Young Stellar Objects: SU Aurigae

DeWarf and Guinan, with former undergraduate astronomy student J. Sepinsky (currently a graduate student at Northwestern University), continue their study of the nearby Pre-Main Sequence (PMS) star SU Aurigae. PMS stars are known to have a large circumstellar accretion disks. Our photometry of SU Aur with robotic telescopes shows that its brightness varies on time scales of days, months, and years, and the star often displays dramatic ``dips'' ( $\Delta V \lesssim 0.80$ mag) that last for several days. These sudden drops in light are not accompanied by spectral changes (i.e., line blocking effects), which implies obscuration of the star by dusty concentrations. Because SU Aur is viewed at high inclination (nearly ``edge-on''), the source of these obscurations is most likely dust clumps around low mass companions (accreting protoplanets, protocomets, and/or associated halos). The accretion disk of SU Aur is therefore most likely in the process of forming embryonic planets.

They hope to expand the program to obtain FUV spectra with FUSE. These spectra, if approved for observations in 2004, will provide excellent data on the hot plasmas at various temperatures, compositions, dynamics, ionization states, and electron densities in the stellar chromosphere, transition region, and corona, along with the hot inner regions of the circumstellar disk. These observations should greatly improve our understanding of the complex inflow, accretion, and outflow dynamics that occur during this stage of evolution and possibly provide insights into the nature of the ``eclipse-like'' events.

In addition to observing SU Aur, differential photometry of its proper motion companion, AB Aur, is conducted at the same time. AB Aur is observed less frequently per night and shows only small light variations ($\pm0.07$ in u and $\pm0.03$ in y).

This research is supported by NSF/RUI Grant AST-00-71260.