Yellow supergiants (YSGs) are rare and poorly understood, and studying them is critical to constraining massive star evolution. We obtained flux-calibrated Magellan Inamori Kyocera Echelle (MIKE) high-resolution spectra of 40 YSGs in the Large Magellanic Cloud (LMC); this sample likely contains post-red supergiants (RSGs). Fitting these data with ATLAS9 model atmospheres, we determined fundamental parameters for these stars. We measure the first spectroscopic luminosities for YSGs above 20 $M_\odot$, providing us a novel probe of the luminosity-to-mass ratio. Many stars in our sample appear to have anomalously high surface gravities, despite being confirmed LMC supergiants. We manually inspected our data finding evidence for binary companions and ongoing mass loss. Our work demonstrates the valuable role of high-resolution spectroscopy in interpreting the evolutionary status of cool supergiants.
We present UVIT/Astrosat UV photometry of the RSG population of the Small Cloud galaxy (SMC). As RSGs are extremely faint in the far-UV, these observations directly probe potential companion stars. From a sample of 861 SMC RSGs, we find 88 have detections at far-UV wavelengths: a clear signature of binarity. Stellar parameters are determined for both components, which allows us to study - for the first time - the mass-ratio (q) distribution of RSG binary systems. We find a flat mass-ratio distribution best describes the observations up to M{RSG}~15 Msun. We account for our main observing bias …
We report the serendipitous observations of 571 luminous supergiants in the Magellanic Clouds by the spectroscopic GALAH and TESS-HERMES surveys: 434 stars in the Large Magellanic Cloud and 137 in the Small Magellanic Cloud. We also find one star that appears associated with structured star formation in the Magellanic Bridge. Both of these surveys are aimed at the local volume of the Galaxy but have simple, magnitude-limited selection functions that mean they include some observations of luminous extra-Galactic stars. The surveys determine stellar parameter and abundances using The Cannon, a d…
B[e] supergiants are evolved massive stars with a complex circumstellar environment. A number of important emission features probe the structure and the kinematics of the circumstellar material. In our survey of Magellanic Cloud B[e] supergiants we focus on the [OI] and [CaII] emission lines, which we identified in four more objects.
Excitation of radial pulsations in red supergiants of Magellanic Clouds is investigated using the stellar evolution calculations and the self-consistent solution of the equations of radiation hydrodynamics and turbulent convection. The stars with initial masses 6M_odot<=M_zams<=28 M_odot and the initial chemical composition X=0.7, 0.004<=Z<=0.008 are shown to be unstable against fundamental mode oscillations with periods from 17 to 1200 days as they become helium burning red supergiants. The period-luminosity relation slightly depends on the mass loss rate varying with a factor of three, where…
There is evidence that some red supergiants (RSGs) experience short lived phases of extreme mass loss, producing copious amounts of dust. These episodic outburst phases help to strip the hydrogen envelope of evolved massive stars, drastically affecting their evolution. However, to date, the observational data of episodic mass loss is limited. This paper aims to derive surface properties of a spectroscopic sample of fourteen dusty sources in the Magellanic Clouds using the Baade telescope. These properties may be used for future spectral energy distribution fitting studies to measure the mass l…
We present a self-consistent study of cool supergiants (CSGs) belonging to the Magellanic clouds. We calculated stellar atmospheric parameters using LTE KURUCZ and MARCS atmospheric models for more than 400 individual targets by fitting a careful selection of weak metallic lines. We explore the existence of a T eff scale and its implications in two different metallicity environments (each Magellanic cloud). Critical and in-depth tests have been performed to assess the reliability of our stellar parameters (i.e. internal error budget, NLTE systematics). In addition, several Montercarlo tests ha…
The characterisation of the multiplicity of high-mass stars is of fundamental importance to understand their evolution, the diversity of observed core-collapse supernovae and the formation of gravitational wave progenitor systems. Despite that, until recently, one of the final phases of massive star evolution -- the cool supergiant phase -- has received comparatively little attention. In this study we aim to explore the multiplicity among the cool supergiants (CSGs) in the Large and Small Magellanic Clouds (LMC and SMC, respectively). To do this we compile extensive archival radial velocity (R…
