Caltech/IPAC Lunch Seminar

Red dwarfs are favored hosts for exoplanet searches, but the particle and radiation environments their planets inhabit are observationally difficult to probe.  A new handle on the problem has emerged from precise space-based photometry: a small fraction of young red dwarfs show complex periodic variability in their optical light curves, with key early contributions from locals including Rebull, Stauffer, van Eyken, Ciardi, Christiansen, and Hillenbrand.  New observations show that the phenomenon is driven by magnetically confined clumps of ~1500 K dust and ~10⁴ K plasma, persisting for months to years in million-K coronae.  These systems demonstrate that circumstellar plasma number densities can be measured directly, and suggest that the underlying stellar magnetic field topologies are more complex than simple dipoles.  The dust's origin remains open.  Continued data from Roman, JWST, Gaia, and TESS will sharpen the inferences and open new questions.