Sky Area Research Articles

The Study of Helium Variations in Star Clusters Using China Space Station Telescope

The China Space Station Telescope (CSST) is a 2 m space-based optical-UV telescope. Its primary goal is to carry out a high-resolution photometric imaging survey of a 17,500 square degree sky area using the on board Survey Camera. With its wide field of view (1.1 square degrees) and a mosaic imager containing 640 million pixels, studying the different populations of stars within star clusters is highly feasible. The aim of this study is to assess the CSST’s ability to distinguish between stellar populations with varying helium abundance levels, with the help of Modules for Experiments in Stellar Astrophysics. The results of the CSST’s photometry for these different populations are presented by transferring the models into the CSST Survey Camera photometric system. The findings confirm that helium-enriched stellar populations will have unique patterns in the color–magnitude diagrams under the CSST photometric system, compared to normal stellar populations. The CSST, with its filters and wide field of view of the Survey Camera, provides a new avenue for the study of multiple populations in star clusters.

Parameter estimation of LAMOST Medium-Resolution Stellar Spectra

ABSTRACT This paper investigates the problem of estimating three stellar atmospheric physical parameters and 13 elemental abundances for medium-resolution spectra from Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). Typical characteristics of these spectra are their huge scale, wide range of spectral signal-to-noise ratio (S/N), and uneven distribution in parameter space. These characteristics lead to unsatisfactory results on the spectra with low temperature, high temperature, or low metallicity. To this end, this paper proposes a stellar parameter estimation method based on multiple regions (SPEMR) that effectively improves parameter estimation accuracy. On the spectra with S/N ≥ 10, the precisions are 47 K, 0.08 dex, 0.03 dex, respectively, for the estimations of (Teff, $\log \, g$, and $\rm [Fe/H]$), 0.03–0.06 dex for elements C, Mg, Al, Si, Ca, Mn, and Ni, 0.07–0.13 dex for N, O, S, K, and Ti, while that of Cr is 0.16 dex. For the reference of astronomical science researchers and algorithm researchers, we released a catalogue for 4.19 million medium-resolution spectra from the LAMOST DR8, experimental code, trained model, training data, and test data.

Foreground separation and constraints on primordial gravitational waves with the PICO space mission

PICO is a concept for a NASA probe-scale mission aiming to detect or constrain the tensor to scalar ratio r, a parameter that quantifies the amplitude of inflationary gravity waves.We carry out map-based component separation on simulations with five foreground models and input r values r in = 0 and r in = 0.003. We forecast r determinations using a Gaussian likelihood assuming either no delensing or a residual lensing factor A lens = 27%. By implementing the first full-sky, post component-separation, map-domain delensing, we show that PICO should be able to achieve A lens = 22% – 24%. For four of the five foreground models we find that PICO would be able to set the constraints r < 1.3 × 10-4 to r < 2.7 × 10-4 (95%) if r in = 0, the strongest constraints of any foreseeable instrument. For these models, r = 0.003 is recovered with confidence levels between 18σ and 27σ. We find weaker, and in some cases significantly biased, upper limits when removing few low or high frequency bands. The fifth model gives a 3σ detection when r in = 0 and a 3σ bias with r in = 0.003. However, by correlating r determinations from many small 2.5% sky areas with the mission's 555 GHz data we identify and mitigate the bias. This analysis underscores the importance of large sky coverage. We show that when only low multipoles ℓ ≤ 12 are used, the non-Gaussian shape of the true likelihood gives uncertainties that are on average 30% larger than a Gaussian approximation.

Evidence of a common origin for the Virgo overdensity and Hercules-Aquila Cloud from abundances and orbital parameters

Aims. The Virgo overdensity (VOD) and the Hercules-Aquila cloud (HAC) may have originated from the same accretion event. In this work, we use K giants from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey to further investigate their potentially common origins. Methods. We selected member stars in the VOD and HAC regions from the K giant sample of LAMOST DR5 and cross-matched them with results from the literature to obtain their elemental abundances. The orbital characteristics, namely, eccentricity, apocenter distance, energy, and angular momentum were compared between the member stars in the VOD and HAC regions. Then, we investigated the relationship between the VOD and HAC from the perspective of chemical evolution through a comparison of the distributions of elemental abundances in these two regions. Results. By studying the orbital parameters of the members in VOD and HAC, we find that the distribution of the orbital eccentricity, apocenter, and maximum height from the Galactic disk of the members of these two regions are very consistent. They are both on orbits of low angular momentum and high energy. Their density distributions in the spatial position are also similar based on an integration of the last 8 Gyr of their orbits. We also found that these two structures have similar distributions in [Fe/H] and other elemental abundances. Based on the similarity of the orbital properties and the consistency of the chemical abundances, we suggest that these two structures may have come from the merger of the same dwarf galaxy, such as the Gaia-Sausage-Enceladus (GSE). Also, part of the VOD may originate from Small Magellanic Cloud (SMC) debris that had been stripped 3 Gyr ago.

