Toloza Castillo, Odette Fabiola

2019-04-05, Manser, Christopher J., Gänsicke, Boris T., Eggl, Siegfried, Hollands, Mark, Izquierdo, Paula, Koester, Detlev, Landstreet, John D., Lyra, Wladimir, Marsh, Thomas R., Meru, Farzana, Mustill, Alexander J., Rodríguez-Gil, Pablo, Toloza, Odette, Veras, Dimitri, Wilson, David J., Burleigh, Matthew R., Davies, Melvyn B., Farihi, Jay, Fusillo, Nicola Gentile, de Martino, Domitilla, Parsons, Steven G., Quirrenbach, Andreas, Raddi, Roberto, Reffert, Sabine, Santo, Melania Del, Schreiber, Matthias R., Silvotti, Roberto, Toonen, Silvia, Villaver, Eva, Wyatt, Mark, Xu, Siyi, Zwart, Simon Portegies

A low-mass planet around a white dwarf Numerous exoplanets have been detected around Sun-like stars. These stars end their lives as white dwarfs, which should inherit any surviving planetary systems. Manser et al. found periodic shifts in emission lines from a disc of gas orbiting around a white dwarf (see the Perspective by Fossati). They used numerical simulations to show that the most likely explanation for the spectral shifts is a low-mass planet orbiting within the disc. The planet must be unusually small and dense to avoid being ripped apart by tidal forces. The authors speculate that it may be the leftover core of a planet whose outer layers have been removed. Science , this issue p. 66 ; see also p. 25

2024-03-01, Hernandez, Mercedes S., Schreiber, Matthias R., Landstreet, John D., Bagnulo, Stefano, Parsons, Steven G., Chavarria, Martin, Toloza, Odette, Bell, Keaton J.

Recent surveys of close white dwarf binaries as well as single white dwarfs have provided evidence for the late appearance of magnetic fields in white dwarfs, and a possible generation mechanism, a crystallization and rotation-driven dynamo has been suggested. A key prediction of this dynamo is that magnetic white dwarfs rotate, at least on average, faster than their non-magnetic counterparts and/or that the magnetic field strength increases with rotation. Here we present rotation periods of ten white dwarfs within 40 pc measured using photometric variations. Eight of the light curves come from TESS observations and are thus not biased towards short periods, in contrast to most period estimates that have been reported previously in the literature. These TESS spin periods are indeed systematically shorter than those of non-magnetic white dwarfs. This means that the crystallization and rotation-driven dynamo could be responsible for a fraction of the magnetic fields in white dwarfs. However, the full sample of magnetic white dwarfs also contains slowly rotating strongly magnetic white dwarfs which indicates that another mechanism that leads to the late appearance of magnetic white dwarfs might be at work, either in addition to or instead of the dynamo. The fast-spinning and massive magnetic white dwarfs that appear in the literature form a small fraction of magnetic white dwarfs, and probably result from a channel related to white dwarf mergers.