English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We present results from the analysis of deep ROSAT HRI and PSPC observationsof the spiral galaxy M81. The inferred total (0.5-2 keV band) luminosity of M81is ~3x10^40 ergs/s, excluding the contribution from identified interlopersfound within the D_25 ellipse. The nucleus of the galaxy alone accounts forabout 65% of this luminosity. The rest is due to 26 other X-ray sources(contributing ~10%) and to apparently diffuse emission, which is seen acrossmuch of the galactic disk and is particularly bright in the bulge region aroundthe nucleus. Spectral analysis further gives evidence for a soft component,which can be characterized by a two-temperature optically thin plasma withtemperature at ~0.15 keV and 0.60 keV and an absorption of the Galacticforeground only. These components, accounting for ~13% of the X-ray emissionfrom the region, apparently arise in a combination of hot gas and faintdiscrete sources. We find interesting spatial coincidences of luminous(10^37-10^40 ergs/s) and variable X-ray sources with shock-heated opticalnebulae. Three of them are previously classified as supernova remnantcandidates. The other one is far off the main body of M81, but is apparentlyassociated with a dense HI concentration produced most likely by the tidalinteractions of the galaxy with its companions. These associations suggest thatsuch optical nebulae may be powered by outflows from luminous X-ray binaries,which are comparable to, or more luminous than Galactic `micro-quasars'.Comment: 15 pages, 8 tables, 9 figures, accepted for publication in the  Astrophysical Journa

ROSATX‐Ray Observations of the Spiral Galaxy M81