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1) Emily Alicea-Muñoz's project abstract
PROJECT TITLE: What's Happening in the Oldest Stars?
ADVISOR: Andrea Dupree
INTERN: Emily Alicea-Muñoz
The oldest stars in our galaxy 'should' be pretty boring by now --
having evolved beyond their young stages with rapid rotation, magnetic
dynamo activity, and hot outer atmospheres. However, we find
unexpected signatures of stellar activity in these old giants: H-alpha
emission appears in their spectra and it varies. Ultraviolet Mg II
emission is found that signifies a stellar chromosphere -- and
material even hotter than the surface layers. If these are truly
signatures of magnetic processes, our theoretical models of dynamos
and their evolution are severely challenged (a polite way of saying
they may be wrong). Additionally the oldest stars now represent our
galaxy when it was young - and so give insight into galaxy formation
and evolution.
We have a unique set of multiple optical H-alpha spectra of metal
deficient field giants acquired over a year of observations. Emission
is present in many of these spectra. We want to find out when the
emission wings appear, when they are strong or weak, or asymmetric.
Is the strength or asymmetry periodic? Does it vary randomly? Are the
brightest stars more (or less) variable? Can we deduce whether the
emission is of magnetic origin or if the source is hydrodynamic? What
dynamics are implied by the line profiles?
Higher levels of these chromospheres can be detected in ultraviolet
spectra of the same or similar stars from HST/STIS, showing strong
emission from Mg II. (These data have already been taken.) We want to
know how the flux changes among stars of different temperature and
luminosity. How do the flux levels compare to younger and more
metal-rich objects?
The reduction and analysis of H-alpha and ultraviolet spectra, and
comparison to other objects is a good summer project. A computationally
inspired student could take this even further and calculate the line
profiles and begin to model the stars in detail so as to qualitatively
interpret the spectra. What will we learn from this? We will discover
what luminous old stars are doing. Are they pulsating? Are they driving
off winds in the process? Have their dynamos died? Metal-deficient field
giants are surrogates for giants in globular clusters in our galaxy and
others - giants that will only be studied with the next generation of
ground and space based telescopes. So these studies provide a strong
fiducial sample - a baseline on which to build future studies.
This program is first of all computer intensive. You will become
facile in IRAF (a software suite for reducing astronomical data.) You
will learn about spectra, spectral reductions, wavelength calibrations,
signal to noise ratios, and flux extractions. You will also learn to
construct programs in the IDL language that is used for analysis, data
presentation, even movies of our time sequences (black/white and color).
You will dig into the astronomical literature - using query tools in the
Astronomical Data System (ADS), SINBAD, VIZIER - and major catalogues such
as Hipparcos on line to track down parameters of the targets and find out
what has been done earlier. You will make comparisons between these
target stars and others with similar characteristics. You will think of
the questions yet to be answered and try to devise ways to answer them.
You may want to address some problem computationally with semi-empirical
modelling using existing sophisticated radiative-transfer codes. We may
write proposals to use other telescopes on the ground or in space to
extend our sample or to probe different atmospheric levels.
2) Mia Bovill's project abstract
PROJECT TITLE: The Chemistry and Dynamics of the Molecular Outflow in BHR71
ADVISOR: Tyler Bourke
INTERN: Mia Bovill
The process of forming a star is not well understood, but they are the
basic astronomical units of our Galaxy. We do know that stars form
via gravitational collapse of a gas cloud, but when Astronomers first
tried to observe this process, they instead discovered very powerful
collimated outflows. These outflows have a major effect on the
surround gas cloud, creating shocks which destroy dust grains and may
be the process that ends the stellar formation.
In order to study the effects of outflows on their parent clouds, we
have obtained mm/submm data toward the outflow from the very young
protostar in BHR 71. This data has been obtained with the SEST in
Chile, the CfA submillimeter telescope AST/RO at the South Pole, and
the NASA satellite SWAS (http://cfa-www.harvard.edu/swas/). The
protostar lies in an isolated cloud, and so the effects of its outflow
on the cloud can be studied without confusion. The outflow is one of
a few to show extreme chemical signatures of the shocks, such as
greatly increased chemical abundances.
