HUBBLE SPACE TELESCOPE - Continuing to collect World Class
Science
DAILY REPORT #4843
PERIOD COVERED: 5am April 28 - 5am April 29, 2009 (DOY
118/0900z-119/0900z)
OBSERVATIONS SCHEDULED
FGS 11944
Binaries at the Extremes of the H-R Diagram
We propose to use HST/Fine Guidance Sensor 1r to survey
for binaries
among some of the most massive, least massive, and oldest
stars in our
part of the Galaxy. FGS allows us to spatially resolve
binary systems
that are too faint for ground-based, speckle or optical
long baseline
interferometry, and too close to resolve with AO. We
propose a
SNAP-style program of single orbit FGS TRANS mode
observations of very
massive stars in the cluster NGC 3603, luminous blue
variables, nearby
low mass main sequence stars, cool subdwarf stars, and
white dwarfs.
These observations will help us to (1) identify systems
suitable for
follow up studies for mass determination, (2) study the
role of binaries
in stellar birth and in advanced evolutionary states, (3)
explore the
fundamental properties of stars near the main
sequence-brown dwarf
boundary, (4) understand the role of binaries for X-ray
bright systems,
(5) find binaries among ancient and nearby subdwarf stars,
and (6) help
calibrate the white dwarf mass - radius relation.
WFPC2 11612
Eta Carinae's Continuing Instability and Recovery - the
2009 Event
Eta Carinae is the only really observable example of
structural recovery
from a massive giant eruption, a "supernova imposter'
event. Moreover it
is the only well-observed star above 100 Msun, and its
5.5-year-recurrent spectroscopic events provide
extraordinary clues to
its surface instability. This truly unique combination of
attributes
makes it valuable for understanding the most massive
stars. A fresh
development arose a few years ago: The star has brightened
much faster
than before, and appears to have entered a rapid stage in
its
post-eruption recovery.
A spectroscopic event will occur at 2009.0, soon after the
planned HST
servicing mission. Because of the recent secular trend,
this event is
expected to differ from its well-observed 2003.5
predecessor. The
differences will be very important, because they offer
clues to
very-massive-star structural instabilities that can't be
observed in any
other known way.
Some of the needed observations require HST's high spatial
resolution
and UV coverage. We propose an efficient, well-chosen set
of STIS and
ACS observations around the critical time. If the
servicing mission is
too late for the event, then a subset of the observations
will still be
merited.
WFPC2 11979
WFPC2 Imaging of Fomalhaut b: Determining its Orbit and
Testing for
H-alpha Emission
Fomalhaut is a bright nearby star that harbors a belt of
dusty material
with a morphology that has been used to predict the
presence of a
shepherding planet. With ACS/HRC coronagraphy, we have
achieved the
direct detection of a planet candidate (Fomalhaut b) in
F606W and F814W.
The planet candidate lies 18 AU interior to the dust belt
and we detect
counterclockwise orbital motion in two epochs of
observations (2004 and
2006). Fomalhaut b has mass no greater than three Jupiter
masses based
on an analysis of its luminosity, including non-detections
at infrared
wavelengths, and the dynamical argument that a
significantly more
massive object would disrupt the dust belt. Variability at
optical
wavelengths and the brightness in the F606W passband
suggest additional
sources of luminosity such as starlight reflected from a
circumplanetary
ring system. A second possibility that has been invoked
for substellar
objects is a significant contribution of H-alpha emission.
Here we
propose follow-up WFPC2 observations to test the
possibility that the
F606W flux is contaminated by H-alpha emission. We
demonstrate that the
detection of Fomalhaut b using WFPC2 is feasible using
roll
deconvolution. Furthermore, a detection of Fomalhaut b in
2009 will
provide a crucial third epoch for astrometry. With the
existing two
epochs of data, the orbit of Fomalhaut b cannot be
determined uniquely.
