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LAMOST observations in the Kepler field. II. Database of the low-resolution spectra from the five-year regular survey

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 acquired through 2015 May to 2017 June together with the first round observations of the LK-project from 2012 June to 2014 September. The LK-project now counts 227 870 spectra of 156 390 stars, among which we have derived atmospheric parameters (log g, T eff and [Fe/H]) and heliocentric radial velocity (RV) for 173 971 spectra of 126 172 stars. These parameters were obtained with the most recent version of the LAMOST Stellar Parameter Pipeline v 2.9.7. Nearly one half, namely 76 283 targets, are observed both by LAMOST and Kepler telescopes. These spectra, establishing a large spectroscopy library, will be useful for the entire astronomical community, particularly for planetary science and stellar variability on Kepler targets.


INTRODUCTION
The Kepler satellite was launched on 2009 March 7th by NASA with the aim of searching for Earth-sized planets around Solar-like stars (Borucki et al. 2010). Before its second of four reaction wheels on board failed on 2013 May 11th, Kepler had been continuously monitoring about 200 000 stars together within a 105 deg 2 field in the constellations Cygnus and Lyrae region for a period of ∼ 4 yr. These unprecedented high-quality photometric data are goldmines for the field of asteroseismology (Gilliland et al. 2010), as well as for many other science cases (see, e.g., eclipsing binaries in Prša et al. 2011). Nevertheless, to uncover indepth physics for interesting targets with Kepler photometry, it is crucial that the input atmospheric parameters of stars are available beforehand, such as for the successful asteroseismology depending somewhat on the effective temperature (T eff ), surface gravity (log g) and metallicity ([M/H]) measured first from spectroscopy, that could reduce the size of parameter space to find the optimal seismic models (see, e.g., Cunha et al. 2007;Charpinet et al. 2011). The Kepler Input Catalog (KIC; Brown et al. 2011) provides stellar parameters of potential interesting targets which are derived mainly from photometry in the SDSS-like photometric bands (Doi et al. 2010) but the precision of KIC is not high enough for asteroseismic modeling, particular for hot and peculiar stars (Molenda-Żakowicz et al. 2011;McNamara et al. 2012;Huber et al. 2014). There are many additional endeavors to improve the precision of atmosphere parameters for seismic aims with ground-based spectroscopic data (see, e.g., Uytterhoeven et al. 2010;Thygesen et al. 2012;Niemczura et al. 2015). It is inevitable that these projects are not allocated sufficient observation time to fully cover all ∼ 200 000 Kepler targets, except telescope installed with a large number of fibers. In addition, the spectroscopic data from different instruments may suffer systematic uncertainties. Recently, spectroscopic follow-up works in the Kepler field for asteroseismolgy have also been performed by the APOKASC with the multiple fibers of SDSS telescope, which is a part of a survey of APOGEE (Serenelli et al. 2017;Majewski et al. 2017;Pinsonneault et al. 2018).
The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST, also called Gou Shoujing Telescope) is an ideal instrument for follow-up spectroscopic observations on Kepler stars. It combines a large aperture (3.6-4.9 m) with a wide field of view (circular FOV with the diameter of 5 • ) and is equipped with 4000 fibers at its focus (Wang et al. 1996;Xing et al. 1998). LAMOST spectra have a low resolution R ∼ 1800 and cover the wavelength range from 370 nm to 900 nm (see details in Cui et al. 2012;Zhao et al. 2012). To take advantage of the ability of LAM-OST to acquire many spectra at a time over a large field of view, the LAMOST-Kepler (LK) project was initiated with the scientific goal to observe as many objects in the Kepler FOV as possible from the test and pilot survey phase of LAMOST onwards (De Cat et al. 2015, hereafter Paper I). This strategy provides a homogeneous determination of both the atmosphere parameters (i.e., the surface gravity log g, the effective temperature T eff and the metallicity [Fe/H]) and the spectral classification of the observed objects. The low resolution spectra can also be used to estimate the radial velocity (RV) and the projected rotational velocity (v sin i) for the rapid rotation stars.
