The multiplicity properties of massive stars are one of the important outstanding issues in stellar evolution. Quantifying the binary statistics of all evolutionary phases is essential to paint a complete picture of how and when massive stars interact with their companions, and to determine the consequences of these interactions. We investigate the multiplicity of an almost complete census of red supergiant stars (RSGs) in NGC 330, a young massive cluster in the SMC. Using a combination of multi-epoch HARPS and MUSE spectroscopy, we estimate radial velocities and assess the kinematic and multiplicity properties of 15 RSGs in NGC 330. Radial velocities are estimated to better than +/-100 m/s for the HARPS data. The line-of-sight velocity dispersion for the cluster is estimated as 3.20 +0.69-0.52 km/s. When virial equilibrium is assumed, the dynamical mass of the cluster is log (M{dyn} /M{sun}) = 5.20+/-0.17, in good agreement with previous upper limits. We detect significant radial velocity variability in our multi-epoch observations and distinguish between variations caused by atmospheric activity and those caused by binarity. The binary fraction of NGC 330 RSGs is estimated by comparisons with simulated observations of systems with a range of input binary fractions. In this way, we account for observational biases and estimate the intrinsic binary fraction for RSGs in NGC 330 as f{RSG} = 0.3+/-0.1 for orbital periods in the range 2.3< log P [days] <4.3, with q>0.1. Using the distribution of the luminosities of the RSG population, we estimate the age of NGC 330 to be 45+/-5 Myr and estimate a red straggler fraction of 50%. We estimate the binary fraction of RSGs in NGC 330 and conclude that it appears to be lower than that of main-sequence massive stars, which is expected because interactions between an RSG and a companion are assumed to effectively strip the RSG envelope.
We present K-band Multi-Object Spectrograph (KMOS) observations of 18 Red Supergiant (RSG) stars in the Sculptor Group galaxy NGC 55. Radial velocities are calculated and are shown to be in good agreement with previous estimates, confirming the supergiant nature of the targets and providing the first spectroscopically confirmed RSGs in NGC 55. Stellar parameters are estimated for 14 targets using the $J$-band analysis technique, making use of state-of-the-art stellar model atmospheres. The metallicities estimated confirm the low-metallicity nature of NGC 55, in good agreement with previous stu…
Studies on the massive star population in galaxies beyond the Local Group are the key to understand the link between their numbers and modes of star formation in different environments. We present the analysis of the massive star population of the galaxies NGC 1326A, NGC 1425 and NGC 4548 using archival Hubble Space Telescope Wide Field Planetary Camera 2 images in the F555W and F814W filters. Through high precision point spread function fitting photometry for all sources in the three fields we identified 7640 candidate blue supergiants, 2314 candidate yellow supergiants, and 4270 candidate re…
We present near-IR spectroscopy of red supergiant (RSG) stars in NGC 6822, obtained with the new VLT-KMOS instrument. From comparisons with model spectra in the J-band we determine the metallicity of 11 RSGs, finding a mean value of [Z] = -0.52 $\pm$ 0.21 which agrees well with previous abundance studies of young stars and HII regions. We also find an indication for a low-significance abundance gradient within the central 1 kpc. We compare our results with those derived from older stellar populations and investigate the difference using a simple chemical evolution model. By comparing the physi…
Using archival near-IR photometry, we identify 51 of the K-band brightest red supergiants (RSGs) in NGC 6822 and compare their physical properties with stellar evolutionary model predictions. We first use Gaia parallax and proper motion values to filter out foreground Galactic red dwarfs before constructing a J - K vs. K color-magnitude diagram to eliminate lower-mass asymptotic giant branch star contaminants in NGC 6822. We then cross-match our results to previously spectroscopically confirmed RSGs and other NGC 6822 content studies and discuss our overall completeness, concluding that radial…
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…
The mass loss rates of red supergiants (RSGs) govern their evolution towards supernova and dictate the appearance of the resulting explosion. To study how mass-loss rates change with evolution we measure the mass-loss rates (\mdot) and extinctions of 19 red supergiants in the young massive cluster NGC2100 in the Large Magellanic Cloud. By targeting stars in a coeval cluster we can study the mass-loss rate evolution whilst keeping the variables of mass and metallicity fixed. Mass-loss rates were determined by fitting DUSTY models to mid-IR photometry from WISE and Spitzer/IRAC. We find that the…
