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)
-Lynn
Lynn F. Bassford
CHAMP HST Missions Operations Manager
Lockheed Martin Technical Operations
GSFC PH#: 301-286-2876
"The Hubble Space Telescope is the Babe Ruth of astronomical
observatories, the Muhammad Ali of cosmic photography
"
- Robert Roy Britt, space.com 7-14-4
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