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

Searches for magnetic fields in white dwarfs have clarified both thefrequency of occurrence and the global structure of the fields found down tofield strengths of the order of 500 kG. Below this level, the situation isstill very unclear. We are studying the weakest fields found in white dwarfs todetermine the frequency of such fields and their structure. We describe a verysensitive new method of measuring such fields in DA (H-rich) white dwarfs, andsearch for a field in the brightest such star, 40 Eri B. Our new method makesuse of the strongly enhanced polarisation signal in the sharp core of Halpha.We find that with one-hour integrations with the high-resolutionspectropolarimeter ESPaDOnS on the 3.6-m CFHT, we can reach a standard error fothe longitudinal field of about 85 G, the smallest error ever achieved for anywhite dwarf. Nevertheless, we do not detect a magnetic field in this star.Observations with ISIS at the WHT, and the Main Stellar Spectrograph at theSAO, support the absence of a field at somewhat lower precision. The new methodis very efficient; it is shown that for suitable DA stars the integration time,with ESPaDOnS on a 3.6-m telescope, to reach a 500 G standard error on a whitedwarf of V = 12.5, is about half an hour, about the same as the time requiredon an ESO 8-m telescope with FORS using conventional low-resolutionspectropolarimetry.

A novel and sensitive method for measuring very weak magnetic fields of DA white dwarfs: A search for a magnetic field at the 250 G level in 40 Eri B