We present a quantitative analysis of the low-resolution (4.5 A) spectra of 12 late-B and early-A blue supergiants (BSGs) in the metal-poor dwarf galaxy NGC 3109. A modified method of analysis is presented which does not require use of the Balmer jump as an independent temperature indicator, as used in previous studies. We determine stellar effective temperatures, gravities, metallicities, reddening, and luminosities, and combine our sample with the early-B type BSGs analyzed by Evans et al. (2007) to derive the distance to NGC 3109 using the Flux-weighted Gravity-Luminosity Relation (FGLR). U…
A quantitative spectral analysis of BA-type supergiants and bright giants in an inner spiral arm region of the nearby spiral galaxy NGC 300 is presented, based on observations with the Multi Unit Spectroscopic Explorer (MUSE) on the European Southern Obsevatory, Very Large Telescope (ESO, VLT). The flux-weighted gravity-luminosity relationship (FGLR), a stellar spectroscopic distance determination method for galaxies, is extended towards stars at lower luminosities. Point spread function fitting 3D spectroscopy was performed with PampelMUSE on the datacube. The 16 stars with the highest signal…
We study the post-main sequence stars in NGC 604, the most luminous HII region in M33. Previously, a number of Wolf-Rayet (WR) stars and one red supergiant (RSG) have been discovered. Based on broadband photometry of the region, we present evidence that is consistent with the presence of this RSG and with three more RSG candidates. Using SED fitting based on HST UVIJHK photometry we estimate the ages of the WR stars and RSGs finding that the two populations are from distinct formation episodes with ages 3.2$\pm%1.0Myrs and 12.4$\pm$2.1Myrs, respectively. The RSGs have greater extinctions towar…
We analyzed the massive star population of the Virgo Cluster galaxy NGC 4535 using archival Hubble Space Telescope Wide Field Planetary Camera 2 images in filters F555W and F814W, equivalent to Johnson V and Kron-Cousins I. We performed high precision point spread function fitting photometry of 24353 sources including 3762 candidate blue supergiants, 841 candidate yellow supergiants and 370 candidate red supergiants. We estimated the ratio of blue to red supergiants as a decreasing function of galactocentric radius. Using Modules for Experiments in Stellar Astrophysics isochrones at solar meta…
We have obtained K-band Multi-Object Spectrograph (KMOS) near-IR spectroscopy for 14 red supergiant stars (RSGs) in the young massive star cluster NGC 2100 in the Large Magellanic Cloud (LMC). Stellar parameters including metallicity are estimated using the J-band analysis technique, which has been rigorously tested in the Local Universe. We find an average metallicity for NGC 2100 of [Z]=$-$0.43$\pm$0.10 dex, in good agreement with estimates from the literature for the LMC. Comparing our results in NGC 2100 with those for a Galactic cluster (at Solar-like metallicity) with a similar mass and …
Galactic, young massive star clusters are approximately coeval aggregates of stars, close enough to resolve the individual stars, massive enough to have produced large numbers of massive stars, and young enough for these stars to be in a pre-supernova state. As such these objects represent powerful natural laboratories in which to study the evolution of massive stars. To be used in this way, it is crucial that accurate and precise distances are known, since this affects both the inferred luminosities of the cluster members and the age estimate for the cluster itself. Here we present distance e…
We have combined resolved stellar photometry from Hubble Space Telescope (\emph{HST}), \emph{Spitzer}, and \emph{Gaia} to identify red supergiant (RSG) candidates in NGC~6946, based on their colors, proper motions, visual morphologies, and spectral energy distributions. We start with a large sample of 17,865 RSG candidates based solely on \emph{HST} near-infrared photometry. We then chose a small sample of 385 of these candidates with Spitzer matches for more detailed study. Using evolutionary models and isochrones, we isolate a space where RSGs would be found in our photometry catalogs. We th…
We present moderate-resolution spectroscopic observations of red supergiants (RSGs) in the low-metallicity Local Group galaxies NGC 6822 (Z = 0.4Zsun) and Wolf-Lundmark-Melotte (WLM; Z = 0.1Zsun). By combining these observations with reduction techniques for multislit data reduction and flux calibration, we are able to analyze spectroscopic data of 16 RSGs in NGC 6822 and spectrophotometric data of 11 RSGs in WLM. Using these observations we determine spectral types for these massive stars, comparing them to Milky Way and Magellanic Clouds RSGs and thus extending observational evidence of the …
