Rotation-Induced Radio Variability from the T Tauri Star HDE283572?
Session 40 -- Young Stars and T Tauri Stars
Display presentation, Thursday, January 13, 9:30-6:45, Salons I/II Room (Crystal Gateway)

## [40.05] Rotation-Induced Radio Variability from the T Tauri Star HDE283572?

J.L.Hand (Kansas University), C.J.Lonsdale, R.B.Phillips (MIT Haystack Observatory)

We report the results of a month-long monitoring observation of the Pre-Main Sequence star HDE283572 (G5 IV). The VLA was used to measure total and polarized intensity at $\lambda$20, 6, and 3.6 cm in 34 snapshots in May and June 1993, to investigate possible correlations of nonthermal radio activity with rotational phase.

Previous claims for stellar rotation - radio correlations were in some cases unconvincing because of sparse phase coverage, or because widely separated radio measurements sampled disparate rotation cycles. We chose the target source for our study HDE283572 for attributes favorable to observing putative modulation, such as an inclination nearly equator-on and a rotation period (1.55 days) that is a non-integral number of terrestrial days, so that observations repeated at the same LST would slew in stellar rotation phase. Observation dates were requested to sample several consecutive rotations periods, in the event radio activity arose in persistent regions anchored in stellar longitude.

Our results suggest that elevated levels of radio emission are absent from one hemisphere of the star, but rigorous statistical tests are in progress. Independently of the search for rotational effects in the radio emission, the observations provide a rich data base of nonthermal radio spectra vs. time and activity level for this rapidly-rotating, newly convective PMS star.