Red Supergiant Research Articles

A New Approach to Identifying Red Supergiant Stars in Metal-poor Galaxies: A Case Study of NGC 6822

Abstract A complete sample of red supergiant (RSG) stars is important for studying their properties. Identifying RSGs in extragalactic fields first requires removing the Galactic foreground dwarfs. The color–color diagram (CCD) method, specifically using r − z/z − H and J − H/H − K, has proven successful in several studies. However, in metal-poor galaxies, faint RSGs will mix into the dwarf branch in the CCD and would be removed, leading to an incomplete RSG sample. This work attempts to improve the CCD method in combination with the Gaia astrometric measurement to remove foreground contamination in order to construct a complete RSG sample in metal-poor galaxies. The empirical regions of RSGs in both CCDs are defined and modified by fitting the locations of RSGs in galaxies with a range of metallicity. The metal-poor galaxy NGC 6822 is taken as a case study for its low metallicity ([Fe/H] ≈ −1.0) and moderate distance (about 500 kpc). In the complete sample, we identify 1184 RSG, 1559 oxygen-rich AGB (O-AGBs), 1075 carbon-rich AGB (C-AGBs), and 140 extreme AGB (x-AGBs) candidates, with a contamination rate of approximately 20.5%, 9.7%, 6.8%, and 5.0%, respectively. We also present a pure sample, containing only the sources away from the dwarf branch, which includes 843 RSG, 1519 O-AGB, 1059 C-AGB, and 140 x-AGB candidates, with a contamination rate of approximately 6.5%, 8.8%, 6.1%, and 5.0%, respectively. About 600 and 450 RSG candidates are newly identified in the complete and pure samples, respectively, compared to the previous RSG sample in NGC 6822.

The Observed Phase Space of Mass-loss History from Massive Stars Based on Radio Observations of a Large Supernova Sample

Abstract In this work, we study the circumstellar material (CSM) around massive stars, and the mass-loss rates depositing this CSM, using a large sample of radio observations of 325 core-collapse supernovae (CCSNe; only ~22% of them being detected). This sample comprises both archival data and our new observations of 99 CCSNe conducted with the AMI-LA radio array in a systematic approach devised to constrain the mass loss at different stages of stellar evolution. In the supernova (SN)–CSM interaction model, observing the peak of the radio emission of an SN provides the CSM density at a given radius (and therefore the mass-loss rate that deposited this CSM). On the other hand, limits on the radio emission, and/or on the peak of the radio emission provide a region in the CSM phase space that can be ruled out. Our analysis shows a discrepancy between the values of mass-loss rates derived from radio-detected and radio-nondetected SNe. Furthermore, we rule out mass-loss rates in the range of 2 × 10−6–10−4 M ⊙ yr−1 for different epochs during the last 1000 yr before the explosion (assuming wind velocity of 10 km s−1) for the progenitors of ~80% of the Type II supernovae (SNe II) in our sample. In addition, we rule out the ranges of mass-loss rates suggested for red supergiants for ~50% of the progenitors of SNe II in our sample. We emphasize here that these results take a step forward in constraining mass loss in winds from a statistical point of view.

The Red Supergiant Progenitor Luminosity Problem

Analysis of pre-explosion imaging has confirmed red supergiants (RSGs) as the progenitors to Type II-P supernovae (SNe). However, extracting an RSG's luminosity requires assumptions regarding the star’s temperature or spectral type and the corresponding bolometric correction, circumstellar extinction, and possible variability. The robustness of these assumptions is difficult to test since we cannot go back in time and obtain additional pre-explosion imaging. Here, we perform a simple test using the RSGs in M31, which have been well observed from optical to mid-IR. We ask the following: By treating each star as if we only had single-band photometry and making assumptions typically used in SN progenitor studies, what bolometric luminosity would we infer for each star? How close is this to the bolometric luminosity for that same star inferred from the full optical-to-IR spectral energy distribution (SED)? We find common assumptions adopted in progenitor studies systematically underestimate the bolometric luminosity by a factor of 2, typically leading to inferred progenitor masses that are systematically too low. Additionally, we find a much larger spread in luminosity derived from single-filter photometry compared to SED-derived luminosities, indicating uncertainties in progenitor luminosities are also underestimated. When these corrections and larger uncertainties are included in the analysis, even the most luminous known RSGs are not ruled out at the 3σ level, indicating there is currently no statistically significant evidence that the most luminous RSGs are missing from the observed sample of II-P progenitors. The proposed correction also alleviates the problem of having progenitors with masses below the expected lower-mass bound for core collapse.