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…
This work establishes the most complete sample of red supergiants (RSGs) in twelve low-mass galaxies (WLM, IC 10, NGC 147, NGC 185, IC 1613, Leo A, Sextans B, Sextans A, NGC 6822, Pegasus Dwarf, SMC and LMC) of the Local Group, which forms the solid basis to study the properties of RSGs as well as the star formation rate (SFR) and initial mass function (IMF) of the galaxies. After removing the foreground dwarf stars by their obvious branch in the near-infrared color-color diagram ($(J-H)_0/(H-K)_0$) with the UKIRT/WFCAM and 2MASS photometry as well as the Gaia/EDR3 measurements of proper motio…
The open cluster NGC 7419 is known to contain five red supergiants and a very high number of Be stars. However, there are conflicting reports about its age and distance that prevent a useful comparison with other clusters. We intend to obtain more accurate parameters for NGC 7419, using techniques different from those of previous authors, so that it may be used as a calibrator for more obscured clusters. We obtained Strömgren photometry of the open cluster NGC 7419, as well as classification spectroscopy of ~20 stars in the area. We then applied standard analysis and classification techniques.…
We present a case study of using a novel method to identify red supergiant (RSG) candidates in NGC 6822, based on their 1.6 $μ$m "H-bump". We collected 32 bands of photometric data for NGC 6822 ranging from optical to MIR. By using the theoretical spectra from MARCS, we demonstrate that there is a prominent difference around 1.6 $μ$m ("H-bump") between low-surface-gravity (LSG) and high-surface-gravity (HSG) targets. Taking advantage of this feature, we identify efficient color-color diagrams (CCDs) of rzH and rzK to separate HSG and LSG targets from crossmatching of optical and NIR data. More…
SN2010da/NGC 300 ULX-1 was first detected as a supernova impostor in May 2010 and was recently discovered to be a pulsating ultraluminous X-ray source. In this letter, we present VLT/X-shooter spectra of this source obtained in October 2018, covering the wavelength range 350-2300 nm. The $J$- and $H$-bands clearly show the presence of a red supergiant donor star that is best matched by a MARCS stellar atmosphere with $T_{\rm eff} = 3650 - 3900$ K and $\log(L_{\rm bol}/L_{\odot}) = 4.25\pm0.10$, which yields a stellar radius $R = 310 \pm 70 R_{\odot}$. To fit the full spectrum, two additional c…
JWST Reveals a Galaxy-Wide Association of Red Supergiants with OB Stars in NGC 5584
School of Physics and Astronomy, China West Normal University（西华师范大学物理与天文学学院）；School of Physics and Astronomy, Beijing Normal University（北京师范大学物理与天文学院）；Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University（北京师范大学前沿天文与天体物理研究所）；CAS Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台光学天文重点实验室）
We describe new results on two supernova impostors in NGC 2403, SN 1954J(V12) and SN 2002kg(V37). For the famous object SN 1954J we combine four critical observations: its current SED, its Halpha emission line profile, the Ca II triplet in absorption in its red spectrum, and the brightness compared to its pre-event state. Together these strongly suggest that the survivor is now a hot supergiant with T ~ 20000 K, a dense wind, substantial circumstellar extinction, and a G-type supergiant companion. The hot star progenitor of V12's giant eruption was likely in the post-red supergiant stage and h…
Through comparison of pre- and post-explosion images obtained with the Wide Field and Planetary Camera 2 onboard the Hubble Space Telescope, we have isolated a supergiant star prior to explosion at nearly the same position as the high-luminosity SN II-P 2008cn. We provide evidence that this supergiant may well be the progenitor of the SN, although this identification is not entirely unambiguous due mainly to the distance to the host galaxy (NGC 4603), 33.3 Mpc. The progenitor candidate has a more yellow color than generally would be expected and, if a single star, would require that it explode…
It is well known that massive O-stars are frequently (if not always) found in binary or higher-order multiple systems, but this fact has been less robustly investigated for the lower mass range of the massive stars, represented by the B-type stars. Obtaining the binary fraction and orbital parameter distributions of B-type stars is crucial to understand the impact of multiplicity on the archetypal progenitor of core-collapse supernovae as well as to properly investigate formation channels for gravitational wave progenitors. This work aims to characterise the multiplicity of the B-star populati…
