Monitoring chromospheric and photospheric indexes of magnetic activity can provide valuable information, especially the interaction between different parts of the atmosphere and their response to magnetic fields. We extract chromospheric indexes, S and Rhk+, for 59,816 stars from LAMOST spectra in the LAMOST-Kepler program, and photospheric index, Reff, for 5575 stars from Kepler light curves. The log Reff shows positive correlation with log Rhk+. We estimate the power-law indexes between Reff and Rhk+ for F-, G-, and K-type stars, respectively. We also confirm the dependence of both chromospheric and photospheric activity on stellar rotation. Ca II H and K emissions and photospheric variations generally decrease with increasing rotation periods for stars with rotation periods exceeding a few days. The power-law indexes in exponential decay regimes show different characteristics in the two activity-rotation relations. The updated largest sample including the activity proxies and reported rotation periods provides more information to understand the magnetic activity for cool stars.
The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) at the Xinglong observatory in China is a new 4-m telescope equipped with 4,000 optical fibers. In 2010, we initiated the LAMOST-Kepler project. We requested to observe the full field-of-view of the nominal Kepler mission with the LAMOST to collect low-resolution spectra for as many objects from the KIC10 catalogue as possible. So far, 12 of the 14 requested LAMOST fields have been observed resulting in more than 68,000 low-resolution spectra. Our preliminary results show that the stellar parameters derived from the LAMOST …
A sample of the LAMOST spectra of the early type M0-M3 dwarfs is compared with the Kepler observations. It is found that M dwarfs with strong chromospheric emission in $H_α$ have large flare activity in general. The rotational periods derived from the Kepler measurements have close correlations with the sizes of the flares, the power-law distribution index and the equivalent widths of the $H_α$ emission. A clear trend exists for higher magnetic activities being detected in faster rotating M dwarfs (rotation periods $<$ 20 day).
The LAMOST-Kepler (LK-) project was initiated to use the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) to make spectroscopic follow-up observations for the targets in the field of the Kepler mission. The Kepler field is divided into 14 subfields that are adapted to the LAMOST circular field with a diameter of 5 degrees. During the regular survey phase of LAMOST, the LK-project took data from 2012 June to 2017 June and covered all the 14 subfields at least twice. In particular, we describe in this paper the second Data Release of the LK-project, including all spectra acquir…
Stellar fundamental parameters are important in the asteroseismic study of Kepler light curves. However, the most used estimates in the Kepler Input Catalog (KIC) are not accurate enough for hot stars. Using a sample of B stars from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) spectral survey, we confirmed the systematic underestimation in KIC effective temperature and overestimation in KIC surface gravity. The good agreement between LAMOST and other follow-up observations proved the accuracy of effective temperature and surface gravity of B stars derived from LAMOST …
In this letter, we report the discovery of 24 new super Li-rich (A(Li) $\ge$ 3.2) giants of He-core burning phase at red clump region. Results are based on systematic search of a large sample of about 12,500 giants common to the LAMOST spectroscopic and Kepler time resolved photometric surveys. The two key parameters derived from Kepler data; average period spacing ($Δp$) between $l=1$ mixed gravity dominated g-modes and average large frequency separation ($Δν$) $l=0$ acoustic p-modes, suggest all the Li-rich giants are in He-core burning phase. This is the first unbiased survey subjected to a…
Asteroseismology is a powerful tool to precisely determine the evolutionary status and fundamental properties of stars. With the unprecedented precision and nearly continuous photometric data acquired by the NASA Kepler mission, parameters of more than 10$^4$ stars have been determined nearly consistently. However, most studies still use photometric effective temperatures (Teff) and metallicities ([Fe/H]) as inputs, which are not sufficiently accurate as suggested by previous studies. We adopted the spectroscopic Teff and [Fe/H] values based on the LAMOST low-resolution spectra (R~1,800), and …
