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3\10 HST Daily Rpt No 3316
Part 1 of 3

 HUBBLE SPACE TELESCOPE
  DAILY REPORT # 3316

PERIOD COVERED: DOY 69

OBSERVATIONS SCHEDULED

NICMOS 8791

NICMOS Post-SAA calibration - CR Persistence Part 2

A new procedure proposed to alleviate the CR-persistence problem of 
NICMOS. Dark frames will be obtained immediately upon exiting the SAA 
contour 23, and every time a NICMOS exposure is scheduled within 50 
minutes of coming out of the SAA.  The darks will be obtained in 
parallel in all three NICMOS Cameras. The POST-SAA darks will be 
non-standard reference files available to users with a USEAFTER 
date/time mark. The keyword 'USEAFTER=date/time' will also be added to 
the header of each POST-SAA DARK frame. The keyword must be populated 
with the time, in addition to the date, because HST crosses the SAA ~8 
times per day so each POST-SAA DARK will need to have the appropriate 
time specified, for users to identify the ones they need. Both the raw 
and processed images will be archived as POST-SAA DARKSs. Generally we 
expect that all NICMOS science/calibration observations started within 
50 minutes of leaving an SAA will need such maps to remove the CR 
persistence from the science images. Each observation will need its 
own CRMAP, as different SAA passages leave different imprints on the 
NICMOS detectors.

ACS 9352

The Deceleration Test from Treasury Type Ia Supernovae at Redshifts 
1.2 to 1.6

Type Ia supernovae {SNe Ia} provide the only direct evidence for an 
accelerating universe, an extraordinary result that needs a rigorous 
test. The case for cosmic acceleration rests on the observation that 
SNe Ia at z ~ 0.5 are ~ 0.25 mag fainter than they would be in a 
universe without acceleration. A powerful and straightforward way to 
assess the reliability of the SN Ia measurement and the conceptual 
framework of its interpretation is to look for cosmic deceleration at 
z >= 1. This would be a clear signature of a mixed dark-matter and 
dark-energy universe. Systematic errors in the SN Ia result attributed 
to grey dust or cosmic evolution of the SN Ia peak luminosity would 
not show this change of sign. We have demonstrated proof of this 
concept with a single SN Ia, SN 1997ff at z = 1.7, found and followed 
by HST. The results suggest an early epoch of deceleration, but this 
is too important a conclusion to rest on just one object. Here we 
propose to use HST for observations of six SNe Ia in the range 1.2 <= 
z <= 1.6, that will be discovered as a byproduct from proposed 
Treasury programs for high-latitude ACS surveys. Six objects will 
provide a much firmer foundation for a conclusion that touches on 
important questions of fundamental physics.

STIS/CCD/MA1 9357

Towards a global understanding of accretion physics --, Clues from an 
UV spectroscopic survey of cataclysmic variables

Accretion inflows and outflows are fundamental phenomena in a wide 
variety of astrophysical environments, such as Young Stellar Objects, 
galactic binaries, and AGN. Observationally, cataclysmic variables 
{CVs} are particularly well suited for the study of accretion 
processes. We propose to carry out a STIS UV spectroscopic snapshot 
survey of CVs that fully exploits the diagnostic potential of these 
objects for our understanding of accretion physics. This survey will 
provide an homogenous database of accretion disc and wind outflow 
spectra covering a wide range of mass transfer rates and binary 
inclinations. We will analyse these spectra with state-of-the-art 
accretion disc model spectra {SYNDISK}, testing our current knowledge 
of the accretion disc structure, and, thereby, providing new insight 
into the so far not well understood process of viscous dissipation. We 
will use our parameterised wind model PYTHON for the analysis of the 
radiation driven accretion disc wind spectra, assessing the 
fundamental question whether the mass loss rate correlates with the 
disc luminosity. In addition, our survey data will identify a number 
of systems in which the white dwarf significantly contributes to the 
UV flux, permitting an analysis of the impact of mass accretion on the 
evolution of these compact stars. This survey will at least double, if 
not triple, the number of high-quality accretion disc / wind outflow / 
accreting white dwarf spectra, and we waive our proprietary rights to 
permit a timely use of this database.

STIS 9421

UV Observations of Hubble Flow Type Ia Supernovae

Two independent research groups have presented compelling evidence for 
an accelerating universe from the observation of high-redshift Type Ia 
supernovae {SNe Ia}. These findings have such important ramifications 
for cosmology that every effort must be made to thoroughly test the 
calibrated standard candles on which they are based, improve upon our 
understanding of the underlying physics of the SN Ia explosion 
mechanism and attempt to constrain or determine their progenitors. 
Here we propose to obtain STIS UV spectra of five Hubble Flow SNe Ia. 
The spectra will be taken at weekly intervals over a range in time 
starting slightly before maximum light and extending to +30 days. 
These observations will accomplish the following three goals: {1} 
Calibration of the rest frame UV light curves of SNe Ia and an 
assessment of their potential use as distance indicators through UV 
light curve shape analyses. {2} Improvement in our understanding of 
the physics of SNe Ia, metallicity/evolutionary effects and 
correlations between peak brightness and UV spectral features. {3} 
Calibration of the SNe Ia previously observed by HST at high-redshift. 
For z > 0.8 SNe Ia discovered by the Supernova Cosmology Project, the 
High-Z Supernovae Search Team and future HST discovered SNe Ia {like 
SN 1997ff found in the HDF} this data is crucial for proper 
cross-filter K-corrections and calibration of the supernova 
photometry.

ACS/STIS 9451

ACS Imaging and STIS Spectroscopy of Binary Brown Dwarfs

We have compiled a sample of 9 spatially resolved binary brown dwarfs 
{18 objects}, and now propose ACS imaging and STIS spectroscopic 
follow-up observations. While theoretical models on the interplay of 
chemical and physical processes governing brown dwarf atmospheres have 
reached a high level of sophistication, interpretation of 
observational data remains difficult. As brown dwarfs never stabilize 
themselves on the hydrogen main sequence, there is always an ambiguity 
between the temperature or luminosity of any brown dwarf and its mass 
or age. The individual components of brown dwarf binaries, however, 
are expected to be coeval and have the same underlying chemical 
composition. This provides crucial constraints on any model, thus 
greatly reducing the number of the free parameters. The aim is to 
obtain photometric and spectroscopic data to probe the physical and 
chemical properties of the brown dwarf atmospheres, as well as second 
epoch astrometric data to characterize th e orbital motion. The study 
will provide important feedback on theoretical model atmospheres and
evolutionary tracks for brown dwarfs. As such, it will be an important 
step towards a better understanding of objects with spectral 
properties intermediate between those of giant planets and late-type 
stars.

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