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PROJECT TITLE: Infrared Observations of Type IIn Supernovae
Project Description: Type II supernovae show hydrogen in their
spectra. The 'n' designates a narrow hydrogen line, one that is a few
hundred to a 1000 km/s wide at the continuum level, rather than the
more typical 10,000 km/s width. The IIn supernovae may be "normal"
massive supernovae exploding inside a dense shell from an earlier
phase of mass loss. These IIn supernovae can be bright at infrared
wavelengths due to dust formation or due to an infrared light echo.
We will reduce and analyze infrared photometry and spectroscopy of the
Type IIn supernova SN1995N to provide clues to understanding the IIn
phenomenon.
ADVISORS: Peter Garnavich, Eric M. Schlegel
INTERN: Alceste Bonanos
Since the discovery of first member of the collection of objects that
orbit near and beyond Neptune in what is now known as the Kuiper belt
or Trans-Neptunian belt, roughly 100 Kuiper belt objects have been
discovered. Although wide-field CCD cameras have dramatically
increased the discovery rate of Kuiper belt objects, more discoveries
provide very minimal scientific information if the orbits of these
objects are not reliably determined. Furthermore, some fraction of
the discovered objects are lost if follow-up astrometry over a
two-month arc cannot be obtained. Only about half of the
previously-discovered objects have multi-opposition orbits, and the
number of lost objects is climbing rapidly.
To avoid the loss of discovered Kuiper belt objects and to improve
the estimates of their orbital properties, we conduct follow up
observations of these objects. We conduct these observations with
SAO's 1.2-meter telescope at Mt. Hopkins in Arizona, with the Apache
Point Observatory's 3.5-meter telescope in New Mexico, and with the
Nordic Optical Telescope in La Palma, Spain. The procedure for
recovering and identifying a Kuiper belt object discovered in earlier
months is straightforward. Based on the preliminary orbit determined
by the Minor Planet Center from the discovery observations, we image
the field in which the object is expected to be. Typically the
predicted position is in error by no more than 1 arcminute if the
object is re-observed within 1-2 months of discovery. Each field is
imaged three times, with the exposures separated by about 1 hour.
Kuiper belt objects move at a rate of 3-4"/hour. Therefore, after
processing the images, each group of three exposures is aligned and
blinked in sequence to search for objects moving along the ecliptic.
Objects with an apparent motion greater than about 10"/hour can be
rejected as main belt asteroids. Astrometric positions are determined
using the USNO catalog. Those candidates that are confirmed on a
second night will be reported to B. Marsden and G. Williams of the
Minor Planet Center.
This Summer Intern project would involve participating in
one or two observing runs to observe recently discovered Kuiper belt
objects. It would also involve learning image processing
and astrometry techniques and applying them to the images obtained at
the telescope.
2) Abstract
PROJECT TITLE: Astrometric Observations of Kuiper Belt Objects
ADVISOR: Matt Holman
INTERN: Carolyn Ernst
On June 29, 1998, the Rossi X-ray Timing Explorer (RXTE), an orbiting
satellite which constantly monitors the 'x-ray sky', discovered a new
x-ray nova: XTE J2123-058. This nova consists of a neutron star with
a low mass (as yet unseen!) companion orbiting once every ~6 hours.
During outburst, the system brightened dramatically at optical (as
well as x-ray) wavelengths. Furthermore, the optical observations
showed truly remarkable modulations at the orbital period. It is
likely that we view the system nearly edge-on to the orbital plane, so
that the companion eclipses the x-ray emitting neutron star once every
orbit.
By late September of 1998 the system had faded back to its pre-nova
level. Four nights of photometry taken with the FLWO 48" telescope
and CCD camera in late September should allow an accurate measurement
of the 'inclination angle' of the system - that is, should allow us to
measure just how close to edge on we view this system.
The optical lightcurve can be compared to computer generated models of
the the expected modulations, which depend strongly upon the
inclination angle. This dependence comes about because stars in such
tight orbits are not round - their rapid rotation and extreme gravity
fields cause them to distort into egg-shaped stars. When such stars
are viewed side on, they appear brighter (because they are larger),
and when they are viewed end on, they appear fainter (because they are
smaller). By comparing the size of the observed modulation to that
generated for a variety of inclinations, once can determine the
inclination angle of the system.
