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28 April 2003

HUBBLE SPACE TELESCOPE

DAILY REPORT #3350

PERIOD COVERED: DOY 115-117

Part 4 of 5

STIS 9431

Composition and history of Beta Pictoris- like circumstellar gaseous
disks

The gaseous parts of dust disks surrounding main sequence stars have
been the subject of intense investigations since 1985. The origin of
the gas content was a puzzle around such evolved stars. But the
spectral signatures of Beta Pictoris led to the explanation that the
gas is probably produced by the evaporation of many small bodies {see
Lecavelier et al., 2001, Nature 412, 706}. It is thus believed that
BetaPic-like disks are young planetary systems in the clearing-out
phase. Our previous HST observations confirmed the presence of gas
disks similar to the Beta Pic one. Here we propose new STIS
observations of four stars with known circumstellar gas. Four main
objectives can be achieved with STIS observations: the determination
of the composition of the gas, the investigation of the puzzling high
ionization species, the determination of the CO and CI history and
monitoring of spectral variability. The analysis of these issues will
provide valuable clues to the origin of these gas disks and the
subsequent evolution of young planetary systems. In particular, from
abundance studies it will be possible to show if the gas is produced
by evaporation of bodies like extra-solar comets.

STIS 9437

Quantitative Constraints for Massive Star Evolution Models with
Rotation 

Rotation is now recognized as an important physical component in
understanding massive stars. Theory suggests that rotation affects
the lifetimes, chemical yields, stellar evolution tracks, and the
supernova and compact remnant properties {Heger & Langer 2000,
Maeder & Meynet 2000}. In a Cycle 7 program, we proved that
rotational mixing occurs in massive main sequence stars {Venn et al.
2001}. In this proposal, we want to quantitatively test model
predictions and constrain the theory for a better understanding of
massive star evolution. We are requesting HST STIS observations of
the BIII 2066 Angstrom resonance line of seven massive stars in three
young clusters carefully selected from IUE analyses. These stars show
traces of boron depletion, but without nitrogen enrichment; rotation
is the only theory able to explain this abundance pattern. These new
abundances will allow us to test rotating model predictions: that
mixing strength increases with stellar age, mass, and rotation rate.
They will also help to quantitatively constrain the rotational mixing
efficiencies in massive stars. One very high S/N spectrum of a
moderately boron-depleted star is also requested. We wish to measure
its 11B/10B ratio, which is predicted to change as boron is depleted
in the rotating models. This ratio will further confirm rotational
effects and observationally constrain the 10B{p, Alpha} thermonuclear
reaction rate, which is presently highly uncertain. 

STIS 9706

STIS Pure Parallel Imaging Program: Cycle 10

This is the default archival pure parallel program for STIS during
cycle 10.

STIS 9708

STIS Pure Parallel Imaging Program: Cycle 11

This is the default archival pure parallel program for STIS during
cycle 11.

WF/PC-2 9173

The Pattern of Heavy Element Abundances in a Damped LyAlpha Galaxy.

The WF/PC-2 was used to observe the quasar PKS 1127-143. X-ray
absorption associated with an intervening 21-cm and damped LyAlpha$
absorber at z=0.312 in its spectrum has been detected with Chandra.
The advantage of the X- ray measurement is that the derived
metallicity is insensitive to ionization, inclusion of an atom in a
molecule, or depletion onto grains. The X-ray absorption is mostly
due to oxygen, and the abundance agrees with the oxygen abundance of
16-40 lines in a galaxy at the redshift of the absorber. The STIS
spectrum will allow measurement of Zn II, an undepleted iron peak
element. Comparison of the oxygen group measured in the X-rays with
the iron peak nuclei measured will reveal whether the absorber has a
Pop II, halo-type abundance pattern or a Pop I, disk-like abundance
pattern. 

WF/PC-2 9142

The Structure and Physics of Extragalactic Jets.

The WF/PC-2 was used to perform an ongoing investigation into the
physics of jets. It is proposed to obtain polarimetry of the jets of
3C 264 and 3C 78. 

WFPC2 9033

Measuring the mass distribution in the most distant, very X-ray
luminous galaxy cluster known

We propose to obtain a mosaic of deep HST/WFPC2 images to conduct a
weak lensing analysis of the mass distribution in the massive,
distant galaxy cluster ClJ1226.9+3332, recently discovered by us. At
z=0.888 this exceptional system is more X-ray luminous and more
distant than both MS1054.4-0321 and ClJ0152.7-1357, the previous
record holders, thus providing yet greater leverage for cosmological
studies of cluster evolution. ClJ1226.9+3332 differs markedly from
all other currently known distant clusters in that it exhibits little
substructure and may even host a cooling flow, suggesting that it
could be the first cluster to be discovered at high redshift that is
virialized. We propose joint HST and Chandra observations to
investigate the dynamical state of this extreme object. This project
will 1} take advantage of HST's superb resolution at optical
wavelengths to accurately map the mass distribution within 1.9 h^{-1}
50 Mpc via strong and weak gravitational lensing, and 2} use
Chandra's unprecedented resolution in the X-ray waveband to obtain
independent constraints on the gas and dark matter distribution in
the cluster core, including the suspected cooling flow region. As a
bonus, the proposed WFPC2 observations will allow us to test the
results by van Dokkum et al. {1998, 1999} on the properties of
cluster galaxies {specifically merger rate and morphologies} at z~0.8
from their HST study of MS1054.4-0321.

WFPC2 9710

POMS Test Proposal: WFII backup parallel archive proposal

This is a POMS test proposal designed to simulate scientific plans.

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