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 # 4341
PERIOD COVERED: UT April 13,14,15, 2007 (DOY 103,104,105)
OBSERVATIONS SCHEDULED
NIC1/NIC2/NIC3 8795
NICMOS Post-SAA calibration - CR Persistence Part 6
A new proceedure proposed to alleviate the CR-persistence
problem of
NICMOS. Dark frames will be obtained immediately upon
exiting the SAA
contour 23, and everytime 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 i
mages. Each observation will need its own CRMAP, as
different SAA
passages leave different imprints on the NICMOS detectors.
WFPC2 11085
Europa in Eclipse: Tenuous Atmosphere, Electromagnetic
Activity and
Surface Luminescence HST Proposal 11085 We propose to
image Europa
during its orbital eclipse by Jupiter. This will form the
basis of an
investigation into the nature of the tenuous atmosphere,
electromagnetic
environment and surface material of Europa. We will
compare the FUV
oxygen line at 1356A to the optical line at 6300A and seek
optical
auroral hydrogen emission in Halpha. With broad continuum
filters, we
will search for optical emissions from other atmospheric
constituents
and for fluorescence of the surface material, arising from
the very high
level of incident energetic particle radiation. The high
spatial
resolution of ACS will allow us to fully resolve scales of
interest and
allow us to distinguish easily the different terrains on
Europa's
surface. In particular we wish to compare luminesence in
regions
dominated by ice to those of potentially organic red
material.
WFPC2 11083
The Structure, Formation and Evolution of Galactic Cores
and Nuclei
A surprising result has emerged from the ACS Virgo Cluster
Survey
{ACSVCS}, a program to obtain ACS/WFC gz imaging for a
large, unbiased
sample of 100 early-type galaxies in the Virgo Cluster. On
subarcsecond
scales {i.e., <0.1"-1"}, the HST brightness
profiles vary systematically
from the brightest giants {which have nearly constant
surface brightness
cores} to the faintest dwarfs {which have compact stellar
nuclei}.
Remarkably, the fraction of galaxy mass contributed by the
nuclei in the
faint galaxies is identical to that contributed by
supermassive black
holes in the bright galaxies {0.2%}. These findings
strongly suggest
that a single mechanism is responsible for both types of
Central Massive
Object: most likely internally or externally modulated gas
inflows that
feed central black holes or lead to the formation of
"nuclear star
clusters". Understanding the history of gas
accretion, star formation
and chemical enrichment on subarcsecond scales has thus
emerged as the
single most pressing question in the study of nearby
galactic nuclei,
either active or quiescent. We propose an ambitious HST
program {199
orbits} that constitutes the next, obvious step forward:
high-resolution, ultraviolet {WFPC2/F255W} and infrared
{NIC1/F160W}
imaging for the complete ACSVCS sample. By capitalizing on
HST's unique
ability to provide high-resolution images with a sharp and
stable PSF at
UV and IR wavelengths, we will leverage the existing
optical HST data to
obtain the most complete picture currently possible for
the history of
star formation and chemical enrichment on these small
scales. Equally
important, this program will lead to a significant
improvement in the
measured structural parameters and density distributions
for the stellar
nuclei and the underlying galaxies, and provide a
sensitive measure of
"frosting" by young stars in the galaxy cores.
By virtue of its superb
image quality and stable PSF, NICMOS is the sole
instrument capable of
the IR observations proposed here. In the case of the
WFPC2
observations, high-resolution UV imaging {< 0.1"}
is a capability unique
to HST, yet one that could be lost at any any time.
NIC3 11082
NICMOS Imaging of GOODS: Probing the Evolution of the
Earliest Massive
Galaxies, Galaxies Beyond Reionization, and the High
Redshift Obscured
Universe
Deep near-infrared imaging provides the only avenue
towards
understanding a host of astrophysical problems, including:
finding
galaxies and AGN at z > 7, the evolution of the most
massive galaxies,
the triggering of star formation in dusty galaxies, and
revealing
properties of obscured AGN. As such, we propose to observe
60 selected
areas of the GOODS North and South fields with NICMOS
Camera 3 in the
F160W band pointed at known massive M > 10^11 M_0 galaxies
at z > 2
discovered through deep Spitzer imaging. The depth we will
reach {26.5
AB at 5 sigma} in H_160 allows us to study the internal
properties of
these galaxies, including their sizes and morphologies,
and to
understand how scaling relations such as the Kormendy
relationship
evolved. Although NIC3 is out of focus and undersampled,
it is currently
our best opportunity to study these galaxies, while also
sampling enough
area to perform a general NIR survey 1/3 the size of an
ACS GOODS field.
