The X-ray Background Emission of the Galactic Center and Bulge with NuSTAR. (arXiv:2008.12393v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kuznetsova_E/0/1/0/all/0/1">Ekaterina Kuznetsova</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Krivonos_R/0/1/0/all/0/1">Roman Krivonos</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Perez_K/0/1/0/all/0/1">Kerstin Perez</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Wik_D/0/1/0/all/0/1">Daniel R. Wik</a> (3) ((1) Space Research Institute of the Russian Academy of Sciences (IKI), Moscow, Russia, (2) Department of Physics, Massachusetts Institute of Technology, Cambridge, USA, (3) Department of Physics and Astronomy, University of Utah, Salt Lake City, USA)
The Galactic diffuse X-ray emission (GDXE) is believed to arise from
unresolved populations of numerous low-luminosity X-ray binary systems that
trace stellar mass distribution of the Milky Way. Many dedicated studies
carried out over the last decade suggest that a dominant contributor to GDXE is
a population of accreting white dwarfs (WDs). The question arises about
relative contribution of different subclasses of accreting WD population,
namely non-magnetic WD binaries, magnetic intermediate polars (IPs) and polars,
in different regions of the Galaxy: the Galactic center, bulge, and ridge.
Recent low-energy (E$<10$ keV) studies indicate that non-magnetic WD binaries,
in particular quiescent dwarf novae, provide a major contribution to the
diffuse hard X-ray emission of the Galactic bulge. From the other side,
previous high energy (E$>10$ keV) X-ray measurements of the bulge and ridge
imply a dominant population of magnetic CVs, in particular intermediate polars.
In this work we use side aperture of the NuSTAR to probe the diffuse continuum
of the inner $sim1-3^{circ}$ of the Galactic bulge, which allows us to
constrain possible mixture of soft and hard populations components of the
spectrum. We found that GDXE spectrum is well-described by a single-temperature
thermal plasma with $kT approx 8$ keV, which supports that the bulge is
dominated by quiescent dwarf novae with no evidence of a significant
intermediate polar population in the hard X-ray band. We also compare this
result with previous NuSTAR measurements of the inner 10 pc and inner 100 pc of
the Galactic center.
The Galactic diffuse X-ray emission (GDXE) is believed to arise from
unresolved populations of numerous low-luminosity X-ray binary systems that
trace stellar mass distribution of the Milky Way. Many dedicated studies
carried out over the last decade suggest that a dominant contributor to GDXE is
a population of accreting white dwarfs (WDs). The question arises about
relative contribution of different subclasses of accreting WD population,
namely non-magnetic WD binaries, magnetic intermediate polars (IPs) and polars,
in different regions of the Galaxy: the Galactic center, bulge, and ridge.
Recent low-energy (E$<10$ keV) studies indicate that non-magnetic WD binaries,
in particular quiescent dwarf novae, provide a major contribution to the
diffuse hard X-ray emission of the Galactic bulge. From the other side,
previous high energy (E$>10$ keV) X-ray measurements of the bulge and ridge
imply a dominant population of magnetic CVs, in particular intermediate polars.
In this work we use side aperture of the NuSTAR to probe the diffuse continuum
of the inner $sim1-3^{circ}$ of the Galactic bulge, which allows us to
constrain possible mixture of soft and hard populations components of the
spectrum. We found that GDXE spectrum is well-described by a single-temperature
thermal plasma with $kT approx 8$ keV, which supports that the bulge is
dominated by quiescent dwarf novae with no evidence of a significant
intermediate polar population in the hard X-ray band. We also compare this
result with previous NuSTAR measurements of the inner 10 pc and inner 100 pc of
the Galactic center.
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