Analysis of the unconcentrated background of the EPIC-pn camera on board XMM-Newton. (arXiv:2012.02071v1 [astro-ph.IM])
<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:+Molendi_S/0/1/0/all/0/1">Silvano Molendi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rossetti_M/0/1/0/all/0/1">Mariachiara Rossetti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gastaldello_F/0/1/0/all/0/1">Fabio Gastaldello</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Salvetti_D/0/1/0/all/0/1">David Salvetti</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:+Bartalucci_I/0/1/0/all/0/1">Iacopo Bartalucci</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kuhl_P/0/1/0/all/0/1">Patrick K&#xfc;hl</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:+Ghizzardi_S/0/1/0/all/0/1">Simona Ghizzardi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tiengo_A/0/1/0/all/0/1">Andrea Tiengo</a>

Our understanding of the background of the EPIC/pn camera onboard XMM-Newton
is incomplete. This affects the study of extended sources and can influence the
predictions of the background of future X-ray missions. We provide new results
based on the analysis of the largest data set ever used. We focus on the
unconcentrated component of the EPIC/pn background – supposedly related to
cosmic rays interacting with the telescope. We find that the out-field of view
region of the pn detector is actually exposed to the sky. After cleaning from
the sky contamination, the unconcentrated background does not show significant
spatial variations and its time behaviour is anti-correlated with the solar
cycle. We find a very tight, linear correlation between unconcentrated
backgrounds detected in the EPIC/pn and MOS2 cameras: this permits the correct
evaluation of the pn unconcentrated background of each exposure on the basis of
MOS2 data, avoiding the use (as usual) of the contaminated pn regions. We find
a tight, linear correlation between the pn unconcentrated background and the
proton flux in the 630-970 MeV energy band measured by SOHO/EPHIN. Through this
relationship we quantify the contribution of cosmic ray interactions to the pn
unconcentrated background and we find a second source which contributes to the
pn unconcentrated background for a significant fraction (30%-70%), that does
not vary with time and is roughly isotropic. Hard X-ray photons of the CXB
satisfy all the known properties of this new component. Our findings provide an
important observational confirmation of simulation results on ATHENA.

Our understanding of the background of the EPIC/pn camera onboard XMM-Newton
is incomplete. This affects the study of extended sources and can influence the
predictions of the background of future X-ray missions. We provide new results
based on the analysis of the largest data set ever used. We focus on the
unconcentrated component of the EPIC/pn background – supposedly related to
cosmic rays interacting with the telescope. We find that the out-field of view
region of the pn detector is actually exposed to the sky. After cleaning from
the sky contamination, the unconcentrated background does not show significant
spatial variations and its time behaviour is anti-correlated with the solar
cycle. We find a very tight, linear correlation between unconcentrated
backgrounds detected in the EPIC/pn and MOS2 cameras: this permits the correct
evaluation of the pn unconcentrated background of each exposure on the basis of
MOS2 data, avoiding the use (as usual) of the contaminated pn regions. We find
a tight, linear correlation between the pn unconcentrated background and the
proton flux in the 630-970 MeV energy band measured by SOHO/EPHIN. Through this
relationship we quantify the contribution of cosmic ray interactions to the pn
unconcentrated background and we find a second source which contributes to the
pn unconcentrated background for a significant fraction (30%-70%), that does
not vary with time and is roughly isotropic. Hard X-ray photons of the CXB
satisfy all the known properties of this new component. Our findings provide an
important observational confirmation of simulation results on ATHENA.

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