HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT #4840

PERIOD COVERED: 5am April 23 - 5am April 24, 2009 (DOY

113/0900z-114/0900z)

OBSERVATIONS SCHEDULED

FGS 11788

The Architecture of Exoplanetary Systems

Are all planetary systems coplanar? Concordance cosmogony makes that

prediction. It is, however, a prediction of extrasolar planetary system

architecture as yet untested by direct observation for main sequence

stars other than the Sun. To provide such a test, we propose to carry

out FGS astrometric studies on four stars hosting seven companions. Our

understanding of the planet formation process will grow as we match not

only system architecture, but formed planet mass and true distance from

the primary with host star characteristics for a wide variety of host

stars and exoplanet masses.

We propose that a series of FGS astrometric observations with

demonstrated 1 millisecond of arc per-observation precision can

establish the degree of coplanarity and component true masses for four

extrasolar systems: HD 202206 (brown dwarf+planet); HD 128311

(planet+planet), HD 160691 = mu Arae (planet+planet), and HD 222404AB =

gamma Cephei (planet+star). In each case the companion is identified as

such by assuming that the minimum mass is the actual mass. For the last

target, a known stellar binary system, the companion orbit is stable

only if coplanar with the AB binary orbit.

FGS 11943

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 11113

Binaries in the Kuiper Belt: Probes of Solar System Formation and

Evolution

The discovery of binaries in the Kuiper Belt and related small body

populations is powering a revolutionary step forward in the study of

this remote region. Three quarters of the known binaries in the Kuiper

Belt have been discovered with HST, most by our snapshot surveys. The

statistics derived from this work are beginning to yield surprising and

unexpected results. We have found a strong concentration of binaries

among low-inclination Classicals, a possible size cutoff to binaries

among the Centaurs, an apparent preference for nearly equal mass

binaries, and a strong increase in the number of binaries at small

separations. We propose to continue this successful program in Cycle 16;

we expect to discover at least 13 new binary systems, targeted to

subgroups where these discoveries can have the greatest impact.

WFPC2 11316

HST Cycle 16 & Pre-SM4 Optical Monitor

This is a continuation of the Cycle 15 & pre-SM4 Optical Monitor, 11020.

Please see that proposal for a more complete description of the

observing strategy. The 6 visits comprising this proposal observe two

single standard stars with WFPC2/PC in order to establish overall OTA

focal length for the purposes of focus maintenance. The goal of this

monitoring before SM4 is to establish a best estimate of the OTA focus

entering SMOV.

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 11987

The Recent Star Formation History of SINGS Galaxies

The Spitzer Legacy project SINGS provided a unique view of the current

state of star formation and dust in a sample of galaxies of all Hubble

types. This multi-wavelength view allowed the team to create current

star formation diagnostics that are independent of the dust content and

increased our understanding of the dust in galaxies. Even so, using the

SINGS data alone we can only make rough estimates of the recent star

formation history of these galaxies. The lack of U-band observations

means that it is impossible to estimate the ages of young clusters. In

addition, the low resolution of the Spitzer and ground-based

observations means that what appear to be individual Spitzer sources can

actually be composed of many individual clusters with varying ages. In

this proposal we plan to address this missing area in SINGS by obtaining

high-resolution WFPC2 UBVI observations to accurately find and determine

the ages of the young stellar clusters in a subset of the SINGS

galaxies. These observations will greatly enhance the legacy value of

the SINGS observations while also directly answering questions

pertaining to star formation in galaxies.