More Like this

1. Characterizing the Ordinary Broad-line Type Ic SN 2023pel from the Energetic GRB 230812B

   https://doi.org/10.3847/2041-8213/ad16e7  

   Srinivasaragavan, Gokul P; Swain, Vishwajeet; O’Connor, Brendan; Anand, Shreya; Ahumada, Tomás; Perley, Daniel; Stein, Robert; Sollerman, Jesper; Fremling, Christoffer; Cenko, S Bradley; et al (January 2024, The Astrophysical Journal Letters)

   Abstract We report observations of the optical counterpart of the long gamma-ray burst (GRB) GRB 230812B and its associated supernova (SN) SN 2023pel. The proximity (z= 0.36) and high energy (E_γ,iso∼ 10⁵³erg) make it an important event to study as a probe of the connection between massive star core collapse and relativistic jet formation. With a phenomenological power-law model for the optical afterglow, we find a late-time flattening consistent with the presence of an associated SN. SN 2023pel has an absolute peakr-band magnitude ofM_r= −19.46 ± 0.18 mag (about as bright as SN 1998bw) and evolves on quicker timescales. Using a radioactive heating model, we derive a nickel mass powering the SN ofM_Ni= 0.38 ± 0.01M_⊙and a peak bolometric luminosity ofL_bol∼ 1.3 × 10⁴³erg s⁻¹. We confirm SN 2023pel’s classification as a broad-line Type Ic SN with a spectrum taken 15.5 days after its peak in therband and derive a photospheric expansion velocity ofv_ph= 11,300 ± 1600 km s⁻¹at that phase. Extrapolating this velocity to the time of maximum light, we derive the ejecta massM_ej= 1.0 ± 0.6M_⊙and kinetic energy $E_{\mathrm{KE}}={1.3}_{-1.2}^{+3.3}\times {10}^{51}\mathrm{erg}$ . We find that GRB 230812B/SN 2023pel has SN properties that are mostly consistent with the overall GRB-SN population. The lack of correlations found in the GRB-SN population between SN brightness andE_γ,isofor their associated GRBs across a broad range of 7 orders of magnitude provides further evidence that the central engine powering the relativistic ejecta is not coupled to the SN powering mechanism in GRB-SN systems. 

   more » « less
2. Circumstellar Interaction Signatures in the Low-luminosity Type II SN 2021gmj

   https://doi.org/10.3847/1538-4357/ad4d55  

   Meza-Retamal, Nicolás; Dong_董, Yize 一泽; Bostroem, K Azalee; Valenti, Stefano; Galbany, Lluís; Pearson, Jeniveve; Hosseinzadeh, Griffin; Andrews, Jennifer E; Sand, David J; Jencson, Jacob E; et al (August 2024, The Astrophysical Journal)

   Abstract We present comprehensive optical observations of SN 2021gmj, a Type II supernova (SN II) discovered within a day of explosion by the Distance Less Than 40 Mpc survey. Follow-up observations show that SN 2021gmj is a low-luminosity SN II (LL SN II), with a peak magnitudeM_V= −15.45 and an Feiivelocity of ∼1800 km s⁻¹at 50 days past explosion. Using the expanding photosphere method, we derive a distance of ${17.8}_{-0.4}^{+0.6}$ Mpc. From the tail of the light curve we obtain a radioactive nickel mass of $M_{{}^{56}\mathrm{Ni}}$ = 0.014 ± 0.001M_⊙. The presence of circumstellar material (CSM) is suggested by the early-time light curve, early spectra, and high-velocity Hαin absorption. Analytical shock-cooling models of the light curve cannot reproduce the fast rise, supporting the idea that the early-time emission is partially powered by the interaction of the SN ejecta and CSM. The inferred low CSM mass of 0.025M_⊙in our hydrodynamic-modeling light-curve analysis is also consistent with our spectroscopy. We observe a broad feature near 4600 Å, which may be high-ionization lines of C, N, or/and Heii. This feature is reproduced by radiation-hydrodynamic simulations of red supergiants with extended atmospheres. Several LL SNe II show similar spectral features, implying that high-density material around the progenitor may be common among them. 

   more » « less
3. The New Status Qvo? SN 2021qvo Is Another 2003fg-like Type Ia Supernova with a Rising Light-curve Bump

   https://doi.org/10.3847/1538-4357/ae279b  

   Paniagua, I_A Abreu; Hoogendam, W B; Jones, D O; Dimitriadis, G; Foley, R J; Gall, C; O’Brien, J; Taggart, K; Angus, C R; Ashall, C; et al (January 2026, The Astrophysical Journal)