The aim of the project is to analyze these data and compare the results
with chemical evolution models, which will allow us to trace the history
of the outflow and its affects on the cloud. Complementary infrared
data tracing the hot-spots in the shocks will also be used.
(see BHR 71 )
3) Richard Cool's project abstract
PROJECT TITLE: Design and Construction of Calibration Equipment for Cryogenic Thermal Sensors
ADVISOR: Eric Silver
INTERN: Richard Cool
The cryogenic x-ray detector research group is seeking a summer
student to assist with the development of a balloon payload for
studying the hard x-ray emission and the processes of nucleosynthesis
in supernova remnants. The student will learn cryogenic and
spectroscopic techniques and participate in all aspects of the
construction and testing of the instrument.
4) Robert Friedman's project abstract
PROJECT TITLE: X-ray Sources and Globular Clusters in NGC 4472 and NGC 4486
ADVISOR: Rosanne DiStefano
INTERN: Robert Friedman
This is a pilot study that would help us to prepare for a larger
archival data project we have proposed. The full archival project
includes 29 galaxies; this pilot project would include 2-4
galaxies. The work on these 2-4 galaxies should lead to a publication
in the Astrophysical Journal or a comparable publication.
There are a number of intriguing questions about galactic populations of
GCs. It has been suggested, e.g., that, in elliptical galaxies,
X-ray binaries form preferentially in GCs. (See, e.g., White 2001).
Studying the fraction of X-ray sources in elliptical galaxies that
reside in GCs provides a way to test this hypothesis. Such a test was
carried out for NGC 1399 by Angelini, Lowenstein, & Mushotsky (2001).
While the results seem to speak in favor of the hypothesis, only a
larger sample of galaxies can really resolve the issue. Differences
between the luminosities of GC X-ray sources in elliptical vs spiral
galaxies have also been suggested (see, e.g., Angelini et al. 2001),
but cannot yet be well-established.
Optical studies of extragalactic star clusters have been going on for
a long time: Hubble (1932) identified about a hundred globular cluster
candidates in M31 shortly after showing that galaxy to be an external
stellar system. Today, globular cluster systems have been detected in
more than 200 galaxies. In Local Group galaxies, GCs are marginally
resolved in ground-based images, and are well-enough resolved in HST
images that color-magnitude diagrams can be produced. GCs in more
distant galaxies, such as those in the Virgo and Fornax clusters can
be individually detected and spectroscopically studied with 8-m class
telescopes.
HST imaging, with its high spatial resolution, has dramatically
improved the precision with which the galaxy background can be
subtracted, which in turn improves the detectability and photometry of
GC candidates. The field of extragalactic star cluster research has
been reinvigorated by the combination of space-based imaging,
ground-based spectroscopy with large telescopes, and theoretical work
on galaxy formation. New results are providing an increasingly
detailed view of the early stages of galaxy assembly.
We will use optical images of a small set of external galaxies to
identify globular clusters, and will then use X-ray data to identify
those clusters harboring X-ray sources.
This procedure will allow us to study, for different galaxy types,
(1) The fraction of the galaxy's X-ray sources in GCs;
(2) The fraction of galaxies with GC X-ray sources having Lx > 1037
ergs/s.
(3) GCX-ray source luminosity functions.
We will naturally try to understand the implications of our results
for the formation of GCs and for the formation of X-ray binaries
within the dense cores of clusters. In addition, several other lines
of research should be followed -- for example studying correlations
between nebulae and X-ray sources in external galaxies.
5) Alex Hill's project abstract
PROJECT TITLE: A Study of the Structure and Dynamics of the Virgo Cluster
ADVISOR: John Huchra
INTERN: Alex Hill
A new complete sample of galaxies in the vicinity of the core of the
Local Supercluster has been assembled from the 2MASS survey. We have
complete redshift information for all galaxies brighter than K=12.0 in
the region 11.5 to 13.5 hours RA and +0 to +24 degress declination.
This data will be used to (1) construct the K-band luminosity function
for the Virgo cluster (RA 12.5h, dec +12 degrees), (2) map the galaxy
density distribution for the cluster, and (3) study the kinematics of
the supercluster core and the individual clusters and sub-clusters and
groups of galaxies that make up that region of the local supercluster.