WIYN/Hydra spectra (R $\sim$ 13,500, signal-to-noise pixel$^{-1}$ = 50-1000) of a 400 $\unicode{x212B}$ region around Li 6708 $\unicode{x212B}$ are used to determine radial and rotational velocities for 287 photometrically selected candidate members of the open cluster M48. The sample ranges from turnoff A stars to late-K dwarfs and eight giants. We combine our $V_{\rm{RAD}}$ measurements and power spectrum analysis with parallax and proper motion data from Gaia DR2 to evaluate membership and multiplicity. We classify 152 stars as single cluster members, 11 as binary members, 16 as members of …
We study the near-infrared properties of the super star cluster NGC1750-1 in order to constrain its spatial extent, its stellar population and its age. We use adaptive optics assisted integral field spectroscopy with SINFONI on the VLT. We estimate the spatial extent of the cluster and extract its K-band spectrum from which we constrain the age of the dominant stellar population. Our observations have an angular resolution of about 0.11", providing an upper limit on the cluster radius of 2.85+/-0.50 pc depending on the assumed distance. The K-band spectrum is dominated by strong CO absorption …
Observations of massive stars in young open clusters (< ~8 Myr) have shown that a majority of them are in binary systems, most of which will interact during their life. Populations of massive stars older than ~20 Myr allow us to probe the outcome of such interactions after many systems have experienced mass and angular momentum transfer. Using multi-epoch integral-field spectroscopy, we investigate the multiplicity properties of the massive-star population in NGC 330 (~40 Myr) in the Small Magellanic Cloud to search for imprints of stellar evolution on the multiplicity properties. From six epo…
The quantitative study of the physical properties and chemical abundances of large samples of massive blue stars at different metallicities is a powerful tool to understand the nature and evolution of these objects. Their analysis beyond the Milky Way is challenging, nonetheless it is doable and the best way to investigate their behavior in different environments. Fulfilling this task in an objective way requires the implementation of automatic analysis techniques that can perform the analyses systematically, minimizing at the same time any possible bias. As part of the ARAUCARIA project we ca…
Context: High-mass stars have a high degree of multiplicity and most likely form via disk accretion processes. The detailed physics of the binary and disk formation are still poorly constrained. Methods: Using the VLA in its most extended configuration at ~24GHz toward the prototypical high-mass star-forming region NGC7538IRS1 has allowed us to study the NH3 and thermal CH3OH emission and absorption as well as the cm continuum emission at an unprecedented spatial resolution of 0.06"x0.05", corresponding to a linear resolution of ~150AU at a distance of 2.7kpc. Results: A comparison of these ne…
Luminous Red Novae (LRNe) are astrophysical transients associated with the partial ejection of a binary system's common envelope (CE) shortly before its merger. Here we present the results of our photometric and spectroscopic follow-up campaign of AT2018bwo (DLT18x), a LRN discovered in NGC45, and investigate its progenitor system using binary stellar-evolution models. The transient reached a peak magnitude of $M_r=-10.97\pm0.11$ and maintained this brightness during its optical plateau of $t_p = 41\pm5$days. During this phase, it showed a rather stable photospheric temperature of ~3300K and a…
We present VLA and ALMA imaging of the deeply-embedded protostellar cluster NGC6334I from 5 cm to 1.3 mm at angular resolutions as fine as 0.17 (220 AU). The dominant hot core MM1 is resolved into seven components at 1.3 mm, clustered within a radius of 1000 AU. Four of the components have brightness temperatures >200 K, radii ~300 AU, minimum luminosities ~10000 Lsun, and must be centrally heated. We term this new phenomenon a "hot multi-core". Two of these objects also exhibit compact free-free emission at longer wavelengths, consistent with a hypercompact HII region (MM1B) and a jet (MM1D).…
Aims. We present the results obtained from a long-term spectroscopic campaign devoted to the multiplicity of O-type stars in the young open cluster NGC2244 and in the Mon OB2 association. Methods. Our spectroscopic monitoring was performed over several years, allowing us to probe different time-scales. For each star, several spectral diagnostic tools are applied, in order to search for line shifts and profile variations. We also measure the projected rotational velocity and revisit the spectral classification. Results. In our sample, several stars were previously considered as spectroscopic bi…
A majority of massive stars are part of binary systems, a large fraction of which will inevitably interact during their lives. Binary-interaction products (BiPs), i.e. stars affected by such interaction, are expected to be commonly present in stellar populations. BiPs are thus a crucial ingredient in the understanding of stellar evolution. We aim to identify and characterize a statistically significant sample of BiPs by studying clusters of 10-40 Myr, an age at which binary population models predict the abundance of BiPs to be highest. One example of such a cluster is NGC 330 in the Small Mage…
