Status Report

NASA Hubble Space Telescope Daily Report # 3396

By SpaceRef Editor
July 2, 2003
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STIS 9359

The Old Star CS 31082-001, the Age of the Universe, and the Nature of the

We propose to observe the newly discovered r-process-element enhanced
star, CS 31082-001 {Fe/H ~ -2.9}, in order to determine abundances of
the heaviest stable elements, using absorption lines that are only
reachable in the near UV. This star is the only halo star for which a
uranium detection has been reported, and for which the U/Th
chronometer has been used to specify an age limit. In order to improve
the accuracy of the age determination from U/Th we require abundance
estimates of the daughter nuclides –Pb & Bi– for which only upper
limits have been obtained from ground-based observations. Such
estimates will provide crucial constraints on the initial production
ratio of U/Th, resulting in a more strict lower limit on the age of
this star’s progenitor, hence on the age of the Universe. Measurements
of 3rd-peak neutron-capture elements, such as Pt, Os, Ir, and Au, all
with lines in the 2400-3100 Angstrom range, will expand our knowledge
of element synthesis in the early Galaxy. Our recent ESO-VLT data
indicate that the neutron-capture elements in this star exhibit
different enhancements as compared with the previously known “
r-process star” CS 22892-052, an apparent anomaly that must be
resolved. CS 31082-001 is the ideal HST target in its class — it is
4-times brighter than CS 22892-052, and less affected by molecular
line blending. Consequently, these HST data will become the reference
in all future studies of similar stars.


The Physical Parameters of the Hottest, Most Luminous Stars as a
Function of Metallicity

We have obtained excellent, new ground-based blue optical and HAlpha
spectra of a sample of very early-type stars in the Magellanic Clouds
in order to measure their physical properties, for comparison with the
extensive data that exists for higher-metallicity Galactic stars. Our
aim is to understand how effective temperatures depend upon
metallicity {necessary in determining IMFs}, and to explore the
astrophysically interesting regime of stars of extreme temperatures,
masses, and luminosities. In order to do this, we need to measure the
stellar wind terminal velocities for our stars, necessary to constrain
the stellar models. These can only be measured with STIS/FUV on HST.
In addition, we will obtain higher spatial resolution data on the
HAlpha line for stars for which nebular contamination is significant
in our ground-based data. We also include several R136 stars with
excellent STIS/CCD data but which lack UV line measures. These new HST
data will provide important information about the strengths of stellar
winds at extreme luminosities and the calibration of the Wind
Momentum- Luminosity Relationship at lower metallicities. This
proposal was highly rated in Cycle 9, but only 4 snapshots were
obtained. We have completed the analysis of these plus additional data
from the archives, but need spectra of the remaining objects if we are
to answer the questions we pose.


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.

ACS 9462

Systemic and Internal Proper Motions of the Magellanic Clouds from
Astrometry with ACS

We request first epoch observations with ACS of Magellanic Cloud
fields centered on background quasars. Second epoch observations will
be requested ~ 5 years later to allow the measurement of the systemic
and internal proper motions of the Clouds with error <~0.05 mas/year. These motions are of fundamental importance. The systemic motions of the LMC and SMC probe the gravitational potential of the dark halo. The internal proper motion due to rotation can be exploited to yield a rotational parallax distance to the LMC; the first time that this will be done for any galaxy. This is particularly important for the LMC because of its crucial role in the extragalctic distance ladder. Previous measurements of the proper motion of the LMC yield a systemic component ranging from 1.4 mas/year to 3.4 mas/year {differing by several times the quoted errors}, with no useful determination of the internal motions. The main problem with measurements of the proper motion of the LMC has been the lack of a sample of background quasars to use as reference frame. We have recently been able to identify a sample of 54 quasars behind the Magellanic Clouds from their variability characteristics in the MACHO database. With this sample and the advent of ACS an accurate proper motion measurement has become possible for the very first time.

