My Personal Homepage
Webpage for ASTR 110-07A Lab
Research
I would like to gratefully acknowlegde the support of the Space Grant
Foundation, which has supported me in some fashion for most of the projects
listed below. I am currently supported by the New Mexico Space Grant
Foundation for the Spring and Fall of 2009.
The Mystery of Cataclysmic Variable Secondaries
In the Fall of 2008 I began working with Dr. Tom Harrison on several questions
concerning the nature of the secondary stars in cataclysmic variables.
Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI)
The Summer of 2007 was spent at Goddard Space Flight Center, working with Dr.
Brian Dennis and supported by the NASA Summer Intern Program and the New Mexico
Space Grant Foundation. RHESSI studies the dynamics of solar flares and
sunspots in in x-ray and gamma rays. My tasks for the summer focused on not
only learning the basics of X-ray and gamma ray spectroscopy, but using RHESSI
in conjunction with another instrument on India's GSAT-2, the Solar X-ray
Spectrometer (SOXS) to look at solar flares observed with both instruments.
RHESSI's lower energy sensitivity is hampered by instrumental effects, whereas
SOXS is not. It was hoped that SOXS could be used to either calibrate RHESSI's
lower energy response or to suppliment it, but significant problems in the
calibration of the SOXS data itself prevented this. The experience was
valuable, however, because of how much I learned about X-ray spectroscopy as
well as giving me an experience at working at a NASA center.
Star Formation Histories
In the Fall of 2006 I began work with Dr. Jon Holtzman here at NMSU on several
questions of chemical evolution and the history of star formation of our solar
neighborhood. Star formation histories of a given galaxy can be obtained by
fitting theoretical models (isochrones) to match the distribution of stars seen
in the color-magnitude diagram (CMD) of our local neighborhood. To increase
the robustness of the fits, extra information such as the chemical abundances
of some of the stars in the CMD could be used. To achieve this, I first got my
feet wet by using the echelle spectrograph at the Apache Point Observatory 3.5
meter telescope to complete observation of a set of red giants. I then began
the development of a program to fit theoretical isochrones to the CMD of our
local neighborhood, and writing the program in such a way to allow easy
expansion and the addition of extra information to constrain the fit. The main
component of the program was completed in the Summer of 2008, and passed to Dr.
Holtzman for further developement and work.
Active Protostars
In 2005 I conducted an extensive program of optical imaging of a faint
protostar (a thirteenth magnitude EXor object, similar to EX Lup) in an
outburst phase, in collaboration with Dr. Marc Audard of the University of
Geneva. Our joint observations in the x-ray, optical, infrared, and radio
regimes led to an ApJL article on the interaction between magnetic loops in the
stellar corona and the accretion disk. We suggest that enhanced mass accretion
rate during the outburst phase affected the x-ray emission from this source.
Cataclysmic Variables & Dwarf Novae
I continue to work with Dr. Edward Sion of Villanova University on various
questions concerning cataclysmic variable (CV) systems both active and
quiescent. My initial work focused on analysis of archival International
Ultraviolet Explorer (IUE) spectra for dwarf novae, constructing synthetic
accretion disk models to match the continuum levels and thus determining white
dwarf masses, system inclination angles, and accretion rates. An analysis of
all dwarf novae with good quality IUE spectra was completed in 2007. Recent
work has led to questions about the nature of nova-like CVs, specifically the
temperature of the underlying white dwarf. I also maintain and develop a suite
of analysis programs and scripts to support this research.
Solar Twins & Analogs
With Dr. Edward Guinan and Dr. Laurence DeWarf of Villanova University, I
developed the Sun in Time project, following the evolution of stars like
our Sun at x-ray and optical wavelengths by studying solar proxies which
currently exist across a range of ages. We confirmed the qualities of the
Solar Twin, 18 Sco, and showed how data obtained in different wavelength
regimes can highlight various physical processes in stars like the Sun.
Publications
ADS Query
Spectral Analysis of the Nova-Like Variable VY Scl from the High State to the Low State
Hamilton, R.T. & Sion, E.M.
2008, PASP, 120, 165
An International Ultraviolet Explorer Archival Study of Dwarf Novae in Outburst
Hamilton, R.T., Urban, J.A., Sion, E.M., Riedel A.R., Voyer, E.N., Marcy J.T., Lakatos, S.L.
2007, ApJ, 667, 1139
X-Ray Spectral Variability During an Outburst in V1118 Ori
Audard, M., Guedel M., Skinner, S.L., Briggs, K.R., Walter, F.M.,
Stringfellow, G., Hamilton, R.T., Guinan, E.F.
2005, ApJL, 635, 81
Dwarf Novae with Newly Determined Parallaxes: Model Analyses of VY Aquari, RU Pegasi, and T Leonis
Hamilton, R.T and Sion, E.M.
2004, PASP, 116, 926
Meetings
American Astronomical Society Meetings:
January 2006: American Astronomical Society meeting, The 2005 Accretion Outburst in V1118 Ori: Evidence for A Spectral Change in X-rays
Audard, M., Güdel, M., Skinner, S.L., Briggs K.R., Walter, F.M., Stringfellow, G., Hamilton, R.T., Guinan, E.F.
January 2005: American Astronomical Society meeting, Spectroscopy on a Shoestring: Worthwhile Science for Undergraduates
Hamilton, R.T., Engle, S.G., Guinan, E.F., McCook, G.P., Wasatonic, R.P.
June 2004: American Astronomical Society meeting, Dwarf Novae in Outburst with Newly Determined Parallaxes: Analyses of VY Aquari and RU Peg
Hamilton, R.T., Sion, E.M.
January 2003: American Astronomical Society meeting, Rotation-Activity-Age Relations of Sun-like Stars: In Search of the Much Coveted Solar Twin
Hamilton, R.T., Guinan, E.F., DeWarf, L.E.
May 2003: American Astronomical Society meeting, Determination of Age, Rotation, and Magnetic Activity Relations for dG, dK, and dM Stars: A Search for Candidates that may be Suitable for Life
Drescher J.W., Guinan, E.F., DeWarf, L.E., McCook, G.P., Hamilton, R.T., Ribas, I.
