arXiv subjects

Daichi Tsuna

Publications and source records attributed to Daichi Tsuna.

At least 19 recordsLinked to original sources

arXiv2026

Explaining the X-ray Precursor, Ultra-long Prompt Emission, and Week-long Decay of GRB250702B with a Jetted Micro-TDE

The longest detected gamma-ray burst, GRB250702B, exhibited seven hours of prompt $\gamma$-ray emission, preceded by a soft X-ray precursor ($\sim1$ day earlier) and followed by a weeks-long fading X-ray tail. Lacking an established progenitor for all three phases, we propose that this ultra-long GRB (ULGRB) is powered by a jetted micro-tidal disruption event (micro-TDE), in which a spinning stellar-mass black hole (BH) disrupts a Sun-like star and launches a relativistic jet via the Blandford-Znajek mechanism. Micro-TDE debris disks have hours-to-days viscous timescales, naturally explaining ULGRB durations. Using 3D hydrodynamic AREPO simulations of a $1\,M_\odot$ star disrupted by a $10\,M_\odot$ BH, we show that within $\sim1$ day the debris forms a quasi-steady envelope with a low-density polar funnel ($\rho\propto r^{-2}$, half-opening angle $\approx15^\circ$). Applying an analytic jet-stability framework to these profiles, we find that the $r^{-2}$ funnel keeps the jet below the kink-instability threshold, enabling stable propagation and breakout for jet powers, $L_{\rm jet}\gtrsim10^{47}$ erg s$^{-1}$. We attribute the X-ray precursor to pre-disk stream-fed accretion; the prompt GRB to a tightly beamed jet ($\theta_{\rm b}\lesssim1^\circ$, $L_{\gamma,\rm iso}\sim10^{51}$ erg s$^{-1}$) escaping the funnel, launched by a rapidly spinning BH ($a_\bullet\sim0.9$); and the weeks-long X-ray decline to disk-wind mass loss ($L_{\rm jet}\propto t^{-2}$) combined with jet widening ($\theta_{\rm b}\propto t$, initially steepening the decay to $L_{\rm X,iso}\propto L_{\rm jet}/\theta_{\rm b}^{2}\propto t^{-4}$). Our model reproduces the multi-phase evolution of GRB250702B and establishes jetted micro-TDEs as a physically motivated ULGRB engine.

astro-ph.HE↗

arXiv2026

No Surviving Companion to the Galactic SN 1181: Evidence for a Double-Degenerate Channel for Type Iax Supernovae

Type Iax supernovae (SNe Iax) are the recently-established, yet peculiar subclass of thermonuclear supernovae, whose progenitor systems and explosion mechanisms remain debated. A leading scenario is a single-degenerate channel, in which a white dwarf accreting from a He-star companion undergoes a pure deflagration, leaving both a bound remnant and surviving companion. The Galactic SN 1181, whose distinctive properties are consistent with an SN Iax involving a weak explosion and bound white dwarf remnant, offers a unique opportunity to test this scenario. Here, we perform a deep search for a surviving He-star companion, a hallmark of the single-degenerate He-donor channel, within $30^{\prime\prime}$ ($\sim 0.3$ pc) of the remnant using archival Gaia and Pan-STARRS1 data. The parallaxes and proper motions exclude all Gaia sources, while the spectral energy distributions of the remaining Pan-STARRS1 sources are inconsistent with both the He-star spectral templates and known hot-subdwarf population. Binary evolution calculations predict a minimum mass of a companion with an absolute $g$-band magnitude of $M_{g} \lesssim 6.5$ mag, much brighter than the Pan-STARRS1 detection limit of $M_{g} > 8$ mag. Our non-detection rules out He-star and luminous hydrogen-rich companions for SN 1181, favoring a double-degenerate channel (i.e., a white dwarf merger). Adding to the luminous He-star companion identified in the pre-explosion imaging of SN 2012Z, our results provide direct evidence for multiple progenitor channels leading to SNe Iax.

astro-ph.HE↗

arXiv2026

Semi-analytical Light Curve Model for Transients Preceding Binary Mergers. I: Supernova Precursor Emission from Compact Object Companions