3) Abstract
PROJECT TITLE: A new X-ray Nova: XTE J2123-058
ADVISOR: Michael Garcia
INTERN: Francisco Galvan
The project is to reduce and analyze extant CCD photometry of a young
cluster. The goal would be to access the faintest stars and determine
the true age of the cluster by comparing with isochrones, as part of a
more general program of trying to determine at what time protostellar
disks dissipate and planets begin to form. An intern's part in the
project would be to construct an observational HR diagram and
determine the best candidates for follow-up high-resolution and
infrared observations.
4) Abstract
PROJECT TITLE: Predicting Planetary Halo Candidates in Young Clusters
ADVISOR: Nuria Calvet
INTERN: Eric Hoversten
PROJECT TITLE: (Not yet available)
ADVISOR: Christine Jones
INTERN: Vit Hradecky
ADVISOR: James Phillips
INTERN: Naibi Marinas
"Spurious forces at launch of equivalence principle test mass."
Friction-like forces between the test mass and its launching stand will
cause the mass to rotate as it is launched, contributing to two types of
systematic error. The forces are not yet well understood by us, and
reading of the friction literature is required, along with testing of
plain launches with candidate materials, and perhaps design and
implementation of mechanisms that promise to reduce the frictional forces
markedly. Construction of simple electronic circuits to sense the test
mass positions may be required.
PROJECT TITLE: Principle of Equivalence Measurement (POEM)
Cataclysmic variables (CVs) are short period, interacting binary stars
in which one star is a red dwarf that is losing mass to the other star
which is a white dwarf. The accreting material can not fall directly
onto the white dwarf because it possesses too much angular momentum, so
it forms a disk around the white dwarf. Matter accretes onto the white
dwarf from the disk.
Time-resolved optical spectroscopy helps us to probe the conditions
within the accretion disk. The best probes of the accretion disk are
eclipsing CVs because the geometry of the system becomes known as soon
as an eclipse is detected. I have time-resolved spectroscopic data of
two eclipsing CVs (only one of which we'll tackle during the summer).
The data will be analyzed to study the light curve, emission line
light curves, and the radial velocity behavior of the emitting
material. The CV will be either the nova-like VZ Scl or the dwarf
nova WZ Sge. There are two epochs of data for VZ Scl, so we can
compare its behavior although the extra data will mean added work.
7) Abstract
PROJECT TITLE: Time-resolved Spectroscopy of an Eclipsing Cataclysmic Variable
ADVISOR: Eric Schlegel
INTERN: John Moustakus
We will find orbital solutions for low-amplitude spectroscopic binaries
discovered in a sample of 20 solar-type IAU radial-velocity standard
stars observed with the Digital Speedometers at the Harvard-Smithsonian
Center for Astrophysics. For all orbits the minimum mass for the
secondary is theorized to be within the border line between stellar and
substellar masses.
We consider the probability that the selected binaries have small enough
inclination angles so that their companions are above the substellar
limit. To do so we treat the 20 IAU standards as a sample drawn from a
population of binaries with a mass ratio distribution which does not
allow any substellar companions. We will calculate the probability that
such a sample could still have binaries with the low-amplitude orbits
actually found within the IAU sample. We will show that this probability
is small, depending on the specific mass-ratio distribution.
We will compare our detections with the null results of four very
precise radial-velocity searches for substellar companions. The
difference is indeed puzzling, but can be accounted for if just a
small fraction of the solar-type stars, of the order of a few percent,
have companions with masses near the substellar limit.
Using HST PC2 images, a summer intern will continue this work in
searching for low-mass companions around main sequence stars. This
work also will involve observing at the Oak Ridge Observatory.
8) Abstract
PROJECT TITLE: Spectroscopic Orbits for Binaries with Low-Mass Companions
ADVISOR: David Latham
INTERN: Margaret Pan
VLA data for several nearby galaxies have been obtained. Maps can be
produced which will show their radio continuum structures. This is of
particular interest in comparing with high resolution maps being
obtained at other wavelengths, including infrared, molecular gas, and
atomic gas. This work would be of interest in introducing the basic
principles of aperture synthesis, VLA imaging, AIPS processing, and
understanding various phenomena in nearby galaxies.
