Daily Report #4160

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4160

PERIOD COVERED: UT July 20, 2006 (DOY 201)

OBSERVATIONS SCHEDULED

ACS/HRC 10512

Search for Binaries Among Faint Jupiter Trojan Asteroids

We propose an ambitious SNAPSHOT program to survey faint Jupiter
Trojan asteroids for binary companions. We target 150 objects, with
the expectation of acquiring data on about 50%. These objects span
Vmag = 17.5-19.5, a range inaccessible with ground-based adaptive
optics. We now have a significant sample from our survey of brighter
Trojans to suggest that the binary fraction is similar to that which
we find among brighter main-belt asteroids, roughly 2%. However, our
observations suggest a higher binary fraction for smaller main-belt
asteroids, probably the result of a different formation mechanism
{evident also from the physical characteristics of the binaries}.
Because the collision environment among the Trojans is similar to that
of the Main Belt, while the composition is likely to be very
different, sampling the binary fraction among the fainter Trojans
should help us understand the collisional and binary formation
mechanisms at work in various populations, including the Kuiper Belt,
and help us evaluate theories for the origin of the Trojans.
Calibration of and constraints on models of binary production and
collisional evolution can only be done using these large-scale,
real-life physical systems that we are beginning now to find and
utilize.

ACS/HRC 10598

ACS Imaging of Fomalhaut: A Rosetta Stone for Debris Disks Sculpted by
Planets

The Sun and roughly 15% of stars are surrounded by dust disks
collisionally replenished by asteroids and comets. Disk structure can
be directly tied to the dynamical influence of more massive bodies
such as planets. For example, planetary perturbations offset the
center of our zodiacal dust disk ~0.01 AU away from the Sun and also
maintain a ~40 AU radius inner edge to our Kuiper Belt. Here we
propose follow-up observation to the first optical detection of
reflected light from dust grains surrounding the nearby star Fomalhaut
using HST/ACS. We find a belt of material between 133 and 158 AU
radius that has a center position offset ~15 AU from the stellar
position, and with a sharp inner edge. A tenuous dust component
interior to the belt is also detected in the southeast. Given
Fomalhaut's proximity to the Sun {7.7 pc}, these images represent the
closest and highest angular resolution view of an extrasolar analog to
our Kuiper Belt. The center of symmetry offset and the sharp inner
edge of Fomalhaut's belt are evidence for planet-mass objects orbiting
the star as predicted by dynamical theory and simulations. We propose
comprehensive follow-up ACS imaging to fully exploit this discovery
and map the disk around its entire circumference with higher
signal-to-noise and at multiple wavelengths. HST/ACS is certainly the
only facility capable of performing this relatively wide field optical
study at high contrast ratios and diffraction-limited resolution. The
Cycle 14 data will provide key measurements of belt width as a
function of azimuth, the scattered light color of the belt versus the
inner dust component, and the azimuthal structure of the belt. These
data will be used to constrain dynamical models of resonances and
shepherding that ultimately elucidate the dynamical properties of
planet-mass objects in the system.

ACS/HRC/WFC 10487

A Search for Debris Disks in the Coeval Beta Pictoris Moving Group

Resolved observations of debris disks present us with the opportunity
of studying planetary evolution in other solar systems. We propose to
search for debris disks in the Beta Pictoris moving group {8-20 Myrs,
10-50 pc away} , which provides a coeval sample of multiple spectral
types, and it has already produced two magnificent resolved debris
disks: AU Mic and Beta Pic. Such coeval sample will provide us with a
snapshop of the crucial time in disk evolution in which the disk makes
the transition from optically thick to optically thin, and it will be
useful to study the stellar mass dependence of the disk evolution.

ACS/WFC 10551

Gamma-Ray Bursts from Start to Finish: A Legacy Approach

The progenitors of long-duration GRBs are now known to be massive
stars. This result lends credence to the collapsar model, where a
rotating massive star ends its life leaving a black hole or a highly
magnetized neutron star, and confirms its essential aspects. The focus
of attention now is on the black hole or magnetar engines that power
the bursts. Somehow these engines create the most highly relativistic
and highly collimated outflows that we know of, through mechanisms
that no current theory can explain. These astrophysical laboratories
challenge our understanding of relativistic shocks, of mechanisms for
extracting energy from a black hole, and of how physics works in
extreme conditions. The launch of Swift is bringing us into a new era,
where we can make broadband observations that will enable us to study
these fascinating physical processes. We propose here an ambitious,
comprehensive program to obtain the datasets that will become the
standard that any successful model for the central engine must
explain. This programs leverages the HST observations to the maximum
extent by our commitment of Swift observations, a Large program at the
VLA, and extensive ground-based optical resources. By studying the
engines and searching for jets in a variety of events, this program
will investigate the conditions necessary for the engine and jet
formation itself.

