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Daily Report #5173



 
 
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Old September 3rd 10, 12:16 AM posted to sci.astro.hubble
Cooper, Joe
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Default Daily Report #5173


HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #5173

PERIOD COVERED: 5am September 1 - 5am September 2, 2010 (DOY 244/09:00z-245/09:00z)

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 9 9
FGS REAcq 6 6
OBAD with Maneuver 9 9

SIGNIFICANT EVENTS: (None)


OBSERVATIONS SCHEDULED:

ACS/WFC 11996

CCD Daily Monitor (Part 3)

This program comprises basic tests for measuring the read noise and
dark current of the ACS WFC and for tracking the growth of hot pixels.
The recorded frames are used to create bias and dark reference images
for science data reduction and calibration. This program will be
executed four days per week (Mon, Wed, Fri, Sun) for the duration of
Cycle 17. To facilitate scheduling, this program is split into three
proposals. This proposal covers 308 orbits (19.25 weeks) from 21 June
2010 to 1 November 2010.

COS/FUV 12216

Taming the Invisible Monster with COS: Eclipse Spectroscopy of Epsilon
Aurigae

We request three single orbit COS observations of the enigmatic binary
epsilon Aurigae. This 27-year binary will be in total eclipse during
all of 2010 and into spring 2011. COS observations are needed in order
to (1) confirm, via higher S/N UV spectroscopy, the FUSE observation
that a B5V star lurks inside the eclipse-causing dust disk, (2) obtain
temperature and density diagnostics of the line of sight columns
during eclipse for inclusion in the ongoing, panchromatic studies of
this rare event, and (3) allow, in coordination with Spitzer Space
Telescope observations, a detailed view of the "invisible" large
eclipsing dust disk surrounding the B star. Only COS has the full UV
wavelength coverage to sample two of the three components in this
binary (the F and B stars) with the SNR to accomplish our scientific
goals.

FGS 12321

The Parallax of the Planet Host Star XO-3

We will use HST+FGS to measure the parallax of the transiting planet
host star XO-3. The resulting accurate distance measurement will
provide the most accurate radius determination to date for this
massive extrasolar planet (XO-3b), allowing us to critically test
current giant extrasolar planet structure models. These observations
will also constrain the amount of heating that may be produced inside
XO-3b by tides raised on the planet as it moves through its 3.2 d
eccentric (e ~ 0.22) orbit.

NIC2/WFC3/IR 11219

Active Galactic Nuclei in Nearby Galaxies: A New View of the Origin of
the Radio-Loud Radio-Quiet Dichotomy?

Using archival HST and Chandra observations of 34 nearby early-type
galaxies (drawn from a complete radio selected sample) we have found
evidence that the radio-loud/radio-quiet dichotomy is directly
connected to the structure of the inner regions of their host galaxies
in the following sense: [1] Radio-loud AGN are associated with
galaxies with shallow cores in their light profiles [2] Radio-quiet
AGN are only hosted by galaxies with steep cusps. Since the brightness
profile is determined by the galaxy's evolution, through its merger
history, our results suggest that the same process sets the AGN
flavor. This provides us with a novel tool to explore the co-evolution
of galaxies and supermassive black holes, and it opens a new path to
understand the origin of the radio-loud/radio-quiet AGN dichotomy.
Currently our analysis is statistically incomplete as the brightness
profile is not available for 82 of the 116 targets. Most galaxies were
not observed with HST, while in some cases the study is obstructed by
the presence of dust features. We here propose to perform an infrared
NICMOS snapshot survey of these 82 galaxies. This will enable us to i)
test the reality of the dichotomic behavior in a substantially larger
sample; ii) extend the comparison between radio-loud and radio-quiet
AGN to a larger range of luminosities.

STIS/CCD 11567

Boron Abundances in Rapidly Rotating Early-B Stars

Models of rotation in early-B stars predict that rotationally driven
mixing should deplete surface boron abundances during the
main-sequence lifetime of many stars. However, recent work has shown
that many boron depleted stars are intrinsically slow rotators for
which models predict no depletion should have occurred, while
observations of nitrogen in some more rapidly rotating stars show less
mixing than the models predict. Boron can provide unique information
on the earliest stages of mixing in B stars, but previous surveys have
been biased towards narrow-lined stars because of the difficulty in
measuring boron abundances in rapidly rotating stars. The two targets
observed as part of our Cycle 13 SNAP program 10175, just before STIS
failed, demonstrate that it is possible to make useful boron abundance
measurements for early-B stars with Vsin(i) above 100 km/s. We propose
to extend that survey to a large enough sample of stars to allow
statistically significant tests of models of rotational mixing in
early-B stars.