Searching for Galactic red supergiants with Gaia RVS spectra

Searching for Galactic red supergiants with Gaia RVS spectra

Probing red supergiant atmospheres and winds with early-time, high-cadence, high-resolution type II supernova spectra

High-cadence high-resolution spectroscopic observations of infant Type II supernovae (SNe) represent an exquisite probe of the atmospheres and winds of exploding red-supergiant (RSG) stars. Using radiation hydrodynamics and radiative transfer calculations, we studied the gas and radiation properties during and after the phase of shock breakout, considering RSG star progenitors enshrouded within a circumstellar material (CSM) that varies in terms of the extent, density, and velocity profile. In all cases, the original, unadulterated CSM structure is probed only at the onset of shock breakout, seen in high-resolution spectra as narrow, often blueshifted emission components, possibly with an additional absorption trough. As the SN luminosity rises during breakout, radiative acceleration of the unshocked CSM starts, leading to a broadening of the ``narrow'' lines by several 100 (up to several 1000) depending on the CSM properties. This acceleration is at its maximum close to the shock, where the radiative flux is greater and thus typically masked by optical-depth effects. Generally, the narrow-line broadening is greater for more compact, tenuous CSM because of the proximity to the shock where the flux is born; it is smaller in the denser and more extended CSM. Narrow-line emission should show a broadening that slowly increases first (the line forms further out in the original wind), then sharply rises (the line forms in a region that is radiatively accelerated), before decreasing until late times (the line forms further away in regions more weakly accelerated). Radiative acceleration is expected to inhibit X-ray emission during the early (IIn) phase. Although high spectral resolution is critical at the earliest times to probe the original slow wind, the radiative acceleration and the associated line broadening may be captured with medium resolution. This would allow for a simultaneous view of narrow, Doppler-broadened line emission, as well as extended, electron-scattering broadened emission.

Transients by Black Hole Formation from Red Supergiants: Impact of Dense Circumstellar Matter

Abstract Failed supernovae (SNe), which are likely the main channel for forming stellar-mass black holes, are predicted to accompany mass ejections much weaker than typical core-collapse SNe. We conduct a grid of one-dimensional radiation hydrodynamical simulations to explore the emission of failed SNe from red supergiant progenitors, leveraging recent understanding of the weak explosion and the dense circumstellar matter (CSM) surrounding these stars. We find from these simulations and semianalytical modeling that diffusion in the CSM prolongs the early emission powered by shock breakout/cooling. The early emission has peak luminosities of ~107–108 L ⊙ in optical and UV and durations of days to weeks. The presence of dense CSM aids in the detection of the early bright peak from these events via near-future wide-field surveys such as Rubin Observatory, ULTRASAT, and UVEX.

MAGIS (Measuring Abundances of red super Giants with Infrared Spectroscopy) project

Context. Given their high luminosities (L ≳ 104 L⊙), red supergiants (RSGs) are good tracers of the chemical abundances of the young stellar population in the Milky Way and nearby galaxies. However, previous abundance analyses tailored to RSGs suffer some systematic uncertainties originating in, most notably, the synthesized molecular spectral lines for RSGs. Aims. We establish a new abundance analysis procedure for RSGs that circumvents difficulties faced in previous works, and test the procedure with ten nearby RSGs observed with the near-infrared high-resolution spectrograph WINERED (0.97−1.32 µm, R = 28 000). The wavelength range covered here is advantageous in that the molecular lines contaminating atomic lines of interest are mostly weak. Methods. We first determined the effective temperatures (Teff) of the targets with the line-depth ratio (LDR) method, and calculated the surface gravities (log 𝑔) according to the Stefan-Boltzmann law. We then determined the microturbulent velocities (vmicro) and metallicities ([Fe/H]) simultaneously through the fitting of individual Fe I lines. Finally, we also determined the abundance ratios ([X/Fe] for element X) through the fitting of individual lines. Results. We determined the [X/Fe] of ten elements (Na I, Mg I, Al I, Si I, K I, Ca I, Ti I, Cr I, Ni I, and Y II). We estimated the relative precision in the derived abundances to be 0.04−0.12 dex for elements with more than two lines analyzed (e.g., Fe I and Mg I) and up to 0.18dex for the other elements (e.g., Y II). We compared the resultant abundances of RSGs with the well-established abundances of another type of young star, namely the Cepheids, in order to evaluate the potential systematic bias in our abundance measurements, assuming that the young stars (i.e., both RSGs and Cepheids) in the solar neighborhood have common chemical abundances. We find that the determined RSG abundances are highly consistent with those of Cepheids within <0.1 dex for some elements (notably [Fe/H] and [Mg/Fe]), which means the bias in the abundance determination for these elements is likely to be small. In contrast, the consistency is worse for some other elements (e.g., [Si/Fe] and [Y/Fe]). Nevertheless, the dispersion of the chemical abundances among our target RSGs is comparable with the individual statistical errors on the abundances. Hence, the procedure is likely to be useful to evaluate the relative difference in chemical abundances among RSGs.