A binary undergoing dynamically unstable mass transfer could rapidly shrink its orbit and lead to a merger, with the whole process often observable in human timescales. We construct a semi-analytical light curve model of binary systems composed of a star and a compact object accretor, that would display long-rising accretion-powered emission prior to a final merger-driven explosion. We apply the model to the precursors of interacting supernovae (SNe) that display long-rising light curves of years, SN 2023zkd, 2023fyq and 2021qqp, demonstrating the model's capability of inferring the mass-transfer history and constraining the progenitor binary system. The model and the parameter inference framework, encapsulated in a publicly-released script, can be applied to existing long-rising precursors of SNe as well as many SN precursors to be discovered by surveys like those from the Vera C. Rubin Observatory.

astro-ph.HE↗

arXiv2026

Formation of rotating supergiants via stellar mergers in dense clusters: Implications for black hole natal spins

We investigate how massive stellar mergers in young star clusters imprint on black hole spin distributions and the broader implications for gravitational wave sources. The central hypothesis is that angular momentum transferred during stellar mergers substantially affects the spins of the merger products and resulting black holes, with some merger products evolving into collapsar-like objects that retain thick accretion disks that enable efficient spin up. This is in contrast to the more general expectation that black holes form with very small spins, having shed most of their envelope angular momentum via winds and expansion before core collapse. Using roughly 150 N-body models generated with the $\texttt{Cluster Monte Carlo}$ code, $\texttt{CMC}$, we analyze stellar mergers that lead to black hole formation, prioritizing ``significant'' events with mass ratio $q>0.1$. After identifying optimal candidates from our $\texttt{CMC}$ models, we explore detailed stellar structure and post-merger evolution implications with MESA stellar evolution models to capture angular momentum injection and pre-collapse profiles most relevant for the BH natal spin. In our current dataset representative of Milky Way-like globular clusters, up to roughly half of black holes are formed from such mergers, including up to roughly $10\%$ from significant mergers with $q>0.1$. Preliminary angular momentum estimates indicate substantial spin-up during the merger, and trends with mass ratio and stellar properties suggest strong correlations with the final black hole spin. In some cases, dimensionless spin parameters of $a\simeq 0.5$ or more are expected. This process has important implications for the dynamical formation and retention of gravitational wave sources in clusters.

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arXiv2026

Old and Bright: The Remarkable Radio Brightening of the Engine-driven SN 2012au Several Years After Explosion Signals the Birth of a PWN

We present the results from an extensive broad-band (radio to X-rays) observing campaign of the engine-driven Type Ib SN 2012au in the first 13 years of evolution. The early-time (${\delta}t\leq{190}$ d) radio and X-ray evolution is well-described by conventional models of a forward shock interacting with a wind-like circumstellar medium ($\rho_{\rm{CSM}}\propto{r}^{-2}$). However, starting at $\delta{t}\approx{6.7}$ yr, we detect a significant radio re-brightening. This late-time emission is dominated by a luminous component characterized by a broad and rapidly evolving spectral peak and a shallow optically thin spectral slope, $F_{\nu}\propto{\nu}^{-0.31\pm0.02}$. These properties imply a compact emitting region ($R\lesssim{10}^{16}$ cm) expanding at a remarkably slow velocity ($\lesssim{500}$ km/s) into a high-density environment ($\geq{10}^4 \rm{cm}^{-3}$), accompanied by a hard electron power-law index $p\approx{1.6}$. No soft or hard X-ray emission is detected at any epoch, indicating that high-energy radiation is either strongly absorbed or intrinsically absent. In the context of aspherical shock-CSM interaction models, these observations imply extreme properties of the CSM (geometry, density, total mass) that lack clear astrophysical motivation. Instead, we show that the emergence of radiation from a newborn Pulsar Wind Nebula (PWN) naturally explains the radio spectral evolution and high-energy limits, where the emission is governed by the adiabatic expansion of a relic pair plasma. We conclude that SN 2012au represents the most compelling candidate for a young, newborn PWN discovered to date, a scenario that can be directly tested with pending Very Long Baseline Interferometry (VLBI) observations.