We present the discovery of three new B[e] supergiants (sgB[e] stars) in the Small Magellanic Cloud (SMC). All three stars (R15, R38, and R48) were identified in the course of our Runaways and Isolated O Type Star Spectroscopic Survey of the SMC (RIOTS4). The stars show optical spectra that closely resemble those of previously known B[e] stars, presenting numerous low-ionization forbidden and permitted emission lines such as [Fe II] and Fe II. Furthermore, our stars have luminosities of log(L/L_sun) > 4, demonstrating that they are supergiants. However, we find lower infrared excesses and weak…
Due to their transitionary nature, yellow supergiants provide a critical challenge for evolutionary modeling. Previous studies within M31 and the SMC show that the Geneva evolutionary models do a poor job at predicting the lifetimes of these short-lived stars. Here we extend this study to the LMC while also investigating the galaxy's red supergiant content. This task is complicated by contamination by Galactic foreground stars that color and magnitude criteria alone cannot weed out. Therefore, we use proper motions and the LMC's large systemic radial velocity (\sim278 km/s) to separate out the…
Red supergiant stars in binary systems II. Confirmation of B-type companions of red supergiants in the Small Magellanic Cloud using Hubble ultra-violet spectroscopy
The empirical upper luminosity boundary $L_{\rm max}$ of cool supergiants, often referred to as the Humphreys-Davidson limit, is thought to encode information on the general mass-loss behaviour of massive stars. Further, it delineates the boundary at which single stars will end their lives stripped of their hydrogen-rich envelope, which in turn is a key factor in the relative rates of Type-II to Type-Ibc supernovae from single star channels. In this paper we have revisited the issue of $L_{\rm max}$ by studying the luminosity distributions of cool supergiants (SGs) in the Large and Small Magel…
Using the PACS and SPIRE spectrometers on-board the Herschel Space Observatory, we obtained spectra of two red supergiants (RSGs) in the Large Magellanic Cloud (LMC). Multiple rotational CO emission lines (J=6-5 to 15-14) and 15 H2O lines were detected from IRAS 05280-6910, and one CO line was detected from WOH G64. This is the first time CO rotational lines have been detected from evolved stars in the LMC. Their CO line intensities are as strong as those of the Galactic RSG, VY CMa. Modelling the CO lines and the spectral energy distribution results in an estimated mass-loss rate for IRAS 052…
Red Supergiants (RSGs) are cool (~4000K), highly luminous stars (L - 10^5 Lsun), and are among the brightest near-infrared (NIR) sources in star-forming galaxies. This makes them powerful probes of the properties of their host galaxies, such as kinematics and chemical abundances. We have developed a technique whereby metallicities of RSGs may be extracted from a narrow spectral window around 1μm from only moderate resolution data. The method is therefore extremely efficient, allowing stars at large distances to be studied, and so has tremendous potential for extragalactic abundance work. Here,…
The binary fraction of unevolved massive stars is thought to be 70-100% but there are few observational constraints on the binary fraction of the evolved version of a subset of these stars, the red supergiants (RSGs). Here we identify a complete sample of RSGs in the Large Magellanic Cloud (LMC) using new spectroscopic observations and archival UV, IR and broadband optical photometry. We find 4090 RSGs with log L/Lo > 3.5 with 1820 of them having log L/Lo > 4, which we believe is our completeness limit. We additionally spectroscopically confirmed 38 new RSG+B star binaries in the LMC, bringing…
We search for runaway stars in the Large Magellanic Cloud (LMC) by computing the space velocities of the visually brightest stars in the LMC that are included in the Gaia TGAS proper motion catalog. We compare with predictions from stellar dynamical models to obtain (peculiar) velocities relative to their local stellar environment. Two of the 31 stars have unusually high proper motions. Of the remaining 29 stars we find that most objects in this sample have velocities in very good agreement with model predictions of a circularly rotating disk model. Indeed the excellent fit to the model implie…
