Daily Report #4623

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4623

PERIOD COVERED: 5am June 02 - 5am June 03, 2008 (DOY 154/0900z-155/0900z)

OBSERVATIONS SCHEDULED

FGS 11212

Filling the Period Gap for Massive Binaries

The current census of binaries among the massive O-type stars is seriously
incomplete for systems in the period range from years to millennia because
the radial velocity variations are too small and the angular separations too
close for easy detection. Here we propose to discover binaries in this
observational gap through a Faint Guidance Sensor SNAP survey of relatively
bright targets listed in the Galactic O Star Catalog. Our primary goal is to
determine the binary frequency among those in the cluster/association,
field, and runaway groups. The results will help us assess the role of
binaries in massive star formation and in the processes that lead to the
ejection of massive stars from their natal clusters. The program will also
lead to the identification of new, close binaries that will be targets of
long term spectroscopic and high angular resolution observations to
determine their masses and distances. The results will also be important for
the interpretation of the spectra of suspected and newly identified binary
and multiple systems.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration - CR Persistence Part 5

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 DARKs. 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 images. Each observation will need its own CRMAP, as
different SAA passages leave different imprints on the NICMOS detectors.

NIC2 11123

A NICMOS Survey for Proplyds in the RCW 38 Massive Embedded Cluster

We propose a search for line emission from photoevaporating protoplanetary
disks in the Massive Embedded Cluster RCW 38. These disks would be analogous
to the "proplyds" discovered in the Orion Nebula: disks around young low
mass stars which are being photoionized by a nearby O star. We will search
for these disks in RCW 38 using narrowband imaging in the lines of Paschen
alpha and molecular hydrogen (1-0) S(1) with NICMOS. The RCW 38 region is an
excellent target for determining whether proplyds are observable in large
numbers outside of Orion. It is a young embedded cluster hosting a few
hundred low mass young stars with a large percentage showing infrared excess
indicating the presence of disks. About 100 of these stars are found within
0.1 pc of the central O5 star, and the cluster is located within a cleared
cavity 0.2 pc in size, embedded within a molecular cloud, exposing the
cluster members directly to the UV radiation from the O star. Unlike Orion,
but like many other young clusters, RCW 38 is not seen in visible light, and
infrared imaging is needed. The best line in the infrared for revealing
proplyds is the Paschen alpha line, which is not detectable from the ground.
Only HST is able to perform these observations. From these observations we
will estimate the lifetime of the evaporating disks, and ascertain whether
these disks will survive long enough to form planets.

NIC2 11164

Molecular Hydrogen Disks Around T Tauri Stars

We propose to measure the properties of planetary system-sized disks around
Sun- like, pre-main sequence stars by imaging the inner parts of these disks
for the first time in gaseous emission from their most dominant constituent,
molecular hydrogen gas. Specifically, we will use the F212N filter and
NICMOS to determine the spatial distribution of ro-vibrational H2 emission
from protoplanetary disks around selected classical and weak-lined T Tauri
stars. The target stars are among those detected by members of this team
through high resolution, ground-based infrared spectroscopy. The spectra
reveal H2 emission at the rest velocities of the stars and at positions
spatially coincident with the stars at the spatial resolution of the
spectroscopic data. This imaging experiment, which is impossible to do using
ground- based facilities, is possible using the NICMOS camera aboard the HST
because the point spread function of this system is extremely stable and can
be measured to a very high accuracy. This experiment is an important test of
the interpretation that the 2.122 micron H2 line emission seen toward T
Tauri stars is produced at distances of 10 to 30 AU from the stars, the
region in which giant planets are expected to form around these stars. These
observations will contribute toward developing a better understanding of the
process, likelihood, and timescale for the formation of planets around
Sun-like stars.

WFPC2 11029

WFPC2 CYCLE 15 Intflat Linearity Check and Filter Rotation Anomaly Monitor

Intflat observations will be taken to provide a linearity check: the
linearity test consists of a series of intflats in F555W, in each gain and
each shutter. A combination of intflats, visflats, and earthflats will be
used to check the repeatability of filter wheel motions. {Intflat sequences
tied to decons, visits 1-18 in prop 10363, have been moved to the cycle 15
decon proposal xxxx for easier scheduling.} Note: long-exposure WFPC2
intflats must be scheduled during ACS anneals to prevent stray light from
the WFPC2 lamps from contaminating long ACS external exposures.

WFPC2 11227

The Orbital Period for an Ultraluminous X-ray Source in NGC1313

The ultraluminous X-ray sources {ULXs} are extragalactic point sources with
luminosities that exceed the Eddington luminosity for conventional
stellar-mass black holes by factors of 10 - 100. It has been hotly debated
whether the ULXs are just common stellar-mass black hole sources with beamed
emission or whether they are sub-Eddington sources that are powered by the
long-sought intermediate mass black holes {IMBH}. To firmly decide this
question, one must obtain dynamical mass measurements through photometric
and spectroscopic monitoring of the secondaries of these system. The crucial
first step is to establish the orbital period of a ULX, and arguably the
best way to achieve this goal is by monitoring its ellipsoidal light curve.
The extreme ULX NGC1313 X-2 provides an outstanding target for an orbital
period determination because its relatively bright optical counterpart {V =
23.5} showed a 15% variation between two HST observations separated by three
months. This level of variability is consistent with that expected for a
tidally distorted secondary star. Here we propose a set of 20 imaging
observations with HST/WFPC2 to define the orbital period. This would be the
first photometric measurement of the orbital period of a ULX binary.
Subsequently, we will propose to obtain spectroscopic observations to obtain
its radial velocity amplitude and thereby a dynamical estimate of its mass.

WFPC2 11337

Investigating the X-ray Variability of Cassiopeia A

We propose a 50 ksec ACIS-S observation of Cas A to follow X-ray flux
changes associated with ejecta recently encountered by the reverse shock.
This will allow us to investigate Cas A's near-term X-ray evolution and the
fine-scale structure of its SN debris. We also request the Chandra
observation be followed by HST NICMOS & WFPC2 images of four identified
X-ray variable features in the high ionization NIR lines of [Si VI] and [Si
X] and low ionization optical lines of [S II] and [O III]. The proposed
X-ray/optical/NIR observations will yield a multi-wavelength study of the
remnant's advancing reverse shock in an inhomogeneous multi-phase ejecta
medium at resolutions down to a fraction of an arcsecond, providing a
hi-resolution broad temperature study of reverse shock heated SN ejecta.

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 08 08
FGS REacq 02 02
OBAD with Maneuver 20 20

SIGNIFICANT EVENTS: (None)