Saul J. Adelman, Department of Physics, The Citadel, United States of America - Principal InvestigatorAustin F. Gulliver, Department of Physics, Brandon University, Canada - Co-investigatorBarry Smalley, Department of Physics, Keele University, England - Co-investigatorJohn S. Pazder, Dominion Astrophysical Observatory, Herzberg Institute for Astrophysics, Canada - Optical DesignerP. Frank Younger, Aurora Astronomical Services, Canada - Mechanical Designer and Supervisor of Instrument ConstructionLouis Boyd, Fairborn Observatory, United States of America - Designer and Builder of The Citadel ASTRA TelescopeDonald Epand, Fairborn Observatory, United States of America - ATIS Expert
A CCD-based spectrophotometer for a new automated 0.5-m telescope at the Fairborn Observatory, Washington Camp, AZ, USA, altitude 1800 m should see first light in Spring 2004. The Citadel ASTRA (Automated Spectrophotometric Telescope Research Associates) Telescope will permit observations of Vega the primary spectrophotometric standard, rapid measurements of the naked-eye stars, sufficient observing time to obtain photometric measurements of the nightly extinction, and still obtain high quality observations of stars of about 10.5 magnitude in an hour. This multiplexed cross-dispersed instrument should produce high-quality fluxes at least of 3300-9000 Angstroms with a resolution of 14 Angstroms in first and 7 Angstroms in second order and full wavelength coverage except for regions badly affected by telluric lines.
Summary of Project
The ASTRA telescope and spectrophotometer are optimally designed for efficient operations using input from astronomers and the experience of the design team. The CCD frames will be reduced to one-dimensional spectra using program CCDSPEC of Austin F. Gulliver & Graham Hill and photometrically calibrated using program SPECPHOTOCAL by Barry Smalley which should correct for the effects of most telluric lines at airmasses < 4.
Model atmospheres are the analytical link between the physical properties of stars (M, R, L, and composition) and the observed flux distribution and spectral line profiles. By comparing predictions of model atmospheres with spectrophotometric fluxes (and Balmer line profiles) effective temperatures, surface gravities, and metallicities can be found for a wide variety of stars. Comparisons for the same star between the best-fitting model atmospheres calculated from different codes will provide insight into how well each code reproduces these observations. High-quality elemental abundance studies will permit consistency checks. As the efficiency of convection can produce observable results in the energy distributions, it should be possible to check the results of different convection theories. Investigators will be able to synthesize a variety of indices which could be obtained by filter photometry.
The first major observing project will be the revision and extension of the bright secondary standards. The existing grid of good secondary standards will be increased several-fold and include those selected to be near variables of particular interest. Over the lifetime of the instrument, measurements of secondary stars for calibration and extinction will be used to improve the quality of the secondary standard fluxes. In less than a year of normal observing, all isolated stars with V < 7.5 mag. and declinations between +76 degrees and -14 degrees can have their fluxes well measured by the ASTRA instrument.
Adelman, Gulliver, and Smalley in planning to deal with this potential flood of data, realize that they will need help to make the best scientific uses of the ASTRA data. Thus they are interested in discussing possible collaborations. As many studies of variable stars will utilize local spectrophotometric standards, they plan to calibrate such stars as part of the initial effort.
This work is supported by NSF grant AST-0115612 to The Citadel.
We thank Dr. Allie Ford for the preliminary rendition of the ASTRA logo.
Last Modified On: Wednesday, July 10, 2002
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