These data will be a significant resource, invaluable for
many other
science goals, including discovering high redshift
galaxies at z > 7,
the evolution of galaxies onto the Hubble sequence, as
well as examining
obscured AGN and dusty star formation at z > 1.5. The
GOODS fields are
the natural location for HST to perform a deep NICMOS
imaging program,
as extensive data from space and ground based
observatories such as
Chandra, GALEX, Spitzer, NOAO, Keck, Subaru, VLT, JCMT,
and the VLA are
currently available for these regions. Deep
high-resolution
near-infrared observations are the one missing ingredient
to this
survey, filling in an important gap to create the deepest,
largest, and
most uniform data set for studying the faint and distant
universe. The
importance of these images will increase with time as new
facilities
come on line, most notably WFC3 and ALMA, and for the
planning of future
JWST observations.
ACS/SBC 11074
ACS/SBC Darks in Support of Specific SBC Science
Observations
This program provides SBC DARK visits to be scheduled in
conjuction with
certain specific science observations which require the
SBC to be turned
on in the orbit preceeding the science observation.
NIC1/NIC2/NIC3 11060
NICMOS Photometric Stability Monitoring
This NICMOS calibration proposal carries out photometric
monitoring
observations during Cycle 15. The format is the same as
the Cycle 14
version of the program {10725}, but a few modifications
were made with
respect to the Cycle 12 program 9995 and Cycle 13 program
10381.
Provisions had to be made to adopt to 2-gyro mode {G191B2B
was added as
extra target to provide target visibility through most of
the year}.
Where before 4 or 7 dithers were made in a filter before
we moved to the
next filter, now we observe all filters at one position
before moving to
the next dither position. While the previous method was
chosen to
minimize the effect of persistence, we now realize that
persistence may
be connected to charge trapping and by moving through the
filter such
that the count rate increases, we reach equilibrium more
quickly between
charge being trapped and released. We have also increased
exposure times
where possible to reduce the charge trapping non-
linearity effects.
WFPC2 11031
CTE Background Dependence Closeout
Measuring the charge transfer efficiency {CTE} of an
astronomical CCD
camera is crucial to determining the CCD's photometric
fidelity across
the field of view. WFPC2's CTE has degraded steadily over
the last 13
years because of continuous exposure to trapped particles
in HST's
radiation environment. The fraction of photometric signal
lost from
WFPC2's CTI {charge transfer inefficiency} is a function
of WFPC2's time
in orbit, the integrated signal in the image, the location
of the image
on the CCD, and the background signal. Routine monitoring
of WFPC2's CTE
over the last 13 years permits an assessment of all but
the last
condition. The dependence of CTE on background signal must
be
characterized, however, because a large fraction of WFPC2
images have
been obtained under conditions of significant sky
background. This
program aims to assess the end-of-life CTE of WFPC2's CCDs
separately as
a function of background signal. Traditional images of an
off-center
field in NGC 5139 {Omega Cen} are recorded after
preflashing {or before
postflashing} the CCDs with internal lamps to provide
average background
signals of 0-160 e-, which span the range of sky
backgrounds observed in
~99% of long-exposure narrow- and broad-band WFPC2 images.
ACS/SBC 10907
Testing the first direct measurement of cataclysmic
variable evolution:
the search for a circumbinary disk or a low?mass companion
around NN
Serpentis
We obtained high time-resolution photometry using the high
speed CCD
camera ULTRACAM between 2002 and 2004, which revealed a
gradual
reduction in the orbital period of the pre- cataclysmic
variable NN
Serpentis. There are three possible explanations for this
period change:
firstly, we may have been successful in obtaining the
first and only
direct measurement of the braking rate of a close binary
system, in
which case our measured values are approximately 2 orders
of magnitude
greater than predicted, and pose serious problems for the
theory of
close binary evolution. Secondly, the unusually high
braking rate may be
caused by the presence of a circumbinary disk, which would
help to
answer two of the outstanding problems with current CV
theory - namely
the high mass- transfer rates seen in some CVs, and the
fact that the
minimum observed value in the CV period distribution is
approximately
15% longer than expected. Finally, our observations could
be explained
by a light travel-time effect caused by a third body in
orbit around the
binary, which would raise major questions about the
evolutionary history
of the system, in particular how a third body has managed
to remain in a
stable orbit throughout periods of intense mass-loss in
the central
binary. We intend to use IRAC observations to search for a
mid-infrared
excess in the spectral energy distribution of NN Ser,
which would
confirm the presence of either a disk or a third body. We
then propose
to use HST imaging to attempt to resolve a third body,
allowing us to
discriminate between the two possibilities. If both
methods fail to
reveal any extra system components, we will have ruled out
our only
remaining alternatives to a genuinely high angular
momentum loss rate in
this system, with profound implications for CV evolution.
