Type II-P supernovae (SNeII-P) are the most common class of core-collapse SNe in the local Universe and play critical roles in many aspects of astrophysics. Since decades ago theorists have predicted that SNeII-P may originate not only from single stars but also from interacting binaries. While ∼20 SNII-P progenitors have been directly detected on pre-explosion images, observational evidence still remains scarce for this speculated binary progenitor channel. In this work, we report the discovery of a red supergiant progenitor for the Type II-P SN2018gj. While the progenitor resembles those of other SNeII-P in terms of effective temperature and luminosity, it is located in a very old environment, and SN2018gj has an abnormally short plateau in the light curve. With state-of-the-art binary evolution simulations, we find these characteristics can only be explained if the progenitor of SN2018gj is the merger product of a close binary system, which developed a different interior structure and evolved over a longer timescale compared with single-star evolution. This work provides the first compelling evidence for the long-sought binary progenitor channel toward SNeII-P, and our methodology serves as an innovative and pragmatic tool to motivate further investigations into this previously hidden population of SNeII-P from binaries.

Metallicity plays a crucial role in the evolution of massive stars and their final core-collapse supernova (CCSN) explosions. Integral-field-unit (IFU) spectroscopy can provide a spatially resolved view of SN host galaxies and serve as a powerful tool to study SN metallicities. While early transient surveys targeted on high star formation rate and metallicity galaxies, recent untargeted, wide-field surveys (e.g., ASAS-SN, ZTF) have discovered large numbers of SNe without this bias. In this work, we construct a large sample of SNe discovered by wide-field untargted searches, consisting of 166 SNe of Types II(P), IIn, IIb, Ib and Ic at z ≤ 0.02 with VLT/MUSE observations. This is currently the largest CCSN sample with IFU observations. With the strong-line method, we reveal the spatially-resolved metallicity maps of the SN host galaxies and acquire accurate metallicity measurements for the SN sites, finding a range from 12 + log(O/H) = 8.1 to 8.7 dex. And the metallicity distributions for different SN types are very close to each other, with mean and median values of 8.4–8.5 dex. Our large sample size narrows the 1σ uncertainty down to only 0.05 dex. The apparent metallicity differences among SN types are all within ∼1σ uncertainties and the metallicity distributions for different SN types are all consistent with being randomly drawn from the same reference distribution. This suggests that metallicity plays a minor role in the origin of different CCSN types and some other metallicity-insensitive processes, such as binary interaction, dominate the distinction of CCSN types.

To date, SN 2017ein is the only Type Ic supernova with a directly identified progenitor candidate. This candidate points to a very massive (>45 M _⊙ ) Wolf–Rayet (WR) progenitor, but its disappearance after the explosion of SN 2017ein remains unconfirmed. In this work, we revisit SN 2017ein in late-time images acquired by the Hubble Space Telescope at 2.4–3.8 yr after peak brightness. We find this source has not disappeared, and its brightness and color remain almost the same as in the preexplosion images. Thus, we conclude that the preexplosion source is not the genuine progenitor of SN 2017ein. It is not much likelier to be a companion star of the progenitor since it has a much lower extinction than SN 2017ein; its color also seems inconsistent with a star cluster, indicated by the newly added magnitude limit in F336W, apart from F555W and F814W. We suggest, therefore, this source is an unrelated star in chance alignment with SN 2017ein. Based on the low ejecta mass, we propose that SN 2017ein is most likely originated from a moderately massive star with M _ini ∼ 8–20 M _⊙ , stripped by binary interaction, rather than a very massive WR progenitor.

Red supergiants may lose significant mass during the final 100-1000 yr before core collapse, shaping their circumstellar environment. The supernova (SN) shockwave propagating through this environment forms a shock-swept dense shell that interacts with the surrounding circumstellar material (CSM), generating secondary shocks that energize the ejecta and may power the SN during the nebular phase. In this work, we investigate the nebular spectrum of SN 2023ixf, observed 1-yr post-explosion (at +363 d) with the recently commissioned WEAVE instrument on the 4.2 m William Herschel Telescope. This marks the first supernova spectrum captured with WEAVE. In this spectrum, H alpha exhibits a peculiar evolution, flanked by blueward and redward broad components centred at similar to +/- 5650 km s(-1), features that have been observed in only a few SNe as early as 1-yr post-explosion. These features may indicate energy deposition from shock generated by the interaction of shock-swept dense shell with CSM expelled a few hundred years prior to the explosion. Comparisons of the +363 d spectrum with model spectra from the literature suggest a shock power of at least similar to 5 x 10(40 )ergs(-1) at this epoch. Additionally, analysis of the [O i] doublet and other emission lines helped to constrain the oxygen mass (less than or similar to 0.07 - 0.30 M-circle dot), He-core mass (less than or similar to 3 M-circle dot), and zero-age main sequence mass (less than or similar to 12 M-circle dot) for SN 2023ixf. The comparison with other Type II SNe highlights SN 2023ixf's unique shock interaction signatures and evidence of dust formation, setting it apart in terms of evolution and dynamics.