STIS/CCD 11843

STIS CCD Performance Monitor

This activity measures the baseline performance and commandability of
the CCD subsystem. Only primary amplifier D is used. Bias and
Flatfield exposures are taken in order to measure bias level, read
noise, CTE, and gain. Numerous bias frames are taken to permit
construction of "superbias" frames in which the effects of read noise
have been rendered negligible. Full frame and binned observations are
made, with binning factors of 2 x 1, 1 x 2, 2 x 2. Bias frames are
taken in subarray readouts to check the bias level for ACQ and
ACQ/PEAK observations. All exposures are internals.

STIS/CCD 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

STIS/CCD 11847

CCD Bias Monitor-Part 2

Monitor the bias in the 1x1, 1x2, 2x1, and 2x2 bin settings at gain=1,
and 1x1 at gain = 4, to build up high-S/N superbiases and track the
evolution of hot columns.

STIS/CCD/MA/WFC3/UV 11665

The Formation Mechanisms of Extreme Horizontal Branch Stars

Blue hook stars are a class of hot (~35, 000 K) subluminous extreme
horizontal branch (EHB) stars that have been recently discovered using
HST ultraviolet images of the massive globular clusters omega Cen and
NGC 2808. These stars occupy a region of the HR diagram that is
unexplained by canonical stellar evolution theory. Using new
theoretical evolutionary and atmospheric models, we have shown that
the blue hook stars are very likely the progeny of stars that undergo
extensive internal mixing during a late helium core flash on the white
dwarf cooling curve. This "flash mixing" produces an enormous
enhancement of the surface helium and carbon abundances (relative to
the abundance pattern that existed on the main sequence), which
suppresses the observed flux in the far-UV. Because stars born with a
high helium abundance are more likely to evolve into hot horizontal
branch stars, flash mixing is more likely to occur in those massive
clusters capable of helium self-enrichment. However, a high initial
helium abundance, by itself, is not sufficient to explain the presence
of a blue hook population - flash mixing of the envelope is also
required.

We propose far-UV spectroscopy of normal and subluminous EHB stars in
NGC 2808 that will unambiguously test this new formation mechanism.
These observations will easily detect the helium and carbon
enhancements predicted by flash mixing and will therefore determine if
flash mixing represents a new evolutionary channel for populating the
hot end of the EHB. More generally, our observations will help to
clarify the role of helium self-enrichment in producing blue
horizontal branch morphologies and multiple main sequences in massive
globular clusters. Finally, these results will provide new insight
into the origin and abundance anomalies of the hot helium-rich
subdwarf B and O stars in the Galactic field.

WFC3/ACS/IR 11647

A Deep Exploration of Classes of Long Period Variable Stars in M31

We propose a thrifty but information-packed investigation with WFC3/IR
F160W and F110W providing crucial information about Long Period
Variables in M31, at a level of detail that has recently allowed the
discovery of new variable star classes in the Magellanic Clouds, a
very different stellar population. These observations are buttressed
by an extensive map of the same fields with ACS and WFC3 exposures in
F555W and F814W, and a massive ground- based imaging patrol producing
well-sampled light curves for more than 400,000 variable stars. Our
primary goal is to collect sufficient NIR data in order to analyze and
classify the huge number of long-period variables in our catalog (see
below) through Period Luminosity (P/L) diagrams. We will produce
accurate P/L diagrams for both the bulge and a progression of
locations throughout the disk of M31. These diagrams will be similar
in quality to those currently in the Magellanic Clouds, with their
lower metallicity, radically different star formation history, and
larger spread in distance to the variables. M31 offers an excellent
chance to study more typical disk populations, in a manner which might
be extended to more distant galaxies where such variables are still
visible, probing a much more evenly spread progenitor age distribution
than cepheids (and perhaps useful as a distance scale alternative or
cross- check). Our data will also provide a massive and unique
color-magnitude dataset; we expect that this study will produce
several important results, among them a better understanding of P/L
and P/L-color relations for pulsating variables which are essential to
the extragalactic distance ladder. We will view these variables at a
common distance over a range of metallicities (eliminating the
distance-error vs. metallicity ambiguity between the LMC and SMC),
allow further insight into possible faint-variable mass-loss for
higher metallicities, and in general produce a sample more typical of
giant disk galaxies predominant in many studies.

WFC3/IR/S/C 11929

IR Dark Current Monitor

Analyses of ground test data showed that dark current signals are more
reliably removed from science data using darks taken with the same
exposure sequences as the science data, than with a single dark
current image scaled by desired exposure time. Therefore, dark current
images must be collected using all sample sequences that will be used
in science observations. These observations will be used to monitor
changes in the dark current of the WFC3-IR channel on a day-to-day
basis, and to build calibration dark current ramps for each of the
sample sequences to be used by Gos in Cycle 17. For each sample
sequence/array size combination, a median ramp will be created and
delivered to the calibration database system (CDBS).

