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

The accretion flow / jet correlation in neutron star (NS) low-mass X-raybinaries (LMXBs) is far less understood when compared to black hole (BH) LMXBs.In this paper we will present the results of a dense multi-wavelengthobservational campaign on the NS LMXB 4U 1820-30, including X-ray (Nicer,NuSTAR and AstroSAT) and quasi-simultaneous radio (ATCA) observations in 2022.4U 1820-30 shows a peculiar 170 day super-orbital accretion modulation, duringwhich the system evolves between "modes" of high and low X-ray flux. During ourmonitoring, the source did not show any transition to a full hard state. X-rayspectra were well described using a disc blackbody, a Comptonisation spectrumalong with a Fe K emission line at 6.6 keV. Our results show that the observedX-ray flux modulation is almost entirely produced by changes in the size of theregion providing seed photons for the Comptonisation spectrum. This region islarge (about 15 km) in the high mode and likely coincides with the wholeboundary layer, while it shrinks significantly (<10 km) in low mode. Theelectron temperature of the corona and the observed RMS variability in the hardX-rays also exhibit a slight increase in low mode. As the source moves fromhigh to low mode, the radio emission due to the jet becomes about 5 fainter.These radio changes appear not to be strongly connected to the hard-to-softtransitions as in BH systems, while they seem to be connected mostly tovariations observed in the boundary layer.

The accretion/ejection link in the neutron star X-ray binary 4U 1820-30 I: A boundary layer-jet coupling?