The ASTRA spectrophotometer: A July 2004 progress report

Abstract

Abstract.A cross-dispersed spectrophotometer with a back-illuminated uv-coated CCD detector and its automated 0.5-m telescope at the Fairborn Observatory, Washington Camp, AZ now under construction, should begin scientific observations in the Spring of 2005 . The Citadel ASTRA (Automated Spectrophotometric Telescope Research Associates) Telescope will be able to observe Vega the primary standard, make rapid measurements of the naked-eye stars, use 10 minutes per hour to obtain photometric measurements of the nightly extinction, and obtain high quality observations of V = 10.5 mag. stars in an hour. The approximate wavelength range is λ 3300-9000 with a resolution of 14Å in first and 7Å in second order. Filter photometric magnitudes and indices will be calibrated in part for use as quality checks.First a grid of secondary standards will be calibrated differentially with respect to Vega. They will also be used to find the nightly extinction. The candidates were selected from the most stable bright secondary stars of the grating scanner era, the least variable main sequence B0-F0 band stars in Hipparcos photometry, and metal-poor stars. Continued measurements of secondary stars will be used to improve the quality of the secondary standard fluxes. Science observations for major projects such as comparisons with model atmospheres codes and for exploratory investigations should also begin in the first year of scientific observations. The ASTRA team realizes to deal with this potential data flood that they will need help to make the best scientific uses of the data. Thus they are interested in discussing possible collaborations. In less than a year of normal observing, all isolated stars in the Bright Star Catalog that can be observed can have their fluxes well measured. Some A star related applications are discussed.

Observations of convection in A-type stars

“…This situation will be rectified, once the ASTRA Spectrophotometer (Adelman et al 2003(Adelman et al , 2005 begins operation. This will allow spectrophotometry to be added to our observational diagnostic toolkit.…”

Stellar fluxes as probes of convection in stellar atmospheres

“…They are being integrated at the Fairborn Observatory near Nogales, Arizona. Scientific observations are expected to begin in 2007 (Adelman et al 2007.…”

Observational challenges of A-type stars

“…For better than Hipparcos parallaxes, we will have to wait for the Gaia mission (see, e.g., http://astro.estec.esa.nl/GAIA). There is still the need to better know the actual spectral energy distribution of Ap stars, something that may be achieved with the ASTRA spectrophotometer (Adelman et al 2005) which uses a 0.5-m telescope.…”