Information on redshift independent galaxy distances will be assembled
from the literature and from IR Tully Fisher measurements enabled by
the 2MASS photometry.
6) Holly Maness's project abstract
PROJECT TITLE: X-ray Spectra of Chandra-Observed Planetary Nebulae - Revisited
ADVISOR: Saeqa Vrtilek
INTERN: Holly Maness
We have observed several young Planetary Nebulae with Chandra and have
several others with approved time. The routine appearance of X-rays
in the interiors of young PNs (first detected conclusively with
Chandra) provides strong constraints on models of their formation and
evolution. For example, according to Mellema & Frank (1995) the
interaction of a fast (∼1000 km s-1) wind from the central
white dwarf with slower-moving (∼ 15 km s-1) material
ejected during the star's asymptotic giant branch phase will result in
strong shocks. Magnetic fields can then act to regulate the cooling
of the shock-heated gas, such that most of the energy released is in
the 1 keV range (Soker 1994).
The student would compare the X-ray morphologies of the nebulae
recently revealed by Chandra observations (Kastner et al. 2000, 2001)
with the spatial distribution of visual extinction as shown by optical
and near-IR observations. They would test several different
mechanisms that can be responsible for the low X-ray temperatures
observed in PNs. Possibilities include collimated outflows with
velocities of 300-500 km/s, highly non-uniform extinction within the
PNs, and mixing of hot and nebular gas.
7) Joannah Metz's project abstract
PROJECT TITLE: What Good Are Direct Detections of Extrasolar
Giant Planets with Ground-based Interferometers?
ADVISOR: Marc Kuchner
INTERN: Joannah Metz
The known extrasolar planets were all discovered indirectly, by
observing the stars they orbit. Directly detecting photons from
extrasolar planets may require giant infrared interferometers, like
the Keck Interferometer, the Large Binocular Telescope, or the
proposed 20/20 interferometer. Direct detection sounds exciting, but
what can these interferometric measurements teach us about the
planets? Can they constrain the planet's orbit or mass? Can they
help us decide how big or bright the planet is?
Take the list of known extrasolar giant planets and simulate how they
will appear to a giant infrared interferometer. Then use the
simulated data to try to constrain properties of the planet-- its
orbit, its mass, its size, its temperature, etc. The results will
help us decide how to use the current generation of interferometers,
and possibly tell us what we should build next. This topic is "hot"
right now--billions of dollars will probably be spent on
planet-finding instruments in the next ten years. This project should
yield a widely-read published paper.
8) Anandi Salinas's project abstract
PROJECT TITLE: An Observation of XY Arietis and TX Columbae with Chandra
ADVISOR: Eric Schlegel
INTERN: Anandi Salinas
Cataclysmic Variables are interacting binary stars; the two stars are
a white dwarf and a red dwarf. The red dwarf donates mass via a mass
transfer stream. In magnetic CVs, the field dominates the mass
dynamics at a radius appropriate to the field strength of the white
dwarf. For polars (= high-field CVs), the field strength dictates the
dynamics from the moment the material leaves the red dwarf. For
intermediate polars, the magnetic field strength is insufficient to
dictate the dynamics at the red dwarf's location. There are two
implications: the two stellar components are not magnetically locked
and the mass transfer stream may create an accretion disk outside of
the magnetic domination radius.
Chandra has serendipitously observed the IP TX Col for about 50 ksec.
The spin period is about 2 ksec and the orbital period is about 20.5
ksec; the data represent about 25 spin periods and about 2 orbital
periods. Chandra's orbit is elliptical, so long observations are
generally uninterrupted by earth block or radiation zones. We will
extract phase-resolved spectra and light curves for this CV.
9) Tristan Smith's project abstract
PROJECT TITLE: A Glimpse into the Future of High Energy Observatories
ADVISOR: Suzanne Romaine
INTERN: Tristan Smith
Everyone is aware of the great success of Chandra -
and a large part of that success is due to the quality
of the optics. We are currently working on multilayer
coatings which will allow the extension of the energy
range of the next X-ray mission (Constellation-X) to
100 keV. We would like to begin a program to investigate
optics for X-ray interferometry -- which will most
likely be a future X-ray mission.