Minute-cadence observations of the LAMOST fields with the TMTS: II. Catalogues of short-period variable stars from the first 2-yr surveys

ABSTRACT Over the past few years, wide-field time-domain surveys such as Zwicky Transient Facility and Optical Gravitational Lensing Experiment have led to discoveries of various types of interesting short-period stellar variables, such as ultracompact eclipsing binary white dwarfs (WDs), rapidly rotating magnetized WDs, transitional cataclysmic variables between hydrogen-rich and helium accretion, and blue large-amplitude pulsators (BLAPs), which greatly enrich our understandings of stellar physics under some extreme conditions. In this paper, we report the first-2-yr discoveries of short-period variables (i.e. P &amp;lt; 2 h) by the Tsinghua University–Ma Huateng Telescopes for Survey (TMTS). TMTS is a multitube telescope system with a field of view up to 18 deg2, which started to monitor the Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST) sky areas since 2020 and generated uninterrupted minute-cadence light curves for about 10 million sources within 2 yr. Adopting the Lomb–Scargle periodogram with period-dependent thresholds for the maximum powers, we identify over 1100 sources that exhibit a variation period shorter than 2 h. Compiling the light curves with the Gaia magnitudes and colours, LAMOST spectral parameters, International Variable Star Index classifications, and archived observations from other prevailing time-domain survey missions, we identified 1076 as δ Scuti stars, which allows us to study their populations and physical properties in the short-period regime. The other 31 sources include BLAPs, subdwarf B variables, pulsating WDs, ultracompact/short-period eclipsing/ellipsoidal binaries, cataclysmic variables below the period gap, etc., which are highly interesting and worthy of follow-up investigations.

The Edge Sensor of Segmented Mirror Based on Fringes of Equal Thickness

Co-phase and co-focus detection is one of the key technologies for large-aperture segmented mirror telescopes. In this paper, a new edge sensor based on fringes of equal thickness is developed, which can detect each segment’s relative piston, tilt, and tip errors from the interferograms. Based on the co-focus demand for many ground-based seeing limited segmented mirror telescopes, an edge sensor prototype based on such a principle is built and applied in the indoor segmented mirror experiment system in the lab. According to the co-focus requirement of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, many simulations and experiments are carried out for co-focus error detection of the segmented mirror system. Experiment results show that the co-focus accuracy is better than 0.″02 rms, which can meet the co-focus requirements of most large or extremely large segmented mirror astronomical telescopes.

Discovering exoplanets in Pleiades with transiting exoplanet survey satellite

No transiting exoplanets have previously been found in the Pleiades. The Pleiades is a relatively young star cluster near us, which makes it valuable for investigation. This study aims to determine the existence of exoplanets in Pleiades using the transit method. Specifically, it sought to determine if the listed 83 stars have exoplanets by inspecting on light-curves from data of Transiting Exoplanet Survey Satellite (TESS). The TESS mission, with a better resolution and observed sky area than the previous Kepler mission, aimed to find more exoplanets around stars. To test the hypothesis that exoplanets do exist in the 83 stars of the Pleiades, we downloaded their light-curves using Jupyter notebook and the Lightkurve package, then checked using BLS method and fitting if there were transits. The results showed no clear sign of transiting planets in those stars. These results suggest that the 83 stars checked likely dont have a transiting exoplanet, but 83 stars cannot represent the whole Pleiades star cluster. Other methods should be used in analysis to gain more accurate results and more stars should be checked to investigate whether or not transiting exoplanets exist in the Pleiades star cluster.

