Daily Report #4624

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4624

PERIOD COVERED: 5am June 03 - 5am June 04, 2008 (DOY 155/0900z-156/0900z)

OBSERVATIONS SCHEDULED

WFPC2 10583

Resolving the LMC Microlensing Puzzle: Where Are the Lensing Objects ?

We are requesting 32 HST orbits to help ascertain the nature of the
population that gives rise to the observed set of microlensing events
towards the LMC. The SuperMACHO project is an ongoing ground-based survey on
the CTIO 4m that has demonstrated the ability to detect LMC microlensing
events in real-time via frame subtraction. The improvement in angular
resolution and photometric accuracy available from HST will allow us to 1}
confirm that the detected flux excursions arise from LMC source stars rather
than extended objects {such as for background supernovae or AGN}, and 2}
obtain reliable baseline flux measurements for the objects in their unlensed
state. The latter measurement is important to resolve degeneracies between
the event timescale and baseline flux, which will yield a tighter constraint
on the microlensing optical depth.

WFPC2 11024

WFPC2 CYCLE 15 INTERNAL MONITOR

This calibration proposal is the Cycle 15 routine internal monitor for
WFPC2, to be run weekly to monitor the health of the cameras. A variety of
internal exposures are obtained in order to provide a monitor of the
integrity of the CCD camera electronics in both bays {both gain 7 and gain
15 -- to test stability of gains and bias levels}, a test for quantum
efficiency in the CCDs, and a monitor for possible buildup of contaminants
on the CCD windows. These also provide raw data for generating annual
super-bias reference files for the calibration pipeline.

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.

NIC3 11120

A Paschen-Alpha Study of Massive Stars and the ISM in the Galactic Center

The Galactic center (GC) is a unique site for a detailed study of a
multitude of complex astrophysical phenomena, which may be common to nuclear
regions of many galaxies. Observable at resolutions unapproachable in other
galaxies, the GC provides an unparalleled opportunity to improve our
understanding of the interrelationships of massive stars, young stellar
clusters, warm and hot ionized gases, molecular clouds, large scale magnetic
fields, and black holes. We propose the first large-scale hydrogen Paschen
alpha line survey of the GC using NICMOS on the Hubble Space Telescope. This
survey will lead to a high resolution and high sensitivity map of the
Paschen alpha line emission in addition to a map of foreground extinction,
made by comparing Paschen alpha to radio emission. This survey of the inner
75 pc of the Galaxy will provide an unprecedented and complete search for
sites of massive star formation. In particular, we will be able to (1)
uncover the distribution of young massive stars in this region, (2) locate
the surfaces of adjacent molecular clouds, (3) determine important physical
parameters of the ionized gas, (4) identify compact and ultra-compact HII
regions throughout the GC. When combined with existing Chandra and Spitzer
surveys as well as a wealth of other multi-wavelength observations, the
results will allow us to address such questions as where and how massive
stars form, how stellar clusters are disrupted, how massive stars shape and
heat the surrounding medium, and how various phases of this medium are
interspersed.

WFPC2 11070

WFPC2 CYCLE 15 Standard Darks - part II

This dark calibration program obtains dark frames every week in order to
provide data for the ongoing calibration of the CCD dark current rate, and
to monitor and characterize the evolution of hot pixels. Over an extended
period these data will also provide a monitor of radiation damage to the
CCDs.

WFPC2 11222

Direct Detection and Mapping of Star Forming Regions in Nearby, Luminous
Quasars

We propose to carry out narrow-band emission line imaging observations of 8
quasars at z=0.05-0.15 with the WFPC2 ramp filters and with the NICMOS
narrow-band filters. We will obtain images in the [O II], [O III], H-beta,
and Pa-alpha emission line bands to carry out a series of diagnostic tests
aimed at detecting and mapping out star-forming regions in the quasar host
galaxies. This direct detection of star-forming regions will confirm
indirect indications for star formation in quasar host galaxies. It will
provide a crucial test for models of quasar and galaxy evolution, that
predict the co-existence of starbursts and "monsters" and will solve the
puzzle of why different indicators of star formation give contradictory
results. A secondary science goal is to assess suggested correlations
between quasar luminosity and the size of the narrow-line region.

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:

18239-0 - RMGA Power On/Off (06/08) @ 155/1431z

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL

FGS GSacq 08 08
FGS REacq 06 06
OBAD with Maneuver 28 28

SIGNIFICANT EVENTS: (None)