astro-ph.HE↗

arXiv2026

SN~2018erx: A fast-evolving, dust-reddened Type Icn supernova with broad C II emission lines

We present the discovery and characterization of SN~2018erx (ZTF18abkmbpy), a fast-evolving, unusually red, interacting stripped-envelope supernova. Spectroscopically, SN~2018erx shows broad \ion{C}{2} emission with characteristic widths of $\sim\!3800$~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 $M_{\rm CSM}\approx0.3\,M_\odot$, $R_0\approx0.7$~AU, and a low ejecta mass of $M_{\rm ej}\approx0.11\,M_\odot$. The radioactive yield is also small, with $M_{\rm Ni}\lesssim(3$--$5)\times10^{-3}\,M_\odot$, 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 $M_{\rm d}\sim10^{-6}$--$10^{-5}\,M_\odot$. 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.

astro-ph.HE↗

arXiv2026

The pair-instability origin of supernova 2023vbw

Stars in the initial and carbon-oxygen core mass ranges of $\sim140-260$ and $50-130$ M$_\odot$, respectively, with low metallicity are predicted to experience copious electron-positron pair production in their cores, leading to a runaway thermonuclear explosion that obliterates the entire star in a luminous and long-duration pair-instability supernova explosion. Some previous supernovae have been interpreted in this context but lack the full range of predicted properties. Here, we report detailed observations and modeling of the hydrogen-rich supernova 2023vbw, which exploded in a low-metallicity ($\sim0.1$ Z$_\odot$) environment in a dwarf star-forming galaxy at a redshift of $0.088$. Its light curve exhibits a luminous ($1.6\times10^{43}$ erg s$^{-1}$) and long-duration ($190$ days) main peak, resulting in a total radiated energy of $3\times10^{50}$ erg, more than an order of magnitude greater than canonical core-collapse supernovae. Semi-analytical light-curve modeling yields a blue supergiant-like progenitor with an ejecta mass of $170-350$ M$_\odot$, radioactive nickel mass of $1.2-1.6$ M$_\odot$, and explosion energy of $(6-13)\times10^{52}$ erg, well matched by pair-instability models. The early and late-phase light curve and spectra also show evidence for interaction of the supernova ejecta with an aspherical circumstellar medium. Discoveries of numerous such events with the upcoming Rubin Observatory and Roman Space Telescope will shed light on the deaths of the most massive stars in the Universe.

astro-ph.HE↗

arXiv2026

UV and Optical Signatures of Late-time Disk Instabilities in Tidal Disruption Events

Tidal disruption events (TDEs) are unique probes of evolving accretion in supermassive black holes. Recent models of TDE disks show that they undergo brief thermal instabilities with temporal super-Eddington accretion at late times, which has been suggested as a possibility to explain the ubiquitous late radio emergence in TDEs. We model the ultraviolet (UV) and optical signatures of such disk instabilities, expected from the accretion power being reprocessed by the optically-thick outflow following super-Eddington accretion. Our model predicts brief UV-bright transients lasting for days, with luminosities of $10^{42}$-$10^{43}$ erg s$^{-1}$ in near-UV and $10^{41}$-$10^{42}$ erg s$^{-1}$ in optical for a typical TDE by a $10^6~M_\odot$ black hole. These could be detectable by near-future surveys such as ULTRASAT, Vera C. Rubin Observatory and Argus Array, for TDEs of redshifts out to $\approx 0.1$. We further conduct a search for these transients in existing nearby TDEs using data from the Zwicky Transient Facility, placing upper limits on the flare rate for each TDE of $1$-$2$ yr$^{-1}$ dependent on the outflow mass. In the era of future surveys, combined UV/optical and radio monitoring would be an important test to the disk instability phenomena, as well as its explanation for the late-time radio emission in TDEs.

astro-ph.HE↗

arXiv2025

Delayed radio emission in tidal disruption events from collisions of outflows driven by disk instabilities

