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

{\it Chandra} Galactic Center Survey detected $\sim 800$ X-ray point-likesources in the $2^{\circ} \times 0.8^{\circ}$ sky region around the GalacticCenter. In this paper, we study the spatial and luminosity distributions ofthese sources according to their spectral properties. Fourteen bright sourcesdetected are used to fit jointly an absorbed power-law model, from which thepower-law photon index is determined to be $\sim$2.5. Assuming that all othersources have the same power-law form, the relation between hardness ratio andHI column density $N_H$ is used to estimate the $N_H$ values for all sources.Monte Carlo simulations show that these sources are more likely concentrated inthe Galactic center region, rather than distributed throughout the Galacticdisk. We also find that the luminosities of the sources are positivelycorrelated with their HI column densities, i.e. a more luminous source has ahigher HI column density. From this relation, we suggest that the X-rayluminosity comes from the interaction between an isolated old neutron star andinterstellar medium (mainly dense molecular clouds). Using the standard Bondiaccretion theory and the statistical information of molecular clouds in theGalactic center, we confirm this positive correlation and calculate theluminosity range in this scenario, which is consistent with the observation($10^{32}\sim 10^{35}$ ergs s$^{-1}$).Comment: 14 pages, 8 figures, accepted by Chinese Journal of Astronomy &  Astrophysic

A Statistical Analysis of Point-like Sources in the Chandra Galactic Center Survey