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LAMOST observations in the Kepler field. Analysis of the stellar parameters measured with the LASP based on the low-resolution spectra
Anbing Ren (Beijing Normal University), Jianning Fu (Department of Astronomy, Beijing Normal University, No. 19 Xinjiekouwai Street, Haid- ian District, Beijing 100875, China), Peter De Cat (Royal observatory of Belgium, Ringlaan 3, B-1180 Brussel, Belgium), Ruyuan Zhang (Department of Astronomy, Beijing Normal University, No. 19 Xinjiekouwai Street, Haid- ian District, Beijing 100875, China), et al.
All of the 14 subfields of the Kepler field have been observed at least once with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST, Xinglong Observatory, China) during the 2012-2014 observation seasons. The raw spectral data were reduced by the LAMOST 2D pipeline to obtain the flux- and wavelength-calibrated, sky-subtracted spectra. There are 88,628 reduced spectra with SNRg (signal-to-noise ratio in g band) ≥ 6 after the first round (2012-2014) of observations for the LAMOST-Kepler project (LK-project). They will be released publicly in the third data release of LAMOST (DR3). By adopting the upgraded version of the LAMOST Stellar Parameter pipeline (lasp), we have determined the atmospheric parameters (Teff, log g, and [Fe/H]) and radial velocity (Vrad) for 51,406 stars with 61,226 spectra. Compared with atmospheric parameters derived from both high-resolution spectroscopy and asteroseismology method for common stars in Huber et al. (2014), an external calibration of lasp atmospheric parameters was made, leading to the determination of external errors for the giants and dwarfs, respectively. Multiple spectroscopic observations for the same objects of the LK-project were used to estimate the internal uncertainties of the atmospheric parameters as a function of SNRg with the unbiased estimation method. The lasp atmospheric parameters were calibrated based on both the external and internal uncertainties for the giants and dwarfs, respectively. Fitting formulae are obtained segmentally for both the calibrated atmospheric parameters of the LK-project and the KIC parameters with the common stars. We obtained more than 97,600 and 99,700 reduced spectra for the LK-project and K2-project during the 2015.09-2016.02 observations seasons, respectively. The Teff, log g, [Fe/H] and Vrad and their errors are determined for more than 79,300 and 66,300 reduced low-resolution spectra in the LK-project and K2-project, respectively. These parameters will be calibrated by using both the linear relationships derived from the external comparisons and their internal uncertainties. Combing with the high-precision time-series photometric data provided by the Kepler mission, the calibrated atmospheric parameters and radial velocities of the two projects will be very useful for studying stars in the Kepler field and K2 fields.