In this study, we conduct a pilot program aimed at the red supergiant population of the Magellanic Clouds. We intend to extend the current known sample to the unexplored low end of the brightness distribution of these stars, building a more representative dataset with which to extrapolate their behaviour to other Galactic and extra-galactic environments. We select candidates using only near infrared photometry, and with medium resolution multi-object spectroscopy, we perform spectral classification and derive their line-of-sight velocities, confirming the nature of the candidates and their mem…
The yellow supergiant content of nearby galaxies provides a critical test of massive star evolutionary theory. While these stars are the brightest in a galaxy, they are difficult to identify because a large number of foreground Milky Way stars have similar colors and magnitudes. We previously conducted a census of yellow supergiants within M31 and found that the evolutionary tracks predict a yellow supergiant duration an order of magnitude longer than we observed. Here we turn our attention to the SMC, where the metallicity is 10x lower than that of M31, which is important as metallicity stron…
We aim to identify and characterise binary systems containing red supergiant (RSG) stars in the Small Magellanic Cloud (SMC) using a newly available ultraviolet (UV) point source catalogue obtained using the Ultraviolet Imaging Telescope (UVIT) on board AstroSat. We select a sample of 560 SMC RSGs based on photometric and spectroscopic observations at optical wavelengths and cross-match this with the far-UV point source catalogue using the UVIT F172M filter, finding 88 matches down to m$_{F172M}$=20.3 ABmag, which we interpret as hot companions to the RSGs. Stellar parameters (luminosities, ef…
We present multiwavelength broadband photometry and V, I time resolved photometry for two variable bright stars in the SMC, OGLE004336.91-732637.7 (SMC-SC3) and OGLE004633.76-731204.3 (SMC-SC4). The light curves span 12 years and show long-term periodicities (SMC-SC3) and modulated eclipses (SMC-SC4) that are discussed in terms of wide-orbit intermediate mass interacting binaries and associated envelopes. SMC-SC3 shows a primary period of 238.1 days along with a complicated waveform suggesting ellipsoidal variablity influenced by an eccentric orbit. This star also shows a secondary variability…
We present an atlas composed of more than 1500 spectra of late-type stars (spectral types from G to M) observed simultaneously in the optical and calcium triplet spectral ranges. These spectra were obtained as part of a survey to search for cool supergiants in the Magellanic Clouds and were taken over four epochs. We provide the spectral and luminosity classification for each spectrum (71% are supergiants, 13% are giants or luminous giants, 4% are carbon or S stars, and the remaining 12% are foreground stars of lesser luminosities). We also provide a detailed guide for the spectral classificat…
X-Shooting ULLYSES: Massive stars at low metallicity XIV. Properties of SMC late-O and B supergiants reveal the metallicity dependence of winds in the Magellanic Clouds
University of Sheffield（谢菲尔德大学）；KU Leuven（荷语鲁汶大学）；Armagh Observatory and Planetarium（阿马赫天文台和天文馆）；Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut（海德堡大学天文学中心，天文计算研究所）
The temperatures of red supergiants (RSGs) are expected to depend on metallicity (Z) in such a way that lower-Z RSGs are warmer. In this work, we investigate the Z-dependence of the Hayashi limit by analysing RSGs in the low-Z galaxy Wolf-Lundmark-Mellote (WLM), and compare with the RSGs in the higher-Z environments of the Small Magellanic Cloud (SMC) and Large Magellanic Cloud (LMC). We determine the effective temperature ($T_{\textrm{eff}}$) of each star by fitting their spectral energy distributions, as observed by VLT+SHOOTER, with MARCS model atmospheres. We find average temperatures of $…
We present a catalog of 1750 massive stars in the Large Magellanic Cloud, with accurate spectral types compiled from the literature, and a photometric catalog for a subset of 1268 of these stars, with the goal of exploring their infrared properties. The photometric catalog consists of stars with infrared counterparts in the Spitzer SAGE survey database, for which we present uniform photometry from 0.3-24 microns in the UBVIJHKs+IRAC+MIPS24 bands. The resulting infrared color-magnitude diagrams illustrate that the supergiant B[e], red supergiant and luminous blue variable (LBV) stars are among …