Delayed radio emission has been associated with a growing proportion of tidal disruption events (TDEs). For many events, the radio synchrotron emission is inferred to originate from the interaction of mildly-relativistic outflows, launched with delay times of $\sim 100$--$1000$ d after the TDE optical peak. The mechanism behind these outflows remains uncertain, but may relate to instabilities or state transitions in the accretion disk formed from the TDE. We model the radio emission powered by the collision of mass outflows ("flares") from TDE accretion disks, considering scenarios in which two successive disk flares collide with each other, as well as collisions between the outflow and the circumnuclear medium (CNM). For flare masses of $\sim 0.01$-$0.1 M_{\odot}$, varied CNM densities, and different time intervals between ejected flares, we demonstrate that the shocks formed by the collisions have velocities $0.05c$-$0.3c$ at $\sim 10^{17}$ cm and power bright radio emission of $L_{\nu} \sim 10^{27}$-$10^{30}$ erg s$^{-1}$ Hz$^{-1}$, consistent with the properties inferred for observed events. We quantify how the typical peak timescale and flux varies for different properties of our models, and compare our model predictions to a selection of TDEs with delayed radio emission. Our models successfully reproduce the light curves and SEDs for several events, supporting the idea that delayed outflows from disk instabilities and state transitions can power late-time radio emission in TDEs.

astro-ph.HE↗

arXiv2025

Spectral Diversity in Type Ibn Supernovae and the Large Host Offset of SN2024acyl

In this paper, we first present observations of SN~2024acyl, a normal Type Ibn supernova with a large projected offset ($\sim$35~kpc) from its host galaxy. The low star-formation rate measured at the explosion site raises the possibility that the progenitor of SN~2024acyl may not have been a massive star. We then examine, more broadly, the spectral diversity of Type Ibn supernovae around 20--35 days after peak brightness and identify two distinct groups: Group I, which shows bluer rest-frame optical color and narrower He~I emission lines; and Group II, which shows redder rest-frame optical color and broader He~I lines. Group~I also tends to show higher peak luminosities. The diversity we identify appears to be closely connected to the diversity observed around peak and to persist into late phases ($>80$ days after peak). Given its redder color and broader He~I lines, we classify SN~2024acyl as belonging to Group II. Based on the current dataset, we find no clear connection between this spectral diversity and either the host environments of Type Ibn SNe or their pre-explosion activity. The observed diversity in Type Ibn SNe likely reflects differences in circumstellar material properties and/or explosion energetics. These differences could result from a range of progenitor properties, such as different helium star mass, orbital period and companion type if they are in binary systems, and may indicate fundamentally diverse progenitors. Whether a continuous distribution exists between the two groups remains to be determined and will require further data to explore.

astro-ph.HE↗

arXiv2025

The first radio view of a type Ibn supernova in SN 2023fyq: Understanding the mass-loss history in the last decade before the explosion

Supernovae that interact with hydrogen-poor, helium-rich circumstellar material (CSM), known as Type Ibn supernovae (SNe Ibn), present a unique opportunity to probe mass-loss processes in massive stars. In this work, we report the first radio detection of a SN Ibn, SN 2023fyq, and characterize the mass-loss history of its stellar progenitor using the radio and X-ray observations obtained over 18 months post-explosion. We find that the radio emission from 58--185 days is best modeled by synchrotron radiation attenuated by free-free absorption from a CSM of density $\sim$ $10^{-18}$ g/$\rm{cm^{3}}$ ($\sim 10^{6} \mathrm{\rho_{ISM}}$) at a radius of $10^{16}$ cm, corresponding to a mass-loss rate of $\sim$ $4 \times 10^{-3} \ \mathrm{M_{\odot} \ yr^{-1}}$ (for a wind velocity of 1700 km/s from optical spectroscopy) from 0.7 to 3 years before the explosion. This timescale is consistent with the time frame over which pre-explosion optical outbursts were observed. However, our late-time observations at 525 days post-explosion yield non-detections, and the 3$\sigma$ upper limits (along with an X-ray non-detection) allow us to infer lower-density CSM at $2\times 10^{16}$ cm with $\rm{\dot{M}}$ $< 2.5\times 10^{-3} \ \mathrm{M_{\odot} \ yr^{-1}}$. These results suggest a shell-like CSM from at most $4 \times 10^{15}$ to $2 \times 10^{16}$ cm ($\sim 10^{5} R_{\rm{\odot}}$) with an elevated CSM density (0.004 $\mathrm{M_{\odot} \ yr^{-1}}$) that is roughly consistent with predictions from a merger model for this object. Future radio observations of a larger sample of SNe Ibn will provide key details on the extent and density of their helium-rich CSM.

