Want a PEPSI? Performance status of the recently commissioned high-resolution spectrograph
and polarimeter for the 2x8.4m Large Binocular Telescope
Strassmeier, Klaus G.; Ilyin, I.; Weber, M.; Jaervinen, A.; Woche, M.; Jaervinen, S.; Sablowski, D.; Mallonn, M.; Keles, E.; Carroll, T.; Johnson, M. C.; Bender, C.; Wagner, R. M.; Veillet, C.
Angol nyelvű Konferenciaközlemény (Könyvrészlet) Tudományos
PEPSI is the new fiber-fed and stabilized "Potsdam Echelle Polarimetric and Spectroscopic
Instrument" for the Large Binocular Telescope (LBT). It covers the entire optical
wavelength range from 384 to 913 nm in three exposures at resolutions of either R=lambda/Delta
lambda=50,000, 130,000 or 250,000. The R=130,000 mode can also be used with two dual-beam
Stokes IQUV polarimeters. The 50,000-mode with its 12-pix sampling per resolution
element is our "bad seeing" or "faint-object" mode. A robotic solar-disk-integration
(SDI) telescope feeds solar light to PEPSI during day time and a 450-m fiber feed
from the 1.8m VATT can be used when the LBT is busy otherwise. CCD characterization
and a removal procedure for the spatial fixed-pattern noise were the main tasks left
from the commissioning phase. Several SDI spectral time series with up to 300 individual
spectra per day recovered the well-known solar 5-minute oscillation at a peak of 3
mHz (5.5min) with a disk-integrated radial-velocity amplitude of only 47 cm/s. Spectral
atlases for 50 bright benchmark stars including the Sun were recently released to
the scientific community, among them the ancient planet-system host Kepler-444. These
data combine PEPSI's high spectral resolution of R= 250,000 with signal-to-noise ratio
(S/N) of many hundreds to even thousands covering the entire optical to near-infrared
wavelength range from 384 to 913 nm. Other early science cases were exoplanet transits
including TRAPPIST-1, a spectrum of Boyajian's star that revealed strong and structured
but stable ISM Na D lines, a spectrum of zeta Oph allowing a redetermination of the
ISM Li line doublet, and a first Doppler image of the young solar analog EK Dra that
revealed starspots with solar-like penumbrae.