Machine Learning Classification of Young Stellar Objects and Evolved Stars in the Magellanic Clouds Using the Probabilistic Random Forest Classifier

The Magellanic Clouds (MCs) are excellent locations to study stellar dust emission and its contribution to galaxy evolution. Through spectral and photometric classification, MCs can serve as a unique environment for studying stellar evolution and galaxies enriched by dusty stellar point sources. We applied machine learning classifiers to spectroscopically labeled data from the Surveying the Agents of Galaxy Evolution (SAGE) project, which involved 12 multiwavelength filters and 618 stellar objects at the MCs. We classified stars into five categories: young stellar objects (YSOs), carbon-rich asymptotic giant branch (CAGB) stars, oxygen-rich AGB (OAGB) stars, red supergiants (RSG), and post-AGB (PAGB) stars. Following this, we augmented the distribution of imbalanced classes using the Synthetic Minority Oversampling Technique (SMOTE). Therefore, the Probabilistic Random Forest (PRF) classifier achieved the highest overall accuracy, reaching 89% based on the recall metric, in categorizing dusty stellar sources before and after data augmentation. In this study, SMOTE did not impact the classification accuracy for the CAGB, PAGB, and RSG categories but led to changes in the performance of the OAGB and YSO classes.

Diversity in Hydrogen-rich Envelope Mass of Type II Supernovae. I. Plateau Phase Light-curve Modeling

Abstract We present a systematic study of Type II supernovae (SNe II) originating from progenitors with effective temperatures (T eff) and luminosities closely resembling red supergiants (RSGs) observed in pre-supernova (SN) images and in the Galaxy. Using Modules for Experiments in Stellar Astrophysics, we compute a large grid of massive stars with T eff ranging from 3200 to 3800 K at their RSG phases, with hydrogen envelopes artificially stripped to varying extents (3–10 M ⊙). The light curves of SNe IIP resulting from the explosions of these Galactic-RSG–like progenitors are modeled using STELLA. Our survey of the light curves reveals that partial stripping of the hydrogen envelope creates diversity in the magnitude and duration of SNe IIP light curves, without affecting the position of the RSG progenitor on the Hertzsprung–Russell diagram. For these Galactic-RSG-like progenitor models, we establish an indicator based on the light-curve properties to estimate the hydrogen envelope mass. Additionally, we discuss the effects of material mixing and 56Ni heating. Applying our model grid to a large sample of approximately 100 observed SNe IIP reveals a considerably broader range of hydrogen-rich envelope masses than predicted by standard stellar wind models. This finding suggests that if SNe IIP are explosions of Galactic-like RSGs to explain the diversity in the observed light curves, a significant fraction of them must have experienced substantial mass loss beyond the standard mass-loss prescription prior to their explosions. This finding highlights the uncertainties involved in massive star evolution and the pre-SN mass-loss mechanism.

Radial Velocity and Astrometric Evidence for a Close Companion to Betelgeuse

Abstract We examine a century of radial velocity, visual magnitude, and astrometric observations of the nearest red supergiant, Betelgeuse, in order to reexamine the century-old assertion that Betelgeuse might be a spectroscopic binary. These data reveal Betelgeuse varying stochastically over years and decades due to its boiling, convective envelope, periodically with a 5.78 yr long secondary period (LSP), and quasiperiodically from pulsations with periods of several hundred days. We show that the LSP is consistent between astrometric and radial velocity data sets, and argue that it indicates a low-mass companion to Betelgeuse, less than a solar mass, orbiting in a 2110 day period at a separation of just over twice Betelgeuse’s radius. The companion star would be nearly 20 times less massive and a million times fainter than Betelgeuse, with similar effective temperature, effectively hiding it in plain sight near one of the best-studied stars in the night sky. The astrometric data favor an edge-on binary with orbital plane aligned with Betelgeuse’s measured spin axis. Tidal spin–orbit interaction drains angular momentum from the orbit and spins up Betelgeuse, explaining the spin–orbit alignment and Betelgeuse’s anomalously rapid spin. In the future, the orbit will decay until the companion is swallowed by Betelgeuse in the next 10,000 yr.

