An Analysis of the North Polar Spur Using HaloSat
Open accessAbstract
We present HaloSat X-ray observations of the entirety of the bright X-ray emitting feature known as the North Polar Spur (NPS). The large field of view of HaloSat enabled coverage of the entire bright NPS in only 14 fields, which were each observed for ≈30,000 s. We find that the NPS fields are distinct in both brightness and spectral shape from the surrounding halo fields. We fit the NPS as two thermal components in ionization equilibrium with temperatures and . We note a temperature gradient in the NPS hot component with an inner arc temperature warmer than the outer arc. The emission measures we find for the cool component of the NPS is a factor of 3–5 greater than that of the hot component, which suggests that the bulk of the NPS material is in the ≈0.1 keV component. We evaluate distance estimates of 0.4 and 8.0 kpc for the NPS. Our findings suggest a preference for a distant NPS with an energy of ≈ 6 × 10 54 erg, an age of ≈ 10 Myr, and pressures consistent with a 10 μ G magnetic field associated with the Fermi bubbles. The electron density ≈10 × 10−3 cm−3 is consistent with estimates for the shock region surrounding a Galactic-scale event.
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- Authors
- LaRocca, D. M., Kaaret, P., Kuntz, K. D., Hodges-Kluck, E., Zajczyk, A., Bluem, J., Ringuette, R., & Jahoda, K. M.
- Affiliations
- University of Iowa (US)
- Goddard Space Flight Center (US)
- Corresponding author
- LaRocca, Daniel M.
- ORCID
- Venue
- The Astrophysical Journal
- Publisher
- American Astronomical Society
- Published
- 2020-11-01
- Volume
- 904
- Issue
- 1
- Pages
- 54
- ISSN
- 0004-637X (ISSN-L)
- 1538-4357
- OpenAlex
- W3109548852
- Cited by
- 26
- References
- 35
- Citations by year
- 2025: 1 · 2024: 7 · 2023: 4 · 2022: 6 · 2021: 7 · 2020: 1
- FWCI
- 1.99
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Licence
- Locations
- The Astrophysical Journal (publishedVersion)
- Maryland Shared Open Access Repository (USMAI Consortium) (submittedVersion, public-domain)
- Digital Repository at the University of Maryland (University of Maryland College Park) (public-domain)
- Funders
- NASA (NNX15AU57G)
- Iowa Space Grant Consortium (NNX16AL88H)
- Topics
- Physical Sciences › Physics and Astronomy › Nuclear and High Energy Physics › Astrophysics and Cosmic Phenomena
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysical Phenomena and Observations
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Gamma-ray bursts and supernovae
- Keywords
- North Polar Spur, X-ray emission, thermal plasma, ionization equilibrium, temperature gradient, emission measure, distance estimates, Fermi bubbles, magnetic field, Galactic halo
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