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 present the detection of a variable star with an $18.05$ minute period infar-ultraviolet (FUV) images of the globular cluster NGC 1851 taken with theHubble Space Telescope (HST). A candidate optical counterpart lies on the redhorizontal branch or the asymptotic giant branch star of the cluster, but it isstatistically possible that this is a chance superposition. This interpretationis supported by optical spectroscopt obtained with HST/STIS: the spectrumcontains none of the strong emission lines that would be expected if the objectwas a symbiotic star (i.e. a compact accretor fed by a giant donor). Wetherefore consider two other possibilities for the nature of FUV variable: (i)an intermediate polar (i.e. a compact binary containing an accreting magneticwhite dwarf), or (ii) an AM CVn star (i.e. an interacting double-degeneratesystem). In the intermediate polar scenario, the object is expected to be anX-ray source. However, no X-rays are detected at its location in $\simeq65$~ksec of {\em Chandra} imaging, which limits the X-ray luminosity to $L_X\leqslant 10^{32}$~erg~s$^{-1}$. We therefore favour the AM CVn interpretation,but a FUV spectrum is needed to distinguish conclusively between the twopossibilities. If the object is an AM CVn binary, it would be the first suchsystem known in any globular cluster.

A far-ultraviolet variable with an 18-minute period in the globular cluster NGC 1851