During the first round of observation, from 2011 May to 2014 September, the LK-project had obtained 101 086 low resolution spectra, covering about 21% of 200 000 Kepler stars (Paper I). These spectra had been independently analyzed by three different groups: (i) the "Asian team" (Ren et al. 2016) performed a statistical analysis of the stellar parameters based on the LAMOST stellar parameter pipeline (LASP; Wu et al. 2011Wu et al. , 2014Luo et al. 2015); (ii) the "European team"  determined the stellar parameters, the spectral classification, and the activity indicators with an updated version of the code ROTFIT (Frasca et al. 2003(Frasca et al. , 2006; (iii) the "American team" (Gray et al. 2016) developed the code MKCLASS which automatically classifies stellar spectra on the MK system independent of the stellar parameter determination (see details in Gray & Corbally 2014). The LAMOST-Kepler spectra, by establishing a spectroscopic database, have made an impact on many scientific areas, particular for the research within the Kepler community. These spectra cover the Lithium line at 670.8 nm and were used to discover the first confirmed Li-rich core-helium-burning giant . The spectra also cover the Ca II H and K lines at 396.85 and 393.37 nm, respectively, which have been used to measure the chromospheric activity on the stellar surface for 5648 solar-like stars within the Kepler field based on LK spectra (Karoff et al. 2016). With the help of LAMOST spectra, the metallicity of the open cluster NGC 6866 has been determined to be similar with the solar value (Bostancı et al. 2015). These spectra are also very useful for individual asteroseismic cases such as the red giant star KIC 5689820 (Deheuvels et al. 2014) and the mainsequence A-type pulsating star KIC 7917485 (Murphy et al. 2016). With the metallicity derived from the LAMOST-Kepler spectra, Smalley et al. (2017) found evidence that the incidence of pulsations in Am stars decreases with increasing metallicity. The LAMOST metallicity has also play an important role in the research of Kepler exoplanets where an excess of hot rocky Kepler planets was found to be preferentially orbiting around metal-rich stars (Mulders et al. 2016) and a new population of short-period (P < 10 d) exoplanets with sizes R p = 2 − 6R ⊕ that resemble hot Jupiters was discovered in preferentially occurring around metal-rich hosts and in single-transiting systems. . With the atmospheric parameters derived from LK-project spectra, stars hosting multiple transiting planets are found with typically near circular or coplanar orbits which is similar to our Solar system (Xie et al. 2016) while Kepler singles are on average eccentric (ē ≈ 0.3). The LK sample is also helpful for investigating the intrinsic architecture of Kepler planetary systems, showing that the frequency of Kepler-like planetary systems is about 30% (Zhu et al. 2018). In addition, the LK-project is a part of a large spectroscopic survey for Galactic archaeology (see, e.g., Xiang et al. 2017). Given the importance of these spectra, we report in this paper the second round of spectroscopic observations in the Kepler field with the LAMOST telescope from 2015 May to 2017 June. We also include the spectra obtained from the first round observations since they are now extracted and analyzed with the most up-to-date pipelines. The structure of this paper is organized as follows: we first describe the details of the observations for this second round in Section 2, while the database of this version of spectra acquired is given in Section 3, with the discussion followed in Section 4, and we end with a brief summary.

OBSERVATIONS
As LAMOST has a focal plane of 5 degrees in diameter, a minimum of 14 circular LAMOST pointings (or footprints) is needed to cover the 105 square degrees of the Kepler field.
We refer to these individual footprints as LK-fields and the details of classification of each field can be seen in Paper I. The observed plates are called "V-plates", "B-plates", "Mplates", and "F-plates" for targets with the magnitudes of 9 < r 14, 14 < r 16.3, 16.3 < r 17.8, and 17.8 < r 18.5, respectively. In the first round of LK-project observations, we focused on stars which were included on the list of possible targets of the KASC 1 (Paper I). The targets for each plate were selected from a prioritized target list for the second round of observations, compiled from two main types of objects from high to low priority. (1) The 168,151 objects observed by the Kepler mission for which no high-quality LAMOST spectrum without potential issues (no entries in column 14 of Table 4 or column 16 of Table 5 of Paper I) was available after the first round of observations were considered as the new "science targets". Within this category, the seismology targets received a higher priority than the planetsearch targets. (2) The new "field stars" consisted of three kinds of objects in order of decreasing priority: (a) the 31 567 Kepler targets already having a clean high-quality LAMOST spectrum (to allow multi-epoch observations for quality assessment and variability studies), (b) the objects in the KIC that were not observed by Kepler, and (c) other stars in the fields-of-view with V < 18 mag from the USNO-B catalog (Monet et al. 2003) Given the constraints of both the pointing ability of the LAMOST and the visibility of the Kepler field, observations can only be done from late-May to mid-October with a maximal observation window of four hours. In addition, LAMOST is closed during about two months per year in summer due to the Monsoon. Therefore, it takes three or four seasons for LAMOST to have a full coverage of the whole Kepler field, considering the weather conditions as well. Table 1 lists the general information of observations made in each year through the regular survey phase of LAM-OST from 2012 to 2017. The multiple visited targets are counted if spectra were observed with R.A. and DEC. within 3.7 arcsec 2 and magnitude difference less than 0.01 mag. The LK-project has been carried out for two rounds of observations, meaning that all the 14 subfields have been observed at least once in each round. We note that the observations during the phase of the pilot survey of LAMOST have not been processed with the newest version of the pipeline (c.f. Section 3.1) and are not considered here. It only concerns a small amount of data.
