A plague of magnetic spots among the hot stars of globular clusters

Y. Momany, S. Zaggia, M. Montalto, D. Jones, H. M.J. Boffin, S. Cassisi, C. Moni Bidin, M. Gullieuszik, I. Saviane, L. Monaco, E. Mason, L. Girardi, V. D’Orazi, G. Piotto, A. P. Milone, H. Lala, P. B. Stetson, Y. Beletsky

Resultado de la investigación: Contribución a una revistaArtículo

Resumen

For more than six decades, the quest to understand the formation of hot (about 20,000−30,000 K) extreme horizontal branch (EHB) stars in Galactic globular clusters has remained one of the most elusive in stellar evolutionary theory. Here we report on two discoveries that challenge the idea of the stable luminosity of EHB stars. The first mode of EHB variability is periodic and cannot be ascribed to either binary evolution or pulsation. Instead, we attribute it here to the presence of magnetic spots: superficial chemical inhomogeneities whose projected rotation induces the variability. The second mode of EHB variability is aperiodic and manifests itself on timescales of years. In two cases, six-year-long light curves display superflare events that are several million times more energetic than solar analogues. We advocate a scenario in which the two EHB variability phenomena are different manifestations of diffuse, dynamo-generated, weak magnetic fields. Magnetism is therefore a key player driving the formation and evolution of EHB clusters stars and, likewise, operating in the Galactic field counterparts. Our conclusions bridge similar variability/magnetism phenomena in all radiative-enveloped hot-stars: young main-sequence stars, old EHBs and defunct white dwarfs.

Idioma originalInglés
PublicaciónNature Astronomy
DOI
EstadoEn prensa - 1 ene 2020

Áreas temáticas de ASJC Scopus

  • Astronomía y astrofísica

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    Momany, Y., Zaggia, S., Montalto, M., Jones, D., Boffin, H. M. J., Cassisi, S., Moni Bidin, C., Gullieuszik, M., Saviane, I., Monaco, L., Mason, E., Girardi, L., D’Orazi, V., Piotto, G., Milone, A. P., Lala, H., Stetson, P. B., & Beletsky, Y. (Aceptado/En prensa). A plague of magnetic spots among the hot stars of globular clusters. Nature Astronomy. https://doi.org/10.1038/s41550-020-1113-4