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Дата изменения: Tue Dec 11 01:29:52 2001
Дата индексирования: Sat Dec 22 13:25:22 2007
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Cycle 11 Abstract catalog (based on Phase I submissions)
Generated on: Mon Dec 10 08:39:48 EST 2001
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Proposal Category: GO
Scientific Category: Quasar Absorption Lines and IGM
ID: 9350
Title: Intergalactic HeII absorption in CSO 118 = HS 1157+3143
PI: Dieter Reimers
PI Institution: Hamburger Sternwarte

We propose to observe the HeII Gunn-Peterson effect in the z = 3 quasar CSO
118, which has been discovered in our SNAPSHOT survey to have a transparent
line of sight. The aim is in particular to extend our knowledge about HeII
reionization which has been observed to take place in the range z = 3.1 to z =
2.8. While existing and future FUSE observations will cover the redshift range
z < 2.9, redshifts above 2.9 have been covered by HST with only 2 lines of
sights.
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Proposal Category: GO
Scientific Category: Cosmology
ID: 9351
Title: Determining Hubble's Constant from Observations of
Cepheids in the Host Galaxy of SN Ia 1994ae
PI: Adam Riess
PI Institution: Space Telescope Science Institute

We propose to determine the luminosity of the type Ia supernova (SN Ia) 1994ae
by observing Cepheids in the host spiral galaxy NGC 3370. Modern CCD
photometry has yielded an extremely tight Hubble diagram for SNe Ia with a
precisely determined intercept (i.e., Delta H_0/H_0 ~ 1) measurement of the
true Hubble constant is still limited by the calibration. The HST calibration
of all but a few SNe Ia observed to date is significantly compromised by the
systematics of photographic photometry and host galaxy extinction, as well as
by the photometric uncertainties associated with WFPC2. In contrast, SN
1994ae is one of the very best-observed SNe Ia with CCD photometry. The
exquisite B, V, $R, and I light curves are well-sampled beginning 10 days
before maximum brightness, and they indicate little reddening. From our
supernova photometry and the current provisional SN Ia calibration we would
find a distance of 30 +/- 2.1 Mpc, well within the range where ACS can
accurately observe Cepheid light curves and distinguish Cepheids from
nonvariable stars.
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Proposal Category: GO
Scientific Category: Cosmology
ID: 9352
Title: The Deceleration Test from Treasury Type Ia Supernovae at
Redshifts 1.2 to 1.6
PI: Adam Riess
PI Institution: Space Telescope Science Institute

Type Ia supernovae (SNe Ia) provide the only direct evidence for an
accelerating universe, an extraordinary result that needs a rigorous test.
The case for cosmic acceleration rests on the observation that SNe Ia at z ~
0.5 are ~ 0.25 mag fainter than they would be in a universe without
acceleration. A powerful and straightforward way to assess the reliability of
the SN Ia measurement and the conceptual framework of its interpretation is to
look for cosmic deceleration at z >= 1. This would be a clear signature of a
mixed dark-matter and dark-energy universe. Systematic errors in the SN Ia
result attributed to grey dust or cosmic evolution of the SN Ia peak
luminosity would not show this change of sign. We have demonstrated proof of
this concept with a single SN Ia, SN 1997ff at z = 1.7, found and followed by
HST. The results suggest an early epoch of deceleration, but this is too
important a conclusion to rest on just one object. Here we propose to use HST
for observations of six SNe Ia in the range 1.2 <= z <= 1.6, that will be
discovered as a byproduct from proposed Treasury programs for high-latitude
ACS surveys. Six objects will provide a much firmer foundation for a
conclusion that touches on important questions of fundamental physics.
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Proposal Category: GO
Scientific Category: Hot Stars
ID: 9353
Title: Direct imaging of the progenitors of massive, core-
collapse supernovae
PI: Stephen Smartt
PI Institution: Institute of Astronomy