Type IIn supernovae (SNe) exhibit narrow hydrogen lines that arise from the strong interaction between ejecta and circumstellar material. It remains poorly understood, however, what progenitor stars give rise to these explosions. In this work, we perform a detailed analysis of the progenitor and environment of the nearby Type IIn SN 2010jl. With newer images taken by the Hubble Space Telescope, we confirm that the previously reported progenitor candidate is a blend of the progenitor itself and a field star cluster in its close vicinity. SN 2010jl has now become much fainter than the progenitor. The progenitor is very blue and luminous with an effective temperature of log T eff/K = 4.26 - 0.09 + 0.11 and a luminosity of log L/L circle dot = 6.52 - 0.16 + 0.20 . It is located in a very young star-forming region, but its luminosity is much higher than that expected from the environmental stellar populations. We suggest that the progenitor was in outburst when observed. Its nature and evolutionary history remain to be investigated.

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 circle dot. Our work provides an independent measurement of the progenitor mass, which is not affected by circumstellar extinction and pulsational brightness variability.

Type IIb supernovae are an important subclass of stripped-envelope supernovae (SNe), which show H lines only at early times. Their progenitors are believed to contain a low-mass H envelope before explosion. This work reports the discovery of a progenitor candidate in preexplosion Hubble Space Telescope images for the Type IIb SN 2017gkk. With detailed analysis of its spectral energy distribution and local environment, we suggest that the progenitor is most likely a yellow supergiant with significant circumstellar extinction and has an initial mass of about 16 M _⊙ , effective temperature log( T _eff /K) = 3.72 ± 0.08, and luminosity log( L / L _⊙ ) = 5.17 ± 0.04. This progenitor is not massive enough to strip envelope through stellar wind, and it supports an interacting binary progenitor channel and adds to the growing list of direct progenitor detections for Type IIb SNe. Future late-time observations will confirm whether this progenitor candidate has disappeared and reveal the putative binary companion that has survived the explosion.

The exponential growth of large-scale telescope arrays has boosted time-domain astronomy development but introduced operational bottlenecks, including labor-intensive observation planning, data processing, and real-time decision-making. Here we present the StarWhisper Telescope system, an AI agent framework automating end-to-end astronomical observations for surveys like the Nearby Galaxy Supernovae Survey. By integrating large language models with specialized function calls and modular workflows, StarWhisper Telescope autonomously generates site-specific observation lists, executes real-time image analysis via pipelines, and dynamically triggers follow-up proposals upon transient detection. The system reduces human intervention through automated observation planning, telescope controlling and data processing, while enabling seamless collaboration between amateur and professional astronomers. Deployed across Nearby Galaxy Supernovae Survey's network of 10 amateur telescopes, the StarWhisper Telescope has detected transients with promising response times relative to existing surveys. Furthermore, StarWhisper Telescope's scalable agent architecture provides a blueprint for future facilities like the Global Open Transient Telescope Array, where AI-driven autonomy will be critical for managing 60 telescopes.

This paper reports an environmental analysis of 41 uniformly-selected stripped-envelope supernovae (SESNe) based on deep ultraviolet-optical images acquired by the Hubble Space Telescope. Young stellar populations are detected in most SN environments and their ages are derived with a hierarchical Bayesian approach. The age distributions are indistinguishable between Type IIb and Type Ib while that for Type Ic is systematically younger. This suggests that the Type Ic SN progenitors are more massive while the Type IIb and Type Ib SNe have very similar progenitor masses. Our result supports a hybrid envelope-stripping mechanism, in which the hydrogen envelopes of the SESN progenitors are stripped via a mass-insensitive process (e.g. binary interaction) while the helium envelopes are stripped via a mass-sensitive process (e.g. stellar wind of the post-binary interaction progenitor). We also provide progenitor constraints for three Type Ibn SNe and two broad-lined Type Ic SNe. All these results demonstrate the importance of the very diverse mass-loss processes in the origins of SESNe.