V-SLAM ENHANCED INS/GNSS FUSION SCHEME FOR LANE LEVEL VEHICULAR NAVIGATION APPLICATIONS IN DYNAMIC ENVIRONMENT

Abstract. With the development of different sensors, such as global navigation satellite system (GNSS), inertial measurement unit (IMU), LiDAR, radar and camera, more localization information is available for autonomous vehicular applications. However, each sensor has its limitations in different circumstances. For example, visual Simultaneous Localization and Mapping (SLAM) easily loses tracking in an open sky area where accurate GNSS measurements can be obtained. Sensors can complement each other by integrated their information in a multi-sensor fusion scheme. In this study, we proposed a visual-SLAM enhanced INS/GNSS localization fusion scheme for a high dynamic environment. Oriented FAST and rotated BRIEF (ORB) SLAM are used to pre-process image sequences from monocular camera, rescaled and refreshed after applying GNSS measurements, and convert to position and velocity information, which can provide updates to the system. The performance of the fusion system was verified through two field tests at different speed ranges (about 30–60 km/s), using a reliable reference system as ground-truth to assess the accuracy of the proposed localization fusion scheme. The results indicated that the proposed system could improve the navigation accuracy compared to INS/GNSS integration scheme and achieve which-lane level or even where-in-lane level.

Image dehazing algorithm based on optimized dark channel and haze-line priors of adaptive skysegmentation.

When dealing with outdoor hazy images, traditional image dehazing algorithms are often affected by the sky regions, resulting in appearing color distortions and detail loss in the restored image. Therefore, we proposed an optimized dark channel and haze-line priors method based on adaptive sky segmentation to improve the quality of dehazed images including sky areas. The proposed algorithm segmented the sky region of a hazy image by using the Gaussian fitting curve and prior information of sky color rules to calculate the adaptive threshold. Then, an optimized dark channel prior method was used to obtain the light distribution image of the sky region, and the haze-line prior method was utilized to calculate the transmission of the foreground region. Finally, a minimization function was designed to optimize the transmission, and the dehazed images were restored with the atmospheric scattering model. Experimental results demonstrated that the presented dehazing framework could preserve more details of the sky area as well as restore the color constancy of the image with better visual effects. Compared with other algorithms, the results of the proposed algorithm could achieve higher peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM) evaluation values and provide the restored image with subjective visual effects closer to the real scene.

Detection approach for GEO space objects with a wide-field optical telescope array.

In 2020, Changchun Observatory developed a 280 mm wide-field optical telescope array to improve surveillance of space debris in the geosynchronous belt. There are many advantages including a wide field of view, the ability to observe a large area of sky and high reliability. However, the wide field of view causes a significant number of background stars to appear in the image when photographing space objects, making it difficult to detect them. This research focuses on the precise detection of GEO space objects from images taken by this telescope array in order to position them in large quantities. Our work further investigates the motion feature of an object, namely that the object can be seen as being in a uniform linear motion for a brief length of time. Based on this feature, the belt can be divided into a number of smaller areas and the telescope array scans each smaller area one at a time from east to west. To detect objects in the subarea, a combination of image differencing with trajectory association is used. The image differencing algorithm is used to remove most stars and screen out suspected objects in the image. Next, the trajectory association algorithm is employed to further filter out the real objects among the suspected ones, and the trajectories attributed to the same object are linked. The feasibility and accuracy of the approach were verified by the experiment results. The accuracy rate of trajectory association exceeds 90% and on average, more than 580 space objects can be detected per observation night. Since the J2000.0 equatorial system can accurately describe the apparent position of an object, the object can be detected by using this coordinate system as opposed to the pixel coordinate system.

A Catalog of Distance Determinations for the LAMOST DR8 K Giants in the Galactic Halo

We present a catalog of distances for 19,544 K giants drawn from Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) DR8. Most of them are located in the halo of the Milky Way up to ∼120 kpc. There are 15% K giants without Sloan Digital Sky Survey (SDSS) photometry, for which we supplements with Pan-STARRS1 (PS1) photometry calibrated to SDSS photometric system. The possible contamination of the red clumps/horizontal branch are removed according to metallicities and colors before the distance determination. Combining the LAMOST spectroscopic metallicities with the SDSS/PS1 photometry, we estimate the absolute magnitudes in the SDSS r band, the distance moduli, and the corresponding uncertainties through an Bayesian approach devised by Xue et al. for the Sloan Extension for Galactic understanding and exploration halo K giants. The typical distance precision is about 11%. The stars in the catalog lie in a region of 4–126 kpc from the Galactic center, of which with 6320 stars beyond 20 kpc and 273 stars beyond 50 kpc, forming the largest spectroscopic sample of distant tracers in the Milky Way halo so far.

