AAS 198th Meeting, June 2001
Session 46. Variable and Binary Stars - Photometry
Display, Tuesday, June 5, 2001, 10:00am-6:30pm, Exhibit Hall

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[46.04] When the Sun was Young: A Multi-frequency Study of the Young Solar Analog HD 129333 (= EK Dra)

J.M. DePasquale, J.J. Bochanski, E.F. Guinan, I. Ribas, G.P. McCook (Villanova University), J.D. Dorren (Edinburgh), M. Guedel (ETHZ)

EK Draconis (HD 129333; V = 7.50 mag; G1 V; B-V = +0.61) is a very young (near ZAMS), single solar type star with a rotational period of P ~2.7 days. The space motions of EK Dra show it to be a probable member of the Pleiades Moving Group implying an age of ~ 70 Myr. Providing a look-back of the Sun shortly after its arrival on the Zero-Age Main Sequence some 4.5 Gyr ago, EK Dra is one of the youngest solar-type stars on our "Sun in Time" Program. Appropriate for its youth and related rapid rotation, EK Dra has very high levels of coronal X-ray and EUV emissions and strong FUV - UV transition-region and UV-NUV chromospheric line emissions. These strong emissions arise from a robust magnetic dynamo.

Optical photometry of EK Dra has been carried out since 1988 using robotic telescopes. The photometry shows large rotationally induced brightness variations (V-Ampl. = 0.05 - 0.09 mag) with periods that range from 2.55d to 2.80d. These light variation have been modeled with dark starspots covering up to 15 percent of the stellar surface. The apparent variation in the observed period is explained by differential latitudinal rotation. The photometry also shows a ~12 year cyclic brightness variations which is remarkably similar to present Sun's ~ 11 year cycle. However, the luminosity variations observed for EK Dra are much larger (~ 8 varies only about 0.2 this paper we discuss the results of the uvby photometry, X-ray, EUV, FUV, UV, and NUV observations of EK Dra. A summary of the properties of the young Sun using EK Dra as a proxy are presented.

This research is supported by the following grants: NSF/RUI Grant 00-71260; NASA/FUSE Grants NAG 5-8986, NAG 5-10387; NASA/EUVE Grant SA2085-26310; which we gratefully acknowledge.

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