astro-ph.HE↗

arXiv2025

The Most Luminous Known Fast Blue Optical Transient AT 2024wpp: Unprecedented Evolution and Properties in the X-rays and Radio

We present X-ray (0.3--79 keV) and radio (0.25--203 GHz) observations of the most luminous Fast Blue Optical Transient (LFBOT) AT\,2024wpp at $z=0.0868$, spanning 2--280 days after first light. AT 2024wpp shows luminous ($L_{\rm X} \approx 1.5 \times 10^{43}\, \rm erg\,s^{-1}$), variable X-ray emission with a Compton hump peaking at $\delta t \approx 50$ days. The X-ray spectrum evolves from a soft ($F_{\nu} \propto \nu^{-0.6}$) to an extremely hard state ($F_{\nu} \propto \nu^{1.26}$) accompanied by a re-brightening at $\delta t \approx 50$\,days. The X-ray emission properties favor an embedded high-energy source shining through asymmetric expanding ejecta. We detect radio emission peaking at $L_{\rm 9\,GHz} \approx 1.7 \times 10^{29}\,\rm erg\,s^{-1}\,Hz^{-1}$ at $\delta t \approx 73$ days. The spectral evolution is unprecedented: the early millimeter fluxes rise nearly an order of magnitude during $\delta t \approx 17-32$ days followed by a decline in spectral peak fluxes. We model the radio emission as synchrotron radiation from an expanding blast wave interacting with a dense environment ($\dot{M} \sim 10^{-3}\, \rm M_{\odot}\,yr^{-1}$ for $v_{\rm w} = 1000\,\rm km\,s^{-1}$). The inferred outflow velocities increase from $\Gamma \beta c \approx 0.07\, \rm to\,0.42c$ during $\delta t \approx 32-73$ days, indicating an accelerating blast-wave. We interpret these observations as a shock propagating through a dense shell of radius $\approx 10^{16}$\,cm, then accelerating into a steep density profile $\rho_{\rm CSM}(r) \propto r^{-3.1}$. All radio-bright LFBOTs exhibit similar circumstellar medium (CSM) density profiles ($\rho_{\rm CSM} \propto r^{-3}$), suggesting similar progenitor processes. The X-ray and radio properties favor a progenitor involving super-Eddington accretion onto a compact object launching mildly-relativistic disk-wind outflows.

astro-ph.HE↗

arXiv2025

Fates of Rotating Supergiants from Stellar Mergers and the Landscape of Transients upon Core-collapse

We present a grid of rotating supergiant models from post-main sequence binary merger products, constructed by the MESA stellar evolution code. We focus on the evolution of these stars until core-collapse, in addition to their rotation, which could influence their mass loss and explosion phenomenology. We find that (i) as in previous studies, larger mass gain by merger favors the production of blue supergiants (BSGs) over red supergiants, and (ii) merger products that end as BSGs at core collapse have rotating outer envelopes, with lower-mass BSGs having faster envelope rotation due to less wind mass loss. We model the expected transients from these BSGs upon core-collapse, considering cases where the neutrino-driven explosion is successful and unsuccessful. The successful explosions result in supernovae (SNe) with long-rising light curves of morphology similar to SN 1987A. Failed explosions of these BSGs result in envelope fallback of $\sim (0.1$- several) $~M_\odot$ over $10^3$-$10^5$ seconds that power strong ($10^{51}$-$10^{53}$ erg) accretion-driven outflows in winds and possibly jets, with relativistic jets (if formed) generally capable of breaking out of the BSG envelope. Our modeling points to these merger-origin BSGs as viable progenitors for SN 1987A-like SNe, ultra-long gamma-ray bursts, and some of the fast luminous transients found in high-cadence optical surveys.

