Abstract
Sinusoidal variations in the magnitude of EV Lac outside of flares are interpreted as due to intensity modulations from a photospheric spot group. No variations are detected in the color indices. An upper limit set by observational uncertainties indicates that the temperature difference between the photosphere and the spot region is only a few hundred degrees. The period of the cyclic magnitude variations is determined for the first time for EV Lac, and my best estimate is P=4.378 days. This implies an equatorial rotational velocity of 4.2 +- 0.5 km s/sup -1/. The equivalent width of the H..beta.. emission line does not vary, as measured through a set of interference filters. A larger scatter is evident in the measurements of the H..cap alpha.. emission, however, but the variations in this line do not correlate clearly with the rotation of EV Lac. The variation in the equivalent width of the H..cap alpha.. line is about one hundred percent. We are led to the conclusion that the prominent emission seen in the H..cap alpha.. line is formed partly in the chromosphere of EV Lac and partly in flare-associated regions of the atmosphere, and with a possible contribution also from analogs to solarmore » plage areas.« less
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