9) Abstract
PROJECT TITLE: Radio Continuum Images of Nearby Galaxies
ADVISOR: Paul Ho
INTERN: David Rothstein
Some HST/NICMOS images of protostars show bipolar nebulae. These
nebulae are formed when light from the protostar scatters in optically
thin cavities in the dense natal clouds that are presumed to be carved
by energetic outflows associated with the earliest phases of star form-
ation. However, other sources show complex nebulae that appear to have
been shaped by multiple outflows and precessing jets. The goal of
this project is to interpret the scattered light nebulae for two
particular objects, IRAS 04016+2610 and IRAS 04248+2612. The first
object appears to have two sets of bipolar outflows that have ruptured
the circumstellar envelope. The second object shows a point symmetric
nebulosity that may be related to the precessing jet associated with
this source. Using a fully three dimensional Monte Carlo scattering
code, we will generate 3D circumstellar geometries and determine how
these will appear in scattered light. Comparison of models with HST
observations will enable us to disentangle the complex geometries
associated with this phase of star formation.
10) Abstract
PROJECT TITLE: Shaping Protostellar Envelopes: 3D Modeling of HST Observations
ADVISOR: Kenny Wood
INTERN: David Smith
Located at a distance of ~800 parsecs, NGC 2264 is one of the most
populous nearby star-forming regions. Within 1 kpc of the Sun, there
is no other star-forming region with such a large, well-defined
membership covering a wide range of both mass and age, concentrated
into a relatively compact area on the sky. In March 1991 and
September 1992, the ROSAT HRI observed NGC 2264 in soft X-rays for 19
kiloseconds and 11 kiloseconds respectively. In total, 74 X-ray
sources were identified in these X-ray images, the majority of which
appear to be associated with known cluster members. The primary goal
of these X-ray observations is to derive X-ray luminosities for a
large sample of pre-main sequence stars covering a wide range of both
mass and age. In the time since these ROSAT observations were made,
we have assembled an extensive database of ground-based optical
spectroscopy, optical and near-infrared photometry, and photometrically
determined rotation periods (using star spot modulation) for hundreds
of stars in this cluster. These data, when merged with the X-ray data,
will allow us to explore the relationship between rotation period and
coronal activity in very young stars. This in turn will allow us to
probe the nature of stellar magnetic dynamos in the pre-main sequence
phase of evolution. Because our sample consists of both Classical and
weak-lined T Tauri stars, we will also be able to to determine if
external influences, such as the presence of a circumstellar material,
are causing an attenuation of X-ray emission and if there is a relation
between rotation period and the presence of a CS disk.
The primary goal for the summer intern will be merge the X-ray
database with the extensive optical and IR photometry, spectral type,
and rotation period databases for this region (there will also be some
verification that the original X-ray analysis is up-to-date and
complete). The final product will be a dataset which will be used for
the subsequent analysis of coronal luminosity versus mass, age, and
rotation period. Once the database is complete, the intern will take
part in that analysis. The intern will be expected to make use of
scientific workstations (running the Unix OS), manipulate large data-
bases on-line, and gain familiarity astronomical coordinate systems
and object naming schemes. The intern will also gain familiarity with
scientific plotting packages and will likely do some scientific
programming (in FORTRAN or C). This work will ultimately be used in a
refereed paper. The possibility exists to present a poster paper at
a professional meeting.
11) Abstract
PROJECT TITLE: Coronal Activity in Low-Mass Pre-Main Sequence Stars
ADVISOR: Brian M. Patten
INTERN: Heide Tebbe
Distant X-ray clusters beyond redshift z=0.5 appear to have fewer
galaxies (i.e. they are poorer) compared to nearby clusters with
similar X-ray luminosities.
However, different galaxy counting methods were used in the nearby and
distant cluster studies. Galaxies in nearby clusters were counted by
eye on wide-field photographic plates, while the distant cluster
galaxies were counted by computer on narrow-field, CCD images. We
will measure richnesses for a sample of 30--40 nearby clusters imaged
on the digitized Palomar Observatory Sky Survey using the same computer
programs and methods used to count galaxies in CCD images of distant
clusters.
Our goal is to produce a sample of nearby clusters with well understood
richnesses and X-ray properties, that can serve as a low-redshift
template for high redshift cluster evolution studies.
