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

Our Galaxy harbours a large population of X-ray sources of intermediate tolow X-ray luminosity (typically Lx from 10^27 to 10^34 erg/s). At energiesbelow 2 keV, active coronae completely dominate the X-ray landscape. However,the nature and the properties of Galactic sources detected at energies > 2 keVis much less constrained. Optical follow-up spectroscopic observations showthat in addition to cataclysmic variables (CVs) and very active stellarcoronae, massive stars (colliding wind binaries, quiescent high-mass X-raybinaries and Gamma-Cas analogs) account for a sizable fraction of the Galactichard X-ray sources at medium flux (Fx > 10^-13 erg/s/cm^2). Cross-correlationsof the 2XMM-DR3 catalogue with 2MASS and GLIMPSE confirm the presence above 2keV of a large population of coronally active binaries, probably of the BY Draand RS CVn types, in addition to many distant and absorbed massive stars. Wealso report the results of a specific optical identification campaign aimed atstudying the nature of the optically faint hard X-ray sources and atconstraining the surface density of black holes (BHs), either isolated andaccreting from the interstellar medium or in quiescent binaries. Notastonishingly, most of our sample of 14 optically faint and X-ray hard sourcesare identified with CVs and Me stars. We do not find any likely counterpart inonly three cases. Our observations also allow us to put an upper limit of 0.2BH deg^-2 at Fx = 1.3 10^-13 erg/s/cm^2 in directions toward the center of ourGalaxy. This implies a combined Bondi-Hoyle and mass accretion rate to Lxefficiency of accretion onto black holes of less than 10^-3.

Multi-frequency Studies of Galactic X-ray Sources Populations. Hard  X-ray Galactic sources of low to intermediate Lx; A search for isolated  accreting black holes