Press Release

NASA Hubble Space Telescope Daily Report #4845

By SpaceRef Editor
May 4, 2009
Filed under , ,

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science


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


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.

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).


Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be

HSTARS: (None)




FGS GSAcq 09 09
FGS REAcq 03 03
OBAD with Maneuver 24 24


SpaceRef staff editor.