ACS 9472

A Snapshot Survey for Gravitational Lenses among z >= 4.0 Quasars

Over the last few years, the Sloan Digital Sky Survey has
revolutionized the study of high-redshift quasars by discovering over
200 objects with redshift greater than 4.0, more than doubling the
number known in this redshift interval. The sample includes eight of
the ten highest redshift quasars known. We propose a snapshot imaging
survey of a well-defined sample of 250 z > 4.0 quasars in order to
find objects which are gravitationally lensed. Lensing models
including magnification bias predict that at least 4% of quasars in a
flux-limited sample at z > 4 will be multiply lensed. Therefore this
survey should find of order 10 lensed quasars at high redshift; only
one gravitationally lensed quasar is currently known at z > 4. This
survey will provide by far the best sample to date of high-redshift
gravitational lenses. The observed fraction of lenses can put strong
constraints on cosmological models, in particular on the cosmological
constant Lambda. In addition, magnification bias can significantly
bias estimates of the luminosity function of quasars and the evolution
thereof; this work will constrain how important an effect this is, and
thereby give us a better understanding of the evolution of quasars and
black holes at early epochs, as well as constrain models for black
hole formation.


Completing A Near-Infrared Search for Very Low Mass Companions to
Stars within 10 pc of the Sun

Most stars are fainter and less massive than the Sun. Nevertheless,
our knowledge of very low mass {VLM} red dwarfs and their brown dwarf
cousins is quite limited. Unknown are the true luminosity function
{LF}, multiplicity fraction, mass function, and mass-luminosity
relation for red and brown dwarfs, though they dominate the Galaxy in
both numbers and total mass. The best way to constrain these relations
is a search for faint companions to nearby stars. Such a search has
several advantages over field surveys, including greater sensitivity
to VLM objects and the availability of precise parallaxes from which
luminosities and masses can be derived. We propose to complete our
four-filter NICMOS snapshot search for companions to stars within 10
pc. With a 10 sigma detection limit of M_J ~ 20 at 10 pc, we can
detect companions between 10 and 100 AU that are at least 9 mag
fainter than the empirical end of the main sequence and at least 6.5
mag fainter than the brown dwarf Gl 229B. When completed, our search
will be the largest, most sensitive, volume-limited search for VLM
companions ever undertaken. Our four-filter search will permit
unambiguous identification of VLM-companion candidates for follow-up
observation. Together with IR speckle and deep imaging surveys, our
program will firmly establish the LF for VLM companions at separations
of 1-1000 AU and the multiplicity fraction of all stars within 10 pc.

WFPC2 9595


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

STIS 9606

CCD Dark Monitor-Part 2

Monitor the darks for the STIS CCD.

STIS 9608

CCD Bias Monitor – Part 2

Monitor the bias in the 1×1, 1×2, 2×1, and 2×2 bin settings at gain=1,
and 1×1 at gain = 4, to build up high-S/N superbiases and track the
evolution of hot columns.

STIS 9615

Cycle 11 MAMA Dark Monitor

This test performs the routine monitoring of the MAMA detector dark
noise. This proposal will provide the primary means of checking on
health of the MAMA detectors systems through frequent monitoring of
the background count rate. The purpose is to look for evidence of
change in dark indicative of detector problem developing.

STIS 9633

STIS parallel archive proposal – Nearby Galaxies – Imaging and

Using parallel opportunities with STIS which were not allocated by the
TAC, we propose to obtain deep STIS imagery with both the Clear
{50CCD} and Long-Pass {F28X50LP} filters in order to make
color-magnitude diagrams and luminosity functions for nearby galaxies.
For local group galaxies, we also include G750L slitless spectroscopy
to search for e.g., Carbon stars, late M giants and S-type stars. This
survey will be useful to study the star formation histories, chemical
evolution, and distances to these galaxies. These data will be placed
immediately into the Hubble Data Archive.

ACS 9657

ACS Internal Flat Field Stability

The flat field stability and characterization obtained during the
ground calibration and SMOV phases will be tested and verified through
a sub-sample of the filter set. Only internal exposures with the
calibration lamps will be required.

ACS 9674

CCD Daily Monitor

This program consists of basic tests to monitor, the read noise, the
development of hot pixels and test for any source of noise in ACS CCD
detectors. This programme will be executed once a day for the entire
lifetime of ACS.

