Electron-capture supernovae (ECSNe) may arise from ONeMg-core collapse in super-asymptotic giant branch (sAGB) stars near the low-mass core-collapse limit (approximate to 8-10 M circle dot). At early times, models predict that ECSNe resemble low-mass red supergiant iron-core-collapse SNe, making the two channels difficult to distinguish. Nebular spectroscopy, however, can reveal differences in ejecta composition. We present a systematic sample of 19 nebular spectra of low-luminosity Type IIP (LLIIP) SNe from the Zwicky Transient Facility Census of the Local Universe survey, obtained 115-450 days after explosion. Their low velocities expose narrow lines blended in brighter SNe, which we identify and model to constrain progenitor properties. We find a strong correlation between the FWHM of H i lambda 6563 and peak luminosity, showing that LLIIP SNe occupy the low-energy end of the core-collapse population, but no correlation with plateau duration, suggesting that envelope and core properties are not tightly linked. Only one SN reaches the extremely low H i lambda 6563 widths predicted for the weakest similar to 9 M circle dot explosion models, implying that such low-energy events are intrinsically rare. Combining our sample with 118 literature nebular spectra of Type II SNe, we infer an IMF slope of 2.1 +/- 1.2. We also introduce an "ECSN score" based on the absence of He- and O-shell emission lines, and identify two plausible ECSN candidates, SN 2023bvj and SN 2024btj. However, neither shows the extremely narrow nebular lines predicted by current ECSN models. If ECSNe arise predominantly through the LLIIP channel, we infer an upper limit on the ECSN rate of less than or similar to(5-8) & times; 102 Gpc-3 yr-1, corresponding to a narrow sAGB progenitor mass window of Delta MsAGB less than or similar to 0.02-0.06 M circle dot.

Son Of X-Shooter (SOXS) is a spectrograph for the European Southern Observatory (ESO), recently installed at the New Technology Telescope at the La Silla Observatory, Chile. The main instrument goal consists of the characterization of transient sources, based on alerts. It covers from (partially) ultraviolet to visible and near-infrared bands, with a spectral resolution of R similar to 4500, using two separate, wavelength-optimized spectrographs. A scientific-grade visible camera, primarily intended for target acquisition, also provides a "light imaging" mode. We present the design of the SOXS Instrument Control Software, which is in charge of controlling all motors, calibration lamps, and detectors; monitoring sensors and components' status; coordinating the execution of exposures; and implementing all observation, calibration, and maintenance procedures. Given the extensive experience of the SOXS consortium in the development of instruments for the ESO Very Large Telescope, we decided to base the design of the control system on the same standards, both for hardware and software control. We illustrate the control network, the instrument functions and detectors to be controlled, the overall design of the SOXS Instrument Software and its main components. Then, we provide details about the control software for the most SOXS-specific components and peculiar features: the piezoelectric tip-tilt corrector used for active compensation of mechanical flexures of the instrument, the cryogenic piezoelectric slit exchanger for the near-infrared spectrograph, the co-rotator monitoring system, and the control of the commercial-off-the-shelf-based imaging camera.