Modern supernovae searches in the nearby Universe are discovering vast numbers
of SNe which have massive star progenitors (Types II, Ib and Ic). The
extensive HST (and ground-based) image archives of galaxies within ~20 Mpc
enables their individual bright stellar content to be resolved. As massive,
evolved stars are the most luminous single objects in a galaxy, the
progenitors of core-collapse SNe should be directly detectable on pre-
explosion images. Within the last year we have set direct mass limits on the
progenitors of two SNe Type II-P by analysing pre-explosion archive images and
follow up HST exposures. We have now identified six other recent, nearby SNe
which have WFPC2 archive exposures of the site taken before explosion.
Additionally, our Cycle 10 SNAP program will double the WFPC2 image archive of
nearby galaxies which significantly increases the chances of having multi-
colour photometry of pre-explosion sites for future SNe. In this Cycle, we
request time on two fronts. Firstly we require imaging of the six SNe with
existing pre-explosion data in order to perform exact astrometry of the SNe
positions to around 0.05". Secondly, as a follow on from our two successful
Cycle 10 programs, we request ToO status for any nearby core-collapse SN which
explodes during Cycle 11 and which has pre-explosion HST images. The goal of
this proposal is to directly identify the progenitor stars of core-collapse
SNe.
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Proposal Category: GO
Scientific Category: Solar System
ID: 9354
Title: Saturn's Atmospheric Structure at Solstice
PI: Erich Karkoschka
PI Institution: University of Arizona

We propose to image Saturn near its solstice with the same 22 WFPC2/NICMOS
filters which we imaged Saturn near its equinox about six years ago.
Additionally, we propose to use the ACS/HRC with its high ultraviolet
throughput and its superior spatial resolution. All filters span a wavelength
range of a factor of 10, they cover methane band strengths over several orders
of magnitude, and they include the center and wings of the hydrogen dipole
absorption near 2 Mum. Thus, they probe many atmospheric levels over five
scale heights. The 22 WFPC2/NICMOS filters have proven to provide an
excellent probe of Saturn's vertical aerosol structure. The spatial resolution
yields several hundred resolution elements in latitude which can be grouped
into 10-15 distinct zones. The best viewing of Saturn high southern latitudes
occurs at its winter solstice which happens during Cycle 11. The three
spacecraft which have visited Saturn flew by near Saturn's equinox, and
Cassini will miss the solstice too. HST acquired comprehensive data of Saturn
near its last equinox in 1995. The proposed observations will expand this
data set to Saturn's solstice and thus provide a unique record of its seasonal
variation.
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Proposal Category: GO
Scientific Category: Solar System
ID: 9355
Title: Test of Efficient Subsampling for NIC3 by Smearing Images
of Jupiter
PI: Erich Karkoschka
PI Institution: University of Arizona

Several camera/filter combinations of HST do not sample the point spread
function with a sufficiently small sampling interval to retrieve the full
spatial resolution possible at the wavelength of the filter. This is
especially true for the NIC3 camera. Dithering observations by sub-pixels is
the standard solution. However, the extra overhead time of dithering can be
too long to make dithering feasible for many solar system targets where
rotation or relative motion is noticeable during the overhead time. I suggest
to test a new method where a single exposure yields 10 dithered images which
provide sufficient subpixel information to recover the whole spatial
capabilities of HST. I suggest to test this method with Jupiter imaged by
eight NIC3 filters. The same eight filters of NIC1 or NIC2 provide the
standard for comparison with still exposures. The method lets Jupiter smear
across NIC3 by about three pixels during the whole exposure by changing HST's
tracking rates. Each interval between readouts of NIC3 provides a dithered
image. It is difficult to predict how well the reduced NIC3 images will
compare with the still NIC1 images with respect to spatial resolution, but one
orbit of HST can test the method. If this method works well, it could be
applied to many other future observations.
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Proposal Category: SNAP
Scientific Category: ISM and Circumstellar Matter
ID: 9356
Title: SNAPSHOT survey of the Planetary Nebulae population of
the Galactic Bulge
PI: Albert Zijlstra
PI Institution: Department of Physics

