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3 April 2003

HUBBLE SPACE TELESCOPE

DAILY REPORT       # 3333

PERIOD COVERED: DOY 92

Part 1 of 3

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.

SNAP 9356

SNAPSHOT survey of the Planetary Nebulae population of the Galactic
Bulge 

The spectacular structures seen in HST images of planetary nebulae
{PNe} are generally accepted as originating from hydrodynamical
interactions between stellar winds: the interacting-stellar wind
model {ISW}. Traditionally, the shaping is thought to occur after the
star becomes hot enough to ionize the PN. But recent HST images
indicate that the shaping may occur earlier, and the newer GISW model
puts the shaping during the pre-planetary nebula evolution. The
relative importance of both models is not known: GISW shaping will
account for some fraction of PNe, but estimates range from 15--100
during the PN phase, especially for the youngest PNe. We here propose
an HST Snapshot survey of compact PNe in the Galactic Bulge, to test
these predictions. The Bulge provides the only PNe population for
which progenitor masses are known and nebular ages can be measured.
In support of these HST measurements we have already measured
velocity fields and emission line fluxes. The survey will give an
unbiased sampling of morphologies, and allow evolutionary sequences
to be determined to test the ISW versus the GISW model. By-products
of the survey will be the determination of nebular masses, diameters
and filling factors. We will also obtain the White Dwarf mass
distribution in the Bulge, and the initial-final mass function for
low-mass stars. 

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. 

FGS1R 9408

Calibrating the Mass-Luminosity Relation at the End of the Main
Sequence 

We propose to use HST-FGS1R to calibrate the mass-luminosity
relation {MLR} for stars less massive than 0.2 Msun, with special
emphasis on objects near the stellar/brown dwarf border. Our goals
are to determine M_V values to 0.05 magnitude, masses to 5 than
double the number of objects with masses determined to be less than
0.20 Msun. This program uses the combination of HST-FGS3/FGS1R at
optical wavelengths and ground-based infrared interferometry to
examine nearby, subarcsecond binary systems. The high precision
measurements with HST-FGS3/FGS1R {to 1 mas in the separations} for
these faint targets {V = 10--15} simply cannot be equaled by any
ground based technique. As a result of these measurements, we are
deriving high quality luminosities and masses for the components in
the observed systems, and characterizing their spectral energy
distributions from 0.5 to 2.2 Mum. Several of the objects included
have M < 0.1 Msun, placing them at the very end of the stellar main
sequence. Three of the targets are brown dwarf candidates, including
the current low mass record holder, GJ 1245C, with a mass of
0.062 +/- 0.004 Msun. The payoff of this proposal is high because all
10 of the systems selected have already been resolved with HST-
FGS3/FGS1R during Cycles 5--10 and contain most of the reddest
objects for which masses can be determined. 

STIS/MA2 9465

The Cosmic Carbon Budget

Gaseous carbon drives the chemistry of, and is an important coolant
in interstellar clouds. In solid form, carbon is the second most
abundant element in interstellar dust, the key element contributing
to interstellar extinction, and the dominant heat source in some
interstellar clouds. Given the fundamental importance of this element
to interstellar cloud physics, it is surprising that only 8
measurements of gas- phase carbon abundances exist for neutral
clouds; 7 are in diffuse clouds where the least amount of chemistry
and dust incorporation are expected. The single measurement in a
translucent cloud suggests a C abundance that differs from the
diffuse clouds, but the measurement uncertainties make this
difference statistically insignificant. We, therefore, have no
information about carbon's behavior in translucent clouds, regions
dense enough for chemistry and dust growth to be important but low
enough extinction so that UV spectroscopy is possible {unlike for
molecular clouds}. We propose to measure total gas-phase C abundances
in 6 translucent clouds with our principal scientific goals being to
1} accurately determine the fraction of carbon in the gas and dust
phases in environments bridging the gap between diffuse and molecular
clouds 2} determine the relative depletions of C and O in neutral
clouds with known O-depletion enhancements and 3} explore how the
interstellar gas-phase C/H is related to extinction variations.

 - Continued -

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