We present multiwavelength observations and analysis of six luminous fast blue optical transients (LFBOTs) discovered in Zwicky Transient Facility (ZTF) survey data. We identified these LFBOTs from their fast light-curve evolution (t_1/2≤ 12d), blue colors at peak brightness (g-r≤-0.5mag), a visible host galaxy, high optical luminosity (M_g<-20), and an X-ray or radio detection. With the exception of AT2024aehp (ZTF24abygbss), these transients exhibit peaks in their 10GHz radio light curves at t_rest≈ 50-100 d, with peak radio luminosities ranging from 10^38-10^40 erg s^-1. Modeling the radio emission as synchrotron radiation indicates a fast (v=0.1-0.3c) shock in a dense (n_e≈10^3-10^4 cm^-3) medium. The X-ray emission varies by ≈2 orders of magnitude in luminosity (10^42-10^44 erg s^-1) at t_rest∼20d. Analysis of the host-galaxy photometry and spectroscopy for each transient shows that they are predominantly nonnuclear (a few kpc offset) with star-forming host galaxies of stellar masses 10^9-10^11 ,M_⊙. Unlike all other LFBOTs to date, AT2024aehp exhibited a luminous (M<-19mag) plateau in the optical light curve; spectra during this plateau phase showed a featureless blue continuum. The 6-15 GHz radio emission of AT2024aehp brightened by over an order of magnitude from t_rest≈70d to t_rest≈130d. The mostly consistent radio behavior between optically selected LFBOTs implies a similar circumburst medium, leading us to prefer a progenitor scenario in which mass is lost in a consistent way shortly prior to the terminal event, such as a massive star merging with a compact object.

Most massive stars live in binary systems. When the first supernova (SN) in a binary occurs, the ejecta hit the companion, which may inflate as a consequence, and then interacts with the newly formed compact object. The recent Type Ic SN2022jli shows a periodic modulation in its emission, which is interpreted as evidence for such interaction. We derive predictions for the occurrence rate and observables of SNe exhibiting these companion - compact-object interactions (CCIs). We analyze a comprehensive, state-of-the-art grid of detailed binary stellar evolution models, and implement analytic prescriptions for the expansion of the companion star following its interaction with the SN ejecta. We employ the newly developed population synthesis code SN-ORACLE to derive the distribution functions of the properties of the SNe affected by CCI and their companions, where we use different explodability and neutron star birth kick distributions. We find that periodic CCI is expected to occur in more than half of the binary systems that produce a hydrogen-poor core collapse SN and are not disrupted, while the occurrence rate in systems producing hydrogen-rich SNe is small. We find broad period ranges, peaking around 20-50 days, with the interaction lasting for 0.5-10 years. We identify specific binary evolution models that reproduce the observed period of the light curve undulations of SN2022jli, SN2015ap, and SN2022esa. The inflation of the companion also increases its luminosity and brightness, increasing its detectability with current instruments. For SN2022jli, our best fitting models predict a J-band magnitude of 21-23 for up to 10 years. We find that up to 27

Type Ia Supernovae (SNe Ia) are well known for their role as standardizable cosmological candles. Their uniformity is credited to their single origin as thermonuclear explosions of White dwarf (WD) stars. Nevertheless, some SNe Ia break this regularity. Prominently, the Iax subclass are less energetic and remarkably diverse, raising questions about their progenitor systems. While no progenitor system of a normal SN Ia has ever been detected, a luminous blue star was identified in pre-explosion images of the site of the bright SN Iax SN 2012Z, suggested to be a helium giant companion star acting as a mass donor to a WD SN progenitor. This is in line with models of weak mass accretion of a WD from a binary companion, producing an explosion that does not fully disrupt the star. However, these models fail to explain the properties of the faintest Type Iax explosions, suggesting either they originate from other WD binary systems, or even from massive progenitor stars. Here, we present the faint SN Iax SN 2024vjm - possibly the faintest supernova observed to date. Using a deep pre-explosion image taken by the recently launched Euclid space mission, we show that its progenitor system must be fainter than the helium giant SN Iax progenitor candidate of SN 2012Z, as well as that of the luminous red companion or remnant of the faint SN 2008ha, and may require a subdwarf helium star as a mass donor. The deep image also provides strong arguments against a massive star origin for this faint supernova. Our observations argue that SN 2024vjm is a WD explosion, but we find that remarkably faint SNe Iax fade more slowly than bright ones, i.e., they evolve in an opposite manner from the famous Phillips relation that makes regular SNe Ia cosmological candles.