As one of the closest supernovae (SNe) in the last decade, SN 2023ixf is an unprecedented target to investigate the progenitor star that exploded. However, there is still significant uncertainty in the reported progenitor properties. In this work, we present a detailed study of SN 2023ixf’s progenitor with two independent analyses. We first modeled its spectral energy distribution (SED) based on Hubble Space Telescope optical, Spitzer mid-infrared (IR), and ground-based near-IR data. We find that stellar pulsation and circumstellar extinction have great impacts on SED fitting, and the result suggests a relatively massive red supergiant surrounded by C-rich dust with an initial mass of 16.2–17.4 M _⊙ . The corresponding rate of mass loss occurring at least 3 yr before the SN explosion is about 2 × 10 ^−4 M _⊙ yr ^−1 . We also derived the star formation history of the SN environment based on resolved stellar populations, and the most recent star-forming epoch corresponds to a progenitor initial mass of 17–19 M _⊙ , in agreement with that from our SED fitting. Therefore, we conclude that the progenitor of SN 2023ixf is close to the high-mass end for Type II SN progenitors.

ABSTRACT The nature of the newly discovered fast blue optical transients (FBOTs) is still puzzling astronomers. In this paper, we carry out a comprehensive analysis of the molecular gas, ionized gas, and stellar populations in the environment of the nearby FBOT AT2018cow based on ALMA, VLT/MUSE, and HST/WFC3 observations. A prominent molecular concentration of 6 (± 1) × 106 M⊙ is found in the vicinity of AT2018cow, which has given rise to two active star-forming complexes with ages of 4 ± 1 and ≲2.5 Myr, respectively. Each star-forming complex has a stellar mass of 3 × 105 M⊙, and has photoionized a giant H ii region with Hα luminosity even comparable to that of the 30 Dor mini-starburst region. AT2018cow is spatially coincident with one of the star-forming complexes; however, it is most likely to reside in its foreground since it has a much smaller extinction than the complex. Its progenitor could have been formed in a different star-forming event, and the non-detection of the associated stellar population constrains the progenitor’s age to be ≳10 Myr and initial mass to be ≲20 M⊙. We further find the late-time brightness of AT2018cow is unlikely to be a stellar object. Its brightness has slightly declined from 2 to 4 yr after explosion and is most likely to originate from AT2018cow itself due to some powering mechanism still working at such late times.

We perform a statistical clustering analysis of upper main-sequence stars in the Large Magellanic Cloud (LMC) using data from the Visible and Infrared Survey Telescope for Astronomy survey of the Magellanic Clouds. We map over 2500 young stellar structures at 15 significance levels across 120 square degrees centred on the LMC. The structures have sizes ranging from a few parsecs to over 1 kpc. We find that the young structures follow power-law size and mass distributions. From the perimeter-area relation, we derive a perimeter-area dimension of 1.44+-0.20. From the mass-size relation and the size distribution, we derive two-dimensional fractal dimensions of 1.50+-0.10 and 1.61+-0.20, respectively. We find that the surface density distribution is well-represented by a lognormal distribution. We apply the Larson relation to estimate the velocity dispersions and crossing times of these structures. Our results indicate that the fractal nature of the young stellar structures has been inherited from the gas clouds from which they form and that this architecture is generated by supersonic turbulence. Our results also suggest that star formation in the LMC is scale-free from 10 pc to 700 pc.

We report the discovery of a luminous late-time source at the position of the fast blue optical transient (FBOT) AT2018cow on images taken by the Hubble Space Telescope (HST) at 714 d and 1136 d after its explosion. This source is detected at both UV and optical wavelengths and has prominent H$\alpha$ emission. It has a very stable brightness between the two epochs and a very blue spectral energy distribution (SED) consistent with $f_\lambda$ $\propto$ $\lambda^{-4.1 \pm 0.1}$, i.e. the Rayleigh-Jeans tail of a hot blackbody with a very high temperature of log($T$/K) $>$ 4.6 and luminosity of log($L$/$L_\odot$) $>$ 7.0. This late-time source is unlikely to be an unrelated object in chance alignment, or due to a light echo of AT2018cow. Other possible scenarios also have some difficulties in explaining this late-time source, including companion star(s), star cluster, the survived progenitor star, interaction with circumstellar medium (CSM), magnetar, or delayed accretion in a tidal disruption event (TDE). Long-term and multi-wavelength monitoring will help to resolve its nature and finally reveal the origin of the "Cow".

