More Like this

1. PS1-11aop: Probing the Mass-loss History of a Luminous Interacting Supernova Prior to Its Final Eruption with Multiwavelength Observations

   https://doi.org/10.3847/1538-4357/ad9336  

   Ibik, Adaeze L; Drout, Maria R; Margutti, Raffaella; Matthews, David; Villar, V Ashley; Berger, Edo; Chornock, Ryan; Alexander, Kate D; Eftekhari, Tarraneh; Laskar, Tanmoy; et al (January 2025, The Astrophysical Journal)

   Abstract Luminous interacting supernovae (SNe) are a class of stellar explosions whose progenitors underwent vigorous mass loss in the years prior to core collapse. While the mechanism by which this material is ejected is still debated, obtaining the full density profile of the circumstellar medium (CSM) could reveal more about this process. Here, we present an extensive multiwavelength study of PS1-11aop, a luminous and slowly declining Type IIn SNe discovered by the Pan-STARRS Medium Deep Survey. PS1-11aop had a peakr-band magnitude of −20.5 mag, a total radiated energy >8 × 10⁵⁰erg, and it exploded near the center of a star-forming galaxy with super-solar metallicity. We obtained multiple detections at the location of PS1-11aop in the radio and X-ray bands between 4 and 10 yr post-explosion, and if due to the supernova (SN), it is one of the most luminous radio SNe identified to date. Taken together, the multiwavelength properties of PS1-11aop are consistent with a CSM density profile with multiple zones. The early optical emission is consistent with the SN blastwave interacting with a dense and confined CSM shell, which contains multiple solar masses of material that was likely ejected in the final <10–100 yr prior to the explosion, (∼0.05−1.0M_⊙yr⁻¹at radii of ≲10¹⁶cm). The radio observations, on the other hand, are consistent with a sparser environment (≲2 × 10⁻³M_⊙yr⁻¹at radii of ∼0.5–1 × 10¹⁷cm)—thus probing the history of the progenitor star prior to its final mass-loss episode. 

   more » « less
2. The First Radio View of a Type Ibn Supernova in SN 2023fyq: Understanding the Mass-loss History in the Last Decade before the Explosion

   https://doi.org/10.3847/2041-8213/ae1cb8  

   Baer-Way, Raphael; A_J, Nayana; Jacobson-Galán, Wynn; Chandra, Poonam; Modjaz, Maryam; Wu, Samantha C; Tsuna, Daichi; Margutti, Raffaella; Chornock, Ryan; Pellegrino, Craig; et al (December 2025, The Astrophysical Journal Letters)

   Abstract 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 an 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 to 185 days is best modeled by synchrotron radiation attenuated by free–free absorption from a CSM of density ∼10⁻¹⁸g cm⁻³(∼10⁶ρ_ISM) at a radius of 10¹⁶cm, corresponding to a mass-loss rate of ∼4 × 10⁻³M_⊙yr⁻¹(for a CSM velocity of 1700 km s⁻¹from optical spectroscopy) from 0.7 to 3 yr 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 nondetections, and the 3σupper limits (along with an X-ray nondetection) allow us to infer a drop in the progenitor mass-loss rate at 5–10 yr pre-explosion with $\dot{M}$ < 2.5 × 10⁻³M_⊙yr⁻¹. These results suggest a shell-like CSM from at most 4 × 10¹⁵to 2 × 10¹⁶cm (∼10⁵R_⊙), with a CSM density 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. 

   more » « less
3. An Infrared Echo from a Circumstellar Disk in the Hydrogen- and Helium-poor SN 2024aecx

   https://doi.org/10.3847/1538-4357/ae623e  

   Tinyanont, Samaporn; Wangnok, Kittipong; Andrews, Jennifer E; Foley, Ryan J; Kaewmookda, Methawee; Jencson, Jacob E; Rest, Armin; Auchettl, Katie; Bostroem, K Azalee; Coulter, David A; et al (June 2026, The Astrophysical Journal)