Most massive stars exchange mass with a companion, leading to evolution which is altered drastically from that expected of stars in isolation. Such systems are the result of unusual binary evolution pathways and, as such, may be used to place stringent constraints on the physics of these interactions. We use the R4 system's B[e] supergiant, which has been postulated to be the product of a binary stellar merger, to guide our understanding of such outcomes by comparing observations of R4 to the results of simulations of mergers performed with the 3d hydrodynamics code FLASH. Our approach tailors…
We recently discovered a yellow supergiant (YSG) in the Small Magellanic Cloud (SMC) with a heliocentric radial velocity of ~300 km/s which is much larger than expected for a star in its location in the SMC. This is the first runaway YSG ever discovered and only the second evolved runaway star discovered in a different galaxy than the Milky Way. We classify the star as G5-8I, and use de-reddened broad-band colors with model atmospheres to determine an effective temperature of 4700+/-250K, consistent with what is expected from its spectral type. The star's luminosity is then L/Lo ~ 4.2+/-0.1, c…
A review of the properties of the Tarantula Nebula (30 Doradus) in the Large Magellanic Cloud is presented, primarily from the perspective of its massive star content. The proximity of the Tarantula and its accessibility to X-ray through radio observations permit it to serve as a Rosetta Stone amongst extragalactic supergiant HII regions since one can consider both its integrated characteristics and the individual properties of individual massive stars. Recent surveys of its high mass stellar content, notably the VLT FLAMES Tarantula Survey (VFTS), are reviewed, together with VLT/MUSE observat…
To measure the mass loss from dusty oxygen-rich (O-rich) evolved stars in the Large Magellanic Cloud (LMC), we have constructed a grid of models of spherically-symmetric dust shells around stars with constant mass-loss rates using 2Dust. These models will constitute the O-rich model part of the "Grid of Red supergiant and Asymptotic giant branch star ModelS" (GRAMS). This model grid explores 4 parameters - stellar effective temperature from 2100 K - 4700 K; luminosity from 10^3-10^6 L_Sun; dust shell inner radii of 3, 7, 11, and 15 R_Star; and 10.0 micron optical depth from 10^-4 to 26. From a…
Red supergiants (RSGs) are evolved massive stars that represent extremes, in both their physical sizes and their cool temperatures, of the massive star population. Effective temperature ($T_{\rm eff}$) is the most critical physical property needed to place a RSG on the Hertzsprung-Russell Diagram, due to the stars' cool temperatures and resulting large bolometric corrections. Several recent papers have examined the potential utility of atomic line equivalent widths in cool supergiant spectra for determining $T_{\rm eff}$ and other physical properties (dorda2016b, dorda2016a) and found strong c…
The characteristics of light variation of RSGs in SMC are analyzed based on the nearly 8-10 year long data collected by the ASAS and MACHO projects. The identified 126 RSGs are classified into five categories accordingly: 20 with poor photometry, 55 with no reliable period, 6 with semi-regular variation, 15 with Long Secondary Period (LSP) and distinguishable short period and 30 with only LSP. For the semi-regular variables and the LSP variables with distinguishable short period, the Ks band period-luminosity (P-L) relation is analyzed and compared with that of the Galaxy, LMC and M33. It is f…
We report on the first detection of $^{13}$C enhancement in two B[e] supergiants in the Large Magellanic Cloud. Stellar evolution models predict the surface abundance in $^{13}$C to strongly increase during main-sequence and post-main sequence evolution of massive stars. However, direct identification of chemically processed material on the surface of B[e] supergiants is hampered by their dense, disk-forming winds, hiding the stars. Recent theoretical computations predict the detectability of enhanced $^{13}$C via the molecular emission in $^{13}$CO arising in the circumstellar disks of B[e] s…
X-Shooting ULLYSES: Massive Stars at low metallicity IX: Empirical constraints on mass-loss rates and clumping parameters for OB supergiants in the Large Magellanic Cloud
A code used previously to predict O-star mass fluxes as a function of metallicity is used to compute a grid of models with the metallicity of the Small Magellanic Cloud (SMC). These models allow mass-loss rates to be derived by interpolation for all O-type supergiants in the SMC, with the possible exception of extremely massive stars close to the Eddington limit.
