A Multi-wavelength study of the M dwarf binary YY Geminorum

TL;DR

This multi-wavelength study of the binary YY Geminorum combines optical, UV, X-ray, and radio data to analyze stellar activity, revealing compact radio emission regions, chromospheric saturation, and magnetic flares.

Contribution

It provides a comprehensive multi-wavelength analysis of YY Geminorum, integrating observations across different spectra to understand stellar activity and magnetic phenomena in this binary system.

Findings

Eclipses observed at optical, UV, and radio wavelengths.

Radio emission drops indicate compact emission regions.

Evidence of chromospheric saturation and magnetic flares.

Abstract

We review the results of the 1988 multi-wavelength campaign on the late-type eclipsing binary YY Geminorum. Observations include: broad-band optical and near infra-red photometry, simultaneous optical and ultraviolet (IUE) spectroscopy, X-ray (Ginga) and radio (VLA) data. From models fitted to the optical light curves, fundamental physical parameters have been determined together with evidence for transient maculations (spots) located near quadrature longitudes and intermediate latitudes. Eclipses were observed at optical, ultraviolet and radio wavelengths. Significant drops in 6cm radio emission near the phases of both primary and secondary eclipse indicate relatively compact radio emitting volumes that may lie between the binary components. IUE observations during secondary eclipse are indicative of a uniform chromosphere saturated with MgII plage-type emission and an extended volume of Ly$\alpha$ emission. Profile fitting of high-dispersion H alpha spectra confirms the chromospheric saturation and indicates significant H$\alpha$ opacity to heights of a few percent of the photospheric radius. There is evidence for an enhanced H alpha emission region visible near phase 0.25-0.35 which may be associated with a large spot on the primary and with two small optical flares which were also observed at other wavelengths: one in microwave radiation and the other in X-rays. For both flares, L_X/L_opt is consistent with energy release in closed magnetic structures.