HUBBLE
SPACE TELESCOPE - Continuing to collect World Class Science
DAILY
REPORT # 4606
PERIOD
COVERED: 5am May 07 - 5am May 08, 2008 (DOY 128/0900z - 129/0900z)
OBSERVATIONS
SCHEDULED
WFPC2
10896
An Efficient
ACS Coronagraphic Survey for Debris Disks around Nearby
Stars
We
propose to finish our Cycle 11 optical survey for nearby debris disks
using
the ACS/HRC coronagraph. Out of 43 orbits originally proposed for
the
survey, 23 orbits were allocated, leading to a survey of 22 stars,
from
which two new debris disks were imaged for the first time. Our
analysis
of the initial survey gives an empirical estimate for the
detection
rate of debris disks relative to heliocentric distance and
dust
optical depth. Our target list for Cycle 15 is now optimized to
yield
more frequent disk detections. Likewise our observing strategy is
improved
to maximize sensitivity per telescope orbit allocated.
Therefore
we present the most efficient survey possible. The scientific
motivation
is to obtain scattered light images of previously unresolved
debris
disks to determine their viewing geometry and physical
architecture,
both of which may characterize the underlying planetary
system.
We choose 25 debris disk targets for which we predict a
detection
rate of 25% ? 5%. Four targets have extrasolar planets from
which
the viewing geometry revealed by a disk detection will resolve the
v
sin{i} ambiguity in the planet masses. These targets present the
remarkable
opportunity of finally seeing a debris disk in system with
known
planets.
NIC1/NIC2/NIC3
8795
NICMOS Post-SAA calibration - CR Persistence Part 6
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 i
mages.
Each observation will need its own CRMAP, as different SAA
passages
leave different imprints on the NICMOS detectors.
NIC2
10852
Coronagraphic
Polarimetry with NICMOS: Dust grain evolution in T Tauri
stars
The
formation of planetary systems is intimately linked to the dust
population
in circumstellar disks, thus understanding dust grain
evolution
is essential to advancing our understanding of how planets
form.
By combining {1} the coronagraphic polarimetry capabilities of
NICMOS,
{2} powerful 3-D radiative transfer codes, and {3} observations
of
objects known to span the Class II- III stellar evolutionary phases,
we will
gain crucial insight into dust grain growth. By observing
objects
representative of a known evolutionary sequence of YSOs, we will
be
able to investigate how the dust population evolves in size and
distribution
during the crucial transition from a star+disk system to a
system
containing planetesimals. When combine with our previous study on
dust
grain evolution in the Class I-II phase, the proposed study will
help
to establish the fundamental time scales for the depletion of
ISM-like
grains: the first step in understanding the transformation from
small
submicron sized dust grains, to large millimeter sized grains, and
untimely
to planetary bodies.
NIC3
11195
Morphologies
of the Most Extreme High-Redshift Mid-IR-luminous Galaxies
II:
The `Bump' Sources
The
formative phase of some of the most massive galaxies may be
extremely
luminous, characterized by intense star- and AGN-formation.
Till
now, few such galaxies have been unambiguously identified at high
redshift,
and thus far we have been restricted to studying the
low-redshift
ultraluminous infrared galaxies as possible analogs. We
have
recently discovered a sample of objects which may indeed represent
this
early phase in galaxy formation, and are undertaking an extensive
multiwavelength
study of this population. These objects are optically
extremely
faint {R>26} but nevertheless bright at mid-infrared
wavelengths
{F[24um] > 0.5 mJy}. Mid-infrared spectroscopy with
Spitzer/IRS
reveals that they have redshifts z~2, implying luminosities
~1E13
Lsun. Their mid-IR SEDs fall into two broad, perhaps overlapping,
categories.
Sources with brighter F[24um] exhibit power-law SEDs and SiO
absorption
features in their mid-IR spectra characteristic of AGN,
whereas
those with fainter F[24um] show a "bump" characteristic of the
redshifted
1.6um peak from a stellar population, and PAH emission
characteristic
of starformation. We have begun obtaining HST images of
the
brighter sources in Cycle 15 to obtain identifications and determine
kpc-scale
morphologies for these galaxies. Here, we aim to target the
second
class {the "bump" sources} with the goal of determining if these
constitute
morphologically different objects, or simply a "low-AGN"
state
of the brighter class. The proposed observations will help us
determine
whether these objects are merging systems, massive obscured
starbursts
{with obscuration on kpc scales!} or very reddened {locally
obscured}
AGN hosted by intrinsically low-luminosity galaxies.
S/C
11163
Accreting
Pulsating White Dwarfs in Cataclysmic Variables
Recent
ground-based observations have increased the number of known
pulsating
white dwarfs in close binaries with active mass transfer
{cataclysmic
variables} from 5 to 11 systems. Our past Cycles 8 and 11
STIS
observations of the first 2 known, followed by our Cycle 13 SBC
observations
of the next 3 discovered, revealed the clear presence of
the
white dwarf and increased amplitude of the pulsations in the UV
compared
to the optical. The temperatures derived from the UV spectra
show
4 systems are much hotter than non-interacting pulsating white
dwarfs.