astro-ph.HE↗

arXiv2025

Luminous Late-time Radio Emission from Supernovae Interacting with Circumbinary Material

Numerous core-collapse supernovae (CCSNe) exhibit signatures of interaction with circumstellar material (CSM). Bright radio emission years after the SN is one such indication of dense CSM at large distances from the star, which may be generated via binary interactions. In this work, we use forward modeling to study the radio emission produced by interaction between the SN ejecta and CSM formed by non-conservative stable mass transfer from stripped-envelope stars in short-period binaries. The donors are among the likely progenitors of hydrogen-poor CCSNe that significantly expand $10^3$-$10^4$ years before core-collapse, with companions that best represent low-mass compact objects. We identify that non-conservative stable mass transfer from lower-mass stripped stars can create a detached shell-like CSM, whereas for our higher-mass stars the CSM is wind-like. In our models, mass transfer rates of $\sim 10^{-4} M_\odot$ $\mathrm{yr}^{-1}$ lead to dense CSM extending to $\sim 10^{18}$ $\mathrm{cm}$. The predicted radio emission is luminous at late times, reaching $L_{\nu}\sim10^{26}$-$10^{29}\mathrm{erg}$ $\mathrm{s}^{-1}\mathrm{Hz}^{-1}$ at years to decades after core-collapse, which is as bright as late-time radio emission observed for a sample of hydrogen-poor SNe. However, the light curves of events with early-time data show more complex behavior in the weeks to months after core-collapse. We qualitatively demonstrate that similar early-time emission can manifest for CSM that is accelerated to speeds of $\sim10^3$ $\mathrm{km}$ $\mathrm{s}^{-1}$ upon ejection, as well as for different viewing angles in case of an asymmetric CSM distribution.

astro-ph.HE↗

arXiv2025

Accretion from a shock-inflated companion: double-peaked supernova lightcurve with periodic modulations

We study the observational signatures from the interactions between a newly born neutron star and a companion star that is impacted by the supernova ejecta. We focus on the cases with bound post-explosion orbits, where the neutron star may periodically gravitationally capture gas from the companion. We find that neutron star accretion must occur if the pre-supernova binary separation is less than about 20 Rsun. This is because the stellar radius expands beyond this radius before the shock-inflated envelope undergoes Kelvin-Helmholtz contraction back to the main sequence. We then consider the internal shocks formed between adjacent episodes of disk wind. The shocks efficiently convert the wind kinetic energy into radiation (due to inverse-Compton cooling), which heats up the supernova ejecta located at much larger radii. The extra heating powers bright optical emission that is periodically modulated on the orbital timescale. The shocks also accelerate non-thermal particles which produce gamma-ray and neutrino emission from 100 MeV to 10 PeV via hardronic pp collisions. The high-energy photons leak out of the supernova ejecta after a delay of several months to one year. Photo-ionization of the slowest parts of the disk wind produces hydrogen recombination lines. We then use the model to explain the puzzling Type Ic supernova SN2022jli which shows a double-peaked optical lightcurve along with many peculiar properties, including delayed onset and rapid shutoff of the second peak, periodic modulations, delayed GeV emission, and narrow Balmer lines. Under this model, SN2022jli had a close-by companion at a pre-supernova binary separation of 10 to 20 Rsun, likely due to an earlier phase of common-envelope evolution.

astro-ph.HE↗

arXiv2025

Low-Luminosity Type IIP Supernovae from the Zwicky Transient Facility Census of the Local Universe. II: Lightcurve Analysis