ACS/WFC/HRC 10536

What Are Stalled Preplanetary Nebulae? An ACS SNAPshot Survey

Essentially all planetary nebulae {PNs} are aspherical, whereas the
mass-loss envelopes of AGB stars are strikingly spherical. Our
previous SNAPshot surveys of a morphologically unbiased sample of
pre-planetary nebulae {PPNs} -- objects in transition between the AGB
and PN evolutionary phases -- show that roughly half our observed
targets are resolved, with bipolar or multipolar morphologies.
Spectroscopic observations of our sample confirm that these objects
have not yet evolved into planetary nebulae. Thus, the transformation
from spherical to aspherical geometries has already fully developed by
the time these dying stars have become PPNs. Although our current
studies have yielded exciting results, they are limited in two
important ways -- {1} the number of well-resolved objects is still
small {18}, and the variety of morphologies observed relatively
multitudinous, hence no clear trends can yet be established between
morphology and other source properties {e.g., near-IR, far-IR colors,
stellar spectral type, envelope mass}, and {2} the current samples are
strongly biased towards small PPNs, as inferred from their low 60-to-
25 micron flux ratios [R{60/25}1]. However, the prototype of objects
with R{60/25}1, the Frosty Leo Nebula, has a puzzlingly large
post-AGB age {almost 10^4 yr} and a fairly cool central star, very
different from the expectations of single-star stellar evolutionary
models. A proposed, but still speculative, hypothesis for such objects
is that the slow evolution of the central star is due to backflow of
material onto the mass-losing star, retarding its evolution towards
the PN phase. This hypothesis has significant consequences for both
stellar and nebular evolution. We therefore propose a survey of PPNs
with R{60/25}1 which is heavily weighted towards the discovery of
such "stalled PPNs". Supporting kinematic observations using long-slit
optical spectroscopy {with the Keck}, millimeter and radio
interferometric observations {with OVRO, VLA & VLBA} are being
undertaken. The results from this survey {together with our previous
work} will allow us to draw general conclusions about the complex
mass-outflow processes affecting late stellar evolution, and will
provide crucial input for theories of post-AGB stellar evolution. Our
survey will produce an archival legacy of long-standing value for
future studies of dying stars.

CAL/NIC 10784

Further Test of the AUTORESET Mode on NICMO

Test of the short term temperature ripples in the NICMOS dewar. The
test consists of running the NICMOS detectors without the AUTORESET
mode on. Orbits free of NICMOS science observations are to be used and
each mode {ON/OFF} will run for approximately 48 hours. The long
duration is on order to allow the temperature in the dewar to
stabilize. Normal telemetry data will be sufficient for the
temperature monitoring. The darks that will be obtained with this
program will also be used to assess the temperature stability, as well
as a check of the impact of possible artefacts on the detectors.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration - CR Persistence Part 5

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.

NIC2 10603

Multiwavelength Imaging of Edge-on Protoplanetary Disks: Quantifying
the Growth of Circumstellar Dust

Young, edge-on circumstellar disks are uniquely valuable laboratories
for the study of planet formation. In these objects, the central star
is occulted from direct view, significant PSF artifacts are absent,
and the disk is clearly seen as a central dust lane flanked by faint
disk reflected light. The detailed morphology of these nebulae and its
variation with wavelength provide crucial information on the disk
internal structure and the properties of its constituent dust grains.
A key observable is the slope defining the wavelength dependence of
the dust scattering opacity, which becomes shallower when grain growth
has taken place; multiwavelength resolved disk images are the key
dataset enabling such measurements. Recent analyses of three different
edge-on disks have revealed a diversity in their dust properties that
is indicative of different degrees of dust grain evolution having
taken place in each system. This characterization of disk grain
growth, when applied comparatively to a larger sample of these
objects, would enable the construction of an evolutionary sequence of
young disks at successive stages on the road to planet formation. In
pursuit of this goal, we have identified a sample of 15 edge-on disks
previously discovered by HST or groundbased telescopes, but for which
high fidelity, high spatial resolution images do not yet exist in both
the optical and near-infrared. We propose broad-band multicolor
imaging with NICMOS of all these targets, and ACS imaging of nine of
these targets In combination with existing data, the proposed images
will form a complete database of high resolution optical/near-IR
images for these 15 disk systems. Scattered light modeling will be
used to derive the disk structure and dust properties, yielding
results that will be of fundamental importance for our understanding
of grain properties during protoplanetary disk evolution.

WFPC2 10767

Further Resolving the Puzzle of Hybrid Star X-rays

Do Alpha TrA {K2II} and Beta Ind {K1II} have previously unrecognized
X-ray active dwarf companions, leading us astray concerning the
coronal properties of the "hybrid- chromosphere" class? Establishing
the true X-ray luminosities of the hybrids is a basis for
understanding magnetic field generation in evolved supergiants, the
driving of their winds, and the seeding of coronal conditions in their
extended outer envelopes. It also bears on the issue of late-type
dwarfs orbiting main sequence B stars, the evolutionary predecessors
of K bright giants. We propose to directly image the putative hybrid
companions using Chandra, with supporting observations from HST/WFPC2.


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:
#17858-1 RF Transfer Switch Scrub @ 201/15:49z
#17861-1 Clear ACS Event Flag 2 @ 201/20:40z


COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS
GSacq 09 09

FGS
REacq 04 04
OBAD with Maneuver 28 28

SIGNIFICANT EVENTS: (None)