WFPC2 10890
Morphologies of the Most Extreme High-Redshift
Mid-IR-Luminous Galaxies
The formative phase of the most massive galaxies may be
extremely
luminous, characterized by intense star- and
AGN-formation. Till now,
few such galaxies have been unambiguously identified at
high redshift,
restricting us to the study of low-redshift ultraluminous
infrared
galaxies as possible analogs. We have recently discovered
a sample of
objects which may indeed represent this early phase in
galaxy formation,
and are undertaking an extensive multiwavelength study of
this
population. These objects are bright at mid-IR wavelengths
{F[24um]>0.8mJy}, but deep ground based imaging
suggests extremely faint
{and in some cases extended} optical counterparts
{R~24-27}. Deep K-band
images show barely resolved galaxies. Mid-infrared
spectroscopy with
Spitzer/IRS reveals that they have redshifts z ~ 2-2.5,
suggesting
bolometric luminosities ~10^{13-14}Lsun! We propose to
obtain deep ACS
F814W and NIC2 F160W images of these sources and their
environs in order
to determine kpc-scale morphologies and surface photometry
for these
galaxies. The proposed observations will help us determine
whether these
extreme objects are merging systems, massive obscured
starbursts {with
obscuration on kpc scales!} or very reddened {locally
obscured} AGN
hosted by intrinsically low-luminosity galaxies.
WFPC2 10880
The host galaxies of QSO2s: AGN feeding and evolution at
high
luminosities
Now that the presence of supermassive black holes in the
nuclei of
galaxies is a well established fact, other questions
related to the AGN
phenomena still have to be answered. Problems of
particular interest are
how the AGN gets fed, how the black hole evolves and how
the evolution
of the black hole is related to the evolution of the
galaxy bulge. Here
we propose to address some of these issues using ACS/WFC +
F775W
snapshot images of 73 QSO2s with redshifts in the range
0.3<z<0.4. These
observations will be combined with similar archival data
of QSO1s and
ground based data of Seyfert and normal galaxies. First,
we will
intestigate whether interactions are the most important
feeding
mechanism in high luminosity AGNs. This will be done in a
quantitative
way, comparing the asymmetry indices of QSO2 hosts with
those of lower
luminosity AGNs and normal galaxies. Second, we will do a
detailed study
of the morphology of the host galaxies of both QSO types,
to determine
if they are similar, or if there is an evolutionary trend
from QSO2s to
QSO1s. The results from this project will represent an
important step in
the understanding of AGN evolution, and may also introduce
a substantial
modification to the Unified Model.
WFPC2 10877
A Snapshot Survey of the Sites of Recent, Nearby
Supernovae
During the past few years, robotic {or nearly robotic}
searches for
supernovae {SNe}, most notably our Lick Observatory
Supernova Search
{LOSS}, have found hundreds of SNe, many of them in quite
nearby
galaxies {cz < 4000 km/s}. Most of the objects were
discovered before
maximum brightness, and have follow-up photometry and
spectroscopy; they
include some of the best-studied SNe to date. We propose
to conduct a
snapshot imaging survey of the sites of some of these
nearby objects, to
obtain late-time photometry that {through the shape of the
light and
color curves} will help reveal the origin of their
lingering energy. The
images will also provide high-resolution information on
the local
environments of SNe that are far superior to what we can
procure from
the ground. For example, we will obtain color-color and
color-magnitude
diagrams of stars in these SN sites, to determine the SN
progenitor
masses and constraints on the reddening. Recovery of the
SNe in the new
HST images will also allow us to actually pinpoint their
progenitor
stars in cases where pre- explosion images exist in the
HST archive.
This proposal is an extension of our successful Cycle 13
snapshot survey
with ACS. It is complementary to our Cycle 15 archival
proposal, which
is a continuation of our long-standing program to use
existing HST
images to glean information about SN environments.
