Samaporn Tinyanont

Type IIP supernovae (SNe IIP) exhibit a significant diversity in their explosion properties, yet the physical mechanisms driving this diversity remain unknown. In this work, we present photometric and spectroscopic observations of SN 2024abfl, a SN IIP in NGC 2146 with a directly detected red supergiant (RSG) progenitor. We find it has a low plateau luminosity ( M _V ∼ −15 mag) and a relatively long plateau length (∼126.5 days). We estimated a ⁵⁶ Ni mass of 0.014 ± 0.006 M _⊙ from the tail luminosities, and an explosion energy of 0.21 ^+0.03 _−0.02 foe (1 foe = 10 ⁵¹ erg) and a progenitor mass of 9.50 ^+0.50 _−0.25 M _⊙ from radiation-hydrodynamic modelling. The spectral evolution of SN 2024abfl is similar to those of other SNe IIP. However, SN 2024abfl exhibits much lower ejecta velocities than other SNe IIP at similar epochs. At later epochs, we find a relatively high-velocity H α absorption feature at ∼ − 4000 km s ⁻¹ , possibly due to a fast-moving plume of matter in the inner ejecta, and two emission features at ±2000 km s ⁻¹ , possibly caused by circumstellar medium (CSM) interaction, which indicates a mass-loss event before the SN explosion with a mass-loss rate of ∼10 ⁻⁶ M _⊙ yr ⁻¹ . We also estimate the progenitor mass to be ≤15 M _⊙ based on nebular spectra. We conclude that SN 2024abfl is a low-luminosity SN IIP originating from a low-mass RSG progenitor.

We present JWST/MIRI observations of the Type I superluminous supernova (SLSN) 2017gci obtained over 2000 rest-frame days after the supernova (SN) exploded, which represent the latest phase images taken of any known SLSN to date. We find that archival Wide-field Infrared Survey Explorer (WISE) detections of SN 2017gci taken 70–200 days after explosion are most likely explained by an IR dust echo from a ∼10 ⁻⁴ M _⊙ shell of preexisting dust, as opposed to freshly formed dust. New JWST observations reveal mid-infrared emission at the position of SN 2017gci; however, the flux level and spatial offset indicate that this emission is most likely dominated by the host galaxy. We therefore derive upper limits from these observations to constrain dust emission at late times. Radiative transfer modeling of carbonaceous dust shows that warm optically thin dust masses up to 0.18 M _⊙ are excluded at the 3 σ confidence level. However, substantially larger dust masses cannot be ruled out if the dust is optically thick. Infrared detections of other SLSNe have suggested that SLSNe may be highly efficient dust producers. While our constraints are insufficient to determine the total dust yield of SN 2017gci, they indicate that any late-time dust emission must either be modest compared to the most dust-rich SNe or arise from dust that is optically thick. A larger sample of deep infrared observations will be required to determine whether SLSNe are significant contributors to cosmic dust production.

We present multiepoch high-resolution optical spectroscopy ( R ≃ 80,000) of the emission-line object NaSt1 to test its proposed binary nature, along with long-term multiband photometry, mid-infrared spectroscopy, and spatially resolved integral field unit (IFU) spectroscopy to probe the circumstellar kinematics of the system. We detect two groups of 36 emission lines showing radial velocity (RV) variation with a mean period of 311 ± 5 days, but varying in opposite phase. We associate these two groups with the optically thick wind of the stripped primary star and the wind–wind collision region with the companion star, providing strong evidence for binarity. The RV and light curve (LC) periods are consistent within the uncertainties, ruling out ellipsoidal modulation, which would require an orbital period of about 620 days. The RV–LC phase relationship and high-ionization lines favor binary interaction over pulsations. We model the 1–5 μ m spectrum of NaSt1 and find two optically thin dust components: hot: T _h ≃ 1230 K and M _h ≃ 2 × 10 ⁻¹⁰ M _⊙ , and warm: T _c ≃ 660 K and M _c ≃ 3 × 10 ⁻⁸ M _⊙ . IFU spectroscopy spatially resolves the circumstellar medium in the [N ii ] λ 6548 and λ 6584 emission lines, showing a deprojected expansion velocity of ∼31 km s ⁻¹ , implying a dynamical age of ∼40 yr. This short timescale suggests that the nebula was produced by recent mass loss. The system may represent a Galactic analog of a massive binary undergoing a mass-loss process to become a stripped-envelope supernova progenitor.