Radial velocity is one of key measurements in understanding the fundamental properties of stars, stellar clusters and the Galaxy. A plate of stars in the Kepler field were observed in May of 2018 with the medium-resolution spectrographs of LAMOST, aiming to test the performance of this new system which is the upgraded equipment of LAMOST after the first five-year regular survey.We present our analysis on the radial velocity measurements (RVs) derived from these data. The results show that slight and significant systematic errors exist among the RVs obtained from the spectra collected by differ…
Homogeneous metallicities and continuous high-precision light curves play key roles in studying the pulsation properties of RR Lyrae stars. By cross-matching with LAMOST DR6, we have determined 7 and 50 Non-Blazhko RRab stars in the Kepler and K2 fields, respectively, who have homogeneous metallicities determined from low-resolution spectra of the LAMOST-Kepler/K2 project. The Fourier Decomposition method is applied to the light curves of these stars provided by the Kepler space based telescope to determine the fundamental pulsation periods and the pulsation parameters. The calculated amplitud…
Asteroseismology allows for deriving precise values of surface gravity of stars. The accurate asteroseismic determinations now available for large number of stars in the Kepler fields can be used to check and calibrate surface gravities that are currently being obtained spectroscopically for a huge numbers of stars targeted by large-scale spectroscopic surveys, such as the on-going Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Galactic survey. The LAMOST spectral surveys have obtained a large number of stellar spectra in the Kepler fields. Stellar atmospheric parameters of…
Mapping lithium evolution for evolved stars will provide restrictions and constraints on the fundamental stellar interior physical processes, which further shed light on our understanding of the theory of stellar structure and evolution. Based on a sample of 1,848 giants with known evolutionary phases and lithium abundances from the LAMOST-\kepler{} and LAMOST-\emph{K}2 fields, we construct mass-radius diagrams to characterize the evolutionary features of lithium. The stars at red giant branch (RGB) phase show natural depletion along with their stellar evolution, particularly, there is no obvi…
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. There are 88,628 reduced spectra with SNR$_g$ (signal-to-noise ratio in g band) $\geq$ 6 after the first round (2012-2014) of observations for the LAMOST-Kepler project (LK-project). By adopting the upgraded version of the LAMOST Stellar Parameter pipeline (LASP), we have determined the atmospheric parameters ($T_{\rm eff}$ , $\log g$, and $\rm [Fe/H]$) and heliocentric rad…
The nearly continuous light curves with micromagnitude precision provided by the space mission Kepler are revolutionising our view of pulsating stars. They have revealed a vast sea of low-amplitude pulsation modes that were undetectable from Earth. The long time base of Kepler light curves allows an accurate determination of frequencies and amplitudes of pulsation modes needed for in-depth asteroseismic modeling. However, for an asteroseismic study to be successful, the first estimates of stellar parameters need to be known and they can not be derived from the Kepler photometry itself. The Kep…
The NASA $Kepler$ mission obtained long-term high-quality photometric observations for a large number of stars in its original field of view from 2009 to 2013. In order to provide reliable stellar parameters in a homogeneous way, the LAMOST telescope began to carry out low-resolution spectroscopic observations for as many stars as possible in the $Kepler$ field in 2012. By September 2018, 238,386 low-resolution spectra with SNR$_g \geq 6$ had been collected for 155,623 stars in the $Kepler$ field, enabling the determination of atmospheric parameters and radial velocities, as well as spectral c…
The LAMOST-Kepler survey, whose spectra are analyzed in the present paper, is the first large spectroscopic project aimed at characterizing these sources. Our work is focused at selecting emission-line objects and chromospherically active stars and on the evaluation of the atmospheric parameters. We have used a version of the code ROTFIT that exploits a wide and homogeneous collection of real star spectra, i.e. the Indo US library. We provide a catalog with the atmospheric parameters (Teff, logg, [Fe/H]), the radial velocity (RV) and an estimate of the projected rotation velocity (vsini). For …
The spotted detached eclipsing binary (DEB) offers insights into starspots on the binary. Three spotted DEBs, KIC 8097825, KIC 6859813, and KIC 5527172, which were observed by the Kepler photometry and LAMOST spectroscopy, are studied in this work. The physical parameters of binaries are determined by binary modeling. The sizes, lifetimes, and single/double-dip ratio (SDR) of starspots are derived by starspot analysis. KIC 8097825 has large starspots. KIC 6859813 has a spot rotation period shorter than its orbital period but the system should be synchronized inferred from timescale estimation.…