WFPC2 10873
The Radio-quiet Jet Flow in Markarian 34
The properties of AGN jet flows are notoriously difficult
to ascertain.
We are currently studying jets in Seyferts by combining
emission-line
diagnostics with radio observations. We have devised a
method of
analysis which -- with only modest and reasonable
assumptions -- leads
to a physical description of the jet flow: its mass,
momentum and energy
flux, along with its density, velocity and Mach number. We
have applied
this method to a rich dataset on Markarian 78 and
discovered that its
jet is very weak, slow, and dense relative to the kind of
jets found in
radio loud AGN {Whittle \& Wilson 2004, Whittle et al
2005, 2006}. Such
a difference between radio quiet and radio loud jet flows
would be a
major result -- if it were found to be generally true. We
have more
modest observations of a further six Seyferts with jets,
but only one of
these -- Mkn 34 -- approaches Mkn 78 as a clean enough
case to allow our
full analysis. Our existing VLA and STIS data are
excellent, but the HST
archive emission-line and continuum images are of poor
quality and low
resolution. We are requesting just 3 orbits to obtain
higher S/N images
at high resolution {ACS/HRC} in [OIII] 5007, [OII] 3727,
green and red
continuum, bringing the total dataset up to a par with
that of Mkn 78.
We will then be able to apply our full analysis to
determine the nature
of the jet flow in this second radio quiet AGN.
ACS/SBC 10872
Lyman Continuum Emission in Galaxies at z=1.2
Lyman continuum photons produced in massive starbursts may
have played a
dominant role in the reionization of the Universe.
Starbursts are
important contributors to the ionizing metagalactic
background at lower
redshifts as well. However, their contribution to the
background depends
upon the fraction of ionizing radiation that escapes from
the intrinsic
opacity of galaxies below the Lyman limit. Current surveys
suggest
escape fractions of a few percent, up to 10%, with very
few detections
{as opposed to upper limits} having been reported. No
detections have
been reported in the epochs between z=0.1 and z=2. We
propose to measure
the fraction of escaping Lyman continuum radiation from 15
luminous
z~1.2 galaxies in the GOODS fields. Using the tremendous
sensitivity of
the ACS Solar- blind Channel, we will reach AB=30 mag.,
allowing us to
detect an escape fraction of 1%. We will correlate the
amount of
escaping radiation with the photometric and morphological
properties of
the galaxies. A non-detection in all sources would imply
that QSOs
provide the overwhelming majority of ionizing radiation at
z=1.3, and it
would strongly indicate that the properties of galaxies at
higher
redshift have to be significantly different for galaxies
to dominate
reionization. The deep FUV images will also be useful for
extending the
FUV study of other galaxies in the GOODS fields.
ACS/SBC 10862
Comprehensive Auroral Imaging of Jupiter and Saturn during
the
International Heliophysical Year
A comprehensive set of observations of the auroral
emissions from
Jupiter and Saturn is proposed for the International
Heliophysical Year
in 2007, a unique period of especially concentrated
measurements of
space physics phenomena throughout the solar system. We
propose to
determine the physical relationship of the various auroral
processes at
Jupiter and Saturn with conditions in the solar wind at
each planet.
This can be accomplished with campaigns of observations,
with a sampling
interval not to exceed one day, covering at least one
solar rotation.
The solar wind plasma density approaching Jupiter will be
measured by
the New Horizons spacecraft, and a separate campaign near
opposition in
May 2007 will determine the effect of large-scale
variations in the
interplanetary magnetic field {IMF} on the Jovian aurora
by
extrapolation from near-Earth solar wind measurements. A
similar Saturn
campaign near opposition in Jan. 2007 will combine
extrapolated solar
wind data with measurements from a wide range of locations
within the
Saturn magnetosphere by Cassini. In the course of making
these
observations, it will be possible to fully map the auroral
footprints of
Io and the other satellites to determine both the local
magnetic field
geometry and the controlling factors in the
electromagnetic interaction
of each satellite with the corotating magnetic field and
plasma density.
Also in the course of making these observations, the
auroral emission
properties will be compared with the properties of the
near-IR
ionospheric emissions {from ground-based observations} and
non thermal
radio emissions, from ground-based observations for
Jupiter?s decametric
radiation and Cassini plasma wave measurements of the
Saturn Kilometric
Radiation {SKR}.