The Zwicky Transient Facility Census of the Local Universe survey yielded a sample of 330 Type IIP supernovae (SNe) with well-constrained peak luminosities. In paper I (arXiv:2502.19493), we measured their luminosity function and volumetric rate. Here (paper II), we present the largest systematic study of lightcurve properties for Type IIP SNe from a volume-limited survey, analyzing a selected subset of 129 events, including 16 low-luminosity Type IIP (LLIIP) SNe with M${r,peak} \geq -16$ mag. We find that plateau slope correlates with peak brightness, with many LLIIP SNe showing positive slopes--suggesting smaller progenitor radii and distinct density profiles compared to brighter Type IIP SNe. The plateau duration shows only a weak dependence on peak brightness, likely suggesting binary interaction. One SN exhibits a plateau-to-tail drop of >3.5 mag, consistent with an electron-capture or failed SN with very low or zero nickel mass. We derive explosion and progenitor parameters of the entire Type IIP SN sample using semi-analytical and radiation-hydrodynamical models. Based on radiation-hydrodynamical model fitting, LLIIP SNe are characterized by low nickel masses (0.001-0.025 $\mathrm{M_\odot}$), low explosion energies (0.1-0.28 $\times 10^{51}$ erg), low ejecta masses ($8.1^{+0.8}_{-1.7}$ $\mathrm{M\odot}$), and ZAMS masses below 11 $\mathrm{M_\odot}$. In comparison, the full Type IIP SN sample spans a wider range with nickel masses (0.001-0.222 $\mathrm{M_\odot}$), explosion energies (0.10-4.43 $\times 10^{51}$ erg), ejecta masses (5.4-24.8 $\mathrm{M_\odot}$), and ZAMS masses (9.3-16.7 $\mathrm{M_\odot}$). We find strong correlations between peak brightness, explosion energy, and nickel mass that extend to the low-luminosity end. We conclude that LLIIP SNe represent the faint, low-energy end of the Type IIP population and originate from the lowest-mass core-collapse progenitors.

astro-ph.HE↗

arXiv2025

Population Synthesis Study on the Binary Origin of Type Ibn Supernovae

Type Ibn supernovae (SNe) are a class of SN explosions whose progenitors are surrounded by dense helium-rich circumstellar matter (CSM). Some models have been proposed for how to form the dense CSM, with promising scenarios involving either binaries with a low-mass ($\lesssim 3~M_\odot$) helium (He) star, or mergers following common envelope phases between a He star and a compact object. Using rapid binary population synthesis calculations, we estimate the event rate of these channels and compare it with the observed SN Ibn rate. We find that exploding low-mass He stars in close binaries (of separations $\lesssim$ a few 100 $R_\odot$) can be sufficiently produced to account for the observed event rate of SN Ibn, while the merger scenario can likely account for only a fraction of these SNe. We discuss the types of companions expected in the low-mass He star scenario, finding massive main sequence stars ($10$--$20\ M_\odot$) to be typical, with a potentially non-negligible fraction ($<10\%$) of binaries with white dwarf (WD) companions that have long delay times of up to $100$ Myrs.

astro-ph.SR↗

arXiv2025

Stellar Tidal Disruptions by Newborn Neutron Stars or Black Holes: A Mechanism for Hydrogen-poor (Super)luminous Supernovae and Fast Blue Optical Transients

Hydrogen-poor supernovae (SNe) of Type Ibc are explosions of massive stars that lost their hydrogen envelopes, typically due to interactions with a binary companion. We consider the case where the natal kick imparted to the neutron star (NS) or black hole (BH) remnant brings the compact object to a collision with a main-sequence companion, eventually leading to full tidal disruption of the companion. Subsequently, super-Eddington accretion onto the NS/BH launches a powerful, fast wind which collides with the SN ejecta and efficiently converts the kinetic energy of the wind into radiation. The radiation is reprocessed by the surrounding ejecta into a luminous ($\sim 10^{44}$ erg s$^{-1}$ at peak), days to months-long transient with optical peaks from $-19$ to $-21$ mag, comparable to (super)luminous Type Ibc SNe and fast blue optical transients (FBOTs) like AT2018cow. From a Monte-Carlo analysis we estimate the fraction of tidal disruptions following SNe in binaries to be $\sim 0.1$--$1$\%, roughly compatible with the event rates of these luminous SNe. At the broad-brush level, our model reproduces the multi-wavelength and spectral observations of FBOTs, and has the potential to explain peculiar features seen in some (super)luminous SNe which are difficult to reproduce by the conventional magnetar spindown mechanism, such as late-time hydrogen lines, bumpy light curves, and pre-peak excess.

astro-ph.HE↗