We will construct a catalog of cluster richnesses (galaxy counts) for a
sample of nearby, X-ray-selected clusters using the same counting
methods used to study very distant clusters. The catalog of cluster
galaxy counts made from DPOSS images will serve as a low-redshift
template for studies of high redshift clusters.
12) Abstract
PROJECT TITLE: Richnesses of Nearby X-ray Clusters
ADVISOR: Brian McNamara
INTERN: Kathryn Whitman
1) Alceste Bonanos
Wellesley College
We analyze photometric and spectroscopic observations of the supernova
SN 1999by in the spiral galaxy NGC 2841. CCD images were taken with
the 1.2 m telescope and spectra with the 1.5 m Tillinghast telescope
at the Fred Lawrence Whipple Observatory in Arizona. SN 1999by reached
maximum in B on UT 1999 May 10 (JD 24501308.5 ± 1) with B = 13.80
± 0.02 and V = 13.36 ± 0.02, as indicated by 20 photometric
observations between May 6 and June 21. The light-curves obtained in
the U, B, V, R and I filters were compared to the templates of the
subluminous type Ia SN 1991bg. SN 1999by appears very similar to SN
1991bg; it has Δm15(B) = 1.87, versus 1.93 for SN 1991bg,
making SN 1999by one of the most sub-luminous type Ia supernovae ever
observed. The ratio of the spectral lines at 580 and 615 nm is small,
consistent with being under-luminous. Models indicate that the
spectrum contains deep titanium absorption bands, especially in the
blue.
--- Advisors Peter Garnavich and Eric Schlegel
Since the first direct detection of a Kuiper belt object (KBO) in 1992, over 200 of these objects have been discovered by a number of groups. Available observations and theoretical models suggest that the Kuiper belt is comprised of three principal populations: objects, like Pluto, in Neptune’s mean motion resonances, objects with more distant non-resonant orbits, and objects with highly eccentric orbits that may permit occasional close approaches with Neptune. The discovery of KBOs alone does little to advance our scientific understanding of their distribution and dynamical evolution unless sufficient follow-up observations are available to make unequivocal determinations of their orbits, which typically requires intermittent observations over at least a 2-year baseline after their initial discovery (due to their very long orbital periods).
We describe a continuing program to provide consistent follow-up astrometry of KBOs. This program involves a number of observers using a variety of telescopes. Here we report results from the F. L. Whipple Observatory’s 1.2-meter telescope on Mt. Hopkins, Arizona, the Apache Point Observatory’s 3.5-meter telescope in New Mexico, and the 2.6-meter Nordic Optical Telescope in La Palma, Spain.
--- Advisor Matt Holman
A red interloper has been detected in the vicinity of the faint Tremendous Outburst Amplitude Dwarf (TOAD) AL Comae, with a 3.95 arc-seconds approximate separation between the center of both systems. New infrared photometry was taken with the 2.1m IRIM camera on the observation nights of July 11 and 12 of 1997. Analysis of this data shows that the previously published K band magnitude for AL Comae is not 15.8 but rather 17.9, with a V-K magnitude similar to that of G type star. We conclude that previous photometric analysis of AL Comae was contaminated by the close red dwarf. This suggests that the results from the optical spectral analysis by Howell et al. might have been contaminated as well. A new spectorscopic analysis in the optical range has been done on data taken with the 4m MMT on February 7, 1997. These new analyses agrees with our new photometric results. We re-analyzed the WHT data published in Howell et al. taking the red neighbor into account, but the re-analysis seemed to be consistent with that of the published paper.
--- Advisor Mike Garcia
We present 1.6 micron and 2.05 micron images of IRAS 4381+2540 obtained
with NICMOS2 on board the Hubble Space Telescope. IRAS 4381+2540 is a
Class I object in Taurus still surrounded by an infalling envelope. The
high resolution NICMOS images reveal that the source is a binary, with a
mean separation of approximately 80 AU; both members of the binary are
immersed in a common envelope. Near-infrared scattered light image models
for the dusty envelope used in tandem with spectral energy distribution
calculations, including the dust thermal emission, allow us to constrain
estimates of system inclination, envelope density and the amount of
flattening in the initial cloud of IRAS 4381+2540 further than with either
technique alone. We also show that a small polar cavity, suggested by the
images, can exist within constraints of the calculations. This research
was made possible by the SAO Summer Intern Program funded in part by NSF.
