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تسجيل مستخدم جديدEvidence for intermediate polars as the origin of the Galactic Center hard X-ray emission
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Recently, unresolved hard (20-40 keV) X-ray emission has been discovered within the central 10 pc of the Galaxy, possibly indicating a large population of intermediate polars (IPs). Chandra and XMM-Newton measurements in the surrounding ~50 pc imply a much lighter population of IPs with $langle M_{rm WD} rangle approx 0.5 M_odot$. Here we use broad-band NuSTAR observations of two IPs: TV Columbae, which has a fairly typical but widely varying reported mass of $M_{rm WD} approx 0.5-1.0 M_odot$, and IGR J17303-0601, with a heavy reported mass of $M_{rm WD} approx 1.0-1.2 M_odot$. We investigate how varying spectral models and observed energy ranges influence estimated white dwarf mass. Observations of the inner 10 pc can be accounted for by IPs with $langle M_{rm WD} rangle approx 0.9 M_odot$, consistent with that of the CV population in general, and the X-ray observed field IPs in particular. The lower mass derived by Chandra and XMM-Newton appears to be an artifact of narrow energy band fitting. To explain the (unresolved) CHXE by IPs requires an X-ray (2-8 keV) luminosity function (XLF) extending down to at least $5times10^{31}$ erg/s. The CHXE XLF, if extended to the surrounding ~50 pc observed by Chandra and XMM-Newton, requires at least ~20-40% of the $sim$9000 point sources are IPs. If the XLF extends just a factor of a few lower in luminosity, then the vast majority of these sources are IPs. This is in contrast to recent observations of the Galactic ridge, where the bulk of the 2-8 keV emission is ascribed to dwarf novae.
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The hardness of the X-ray spectra of intermediate polars (IPs) is determined mainly by the white dwarf (WD) compactness (mass-radius ratio, M/R) and, thus, hard X-ray spectra can be used to constrain the WD mass. An accurate mass estimate requires th
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We analyse new results of Chandra and Suzaku which found a flux of hard X-ray emission from the compact region around Sgr A$^ast$ (r ~ 100 pc). We suppose that this emission is generated by accretion processes onto the central supermassive blackhole
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The Galactic Center X-ray Emission (GCXE) is composed of high temperature (7 keV) and low temperature (1 keV) plasmas (HTP and LTP, respectively). The global structure of the HTP is roughly uniform over the Galactic center (GC) region, and the origin
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