NIC3 10839
The NICMOS Polarimetric Calibration
Recently, it has been shown that NICMOS possesses an
instrumental
polarization at a level of 1.2%. This completely inhibits
the data
reduction in a number of previous GO programs, and hampers
the ability
of the instrument to perform high accuracy polarimetry. In
all, 90
orbits of HST data are affected, with potentially many
more in Cycle 15.
We propose to obtain high signal to noise observations of
three
polarimetric standards at the cardinal roll angles of the
NICMOS
polarizers for both NIC1 and NIC2. These observations are
designed to
fully characterize the instrumental polarization in order
for NICMOS to
reach its full potential by enabling high accuracy
polarimetry of
sources with polarizations around 1%. The residual
polarization will
also be determined as a function of position and spectral
energy
distribution. Our group will rapidly turn around the
required data
products and produce reports and software for the accurate
representation of the instrumental polarization. These
items will be
presented to STScI and for dissemination among the wider
astronomical
community.
WFPC2 10829
Secular Evolution at the End of the Hubble Sequence
The bulgeless disk galaxies at the end of the Hubble
Sequence evolve at
a glacial pace relative to their more violent,
earlier-type cousins. The
causes of their internal, or secular evolution are
important because
secular evolution represents the future fate of all
galaxies in our
accelerating Universe and is a key ingredient to
understanding galaxy
evolution in lower-density environments at present. The
rate of secular
evolution is largely determined by the stability of the
cold ISM against
collapse, star formation, and the buildup of a central
bulge. Key
diagnostics of the ISM's stability are the presence of
compact molecular
clouds and narrow dust lanes. Surprisingly, edge-on, pure
disk galaxies
with circular velocities below 120 km/s do not appear to
contain such
dust lanes. We propose to obtain ACS/WFC F606W images of a
well-selected
sample of extremely late-type disk galaxies to measure the
characteristic scale size of the cold ISM and determine if
they possess
the unstable, cold ISM necessary to drive secular
evolution. Our sample
has been carefully constructed to include disk galaxies
above and below
the critical circular velocity of 120 km/s where the dust
properties of
edge-on disks change so remarkably. We will then use
surface brightness
profiles to search for nuclear star clusters and
pseudobulges, which are
early indicators that secular evolution is at work, as
well as measure
the pitch angle of the dust lanes as a function of radius
to estimate
the central mass concentrations.
ACS/SBC 10814
The Masses for ultraluminous X-ray sources
Ultraluminous X-ray sources are non-nuclear sources in
normal disk
galaxies that are either stellar mass black holes that are
super-Eddington emitters, or 1E3-1E4 Msolar black holes
emitting
normally. We can distinguish between these models by
obtaining
constraints for the mass of the primary, which can be
accomplished
through UV objective prism spectra. This strategy begins
with the
optical identification of the secondary and identification
of its
spectral type in order to determine its mass and the Roche
Lobe radius.
Secondly, we need to determine whether an accretion disk
is present and
if its high ionization UV line luminosities point to a
stellar mass
black hole or a more massive object. Finally, if the black
hole is
1E3-1E4 Msolar, the orbital velocity of the secondary is
so large that a
Doppler shift will be detectable, even at the modest
resolution of the
prism.
WFPC2 10809
The nature of "dry" mergers in the nearby
Universe
Recent studies have shown that "dry" mergers of
red, bulge-dominated
galaxies at low redshift play an important role in shaping
today's most
massive ellipticals. These mergers have been identified in
extremely
deep ground-based images of red sequence galaxies at z ~
0.1. The
ground-based images reach surface brightness limits of AB
~ 29, but lack
the resolution to study the morphologies of the galaxies
inside the
effective radius. Here we propose to obtain ACS images of
a
representative sample of 40 of these red sequence
galaxies: 15 ongoing
dry mergers, 15 remnants, and 10 undisturbed objects. We
will measure
the isophote shapes and ellipticities of the galaxies,
their dust
content, morphological fine structure {shells and
ripples}, AGN content,
and their location on the Fundamental Plane. By comparing
galaxies in
different stages of the merging process we can constrain
the amount of
gas associated with these red mergers, the effect of
active nuclei, and
track structural changes. As two galaxies can be observed
in a single
orbit 20 orbits are requested to observe the 40 galaxies.
WFPC2 10798
Dark Halos and Substructure from Arcs & Einstein Rings
The surface brightness distribution of extended
gravitationally lensed
arcs and Einstein rings contains super-resolved
information about the
lensed object, and, more excitingly, about the smooth and
clumpy mass
distribution of the lens galaxies. The source and lens
information can
non-parametrically be separated, resulting in a direct
"gravitational
image" of the inner mass-distribution of
cosmologically-distant galaxies
{Koopmans 2005; Koopmans et al. 2006 [astro-ph/0601628]}.
