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24 April 2003

HUBBLE SPACE TELESCOPE

DAILY REPORT #3348

PERIOD COVERED:  DOY 113

Part 2 of 3

NICMOS/STIS CCD 9405

The Origin of Gamma-Ray Bursts

The rapid and accurate localization of gamma-ray bursts {GRBs}
promised by a working HETE-2 during the coming year may well
revolutionize our ability to study these enigmatic, highly luminous
transients. We propose a program of HST and Chandra observations to
capitalize on this extraordinary opportunity. We will perform some of
the most stringent tests yet of the standard model, in which GRBs
represent collimated relativistic outflows from collapsing massive
stars. NICMOS imaging and STIS CCD spectroscopy will detect broad
atomic features of supernovae underlying GRB optical transients, at
luminosities more than three times fainter than SN 1998bw. UV,
optical, and X-ray spectroscopy will be used to study the local ISM
around the GRB. Chandra spectroscopy will investigate whether the GRB
X-ray lines are from metals freshly ripped from the stellar core by
the GRB. HST and CTIO infra-red imaging of the GRBs and their hosts
will be used to determine whether `dark' bursts are the product of
unusually strong local extinction; imaging studies may for the first
time locate the hosts of `short' GRBs. Our early polarimetry and
late-time broadband imaging will further test physical models of the
relativistic blast wave that produces the bright GRB afterglow, and
will provide unique insight into the influence of the GRB environment
on the afterglow.
 
NICMOS 9423

NICMOS Observations of Transient Infrared Jets in the Galactic
Microquasar GRS1915+105

We propose to use HST/NICMOS to make Target of Opportunity
observations of the galactic microquasar GRS1915+105. This source
possesses transient radio jets which exhibit apparent superluminal
motions, and resolved infrared emission from these jets has been
observed in GRS1915+105 {Sams, Eckart, and Sunyaev, 1996; Eikenberry
and Fazio, 1996}. Because the jet ejection events are correlated with
X-ray outbursts, we will use observations of X-ray flares with the
Rossi X-Ray Timing Explorer to trigger the HST observations. We will
then monitor GRS1915+105 periodically with NICMOS, obtaining relative
astrometry, photometry, polarimetry, and grism spectroscopy of the
jets and the parent object. These observations will allow us to
greatly increase our understanding of the jets' radiative mechanisms
and physical conditions, and their evolution with time. We require
the capabilities of HST and NICMOS due to the small angular
separations between the jets and the parent object {increasing from
~0.1 to ~ 0.8 arcsec over the span of the TOO observations} and the
high reddening towards GRS1915+105 {A_V ~ 30 mag}.

ACS 9476

Galaxy Evolution in the Richest Clusters at z=0.8: the EDisCS Cluster
Sample

The study of distant cluster galaxies requires two key ingredients:
{1} deep high-resolution imaging, to constrain galaxy structure; and
{2} 8m-class spectroscopy, to measure stellar content, star-formation
rates, dynamics, and cluster membership. We will reach both
conditions with the addition of HST/ACS imaging to our suite of VLT
{36 nights} and NTT {20 nights} observations of 10 confirmed clusters
at z~0.8, drawn from the ESO Distant Cluster Survey {EDisCS}. The
proposed HST/ACS data will complement our existing optical/IR imaging
and spectroscopy with quantitative measures of cluster galaxy
morphologies {i.e. sizes and shapes, bulge-disk decompositions,
asymmetry parameters}, and with measurements of cluster masses via
weak lensing. Major advantages unique to the EDisCS project include:
{i} uniform selection of clusters; {ii} large enough sample sizes to
characterize the substantial cluster-to-cluster variation in galaxy
populations; {iii} large quantities of high quality data from 8m
telescopes; {iv} uniform measurements of morphologies, spectroscopic
and photometric redshifts, SEDs, star-formation/AGN activities, and
internal kinematics; {v} optical selection of clusters to complement
the X-ray selection of almost all high-z clusters in the ACS GTO
programs; {vi} forefront numerical simulations designed specifically
to allow physical interpretation of observed differences between the
high-z and local clusters. 

ACS 9480

Cosmic Shear With ACS Pure Parallels

directly measuring the amount and distribution of dark matter.
Several groups have recently detected this weak lensing by
large-scale structure, also called cosmic shear. The high resolution
and sensitivity of HST/ACS provide a unique opportunity to measure
cosmic shear accurately on small scales.  Using 260 parallel orbits
in Sloan textiti {F775W} we will measure for the first time:
beginlistosetlength sep0cm setlengthemsep0cm setlength opsep0cm em
the cosmic shear variance on scales <0.7 arcmin, em the skewness of
the shear distribution, and em the magnification effect. endlist Our
measurements will determine the amplitude of the mass power spectrum
sigma_8Omega_m^0.5, with signal-to-noise {s/n} ~ 20, and the mass
density Omega_m with s/n=4. They will be done at small angular scales
where non-linear effects dominate the power spectrum, providing a
test of the gravitational instability paradigm for structure
formation. Measurements on these scales are not possible from the
ground, because of the systematic effects induced by PSF smearing
from seeing. Having many independent lines of sight reduces the
uncertainty due to cosmic variance, making parallel observations
ideal.

WFPC2 9594

WFPC2 CYCLE 11 SUPPLEMENTAL DARKS pt2/3

This dark calibration program obtains 3 dark frames every day to
provide data for monitoring and characterizing the evolution of hot
pixels 

STIS 9606

CCD Dark Monitor-Part 2

Monitor the darks for the STIS CCD.

STIS 9608

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 9612

STIS CCD Hot Pixel Annealing Cycle 11

The effectiveness of the CCD hot pixel annealing process is assessed
by measuring the dark current behavior before and after annealing and
by searching for any window contamination effects. In addition CTE
performance is examined by looking for traps in a low signal level
flat. Follows on from proposal 8906.

 - Continued -

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