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HUBBLE SPACE TELESCOPE

DAILY REPORT       # 3326

PERIOD COVERED: DOY 83

Part 1 of 3

OBSERVATIONS SCHEDULED

FLIGHT OPERATIONS SUMMARY:

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.

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 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. 

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. 

 - Continued -

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