LAMOST Time-Domain Survey: First Results of four $K$2 plates

Abstract

From Oct. 2019 to Apr. 2020, LAMOST performs a time-domain spectroscopic survey of four K2 plates with both low-and med-resolution observations. The low-resolution spectroscopic survey gains 282 exposures (≈46.6 hours) over 25 nights, yielding a total of about 767,000 spectra, and the medresolution survey takes 177 exposures (≈49.1 hours) over 27 nights, collecting about 478,000 spectra. More than 70%/50% of low-resolution/med-resolution spectra have signal-to-noise ratio higher than 10. We determine stellar parameters (e.g., T eff , logg, [Fe/H]) and radial velocity (RV) with different methods, including LASP, DD-Payne, and SLAM. In general, these parameter estimations from different methods show good agreement, and the stellar parameter values are consistent with those of APOGEE. We use the Gaia DR2 RV data to calculate a median RV zero point (RVZP) for each spectrograph exposure by exposure, and the RVZP-corrected RVs agree well with the APOGEE data. The stellar evolutionary and spectroscopic masses are estimated based on the stellar parameters, multi-band magnitudes, distances and extinction values. Finally, we construct a binary catalog including about 2700 candidates by analyzing their light curves, fitting the RV data, calculating the binarity parameters from med-resolution spectra, and crossmatching the spatially resolved binary catalog from Gaia EDR3. The LAMOST TD survey is expected to get breakthrough in various scientific topics, such as binary system, stellar activity, and stellar pulsation, etc.

The Spectroscopic Binaries from LAMOST Medium-Resolution Survey (MRS). I. Searching for Double-lined Spectroscopic Binaries (SB2s) with Convolutional Neural Network

“…Therefore, it balances the tradeoff between TPR and FPR and relies on specific science goals. For example, our low Λ model has been used in the LAMOST-TD survey (Wang et al 2021c) to prompt possible SB2 candidates. It serves as an aid parallel to manual inspection and works well.…”

“…Combined with high-precision photometry from Kepler/K2 and TESS, it forms a valuable and sizable dataset for timedomain research on this scientific goal (e.g., Pan et al 2020Pan et al , 2021Wang et al 2021a,b). A subproject towards 4 K2 plates, namely the LAMOST-TD survey (Wang et al 2021c), has led to the discovery of a subgiant with an undetected 1-3 M companion (Yang et al 2021a). Minute-cadence photometry is obtained for LAMOST MRS fields as well to study short period variables (Lin et al 2021).…”

Detecting and Monitoring Tidal Dissipation of Hot Jupiters in the Era of SiTian

“…SiTian is an integrated network of 1 m telescopes, aiming at time-domain astronomy (Liu et al 2021). It shall produce a huge amount of light curves, that would contribute to time-domain researches of targets with physical size ranging from galaxy clusters to planets (Liu et al 2019Yang et al 2020aYang et al , 2020bYang et al , 2022Lennon et al 2021;Ngeow et al 2021;Wang et al 2021;Yang et al 2021c). Monitoring the same area of the sky simultaneously in three bands (u, g, i), SiTian will deliver high precision timing measurements, enabling detections of TTVs.…”

TYC~2990-127-1: an Algol-type SB2 binary system of subgiant and red giant with a probable ongoing mass-transfer

“…Kounkel et al (2021) reports RV scd = −102.33 ± 1.28 km s −1 , RV prm = −31.88 ± 1.72 km s −1 , which is very close to our orbital solution RV scd = −111.46 km s −1 , RV prm = −28.00 km s −1 . The discrepancy is probably due to the different RV zero points of the spectrographs used in LAMOST and APOGEE (Wang et al 2021). We convert the observed spectrum's wavelength scale from vacuum to air and apply a heliocentric correction using PyAstronomy (Czesla et al 2019).…”