The massive stars that survive the phase of red supergiants (RSGs) spend the rest of their life in extremity. Their unstable atmospheres facilitate the formation and episodic ejection of shells that alter the stellar appearance and surroundings. In the present study, we revise the evolutionary state of eight hypergiants in the Magellanic Clouds, four of early-A type and four of FG type, and complement the short list of the eruptive post-RSGs termed as yellow hypergiants (YHGs). We refine the outdated temperatures and luminosities of the stars by means of high-resolution spectroscopy with FEROS…
We present a catalog of 5324 massive stars in the Small Magellanic Cloud (SMC), with accurate spectral types compiled from the literature, and a photometric catalog for a subset of 3654 of these stars, with the goal of exploring their infrared properties. The photometric catalog consists of stars with infrared counterparts in the Spitzer, SAGE-SMC survey database, for which we present uniform photometry from 0.3-24 um in the UBVIJHKs+IRAC+MIPS24 bands. We compare the color magnitude diagrams and color-color diagrams to those of the Large Magellanic Cloud (LMC), finding that the brightest infra…
The characteristics of IR properties and MIR variability of RSGs in the LMC are analyzed based on 12 bands of NIR to MIR co-added data from 2MASS, Spitzer and WISE, and $\sim$6.6 years of MIR time-series data collected by the ALLWISE and NEOWISE-R projects. 773 RSGs candidates were compiled from the literature and verified by using the CMD, SED and MIR variability. About 15\% of valid targets in the $IRAC1-IRAC2$/$IRAC2-IRAC3$ diagram may show PAH emission. We show that arbitrary dereddening Q parameters related to the IRAC4, S9W, WISE3, WISE4, and MIPS24 bands could be constructed based on a …
Red supergiants (RSGs) are a He-burning phase in the evolution of moderately massive stars (10-25 solar masses). For many years, the assumed physical properties of these stars placed them at odds with the predictions of evolutionary theory. We have recently determined new effective temperatures and luminosities for the RSG populations of galaxies with a factor of ~8 range in metallicity, including the Milky Way, the Magellanic Clouds, and M31. We find that these new physical properties greatly improve the agreement between the RSGs and the evolutionary tracks, although there are still notable …
We present the most comprehensive RSG sample for the SMC up to now, including 1,239 RSG candidates. The initial sample is derived based on a source catalog for the SMC with conservative ranking. Additional spectroscopic RSGs are retrieved from the literature, as well as RSG candidates selected from the inspection of CMDs. We estimate that there are in total $\sim$ 1,800 or more RSGs in the SMC. We purify the sample by studying the infrared CMDs and the variability of the objects, though there is still an ambiguity between AGBs and RSGs. There are much less RSGs candidates ($\sim$4\%) showing P…
We present a study of the infrared properties of 4922 spectroscopically confirmed massive stars in the Large and Small Magellanic Clouds, focusing on the active OB star population. Besides OB stars, our sample includes yellow and red supergiants, Wolf-Rayet stars, Luminous Blue Variables (LBVs) and supergiant B[e] stars. We detect a distinct Be star sequence, displaced to the red, and find a higher fraction of Oe and Be stars among O and early-B stars in the SMC, respectively, when compared to the LMC, and that the SMC Be stars occur at higher luminosities. We also find photometric variability…
We examine the recent star formation associated with four supergiant shells (SGSs) in the Large Magellanic Cloud (LMC): LMC 1, 4, 5, and 6, which have been shown to have simple expanding-shell structures. H II regions and OB associations are used to infer star formation in the last few Myr, while massive young stellar objects (YSOs) reveal the current ongoing star formation. Distributions of ionized, H I, and molecular components of the interstellar gas are compared with the sites of recent and current star formation to determine whether triggering has taken place. We find that a great majorit…
We present the results of a spectroscopic investigation of two novel variable bright blue stars in the SMC, OGLE004336.91-732637.7 (SMC-SC3) and the periodically occulted star OGLE004633.76-731204.3 (SMC-SC4), whose photometric properties were reported by Mennickent et al. (2010). High-resolution spectra in the optical and far-UV show that both objects are actually A + B type binaries. Three spectra of SMC-SC4 show radial velocity variations, consistent with the photometric period of 184.26 days found in Mennickent et al. 2010. The optical spectra of the metallic lines in both systems show com…
