HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science
DAILY REPORT # 3787
PERIOD COVERED: DOY 031
OBSERVATIONS SCHEDULED
ACS/HRC 10182
Towards a Comprehensive Understanding of Type Ia Supernovae: The
Necessity of UV Observations
Type Ia supernovae {SNe Ia} are very important to many diverse areas
of astrophysics, from the chemical evolution of galaxies to
observational cosmology which led to the discovery of dark energy and
the accelerating Universe. However, the utility of SNe Ia as
cosmological probes depends on the degree of our understanding of SN
Ia physics, and various systematic effects such as cosmic chemical
evolution. At present, the progenitors of SNe Ia and the exact
explosion mechanisms are still poorly understood, as are evolutionary
effects on SN Ia peak luminosities. Since early-time UV spectra and
light curves of nearby SNe Ia can directly address these questions, we
propose an approach consisting of two observational components: {1}
Detailed studies of two very bright, young, nearby SNe Ia with HST UV
spectroscopy at 13 epochs within the first 1.5 months after discovery;
and {2} studies of correlations with luminosity for five somewhat more
distant Hubble-flow SNe Ia, for which relative luminosities can be
determined with precision, using 8 epochs of HST UV spectroscopy
and/or broad-band imaging. The HST data, along with extensive
ground-based optical to near-IR observations, will be analyzed with
state-of-the-art models to probe SN Ia explosion physics and constrain
the nature of the progenitors. The results will form the basis for the
next phase of precision cosmology measurements using SNe Ia, allowing
us to more fully capitalize on the substantial past {and future}
investments of time made with HST in observations of high-redshift SNe
Ia.
ACS/HRC 10377
ACS Earth Flats
High signal sky flats will be obtained by observing the bright Earth
with the HRC and WFC. These observations will be used to verify the
accuracy of the flats currently used by the pipeline and will provide
a comparison with flats derived via other techniques: L- flats from
stellar observations, sky flats from stacked GO observations, and
internal flats using the calibration lamps. Weekly coronagraphic
monitoring is required to assess the changing position of the spots.
ACS/HRC/WFC 10367
ACS CCDs daily monitor- cycle 13 - part 1
This program consists of a set of basic tests to monitor, the read
noise, the development of hot pixels and test for any source of noise
in ACS CCD detectors. The files, biases and dark will be used to
create reference files for science calibration. This programme will be
for the entire lifetime of ACS.
ACS/WFC 10378
ACS Polarimetry Calibration
Observations are made of the Boomerang Nebula {highly polarized
reflection nebula} to calibrate the ACS polarizers.
FGS 10110
Parallaxes of Extreme Halo Subgiants: Calibrating Globular Cluster
Distances and the Ages of the Oldest Stars
The ages of the oldest stars are a key constraint on the evolution of
our Galaxy, the history of star formation, and cosmological models.
These ages are usually determined from globular clusters. However, it
is alternatively possible to determine ages of extreme Population II
subgiants in the solar neighborhood based on trigonometric parallaxes,
without any recourse to clusters. This approach completely avoids the
vexing issues of cluster distances, reddenings, and chemical
compositions. There are 3 known nearby, extremely metal-deficient Pop
II subgiants with Hipparcos parallax errors of 6- 11% which are
available for such age determinations. At present, based on the latest
isochrones, the derived ages of these stars {HD 84937, HD 132475, and
HD 140283} are all close to 14 Gyr, uncomfortably close to or higher
than current estimates of the age of the universe. However, the errors
in the Hipparcos parallaxes imply uncertainties of at least 2 Gyr in
the ages of the 3 stars. We propose to measure parallaxes of these
three Pop II subgiants using HST's Fine Guidance Sensor 1R. We expect
to reduce the Hipparcos parallax error bars by factors of 5-6,
providing the most stringent test yet of current theoretical stellar
models of Pop II stars and pushing the age uncertainties to below 0.5
Gyr. These data will also provide a major new constraint on the
distance scale of globular clusters, with wide implications for
stellar evolution and the calibration of Pop II standard candles.
FGS 10202
Resolving OB Binaries in the Carina Nebula, Resuming the Survey
In March 2002 we carried out a small, high-angular resolution survey
of some of the brightest OB stars in the Carina Nebula with FGS1r in
an attempt to resolve binary systems which had thus far evaded
detection by other techniques. Of 23 stars observed, 5 new OB binaries
were discovered with component separations ranging from 0.015"
to0.325". This yield over the spatial domain of FGS1r's angular
resolution, coupled with published statistics of the incidence of OB
stars in short-period spectroscopic, and long-period visual binaries
suggests that the fraction of binarity or multiplicity among OB stars
is near unity. Our unexpected resolution of the prototype O2 If* star
HD 93129A as a 55 milli-arcsecond double is a case in point that great
care must be exercised when one attempts to establish the IMF and
upper-mass cuttoff at the high-mass end of the HR diagram. We propose
to resume the survey to observe a larger, statistically meaningful
sample of OB stars to establish a firm assessment of multiplicity at
the high-mass end of the IMF in these clusters. We will also
investigate the single- star/binary-star status of several
astrophysically important, individual stars in order to enable a
better understanding of the evolution of high-mass stars.
