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

Detection of paired kilohertz quasi-periodic oscillations (kHz QPOs) in theX-ray emission of a compact object is compelling evidence that the object is anaccreting neutron star. In many neutron stars, the stellar spin rate is equalor roughly equal to Delta-nu, the frequency separation of the QPO pair, or to2Delta-nu. Hence, if the mechanism that produces the kilohertz QPOs is similarin all stars, measurement of Delta-nu can provide an estimate of the star'sspin rate. The involvement of the stellar spin in producing Delta-nu indicatesthat the magnetic fields of these stars are dynamically important.  We focus here on the implications of the paired kHz QPOs recently discoveredin the low-mass X-ray binary (LMXB) system Cir X-1 (Boutloukos et al. 2006).The kHz QPOs discovered in Cir X-1 are generally similar to those seen in otherstars, establishing that the compact object in the Cir X-1 system is a neutronstar. However, the frequency nu-u of its upper kHz QPO is up to a factor ofthree smaller than is typical, and Delta-nu varies by about a factor 2 (167 Hz,the largest variation so far observed). Periodic oscillations have not yet beendetected from Cir X-1, so its spin rate has not yet been measured directly. Thelow values of nu-u and the large variation of Delta-nu challenge current modelsof the generation of kHz QPOs. Improving our understanding of Cir X-1 willimprove our knowledge of the spin rates and magnetic fields of all neutronstars.

Implications of kHz QPOs for the spin frequencies and magnetic fields of neutron stars: new results from Circinus X-1