Search for Extremely Metal-poor Stars with Gemini-N/Graces. I. Chemical-abundance Analysis

We present stellar parameters and abundances of 13 elements for 18 very metal-poor (VMP; [Fe/H] < –2.0) stars, selected as extremely metal-poor (EMP; [Fe/H] < –3.0) candidates from the Sloan Digital Sky Survey and Large sky Area Multi-Object Fiber Spectroscopic Telescope survey. High-resolution spectroscopic observations were performed using GEMINI-N/GRACES. We find 10 EMP stars among our candidates, and we newly identify three carbon-enhanced metal-poor stars with [Ba/Fe] < 0. Although chemical abundances of our VMP/EMP stars generally follow the overall trend of other Galactic halo stars, there are a few exceptions. One Na-rich star ([Na/Fe] = +1.14) with low [Mg/Fe] suggests a possible chemical connection with second-generation stars in a globular cluster. The progenitor of an extremely Na-poor star ([Na/Fe] = –1.02) with high K- and Ni-abundance ratios may have undergone a distinct nucleosynthesis episode, associated with core-collapse supernovae (SNe) having a high explosion energy. We have also found a Mg-rich star ([Mg/Fe] = +0.73) with slightly enhanced Na and extremely low [Ba/Fe], indicating that its origin is not associated with neutron-capture events. On the other hand, the origin of the lowest Mg abundance ([Mg/Fe] = –0.61) star could be explained by accretion from a dwarf galaxy, or formation in a gas cloud largely polluted by SNe Ia. We have also explored the progenitor masses of our EMP stars by comparing their chemical-abundance patterns with those predicted by Population III SNe models, and find a mass range of 10–26 M ⊙, suggesting that such stars were primarily responsible for the chemical enrichment of the early Milky Way.

A New Catalog of Am-type Chemically Peculiar Stars Based on LAMOST

A total of about 21,600 Am candidates were detected with the MKCLASS code based on the low-resolution spectra of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope Data Releases 8 (v1.0), 9 (v0), and 10 (v0), which greatly expands the database of Am-type stars. By crossmatching the known catalogs of Am stars and our Am candidates with the AAVSO International Variable Star Index catalog, a catalog of the largest eclipsing Am binaries was obtained, which includes 754 binaries and provides a substantial sample with which to study Am stars. Fundamental information, including atmospheric parameters of the two kinds of candidates, are collected and listed in the catalogs, such as temperature, log g, and metallicity. We further carried out statistical analysis of the types of parameters. In our new catalog, there are some Am candidates with a temperature lower than 7000 K and some eclipsing Am binary candidates with a period of less than 1 day, which poses challenges to the slow rotation of stars classified as type Am observed in previous research. These candidates are significant and provide a great opportunity to explore the real relationship between Am-type stars’ peculiarity and slow stellar rotation. The Hertzsprung–Russell diagram of Am stars and the primary stars of eclipsing Am binary candidates indicate that a majority of the Am stars and almost all primary stars of binaries are in or around the main-sequence evolution stage.

Searching for Gravitational-wave Counterparts Using the Transiting Exoplanet Survey Satellite

In 2017, the LIGO and Virgo gravitational-wave (GW) detectors, in conjunction with electromagnetic (EM) astronomers, observed the first GW multimessenger astrophysical event, the binary neutron star (BNS) merger GW170817. This marked the beginning of a new era in multimessenger astrophysics. To discover further GW multimessenger events, we explore the synergies between the Transiting Exoplanet Survey Satellite (TESS) and GW observations triggered by the LIGO–Virgo–KAGRA Collaboration (LVK) detector network. TESS's extremely wide field of view (∼2300 deg2) means that it could overlap with large swaths of GW localizations, which often span hundreds of square degrees or more. In this work, we use a recently developed transient detection pipeline to search TESS data collected during the LVK’s third observing run, O3, for any EM counterparts. We find no obvious counterparts brighter than about 17th magnitude in the TESS bandpass. Additionally, we present end-to-end simulations of BNS mergers, including their detection in GWs and simulations of light curves, to identify TESS's kilonova discovery potential for the LVK's next observing run (O4). In the most optimistic case, TESS will observe up to one GW-found BNS merger counterpart per year. However, TESS may also find up to five kilonovae that did not trigger the LVK network, emphasizing that EM-triggered GW searches may play a key role in future kilonova detections. We also discuss how TESS can help place limits on EM emission from binary black hole mergers and rapidly exclude large sky areas for poorly localized GW events.

