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 report the first results of the Chandra temporal monitoring of theultra-luminous X-ray sources (ULXs) in the Antennae galaxies (NGC 4038/39).Observations at four different epochs, covering time scales of 2 years to 2months, show variability in seven out of nine ULXs, confirming that they arelikely to be accreting compact X-ray binaries (XRBs). The seven variable ULXsexhibit a variety of temporal and spectral behaviors: one has harder X-raycolors with decreasing luminosity, similar to the black hole binary Cyg X-1,but four other ULXs show the opposite behavior. We suggest that the latter maybe black-hole binaries accreting at very high rates.Comment: 3 pages, 3 figures, 1 table In press in Ap. J. Letter

The Time-variable Ultraluminous X-Ray Sources of “The Antennae”