The spectacular structures seen in HST images of planetary nebulae (PNe) are
generally accepted as originating from hydrodynamical interactions between
stellar winds: the interacting-stellar wind model (ISW). Traditionally, the
shaping is thought to occur after the star becomes hot enough to ionize the
PN. But recent HST images indicate that the shaping may occur earlier, and the
newer GISW model puts the shaping during the pre-planetary nebula evolution.
The relative importance of both models is not known: GISW shaping will account
for some fraction of PNe, but estimates range from 15--100 during the PN
phase, especially for the youngest PNe. We here propose an HST SNAPshot survey
of compact PNe in the Galactic Bulge, to test these predictions. The Bulge
provides the only PNe population for which progenitor masses are known and
nebular ages can be measured. In support of these HST measurements we have
already measured velocity fields and emission line fluxes. The survey will
give an unbiassed sampling of morphologies, and allow evolutionary sequences
to be determined to test the ISW versus the GISW model. By-products of the
survey will be the determination of nebular masses, diameters and filling
factors. We will also obtain the White Dwarf mass distribution in the Bulge,
and the initial-final mass function for low-mass stars.
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Proposal Category: SNAP
Scientific Category: Hot Stars
ID: 9357
Title: Towards a global understanding of accretion physics --,
Clues from an UV spectroscopic survey of cataclysmic
variables
PI: Boris T. Gaensicke
PI Institution: Universitaets-Sternwarte Goettingen

Accretion inflows and outflows are fundamental phenomena in a wide variety of
astrophysical environments, such as Young Stellar Objects, galactic binaries,
and AGN. Observationally, cataclysmic variables (CVs) are particularly well
suited for the study of accretion processes. We propose to carry out a STIS
UV spectroscopic snapshot survey of CVs that fully exploits the diagnostic
potential of these objects for our understanding of accretion physics. This
survey will provide an homogenous database of accretion disc and wind outflow
spectra covering a wide range of mass transfer rates and binary inclinations.
We will analyse these spectra with state-of-the-art accretion disc model
spectra (SYNDISK), testing our current knowledge of the accretion disc
structure, and, thereby, providing new insight into the so far not well
understood process of viscous dissipation. We will use our parameterised wind
model PYTHON for the analysis of the radiation driven accretion disc wind
spectra, assessing the fundamental question whether the mass loss rate
correlates with the disc luminosity. In addition, our survey data will
identify a number of systems in which the white dwarf significantly
contributes to the UV flux, permitting an analysis of the impact of mass
accretion on the evolution of these compact stars. This survey will at least
double, if not triple, the number of high-quality accretion disc / wind
outflow / accreting white dwarf spectra, and we waive our proprietary rights
to permit a timely use of this database.
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Proposal Category: GO
Scientific Category: Cool Stars
ID: 9359
Title: The Old Star CS 31082-001, the Age of the Universe, and
the Nature of the r-process
PI: Roger Cayrel
PI Institution: Observatoire de Paris

We propose to observe the newly discovered r-process-element enhanced star,
CS 31082-001 (Fe/H ~ -2.9), in order to determine abundances of the heaviest
stable elements, using absorption lines that are only reachable in the near
UV. This star is the only halo star for which a uranium detection has been
reported, and for which the U/Th chronometer has been used to specify an age
limit. In order to improve the accuracy of the age determination from U/Th we
require abundance estimates of the daughter nuclides --Pb & Bi-- for which
only upper limits have been obtained from ground-based observations. Such
estimates will provide crucial constraints on the initial production ratio of
U/Th, resulting in a more strict lower limit on the age of this star's
progenitor, hence on the age of the Universe. Measurements of 3rd-peak
neutron-capture elements, such as Pt, Os, Ir, and Au, all with lines in the
2400-3100 Angstrom range, will expand our knowledge of element synthesis in
the early Galaxy. Our recent ESO-VLT data indicate that the neutron-capture
elements in this star exhibit different enhancements as compared with the
previously known "r-process star" CS 22892-052, an apparent anomaly that
must be resolved. CS 31082-001 is the ideal HST target in its class -- it is
4-times brighter than CS 22892-052, and less affected by molecular line
blending. Consequently, these HST data will become the reference in all
future studies of similar stars.
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Proposal Category: SNAP
Scientific Category: Galaxies
ID: 9360
Title: Paschen-alpha Imaging of a SIRTF-Selected Nearby Galaxy
Sample
PI: Robert Kennicutt
PI Institution: University of Arizona

