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Spectroscopy with VATT

Published onJun 01, 2020
Spectroscopy with VATT

Stellar spectroscopy is an ongoing endeavor at the VATT telescope, both from the low-resolution end and, more recently, also high-resolution end. Using the 1.8-m f/1.0 VATT optical telescope on Mt. Graham (MGIO), near Tucson, AZ, we test a method for estimating the stellar parameters of stars from medium- to low-resolution spectra, something ordinary done using high signal-to-noise ratio (S/N), high-resolution (R>20,000) spectroscopy for the most accurate determinations. Here we present some preliminary results using the methodologies of Kirby et al. (2008), Steinmetz et al. (2006), and Lee, Beers, et al. (2010), who give a general method capable of recovering estimates of abundances for α-elements using lower resolution spectroscopy, based on spectral matching against a grid of synthetic spectra, employing a star-by-star comparison with such spectra. This method is capable of estimating [α/Fe] with a precision of < 0.07 dex for spectra with S/N > 50/1 over the parameter space Teff = [4500, 7000] K, log10g = [1.5, 5.0], [Fe/H] = [–3.0, +0.3], and [α/Fe] = [–0.1, +0.6]. This technique is ideal for VATT and its medium-resolution spectrometer because it applies spectral synthesis to medium-resolution spectroscopy (MRS; R ~ 6000) in the red (6300 Å < λ < 9100 Å) to measure [Fe/H] and [α/Fe] of individual FGK stars over a wide metallicity range, comparable to what VATT can observe. From the high-resolution end, VATT is also part of the VATT-PEPSI-TESS survey/collaboration whereby the PEPSI high-resolution spectrograph (R=200,000) from the LBT telescope is being used in conjunction with the VATT optical telescope to obtain high-resolution spectra (480-544 nm, 628-741 nm, 741- 912 nm) from TESS survey stars in the hope of providing precise spectroscopic parameters. Some initial results are given.

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