A larger sample is needed to sort out the nature of the
instability
strip in accreting pulsators i.e. whether effects of
composition
and rotation due to accretion result in a well- defined
instability
strip as a function of Teff.
WFPC2
11156
Monitoring
Active Atmospheres on Uranus and Neptune
We
propose Snapshot observations of Uranus and Neptune to monitor
changes
in their atmospheres on time scales of weeks and months. Uranus
equinox
is only months away, in December 2007. Hubble Space Telescope
observations
during the past several years {Hammel et al. 2005, Icarus
175,
284 and references therein} have revealed strongly wavelength-
dependent
latitudinal structure, the presence of numerous
visible-wavelength
cloud features in the northern hemisphere, at least
one
very long-lived discrete cloud in the southern hemisphere, and in
2006
the first dark spot ever seen on Uranus. Long-term ground-based
observations
{Lockwood and Jerzekiewicz, 2006, Icarus 180, 442; Hammel
and
Lockwood 2007, Icarus 186, 291} reveal seasonal brightness changes
whose
origins are not well understood. Recent near-IR images of
obtained
using adaptive optics on the Keck Telescope, together with HST
observations
{Sromovsky et al. 2003, Icarus 163, 256 and references
therein}
which include previous Snapshot programs {GO 8634, 10170,
10534}
show a general increase in activity at south temperate latitudes
until
2004, when
Further
Snapshot observations of these two dynamic planets will
elucidate
the nature of long-term changes in their zonal atmospheric
bands
and clarify the processes of formation, evolution, and dissipation
of
discrete albedo features.
WFPC2
11169
Collisions
in the Kuiper belt
For
most of the 15 year history of observations of Kuiper belt objects,
it
has been speculated that impacts must have played a major role in
shaping
the physical and chemical characteristics of these objects, yet
little
direct evidence of the effects of such impacts has been seen. The
past
18 months, however, have seen an explosion of major new discoveries
giving
some of the first insights into the influence of this critical
process.
From a diversity of observations we have been led to the
hypotheses
that: {1} satellite-forming impacts must have been common in
the
Kuiper belt; {2} such impacts led to significant chemical
modification;
and {3} the outcomes of these impacts are sufficiently
predictable
that we can now find and study these impact-derived systems
by
the chemical and physical attributes of both the satellites and the
primaries.
If our picture is correct, we now have in hand for the first
time
a set of incredibly powerful tools to study the frequency and
outcome
of collisions in the outer solar system. Here we propose three
linked
projects that would answer questions critical to the multiple
prongs
of our hypothesis. In these projects we will study the chemical
effects
of collisions through spectrophotometric observations of
collisionally
formed satellites and through the search for additional
satellites
around primaries with potential impact signatures, and we
will
study the physical effects of impacts through the examination of
tidal
evolution in proposed impact systems. The intensive HST program
that
we propose here will allow us to fully test our new hypotheses and
will
provide the ability to obtain the first extensive insights into
outer
solar system impact processes.
WFPC2
11216
HST
/ Chandra Monitoring of a Dramatic Flare in the M87 Jet
As
the nearest galaxy with an optical jet, M87 affords an unparalleled
opportunity
to study extragalactic jet phenomena at the highest
resolution.
During 2002, HST and Chandra monitoring of the M87 jet
detected
a dramatic flare in knot HST-1 located ~1" from the nucleus.
Its
optical brightness eventually increased seventy-fold and peaked in
2005;
the X-rays show a similarly dramatic outburst. In both bands HST-1
is
still extremely bright and greatly outshines the galaxy nucleus. To
our
knowledge this is the first incidence of an optical or X-ray
outburst
from a jet region which is spatially distinct from the core
source
-- this presents an unprecedented opportunity to study the
processes
responsible for non-thermal variability and the X-ray
emission.
We propose five epochs of HST/WFPC2 flux monitoring during
Cycle
16, as well as seven epochs of Chandra/ACIS observation {5ksec
each,
six Chandra epochs contemporary with HST}. At two of the HST/WFPC2
epochs
we also gather spectral information, and at one epoch we will map
the
magnetic field structure. The results of this investigation are of
key
importance not only for understanding the nature of the X-ray
emission
of the M87 jet, but also for understanding flares in blazar
jets,
which are highly variable, but where we have never before been
able
to resolve the flaring region in the optical or X-rays. These new
observations
will allow us to track the decay phase of the giant flare,
and
study smaller secondary flares such as seen late in 2006. Ultimately
we
will test synchrotron emission models for the X-ray outburst,
constrain
particle acceleration and loss timescales, and study the jet
dynamics
associated with this flaring component.
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:
18232-0 – Clear ACS SBC Event Flag #2 for OBS #11163 @ 128/2049z
COMPLETED
OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSacq
07
07
FGS
REacq
06
06
OBAD
with Maneuver 26
26
SIGNIFICANT
EVENTS: (None)