NASA Hubble Space Telescope Daily Report #3866

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT        # 3866

PERIOD COVERED: DOY 143

OBSERVATIONS SCHEDULED

ACS/HRC 10198

Probing the Dynamics of the Galactic Bar through the Kinematics of
Microlensed Stars

The observed optical depths to microlensing of stars in the Galactic
bulge are difficult to reconcile with our present understanding of
Galactic dynamics. The main source of uncertainty in those comparisons
is now shifting from microlensing measurements to the dynamical models
of the Galactic bar. We propose to constrain the Galactic bar models
with proper motion observations of Bulge stars that underwent
microlensing by determining both the kinematic identity of the
microlensed sources and the importance of streaming motions. The
lensed stars are typically farther than randomly selected stars.
Therefore, our proper motion determinations for 36 targeted MACHO
events will provide valuable constraints on the dynamics of bulge
stars as a function of distance. The first epoch data for our proposed
events is already available in the HST archive so the project can be
completed within a single HST cycle. The exceptional spatial
resolution of HST is essential for completion of the project.
Constraints on the total mass in the bulge will ultimately lead to the
determination of the amount of dark matter in inner Galaxy.

ACS/HRC 10707

First Mass Measurement of a Planet Found By Microlensing

We will use ACS to determine the mass of the extra-solar planet found
in the ongoing microlensing event OGLE-2005-BLG-071. This source will
be imaged in V {F555W} and I {F814W} at two epochs, one “very soon”
while the event is still significantly magnified, and the other after
5 months when it has returned to baseline. If the centroid does not
move, this will demonstrate that the “blended light” detected in the
event is “perfectly aligned” {within 15 mas, 1 sigma} with the source,
and so is almost certainly the lens. V and I photometry will then
permit an estimate of its mass and distance. Since the planet-star
mass ratio is already known to be 0.007, this will yield a planet
mass. Even if the HST images show that the blended light is not
aligned with the source {and so is not from the lens}, the HST
observations will still strongly constrain the mass by helping to
measure the “microlens parallax”, which when combined with the
“angular Einstein radius”, determines the mass. Thus, the observations
have a very high probability of success. The observations are
time-critical because the first one must be taken while the event is
still in progress.

ACS/HRC/WFC 10389

ACS CCDs daily monitor – Cycle 13 – Part 2

This program consists of a set of basic tests to monitor, the read
noise, the development of hot pixels and test for any source of noise
in ACS CCD detectors. The files, biases and dark will be used to
create reference files for science calibration. This programme will be
for the entire lifetime of ACS.

ACS/S/C/SBC 10233

Determining the Instability Strip for Accreting White Dwarfs

Using UV observations with SBC and PR110L, we will obtain spectra of 3
newly discovered pulsating white dwarfs found among recent cataclysmic
variables identified in the SDSS. Our Cycle 8 observations of the only
previously known accreting, pulsating, white dwarf in GW Lib revealed
large amplitude UV pulsations, a spectrum that showed metals and
required a dual temperature fit with a high white dwarf mass. Since
accretion likely causes abundance, rotation, and atmospheric
temperature differences in accreting white dwarfs versus single white
dwarfs, we will use these systems to explore the location of the
instability strip for accreting white dwarfs and determine whether
they are all massive and spotted objects. Light curves can be
constructed at different wavelengths to aid in mode identification.
Having knowledge of the atmospheres and interior structure of 4 sytems
will provide great insight into the interaction of accretion, stellar
pulsation and long term evolution. Due to optical contamination by the
disk, stream, and/or secondary, the UV is the optimum regime to study
pulsating, accreting white dwarfs.

ACS/WFC 10135

Unveiling the Progenitors and Physics of Cosmic Explosions

GRBs and XRFs are clearly highly asymmetric explosions and require a
long-lived power source {central engine}. In contrast, nearby
core-collapse events are essentially spherical explosions. However,
the failure of spherical neutrino driven collapses has led to the idea
that asymmetric energy release is essential for the explosion. The
recent finding of a Type Ic SN in GRB 030329, the association of the
low energy event GRB 980425 with SN 1998bw, the theoretical
development discussed above and the rise of collapsar models make it
timely to consider whether all these explosions contain engines. Given
the uncertainties in theoretical modeling it is clear that
observations are needed to guide models. A priori there is little
reason to expect connection between the ultra-relativistic jet that
powers the GRB and the explosive nucleosynthesis of the ~0.5 solar
masses of Nickel-56 that powers the accompanying supernova. We propose
a comprehensive program of ACS photometric searches {and measurements}
for SNe associated with GRBs and XRFs. In concert, we will undertake
ground-based spectroscopy to determine velocity widths, and measure
engine parameters from pan-chromatic afterglow observations. Our goal
is to produce a comprehensive database of engine and SN physical
parameters against which theoretical modeling will be guided.

