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21 April 2003

HUBBLE SPACE TELESCOPE

DAILY REPORT     #3345

PERIOD COVERED:  DOY 108-110

Part 5 of 5

WFPC2 9334

Dynamical Masses of White Dwarfs from Resolved Sirius-Like Binaries

In Cycle 8 we initiated a WFPC2 snapshot survey for resolved,
``Sirius-like'' systems containing hot white-dwarf companions of
cooler main-sequence stars. Out of 17 systems observed to date, 8
have been resolved with WFPC2 by using UV filters. Two of the
resolved systems---56 Persei and Zeta Cygni---have predicted or known
orbital periods short enough that dynamical masses can be determined
for the white dwarfs within reasonable times. These would thus add to
the extremely small number of white dwarfs presently having
accurately and directly measured masses. We propose to image them
annually in the UV with WFPC2. In addition, we will observe Zeta Cyg
with FGS in order to measure the absolute motion of the optical
component, needed for the mass solution. We also propose to observe
Sirius itself with WFPC2 over the next 3 Cycles. The resulting
astrometric data will not only greatly improve the precision of the
binary orbit and the dynamical mass measurements for both the
main-sequence and white-dwarf components, but will also test
definitively for the claimed presence of a third body in this famous
system. 

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.

WFPC2 9709

POMS Test Proposal: WFII parallel archive proposal

This is the generic target version of the WFPC2 Archival Pure
Parallel program. The program will be used to take paralell images of
random areas of the sky, following the recommendations of the 2002
Parallels Working Group.

WFPC2 9594

WFPC2 CYCLE 11 SUPPLEMENTAL DARKS pt2/3

This dark calibration program obtains 3 dark frames every day to
provide data for monitoring and characterizing the evolution of hot
pixels 

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies:
(The following are preliminary reports of potential non-nominal
performance that will be investigated.)

HSTARs:
8995 - LOL during GSacq(2,3,3) {at} 088/1733z
8996 - REacq(1,2,1) requires 2 attempts to achieve Finelock Data
Valid {at} 097/0419z

COMPLETED OPS REQs:
16940-0 - Clear NICMOS Error Log {at} 108/1714z

OPS NOTES EXECUTED:
None

                       SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq                 22             22
FGS REacq                 27             27
FHST Update               43             43
LOSS of LOCK

SIGNIFICANT EVENTS: None

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