The third epoch will be used to test the prediction of
apsidal alignment
and more accurately determine the dynamical mass of
Fomalhaut b. If
apsidal mis-alignment is found between the planet and the
belt, this
result would point to the existence of still other planets
lurking
unseen in the Fomalhaut system.
WFPC2 11983
An Imaging Survey of Protoplanetary Disks and Brown Dwarfs
in the
Chamaeleon I Region
We propose to carry out a HST/WFPC2 survey of young brown
dwarfs, Class
I and Class II sources in the Chamaelon I region, one of
the
best-studied star-forming regions, in order to investigate
the link
between disk evolution and the formation of
substellar-mass objects. We
will use deep broad-band imaging in the I and z-equivalent
HST bands to
unveil the unknown population of substellar binary
companions, down to a
few Jupiter masses for separations of a few tens of AU. We
will also
perform narrow-band imaging to directly detect accreting
circumstellar
disks and jets around brown dwarfs, Class-I and class-II
objects.
Chamaelon I is nearly coeaval of Orion (~1-2Myr) but at
~1/3 its
distance, allowing 3x higher resolution and 10x more flux
for comparable
objects. Unlike Orion, low-mass objects and protoplanetary
disks in
Chamaeleon I have been extensively studied with Spitzer,
but not yet
with the HST. The Chamaeleon I region is an ideal HST
target, as it lies
in the CVZ of the HST and therefore it is easily
accessible any time of
the year with long orbits.
WFPC2 11988
Searching for Intermediate Mass Black Holes in Globular
Clusters via
Proper Motions
The unambiguous detection of an intermediate mas black
hole (IMBH) in a
globular star cluster would be a major achievement for the
Hubble Space
Telescope. It is critical to know whether or not IMBHs
exist in the
centers of clusters in order to understand the dynamical
evolution of
dense stellar systems. Also, n IMBH detection would prove
the existence
of BHs in an entirely new mass range. Observationally, the
search has
been hampered by the low number of stars with known
velocities in the
central few arcseconds. This limits measurements of the
stellar velocity
dispersion in the region where the gravitational influence
of any IMBH
would be felt. Existing IMBH claims in the literature have
all been
called into question, and have all been based on
line-of-sight
velocities from spectroscopy. In cycle 13, we obtained
ACS/HRC
observations for 5 nearby Galactic globular clusters for a
new proper
motion study. Here, we request WFPC2/PC observations of
these clusters,
all of which are observable in Feb-May 2009. This 4 year
baseline will
allow us to measure the proper motions of stars into the
very center of
each cluster, and either detect or place firm constraints
on the
presence of an IMBH. In addition, we will determine
whether or not the
clusters rotate or show any anisotropy in their motions.
Our small (<75
orbit) program meets the criteria of addressing high
impact science
(IMBH detection) using innovative methods (proper
motions).
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are
preliminary reports
of potential non-nominal performance that will be
investigated.)
HSTARS:
11785 - GSAcq(2,3,2) scheduled from 119/05:03:25 -
05:11:30, failed to
RGA Hold due to Search Radius Limit Exceeded on FGS-2.
Observations Affected: Astrometry, Proposal ID# 11944
COMPLETED OPS REQUEST:
18420-0 - Disable SIC&DH Redundant Tray Heaters @
118/20:13z
18421-0 - Reconfigure SIC&DH to Reply Bus B @
118/20:15z
COMPLETED OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSAcq
09
08
FGS
REAcq
04
04
OBAD with Maneuver
26
25
SIGNIFICANT EVENTS:
Flash Report: SIC&DH Reconfiguration - Redundant
Heater Disable & Reply
Bus B
At 118/20:13:34 UTC, Ops Request 18420-0 was successfully
completed, disabling the SIC&DH redundant tray
heaters. Immediately
following, at 118:20:15:07 UTC, Ops Request 18421-0 was
also
successfully completed, reconfiguring the SIC&DH
Multiplexed Data Bus
(MDB) to operations on Reply Bus B.