Richard O. Gray
Professor of Physics and Astronomy
BA-Mathematics Washington State University
MSc-Astronomy University of Toronto
PhD-Astronomy University of Toronto
Office: CAP 311
I am a Professor in the department of Physics and Astronomy
at Appalachian State University. I currently teach the following
courses: AST 1001/1002 (Introductory Astronomy), AST 2002 (Observational
AST 3100 (Astrophysics), PHY 3538 (Environmental Physics) and PHY 4620
(Optics). I also normally have one graduate student, and regularly
involve undergraduates in my research. In addition, I have developed
a number of teaching resources, including some computerized introductory
astronomy labs, as well as a Digital
Spectral Classification Atlas which is useful both for advanced
classes on stellar spectroscopy and for research.
Recently, I was a member of the faculty of the Vatican Observatory Summer
School during the summer of 1999 ( VOSS
99). This is an international astronomy summer school, open to
beginning graduate students in astronomy of all faiths and no faith.
I taught 24 exceptionally bright students from 20 countries about the astrophysics
of single stars.
My research is in the field of stellar spectroscopy. My interests
include the discovery and classification of chemically pecular stars, in
particular the Lambda
Bootis stars, a group of Population I A-type stars which show
marked underabundances in most elements with the exception of C,N,O and
S, which can be of nearly solar abundance. These stars are astrophysically
important because these underabundances are most likely due to accretion
of metal-depleted gas from the interstellar medium or from a protoplanetary
disk. Thus these stars may have something to tell us about protoplanetary
disks and planet formation, as well as being intrinsically interesting
in themselves. In collaboration with my colleague, Dr. Chris Corbally,
S.J. of the Vatican Observatory, we are trying to determine the evolutionary
state of these objects. So far we have discovered lambda Bootis stars
in the Orion OB1 association, but have not been successful in finding any
of these stars in intermediate-age clusters, even though many of the Lambda
Bootis stars in the field must be of that age range. This may be
telling us something important about the formation and survival of protoplanetary
disks in star clusters. See below for some recent papers we have
published on this subject. Recently, another colleague of mine and
I have discovered that HR 8799, a lambda Bootis star, is also a Gamma Doradus
pulsator. This has led to some insight into the nature of the pulsation
mechanism in these newly discovered variables (see papers below).
In addition to the Lambda Bootis stars, I have become interested in
pre-main-sequence A-type stars, stars which are very young and are still
contracting to the main sequence. Many of these stars show emission
lines in their spectra, and are known as the "Ae stars" The two groups
turn out to be connected, as Chris Corbally and I recently discovered (see
papers below) one Ae star which is also a Lambda Bootis star. Chris
and I have also extended the MK spectral classification system to these
Ae stars (see below).
In addition to these observational topics, I have been involved in the
modeling of stellar spectra through spectral synthesis. I have written
a spectral synthesis program SPECTRUM
, which computes the emergent spectrum given a stellar atmosphere model.
I have been using these synthetic spectra to determine the basic parameters
of stars (effective temperature, gravity, [M/H] and microturbulent velocity)
using the spectra I have obtained with the Gray/Miller spectrograph
which I designed and built (with the expert help of Robert Miller, instrument
maker) for the Dark
Sky Observatory 32" telescope. This research is currently being
written up, and should soon be submitted for publication.
During my time at ASU, I have designed and constructed two astronomical
spectrographs. The first was the Gray/Miller
cassegrain classification spectrograph which I have used for
most of my research on the Dark Sky Observatory 32" telescope. More
recently, in collaboration with my graduate student, Pam Graham, I designed
and constructed a Faint Object Spectrograph for the Dark Sky Observatory.
This spectrograph is capable of obtaining very low resolution spectra of
objects down to mv = 18.5.
Here are some recent papers I have authored/co-authored on the topics
Kaye , A.B. et al. 1999 AJ 118, 2997 "HD 62454 and HD 68192: Two New
Gamma Doradus Variables"
Gray, R.O. & Kaye, A.B. 1999 AJ 118, 2993 "HR 8799: A Link between
Gamma Doradus Variables and Lambda Bootis Stars" pdf
Gray, R.O. & Corbally, C.J. 1999 BAAS 194, 47.02 "A Spectroscopic
Search for Peculiar A-type Stars in Open Clusters"
Miroshnichenko, A.S. et al. 1999 A&A 347, 137 "Observations of Recently
Recognized candidate Herbig Ae/Be stars" pdf
Wilhelm, R., Beers, T.C. & Gray, R.O. 1999 AJ 117, 2308 "Spectroscopy
of Hot Stars in the Galactic Halo II. The Identification and Classification
of Horizontal-Branch and Other A-type Stars"
Zwintz, K. et al. 1999 A&A 343, 899 "Hubble Deep Field Guide Star
Gray, R.O. & Corbally, C.J. 1998 AJ 116, 2530 "The Incidence of
Lambda Bootis Stars via an Extension of the MK Spectral Classification
System to Very Young A-type Stars" pdf
Gray, R.O. 1998 AJ 116, 482 "The Absolute Flux Calibration of Stromgren
uvby Photometry" pdf
Paunzen, E. & Gray, R.O. 1997 A&AS 126, 407 "A Spectroscopic
Survey for Lambda Bootis Stars I. Strategy, Techniques and First Results