Mapping how the explosion properties of Type II supernovae (SNe II) relate to the properties of their progenitors can provide strong constraints for understanding the final evolutionary stages of massive stars. Type IIP SNe, linked to the explosions of single red super-giant (RSG) stars, have recently been found to require some form of interaction with circumstellar material (CSM) to reproduce the rapid rise to the plateau often seen in their light curves. In this work, we present observations and analysis of the Type IIP SN 2020bij, characterized by a slow rise to its plateau as well as high expansion velocities. We identify four other SNe IIP from the literature (ASASSN-14kg, SN 2018fif, SN 2021yja and SN 2023axu) with similarly slowly rising light curves and find that they also show high expansion velocities. Using both analytical and numerical models, all five events can be explained with weak to no CSM interaction. We therefore propose that these events constitute a new subclass of Type IIP SNe which could be associated with relatively confined CSM. Early and dense photometric coverage of future SNe IIP together with early spectroscopic observations will further map this subclass and its physical properties. Understanding such rare events could be key to constraining the diversity of late-stage mass-loss in RSGs.

We present optical and near-infrared (NIR) observations of the fast-declining Type Ia supernova (SN Ia) 2022an. The photometric and spectroscopic properties identify it as a standard 91bg-like event; however, our data reveal a relatively narrow absorption feature with a full width at half-maximum (FWHM) of 75 & Aring; near 1.037 mu m in the rest frame of the observed spectra that persists from around 30 days to nearly 90 days after maximum light. We attribute this feature to the He i 1.083 mu m line with a blueshifted velocity of 1.3 & times; 104 km s-1 and a FWHM of 2.1 & times; 103 km s-1, supported by the detection of multiple optical He i transitions at earlier epochs with a higher velocity of around 1.5 & times; 104 km s-1. The high velocity of the helium cannot be explained by helium external to the progenitor at the time of explosion, such as stripped surface helium from a companion star. The properties of the helium absorption in the spectra of SN 2022an instead point to unburned material in the outer ejecta, thus providing the most compelling evidence to date for helium-bearing ejecta in a 91bg-like SN Ia. Such helium has been predicted in sub-Chandrasekhar-mass double-detonation explosions involving a surface helium shell. No theoretical calculations of modern helium-shell double detonations have been performed at epochs similar to those observed for SN 2022an to study the effects of helium on their spectra, revealing a gap between observations and theoretical calculations in our understanding of how helium manifests in SNe Ia. Nevertheless, the discovery of persistent helium absorption in SN 2022an demonstrates the diagnostic power of NIR spectroscopy for understanding thermonuclear supernova explosions by probing the abundance and structure of their ejecta.

We present the discovery and characterization of SN 2018erx (ZTF18abkmbpy), a fast-evolving, unusually red, interacting stripped-envelope supernova. Spectroscopically, SN 2018erx shows broad C2 emission with characteristic widths of ∼3800 km s^-1, consistent with interaction with carbon-rich circumstellar material and a Type Icn core-collapse SN classification. Photometrically, it evolves rapidly, rising from half-maximum to peak in 2.1 d and declining back in 3.1 d. Semi-analytical CSM-interaction modeling favors a compact, shell-like CSM with M_ CSM≈0.3 M_⊙, R_0≈0.7 AU, and a low ejecta mass of M_ ej≈0.11 M_⊙. The radioactive yield is also small, with M_ Ni≲(3–5)×10^-3 M_⊙, placing SN 2018erx at the low end of the H-poor distribution. At +29 d after peak, we detect a near-infrared excess consistent with pre-existing local circumstellar dust, with M_ d∼10^-6–10^-5 M_⊙. Together, the rapid evolution, strong local reddening, carbon-rich emission, and dust point to a multi-component circumstellar environment: a dense inner interaction region from enhanced pre-SN mass loss and an outer dusty layer from an earlier mass-loss episode roughly 10–200 yr before core collapse. These properties favor an ultra-stripped core-collapse explosion of a low-mass He star in a binary system, with fallback-modified Wolf–Rayet collapse or merger-driven mass loss remaining possible alternatives. SN 2018erx provides rare insight into the mass-loss history of stripped-envelope SNe and suggests that dust-enshrouded explosions of this kind may be underrepresented in optical surveys.

