Projects to be developed with the SOAR facilities: 1) PRE MAIN SEQUENCE STARS: UV - IR Pre Main Sequence Stars (PMS) are still surrounded by the primordial gas that formed them. In a large fraction of these stars, this primordial gas has collapsed down to disk-like structures. The presence of these circumstellar disks are thought to be directly responsible for very large amplitude light variations (> 0.6 mag), mass Loss, broad and narrow line emissions and excess luminosity in the optical and IR compared to Main Sequence stars of the same spectral type. In particular, accretion disks are self luminous in the near infrared, generating the large fraction of continuum flux that has been collected in the J,H,K,L bands. Excess radiation in low mass PMS is also particularly conspicuous in the UV, being sometimes observed in the optical range in cases where heavily accretion rates are taking place. Optical and UV luminous excess is thought to originate in regions of shock where the circumstellar gas meets the stellar photosphere. The advent of SOAR will facilitate the following projects: 1.1) UV-optical and Near Infrared continuum observation. Such data will verify if current models of PMS stars well represent the accretion flow in the regions close to the star. The simultaneity of near IR and UV data, including the Balmer jump, will provide clues concerning the disk flow, including those characterized by low (< 2000K) and high (> 8000K) temperature gas. 1.2) Veiling Determinations of TTS in the Cha and Lupus complexes. If quasi-simultaneous photometry or spectrophotometry with high resolution spectroscopy is available, it will be possible to access the stellar and circumstellar luminosities with a high degree of accuracy. The spectral data corrected for veiling can yield metallicities and real chromospheric luminosities - measurements yet to be made for TTS with high levels of disk accretion. 1.3) Study of the disk atmosphere using molecular bands in the near IR. It is thought that the stellar magnetosphere halts the accretion disk at the corotational annulus, driving the gas down to high latitude regions. Disk atmospheres with temperature and density scales suitable for molecular formation then arise. Studying the variability of these bands and correlating them with the fluctuations found in other spectral features (such as forbidden lines, Halpha, CaII broad lines, etc...) will shed more light on the reality of accretion and the stellar magnetosphere as the mechanism controlling the fluctuation of all these spectral features. This study goes in parallel with a project devoted to analyze the variability of selected spectral features found in broad line emission of PMS star (synoptic observations). 1.4) Spectral Imaging of forbidden lines will scan the regions surrounding PMS in [OI] or [SII] to ascertain bipolar jets and/or the morphology in general of the circumstellar region. ----------------------------------------- 2) The following projects involve the direct observation of the circumstellar environment. 2.1) Direct Imaging of PMS circumstellar disks. Hubble telescope has provided several images of disk-like circumstellar material. We intend to pursue this same project using the SOAR instruments. 2.2) Determination of Jupiter-like planets in nearby field stars. The project will select molecular bands in the NIR that are typically observed in Jupiter and search for them in the surroundings of nearby stars. These features will be selected after observing Jupiter with the IR camera that is being presently developed at LNA. This project is a joint collaboration with Daniela Lazzaro, and we are in the process of selecting possible molecular bands, candidate star systems etc. The advantages of this project in comparison with those using radial velocity modulations are the complete independence from stellar activity (which widen the number of candidates) and the use of less observing time per candidate. 2.3) Search for low mass companions in binary systems. The coronagraphic system will allow for the following projects: 2.3.1) Searches for secondary T Tauri stars in Lupus and Cha complexes. 2.3.2) Searches for brown dwarfs as companions to M stars. 2.3.3) Searches for T Tauri Stars as companions to O-B stars. Such systems allow us to compute accurate ages of the TTS since we can draw from the evolutionary models of main sequence stars which are much more reliable than those of pre-main sequence stars. The difficulty arises in observing the TTS which is orders of magnitude fainter than its main sequence companion. The dynamic range of typical CCD's makes this a very difficult task. Blocking out the light of the O-B star, however, using the coronagraph, would make this possible. The result would be light curves and spectroscopic data of T Tauri Stars with well determined ages. -------------------------------------- There are several important projects on stellar activity which can be developed with the instruments of SOAR. I list two: 3.1) Study the infrared excess observed in dMe stars relative to inactive M stars. This will require high resolution (R>50000) spectral observations in the IR to infer the properties of the gas where this continuum is being formed. This, in turn, is related to the number of flare events which partially drives mass-loss in main sequence stars. The details of this connection, however, are poorly understood. 3.2) Study of Spots in Late Type Stars. Quasi simultaneous access to photometry and high resolution spectroscopy will provide a unique setup ideally suited to Doppler Imaging analyses of late-type stars. Current work in this field has been largely limited to only the brightest of the young late-type stars. Natalie Marie Stout and I are presently selecting the targets which will include stars with accretion disks.