   Abstract We present near-infrared (NIR) spectroscopy of the hydrogen- and helium-poor (Type Ic supernovae (SNe Ic)) SN 2024aecx, which displays a strong NIR excess emerging 32 days postpeak. SN 2024aecx is a peculiar SN Ic that exhibited luminous shock-cooling emission at early times, suggestive of close-in circumstellar medium (CSM), unexpected for this class of supernovae (SNe). Its early NIR spectra are typical for a SNe Ic but with strong Ciabsorption features. By ∼32 days postpeak, the spectra show a strong NIR excess, while maintaining normal optical colors, unprecedented for SNe Ic. We find that the NIR excess is well fit with a single-temperature, optically thin dust model with declining temperature, increasing mass, and roughly constant luminosity over time. The NIR excess appears too promptly for dust to have formed in the supernova (SN) ejecta, indicating an IR echo from preexisting dust in the CSM. The IR echo is likely powered by the relatively slowly evolving SN peak light, and not the brief shock cooling emission, as the latter requires unrealistically high CSM densities to explain the observed dust mass. We consider different potential CSM geometries and find that a thick face-on disk with an inner edge of around 5 × 10¹⁶cm can best explain the dust mass and temperature evolution. In this scenario, the SN shock should start interacting with this CSM 440 ± 200 days postexplosion. CSM around SNe Ic is rare, and follow-up observations of SN 2024aecx will probe the mass-loss process responsible for removing hydrogen and helium from its progenitor star. 

   more » « less
4. Final Moments. III. Explosion Properties and Progenitor Constraints of CSM-interacting Type II Supernovae

   https://doi.org/10.3847/1538-4357/adfa23  

   Jacobson-Galán, W V; Dessart, L; Davis, K W; Bostroem, K A; Kilpatrick, C D; Margutti, R; Filippenko, A V; Foley, R J; Chornock, R; Terreran, G; et al (October 2025, The Astrophysical Journal)

   Abstract We present analysis of the plateau and late-time phase properties of a sample of 39 Type II supernovae (SNe II) that show narrow, transient, high-ionization emission lines (i.e., “IIn-like”) in their early-time spectra from interaction with confined, dense circumstellar material (CSM). Originally presented by W. V. Jacobson-Galán et al., this sample also includes multicolor light curves and spectra extending to late-time phases of 35 SNe with no evidence for IIn-like features at <2 days after first light. We measure photospheric phase light-curve properties for the distance-corrected sample and find that SNe II with IIn-like features have significantly higher luminosities and decline rates at +50 days than the comparison sample, which could be connected to inflated progenitor radii, lower ejecta mass, and/or persistent CSM interaction. However, we find no statistical evidence that the measured plateau durations and⁵⁶Ni masses of SNe II with and without IIn-like features arise from different distributions. We estimate progenitor zero-age main-sequence (ZAMS) masses for all SNe with nebular spectroscopy through spectral model comparisons and find that most objects, both with and without IIn-like features, are consistent with progenitor masses ≤12.5M_⊙. Combining progenitor ZAMS masses with CSM densities inferred from early-time spectra suggests multiple channels for enhanced mass loss in the final years before core collapse, such as a convection-driven chromosphere or binary interaction. Finally, we find spectroscopic evidence for ongoing ejecta-CSM interaction at radii >10¹⁶cm, consistent with substantial progenitor mass-loss rates of ∼10⁻⁴–10⁻⁵M_⊙yr⁻¹(v_w < 50 km s⁻¹) in the final centuries to millennia before explosion. 

   more » « less
5. Unveiling the Diversity of Type IIn Supernovae via Systematic Light-curve Modeling

   https://doi.org/10.3847/1538-4357/adce03  

   Ransome, C L; Villar, V A (June 2025, The Astrophysical Journal)

   Abstract Type IIn supernovae (SNe IIn) are a highly heterogeneous subclass of core-collapse supernovae, spectroscopically characterized by signatures of interaction with a dense circumstellar medium (CSM). Here, we systematically model the light curves of 142 archival SNe IIn using the Modular Open Source Fitter for Transients. We find that the observed and inferred properties of SN IIn are diverse, but there are some trends. The typical supernova CSM is dense (∼10⁻¹²g cm⁻³) with highly diverse CSM geometry, with a median CSM mass of ∼1M_⊙. The ejecta are typically massive (≳10M_⊙), suggesting massive progenitor systems. We find positive correlations between the CSM mass and the rise and fall times of SNe IIn. Furthermore, there are positive correlations between the rise time and fall times and ther-band luminosity. We estimate the mass-loss rates of our sample (where spectroscopy is available) and find a high median mass-loss rate of ∼10⁻²M_⊙yr⁻¹, with a range between 10⁻³and 1M_⊙yr⁻¹. These mass-loss rates are most similar to the mass loss from great eruptions of luminous blue variables, consistent with the direct progenitor detections in the literature. We also discuss the role that binary interactions may play, concluding that at least some of our SNe IIn may be from massive binary systems. Finally, we estimate a detection rate of 1.6 × 10⁵yr⁻¹in the upcoming Legacy Survey of Space and Time at the Vera C. Rubin Observatory. 

   more » « less