--- Advisor N. Calvet
We use galaxy catalogs resulting from the digitization and automated
processing of the second generation Palomar Sky Survey plates
calibrated with CCD images in Gunn-Thuan g, r, and i bands, ASCA
spatially resolved spectroscopic X-ray observations and ROSAT PSPC
images to constrain total and gas mass-to-light ratios, gas mass
fraction, baryon mass fraction and the ratio of total to luminous mass
for a sample of 8 nearby relaxed galaxy groups and clusters. They are
A262, A426, A478, A1795, A2052, A2063, A2199 and MKW4s.
Under the assumption of hydrostatic equilibrium and spherical
symmetry, we can measure the total masses of clusters from their
intracluster gas temperature and density profiles. Previous cluster
mass estimates assumed the gas is isothermal, however ASCA
spatially resolved spectra show the gas temperature decreases with
increasing distance from the center. By comparison, the isothermal
assumption results in an underestimate of the total mass at small
radii, and an overestimate at large cluster radii. The discrepancy
between mass-to-light ratios obtained using virial mass estimates and
X-ray mass estimates is thus increased. We argue that the virial mass
estimate is a less reliable one, subject to systematic errors due to
limited cluster volumes sampled and possible galaxy velocity
anisotropies.
We obtained luminosity functions for the clusters in our sample using
the digitized Palomar Sky Survey data calibrated with CCD images. To
correct for contamination by background and foreground galaxies, we
use color information to reject obvious non-members and subtract
background galaxies statistically. We then estimate the total cluster
luminosity using Schechter function fits to the galaxy catalogs.
The measured mass-to-light ratios are ∼100Modot / Lodot,
assuming H0 = 50 km/s -1Mpc-1.
This, along with a high baryonic fraction, are indicative
of a low density universe with Ω∼ 0.2.
Vit Hradecky was partially supported by the Caltech SURF fellowship.
--- Advisors C. Jones and H. Donnelly
A Galilean Equivalence Principle test is being constructed at SAO by
Reasenberg and Phillips that requires a precision distance laser gauge
faster by a factor of 1000 than ones used in previous tests. A vacuum
chamber containing test masses will move along a vertical path. Each
mass will have a retro-reflector used at one end point of a laser
gauge that will measure the distance between the masses. To take
accurate measurements for this experiment, the laser gauge needs a
measurement capability of 0.2 nm in 10 ms. During the Summer at SAO,
the laser gauge was tested for time response and noise by obtaining a
noise spectrum and calculating the 3dB frequency of the gauge. The
system also needed an increased frequency shift to allow the gauge to
follow large distance changes. By redesigning the optic path of the
laser, we were able to obtain the desired frequency shift for the
experiment. This new improved system will be presented.
--- Advisor Jim Phillips
We present a spectrophotometric analysis of the eclipsing nova-like
variable VZ Sculptoris. The data include 132 time-resolved spectra
obtained with the 4-meter CTIO telescope in addition to 277
time-resolved spectra obtained with the KPNO 2.1-meter telescope.
Although Doppler tomography, light and radial velocity curves of the
prominent HI, HeI and HeII λ4686 emission lines suggest the
existence of an accretion disc, a program to model the emission-line
profiles to better determine the geometry of the system is currently
underway. We discuss the possibility that VZ Sculptoris belongs to a
currently unexplained subclass of nova-likes called the SW Sex stars.
--- Advisor Eric Schlegel
A new spectroscopic orbit was derived for the double-lined binary
G209-35 (HD 195987) based on 52 spectra taken over the past 16
years. An orbital inclination of [0in][l]90.90circ2 ±
[0in][l]6.6circ0 was derived for G209-35 from the
Hipparcos intermediate results; the new orbit and this inclination
yielded component masses of 0.7907 ± 0.0143 Modot and
0.6297 ± 0.0069 Modot. Comparison of the G209-35 components
to recent stellar isochrones and evolutionary tracks showed some
disagreement between the models and the G209-35 data. In particular,
the magnitude difference between the G209-35 primary and secondary was
consistently larger than the models' predictions for stars of the
derived masses. Outside of this, the G209-35 data were in closest
agreement with interpolations of models computed by Baraffe et
al. (1997).