Radio AGN selection and characterization in three Deep-Drilling Fields of the Vera C. Rubin Observatory Legacy Survey of Space and Time

ABSTRACT The Australia Telescope Large Area Survey (ATLAS) and the VLA survey in the XMM-LSS/VIDEO deep field provide deep (≈15 $\mu$ Jy beam−1) and high-resolution (≈4.5–8 arcsec) radio coverage of the three XMM-SERVS fields (W-CDF-S, ELAIS-S1, and XMM-LSS). These data cover a total sky area of 11.3 deg2 and contain ≈11 000 radio components. Furthermore, about 3 deg2 of the XMM-LSS field also has deeper MIGHTEE data that achieve a median RMS of 5.6 $\mu$ Jy beam−1 and detect more than 20 000 radio sources. We analyse all these radio data and find source counterparts at other wavebands utilizing deep optical and infrared (IR) surveys. The nature of these radio sources is studied using radio-band properties (spectral slope and morphology) and the IR–radio correlation. Radio AGNs are selected and compared with those selected using other methods (e.g. X-ray). We found 1656 new AGNs that were not selected using X-ray and/or MIR methods. We constrain the FIR-to-UV SEDs of radio AGNs using cigale and investigate the dependence of radio AGN fraction upon galaxy stellar mass and star formation rate.

Value-added Catalog of M-giant Stars in LAMOST DR9

In this work, we update the catalog of M-giant stars from the low-resolution spectra of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Data Release 9. There are 58,076 M giants identified from the classification pipeline with seven temperature subtypes from M0 to M6. The 2471 misclassified non–M-giant stars are white dwarf binaries, early types, and M dwarfs. And the contamination rate is 4.2% in the M-giants sample. A total of 372 carbon stars were identified by CaH spectral indices, and were further confirmed by the LAMOST spectra. We update the correlation between the (W1 – W2)0 color and [M/H] from APOGEE DR17. We calculate the radial velocities of all M giants by applying cross-correlation to the spectra between 8000 and 8950 Å with synthetic spectra from ATLAS9. Taking star distances less than 4 kpc from Gaia EDR3 as the standard, we refitted the photometric distance relation of M giants. And based on our M-giant stars, we select a group of Sagittarius stream members, whose sky and 3D velocity distributions are well consistent with K-giant Saggitarius stream members found in Yang et al. With our M giants, we find that the disk is asymmetric out to R = 25 kpc, which is 5 kpc further out than detected using K giants.

Spectroscopic and photometric studies on four solar-type short-period contact binaries in the triple stellar systems

ABSTRACT We reported new spectroscopy and photometry for four short-period binaries, which were acquired by several small telescopes in China from 2020 to 2022. From new spectrum and Large Sky Area Multiobject Fiber Spectroscopic Telescope data, we determined their spectral types of G8V for PZ UMa, G7 for MM Com, and V0685 Peg and G3 for V1055 Her. When compared to the Transiting Exoplanet Survey Satellite (TESS) light curve (LC) with a 2-min cadence, the difference between two light maxima for V1055 Her displays a 29.7-d oscillation. Utilizing the Wilson–Devinney program, we deduced 10 photometric solutions from our new and TESS data. Four binaries are W-type ones with variable O’Connell effects. For LC2022.1 (MM Com) and LC2022.9 (V1055 Her), Δmmax=Max.I–Max.II is as large as $15{{\ \rm per\ cent}}$ of variable light amplitude, which may be attributed to the spot’s migration and evolution. From the mass-luminosity diagram, the more massive components aref somewhat evolved main-sequence stars, whereas the less massive ones are overluminous as a result of energy exchange. Based on all eclipse timing residuals, the orbital period variations are preferably described by the light-travel time effects via the presence of additional companions. Their modulation periods range from 10 to 20 yr for four binaries, corresponding the companion’s mass ranging from M3 = 0.11 to 0.34 M⊙. Therefore, four solar-type short-period contact binaries (i.e. MM Com, PZ UMa, V0685 Peg, and V1055 Her) may be triple stellar systems.