Obtaining measurements of chromospheric and photometric activity of stars with near-solar fundamental parameters and rotation periods is important for a better understanding of solar-stellar connection. We select a sample of 2603 stars with near-solar fundamental parameters from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST)-Kepler field and use LAMOST spectra to measure their chromospheric activity and Kepler light curves to measure their photospheric activity (i.e., the amplitude of the photometric variability). While the rotation periods of 1556 of these stars could …
We use 12000 stars from Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) spectroscopic data to show that the metallicities of Kepler field stars as given in the Kepler Input Catalog (KIC) systematically underestimate both the true metallicity and the dynamic range of the Kepler sample. Specifically, to the first order approximation, we find [Fe/H]_KIC = -0.20 + 0.43 [Fe/H]_LAMOST, with a scatter of ~0.25 dex, due almost entirely to errors in KIC. This relation is most secure for -0.3<[Fe/H]_LAMOST<+0.4 where we have >200 comparison stars per 0.1 dex bin and good consistency i…
Main sequence turn-off (MSTO) stars have advantages as indicators of Galactic evolution since their ages could be robustly estimated from atmospheric parameters. Hundreds of thousands of MSTO stars have been selected from the LAMOST Galactic sur- vey to study the evolution of the Galaxy, and it is vital to derive accurate stellar parameters. In this work, we select 150 MSTO star candidates from the MSTO stars sample of Xiang that have asteroseismic parameters and determine accurate stellar parameters for these stars combing the asteroseismic parameters deduced from the Kepler photometry and at…
Obtaining accurate and precise masses and ages for large numbers of giant stars is of great importance for unraveling the assemblage history of the Galaxy. In this paper, we estimate masses and ages of 6940 red giant branch (RGB) stars with asteroseismic parameters deduced from \emph{Kepler} photometry and stellar atmospheric parameters derived from LAMOST spectra. The typical uncertainties of mass is a few per cent, and that of age is $\sim$\,20 per cent. The sample stars reveal two separate sequences in the age -- [$α$/Fe] relation -- a high--$α$ sequence with stars older than $\sim$\,8\,Gyr…
The correlation between host star iron abundance and the exoplanet occurrence rate is well-established and arrived at in several studies. Similar correlations may be present for the most abundant elements, such as carbon and oxygen, which also control the dust chemistry of the protoplanetary disk. In this paper, using a large number of stars in the Kepler field observed by the LAMOST survey, it has been possible to estimate the planet occurrence rate with respect to the host star carbon abundance. Carbon abundances are derived using synthetic spectra fit of the CH G-band region in the LAMOST s…
We use the LAMOST spectra of member stars in Pleiades, M34, Praesepe, and Hyades to study how chromospheric activity vary as a function of mass and rotation at different age. We measured excess equivalent widths of H$α$, H$β$, and Ca~{\sc ii} K based on estimated chromospheric contributions from old and inactive field dwarfs, and excess luminosities are obtained by normalizing bolometric luminosity, for more than 700 late-type stars in these open clusters. Results indicate two activity sequences in cool spot coverage and H$α$ excess emission among GK dwarfs in Pleiades and M dwarfs in Praesepe…
$\require{mediawiki-texvc}$A stellar chromospheric activity database of solar-like stars is constructed based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Low-Resolution Spectroscopic Survey (LRS). The database contains spectral bandpass fluxes and indexes of Ca II H&K lines derived from 1,330,654 high-quality LRS spectra of solar-like stars. We measure the mean fluxes at line cores of the Ca II H&K lines using a 1 $Å$ rectangular bandpass as well as a 1.09 $Å$ full width at half maximum (FWHM) triangular bandpass, and the mean fluxes of two 20 $Å$ pseudo-continuum…
We present the results from a systematic study of temporal variation of stellar activity in young late-type stars. We used multi-epoch LAMOST low-resolution spectra of over 300 member candidates in three young open clusters: Pleiades, Praesepe, and Hyades. The spectral measurements of TiO band strength near 7050 Å (TiO2) and equivalent width of Hα line (EW Hα ) are used as the tracers of cool-spot coverage and chromospheric emission strength, respectively. The analysis of time-variation patterns of these two tracers suggested there exist detectable variabilities in TiO2 and EW Hα , and their t…
