UV to X-ray Comptonization delay in Mrk 493. (arXiv:1812.08056v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Adegoke_O/0/1/0/all/0/1">Oluwashina Adegoke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dewangan_G/0/1/0/all/0/1">Gulab C. Dewangan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pawar_P/0/1/0/all/0/1">Pramod Pawar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pal_M/0/1/0/all/0/1">Main Pal</a>
The broadband X-ray emission from type 1 active galactic nuclei, dominated by
a powerlaw continuum, is thought to arise from repeated inverse Compton
scattering of seed optical/UV photons by energetic electrons in a hot corona.
The seed optical/UV photons are assumed to arise from an accretion disc but a
direct observational evidence has remained elusive. Here we report the
discovery of variations in the UV emission preceding the variations in the
X-ray emission based on $sim100,mathrm{ks}$ XMM-Newton observations of the
narrow-line Seyfert 1 galaxy Mrk 493. We find the UV emission to lead by
$sim5,mathrm{ks}$ relative to the X-ray emission. The UV lead is consistent
with the time taken by the UV photons to travel from the location of their
origin in the accretion disc to the hot corona and the time required for
repeated inverse Compton scattering converting the UV photons into X-ray
photons. Our findings provide first direct observational evidence for the
accretion disc to be responsible for the seed photons for thermal
Comptonization in the hot corona, and constrain the size of the corona to be
$sim20r_{g}$.
The broadband X-ray emission from type 1 active galactic nuclei, dominated by
a powerlaw continuum, is thought to arise from repeated inverse Compton
scattering of seed optical/UV photons by energetic electrons in a hot corona.
The seed optical/UV photons are assumed to arise from an accretion disc but a
direct observational evidence has remained elusive. Here we report the
discovery of variations in the UV emission preceding the variations in the
X-ray emission based on $sim100,mathrm{ks}$ XMM-Newton observations of the
narrow-line Seyfert 1 galaxy Mrk 493. We find the UV emission to lead by
$sim5,mathrm{ks}$ relative to the X-ray emission. The UV lead is consistent
with the time taken by the UV photons to travel from the location of their
origin in the accretion disc to the hot corona and the time required for
repeated inverse Compton scattering converting the UV photons into X-ray
photons. Our findings provide first direct observational evidence for the
accretion disc to be responsible for the seed photons for thermal
Comptonization in the hot corona, and constrain the size of the corona to be
$sim20r_{g}$.
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