The details of observations of the first round of the LKproject from 2012 to 2014 are given in Paper I. Here we focus on the second round of observations of the LK-project, which began on 2015 May 29 and ended on 2017 June 15. A total of 48 plates were observed on 24 observation nights: 32 plates on 18 nights in 2015 and 16 plates on 6 nights 2017. Table 2 lists the overview information of the observed plates for the second round of the LK-project. The very bright "V-plates" were mainly observed as well as a small fraction of bright "Bplates", with typical exposure times of 3 × 10 minutes and 3 × 25 minutes, respectively, depending on the observation conditions.  Note-For each plate, we give the sequence number of the plate (PlateID), the reference of the LK-field (LK#), the plan identification number (PlanID), with the associated right ascension (R.A. (2000)) and declination (DEC. (2000)) of the central star on that plate, the observed date (Date), the air turbulence in Xinglong (seeing), and the time of each exposure (Exposure time). Note that the plate KP193708N401249V04 was observed on 2017-06-12 but it suffered from a bad weather condition and all spectra have a very low signal-to-noise. We therefore did not include that plate in this table. a The unusual exposure time happened because the plate moved out of the observable view of LAMOST, two hours before and after its meridian, respectively.

Data reduction process
One of the main products of LAMOST provided to astronomers is the wavelength and flux-calibrated spectra, which are processed by an automatic data reduction and data analysis pipeline (see details in Luo et al. 2012Luo et al. , 2015. The version v2.9.7 pipeline is used for the spectra obtained in the five-year regular survey of LAMOST from 2012 to 2017. After the quality evaluation of the observations (e.g., seeing and cloud coverage) and telescope performance, the raw CCD frames are fed to the 2D pipeline which uses procedures similar to those of SDSS (Stoughton et al. 2002), to produce calibrated 1D spectra. The main tasks of the 2D pipeline include dark and bias subtraction, flat field correction, spectral extraction, sky subtraction, wavelength calibration, stacking sub-exposures and combining of different wavelength bands (the detailed description can be found in Paper I and Luo et al. 2015). The 1D pipeline is aimed at the analysis of the LAMOST spectra and provides the classification of spectral type and the measure of RVs (for stars) or redshifts (for galaxies and quasi-stellar objects). This goal is reached with the help of a template-matching and line-recognition algorithm. The library of stellar templates was constructed based on the classification of about one million LAMOST DR1 stellar spectra (Wei et al. 2014).