WFC3/UV 12237

Orbits, Masses, Densities, and Colors of Two Transneptunian Binaries

Binaries are the key to learning many crucial bulk properties of
transneptunian objects (TNOs) including their masses. Perhaps the most
interesting mass-dependent property of a TNO is its bulk density,
which provides unique information about its bulk composition and
interior structure. Densities have so far only been measured for a
handful of binary TNO systems. This proposal seeks to determine orbits
and thus masses of two more binary TNOs, both of which are also to be
observed at thermal infrared wavelengths by the Herschel spacecraft.
Combining the masses from Hubble with the sizes from Herschel will
enable us to compute their densities. We will also obtain
multi-wavelength photometric colors of the individual components of
each binary system. It is imperative to link colors to the physical
properties measurable in binary systems in order to use the remnant
planetesimals in today's Kuiper belt to learn more about the early
history of our own solar system, and more generally about how
planetesimals form in nebular disks and subsequently evolve.

WFC3/UVIS 11729

Photometric Metallicity Calibration with WFC3 Specialty Filters

The community has chosen to include several filters in the WFC3 filter
complement that have been designed to allow fairly precise estimates
of stellar metallicities, and many science programs are enabled by
this capability. Since these filters do not exactly match those used
for this purpose on the ground, however, the mapping of stellar colors
to stellar metallicities needs to be calibrated. We propose to achieve
this calibration through observations of five stellar clusters with
well known metallicities. We will calibrate several different filter
calibrations which will allow future users to determine what filter
combination best meets their science needs.

WFC3/UVIS 11905

WFC3 UVIS CCD Daily Monitor

The behavior of the WFC3 UVIS CCD will be monitored daily with a set
of full-frame, four-amp bias and dark frames. A smaller set of 2Kx4K
subarray biases are acquired at less frequent intervals throughout the
cycle to support subarray science observations. The internals from
this proposal, along with those from the anneal procedure (Proposal
11909), will be used to generate the necessary superbias and superdark
reference files for the calibration pipeline (CDBS).

WFC3/UVIS 11908

Cycle 17: UVIS Bowtie Monitor

Ground testing revealed an intermittent hysteresis type effect in the
UVIS detector (both CCDs) at the level of ~1%, lasting hours to days.
Initially found via an unexpected bowtie- shaped feature in flatfield
ratios, subsequent lab tests on similar e2v devices have since shown
that it is also present as simply an overall offset across the entire
CCD, i.e., a QE offset without any discernable pattern. These lab
tests have further revealed that overexposing the detector to count
levels several times full well fills the traps and effectively
neutralizes the bowtie. Each visit in this proposal acquires a set of
three 3x3 binned internal flatfields: the first unsaturated image will
be used to detect any bowtie, the second, highly exposed image will
neutralize the bowtie if it is present, and the final image will allow
for verification that the bowtie is gone.

WFC3/UVIS 11912

UVIS Internal Flats

This proposal will be used to assess the stability of the flat field
structure for the UVIS detector throughout the 15 months of Cycle 17.
The data will be used to generate on-orbit updates for the delta-flat
field reference files used in the WFC3 calibration pipeline, if
significant changes in the flat structure are seen.

WFC3/UVIS 11914

UVIS Earth Flats

This program is an experimental path finder for Cycle 18 calibration.
Visible-wavelength flat fields will be obtained by observing the dark
side of the Earth during periods of full moon illumination. The
observations will consist of full-frame streaked WFC3 UVIS imagery:
per 22- min total exposure time in a single "dark-sky" orbit, we
anticipate collecting 7000 e/pix in F606W or 4500 e/pix in F814W. To
achieve Poisson S/N 100 per pixel, we require at least 2 orbits of
F606W and 3 orbits of F814W.

For UVIS narrowband filters, exposures of 1 sec typically do not
saturate on the sunlit Earth, so we will take sunlit Earth flats for
three of the more-commonly used narrowband filters in Cycle 17 plus
the also-popular long-wavelength quad filters, for which we get four
filters at once.

Why not use the Sunlit Earth for the wideband visible-light filters?
It is too bright in the visible for WFC3 UVIS minimum exposure time of
0.5 sec. Similarly, for NICMOS the sunlit-Earth is too bright which
saturates the detector too quickly and/or induces abnormal behaviors
such as super-shading (Gilmore 1998, NIC 098-011). In the narrowband
visible and broadband near- UV its not too bright (predictions in Cox
et al. 1987 "Standard Astronomical Sources for HST: 6. Spatially Flat
Fields." and observations in ACS Program 10050).

Other possibilities? Cox et al.'s Section II.D addresses many other
possible sources for flat fields, rejecting them for a variety of
reasons. A remaining possibility would be the totally eclipsed moon.
Such eclipses provide approximately 2 hours (1 HST orbit) of
opportunity per year, so they are too rare to be generically useful.
An advantage of the moon over the Earth is that the moon subtends less
than 0.25 square degree, whereas the Earth subtends a steradian or
more, so scattered light and light potentially leaking around the
shutter presents additional problems for the Earth. Also, we're unsure
if HST can point 180 deg from the Sun.


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