Hydrogen-rich superluminous supernovae without narrow emission lines (SLSNe-II) are rare transients whose powering mechanisms remain debated, particularly the role of circumstellar medium (CSM) interaction. We present photometric and spectroscopic observations of SN 2019cqc to investigate its power source and progenitor mass loss. We model the lightcurve using MOSFiT with the csm and csmni models to constrain the explosion and CSM parameters. SN 2019cqc peaked at M_g = -20.21 ± 0.07 and emitted ∼ 1.7 × 10^50 erg of energy in the form of radiation. Photometric and spectroscopic modeling indicates that CSM interaction dominates in both scenarios, with best-fit CSM and ejecta masses of ∼ 4.5 M_⊙ and ∼ 32 M_⊙, respectively. The inferred CSM properties imply an extreme eruptive mass loss at a rate of ∼ 0.2–0.3 M_⊙ yr^-1 in the years preceding the core collapse, consistent with a variable progenitor of luminous blue variable progenitor. We observe a persistent blueshifted asymmetry in the Hα emission line. At early times (≲ +110 d), this is attributed to electron scattering with bulk Velocity of ejecta, while the profile at late epochs (≳ +402 d onward) suggests the subsequent formation of dust in the ejecta. Additionally, we identify a distinct, short-lived feature at ∼ 4600 Å , likely a blend of ionized C III/N III lines powered by the interaction of the SN-shock with the extended atmosphere.

We present the discovery of AT 2024wpp ('Whippet'), a fast and luminous 18cow-like transient. At a redshift of z = 0 . 0868 , revealed by Keck Cosmic Web Imager spectroscopy of its faint star-forming host, it is the fourth-nearest example of its class to date. Rapid identification of the source in the Zwicky Transient Facility data stream permitted ultraviolet-through-optical observations to be obtained prior to peak, allowing the first determination of the peak bolometric luminosity ( 2 & times; 10(45 )erg s(-1)), maximum photospheric radius ( 10(15) cm), and total radiated energy ( 10(51) erg) of an 18cow-like object. We present results from a comprehensive multiwavelength observing campaign, including a far-ultraviolet spectrum from the Cosmic Origins Spectrograph on the Hubble Space Telescope and deep imaging extending > 100 d post-explosion from the Very Large Telescope, Hubble Space Telescope , Very Large Array, and Atacama Large Millimetre Array. We interpret the observations under a model in which a rapidly accreting central engine blows a fast (similar to 0.2 c ) wind into the surrounding medium and irradiates it with X-rays. The high Doppler velocities and intense ionization within this wind prevent identifiable spectroscopic features from appearing in the ejecta or in the surrounding circumstellar material. Weak H and He signatures do emerge in the spectra after 35 d in the form of double-peaked narrow lines. Each peak is individually narrow (full width Sv similar to 3000 km s(-1)) but the two components are separated by Delta v similar to 6600 km s(-1), indicating stable structures of denser material, possibly representing streams of tidal ejecta or an ablated companion star.

Understanding dust attenuation toward extragalactic transients is critical for recovering their intrinsic properties and probing the local environments of distant galaxies. A popular diagnostic is the Na I D absorption equivalent width widely applied to extragalactic transients. In this paper, we present early-time optical and near-infrared observations of the Type Ib supernova (SN) SN 2024vjc, followed for $\sim$130 days post-explosion. SN~2024vjc exhibits only weak Na~I~D absorption, indicating only a modest host attenuation with $E (B-V)_{\rm host} \sim 0.18$ mag; if this argument were applied, SN~2024vjc would be a peculiar, faint, and red SN Ib while showing the light-curve shape and spectral evolution broadly consistent with those of canonical SNe Ib. We show that this is not the case; SN-based diagnostics (intrinsic color templates, color-curve evolution, and spectral dereddening) together with the Balmer decrement indicate substantial attenuation, $E(B-V) \sim 0.45$ $-$ $0.8$\,mag. The weak Na I D absorption may result from photoionization of neutral sodium by the intense radiation field of a young H$_{2}$ region at the explosion site; this scenario is directly supported by the detection of narrow H$_α$, [N$_{2}$], and H$_β$ emission lines and a blue continuum excess in late-time spectroscopy. SN~2024vjc represents a clear counterexample to the commonly assumption that weak or absent Na I D absorption implies negligible host-galaxy attenuation, and highlights the importance of employing multiple, independent attenuation diagnostics.

