HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT      #4845

PERIOD COVERED: 5am April 30 - 5am May 01, 2009 (DOY

                          120/0900z-121/0900z)

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 to observe using 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/ACS/SBC 11975

UV Light from Old Stellar Populations: a Census of UV Sources in

Galactic Globular Clusters

In spite of the fact that HST has been the only operative

high-resolution eye in the UV-window over the last 18 years, no

homogeneous UV survey of Galactic globular clusters (GGCs) has been

performed to date. In order to fill this gap in the stellar population

studies, we propose a program that exploits the unique capability of the

WFPC2 and the SBC in the far-/mid- UV for securing deep UV imaging of 46

GGCs. The proposed observations will allow to study with unprecedented

accuracy the hottest GGC stars, comprising the extreme horizontal branch

(HB) stars and their progeny (the so-called AGB-manque', and Post-early

AGB stars), and "exotic stellar populations" like the blue straggler

stars and the interacting binaries. The targets have been selected to

properly sample the GGC metallicity/structural parameter space, thus to

unveil any possible correlation between the properties of the hot

stellar populations and the cluster characteristics. In addition, most

of the targets have extended HB "blue tails", that can be properly

studied only by means of deep UV observations, especially in the far-UV

filters like the F160BW, that is not foreseen on the WFC3. This data

base is complemented with GALEX observations in the cluster outermost

regions, thus allowing to investigate any possible trend of the

UV-bright stellar types over the entire radial extension of the

clusters. Although the hottest GGC stars are just a small class of

"special" objects, their study has a broad relevance in the context of

structure formation and chemical evolution in the early Universe,

bringing precious information on the basic star formation processes and

the origin of blue light from galaxies. Indeed, the proposed

observations will provide the community with an unprecedented data set

suitable for addressing a number of still open astrophysical questions,

ranging from the main drivers of the HB morphology and the mass loss

processes, to the origin of the UV upturn in elliptical galaxies, the

dating of distant systems from integrated light, and the complex

interplay between stellar evolution and dynamics in dense stellar

aggregates. In the spirit of constructing a community resource, we

entirely waive the proprietary period for these observations.

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: (None)

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

                       SCHEDULED      SUCCESSFUL

FGS GSAcq               09                 09               

FGS REAcq               03                 03                            

OBAD with Maneuver 24                 24                                

SIGNIFICANT EVENTS: (None)