We present multiwavelength observations and analysis of SN 2024iss, a Type IIb supernova (SN IIb) located at ∼14 Mpc. The first Zwicky Transient Facility detection of SN 2024iss is ∼40 minutes after first light (one of the earliest detections of a SN IIb to date) and a Hubble Space Telescope (HST) UV spectrum was obtained at 7 days (the earliest HST UV SN IIb spectrum to date). We estimate an ejecta mass range of 1.1–3.3 M _⊙ and a ⁵⁶ Ni mass of 0.11 ± 0.01 M _⊙ from bolometric light-curve modeling and He-star model comparisons. We fit shock-cooling emission models to estimate a progenitor radius of 100–320 R _⊙ and an envelope mass of 0.07–0.46 M _⊙ . We compare optical/UV spectra to binary progenitor models, which indicate a stripped H-rich envelope mass of 0.19–0.28 M _⊙ . We use early-time X-ray detections to calculate circumstellar material (CSM) densities that are consistent with a progenitor mass-loss rate of 5 × 10 ⁻⁴ M _⊙ yr ⁻¹ ( v _w = 100 km s ⁻¹ ), corresponding to 2–5 yr preexplosion. In the UV, we observe strong Mg ii emission extending to 15,000 km s ⁻¹ as well as weak P Cygni profiles of iron-group elements (e.g., Fe, Ti, Al, Ni) present in outer SN ejecta. The overall spectroscopic evolution of SN 2024iss is comparable to that of SNe IIb, but its increased brightness at peak is influenced by SN ejecta–CSM interaction. Nebular spectroscopy of SN 2024iss at ∼260–412 days reveals multipeaked forbidden-line profiles of O i and Mg i ] indicative of inner ejecta asymmetry and/or clumping. We demonstrate the utility of a rich, multiwavelength data set for constraining the progenitor systems and explosion dynamics of SNe IIb.

We present optical and near-infrared (NIR) observations of the Type Ib supernova (SN) 2024rbc. Emission from the first CO overtone, resting on a dust continuum at 2.3−2.4 μ m, was observed at 62 days postexplosion. The CO band heads are not resolved, and the emission appears broad, lacking sharp spectral features. This is the first observation of CO in the ejecta of a Type Ib SN reported in literature. The spectra of SN 2024rbc exhibit strong He I lines and numerous neutral and ionized metal lines. Comparing the spectral evolution of SN 2024rbc to other Type Ib, Ic, and IIb SNe indicates it is a Type Ib SN. We compare the velocities of key optical lines to examine the evolution of the ejecta. Additionally, fitting SN light-curve models of helium star progenitors computed with the STELLA code to photometric observations indicates a ⁵⁶ Ni mass of 0.07 M _⊙ and an ejecta mass of 1.7 M _⊙ . Fitting an LTE model to the CO overtone implies a CO mass of 5.2 × 10 ⁻⁴ M _⊙ , a CO temperature of 4040 K, and a CO velocity width of 5905 km s ⁻¹ . We also fitted a modified blackbody model to the dust continuum, deriving a dust temperature of 910 K and a dust mass of 1.3 × 10 ⁻³ M _⊙ . The CO provides direct evidence for the onset of dust formation, and the observed dust continuum likely originates from newly formed dust in the ejecta. However, robust dust mass estimates require mid-infrared (MIR) observations.

Interacting supernovae probe the twilight years of massive stars, exhibiting signatures of interaction between the supernova ejecta and surrounding material expelled from the progenitor. We present the peculiar interacting supernova, SN 2025ngs in NGC 5961 (37.8 Mpc). This transient toes the line between strongly interacting supernovae (Type IIn) and Type IIP supernovae. SN 2025ngs presents photometrically as a short-plateau supernova, with a plateau duration t PT ≈ 70 days. Interaction features subside within a week postexplosion, consistent with the growing number of flash supernovae, giving way to a short period where a typical IIP spectrum is exhibited. Towards the drop off the plateau, interaction features re-emerge, exhibiting complex H α profiles throughout the rest of the transient evolution. We compare with models of early spectra, finding the abundances generally consistent with a supergiant progenitor with a high mass-loss rate (10 ⁻³ M _⊙ yr ⁻¹ ). Early, high-resolution spectra reveal a double-horned H α profile, providing strong evidence for shock interaction with a proximate disk-like circumstellar medium. Spectroscopically, SN 2025ngs closely resembles the luminous SN 1998S, despite photometric differences, with SN 2025ngs having a relatively modest peak magnitude of M _V = −17.9 mag, adding another member to the surprisingly diverse 98S-like group.