SN 2025wny is a gravitationally lensed, hydrogen-poor superluminous supernova (SLSN-I) at z = 2.015. To date, it is the most extensively observed high-redshift core-collapse SN and has the most detailed rest-frame UV observations of any SLSN. We present densely sampled rest-frame UV-to-optical photometry and spectroscopy out to +80 d post-peak (rest frame) from several facilities, including JWST, Keck, VLT, Gemini, the Palomar 200-inch, the Fraunhofer Telescope at Wendelstein, and the Liverpool Telescope. Correcting for lensing magnification, SN 2025wny reaches a peak pseudo-bolometric luminosity of L_ peak≳4×10^44 erg s^-1 over rest-frame 1500-4230 Å, placing it within the luminosity range of typical SLSNe-I. SN 2025wny exhibits several unusual features, including a continuum excess and sharp spectral features in the FUV from +20-60 d that coincide with an FUV light-curve plateau and higher inferred blackbody temperatures. SN 2025wny's spectra also show little to no UV line blanketing, no obvious O II absorption despite high temperatures, and evidence for C II, Hα, and possible He I. Light-curve modeling suggests that SN 2025wny may require a hybrid or non-standard power source. This work provides some of the first detailed constraints on high-redshift SLSNe and establishes SN 2025wny as an essential spectral and photometric reference for identifying and interpreting high-redshift SLSNe discovered by Rubin and Roman.

Periodic luminosity modulations have been recently identified for the stripped-envelope supernovae SN 2022jli and SN 2022esa, motivating a systematic search for a similar behavior in a larger sample. Such modulations may indicate the explosions arise in binary progenitor systems. We perform the first systematic search for periodic modulation in a sample of 34 Type Ib/c supernovae with high quality photometry from the Zwicky Transient Facility. We develop and apply a statistically rigorous pipeline for detecting periodic modulation in light curves. The pipeline successfully recovers the previously reported periodic undulations of SN 2022jli and SN 2022esa, and identifies SN 2020sgf as an additional promising periodic candidate. Injection-recovery simulations are used to quantify the survey sensitivity as a function of period and modulation amplitude. Comparing the observed detections with recent population synthesis models shows that, under the adopted assumptions, models predicting intrinsic periodic fractions of order 20

The emission mechanism and host galaxy preference of optical/UV tidal disruption events (TDEs) are still not entirely understood. We present observations of the TDE AT 2022csn, which is one of the most distant (d_L 726 Mpc) and luminous (L_peak=2.487^(+0.073)_(-0.067)*10^(44) erg/s) optical/UV TDEs observed to date. Although it is a spectroscopically normal H+He TDE, it shows some photometric peculiarities, exhibiting a pronounced double-peaked light curve (with peaks separated by 18.30 pm 2.84 days in the g-band), and lying in the low-temperature and large-radius end of the optical/UV TDE population. The host galaxy of AT 2022csn shows evidence for a significant starburst within the last Gyr consistent with other optical/UV TDEs, but also narrow emission lines that place it within the Type II AGN region of the BPT diagram. Interaction between the TDE and a pre-existing AGN accretion disk might explain the peculiar photometric properties. However, it is puzzling that a TDE would be visible in a Type II AGN, where according to the AGN unification picture the central region around the supermassive black hole is obscured. We suggest a few scenarios to reconcile this. AT 2022csn together with AT 2019ahk, which shows similar properties, may belong to a new subset of low-temperature, high-radius TDEs in galaxies with Type II AGN emission features.

