PROPOSALS FOR THE SOAR TELESCOPE

Programme 1. ROTATION, ACTIVITY AND NUCLEOSSYNTHESIS
                       IN EVOLVED STARS OF OPEN CLUSTERS

                            J. R. De Medeiros and J. C. Carvalho
 
                            Departamento de Fisica Teorica e 
Experimental
                            Universidade Federal do Rio Grande do Norte
                            Campus Universitario
                            59072-970, Natal, R.N., Brasil


The behavior of rotation as a fuction of luminosity and effective 
temperatures can provide important constraints for models of angular 
momentum as stars evolve through the HR diagram, as well as important 
information on the presence of external rotational brakes, tidal 
interactions acoustic heating in binary systems, the dilution of light 
elements in stellar interiors and non-thermal heating in stellar 
atmospheres. Up to date, one knows just the behavior of rotation in 
field evolved stars. J. R.  De Medeiros and Collaborators have published 
some 10 papers concerning this matter. It is of major importance to 
study the rotation of evolved stars in open clusters, as well as the 
link between such parameter and the indicators of activity and chemical 
abundances, because such stars offer additional constraints like age and 
mass which are not possible to determine for field stars. The main goal 
of the present project is the determination of rotational velocity, 
chromospheric emission flux and chemical !
 abundances in evolved stars of luminosity classes Ia, Ib, II, III and 
IV in open clusters, from the observation of absorption and emission 
line profiles.

Instrumental requirements:

- High-resolution Echelle Spectrograph;
- adaptative optics;
- multi-objects observation tools;
- Signal-to-Noise higher than 200;
- Spectral range: 3000-6000A;
- Spectral resolution better than 50,000;
- Typical exposure time: 60 to 120 minutes;
- moonlight: grey time to dark time.



Programme 2. MEASUREMENT OF THE COSMIC MICROWAVE BACKGROUND
                       RADIATION TEMPERATURE AT HIGH REDSHFTS.

                           J. A. S. Lima and J. R. De Medeiros
  
                           Departamento de Fisica Teorica e Experimental
                            Universidade Federal do Rio Grande do Norte
                            Campus Universitario
                            59072-970, Natal, R.N., Brasil

We intend to determine the temperature of the cosmic microwave 
background radiation by observing the excitation of atomic transitions 
in absorption clouds along the line-of-sight of quasars at high 
redshifts. As predicted by Lima (Phys. Rev. D, 1996, 54, 2571), the 
temperature of the CMBR for a model with adiabatic photon creation 
satisfies the relation
                             T = To (1+z) ( N(t)/No)**1/3,

where To = 2.7 K is the present value of  T,  No and N(t) are 
respectively the number of photons today and at time t(z). This equation 
means that universes with photon creation are, for any value of z larger 
than 0, cooler than the standard model. In particular, in the minimal 
model, the above equation reduces to

                                    T = To (1+z)**(1-B),

where the B parameter varies on 0<B<1.

 

Programme 3.  THE DETERMINATION OF PRIMORDIAL ABUNDANCES  
                            OF LIGHT ELEMENTS

                           J. A. S. Lima and J. R. De Medeiros
  
                           Departamento de Fisica Teorica e Experimental
                           Universidade Federal do Rio Grande do Norte
                           Campus Universitario
                           59072-970, Natal, R.N., Brasil


We intend to determine the abundance of light elements, outside the 
Galaxy,  by studying the absorption spectra of high redshift quasars. 
Such abundance can be used as a sensitive test of the standard Big-Bang 
cosmologie as well as a test for the new alternative theories.


Instrumental requirements:

- High-resolution Echelle Spectrograph;
- Signal-to-Noise higher than 100;
- Spectral range: 3000-6000A;
- Spectral resolution better than 50,000;
- Typical exposure time: 90 to 120 minutes (for a quasar of mv=16)
- moonlight: dark time.