9933(  1) - 04/04/03 10:22  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      9933
                                                       Version: 1
                                                       Check-in Date: 04-Apr-2003
                                                                      10:22:36

1.Proposal Title:
Accretion Shocks in Classical T-Tauri Stars
------------------------------------------------------------------------------------
2. Proposal For  3. Cycle
AR               11
------------------------------------------------------------------------------------
4. Investigators
                                                                                     Contact?
    PI: Christopher Johns-Krull           Rice University
   CoI: Dr. David Ardila                  Johns Hopkins University                      N

------------------------------------------------------------------------------------
5. Abstract

We will develop a model of the accretion shock region of Classical T-Tauri stars.
The goal of the model is to relate the observed strong ultraviolet emission in
transition region lines (the SiIV resonance doublets, the CIV resonance doublets,
etc) seen with HST-GHRS and HST-STIS to the physical parameters that control the
accretion process (accretion rate, size of accretion region, topology of magnetic
field, etc.) Current analysis of the transition region lines (which are important
components of HST UV spectral observations of Classical T-Tauris) is limited by the
lack of complete published models. The accretion shock region is composed of a post-
shock region, and a ionized precursor, or pre-shock. Modeling of the former will
take into account that the emiting gas is not in ionization equilibrium, and that
its emission affects the pre-shock, which in turn determines the initial conditions
of the post-shock. The pre-shock will be modeled with a photoionization code.
------------------------------------------------------------------------------------
                                                9933(  1) - 04/04/03 10:22  - [  2]

            Summary Form for Proposal  9933

  Item                         Used in this proposal
------------------------------------------------------------------------------------------------------------------------------------
  Proposal Category            AR
------------------------------------------------------------------------------------------------------------------------------------