Context. The observational properties of core-collapse supernovae are shaped by the envelopes of their progenitors. In massive binary systems, mass-transfer drastically alters the pre-supernova structures compared to single stars, which leads to a diversity in supernova explosions. Aims. We computed the distribution of core-collapse supernova properties based on comprehensive detailed grids of single and binary stellar evolution models. Methods. We conducted a grid-based population synthesis to produce a synthetic population of core-collapse supernovae and compared it to observed supernova samples. To do this, we applied various explodability and merger criteria to our models. In line with earlier results, we identified interacting supernova progenitors as those stars that undergo core collapse during or shortly after a Roche-lobe overflow phase. Results. With an interacting binary fraction of 68%, our models predict that two-thirds of all core-collapse supernovae are Type IIP/L and one-third are Type Ibc. This agrees with recent volume-limited supernova surveys. We find that 76% of the Type Ibc supernova progenitors took part in a previous binary mass transfer (mostly as a mass donor), but 63% of the Type IIP/L supernova progenitors did this as well (mostly as mass gainers). This yields a much broader envelope mass distribution than expected from single stars. Mass-transfer-induced interacting supernovae make up similar to 5% of all core-collapse supernovae, which is close to the observed fractions of Type IIn and Type Ibn supernovae. When a disk or toroidal geometry of the circumstellar medium is assumed for Type IIn supernovae, our models predict a bimodal distribution of the radiated energies that is similar to the distribution deduced from observations. Conclusions. While we found the effect of binary evolution on the relative number of Type Ibc and Type IIP/L supernovae to be moderate, it leads to lower average ejecta masses in Type Ibc and Type IIb supernovae and can lead to higher pre-supernova masses in Type IIP/L supernovae than in single stars. Binary models are also able to reproduce the number and properties of interacting supernovae.

Context. The observational properties of core-collapse supernovae are shaped by the envelopes of their progenitors. In massive binary systems, mass-transfer drastically alters the pre-supernova structures compared to single stars, which leads to a diversity in supernova explosions. Aims. We computed the distribution of core-collapse supernova properties based on comprehensive detailed grids of single and binary stellar evolution models. Methods. We conducted a grid-based population synthesis to produce a synthetic population of core-collapse supernovae and compared it to observed supernova samples. To do this, we applied various explodability and merger criteria to our models. In line with earlier results, we identified interacting supernova progenitors as those stars that undergo core collapse during or shortly after a Roche-lobe overflow phase. Results. With an interacting binary fraction of 68%, our models predict that two-thirds of all core-collapse supernovae are Type IIP/L and one-third are Type Ibc. This agrees with recent volume-limited supernova surveys. We find that 76% of the Type Ibc supernova progenitors took part in a previous binary mass transfer (mostly as a mass donor), but 63% of the Type IIP/L supernova progenitors did this as well (mostly as mass gainers). This yields a much broader envelope mass distribution than expected from single stars. Mass-transfer-induced interacting supernovae make up ∼5% of all core-collapse supernovae, which is close to the observed fractions of Type IIn and Type Ibn supernovae. When a disk or toroidal geometry of the circumstellar medium is assumed for Type IIn supernovae, our models predict a bimodal distribution of the radiated energies that is similar to the distribution deduced from observations. Conclusions. While we found the effect of binary evolution on the relative number of Type Ibc and Type IIP/L supernovae to be moderate, it leads to lower average ejecta masses in Type Ibc and Type IIb supernovae and can lead to higher pre-supernova masses in Type IIP/L supernovae than in single stars. Binary models are also able to reproduce the number and properties of interacting supernovae.