We propose to carry out a NICMOS snapshot survey in the Paschen-alpha (PAlpha)
emission line and H-band of the sample of galaxies being observed at 3.5 --
160 microns as part of SIRTF Nearby Galaxies Survey (SINGS) and a related
guaranteed time survey of starburst galaxies. The PAlpha images, accessible
only from HST, will be combined with groundbased HAlpha imaging to measure the
extinction in the star-forming centers of these galaxies, and obtain robust,
extinction-corrected maps of the massive star formation rate (SFR). The PAlpha
data by themselves will provide reliable `extinction-free' SFRs, and a cross-
calibration of the (dust--affected) HAlpha-- and UV--based SFRs. The PAlpha--
based SFR measurements will extend the SFR-vs.-gas density law (Schmidt--law)
to surface densities at least 30 times higher than what is accessible using
HAlpha--based SFR measurements alone, bridging the gap between normal galaxies
and IR--luminous starbursts. Furthermore, the combination of the HST PAlpha
images with the SIRTF images and spectra, as well as ancillary ground--based
UBVRIJHK images and GALEX UV images being obtained as part of the SINGS
project, will provide a definitive study of the radiative transfer of
starlight and dust heating in star--forming galaxies. The processed NICMOS
images will be incorporated into the public SINGS Legacy Data Archive, to
enable scores of follow-up studies by the astronomical community at large.
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Proposal Category: GO
Scientific Category: Stellar Populations
ID: 9361
Title: Searching for Primeval Galaxies: the promising case of
SBS 1415+437
PI: Alessandra Aloisi
PI Institution: The Johns Hopkins University

Do primeval galaxies exist in the local Universe? The best candidates are
extremely metal-poor (Z <=sssim 1/20 Z) blue compact dwarf (BCD)
galaxies whose photometric and chemical properties are consistent with a
stellar population younger than 100 Myr. SBS 1415+437 (Z = 1/21 Z) is
the closest candidate: its proximity (d = 11.4 Mpc), detailed spectroscopic
knowledge of its HII regions and low metal content, used to infer the
primordial ^4He abundance, make it the best target for this investigation. We
propose to take deep exposures of SBS 1415+437 with the ACS in the F814W and
F606W filters. This instrument has resolution and magnitude limits allowing us
to reach and resolve with the required accuracy individual stars 1 mag below
the tip of the red giant branch (RGBT). If present, these stars will provide a
clear sign of an old stellar population (with ages >~ 1 Gyr) and an
independent distance indicator. If absent, this will unambiguously show that
the system has started to form stars only recently and can be considered the
first robust case of local primeval galaxy. We propose to take exposures in
the F658N (HAlpha Lambda6563) and FR505N (HBeta Lambda4861) filters to study
the morphology of the ionized gas through HAlpha emission and map the dust
content with the HAlpha/HBeta ratio in order to solve the age-dust degeneracy
of the photometry by constraining reddening effects.
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Proposal Category: GO
Scientific Category: AGN/Quasars
ID: 9362
Title: STIS Observations of the Intrinsic UV Absorption in the
Dwarf Seyfert Nucleus of NGC 4395
PI: Steven Kraemer
PI Institution: Catholic University of America

The Sd IV dwarf galaxy NGC 4395 is one of the nearest (d ~ 4.2 Mpc) and least
luminous (L_bol ~ 10^41 ergs s^-1) examples of Seyfert 1 galaxies.
Furthermore, it is the only known example of an active nucleus within a
bulgeless, extreme late-type galaxy. This unique object possesses all of the
classic Seyfert 1 properties in miniature, including broad and narrow emission
lines and highly variable X-ray emission, presumably powered by a small (few x
10^4 M) black hole. Furthermore, we have discovered evidence for
blueshifted, intrinsic absorption lines in the UV (C IV LambdaLambda1548.2,
1550.8), while X-ray spectra show the presence of bound-free edges from O VII
and O VIII. We propose HST/STIS echelle observations to determine the
properties (ionization states, column densities, velocity coverages, covering
factors) of the intrinsic UV absorbers in NGC 4395. Due to the high covering
factor of its narrow-line emission, NGC 4395 offers the best case for testing
the connection between the absorbers and the narrow-line region (NLR).
Furthermore, an empirical comparison of its absorption properties with those
in higher luminosity active galactic nuclei (AGN) will provide valuable
constraints on dynamical models of the absorbers, which make predictions that
are strongly dependent on luminosity and/or central black hole mass.
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Proposal Category: GO
Scientific Category: Galaxies
ID: 9363
Title: Ultra Low Surface Brightness Galaxies
PI: Nelson Caldwell
PI Institution: Smithsonian Astrophysical Observatory

