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)