Data release
The calibrated spectra are released to the astronomical community at regular intervals, typically once every year, and the pipelines are updated every one or two years, during the regular surveys of LAMOST. After two rounds of observations of the LK-project, we have collected 227 870 flux-and wavelength-calibrated, sky-subtracted low resolu- tion (R = 1800) spectra, among which 173 971 ones have been used to calculate the stellar atmospheric parameters with the LASP pipelines. These data will be released to the public along with the fifth data release (DR5 3 ) of all the LAMOST survey spectra in June 2019. They then can be freely downloaded from the official LAMOST website 4 . Figure 1 illustrates the spatial distribution of the stars observed within the LK-project from 2012 to 2017. The spatial distribution of the entire data set cover almost the entire area of the Kepler field. There are 76 283 5 stars which are both observed by LAMOST and have Kepler photometry, corresponding to a fraction of more than a third of the full database of stars observed for the LK-project. We now have LAMOST data for about 38.2% of the ∼ 200, 000 objects that have been 3 http://dr5.lamost.org 4 www.lamost.org 5 The number is obtained through cross-identification between the two datasets on the basis of coordinate separation of 3.0 arcsec. We note that the number would decrease when we use more strict constraints to perform cross-identification. For instrance, the number would be around 60 000 if we would use a maximum coordinate separation of 0.4 arcsec and a magnitude difference of less than 0.01 mag. observed during the Kepler mission. The central hole of each plate is reserved to a bright (V < 8) star which is used for the active optics wavefront sensor to shape the mirror getting rid of deformation of the wavefront from external influences. The coordinates of that star also defines the coordinates of the observed plate. Four guide stars (V < 17) are observed by the guiding CCD cameras placed at the four corners of the LAMOST field of view. Figure 2 shows the histogram of the Kepler magnitude (Kp) distribution for the 146 001 stars, including dwarfs and giants. There are additional 10 389 stars that are not included among them because they are the LAM-OST standard stars or stars without Kp magnitude available from the DR5 catalog. Here we separate dwarfs from giants by their measured surface gravity with a boundary of log g = 3.5. The histogram of Figure 2 clearly reveals that most targets fall into the range of Kp 11-14, with a small fraction of brighter and fainter targets. This histogram also depicts the observation strategy of the LK-project under different observation conditions. The observations concentrate on very bright plates (see Table 2, and Table 3 of Paper I), which can make full use of bright nights or nights with unfavorable weather conditions such as poor seeing or low atmospheric transparency. Consequently, a sharp cutoff appears at Kp = 14 which is the boundary between the V-plates and the B-plates. Figure 3 displays the data quality showing the distributions of the signal-to-noise ratios (S/Ns) in SDSS u, g, r, i, and z bands. We note that the spectra with S /N g 6 can be used to derive valid stellar parameters for type A, F, G and K stars with the LASP pipeline if they are obtained in dark nights (eight nights before and after the new moon). However, the criterion of S /N g increases to 15 for the spectra obtained in bright nights (all other nights except the three nights around the full moon). One can see more details of setting those criteria for calculation of atmospheric parameters in Luo et al. (2015). After two rounds of LK-project observations, we observed merely 29 505, 40 916, and 53 047 spectra with S /N g 6, S /N g 10 and S /N g 15, observed during both bright and dark nights, which correspond to percentages of ∼ 12.95%, ∼ 17.96% and ∼ 23.28%, respectively. Table 3 lists the full catalog of the constructed database that is available for the entire LK-project. This table contains the following columns: Column 1: Obsid is the unique identification number ID of the observed 1D spectrum.
Column 2: the cross-identification of the target in Kepler input catalog within the coordinate separation of three arcsec 6 .

Charaterization of atmospheric parameters
Among these 227 870 spectra, we provide stellar parameters for 173 971 spectra with the LASP pipeline, as the spectra quality is high enough to achieve an accurate and reliable determination of parameters for the AFGK-types of stars (with S/N g 6 and S/N g 15 of spectra observed in dark and bright nights, respectively, see details in Luo et al. 2015). We note that 51 503 targets have been observed more than once (16× for the most observed stars) and the total number of stars is 156 390. There are 65 529 Kepler stars with LASP atmospheric parameters among the 76 283 stars in common. We now have LASP parameters for about 32.8% of the objects that have been observed during the Kepler mission. Figure 4 shows the log g v.s. T eff plane (also called Kiel diagram) for the spectra with sufficient quality. The distribution of targets differs slightly but not significantly, which therefore is not provided here again. The surface gravities are found mainly between 5 and 1 dex, while the effective temperature is mainly in the range of [4000, 8000] K. Most stars have metallicities near to the value of the Sun. We clearly see that most of them locate in either the main sequence or the red giant branch. We note that the giant branch correctly displaces towards higher temperatures as the metallicity decreases. Figure 5 shows the histograms of the stellar parameters T eff , log g, [Fe/H] and the radial velocity. The distribution of effective temperature, T eff , shows a structure where two distinct peaks are found around 4700 and 5700 K, which are the projection of the giants and the main sequence stars from Figure 4, respectively. The surface gravity, log g, also presents two distinct peaks near 2.5 and 4.2 which, again, correspond to the projection of the giant and the main sequence stars, respectively. The metallicity spans the range from ∼ −2.0 to 0.7 dex and peaks around the solar metallicity, which suggests that most stars have a nearly solar metallicity. There are 1 114 stars with [Fe/H] < −1.0 and 65 stars with [Fe/H] < −2.0, which we consider as candidate metal-poor stars and very metal-poor stars, respectively. They could be the fossils of the early generation of stars and can provide fundamental information on the chemical abundances, formation and evolution of the early evolutionary stage of the Galaxy (see, e.g., Li et al. 2015;McWilliam et al. 1995). Most stars are found with radial velocities around −20 km/s. However, in the long tail of the RV distribution, we find 29 and 216 stars with RV < −400 km/s and −300 km/s, which are candidates of high-velocity stars (see, e.g., Zhong et al. 2014). The properties of these stars can be used to determine their original nature and formation mechanisms and aid the study of the structural properties of the Galaxy (see, e.g., Gvaramadze et al. 2009).

