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 Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

This paper reports the discovery of a bright X-ray transient source, SuzakuJ1305-4913, in the south-west arm of the nearby Seyfert II galaxy NGC 4945. Itwas detected at a 0.5 -- 10 keV flux of $2.2 \times 10^{-12}$ erg cm$^{-2}$s$^{-1}$ during the Suzaku observation conducted on 2006 January 15 -- 17, butwas undetectable in a shorter observation on 2005 August 22 --23, with an upperlimit of $1.7 \times 10^{-14}$ erg cm$^{-2}$ s$^{-1}$ (90% confidence level).At a distance of 3.7 Mpc, the bolometric luminosity of the source becomes$L_{\rm bol} = 4.4 \times 10^{39} \alpha$ erg s$^{-1}$, where $\alpha = (\cos60^\circ / \cos i)$ and $i$ is the disk inclination. Therefore, the source isclassified into so-called ultraluminous X-ray sources (ULXs). The time-averagedX-ray spectrum of the source is described by a multi-color disk model, with theinnermost accretion disk temperature of $T_{\rm in} = 1.69_{-0.05}^{+0.06}$keV. During the 2006 January observation, it varied by a factor of 2 inintensity, following a clear correlation of $L_{\rm bol} \propto T_{\rm in}^4$.It is inferred that the innermost disk radius $R_{\rm in}$ stayed constant at$R_{\rm in} = 79_{-3.9}^{+4.0} \alpha^{1/2}$ km, suggesting the presence of astandard accretion disk. Relating $R_{\rm in}$ with the last stable orbitaround a non-rotating black hole yields a rather low black hole mass, $\sim 9\alpha^{1/2}$ solar masses, which would imply that the source is shining at aluminosity of $\sim3 \alpha^{1/2} $ times the Eddington limit. These resultscan be better interpreted by invoking sub-Eddington emission from a rapidlyspinning black hole with a mass of 20 -- 130 solar masses.

Discovery of a bright transient ultraluminous X-ray source Suzaku J1305-4931 in NGC 4945