The proposed project will familiarize the student with
X-ray optics in general - the problems and solutions
and why X-ray interferometry is necessary. We will
investigate what has been done to date, what hurdles
must be overcome and delineate a plan for fabricating
and testing such optics.
10) Daniel Wik's project abstract
PROJECT TITLE: Optical Activity Rates in X-ray-Selected Galaxies
ADVISOR: Paul Green
INTERN: Daniel Wik
The ChaMP project is obtaining a sample of FAST spectroscopy of
optically bright serendipitous Chandra sources. This bright local
sample probes significantly lower fx/fopt ratios than previous such
samples. For galaxies, we will define a sample of low luminosity AGN
(LLAGN). The intern will test for the fraction of X-ray-detected
galaxies that contain signatures of AGN activity, offering an
important constraint on models of black hole formation and accretion
and AGN lifetimes. The fraction and type of off-nuclear sources in
such a sample is also of great interest, to study the nature of these
sources - super starclusters, beamed X-ray binaries, intermediate mass
black holes, or perhaps even background AGN. Stars found in the
sample at the lowest fx/fopt ratios may be useful to probe activity in
new regions of the HR diagram - high mass objects with weak convection
zones, or older convective stars whose dynamos are wearing down.
A preliminary sample of at least 30 spectra are available for analysis,
with about 20 more due to be received this summer. The FAST spectra
come already dispersion-corrected. We propose a summer intern work
with us to flux-calibrate the spectra (using IRAF), to classify the objects.
The intern will help define full source classifications using
the available information - line widths and strengths, as well as
flux ratios and morphology from our existing X-ray and 3-color
optical imaging.
1) Emily Alicea-Muñoz
University of Puerto Rico
--- Advisor: Andrea Dupree
Abstract:
Globular cluster red giant stars are thought to experience
mass loss in their evolution along the red giant branch
(Iben 1983). However, no such mass loss has ever been
directly observed. Emission wings around the Halpha
spectral region have hinted at circumstellar material
(Cohen 1976). Asymmetries and time variations of these
emission wings have hinted that there are pulsating
motions in the chromosphere of the red giants, which
can lead to the unobserved mass loss (Dupree et.al.
1984), but no single star has been observed to confirm
this. Globular cluster red giants are optically faint,
therefore we have chosen to study bright field red
giants (Carney 1993) to see if signatures of pulsations
can be detected. Eight metal deficient field red giants
were chosen for spectroscopic analysis. Four stars
with small metal depletions (-0.9<[Fe/H]<-1.8) were
analyzed, one of which (HD232078) shows time-varying
asymmetries in the emission wings surrounding the Halpha
region of the spectrum. This hints at a pulsating chromosphere
in that star. A period of around 50 days was determined
for the pulsations. Another star (HD6833) shows no
pattern in the asymmetries, therefore hinting at no
chromospheric movement. The ratio of the intensities
of the emission wings for the third star (HD110281)
show clear signs of pulsation, with a period of close
to 60 days. The last star (HD103036) shows some hints
of chromospheric movements; however, analysis of the
Halpha velocity with respect to the chromosphere shows
no clear pattern. Stars with greater metal deficiencies
(-1.92<[Fe/H]<-2.6) have also been analyzed. One of
them (HD29574) shows signs of peculiar chromospheric
motions. The last star analyzed to date (HD165195)
shows signs of pulsations. Data taken on different
times of the year gives us different results, and two
different periods of pulsation were determined: a 40-day
period of chromospheric pulsations, and a 20-day period
of outer-chromosphere pulsation. Two more stars (HD122563
and HD110184) will be analyzed in the near future.
This is the first spectroscopic analysis of time series
of spectra done for these stars. We have compared characteristics
of the stars that show signatures of pulsation with
those that do not to see if emission and motions are
detected only in the most luminous objects (Smith
et.al. 1988). Our results so far tell us that emissions
and motions are detected in stars whose absolute
magnitude is brighter than MV = -1.8. We
have also been able to demonstrate periodic variability
in the brightest stars for the first time.