Orbital eccentricity is one of the basic planetary properties, whose distribution may shed light on the history of planet formation and evolution. Here, in a series of works on Planetary Orbit Eccentricity Trends (dubbed POET), we study the distribution of planetary eccentricities and their dependence on stellar/planetary properties. In this paper, the first work of the POET series, we investigate whether and how the eccentricities of small planets depend on stellar metallicities (e.g., [Fe/H]). Previous studies on giant planets have found a significant correlation between planetary eccentrici…
Phase \RNum{2} of the LAMOST-{\sl Kepler/K}2 survey (LK-MRS), initiated in 2018, aims at collecting medium-resolution spectra ($R\sim7,500$; hereafter MRS) for more than $50,000$ stars with multiple visits ($\sim60$ epochs) over a period of 5 years (2018 September to 2023 June). We selected 20 footprints distributed across the {\sl Kepler} field and six {\sl K}2 campaigns, with each plate containing a number of stars ranging from $\sim2,000$ to $\sim 3,000$. During the first year of observations, the LK-MRS has already collected $\sim280,000$ and $\sim369,000$ high-quality spectra in the blue …
Stellar Chromospheric Activity Database of Solar-like Stars Based on the LAMOST Low-Resolution Spectroscopic Survey: II. the bolometric and photospheric calibration
Rotation is a critical physical process operating in the formation of Am stars. There is a strong correlation between low-velocity rotation and chemical peculiarity. However, the existence of many non-CP slow rotators challenges the understanding of Am stars. The purpose of our work is to search for low-velocity rotating non-CP A-type stars and Am stars and to make a comparative analysis. In this paper, we pick out a sample from the LAMOST-Kepler project, including 21 Am stars, 125 non-CP slow rotators, and 53 non-CP fast rotators. We calculate the rotational frequencies through periodic chang…
We use the spectra of Pleiades and field stars from LAMOST DR2 archive to study how spottedness and activity vary as a function of mass at young ages. We obtained standard TiO band strength by measuring TiO bands near 7050 $Å$ from LAMOST spectra (R$\approx$1800) for large sample of field GKM dwarfs with solar metallicity. Analysis show that active dwarfs, including late G- and early K-type, have extra TiO absorption compare to inactive counterparts, indicating the presence of cool spots on their surface. Active late K- and M-dwarfs show deeper TiO2 and shallower TiO4 compare to inactive stars…
In our 2013 Astronomical Review article, we discussed the statistics of variability for 633 faint spectral type A-F stars observed by the Kepler spacecraft during Quarters 6-13. We found six stars that showed no variability with amplitude 20 ppm or greater in the range 0.2 to 24.4 cycles/day, but whose positions in the log g--Teff diagram place them in the delta Sct or gamma Dor pulsation instability regions established from pre-Kepler ground-based observations. Here we present results for 2137 additional stars observed during Quarters 14-17, and find 34 stars that lie within the instability r…
Stellar Chromospheric Activity Database of Solar-like Stars Based on the LAMOST Low-Resolution Spectroscopic Survey III. Calibrating the Chromospheric Basal Flux and the Connection to Stellar Rotation
Nanxun Innovation Institute, Zhejiang University of Water Resources and Electric Power（浙江水利水电学院南浔创新研究院）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；University of Chinese Academy of Sciences（中国科学院大学）；School of Physics and Optoelectronics Engineering, Anhui University（安徽大学物理与光电工程学院）
We identify member stars of more than 90 open clusters in the LAMOST survey. With the method of Fang et al.(2018), the chromospheric activity (CA) indices logR'CaK for 1091 member stars in 82 open clusters and logR'Hα for 1118 member stars in 83 open clusters are calculated. The relations between the average logR'CaK, logR'Hα in each open cluster and its age are investigated in different Teff and [Fe/H] ranges. We find that CA starts to decrease slowly from logt = 6.70 to logt = 8.50, and then decreases rapidly until logt = 9.53. The trend becomes clearer for cooler stars. The quadratic functi…
In this work we present the results of our analysis of 16,300 medium-resolution LAMOST spectra of late-type stars in the Kepler field with the aim of determining the stellar parameters, activity level, lithium atmospheric content, and binarity. We have used a version of the code ROTFIT specifically developed for these spectra. We provide a catalog with the atmospheric parameters (Teff, log(g), and [Fe/H]), radial velocity (RV), and projected rotation velocity (vsini). For cool stars (Teff < 6500 K), we also calculated the H-alpha and LiI-6708 equivalent width, which are important indicators of…
