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04 Apr 2003

HUBBLE SPACE TELESCOPE

DAILY REPORT        # 3332

PERIOD COVERED: DOY 91

Part 1 of 4

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.

WFPC2/FGS 9332

WFPC2 Observations of Astrophysically Important Visual Binaries

This is a continuation of a Cycle 7-8-9 Long-Term project. The
program consists of annual or biannual WFPC2 or FGS observations of
three visual binary stars that will ultimately yield fundamental
astrophysical results, once their orbits and masses are determined.
Our targets are the following: {1} Procyon {P=41 yr}, for which our
first WFPC2 images yielded an extremely accurate angular separation
of the bright F star and its very faint white-dwarf companion.
Combined with ground-based astrometry of the bright star, our
observation significantly revised downward the derived masses, and
brought Procyon A into excellent agreement with theoretical
evolutionary tracks for the first time. The mass of Procyon B,
however, implies a completely unexpected chemical composition for the
white dwarf, and now poses a sharp evolutionary puzzle. With the
continued monitoring proposed here, we will obtain masses to an
accuracy of better than 1%, providing a testbed for theories of
Sun-like stars and white dwarfs. {2} G 107-70, a close double white
dwarf {P=19 yr} that promises to add two accurate masses to the tiny
handful of white-dwarf masses that are directly known from dynamical
measurements. {3} Mu Cas {P=21 yr}, a famous metal-deficient G dwarf
for which accurate masses will lead to the stars' helium contents,
with cosmological implications. 

FGS 9346

The Masses of the O-type Binary 15 Monocerotis

The O-type star 15 Mon {HD 47839} was recently discovered to be an
astrometric and spectroscopic binary with an orbital period of 25
years; it is the first known O-star system to bridge the
observational gap between the period regimes normally probed by these
techniques. An analysis of both the radial velocity curve and
astrometric orbit yields the masses of the components and distance to
the system. Both radial velocity and astrometric measurements are
scant at present, but the system is now close to periastron and
continued spectroscopic and astrometric monitoring will lead to a
definitive orbit and yield important information about the masses of
O-type stars. FGS TRANS mode measurements of separation, position
angle, and magnitude difference {begun in Cycle 5} are needed to
bridge the gap between recent speckle observations and anticipated
observations with CHARA Array optical interferometer. In addition,
new field astrometry measurements {FGS POS mode} will provide the
proper motion, parallax, and the binary motion around the center of
mass. The POS data will provide an accurate estimate of the mass
ratio and an improved estimate of distance, and taken together with
the spectroscopic and astrometric orbital data, we should be able to
obtain masses for both components accurate to a few percent. 

STIS 9374

The FUV Flux Irradiating the Surfaces of Protostellar Disks

We propose to use STIS to determine the Far-Ultraviolet {FUV}
radiation field in 3 proto-planetary disk systems. These systems:
LkCa 15, GM Aur, and DM Tau, are among a handful of sources that can
be subjected to detailed chemical studies with the current generation
of millimeter-wave instruments. Such studies have found that the
disks have a rich molecular chemistry, which appears to be controlled
by the FUV radiation field {Qi 2001; Dutrey et al 1997; Kastner et al
1997}. These observations will allow, for the first time, a firm
characterization of the FUV radiation field impinging on the surfaces
of circumstellar disks. Knowledge of the FUV field for each object
will allow for theoretical chemical models to be created specific to
each object and compared to observations. Since these objects will
remain, for some time, the main templates for chemical studies of
extra-solar disks this project will provide the real UV data required
to push theory forward. Given that molecules are excellent probes of
their environment, the new information will place better constraints
on the virtually unknown vertical structure of proto-planetary disks.
This project is unique in scope and will increase our limited
understanding of disk chemical evolution, but also improve our
knowledge of uncertain physical processes, such as the possible
dissipation of outer disks by photo-evaporation and on the timescales
of dust grain growth. 

SNAP/STIS 9434

A SNAPSHOT Survey of the Hot Interstellar Medium

We propose to obtain SNAPSHOT STIS echelle observations of key
tracers of hot interstellar gas {CIV, NV and SiIV} for selected FUSE
Team OVI survey targets with known UV fluxes. By taking advantage of
the SNAPSHOT observing mode we will efficiently obtain a large number
of spectra suitable for the study of the highly ionized hot component
of the interstellar medium {ISM}. Our goals are to explore the
physical conditions in and distribution of such gas, as well as to
explore the nature of the interfaces between the hot ISM and the
other interstellar gas phases. Using inter--comparisons of the
various ionic ratios for CIV, NV, OVI and SiIV, we will be able to
discriminate between the various models for the production of the
highly ionized gas in the Galactic ISM. The survey will also enable
detailed studies of regions already known to contain hot gas through
X-ray emission measurements {e.g., SNRs and radio loops}. The
proposed SNAPSHOT observations will extend our previous Cycle 9
survey {which was compromised by the STIS side 1 failure}, and should
roughly double the number of stars for which high quality STIS
observations of the important hot gas tracers are available, enabling
us to derive a truly global view of the hot ISM.

 - Continued -

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