-1}$ (ULX1),
with a peak luminosity that is 500 times its Eddington limit. During a Chandra
observation to probe a low state of ULX1, we detected diffuse X-ray emission at
the position of ULX1. Its diameter is $2.7 pm 1.0$ arcsec and contains 25
photons, none below 0.8 keV. We interpret this extended structure as an
expanding nebula powered by the wind of ULX1. Its diameter of about ${200text{
pc}}$, characteristic energy of ${sim 1.9text{ keV}}$, and luminosity of
${sim 2times10^{38}text{ erg s}^{-1}}$ imply a mechanical power of
${1.3times10^{41}text{ erg s}^{-1}}$ and an age ${sim 7 times 10^{4}text{
yr}}$. This interpretation suggests that a genuinely super-Eddington regime can
be sustained for time scales much longer than the spin-up time of the neutron
star powering the system. As the mechanical power from a single ULX nebula can
rival the injection rate of cosmic rays of an entire galaxy, ULX nebulae could
be important cosmic ray accelerators.

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