STIS 9708

STIS Pure Parallel Imaging Program: Cycle 11

This is the default archival pure parallel program for STIS during cycle

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 parallel images of random
areas of the sky, following the recommendations of the 2002 Parallels
Working Group.

WFPC2 9710

POMS Test Proposal: WFII backup parallel archive proposal

This is a POMS test proposal designed to simulate scientific plans.

ACS/HRC 9805

OGLE-TR-56b: The Most Interesting Transiting Planet

Our team has recently succeeded in confirming spectroscopically the
discovery of the first extrasolar giant planet found in a transit
search: OGLE-TR-56b. Its main parameters are: mass = 0.9 Jupiters,
size = 1.3 Jupiters. Thus, OGLE-TR-56b appears to be similar to HD
209458b, the only other known transiting giant planet. Unfortunately,
our planet radius determination is uncertain due to the very limited
precision of the ground-based photometry, and does not allow for a
meaningful comparison with theoretical model predictions. We propose
HST observations with the ACS-HRC of the main transit of OGLE-TR-56b,
which will improve the precision and the accuracy of the planet
parameters by close to a factor of 10. In addition, we propose a
timing experiment for the planet’s extremely close orbit {1.2-day
period, 0.023 AU from the star}, which will allow us to detect the
orbital decay and test convection theories.

ACS 9984

Cosmic Shear With ACS Pure Parallels

Small distortions in the shapes of background galaxies by foreground
mass provide a powerful method of directly measuring the amount and
distribution of dark matter. Several groups have recently detected
this weak lensing by large-scale structure, also called cosmic shear.
The high resolution and sensitivity of HST/ACS provide a unique
opportunity to measure cosmic shear accurately on small scales. Using
260 parallel orbits in Sloan textiti {F775W} we will measure for the
first time: beginlistosetlength sep0cm setlengthemsep0cm setlength
opsep0cm em the cosmic shear variance on scales <0.7 arcmin, em the skewness of the shear distribution, and em the magnification effect. endlist Our measurements will determine the amplitude of the mass power spectrum sigma_8Omega_m^0.5, with signal-to-noise {s/n} ~ 20, and the mass density Omega_m with s/n=4. They will be done at small angular scales where non-linear effects dominate the power spectrum, providing a test of the gravitational instability paradigm for structure formation. Measurements on these scales are not possible from the ground, because of the systematic effects induced by PSF smearing from seeing. Having many independent lines of sight reduces the uncertainty due to cosmic variance, making parallel observations ideal.


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

HSTAR 9067: GS Acquisition (3,2,3) @ 182/09:45:05Z resulted in FL
backup on FGS 3. HST was in LOS at time of event, upon AOS, there
were no FGS flags indicating SRLEX or SSLEX. Under investigation.

HSTAR 9069: GS Acquisition (1,3,3) @ 182/23:42:54Z resulted in FL
backup on FGS 1 due to SSLE on FGS 3. U2,3FM @ 183/23:36:49Z and
182/23:39:34Z showed attitude errors. May @ 182/23:50:35Z showed
errors. Under investigation.

COMPLETED OPS REQs: 16998-0 Engineering Dump for BCT Critical
Engineering Data @ 183/03:16:56z

1115-0 CCC IP CONFIG Connections @ 182/11:20z
1126-0 Bat Cap Test- Adjust CCC5 K1 Level2 Limits 183/0356z

FGS GSacq 13 13
FGS REacq 06 06
FHST Update 14 14


Initial commanding for Battery 4 Capacity Test started @ 182/10:27Z
with configuration of TMDIAGs (OR 16996-1 with attached Battery 4
Capacity Test script). Battery 4 was connected to the Diode Bus C
and high rate discharge was initiated @ 182/10:43Z, discharge
continued nominally until approximately 182/23:57Z (during ZOE) when
the 15 Volt termination point was reached. SA Section 4 was connected
to Battery 4 @ 183/01:32Z for recharging the battery. Preliminary
capacity is 55.8 Ah measured through the 5.1 Ohm resistor. Plan to
configure the FSW back to a 6-battery system @ approximately

SpaceRef staff editor.