DISCUSSION
After completing the entire two-round observations of the LK-project, we have collected 227 870 low resolution spectra of 156 390 stars and provided atmospheric parameters with 173 971 spectra of 126 172 stars. We remark that the low resolution spectra in the first round observations were mainly produced from the LASP pipeline with version 2.7.5. The parameter comparison from those two different versions is reported in the data release note of DR5 website 7 , where it is shown that the atmospheric parameters T eff , log g, [Fe/H] and RV are within their errors for the stars in common between DR3 and DR5. We note that, for stars within the LK-project, the parameters are also essentially the same, as displayed by the similarity of Figure 6 in Paper I with Figures 4 and 5 here. The slight difference between the two Kiel diagrams is mainly the result of excluding from the analysis the parameters of hot stars (OB-types) because the LASP pipeline is optimized for AFGK-type stars and could lead to untrustable results in other cases. Nevertheless, as the size of the sample has increased, we observe more interesting targets such  as candidates of very low metallicity stars and high-velocity stars (see histograms of Figure 6 of Paper I and our Figure 5).
For the spectral database of only the first round of the LK-project, Ren et al. (2016) calibrated the atmospheric parameters derived from LASP by comparing them with the values measured from either high-resolution spectroscopy or asteroseismology for the stars in common with the catalog of Huber et al. (2014). A similar comparison was also performed by Dong et al. (2014Dong et al. ( , 2018 and Wang et al. (2016). Ren et al. (2016) provide the external errors of T eff , log g and [Fe/H] for giants and dwarfs, respectively. The internal errors have also been estimated with the values derived from multiple spectra of the same stars. A forthcoming paper (Y. Pan et al., 2018, in prep.) will focus on the same topic with a database more than twice the previous spectral library, from 61 226 to 173 971. The number of common stars which have been observed by both Kepler and LAMOST is 76 283, a number larger than twice the data size of Ren et al. (2016). In addition, the previous spectra have been re-analyzed with the updated version of the LASP code, v2.9.7, where the determination of uncertainty of radial velocity is improved significantly. The new calibration examines the reliability of the previous results provided by Ren et al. (2016), to establish more generic calibration formulae.
Other groups, including the "European" and "American" teams, are applying their own codes to these spectra for the determination of basic stellar parameters. The "European team" (Molenda-Żakowicz et al., in prep) is determining the atmospheric parameters, the spectral classification, the projected rotational velocity (for ultrafast rotators only) and activity indicators with the latest adapted version of the code ROTFIT, for the entire database extending the results of their previous work ). The "American team" (R. O. Gray et al., 2018, in prep.) is performing an accurate MK classification with the automatic code MKCLASS, which is independent of the determination of atmospheric parameters (see details in Gray et al. 2016).
The current LASP and the above pipelines have not yet incoporated the templates for hot and highly evolved stars, including the O and B type main-sequence stars, the white dwarfs and the hot subdwaf stars. With the previous LAM-OST data (including the LK-project's), several independent works have been concentrated on highly evolved compact stars, aiming at the characterization and determination of stellar parameters for white dwarfs (Guo et al. 2015;Zhao et al. 2013) as well as hot subdwafs (Luo et al. 2016). These stars, which are not analyzed by the LASP code, are scientifically valuable when their parameters are derived by specialized outside pipelines or models (see, e.g., Su et al. 2017).
In line with the initial goals for the LK-project, there are fruitful results being generated based on this catalog to-gether with the Kepler photometry. While in depth studying the Kepler targets based on the whole database, a crossidentification was established between the catalog of the LAMOST DR4/DR5 and the Kepler archive, with a tolerance of three arcsec in coordinates separation (A. Luo et al., 2018 in prep.), which is useful to give the contamination factor of the targets that are affected by their neighbor sources during the Kepler observations (see also Table 5 of Paper I which lists this value for the DR3 data). For the stars with large contamination factor, one should be extremely careful since those targets may be very close to their neigbor objects and a wrong star observed by LAMOST cannot be ruled out.