Cosmic ray contributions from rapidly rotating stellar mass black holes: cosmic Ray GeV to EeV proton and anti-proton sources

In Radio Super Novae (RSNe) a magnetic field of (B × r) = 1016.0±0.12 Gauss × cm is observed; these are the same numbers for Blue Super Giant (BSG) star explosions as for Red Super Giant (RSG) star explosions, despite their very different wind properties. The EHT data for M87 as well for low power radio galaxies all show consistency with just this value of the quantity (B × r), key for angular momentum and energy transport, and can be derived from the radio jet data. We interpret this as a property of the near surroundings of a black hole (BH) at near maximal rotation, independent of BH mass. In the commonly used green onion model, in which a 2 π flow changes over to a jet flow we interpret this as a wind emanating from the BH/accretion disk system and its surroundings. Near the BH collisions in the wind can produce a large fraction of anti-protons. In this scenario the cosmic Ray (CR) population from the wind/jet is proposed to be visible as EeV protons and anti-protons in the CR data to EeV energy, with a E−7/3 spectrum. This can be connected to a concept of inner and outer Penrose zones in the ergo-region. The observed numbers for the magnetic field imply the Planck time as the governing time scale: A BH rotating near maximum can accept a proton per log bin of energy in an extended spectrum with the associated pions every Planck time.

Constraining the Progenitor of the Nearby Type II-P SN 2024ggi with Environmental Analysis

Abstract The progenitors of Type II-P supernovae (SN) have been confirmed to be red supergiants. However, the upper mass limit of the directly probed progenitors is much lower than that predicted by current theories, and the accurate determination of the progenitor masses is key to understand the final fate of massive stars. Located at a distance of only 6.72 Mpc, the Type II-P SN 2024ggi is one of the closest SNe in the last decade. Previous studies have analyzed its progenitor by direct detection, but the derived progenitor mass may be influenced by the very uncertain circumstellar extinction and pulsational brightness variability. In this work, we try to constrain the progenitor mass with an environmental analysis based on images from the Hubble Space Telescope. We found that stars in the progenitor environment have a uniform spatial distribution without significant clumpiness, and we derived the star formation history of the environment with a hierarchical Bayesian method. The progenitor is associated with the youngest population in the SN environment with an age of log(t/yr) = 7.41 (i.e., 25.7 Myr), which corresponds to an initial mass of 10 . 2 − 0.09 + 0.06 M ⊙. Our work provides an independent measurement of the progenitor mass, which is not affected by circumstellar extinction and pulsational brightness variability.

Close-up of an extragalactic red supergiant

Close-up of an extragalactic red supergiant

Population synthesis of Thorne-Żytkow objects. Rejuvenated donors and unexplored progenitors in the common envelope formation channel

Common envelope evolution of a massive star and a neutron star companion has two possible outcomes: the formation of a short-period binary (a potential gravitational wave source progenitor) or the merger of the massive star with the neutron star. If the binary merges, a structure may form, comprised of a neutron star core surrounded by a large diffuse envelope, known as a Thorne-\.Zytkow object (T\.ZO). The predicted appearance of this hypothetical class of star is very similar to that of a red supergiant, making it difficult to identify them in observations. Our objective is to understand the properties of systems that are potential T\.ZO progenitors; specifically, binary systems that enter a common envelope phase with a neutron star companion. We also aim to distinguish those that have been through a previous stable mass transfer phase, which can rejuvenate the accretor. We used the rapid population synthesis code COMPAS at solar metallicity, with the common envelope efficiency parameter set to unity to determine the population demographics of T\.ZOs. We used one-dimensional (1D) evolutionary T\.ZO models from the literature to determine a fit for the T\.ZO lifetime to estimate the current number of T\.ZOs in the Milky Way, as well as to assess core disruption during the merger. We explored the progenitors in the Hertzsprung-Russell diagram, calculated the formation rates, and investigated the kinematics of the progenitor stars. We find that the vast majority (approx percent ) of T\.ZO progenitors in our population have experienced mass transfer and are rejuvenated prior to their formation event. For the Milky Way, we estimate a T\.ZO formation rate of 4e-4 yr^ which results in T\.ZOs at present.

