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Identifying neutron stars in Galactic Bulge with X-ray data

Presentation #107.32 in the session Stellar/Compact Objects - Poster Session.

Published onMay 03, 2024
Identifying neutron stars in Galactic Bulge with X-ray data

Fermi observations of the inner degree of the Milky Way Galaxy show an excess of gamma-rays in addition to the expected emission from cosmic ray interactions. This gamma-ray excess (GCE) could be from dark-matter annihilation or an underlying population of millisecond pulsars (MSPs). X-ray observations from XMM-Newton and Chandra, which have higher angular resolution than Fermi, can detect the X-ray emission from bright MSPs and constrain the fraction of GCE that could be explained from MSPs. However, the Galactic Bulge also contains a population of bright intermediate polars and X-ray binaries that emit X-rays. We use deep (> 100 ks) XMM-Newton observations of the Galactic Bulge to study 838 sources with NH,Gal > 5×1022 cm-2. We compare the (6.2–7.2) keV emission with the surrounding (5.8–6.2) keV and (7.2–7.6) keV emission to distinguish continuum sources from sources that show significant 6.4 keV fluorescence Fe emission (such as X-ray binaries and active galactic nuclei) or Fe-K emission at 6.7 and 7.0 keV (such as cataclysmic variables). The high diffuse background emission allows us to use this methodology only on sources with more than 100 counts. Using this approach, we select 32 sources which show emission consistent with a continuum source. Further spectral analysis shows that 11 of these sources do not show evidence of any Fe lines. One source, 4XMM J174501.0-291045, has an extended radio counterpart and could be a possible young neutron star with a pulsar wind nebula. Follow-up observations, especially in high-frequency radio wavelengths, will allow us to reveal the nature of these sources.

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