ACS/WFC/NIC2 10189

PANS-Probing Acceleration Now with Supernovae

Type Ia supernovae {SNe Ia} provide the most direct evidence for an
accelerating Universe, a result widely attributed to dark energy.
Using HST in Cycle 11 we extended the Hubble diagram with 6 of the 7
highest-redshift SNe Ia known, all at z>1.25, providing conclusive
evidence of an earlier epoch of cosmic deceleration. The full sample
of 16 new SNe Ia match the cosmic concordance model and are
inconsistent with a simple model of evolution or dust as alternatives
to dark energy. Understanding dark energy may be the biggest current
challenge to cosmology and particle physics. To understand the nature
of dark energy, we seek to measure its two most fundamental
properties: its evolution {i.e., dw/dz}, and its recent equation of
state {i.e., w{z=0}}. SNe Ia at z>1, beyond the reach of the ground
but squarely within the reach of HST with ACS, are crucial to break
the degeneracy in the measurements of these two basic aspects of dark
energy. The SNe Ia we have discovered and measured with HST in Cycle
11, now double the precision of our knowledge of both properties. Here
we propose to quadruple the sample of SNe Ia at z>1 in the next two
cycles, complementing on-going surveys from the ground at z<1, and again doubling the precision of dark energy constraints. Should the current best fit model prove to be the correct one, the precision expected from the current proposal will suffice to rule out a cosmological constant at the 99% confidence level. Whatever the result, these objects will provide the basis with which to extend our empirical knowledge of this newly discovered and dominant component of the Universe, and will remain one of the most significant legacies of HST. In addition, our survey and follow-up data will greatly enhance the value of the archival data within the target Treasury fields for galaxy studies.

ACS/WFC/NIC3 10195

Probing the Surroundings of a Highly Luminous Redshift 6.5 Galaxy

We propose deep images of a recently discovered galaxy at z=6.535,
which is among the most luminous Lyman-alpha emitting galaxies known
at high redshift. The brightness and rarity of this source imply that
it is associated with a high peak in the matter density distribution.
{It is the brightest Lyman alpha source in 2e5 comoving Mpc3, with a
luminosity of 6 L*.} Further objects in this peak are expected to be
visible with HST’s sensitivity. The Lyman alpha line has a large rest
frame equivalent width, with a lower bound >100 Angstroms. Such a
large equivalent width would be impossible for objects embedded in
neutral gas, and instead requires either that {a} the universe was
reionized before z=6.5 or {b} the galaxy resides in a local ionized
bubble, in which case an additional contribution to the ionizing
photon budget from presently undetected neighbors is required. With 19
orbits of ACS and NICMOS imaging, we will measure this object’s
morphology and spectral energy distribution, thus searching for either
active nuclei or old stellar populations. We will also search for
possible neighbors, which could establish the first known galaxy group
at z>6, and may provide sufficient ionizing flux to allow the escape
of the observed Lyman alpha photons in a neutral universe. If
neighbors are not found, it will lead to an upper bound on the neutral
fraction in the general IGM at z=6.5.

NICMOS 8790

NICMOS Post-SAA calibration – CR Persistence Part 1.

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.

WFPC2 10359

WFPC2 CYCLE 13 Standard Darks

This dark calibration program obtains dark frames every week in order
to provide data for the ongoing calibration of the CCD dark current
rate, and to monitor and characterize the evolution of hot pixels.
Over an extended period these data will also provide a monitor of
radiation damage to the CCDs.

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:

COMPLETED OPS NOTES: (None)

                                 SCHEDULED     SUCCESSFUL    FAILURE TIMES 
 FGS Gsacq                     06                       06 
 FGS Reacq                     09                       09 
 FHST Update                  12                       12 
 LOSS of LOCK 

SIGNIFICANT EVENTS:  (None)