A massive star can enter the blue supergiant region either evolving directly from the main-sequence, or evolving from a previous red supergiant stage. The fractions of the blue supergiants having different histories depend on the internal mixing and mass-loss during the red supergiant stage. We study the possibility to use diagnostics based on stellar pulsation to discriminate blue supergiants having different evolution histories. For this purpose we have studied the pulsation property of massive star models calculated with the Geneva stellar evolution code for initial masses ranging from 8 to…
Quantifying Systematic Age Discrepancies in Very Young Star Clusters
Florida State University（佛罗里达州立大学）；Liverpool John Moores University（利物浦约翰摩尔斯大学）；University of Washington（华盛顿大学）；Center for Computational Astrophysics, Flatiron Institute（纽约市立大学高等研究院计算天体物理中心）；Steward Observatory, University of Arizona（亚利桑那大学斯图尔德天文台）；University of Virginia（弗吉尼亚大学）
We report mid- to far-infrared imaging and photomety from 7 to 37 microns with SOFIA/FORCAST and 2 micron adaptive optics imaging with LBTI/LMIRCam of a large sample of red supergiants (RSGs) in four Galactic clusters; RSGC1, RSGC2=Stephenson 2, RSGC3, and NGC 7419. The red supergiants in these clusters cover their expected range in luminosity and initial mass from approximately 9 to more than 25 Solar masses. The population includes examples of very late-type RSGs such as MY Cep which may be near the end of the RSG stage, high mass losing maser sources, yellow hypergiants and post-RSG candida…
The Progenitor of the Type II-Plateau SN 2025pht in NGC 1637: The Dustiest, Most Luminous Red Supergiant So Far?
Caltech/IPAC（加州理工学院/喷气推进实验室）；University of Szeged（塞格德大学）；MTA-ELTE Lendület ”Momentum” Milky Way Research Group（匈牙利科学院-罗兰大学引力研究组“动量”银河系研究小组）；Space Telescope Science Institute（太空望远镜科学研究所）；University of California, Berkeley（加利福尼亚大学伯克利分校）；Purdue University（普渡大学）
Images recorded with the Gemini Multi-Object Spectrograph (GMOS) on Gemini South are combined with archival images from other facilities to search for variable stars in the southern portion of the nearby disk galaxy NGC 247. Fifteen new periodic and non-periodic variables are identified. These include three Cepheids with periods < 25 days, four semi-regular variables, one of which shows light variations similar to those of R CrB stars, five variables with intrinsic visible/red brightnesses and colors that are similar to those of luminous blue variables (LBVs), and three fainter blue variables,…
We present the results of spectroscopy and multi-wavelength photometry of luminous and variable star candidates in the nearby spiral galaxies NGC 2403 and M81. We discuss specific classes of stars, the Luminous Blue Variables (LBVs), B[e] supergiants (sgB[e]), and the high luminosity yellow hypergiants. We identify two new LBV candidates, and three sgB[e] stars in M81. We also find that some stars previously considered LBV candidates are actually field stars. The confirmed and candidate LBVs and sgB[e] stars together with the other confirmed members are shown on the HR Diagrams for their respe…
With red supergiants (RSGs) predicted to end their lives as Type IIP core collapse supernova (CCSN), their behaviour before explosion needs to be fully understood. Mass loss rates govern RSG evolution towards SN and have strong implications on the appearance of the resulting explosion. To study how the mass-loss rates change with the evolution of the star, we have measured the amount of circumstellar material around 19 RSGs in a coeval cluster. Our study has shown that mass loss rates ramp up throughout the lifetime of an RSG, with more evolved stars having mass loss rates a factor of 40 highe…
The open cluster Stephenson 2 contains the largest collection of red supergiants known in the Galaxy, and at present is the second most massive young cluster known in the Milky Way. We have obtained multi-epoch, intermediate-resolution spectra around the CaII triplet for more than 30 red supergiants in Stephenson~2 and its surroundings. We find a clear separation between a majority of RSGs having spectral types M0-M2 and the brightest members in the NIR, which have very late spectral types and show strong evidence for heavy mass loss. The distribution of spectral types is similar to that of RS…