We present the discovery of EP250827b/SN 2025wkm, an X-ray flash (XRF) discovered by the Einstein Probe (EP), accompanied by a broad-line Type Ic supernova (SN Ic-BL) at z = 0.1194. EP250827b possesses a prompt X-ray luminosity of ∼10 ⁴⁵ erg s ⁻¹ , lasts over 1000 s, and has a peak energy E _p < 1.5 keV at 90% confidence. SN 2025wkm possesses a double-peaked optical light curve (LC), though its bolometric luminosity plateaus after its initial peak for ∼20 days, consistent with a central engine injecting additional energy into the explosion. Its spectrum transitions from a blue to red continuum with clear blueshifted broad absorption features consistent with a SN Ic-BL classification. We do not detect any transient radio emission and rule out the existence of an on-axis, energetic jet ≳10 ⁵⁰ erg assuming a typical LGRB circumburst constant density ( n ≈ 10 ⁻³ –10 ⁻¹ cm ⁻³ ) and microphysical parameters ( ϵ _e = 0.1 and ϵ _B = 0.01). In the model we invoke, the collapse gives rise to a long-lived magnetar, potentially surrounded by an accretion disk. Magnetically driven winds from the magnetar and the disk mix together and break out with a velocity ∼0.35 c and interact with an extended circumstellar medium with radius ∼10 ¹³ cm, generating X-ray breakout emission through nonthermal free–free processes. The disk outflows and magnetar winds power blackbody photospheric emission as they cool adiabatically and thermalize, producing the first SN peak. The spin-down luminosity of the magnetar and radioactive decay of ⁵⁶ Ni power the late-time emission. We end by discussing the landscape of XRF-SNe within the context of EP’s recent discoveries.

We present a comprehensive multiwavelength analysis of the long-duration gamma-ray burst (GRB) 250424A. Our dataset spans from the prompt gamma-ray emission to late-time optical monitoring, including spectra obtained with the Keck 10 m telescope. We find that the afterglow light curves display a prominent, simultaneous shallow decay phase in both X-ray and optical bands, followed by an achromatic transition to a standard decay regime. The broadband spectral energy distributions are well modeled by a single power-law function, indicating a common synchrotron origin for the emission across frequencies. We interpret the afterglow evolution within the framework of a relativistic forward shock refreshed by continuous energy injection. This scenario successfully reproduces the observed temporal and spectral behavior, yielding an isotropic equivalent kinetic energy of E_K,iso ≈ 5.5 × 10⁵² erg and an injection index of q ≈ 0.34 in a constant-density circumburst environment. The shallow decay phase is consistent with sustained energy injection lasting ∼9 ks. Despite the relatively low redshift, late-time optical observations reveal no distinct supernova component; however, our derived upper limits do not strictly rule out the presence of a typical GRB-associated supernova.

Calcium-strong transients (CaSTs) are a subclass of faint and rapidly evolving supernovae (SNe) that exhibit strong calcium features and notably weak oxygen features. The small but growing population of CaSTs exhibits some aspects similar to thermonuclear SNe but others similar to massive star core-collapse events, leading to intriguing questions on their physical origins. SN 2025coe is one of the nearest CaSTs discovered to date, and our coordinated multiwavelength observations obtained days to weeks postexplosion reveal new insights into these enigmatic transients. With the most robust near-IR (NIR) spectroscopic time series of a CaST collected to date, SN 2025coe shows spectral signatures characteristic of Type Ib SNe (SNe Ib; i.e., He-rich stripped-envelope SNe (SESNe)). SN 2025coe is the third X-ray-detected CaST and our analysis of Neil Gehrels Swift Observatory X-ray data suggests interaction with 0.12 ± 0.11 M _⊙ of circumstellar material (CSM) extending to at least 2 × 10 ¹⁵ cm (∼30,000 R _⊙ ), while our analysis of the 1–240 GHz radio nondetections gives an outer radius of that CSM of at most ∼5 × 10 ¹⁵ cm. This inferred nearby high-density CSM extending out to (3.5 ± 1.5) × 10 ¹⁵ cm is similar to that seen in the other two X-ray-detected CaSTs, and its presence suggests that either intensive mass loss from a massive star or some exotic pre-SN mass ejection may be a common feature of this subclass. Our work also expands upon recent studies of the optical properties of SN 2025coe and explores our current understanding of different progenitor systems that could possibly produce CaSTs.