Daily Report #4753

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT****** #4753

PERIOD COVERED: 5am December 9 - 5am December 10, 2008 (DOY
*************************** 344/1000z-345/1000z)

OBSERVATIONS SCHEDULED

ACS/SBC 11110

Searching for Lyman Apha Emission from FUSE Lyman Continuum
Candidates

We have recently been granted time on FUSE to characterize the escape
fraction of hydrogen Lyman continuum (Lyc) photons from a
morphologically diverse set of star forming galaxies. The FUSE program
is designed to provide ~ 5 sigma detections of Lyc photons emitted
from star forming galaxies with escape fractions ~5%. With this
proposal we seek hydrogen Lyman alpha (Lya) observations of a
representative subset of the FUSE program targets to constrain the
observational relationship between Lyc, Lya, and hydrogen Balmer line
emission in these systems. Such observations explore the detailed
balance between the simple optically thin (Case A) and optically thick
(Case B) limits in recombination theory. The ultimate goal of this
program is to quantify the relationship between escaping Lya and Lyc
emission and the first structures that form in the early universe.

FGS 11704

The Ages of Globular Clusters and the Population II Distance Scale

Globular clusters are the oldest objects in the universe whose age can
be accurately determined. The dominant error in globular cluster age
determinations is the uncertain Population II distance scale. We
propose to use FGS 1r to obtain parallaxes with an accuracy of 0.2
milliarcsecond for 9 main sequence stars with [Fe/H] -1.5. This will
determine the absolute magnitude of these stars with accuracies of
0.04 to 0.06mag. This data will be used to determine the distance to
24 metal-poor globular clusters using main sequence fitting. These
distances (with errors of 0.05 mag) will be used to determine the ages
of globular clusters using the luminosity of the subgiant branch as an
age indicator. This will yield absolute ages with an accuracy 5%,
about a factor of two improvement over current estimates. Coupled with
existing parallaxes for more metal-rich stars, we will be able to
accurately determine the age for globular clusters over a wide range
of metallicities in order to study the early formation history of the
Milky Way and provide an independent estimate of the age of the
universe.

The Hipparcos database contains only 1 star with [Fe/H] -1.4 and an
absolute magnitude error less than 0.18 mag which is suitable for use
in main sequence fitting. Previous attempts at main sequence fitting
to metal-poor globular clusters have had to rely on theoretical
calibrations of the color of the main sequence. Our HST parallax
program will remove this source of possible systematic error and yield
distances to metal-poor globular clusters which are significantly more
accurate than possible with the current parallax data. The HST
parallax data will have errors which are 10 times smaller than the
current parallax data. Using the HST parallaxes, we will obtain main
sequence fitting distances to 11 globular clusters which contain over
500 RR Lyrae stars. This will allow us to calibrate the absolute
magnitude of RR Lyrae stars, a commonly used Population II distance
indicator.

FGS 11943

Binaries at the Extremes of the H-R Diagram

We propose to use HST/Fine Guidance Sensor 1r to survey for binaries
among some of the most massive, least massive, and oldest stars in our
part of the Galaxy. FGS allows us to spatially resolve binary systems
that are too faint for ground-based, speckle or optical long baseline
interferometry, and too close to resolve with AO. We propose a
SNAP-style program of single orbit FGS TRANS mode observations of very
massive stars in the cluster NGC 3603, luminous blue variables, nearby
low mass main sequence stars, cool subdwarf stars, and white dwarfs.
These observations will help us to (1) identify systems suitable for
followup studies for mass determination, (2) study the role of
binaries in stellar birth and in advanced evolutionary states, (3)
explore the fundamental properties of stars near the main
sequence-brown dwarf boundary, (4) understand the role of binaries for
X-ray bright systems, (5) find binaries among ancient and nearby
subdwarf stars, and (6) help calibrate the white dwarf mass - radius
relation.

FGS/S/C 11945

Asteroseismology of Extrasolar Planet Host Stars

Detections of stellar oscillations, although a very demanding task in
terms of observing time, offers a return of more accurate knowledge
about the structure of stars than can be obtained in any other way. In
particular, detecting the 10-15 highest amplitude modes in solar-like
stars to signal-to-noise of just a few sigma each allows robust
constraints on the stellar density to 1%, and the stellar age to
within 5-10% of its main sequence lifetime. Ten day observing runs
using the FGS as a photometer on any of the 5 best transiting planet
systems would enable these asteroseismology returns. From more
precisely observed transit shapes than can be obtained from the ground
a completely independent constraint on stellar density to ~1% can be
obtained. The long observation sets required for asteroseismology also
provide an excellent opportunity of detecting transits from other
planets, e.g. hypothesized inner -orbit Hot Earths, should any exist.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS: (None)

COMPLETED OPS REQUEST:

18370-0 - Adjust NCS CPL Setpoint

COMPLETED OPS NOTES: (None)

*********************** SCHEDULED***** SUCCESSFUL

FGS GSacq************** 06***************** 06
FGS REacq*************** 0****************** 0
OBAD with Maneuver **** 12***************** 12

SIGNIFICANT EVENTS: (None)