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 TESS photometry of the asynchronous polar BY Cam, which undergoesa beat-cycle between the 199.384-min white dwarf (WD) spin period and the201.244-min orbital period. This results in changes in the flow of matter ontothe WD. The TESS light curve covers 92% of the beat cycle once and 71% of thebeat cycle twice. The strongest photometric signal, at 197.560-min, is ascribedto a side-band period. During times of light-curve stability, the photometrymodulates at the spin frequency, supporting our WD spin-period identification.Both one-pole and two-pole accretion configurations repeat from one beat cycleto the next with clear and repeatable beat-phase dependent intensityvariations. To explain these, we propose the operation of a magnetic valve atL1. The magnetic valve modulates the mass-transfer rate, as evidenced by afactor of 5 variation in orbital-averaged intensity, over the course of thebeat cycle in a repeatable manner. The accretion stream threading distance fromthe WD is also modulated at the beat-period, because of the variation of the WDmagnetic field with respect to the stream and because of changes in the masstransfer rate due to the operation of the magnetic valve. Changes in thethreading distance result in significant shifts in the position of accretingspots around the beat cycle. As a consequence, only the faintest photometricminima allow for an accurate ephemeris determination. Three regions on thewhite dwarf appear to receive most of the accretion flow, suggestive of acomplex WD magnetic field.

A magnetic valve at L1 revealed in TESS photometry of the asynchronous polar BY Cam