We report the identification of the unusual emission-line stellar-like object in the nearby low-metallicity (Z ~ 0.1Zsun) dwarf galaxy NGC 4068. Our observations performed with long-slit spectrograph and Fabry-Perot interferometer demonstrate high velocity dispersion in Ha line, presence of HeII4686A line and peculiarly low [SII]/[NII] fluxes ratio for this object. From observational data, we derived that the object represents a single star of high bolometric luminosity L~1.5*10^6 Lsun surrounded by an expanding nebula with kinematical age of t ~ 0.5Myr. The nebula exhibits significant nitroge…
Evolutionary models have shown the substantial effect that strong mass-loss rates ($\dot{M}$) can have on the fate of massive stars. Red supergiant (RSG) mass-loss is poorly understood theoretically, and so stellar models rely on purely empirical \mdot-luminosity relations to calculate evolution. Empirical prescriptions usually scale with luminosity and effective temperature, but $\dot{M}$ should also depend on the current mass and hence the surface gravity of the star, yielding more than one possible $\dot{M}$ for the same position on the Hertzsprung-Russell diagram. One can solve this degene…
We present the analysis of near infrared (NIR), adaptive optics (AO) Subaru and archived HST imaging data of a region near the northern middle lobe (NML) of the Centaurus A (Cen A) jet, at a distance of $\sim15$ kpc north-east (NE) from the center of NGC5128. Low-pass filtering of the NIR images reveals strong -- $>3σ$ above the background mean -- signal at the expected position of the brightest star in the equivalent HST field. Statistical analysis of the NIR background noise suggests that the probability to observe $>3σ$ signal at the same position, in three independent measurements due to s…
We present the first detection of 24 μm variability in 24 sources in the Local Group galaxy M33. These results are based on 4 epochs of MIPS observations, which are irregularly spaced over ~750 days. We find that these sources are constrained exclusively to the Holmberg radius of the galaxy, which increases their chances of being members of M33. We have constructed spectral energy distributions (SEDs) ranging from the optical to the sub-mm to investigate the nature of these objects. We find that 23 of our objects are most likely heavily self-obscured, evolved stars; while the remaining source …
We examine the spectroscopic binary population for two massive nearby regions of clustered star formation, the Orion Nebula Cluster and NGC 2264, supplementing the data presented by Tobin et al. (2009, 2015) with more recent observations and more extensive analysis. The inferred multiplicity fraction up to 10 AU based on these observations is $5.3\pm 1.2$% for NGC 2264 and $5.8\pm 1.1$% for the ONC; they are consistent with the distribution of binaries in the field in the relevant parameter range. Eight of the multiple systems in the sample have enough epochs to make an initial fit for the orb…
An increasing number of non-terminal giant eruptions are being observed by modern supernova and transient surveys. But very little is known about the origin of these giant eruptions and their progenitors, many of which are presumably very massive, evolved stars. Motivated by the small number of progenitors positively associated with these giant eruptions, we have begun a survey of the evolved massive star populations in nearby galaxies. The nearby, nearly face on, giant spiral M101 is an excellent laboratory for studying a large population of very massive stars. In this paper, we present BVI p…
The Red Supergiant Progenitor of the Type II Supernova 2024abfl
Yunnan Observatories, Chinese Academy of Sciences (CAS)（中国科学院云南天文台）；University of Chinese Academy of Sciences（中国科学院大学）；International Centre of Supernovae, Yunnan Key Laboratory（超新星国际中心，云南省重点实验室）；South-Western Institute for Astronomy Research, Yunnan University（云南大学西南天文研究所）
The fate of massive stars with initial masses >8M$_\odot$ depends largely on the mass-loss rate (\mdot ) in the end stages of their lives. Red supergiants (RSGs) are the direct progenitors to Type II-P core collapse supernovae (SN), but there is uncertainty regarding the scale and impact of any mass-loss during this phase. Here we used near and mid-IR photometry and the radiative transfer code DUSTY to determine luminosity and \mdot\ values for the RSGs in two Galactic clusters (NGC 7419 and $χ$ Per) where the RSGs are all of similar initial mass ($M_{\rm initial}$$\sim$16M$_\odot$), allowing …
The giant HII region NGC 604 constitutes a complex and rich population to studying detail many aspects of massive star formation, such as their environments and physical conditions, the evolutionary processes involved, the initial mass function for massive stars and star-formation rates, among many others. Here, we present our first results of a near-infrared study of NGC 604 performed with NIRI images obtained with Gemini North. Based on deep JHK photometry, 164 sources showing infrared excess were detected, pointing to the places where we should look for star-formation processes currently ta…