ABSTRACT SN 2019yvr is the second Type Ib supernova (SN) with a possible direct detection of its progenitor (system); however, the spectral energy distribution (SED) of the pre-explosion source appears much cooler and overluminous than an expected helium-star progenitor. Using Hubble Space Telescope (HST) images and MUSE integral-field-unit (IFU) spectroscopy, we find the SN environment contains three episodes of star formation; the low ejecta mass suggests the SN progenitor is most likely from the oldest population, corresponding to an initial mass of 10.4$^{+1.5}_{-1.3}$ M⊙. The pre-explosion SED can be reproduced by two components, one for the hot and compact SN progenitor and one for a cool and inflated yellow hypergiant (YHG) companion that dominates the brightness. Thus, SN 2019yvr could possibly be the first Type Ib/c SN for which the progenitor’s binary companion is directly detected on pre-explosion images. Both the low progenitor mass and the YHG companion suggest significant binary interaction during their evolution. Similar to SN 2014C, SN 2019yvr exhibits a metamorphosis from Type Ib to Type IIn, showing signatures of interaction with hydrogen-rich circumstellar material (CSM) at >150 d; our result supports enhanced pre-SN mass-loss as an important process for hydrogen-poor stars at the lower mass end of core-collapse SN progenitors.

We used data from the near-infrared Visible and Infrared Telescope for Astronomy (VISTA) survey of the Magellanic Cloud system (VMC) to measure proper motions (PMs) of stars within the Small Magellanic Cloud (SMC). The data analysed in this study comprise 26 VMC tiles, covering a total contiguous area on the sky of similar to 40deg(2). Using multi-epoch observations in the K-s band over time baselines between 13 and 38 months, we calculated absolute PMs with respect to similar to 130000 background galaxies. We selected a sample of similar to 2160000 likely SMC member stars to model the centre-of-mass motion of the galaxy. The results found for three different choices of the SMC centre are in good agreement with recent space-based measurements. Using the systemic motion of the SMC, we constructed spatially resolved residual PM maps and analysed for the first time the internal kinematics of the intermediate-age/old and young stellar populations separately. We found outward motions that point either towards a stretching of the galaxy or stripping of its outer regions. Stellar motions towards the North might be related to the 'Counter Bridge' behind the SMC. The young populations show larger PMs in the region of the SMC Wing, towards the young Magellanic Bridge. In the older populations, we further detected a coordinated motion of stars away from the SMC in the direction of the Old Bridge as well as a stream towards the SMC.

ABSTRACT We have derived high-spatial-resolution metallicity maps covering ∼42 deg2 across the Small Magellanic Cloud (SMC) in an attempt to understand its metallicity distribution and gradients up to a radius of ∼4○. Using the near-infrared VISTA Survey of the Magellanic Clouds, our data cover a thrice larger area compared with previous studies. We identify red giant branch (RGB) stars in spatially distinct Y, (Y − Ks) colour–magnitude diagrams. In any of our selected subregions, the RGB slope is used as an indicator of the average metallicity, based on calibration to metallicity using spectroscopic data. The metallicity distribution across the SMC is unimodal and can be fitted by a Gaussian distribution with a peak at [Fe/H] = −0.97 dex (σ[Fe/H] = 0.05 dex). We find evidence of a shallow gradient in metallicity (−0.031 ± 0.005 dex deg−1) from the Galactic Centre to radii of 2○–2${_{.}^{\circ}}$5, followed by a flat metallicity trend from ∼3${_{.}^{\circ}}$5 to 4○. We find that the SMC’s metallicity gradient is radially asymmetric. It is flatter towards the east than to the west, hinting at mixing and/or distortion of the spatial metallicity distribution (within the inner 3○), presumably caused by tidal interactions between the Magellanic Clouds.

We study the morphology of the stellar periphery of the Magellanic Clouds in search of substructure using near-infrared imaging data from the Visible and Infrared Survey Telescope for Astronomy Hemisphere Survey. Based on the selection of different stellar populations using the (J − Ks, Ks) colour–magnitude diagram, we confirm the presence of substructures related to the interaction history of the Clouds and find new substructures on the eastern side of the LMC disc, which may be owing to the influence of the Milky Way, and on the northern side of the SMC, which is probably associated with the ellipsoidal structure of the galaxy. We also study the luminosity function of red clump stars in the SMC and confirm the presence of a bi-modal distance distribution, in the form of a foreground population. We find that this bi-modality is still detectable in the eastern regions of the galaxy out to a 10○ distance from its centre. Additionally, a background structure is detected in the North between 7○ and 10○ from the centre that might belong to the Counter Bridge, and a foreground structure is detected in the South between 6○ and 8○ from the centre that might be linked to the Old Bridge.