Shock cooling emission from explosions of massive stars – III. Blue supergiants

ABSTRACT Light emission in the first hours and days following core-collapse supernovae is dominated by the escape of photons from the expanding shock-heated envelope. In preceding papers, we provided a simple analytic description of the time-dependent luminosity, L, and colour temperature, $T_{\rm col}$, as well as of the small (${\simeq} 10 {{\, \rm per\, cent}}$) deviations of the spectrum from a blackbody at low frequencies, $h\nu \lt 3T_{\rm col}$, and of ‘line dampening’ at $h\nu \gt 3T_{\rm col}$, for explosions of red supergiants (RSGs) with convective polytropic envelopes (without significant circumstellar medium). Here, we extend our work to provide similar analytic formulae for explosions of blue supergiants with radiative polytropic envelopes. The analytic formulae are calibrated against a large set of spherically symmetric multigroup (frequency-dependent) calculations for a wide range of progenitor parameters (mass, radius, and core/envelope mass ratios) and explosion energies. In these calculations, we use the opacity tables we constructed (and made publicly available), which include the contributions of bound–bound and bound–free transitions. The analytic formulae reproduce the numeric L and $T_{\rm col}$ to within 10 and 5 per cent accuracy, and the spectral energy distribution to within ${\sim} 20\!-\!40 {{\, \rm per\, cent}}$. The accuracy is similar to that achieved for RSG explosions.

Visual Orbits of Wolf–Rayet Stars. II. The Orbit of the Nitrogen-rich Wolf–Rayet Binary WR 138 Measured with the CHARA Array

Classical Wolf–Rayet (WR) stars are descendants of massive OB-type stars that have lost their hydrogen-rich envelopes and are in the final stages of stellar evolution, possibly exploding as Type Ib/c supernovae. It is understood that the mechanisms driving this mass loss are either strong stellar winds and or binary interactions, so intense studies of these binaries including their evolution can tell us about the importance of the two pathways in WR formation. WR 138 (HD 193077) has a period of just over 4 yr and was previously reported to be resolved through interferometry. We report on new interferometric data combined with spectroscopic radial velocities in order to provide a three-dimensional orbit of the system. The precision on our parameters tend to be about an order of magnitude better than previous spectroscopic techniques. These measurements provide masses of the stars, namely, M WR = 13.93 ± 1.49 M ⊙ and M O = 26.28 ± 1.71 M ⊙. The derived orbital parallax agrees with the parallax from Gaia, namely, with a distance of 2.13 kpc. We compare the system’s orbit to models from BPASS, showing that the system likely may have been formed with little interaction but could have formed through some binary interactions either following or at the start of a red supergiant phase but with the most likely scenario occurring as the red supergiant phase starts for a ∼40 M ⊙ star.

Dimming events of evolved stars due to clouds of molecular gas

Context. The dramatic dimming episode of the red supergiant Betelgeuse in 2019 and 2020, caused by a partial darkening of the stellar disk, has highlighted gaps in the understanding of the evolution of massive stars. Aims. We analyzed numerical models to investigate the processes behind the formation of dark surface patches and the associated reduction in the disk-integrated stellar light. Methods. With the CO5BOLD code, we performed global 3D radiation-hydrodynamical simulations of evolved stars, including convection in the stellar interior, self-excited pulsations, and the resulting atmospheric dynamics with strong radiative shocks. Results. We attribute dimming phenomena to obscuring clouds of cool gas in the lower atmosphere, forming according to three different scenarios. One process transports material outward in a strong shock, similar to what occurs in 1D simulations of radially pulsating asymptotic giant branch (AGB) stars. However, in 3D models, deviations from spherical symmetry of the shock front can lead to further local density enhancements. Another mechanism is triggered by a large convective upflow structure, in combination with exceptionally strong radial pulsations. This induces Rayleigh-Taylor instabilities, causing plumes of material to be sent outward into the atmosphere. The third and rarest scenario involves large-amplitude convective fluctuations, leading to enhanced flows in deep downdrafts, which rebound and send material outward. In all cases, the dense gas above the stellar surface cools and darkens rapidly in visible light. AGB stars show localized dark patches regularly during intermediate phases of their large-amplitude pulsations, while more massive stars will only intermittently form such patches during luminosity minima. Conclusions. The episodic levitation of dense gas clumps above the stellar surface, followed by the formation of complex molecules in the cooling gas and possibly dust grains at a later stage, can account for the dark patches and strong dimming events of supergiant stars such as Betelgeuse.