The radius valley, a dip in the radius distribution of exoplanets at ~1.9 Earth radii separates compact rocky Super-Earths and Sub-Neptunes with lower density. Various hypotheses have been put forward to explain the radius valley. Characterizing the radius valley morphology and its correlation to stellar properties will provide crucial observation constraints on its origin mechanism and deepen the understanding of planet formation and evolution. In this paper, the third part of the Planets Across the Space and Time (PAST) series, using the LAMOST-Gaia-Kepler catalog, we perform a systematical …
We present the results of a study of a large sample of A and Am stars with spectral types from LAMOST and light curves from WASP. We find that, unlike normal A stars, $δ$ Sct pulsations in Am stars are mostly confined to the effective temperature range 6900 $<$ $T_{\rm eff}$ $<$ 7600 K. We find evidence that the incidence of pulsations in Am stars decreases with increasing metallicism (degree of chemical peculiarity). The maximum amplitude of the pulsations in Am stars does not appear to vary significantly with metallicism. The amplitude distributions of the principal pulsation frequencies for…
By using the LAMOST time-domain survey data, we study stellar activities based on the $\rm{H_α}$ lines for about 2000 stars in four $K$2 plates. Two indices, $R_{\rm{Hα}}^{'}$ and $R_{\rm{Hα}}^{+}$, are computed from LAMOST spectra, the former of which is derived by excluding the photospheric contributions to the $\rm{H_α}$ lines, while the latter is derived by further subtracting the non-dynamo driven chromospheric emission. Meanwhile, the periodicity and variation amplitudes are computed from \emph{K2} light curves. Both the $R_{\rm{Hα}}^{'}$-Ro relation and $R_{\rm{Hα}}^{+}$-Ro relation sho…
We probed stellar X-ray activity over a wide range of stellar parameters, using {\it Chandra} and LAMOST data. We measured the X-ray-to-bolometric luminosity ratio ($R_X = L_X/L_{\rm bol}$) for 484 main-sequence stars, and found a bimodal distribution for G and K types. We interpret this bimodality as evidence of two sub-populations with different coronal temperatures, which are caused by different coronal heating rates. Using the metallicity and velocity information, we find both of the two sub-populations are mostly located in the thin disk. We find no trend of $R_X$ with stellar age for sta…
Planets Across Space and Time (PAST) IV: The Occurrence and Architecture of Kepler Planetary Systems as a Function of Kinematic Age Revealed by the LAMOST-Gaia-Kepler Sample
Our knowledge of magnetic activity of stars is mostly based on the study of the Sun and some spectroscopic surveys of a few hundreds of stars. However, the detailed mechanisms of the solar magnetic activity cycle are not fully understood. With the Kepler mission that is providing exquisite photometric data for hundred of thousands of stars monitored continuously for more than three year, we can study changes in the light curves that can be related to magnetic activity. We show here a few examples of stars for which we did a time-frequency analysis to look for such signature.
Light curves of solar-type stars often show gradual fluctuations due to rotational modulation by magnetic features (starspots and faculae) on stellar surfaces. Two quantitative measures of modulated light curves are employed as the proxies of magnetic activity for solar-type stars observed with Kepler telescope. The first is named autocorrelation index $i_{AC}$, which describes the degree of periodicity of the light curve, the second is the effective fluctuation range of the light curve $R_{eff}$, which reflects the depth of rotational modulation. The two measures are complementary and depict …
We present a sample of 2700 Ap stars in LAMOST DR9. The candidates are first selected to be in a temperature range typical of Ap stars by using the $BP$-$RP$ color index from Gaia DR3. Then the 5200\,Å flux depression features characteristic of Ap stars are visually checked in LAMOST DR9 spectra. The detailed spectral features are given by applying a modified spectral classification program, MKCLASS. Stellar parameters of these Ap stars such as $T_{\rm eff}$, $\log g$, [Fe/H], [Si/H], and $v{\sin}i$ are either extracted from a hot star catalog or derived through empirical relations and then a …
Using data of fast-rotating active dwarf stars in the Kepler database, we perform time-frequency analysis of the light curves in order to search for signs of activity cycles. We use the phenomenon that the active region latitudes vary with the cycle (like the solar butterfly diagram), which causes the observed rotation period to change as a consequence of differential rotation. We find cycles in 8 cases of the 39 promising targets with periods between of 300-900 days.