With this goal
in mind, we propose deep HST ACS-F555W/F814W and
NICMOS-F160W WFC
imaging of 20 new gravitational-lens systems with
spatially resolved
lensed sources, of the 35 new lens systems discovered by
the Sloan Lens
ACS Survey {Bolton et al. 2005} so far, 15 of which are
being imaged in
Cycle-14. Each system has been selected from the SDSS and
confirmed in
two time- efficient HST-ACS snapshot programs {cycle
13&14}.
High-fidelity multi-color HST images are required {not
delivered by the
420s snapshots} to isolate these lensed images {properly
cleaned,
dithered and extinction-corrected} from the lens galaxy
surface
brightness distribution, and apply our "gravitational
maging" technique.
Our sample of 35 early-type lens galaxies to date is by
far the largest,
still growing, and most uniformly selected. This minimizes
selection
biases and small-number statistics, compared to smaller,
often
serendipitously discovered, samples. Moreover, using the
WFC provides
information on the field around the lens, higher S/N and a
better
understood PSF, compared with the HRC, and one retains
high spatial
resolution through drizzling. The sample of galaxy mass
distributions -
determined through this method from the arcs and Einstein
ring HST
images - will be studied to: {i} measure the smooth mass
distribution of
the lens galaxies {dark and luminous mass are separated
using the HST
images and the stellar M/L values derived from a joint stellar-dynamical
analysis of each system}; {ii} quantify statistically and
individually
the incidence of mass-substructure {with or without
obvious luminous
counter- parts such as dwarf galaxies}. Since dark-matter
substructure
could be more prevalent at higher redshift, both results
provide a
direct test of this prediction of the CDM hierarchical
structure-formation model.
WFPC2 10786
Rotational state and composition of Pluto's outer
satellites
We propose an intricate set of observations aimed at discovering
the
rotational state of the newly discovered satellites of
Pluto, S/2005 P1
and S/2005 P2. These observations will indicate if the
satellites are in
synchronous rotation or not. If they are not, then the
observations will
determine the rotational period or provide tight
constraints on the
amplitude. The other primary goal is to extend the
wavelength coverage
of the colors of the surface and allow us to constrain the
surface
compositions of both objects. From these data we will also
be able to
significantly improve the orbits of P1 and P2, improve the
measurement
of the bulk density of Charon, and search for albedo
changes on the
surface of Pluto.
FGS 10612
Binary Stars in Cyg OB2: Relics of Massive Star Formation
in a
Super-Star Cluster
We propose to make a high angular resolution SNAP survey
of the massive
stars in the nearby, super-star cluster Cyg OB2. We will
use FGS1r TRANS
mode observations to search for astrometric companions in
the separation
range of 0.01 to 1.00 arcsec and in the magnitude
difference range
smaller than 4 magnitudes. The observations will test the
idea that the
formation of very massive stars involves mergers and the
presence of
nearby companions. Discovery of companions to massive
stars in this
relatively nearby complex will provide guidance in the
interpretation of
apparently supermassive stars in distant locations. The
search for
companions will also be important for verification of
fundamental
parameters derived from spectroscopy, adjustments to main
sequence
fitting and distance estimations, determining third light
contributions
of eclipsing binaries, identifying wide colliding wind
binaries,
studying the relationship between orbital and spin angular
momentum, and
discovering binaries amenable to future mass
determinations. The massive
star environment in Cyg OB2 may be similar to the kinds
found in the
earliest epoch of star formation, so that a study of the
role of
binaries in Cyg OB2 will help us understand the formation
processes of
the first stars in the Universe.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are
preliminary reports
of potential non-nominal performance that will be
investigated.)
HSTARS:
10778 - GSAcq (1,2,1) failed to RGA Hold (Gyro Control)
At
AOS (103/22:48:00) GSAcq (1,2,1) scheduled at 103/22:21:38-22:28:56
had failed to RGA hold (Gyro Control) due to QSTOP flag on FGS2.
OBAD MAP RSS: 5.31 a-s
COMPLETED OPS REQUEST:
18033-1 - LGA Support for TCS Engineering Data
COMPLETED OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSacq
23
22
FGS
REacq
17
17
OBAD with Maneuver
80
80
SIGNIFICANT EVENTS: (None)