Extremely low surface brightness galaxies have been detected in the Virgo
cluster, which are 2 magnitudes fainter than any previously known in that
cluster or even in the Local Group. ACS images of three of these should
resolve stars at the giant branch tip, and allow us to determine distances,
mean metal abundance of the stars, and rough ages. Confirmation of the nature
of these galaxies will provide evidence that dark matter halos are pervasive
in the universe, extending to galaxies with stellar densities 6 times lower
than currently known. These resolved stars would be the most distant yet
observed accurately by HST.
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Proposal Category: GO
Scientific Category: Hot Stars
ID: 9364
Title: The Parallaxes and Proper Motions of Two Nearby Neutron
Stars
PI: David Kaplan
PI Institution: California Institute of Technology

We propose to measure the parallax of two nearby neutron stars to the
highest possible level of accuracy, 0.5 mas. The primary
goal is to determine the neutron-star radius at infinity with better
than 1km precision, and therewith obtain a direct constraint on the
equation of state of matter at supra-nuclear density. The required
flux and temperature determinations are easiest for the so-called
isolated or radio-quiet neutron stars because of their apparently
completely thermal spectrum. We argue that the importance of the
possible results warrants a study to the best possible level of the
best possible sources, and request 24 orbits for the two brightest
isolated neutron stars, RX~J1856.5$-$3754 and RX~J0720.4$-$3125. We
will also determine whether the enigmatic RX~J0720.4$-$3125 is an old
magnetar or an accreting source, based on its luminosity and proper
motion.
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Proposal Category: GO
Scientific Category: AGN/Quasars
ID: 9365
Title: Spectroscopy in the Inner Region of the 3C 48 Host Galaxy
PI: Alan Stockton
PI Institution: Institute for Astronomy

As far as we are aware, there is only one host galaxy continuum feature in a
luminous QSO that is bright enough for practical STIS spectroscopy: this is
the bright peak ~1" NE of the well-known quasar 3C 48. This feature (3C 48A)
is enigmatic, with an apparently distorted morphology. It may be the
distended nuclear region of one of the galaxies in this major merger. It
might, instead, possibly be the result of interaction of the compact-steep
spectrum radio jet with ambient material; but this seems unlikely because the
correspondence between the radio and optical morphologies is not very good. We
also know from ground-based and HST imaging that 3C 48A is overwhelmingly
dominated by continuum radiation, not line emission, and the colors seem to be
inconsistent with stars as young as the probable age of the radio jet. Our
previous high S/N ground-based spectroscopy of 3C 48 covered most regions of
host galaxy beyond ~2" from the QSO. From this spectroscopy and spectral
synthesis models, we have been able to determine mean ages for recent
starbursts in various parts of the host galaxy as well as the velocity field
of the stars. By tying the proposed STIS spectroscopy of 3C 48A to our
existing spectroscopy of the host galaxy, together with archival PC images, we
expect to be able to determine the nature of this unusual inner structure and
its role in the evolutionary history of 3C 48.
================================================================================
Proposal Category: GO
Scientific Category: ISM and Circumstellar Matter
ID: 9366
Title: H_2 Imaging of Proto-Planetary Nebulae: Probing the
Dynamics and Morphology
PI: Bruce Hrivnak
PI Institution: Valparaiso University

H_2 emission provides an excellent probe of the physical conditions in
planetary nebulae (PNs) and also in proto-planetary nebulae (PPNs), objects in
transition between the asymptotic giant branch (AGB) and PN phases. It is
thought that the shaping of the PN occurs when a fast wind interacts with the
remnant of the AGB progenitor during the PPN phase. The study of shock-
excited H_2 in PPNs will allow us to study this process. We request HST/NICMOS
H_2 and complementary K and H broad-band images of 13 PPNs with a range of
spectral types of the central star. We presently have very high-resolution
(~100,000) H_2 spectra for 7 of these, which we will use with the high-
resolution images to study the velocity structure of the fast wind. We will
also explore the relationship between the presence of H_2 and a bipolar shape
for the nebula, as has been found in PNs. However, the role of the equatorial
torus is expected to be different in these two cases, and in the PPNs it is
expected to collimate the wind rather than shield the molecules. Thus the H_2
in the PPNs is expected at the ends of the lobes rather than in the torus.
Radiatively-excited H_2 emission appears to be common in PPNs with central
stars of B spectral types; this appears to be a transitional stage in the
evolution of the H_2 in the nebula which these images will help us to better
understand.
================================================================================
Proposal Category: GO
Scientific Category: Quasar Absorption Lines and IGM
ID: 9367
Title: Unique Opportunities to Search for the Optical
Counterparts to High-Z Damped LyAlpha Systems
PI: Cyril Hazard
PI Institution: University of Pittsburgh