Material mixing in pulsar wind nebulae of massive runaway stars

Abstract In this study we quantitatively examine the manner pulsar wind, supernova ejecta and defunct stellar wind materials distribute and melt together into plerions. We performed 2.5D MHD simulations of the entire evolution of their stellar surroundings and different scenarios are explored, whether the star dies as a red supergiant and Wolf-Rayet supernova progenitors, and whether it moved with velocity $20\, \rm km\, \rm s^{-1}$ or $40\, \rm km\, \rm s^{-1}$ through the ISM. Within the post-explosion, early $10\, \rm kyr$, the H-burning-products rich red supergiant wind only mixes by $\le 20~{{\%}}$, due to its dense circumstellar medium filling the progenitor’s bow shock trail, still unaffected by the supernova blastwave. Wolf-Rayet materials, enhanced in C, N, O elements, distribute circularly for the $35\, \rm M_\odot$ star moving at $20\, \rm km\, \rm s^{-1}$ and oblongly at higher velocities, mixing efficiently up to 80%. Supernova ejecta, filled with Mg, Si, Ca, Ti and Fe, remain spherical for longer times at $20\, \rm km\, \rm s^{-1}$ but form complex patterns at higher progenitor speeds due to earlier interaction with the bow shock, in which they mix more efficiently. The pulsar wind mixing is more efficient for Wolf-Rayet (25%) than red supergiant progenitors (20%). This work reveals that the past evolution of massive stars and their circumstellar environments critically shapes the internal distribution of chemical elements on plerionic supernova remnants, and, therefore, governs the origin of the various emission mechanisms at work therein. This is essential for interpreting multi-frequency observations of atomic and molecular spectral lines, such as in optical, infrared, and soft X-rays.

Mass-loss Rate of Highly Evolved Stars in the Magellanic Clouds

Asymptotic giant branch stars (AGBs) and red supergiant stars (RSGs) exhibit significant mass-loss phenomena and are considered important sources of interstellar dust. In this work, we employed a uniform method of spectral energy distribution fitting to analyze a large, and hence statistically significant, sample of approximately 40,000 RSGs and AGBs in the Magellanic Clouds (MCs), providing a new catalog of evolved stars that includes stellar parameters and dust properties. Our results reveal that the total dust-production rate (DPR) of the Large Magellanic Cloud is approximately 9.69 × 10−6 M ☉ yr−1, while it is around 1.75 × 10−6 M ☉ yr−1 for the Small Magellanic Cloud, with a few stars significantly contributing to the total DPR. No significant differences were observed in the contributions to DPR from carbon-rich and oxygen-rich (O-rich) evolved stars in the MCs. We explored the relations between stellar parameters (luminosity, infrared color, period, amplitude) and mass-loss rate (MLR) for evolved stars. A prominent turning point at log(L/L☉)≈4.4 appears in the luminosity–MLR diagram of RSGs, potentially related to their mass-loss mechanism. The luminosity–MLR relation of AGBs is highly scattered. The DPR of AGBs shows a clear change with pulsation period and amplitude, with DPR exhibiting a drastic increase at pulsation periods of approximately 300 days and I-band amplitudes greater than 0.5 mag. Metallicity has some impact on the DPR of O-rich stars, with lower metallicity seeming to result in lower mean DPR and a higher proportion of optically thin stars.

The LAMOST Spectroscopic Survey of Supergiants in M31 and M33

Abstract We present systematic identifications of supergiants of M31/M33 based on massive LAMOST spectroscopic survey. Radial velocities of nearly 5000 photometrically selected M31/M33 supergiant candidates have been properly derived from the qualified spectra released in LAMOST DR10. By comparing their radial velocities with those predicted from the rotation curves of M31, as well as utilizing {\it Gaia} astrometric measurements to exclude foreground contaminations, 199 supergiant members in M31, including 168 `Rank1' and 31 `Rank2', have been successfully identified. This sample contains 62 blue supergiants (BSGs, all `Rank1'), 134 yellow supergiants (YSGs, 103 `Rank1' and 31 `Rank2') and 3 red supergiants (RSGs, all `Rank1'). For M33, we identify 84 supergiant members (56 `Rank1' and 28 `Rank2'), which includes 28 BSGs (all `Rank1'), 53 YSGs (25 `Rank1' and 28 `Rank2') and 3 RSGs (all `Rank1'). So far, this is one of the largest supergiant sample of M31/M33 with full optical wavelength coverage (3700 \textless $\lambda$ \textless 9100 \AA). This sample is valuable for understanding the star formation and stellar evolution under different environments.