From Oct.2019 to Apr.2020,LAMOST performed a time-domain(TD)spectroscopic survey of four K2 plates with both low-and medium-resolution observations.The low-resolution spectroscopic survey acquired 282 exposures(≈46.6...From Oct.2019 to Apr.2020,LAMOST performed a time-domain(TD)spectroscopic survey of four K2 plates with both low-and medium-resolution observations.The low-resolution spectroscopic survey acquired 282 exposures(≈46.6 h)over 25 nights,yielding a total of about 767000 spectra,and the medium-resolution survey took 177 exposures(≈49.1 h)over 27 nights,collecting about 478000 spectra.More than 70%/50%of low-resolution/medium-resolution spectra have signal-to-noise ratio higher than 10.We determine stellar parameters(e.g.,Teff,log g,[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 values 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 medium-resolution spectra and cross-matching the spatially resolved binary catalog from Gaia EDR3.The LAMOST TD survey is expected to represent a breakthrough in various scientific topics,such as binary systems,stellar activity,stellar pulsation,etc.展开更多
Stellar activity cycles have been found on many stars through different methods.Although in debate,an empirical relation has been found where a period of stellar activity cycle Pcyc is positively correlated with rotat...Stellar activity cycles have been found on many stars through different methods.Although in debate,an empirical relation has been found where a period of stellar activity cycle Pcyc is positively correlated with rotation period Prot along some segregated branches.In this work,we built a systematic process to search for the Kepler objects that are analogous to the long-term solar brightness variations and investigate their possible origins.After a rigorous selection,we obtained 43 objects that all exhibit clear long-term beat-like patterns and their variability(amplitude of rotational modulation)periods and rotation periods were derived.Due to the 4-year duration of the Kepler mission,our targets are located in the region where the cycle periods are longer than~1 yr and shorter than~2.5 yr.However,all of our targets exhibit clear and notable quasi-periodic variations in variability,yet we cannot confirm any linear trends that were predicted by previous research independently.This may suggest that in the Kepler realm of the Pcyc-Prot diagram,these relations would mix with each other or the beat-like patterns may not be related to the stellar cycle unless other evidence is provided.展开更多
基金the National Natural Science Foundation of China(Grant Nos.11988101,11933004 and 12003050)supported by the National Key Research and Development Program of China(Grant Nos.2019YFA0405000,2019YFA0405504 and 2016YFA0400804)+2 种基金the B-type Strategic Priority Program of the Chinese Academy of Sciences(CAS)under grant number XDB41000000the Youth Innovation Promotion Association of CAS(id.2019057 and 2020060,respectively)the European Research Council(ERC)under the European Union Horizon 2020 research and innovation programme(Cartograph Y GA.804752)。
文摘From Oct.2019 to Apr.2020,LAMOST performed a time-domain(TD)spectroscopic survey of four K2 plates with both low-and medium-resolution observations.The low-resolution spectroscopic survey acquired 282 exposures(≈46.6 h)over 25 nights,yielding a total of about 767000 spectra,and the medium-resolution survey took 177 exposures(≈49.1 h)over 27 nights,collecting about 478000 spectra.More than 70%/50%of low-resolution/medium-resolution spectra have signal-to-noise ratio higher than 10.We determine stellar parameters(e.g.,Teff,log g,[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 values 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 medium-resolution spectra and cross-matching the spatially resolved binary catalog from Gaia EDR3.The LAMOST TD survey is expected to represent a breakthrough in various scientific topics,such as binary systems,stellar activity,stellar pulsation,etc.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB 41000000)support from the National Natural Science Foundation of China(NSFC,Grant Nos.11988101 and 113300034)the National Key Research and Development Program of China(NKRDPC,Grant Nos.2016YFA0400804,2019YFA0405000 and 2019YFA0405504)。
文摘Stellar activity cycles have been found on many stars through different methods.Although in debate,an empirical relation has been found where a period of stellar activity cycle Pcyc is positively correlated with rotation period Prot along some segregated branches.In this work,we built a systematic process to search for the Kepler objects that are analogous to the long-term solar brightness variations and investigate their possible origins.After a rigorous selection,we obtained 43 objects that all exhibit clear long-term beat-like patterns and their variability(amplitude of rotational modulation)periods and rotation periods were derived.Due to the 4-year duration of the Kepler mission,our targets are located in the region where the cycle periods are longer than~1 yr and shorter than~2.5 yr.However,all of our targets exhibit clear and notable quasi-periodic variations in variability,yet we cannot confirm any linear trends that were predicted by previous research independently.This may suggest that in the Kepler realm of the Pcyc-Prot diagram,these relations would mix with each other or the beat-like patterns may not be related to the stellar cycle unless other evidence is provided.