Core-collapse supernovae (SNe) are the inevitable fate of most massive stars. Since most stars form in groups, SN progenitors can be constrained with information of their environments. It remains challenging to accurately analyse the various components in the environment and to correctly identify their relationships with the SN progenitors. Using a combined dataset of VLT/MUSE spatially-resolved integral-field-unit (IFU) spectroscopy and HST/ACS+WFC3 high-spatial resolution imaging, we present a detailed investigation of the environment of the Type II-P SN 2004dg and Type IIb SN 2012P. The two SNe occurred in a spiral arm of NGC 5806, where a star-forming complex is apparent with a giant H II region. By modelling the ionised gas, a compact star cluster and the resolved stars, we derive the ages and extinctions of stellar populations in the vicinity of the SNe. The various components are consistent with a sequence of triggered star formation as the spiral density wave swept through their positions. For SNe 2004dg and 2012P, we identify their host stellar populations and derive initial masses of $10.0^{+0.3}_{-0.2}~M_\odot$ and $15.2^{+2.0}_{-1.0}~M_\odot$ for their progenitors, respectively. Both results are consistent with those from pre-explosion images or nebular-phase spectroscopy. SN 2012P is spatially coincident but less likely to be coeval with the star-forming complex. As in this case, star formation bursts on small scales may appear correlated if they are controlled by any physical processes on larger scales; this may lead to a high probability of chance alignment between older SN progenitors and younger stellar populations.

We derive the spatially resolved star formation history (SFH) for a 96 deg(2) area across the main body of the Large Magellanic Cloud (LMC), using the near-infrared photometry from the VISTA survey of the Magellanic Clouds (VMC). The data and analyses are characterized by a great degree of homogeneity and a low sensitivity to the interstellar extinction. 756 subregions of size 0.125 deg(2) - corresponding to projected sizes of about in the LMC - are analysed. The resulting SFH maps, with typical resolution of 0.2-0.3 dex in logarithm of age, reveal main features in the LMC disc at different ages: the patchy star formation at recent ages, the concentration of star formation on three spiral arms and on the Bar up to ages of similar to 1.6 Gyr, and the wider and smoother distribution of older populations. The period of most intense star formation occurred roughly between 4 and 0.5 Gyr ago, at rates of . We compare young and old star formation rates with the observed numbers of RR Lyrae and Cepheids. We also derive a mean extinction and mean distance for every subregion, and the plane that best describes the spatial distribution of the mean distances. Our results cover an area about 50 percent larger than the classical SFH maps derived from optical data. Main differences with respect to those maps are lower star formation rates at young ages, and a main peak of star formation being identified at ages slightly younger than 1 Gyr.

Studies of young stellar objects (YSOs) in the Galaxy have found that a significant fraction exhibits photometric variability. However, no systematic investigation has been conducted on the variability of extragalactic YSOs. Here we present the first variability study of massive YSOs in an similar to 1.5 deg(2) region of the Large Magellanic Cloud (LMC). The aim is to investigate whether the different environmental conditions in the metal-poor LMC (similar to 0.4-0.5 Z(circle dot)) have an impact on the variability characteristics. Multi-epoch near-infrared (NIR) photometry was obtained from the VISTA Survey of the Magellanic Clouds (VMC) and our own monitoring campaign using the VISTA telescope. By applying a reduced chi(2)-analysis, stellar variability was identified. We found 3062 candidate variable stars from a population of 362 425 stars detected. Based on several Spitzer studies, we compiled a sample of high-reliability massive YSOs: a total of 173 massive YSOs have NIR counterparts (down to K-s similar to 18.5 mag) in the VMC catalogue, of which 39 display significant (>3 sigma) variability. They have been classified as eruptive, fader, dipper, short-term variable, and long-period variable YSOs based mostly on the appearance of their K-s-band light curves. The majority of YSOs are aperiodic; only five YSOs exhibit periodic light curves. The observed amplitudes are comparable or smaller than those for Galactic YSOs (only two Magellanic YSOs exhibit Delta K-s > 1 mag), not what would have been expected from the typically larger mass accretion rates observed in the Magellanic Clouds.