Abstract:
------- Text of final project abstract is not available.
Shocking Chemistry in a Protostellar Outflow
------- Advisor: Tyler Bourke
Abstract:
------- Text of final project abstract is not available.
Development of Balloon Payload for Studying Hard X-Ray
Emission and Nucleosynthesis in Supernova Remnants
------- Advisor: Eric Silver
Abstract:
Globular Cluster X-Ray Sources in External Galaxies
------- Text of final project abstract is not available.
------- Advisor: Rosanne DiStefano
Abstract:
------- Advisor: John Huchra
A Study of the Structure and Dynamics of the Virgo Cluster
Abstract:
This paper is a study of the Virgo cluster using a
complete sample of galaxies from the Two Micron All-Sky
Survey (2MASS) with photometry and redshifts. We use
the infrared Tully-Fisher relation to determine distances
to spiral galaxies in the cluster. Combined with distance
obtained by surface brightness fluctuations (compiled
from the literature), we establish distances to seven
clouds near the Virgo cluster, one of which (the W
cloud) is probably background. Using these distances,
we construct the K-band galaxy luminosity function of the
cluster.
Abstract:
Planetary Nebulae
------- Text of final project abstract is not available.
------- Advisor: Saeqa Vrtilek
A Model for Exozodiacal Debris Disks
Abstract:
Zodipic, an IDL program, creates 2-D models of circumstellar
debris disks. The program models the 10 micron silicate
dust emission feature detected in observations of circumstellar
grains. Zodipic calculates realistic temperatures
for the dust and fluxes emitted by the grains in a
debris disk by solving the thermal equilibrium equations
taking into account the wavelength dependent absorption
coefficients. We calculated these coefficients with
the program Dusty using Mie Theory and the optical
constants of Draine and Lee (1984) for a range of grain
sizes and wavelengths. The program includes accurate
stellar fluxes by use of the Kurucz model of stellar
spectra. We then used the Zodipic model to attempt
to match several resolved spectra from Beta Pictoris
and to estimate the typical grain size of dust particles
orbiting the star.
A Chandra Observation of the Intermediate Polar TX Col
------- Text of final project abstract is not available.
------- Advisor: Eric Schlegel
Investigation of Optics for X-ray Interferometry
Abstract:
With the 1999 launch of NASA's Chandra X-ray Observatory
and ESA's XMM-Newton and established science goals
for future missions, it is time to consider designs
for X-ray optics which differ radically from the long
established Wolter type optics. Chandra's <∼0.5''
angular resolution will stand as the highest angular
resolution through the future Constellation-X and Xeus
observatories, both planned for the end of this decade.
Both of these missions take high collecting area at
the expense of angular resolution. This decision might
indicate a departure for X-ray observatories: from
a general purpose observatory, with high throughput,
spectral and angular resolution, to so-called 'mid-ex'
missions, with specific science goals necessitating
designs which have specific strengths.
Two designs, Fresnel Lenses and X-ray interferometry,
present optical systems which, theoretically, can reach
micro-arcsecond angular resolutions. Many obstacles
have stood in the way of realizing the possibility
of these designs. Both present the challenge of separated
spacecraft 'formation flying'. This technology is
being developed currently by NASA in it's Origins Program
in a pathfinder for that program, StarLight, planned
to be launched in 2006. ESA is also participating
with its own pathfinder formation flying spacecraft,
Smart 2, also planned to launch in 2006. Furthermore,
because of the high resolutions and resulting small
fields of view, collecting area might present a problem.
Efficient Fresnel Lenses require refraction, which
present problems for the soft X-ray region (<∼ 1 keV),
in which interesting information is contained
for high redshift objects. Interferometry requires
miniscule length tolerances, on the order of nanometers,
which require large advances in current technology.
In this paper we present the state of the art of X-ray
observatories and suggest a few practical ideas for
future missions.
------- Advisor: Suzanne Romaine
Abstract:
Classification of Serendipidous Chandra Sources
------- Text of final project abstract is not available.
------- Advisor: Paul Green