Temporal Variability of Magnetic Structures on BD +26 730
Abstract
BD +26 730 is perhaps the most magnetically active K dwarf known, a rapidly rotating (P = 1.8 day) flare star with enormous chromospheric and transition-region line emission, highly variable X-ray flux, and large starspots with a known 60 year activity cycle period. Since the star is viewed nearly pole-on, almost all variability will be the result of the evolution of activity in time, rather than rotational modulation. Direct measurement of the magnetic field strength and fractional surface coverage of plages on the star is also possible through the careful analysis of magnetic line broadening. We propose to observe the star, now approaching starspot (and magnetic activity) maximum, with the IUE at multiple phases in order to study the time-variability of the chromospheric and transition-region activity. Simultaneous measurements of photometric colors, linear polarization, and magnetic line broadening will be combined with the IUE data to study the growth and decay of active regions, and explore the connections between photospheric magnetic fields, and the structure and energy balance of the hot, upper-atmospheric layers of the star. Comparison of the UV fluxes with earlier epoch IUE spectra taken near activity minimum will allow us to investigate differences in stellar activity at extremes in the magnetic cycle of the star. Our study will be the first investigation of strictly temporal evolution of magnetic fields and related activity on any star other than the Sun.
- Publication:
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IUE Proposal
- Pub Date:
- 1988
- Bibcode:
- 1988iue..prop.3175S