The astronomical community can exploit the spectra of such a vast database for researches in many different fields, such as stellar activity, binaries and asteroseismology. Yang et al. (2017) provided a comprehensive investigation of stellar flare events in M-dwarfs in the Kepler field with the Hα emission lines illustrated from the LAMOST spectra. There are 483 stars with multiple (5+) spectra which can be used to check the variations of radial velocities, serving as an independent technique to discover new binary systems and to solve their orbital parameters (see, e.g., Catanzaro et al. 2018). A major goal of the LK-project is to provide accurate parameters for pulsating stars since their pulsations can be measured to a precision of a few tenth of a nano hertz from the Kepler photometry (see, e.g., Zong et al. 2016), which are key input parameters for the seismic modeling of pulsating stars.
A drawback of the LK-project is that the Kepler orignal field can only be reached by LAMOST during the summer season when the weather conditions typically show a high precipitation due to the Monsoon (Paper I). Therefore, to fully extend the capacity of LAMOST, providing spectra for targets with high-quality photometry, we select six K2 campaigns (i.e., C0, C1, C4, C5, C6 and C8; Howell et al. 2014) whose declinations are higher than −10 • , hence reachable by LAMOST to carry out the LAMOST-K2 project observations. Each field is divided into 14 subfields, similar to the LK subfields. During a period from 2014 to 2017, a total of 151 plates had been observed over 108 nights, with a collection of 291 956 spectra for 222 926 stars (J. Wang et al., 2018, in prep.). The calibration of log g between the asteroseismic determination and the LASP code have been obtained by Zhang et al. (2018, in prep.). We also mention that a current proposal of LAMOST has been approved for the follow-up observations to the region near the north ecliptic pole where the TESS mission will observe continuously with a duration of about one year (Ricker et al. 2014).
As LAMOST had finished its first five-year regular survey in 2017 summer, several insteresting proposals had been approved, in particular observations related to the LK-project. One of them is the time-series spectroscopic observations for the targets in the field of Kepler and K2, with 16 middleresolution (R ∼ 7500) spectrographs but for two different arms, with the wavelength ranges of 630-680 nm and 495-535 nm, respectively. Observations of the test plate (i.e., LK07) have been completed on 2018 May 24, 28-31. The preliminary data set of parameters contains about 1800 targets with most of them revisited of 30 times. A forthcoming paper will concentrate on the test results. All the data will be available publicly after 2020 September along with the DR6.

SUMMARY
The LK-project, as a support for follow-up spectroscopic observations for Kepler photometry, aims at providing spectra for investigating a variety of physics of the stars observed by Kepler. During the first five-year regular survey phase, the original Kepler field has been observed by LAMOST on 83 plates over 49 nights from 2012 June to 2017 June, accumulating 227 870 spectra of 156 390 stars. From the cross identification of ∼ 200 000 targets with available Kepler photometry, we find 76 283 stars in common between LAM-OST and Kepler with constraints on the coordinate separation (d < 3.0 arcsec).
At the current stage, we have obtained stellar parameters with 173 971 spectra of 126 172 stars of type A, F, G and K star with the LASP pipeline v2.9.7, which provide hundreds of candidates of high-velocity stars and metal-poor or very metal-poor stars. A process of homogenization between our data and the products of other works is ongoing. This work will certainly provide us with a more robust estimation of the derived parameters. These spectra will be useful for the entire astronomical community in particular for investigating planetary science and stellar physics of Kepler targets.
Although LAMOST has completed its first five-year regular survey, the LK-project will be continued in the next years to provide more spectra. In parallel to the LK-project, there are several approved programs to use LAMOST for follow-up observations of targets of already operating and forthcoming space missions such as K2 and TESS satellites. In order to provide time-series spectroscopy, one footprint on K2 C0 field has been continuously observed for more than ten times. A very similar project is under test while LAMOST is equipped with intermediate-resolution spectrographs. Astronomers who are interested in those spectra can contact the members of the LAMOST consortium 8 . (1) (2) (3) (4) (5) (6) (7) a Obsid is the "fingerprint" of that spectrum. One can keep the obsid if they want to get more information of that spectrum. It can be easily accessed though the official LAMOST website searching engine: dr5.lamost.org/search b One should be careful when using the KIC identification if it has a large separation ∆d or conficts with its tcomment (input target).