XMM-Newton observations of the extremely X-ray luminous quasar CFHQS J142952+544717=SRGE J142952.1+544716 at redshift z=6.18. (arXiv:2011.13724v2 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Medvedev_P/0/1/0/all/0/1">P. Medvedev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gilfanov_M/0/1/0/all/0/1">M. Gilfanov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sazonov_S/0/1/0/all/0/1">S. Sazonov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schartel_N/0/1/0/all/0/1">N. Schartel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sunyaev_R/0/1/0/all/0/1">R. Sunyaev</a>
We present results from a 20 ks XMM-Newton DDT observation of the radio-load
quasar CFHQS J142952+544717 at z=6.18, whose extreme X-ray luminosity was
recently revealed by the SRG/eROSITA telescope in the course of its first
all-sky survey. The quasar has been confidently detected with a total of $sim
1400$ net counts in the 0.2-10 keV energy band (1.4 to 72 keV in the object’s
rest frame). Its measured spectrum is unusually soft and can be described by an
absorbed power-law model with a photon index of $Gamma = 2.5pm0.2$. There are
no signs of a high-energy cutoff or reflected component, with an 90 % upper
limit on the fluorescence iron K$alpha$ equivalent width of $approx 290$ eV
and the corresponding upper limit on the iron K-edge absorption depth of 0.6.
We have detected, at the $> 95%$ confidence level, an excess absorption above
the Galactic value, corresponding to a column density $N_H= 3pm2 times
10^{22}$ cm$^{-2}$ of material located at z=6.18. The intrinsic luminosity of
CFHQS J142952+544717 in the 1.4 to 72 keV energy band is found to be
$5.5_{-0.6}^{+0.8} times 10^{46}$ erg s$^{-1}$. We did not detect
statistically significant flux changes between two SRG scans and the XMM-Newton
observation, spanning over $sim 7.5$ months, implying that the quasar remained
at this extremely high luminosity level for at least a month in its rest frame.
We put forward the hypothesis that the extreme X-ray properties of CFHQS
J142952+544717 are associated with inverse Compton scattering of cosmic
microwave background photons (at z=6.18) in its relativistic jets.
We present results from a 20 ks XMM-Newton DDT observation of the radio-load
quasar CFHQS J142952+544717 at z=6.18, whose extreme X-ray luminosity was
recently revealed by the SRG/eROSITA telescope in the course of its first
all-sky survey. The quasar has been confidently detected with a total of $sim
1400$ net counts in the 0.2-10 keV energy band (1.4 to 72 keV in the object’s
rest frame). Its measured spectrum is unusually soft and can be described by an
absorbed power-law model with a photon index of $Gamma = 2.5pm0.2$. There are
no signs of a high-energy cutoff or reflected component, with an 90 % upper
limit on the fluorescence iron K$alpha$ equivalent width of $approx 290$ eV
and the corresponding upper limit on the iron K-edge absorption depth of 0.6.
We have detected, at the $> 95%$ confidence level, an excess absorption above
the Galactic value, corresponding to a column density $N_H= 3pm2 times
10^{22}$ cm$^{-2}$ of material located at z=6.18. The intrinsic luminosity of
CFHQS J142952+544717 in the 1.4 to 72 keV energy band is found to be
$5.5_{-0.6}^{+0.8} times 10^{46}$ erg s$^{-1}$. We did not detect
statistically significant flux changes between two SRG scans and the XMM-Newton
observation, spanning over $sim 7.5$ months, implying that the quasar remained
at this extremely high luminosity level for at least a month in its rest frame.
We put forward the hypothesis that the extreme X-ray properties of CFHQS
J142952+544717 are associated with inverse Compton scattering of cosmic
microwave background photons (at z=6.18) in its relativistic jets.
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