Principal Investigator: Dr. Steven Raymond Majewski
Proposal Title: The Grid Giant Star Survey for the SIM Astrometric Grid:
Northern Hemisphere Extension
Proposal Summary/Abstract
We propose to continue our Grid Giant Star Survey for the SIM Astrometric Grid with an extension to the Northern Hemisphere. The Northern Grid Giant Survey (NGGSS) will be similar to work already underway in the Southern Hemisphere (the SGGSS) to locate bright, intermediate to metal-poor giant stars suitable for the SIM Astrometric Grid. Metal-poor giant stars, by virtue of their luminosity, can probe the Galaxy to greater distances than almost any other stellar type at the same apparent magnitude. Moreover, there is no evidence that K giants are worse in terms of photocenter wander from variability, binaries or planetary systems, and K giants may conceivably be better (in any case, there are several other proposals to this NRA aimed at testing these general claims as well as our GGSS stars directly). Thus, distant (>5kpc) giants with V<12 may have the smallest astrometric jitter of any potential Astrometric Grid star candidate.
With the completion of the NGSS, our Grid Giant Star Survey (GGSS),
a patchwork all-sky survey, will fill, at the 50-100% level, the need of
the SIM for a gird of astrometrically stable reference stars. The GGSS
may also be used to address a host of problems relating to Galactic structure
and kinematics. The GGSS surveys, North and South, are yielding the deepest
(V<17) large database of stars with identified luminosity classes (dwarfs
versus giants); thus, the GGSS is a valuable resource for culling targets
useful for SIM Galactic structure studies to a distance >50 kpc. We are
also generating a sizable list of stars blueward of the field star main
sequence turn off, which includes field blue horizontal branch stars, blue
stragglers, high latitude A stars, and blue metal-poor stars (BMPs). Our
systematic survey of all of these stellar species will aid in the understanding
of Galactic stellar populations as well as the nature of structural and
kinematical substructure in the halo.
Principal Investigator: Dr. Andreas Quirrenbach
Proposal Title: A Radial Velocity Survey of Candidate SIM Grid
Stars
Proposal Summary/Abstract
We will use the Hamilton Spectrograph at Lick Observatory for radial velocity survey of candidate grid stars for SIM. The 0.6m CAT telescope will be used to assess the statistical properties of bright nearby K giants, which can serve as proxies for the more distant K giants suited as SIM grid stars. We will use the 3m Shane telescope to begin an extensive survey of actual grid candidates drawnfrom the Hipparcos and Tyco catalogs. We will perform Monte Carlo simulations to determine the probabilities that stellar and substellar companions may go unnoticed by the radial-velocity observations. We will study the feasibility of an exhaustive high-precision radial-velocity survey of all stars in the SIM grid.
Principal Investigator: Dr. I. Neill Reid
Proposal Title: Meeting the Neighbors: A 2MASS-based survey of
stars and brown dwarfs within 20 parsecs of the Sun
Proposal Summary/Abstract
The deep near-infrared photometry provided by the 2MASS survey has proven a highly-effective means of identifying very low-mass stars and brown dwarfs in the immediate Solar Neighbourhood. Building on this success, we propose to identify dwarfs of spectral type M or later within 20 parsecs of the Sun. We will achieve this goal by combining the 2MASS database with optical data from the POSS I/II and southern UK Schmidt/ESO Schmidt surveys. Based on our experience in analysing those data, we have devised techniques which will reduce the several hundred million point sources detected by 2MASS to a few thousand candidate nearby stars and brown dwarfs. We expect to identify ~900 late-type M dwarfs, L dwarfs, and T-type 'methane' brown dwarfs. Besides expanding the local census, our program will aim at deriving Basic observational properties (magnitudes, spectral types) for these sources. These results will be made available to the general community through an on-line database.
Principal Investigator: Dr. Richard Gray
Proposal Title: Spectral Classification and Determination
of the Basic Parameters of Dwarf and Giant Stars earlier than M0 within
40 parsecs
Proposal Summary/Abstract
We propose to observe spectroscopically, over the course of three years,
all of the approximately 3600 main-sequence and giant stars with spectral
types earlier than M0 within a radius of 40pc. These spectra, obtained
at 1.5 - 4.5 Angstrom resolution will be used to obtain homogeneous, precision,
MK spectral Types of these stars, and, in conjunction with existing Stroemgren
photometry and synthetic spectra based
on Kurucz models, to derive the basic astrophysical parameters of most
of these stars, i.e., effective temperature, log(g), microturbulent velocity,
and [M/H]. This information will enable the derivation of the luminosity,
masses and radii for these stars. During the course of this analysis, the
spectra will be closely examined for evidence of chromospheric activity
and spectroscopic evidence of a companion, as well as chemical peculiarities
and unusually high rotational velocities. These stars, especially the G
and K dwarfs, are of fundamental importance in the discovery of extra-solar
planetary systems. Between the three of us, we have more than adequate
access to telescopes and classification spectrographs in both the hemispheres
to carry out this work. These telescopes include the 0.8m at the Dark Sky
Observatory (North Carolina), the Vatican Advanced Technology Telescope,
the 1.88m at the David Dunlap Observatory and 25% of the time on the 0.6
meter telescope at the El Leoncito Astronomical Complex in Argentina. The
PI and one of the Co I's have compiled over a number of years extensive
photographic and digital databases of spectra of bright and nearby stars;
we estimate that we have spectra for many of the stars earlier than M0
within 20pc, and substantial numbers out to a radius of 40pc. A technique
(using a multidimensional downhill simplex algorithm to determine the best
fit of the observed with model spectra and fluxes) to determine the basic
parameters of the stars has already been formulated and extensively tested.
With observations, data reduction and digitization of the photographic
database required, the completion of the project to 40pc will require a
research assistant, and will take 3 years.
Principal Investigator: Dr. Douglas Geisler (administrative PI is Dr. Nicholas Suntzeff)
Proposal Title: Photometric and Spectroscopic Followup of Grid Giant
Star Candidates: Monitoring Photometric
and Radial Velocity Stability, Improving Stellar Parameters, Checking
for Stellar and Planetary Companions and Studying Galactic Nucleosynthesis
Proposal Summary/Abstract
We propose to obtain followup photometry and spectroscopy of the grid
giant star candidates that we are establishing as part of our current SIM
Preparatory Science program (Majewski PI). This program will establish
several thousand metal-poor southern hemisphere G-K giants as grid star
candidates, based on single-epoch photometry and low resolution spectroscopy.
We anticipate a similar grid giant candidate database for the northern
hemisphere, as requested in a separate proposal (Majewski PI). Our privileged
access to this database and to telescopes in both hemispheres allows us
to obtain rapid and timely multi-epoch photometric and high resolution
spectroscopic followup observations of these candidates. Such data are
essential for verifying their photometric and radial velocity stability
and thus guaranteeing their utility as grid stars. In addition, our observations
will allow us to greatly improve our knowledge of the basic atmospheric
parameters of these stars (surface temperature, gravity and metallicity).
We will carry out a sensitive search for stellar and planetary companions
and establish the binary frequency of these interesting stars for the first
time. Finally, we will study their detailed chemical composition. Such
a large-scale study of abundances in metal-poor giants should yield fascinating
details of Galactic nucleosynthesis.