NIC2 10176
Coronagraphic Survey for Giant Planets Around Nearby Young Stars
A systematic imaging search for extra-solar Jovian planets is now
possible thanks to recent progress in identifying "young stars near
Earth". For most of the proposed young {<~ 30 Myrs} and nearby {<~ 60
pc} targets, we can detect a few Jupiter-mass planets as close as a
few tens of AUs from the primary stars. This represents the first time
that potential analogs of our solar system - that is planetary systems
with giant planets having semi-major axes comparable to those of the
four giant planets of the Solar System - come within the grasp of
existing instrumentation. Our proposed targets have not been observed
for planets with the Hubble Space Telescope previously. Considering
the very successful earlier NICMOS observations of low mass brown
dwarfs and planetary disks among members of the TW Hydrae Association,
a fair fraction of our targets should also turn out to posses low mass
brown dwarfs, giant planets, or dusty planetary disks because our
targets are similar to {or even better than} the TW Hydrae stars in
terms of youth and proximity to Earth. Should HST time be awarded and
planetary mass candidates be found, proper motion follow-up of
candidate planets will be done with ground-based AOs.
NIC2 10177
Solar Systems In Formation: A NICMOS Coronagraphic Survey of
Protoplanetary and Debris Disks Until recently, despite decades of
concerted effort applied to understanding the formation processes that
gave birth to our solar system, the detailed morphology of
circumstellar material that must eventually form planets has been
virtually impossible to discern. The advent of high contrast,
coronagraphic imaging as implemented with the instruments aboard HST
has dramatically enhanced our understanding of natal planetary system
formation. Even so, only a handful of evolved disks {~ 1 Myr and
older} have been imaged and spatially resolved in light scattered from
their constituent grains. To elucidate the physical processes and
properties in potentially planet-forming circumstellar disks, and to
understand the nature and evolution of their grains, a larger
spatially resolved and photometrically reliable sample of such systems
must be observed. Thus, we propose a highly sensitive circumstellar
disk imaging survey of a well-defined and carefully selected sample of
YSOs {1-10 Myr T Tau and HAeBe stars} and {> app 10 Myr} main sequence
stars, to probe the posited epoch of planetary system formation, and
to provide this critically needed imagery. Our resolved images will
shed light on the spatial distributions of the dust in these thermally
emissive disks. In combination with their long wavelength SEDs the
physical properties of the grains will be discerned, or constrained by
our photometrically accurate surface brightness sensitivity limits for
faint disks which elude detection. Our sample builds on the success of
the exploratory GTO 7233 program, using two-roll per orbit
PSF-subtracted NICMOS coronagraphy to provide the highest detection
sensitivity to the smallest disks around bright stars which can be
imaged with HST. Our sample will discriminate between proposed
evolutionary scenarios while providing a legacy of cataloged
morphologies for interpreting mid- and far-IR SEDs that the recently
launched Spitzer Space Telescope will deliver.
NICMOS 8791
NICMOS Post-SAA calibration - CR Persistence Part 2
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 DARKSs. 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.
WFPC2 10359
WFPC2 CYCLE 13 Standard Darks
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 10363
WFPC2 CYCLE 13 Intflat and Visflat Sweeps and Filter Rotation Anomaly
Monitor
Using intflat observations, this WFPC2 proposal is designed to monitor
the pixel-to-pixel flatfield response and provide a linearity check.
The intflat sequences, to be done once during the year, are similar to
those from the Cycle 12 program 10075. The images will provide a
backup database in the event of complete failure of the visflat lamp
as well as allow monitoring of the gain ratios. The sweep is a
complete set of internal flats, cycling through both shutter blades
and both gains. The linearity test consists of a series of intflats in
F555W, in each gain and each shutter. As in Cycle 12, we plan to
continue to take extra visflat, intflat, and earthflat exposures to
test the repeatability of filter wheel motions.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.) None
COMPLETED OPS REQs: None
OPS NOTES EXECUTED: None
SCHEDULED SUCCESSFUL FAILURE TIMES
FGS Gsacq 11 11
FGS Reacq 05 05
FHST Update 17 17
LOSS of LOCK
SIGNIFICANT EVENTS: None
