Spitzer Space Telescope - General Observer Proposal #20408


Dust processing in the protoplanetary disks of the Orion OB1
Association

Principal Investigator: Nuria Calvet
           Institution: University of Michigan

Co-Investigators: 
Cesar Briceno, Centro de Investigaciones de Astronomia (CIDA)         
James Muzerolle, Steward Observatory                                  
Lee Hartmann, Smithsonian Astrophysical Observatory                   
Paola D'Alessio, Instituto de Astronomia UNAM - Morelia               
Edwin Bergin, Department of Astronomy, University of Michigan         

Science Category: circumstellar/debris disks 
 Observing Modes: IrsStare 
  Hours Approved: 2.1 

Abstract:
We propose to obtain mid-IR spectra using IRS on board Spitzer of four
~5 Myr old stars in the Orion OB1b association, which show indications
of an advanced degree of dust evolution in their disks, and for which
the ground-based observations suggest they are in the critical phase
just prior to the opening of gaps in their disks.  Our ongoing
large-scale survey of the Orion OB1 star-forming region has allowed us
to secure the ground-based photometric and spectroscopic data needed
to fully characterize the stellar and accretion properties of these
objects, including the mass accretion rates in their inner disks.
Combined with the Spitzer IRS data and our theoretical analysis, we
will be able to shed light on the state of solids in disks in which
protoplanets may already be forming and starting to open gaps.  Our
analysis will include assesing the distribution of dust and its
mineralogy.  We have also requested time with HST to obtain far-UV
spectra of these objects.  These spectra, if the time is granted, will
provide crucial information on the gas in the inner disk, which
together with the Spitzer mid-IR data will allow us to build a
comprehensive view, and gain unprecedented insight into the physical
processes characterizing the evolution of gas and dust in inner
circumstellar disks.