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Daily Report # 4358



 
 
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Old May 9th 07, 04:07 PM posted to sci.astro.hubble
Cooper, Joe
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Default Daily Report # 4358

Notice: For the foreseeable future, the daily reports may contain apparent
discrepancies between some proposal descriptions and the listed instrument
usage. This is due to the conversion of previously approved ACS WFC or HRC
observations into WFPC2, or NICMOS observations subsequent to the loss of
ACS CCD science capability in late January.


HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4358

PERIOD COVERED: UT May 08, 2007 (DOY 128)

OBSERVATIONS SCHEDULED

WFPC2 10800

Kuiper Belt Binaries: Probes of Early Solar System Evolution

Binaries in the Kuiper Belt are a scientific windfall: in them we have
relatively fragile test particles which can be used as tracers of the early
dynamical evolution of the outer Solar System. We propose to continue a
Snapshot program using the ACS/HRC that has a demonstrated discovery
potential an order of magnitude higher than the HST observations that have
already discovered the majority of known transneptunian binaries. With this
continuation we seek to reach the original goals of this project: to
accumulate a sufficiently large sample in each of the distinct populations
collected in the Kuiper Belt to be able to measure, with statistical
significance, how the fraction of binaries varies as a function of their
particular dynamical paths into the Kuiper Belt. Today's Kuiper Belt bears
the imprints of the final stages of giant-planet building and migration;
binaries may offer some of the best preserved evidence of that long-ago era.

WFPC2 10832

Solving the microlensing puzzle: An HST high-resolution imaging approach

We propose to use the HST Advanced Camera for Surveys High Resolution
Channel to obtain high resolution imaging data for 10 bona-fide LMC
microlensing events seen in the original MACHO survey. The purpose of this
survey will be to assess whether or not the lens and source stars have
separated enough to be resolved since the original microlensing event took
place - about a decade has passed since the original MACHO survey and the
HST WFPC2 follow-up observations of the microlensing events. If the
components of the lensing event are resolved, we will determine the apparent
magnitude and color of both the lens and the source stars. These data, in
combination with Spitzer/IRAC data and Magellan near-IR JHK data, will be
used to ascertain the basic properties of the lens stars. With the majority
of the microlensing events in the original MACHO survey observed at the
highest spatial resolution currently possible, we will be able to draw
important conclusions as to what fraction of these events have lenses which
belong to some population of dwarf stars in the disk and what fraction must
be due to lenses in the halo or beyond. These data will greatly increase our
understanding of the structure of the Galaxy by characterizing the stellar
population responsible for the gravitational microlensing.

WFPC2 10788

Probing the Central Dark Mass Concentration of the Collapsed-Core Globular
Cluster M15

We plan to probe the central dark mass concentration in the collapsed-core
globular cluster M15 by analyzing the structure of its central stellar cusp
with the highest possible angular resolution. The rapid rise of M/L toward
the center of M15 can be alternatively explained by a central concentration
of several thousand compact remnants {heavy white dwarfs and neutron stars}
or instead by the presence of an intermediate-mass black hole {IMBH} of a
few thousand solar masses. We propose to obtain one orbit of highly dithered
WFPC2 F555W {V} imaging to supplement the available ACS/HRC F435W {B}
imaging from GO-10401. This will allow us {1} to improve the constraints on
the radius of the as yet unresolved core and {2} to investigate the relation
between cusp slope and stellar mass, the form of which depends on the size
and mix of the remnant population and on whether or not an IMBH is present.
We will compare the central cusp structure with predictions from both
Fokker-Planck and GRAPE-6 N-body models, with and without IMBHs, to
constrain the nature of the intriguing dark mass concentration.

WFPC2 10791

Proper motion may nail counterpart of unique X-ray pulsar

1E 1207.4-5209 is one of the most puzzling X-ray compact sources in the
Galaxy. Long known to be a radio-quiet Neutron Star {NS} embedded in a young
{~7000 y} supernova remnant, it displays a unique phenomenology, including
multiple cyclotron absorption features in its thermal X-ray spectrum, as
well as a possible non-monotonous evolution of its 424 ms rotational period.
A candidate optical counterpart {I~23.4} with very red colours {not
consistent with the expected emission of a NS, but rather with a low-mass
stellar companion, or a fossil disk} was singled out with HST/ACS in 2003,
at the margin of the Chandra error box. In order to test the reality of such
an association, we propose to take advantage of the high space velocities
characteristics of NSs to search for the expected displacement {~150 mas in
the NE direction} of the candidate counterpart over a 3 years time span. One
orbit observation, either unveiling the displacement or ruling it out, will
settle the problem of the optical identification of 1E1207.4-5209. We stress
that a null result would also be important for the understanding of this
source.

WFPC2 10823

The spectrum of a magnetar in the blue and ultraviolet.

Magnetars are natural laboratories for investigating the behaviour of matter
at the very extremes of nature. The magnetar CXOU J010043.1-721134 was
serendipitously discovered by WFPC2 imaging of the SMC. Because of the low
reddening to this source compared to the other magnetars, this is a unique
opportunity to measure the spectral shape in the blue and ultraviolet. We
hope also to establish the feasibility of spectroscopic follow-up. We are
asking for two orbits of ACS imaging.

WFPC2 10903

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

We are requesting 12 HST orbits to continue to investigate the nature of the
population that gives rise to the microlensing seen towards the LMC. This
proposal builds on the cycle 14 HST program {10583} and will complement the
study with 12 yet-to-be discovered microlensing candidates from Fall 2006.
Our SuperMacho project is an ongoing ground- based survey on the CTIO 4m
that has demonstrated the ability to detect LMC microlensing events via
frame subtraction. The combination of high angular resolution and
photometric accuracy with HST will allow us to 1} confrim that the detected
flux excursions arise from LMC stars, rather than background supernovae or
AGN, and 2} obtain reliable baseline flux measurements for the objects in
their unlensed state. This latter measurement in important in determining
the microlensing optical depth towards the LMC.

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 05 05
FGS REacq 08 08
OBAD with Maneuver 26 26

SIGNIFICANT EVENTS:

Evaluation of Universal Kalman Filter performance continued. Details follow.

Background Kalman Filter Operation Flash Report for day 127

The KF was halted at 127/18:15. The filter was restarted at 127/18:18 with
the CSS disabled, the Gyro2 input enabled, during orbit day, during a
vehicle slew and during an M2G guiding interval and during a slow changing
B-field. All UKF parameters showed nominal operation. The test was an
MSS/Gyro2 Initialization test case during a vehicle slew with a slow
changing B-field (M_G2_IVS, Test #35).

The KF was reconfigured and restarted at 127/19:14 with the CSS and both
gyro inputs disabled to leave the filter in an MSS only configuration. This
configuration is to help provide a earlier baseline set of data for PCS
analysis and it will remain the default configuration outside of other KF
convergence testing for the remainder of the week.
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