We present a sample of $\sim$ 140,000 primary red clump (RC) stars of spectral signal-to-noise ratios higher than 20 from the LAMOST Galactic spectroscopic surveys, selected based on their positions in the metallicity-dependent effective temperature--surface gravity and color--metallicity diagrams, supervised by high-quality $Kepler$ asteroseismology data. The stellar masses and ages of those stars are further determined from the LAMOST spectra, using the Kernel Principal Component Analysis method, trained with thousands of RCs in the LAMOST-$Kepler$ fields with accurate asteroseismic mass mea…
The dynamo process is believed to drive the magnetic activity of stars like the Sun that have an outer convection zone. Large spectroscopic surveys showed that there is a relation between the rotation periods and the cycle periods: the longer the rotation period is, the longer the magnetic activity cycle period will be. We present the analysis of F stars observed by Kepler for which individual p modes have been measure and with surface rotation periods shorter than 12 days. We defined magnetic indicators and proxies based on photometric observations to help characterise the activity levels of …
Magnetic activity of ultracool dwarfs in the LAMOST DR11
Yunnan Observatories, Chinese Academy of Sciences（云南天文台，中国科学院）；Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences（天文物理重点实验室，中国科学院）；International Centre of Supernovae, Yunnan Key Laboratory（超新星国际中心，云南重点实验室）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（天文与空间科学学院，中国科学院大学）
We analyse light curves covering four years of 39 fast-rotating ($P_\mathrm{rot}< 1d$) late-type active stars from the Kepler database. Using time-frequency analysis (Short-Term Fourier-Transform), we find hints for activity cycles of 300-900 days at 9 targets from the changing typical latitude of the starspots, which, with the differential rotation of the stellar surface change the observed rotation period over the activity cycle. We also give a lowest estimation for the shear parameter of the differential rotation, which is ~0.001 for the cycling targets. These results populate the less stud…
The properties of the acoustic modes are sensitive to magnetic activity. The unprecedented long-term Kepler photometry, thus, allows stellar magnetic cycles to be studied through asteroseismology. We search for signatures of magnetic cycles in the seismic data of Kepler solar-type stars. We find evidence for periodic variations in the acoustic properties of about half of the 87 analysed stars. In these proceedings, we highlight the results obtained for two such stars, namely KIC 8006161 and KIC 5184732.
The relation between magnetic activity and rotation in late-type stars provides fundamental information on stellar dynamos and angular momentum evolution. Rotation/activity studies found in the literature suffer from inhomogeneity in the measure of activity indexes and rotation periods. We overcome this limitation with a study of the X-ray emitting late-type main-sequence stars observed by XMM-Newton and Kepler. We measure rotation periods from photometric variability in Kepler light curves. As activity indicators, we adopt the X-ray luminosity, the number frequency of white-light flares, the …
We present an analysis of flare activity in wide binary stars using a combination of value-added data sets from the NASA Kepler mission. The target list contains a set of previously discovered wide binary star systems identified by proper motions in the Kepler field. We cross-matched these systems with estimates of flare activity for $\sim$200,000 stars in the Kepler field, allowing us to compare relative flare luminosity between stars in coeval binaries. From a sample of 184 previously known wide binaries in the Kepler field, we find 58 with detectable flare activity in at least 1 component, …
Due to its unique long-term coverage and high photometric precision, observations from the Kepler asteroseismic investigation will provide us with the possibility to sound stellar cycles in a number of solar-type stars with asteroseismology. By comparing these measurements with conventional ground-based chromospheric activity measurements we might be able to increase our understanding of the relation between the chromospheric changes and the changes in the eigenmodes. In parallel with the Kepler observations we have therefore started a programme at the Nordic Optical Telescope to observe and m…
The light curves of solar-type stars present both periodic fluctuation and flare spikes. The gradual periodic fluctuation is interpreted as the rotational modulation of magnetic features on the stellar surface and is used to deduce magnetic feature activity properties. The flare spikes in light curves are used to derive flare activity properties. In this paper, we analyze the light curve data of three solar-type stars (KIC 6034120, KIC 3118883, and KIC 10528093) observed with Kepler space telescope and investigate the relationship between their magnetic feature activities and flare activities.…
LAMOST J113208.06-005052.3 and LAMOST J052957.56+344127.0: two new binaries with a hot white dwarf and a flaring companion star
Institute of Astrophysics, Chuxiong Normal University（楚雄师范学院天体物理研究所）；International Centre of Supernovae (ICESUN), Yunnan Key Laboratory（超新星国际中心（ICESUN），云南省重点实验室）；Faculty of Science, Kunming University of Science and Technology（昆明理工大学理学院）