An in-depth Exploration of LAMOST Unknown Spectra Based on Density Clustering

Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST) has completed the observation of nearly 20 million celestial objects, including a class of spectra labeled “Unknown.” Besides low signal-to-noise ratio, these spectra often show some anomalous features that do not work well with current templates. In this paper, a total of 637,889 “Unknown” spectra from LAMOST DR5 are selected, and an unsupervised-based analytical framework of “Unknown” spectra named SA-Frame (Spectra Analysis-Frame) is provided to explore their origins from different perspectives. The SA-Frame is composed of three parts: NAPC-Spec clustering, characterization and origin analysis. First, NAPC-Spec (Nonparametric density clustering algorithm for spectra) characterizes different features in the “unknown” spectrum by adjusting the influence space and divergence distance to minimize the effects of noise and high dimensionality, resulting in 13 types. Second, characteristic extraction and representation of clustering results are carried out based on spectral lines and continuum, where these 13 types are characterized as regular spectra with low S/Ns, splicing problems, suspected galactic emission signals, contamination from city light and un-gregarious type respectively. Third, a preliminary analysis of their origins is made from the characteristics of the observational targets, contamination from the sky, and the working status of the instruments. These results would be valuable for improving the overall data quality of large-scale spectral surveys.

Multiband gravitational wave observations of stellar binary black holes at the low to middle and high frequencies

ABSTRACT The ground-based gravitational wave (GW) observatories discover a population of merging stellar binary black holes (BBHs), which are promising targets for multiband observations by the low-, middle-, and high-frequency GW detectors. In this paper, we investigate the multiband GW detections of BBHs and demonstrate the advantages of such observations in improving the localization and parameter estimates of the sources. We generate mock samples of BBHs by considering different formation models as well as the merger rate density constrained by the current observations (GWTC-3). We specifically consider the astrodynamical middle-frequency interferometer GW observatory (AMIGO) in the middle-frequency band and estimate that it may detect 21–91 BBHs with signal-to-noise ratio ϱ ≥ 8 in a 4-yr observation period. The multiband observations by the low-frequency detectors [Laser Interferometer Space Antenna (LISA) and Taiji] and AMIGO may detect 5–33 BBHs with ϱLT ≥ 5 and ϱAMI ≥ 5, which can evolve to the high-frequency band within 4 yr and can be detected by the Cosmic Explorer (CE) and Einstein Telescope (ET). The joint observations of LISA-Taiji-AMIGO-ET-CE may localize the majority of the detectable BBHs in sky areas of 7 × 10−7 to 2 × 10−3 deg2, which is improved by a factor of ∼120, ∼2.4 × 105, ∼1.8 × 104, or ∼1.2 × 104, comparing with those by only adopting CE-ET, AMIGO, LISA-Taiji, or LISA-Taiji-AMIGO. These joint observations can also lead to an improvement of the measurement precision of the chirp mass (symmetric mass ratio) by a factor of ∼5.5 × 104 (33), ∼16 (8), ∼120 (90), or ∼5 (5), comparing with those by CE-ET, AMIGO, LISA-Taiji, or LISA-Taiji-AMIGO.

Properties of Flare Events on M Stars from LAMOST Spectral Survey Based on Kepler and TESS Light Curves

A catalog of M stars has been published from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope data release 7 (LAMOST DR7). We cross-matched the LAMOST M catalog with Kepler, Kepler 2 (K2) and Transiting Exoplanet Survey Satellite (TESS) surveys. We obtained the light curves from the Kepler and TESS surveys. We detected 20,047 flare events from 4053 M stars and calculated their durations, amplitudes, and energies. We analyzed the distribution of the flare durations and energies. The distributions of flare duration for Kepler, K2 and TESS peak are at 3–3.5 hr, 4–6 hr and 1–1.5 hr, respectively. This may be the result of the different cadences for the three data sets. The highest regions of the flare energies of Kepler, K2 and TESS are 32–32.5, 32–32.5 and 31–31.5 erg in Log format, respectively. A linear relationship between flare duration and energy emerges from our analysis. The ratio of flare duration to total observational time is approximately 0.2%–0.3% for the Kepler, K2 and TESS surveys. The occurrence rate of a star with a flare event increases from the M0 to M4 subtypes. We also determined the spatial distribution of the flare rate of M stars in the Milky Way. It seems that the flare rate decreases as the vertical height increases. The power index of the flare energies is in the region of 1.53–2.32, which is similar to previous result for solar type star (2.0). Further, we examined the relationship between the flare amplitude and chromospheric intensity. The flare activity increases rapidly with the increase in the Hα EW at the lower values (less approximately 2 Å) and it increases slowly at the higher values.