--- Advisor David Latham
We use the technique of methane-band imaging to search for faint companions to fourteen nearby stars. Most of the stars in the sample have previously discovered Doppler velocity companions at several AU or less, but our method is sensitive to companions at larger orbital distances. We develop various forms of median subtraction to remove the extremely high and often saturated primary star point-spread functions and to uncover faint objects hiding in their wings. We report the discovery of an apparent companion at 5.0'' from the star BD-04782 (corresponding to a minimum orbital radius of 100 AU); however, this potential companion does not seem to have an atmosphere that would identify it as a methane brown dwarf (Teff < ∼1600 K). Upper limits are set on the near infrared brightness of any companions in the data set which may have escaped our detection.
--- Advisors M. Gurwell and P. Ho
Ground based imaging polarimetry and recent WFPC2 and NICMOS images of
protostars have revealed very complex scattered light patterns. We
are conducting detailed 3-D radiation transfer modeling of these
sources to investigate the effects on image morphology of multiple
illuminating sources and 3-D infalling envelopes that have been shaped
by multiple outflows. We present model images for IRAS 04016+2610,
IRAS 04248+2612, and T Tau. We find that the scattered light pattern
of IRAS 04016+2610 can be reproduced by scattering in an envelope with
cavities carved by two sets of bipolar outflows, suggestive of an en
embedded binary system. IRAS 04248+2612 can be modeled with an
envelope with a single bipolar cavity with the lower cavity offset
from the upper. This break of axisymmetry is not surprising given the
large precessing jets that are associated with this source. For T Tau
we have constructed scattered light models where the illumination of
the surrounding envelope is by a binary with each source having a
small circumstellar disk. We find that the asymmetries in the WFPC2
image of T Tau can be reproduced if the disks in the binary system are
misaligned. Our models demonstrate the necessity of a 3D scattering
code in analysis of the complex geometries inherent in protostellar
collapse.
--- Advisor Kenny Wood
We present the preliminary results of an analysis of ROSAT images in
the region of the populous young (age ∼3 Myr) star-forming region
NGC 2264. The cluster was imaged with the ROSAT HRI in two sets of
pointings -- one set near the central region of the cluster, centered
on the star LW Mon, and the other set in the southern part of the
cluster, centered near the star V428 Mon, just south of the Cone
Nebula. In total 113 unique X-ray sources have been identified in the
ROSAT images with signal-to-noise ratios greater than 3. The limiting
luminosities (log Lx(ergs/sec)) for 3-sigma detections are estimated
to be 30.18, 30.23, and 30.08 for the northern field, southern field,
and overlap region between the two fields respectively. Extensive
optical photometry, classification spectroscopy, and proper motions,
obtained from recent ground-based surveys of this region, were used to
identify the most likely optical counterpart to each X-ray source.
Although most of our X-ray selected sample appears to be associated
with NGC 2264 members, we find that the vast majority of the cluster
membership was undetected in the ROSAT HRI survey. The X-ray
cumulative luminosity function for solar-mass stars NGC 2264 shows
that most of the low-mass members probably have X-ray luminosities
similar to those seen for the X-ray brightest members of older
clusters such as IC 2391/IC 2602 (age ∼50 Myr) and the Pleiades
(age ∼100 Myr). This research was funded in part by the SAO
Summer Intern Program and NASA grant NAG5-8120.
--- Advisor Brian Patten
We have measured the surface density of galaxies on R-band Digital
Sky Survey images toward 18, redshift z < 0.1, X-ray-selected Abell
clusters. Our automated galaxy counts within 3 Mpc apertures agree
well with Abell's counts for richness class 0--2 clusters. However,
we find a smaller scatter in the X-ray luminosity--cluster richness
relation using galaxy counts within smaller, 1.0--1.5 Mpc apertures
compared to counts within the 3 Mpc Abell radius. We find that galaxy
counts for distant clusters are likewise most accurate within ≤
1.5 Mpc apertures, where the ratio of cluster galaxies to
background/foreground galaxies is maximal. An expanded sample of
nearby clusters selected and analyzed similarly will provide a basis
for comparing nearby and distant (i.e. z > 0.5) X-ray clusters to
study evolution.
--- Advisor Brian McNamara