The galaxies responsible for damped LyAlpha absorption in QSO spectra are
difficult to observe against the strong background QSO emission. We propose to
detect even low luminosity galaxies associated with QSO absorption line
systems out to redshifts as high as z = 1.8 by observing them in the shadow
cast by an even higher redshift damped LyAlpha absorber. As a result the
galaxy will be observed free of contamination by the background AGN and of the
uncertainties which arise when image processing techniques are required to
remove the AGN emission. We propose two approaches. In the first we will
attempt to detect a z = 1.8634 system seen in the optical spectrum of a high-z
BL Lac object in the shadow of two higher-redshift systems seen in the same
optical spectrum. In the second only the higher redshift shadowing LyAlpha
system is seen in the optical spectrum and the presence of the lower-redshift
systems at z = 0.713 and z = 1.0466 are inferred from the presence of strong
MgII, SiII and FeII absorption lines.
================================================================================
Proposal Category: GO
Scientific Category: Cool Stars
ID: 9368
Title: Spectrophotometry of Procyon A: Testing Metal Opacities
PI: Carlos Allende-Prieto
PI Institution: University of Texas

Metal opacity shapes the near-UV spectrum of late-type stars, which dominate
intermediate and old stellar populations. Learning the details of how metal
opacity blocks the light in this spectral region is of capital importance to
understanding the energy balance in the atmosphere of these stars and,
ultimately, building reliable models to interpret observed fluxes. The model
atmospheres most used in spectroscopic analyses of individual stars and at the
core of population synthesis codes are based on calculations of
photoionization cross-sections from the 70's, when better data have been
available for a long time. We implement modern cross-sections in our
calculations of synthetic fluxes and model atmospheres, but the models need to
be confronted with observations. Detailed absolute fluxes for stars of known
effective temperatures and angular diameters can constrain the opacities
directly from observations. So far, such high-quality UV observations are
available only for the Sun, and this leaves some room for ambiguity between
line and continuum opacity. Observations with identical quality are possible
with STIS for a second nearby late-type star: Procyon A. This star is indeed
the only relatively unevolved late-type star for which an extremely precise
determination of its angular diameter is available.
================================================================================
Proposal Category: GO
Scientific Category: Cool Stars
ID: 9369
Title: A Direct Test for Dust-driven Wind Physics
PI: Alex Lobel
PI Institution: Smithsonian Astrophysical Observatory

We propose to perform with STIS a critical test of the physical mechanism of
wind acceleration by dust drag in cool stars. Spatially resolved spectra of
the circumstellar environment of Alpha Ori (M2 Iab) will directly test if
radiation pressure onto dust grains provides the momentum that causes the high
mass-loss rates (up to 10^-6 M_odot yr^-1) observed in asymptotic giant branch
and red supergiant stars. Terminal gas outflow velocities of 13-14 km,s^-1
are observed in Betelgeuse's circumstellar dust shell. However, the smaller
chromospheric outflow velocities (below 6 km,s^-1), point to an extended
region in the circumstellar environment where the wind accelerates. Stellar
wind theory suggests radiation pressure onto dust grains as the driving
mechanism that drags the gas outflow to these high terminal velocities.
Dynamic radiative transport calculations that fit the star's 9.7 Mum silicate
dust emission indicate that this wind accelerating region is located between
0.78" and ~3". We propose to use STIS to obtain a high-resolution spatial and
spectral raster scan across this region. These data can only be obtained for
this unique nearby supergiant with the exceptional capabilities of the STIS.
An increase of the observed asymmetry of