   Abstract In recent years, multiple Type Ia supernovae (SNe Ia) have been observed with “bumps” in their rising light curves shortly after the explosion. Here, we present SN 2021qvo: an SN Ia that exhibits a clear early bump in photometry obtained by the Young Supernova Experiment. Photometric and spectroscopic observations of SN 2021qvo show that it has a broader light curve, higher peak luminosity, shallower Siiiλ5972 pseudoequivalent width, and lower ejecta velocities than normal SNe Ia, which are all consistent with the characteristics of the 2003fg-like (often called “super-Chandrasekhar”) SN subtype. Including SN 2021qvo, just four known 2003fg-like SNe Ia have sufficient prepeak data to reveal a rising light-curve bump, and all four have bump detections. A host-galaxy analysis reveals that SN 2021qvo exploded in a low-mass galaxy $\log (M_{*}/M_{\odot })=7.83_{-0.24}^{+0.17}$ , also consistent with other members of this class. The current leading early bump 2003fg-like SN Ia progenitor model involves an interaction between the circumstellar material (CSM) and the SN ejecta. We test the validity of this theory by modeling the early bump and subsequent light-curve evolution of SN 2021qvo with the Modular Open Source Fitter for Transients. We find that the bump can be modeled with a best-fit CSM mass in the rangeM_CSM= 3.31−8.51 × 10⁻³M_⊙. SN 2021qvo adds to the small but growing number of 2003fg-like SNe Ia with rising light-curve bumps; as the number of these SNe Ia with CSM estimates continues to grow, population-level inferences about the CSM distribution will be able to constrain the progenitor scenario for these SNe Ia. 

   more » « less
4. One Year of SN 2023ixf: Breaking through the Degenerate Parameter Space in Light-curve Models with Pulsating Progenitors

   https://doi.org/10.3847/1538-4357/adf222  

   Hsu, Brian; Smith, Nathan; Goldberg, Jared A; Bostroem, K Azalee; Hosseinzadeh, Griffin; Sand, David J; Pearson, Jeniveve; Hiramatsu, Daichi; Andrews, Jennifer E; Beasor, Emma R; et al (September 2025, The Astrophysical Journal)

   Abstract We present and analyze the extensive optical broadband photometry of the Type II SN 2023ixf up to 1 yr after explosion. We find that, when compared to two preexisting model grids, the bolometric light curve is consistent with drastically different combinations of progenitor and explosion properties. This may be an effect of known degeneracies in Type IIP light-curve models. We independently compute a large grid ofMESA+STELLAsingle-star progenitor and light-curve models with various zero-age main-sequence masses, mass-loss efficiencies, and convective efficiencies. Using the observed progenitor variability as an additional constraint, we select stellar models consistent with the pulsation period and explode them according to previously established scaling laws to match plateau properties. Our hydrodynamic modeling indicates that SN 2023ixf is most consistent with a moderate-energy ( $E_{\exp }\approx 7\times 10^{50}$ erg) explosion of an initially high-mass red supergiant progenitor (≳16.5M_⊙) that lost a significant amount of mass in its prior evolution, leaving a low-mass hydrogen envelope (≲3M_⊙) at the time of explosion, with a radius ≳950R_⊙and a synthesized⁵⁶Ni mass of ≈0.068M_⊙. We posit that previous mass transfer in a binary system may have stripped the envelope of SN 2023ixf’s progenitor. The analysis method with pulsation period presented in this work offers a way to break degeneracies in light-curve modeling in the future, particularly with the upcoming Vera C. Rubin Observatory Legacy Survey of Space and Time, when a record of progenitor variability will be more common. 

   more » « less
5. SN 2021aaev: A Hydrogen-rich Superluminous Supernova with Early Flash and Long-lived Circumstellar Interaction in an Unusual Host Environment

   https://doi.org/10.3847/1538-4357/ae374c  

   Hu_胡, Yang 阳; Lunnan, Ragnhild; Pessi, Priscila J; Saldana-Lopez, Alberto; Jerkstrand, Anders; Sollerman, Jesper; Schulze, Steve; Anderson, Joseph P; Brennan, Seán J; Cosentino, Stefano P; et al (March 2026, The Astrophysical Journal)

   Abstract We present photometric and spectroscopic observations of SN 2021aaev, a hydrogen-rich, superluminous supernova with persistent (at least ∼100 days) narrow Balmer lines (SLSN-IIn) at redshiftz= 0.1557. SN 2021aaev rose over 28.1  ±  1.0 rest-frame days after explosion, reaching a peak absolute magnitude of −21.46 ± 0.01 in the ATLASoband. The prepeak spectra resemble those of typical Type IIn SNe with flash-ionization features arising from the interaction with a dense, confined circumstellar medium (CSM), albeit the flash timescale is longer than usual (>20 days). Postpeak, the narrow emission lines evolve slowly, and the absence of ejecta features indicates strong deceleration by the CSM. The total radiated energy (about 1.41 × 10⁵¹erg) is possibly explained by a low-mass (1–2M_⊙) ejecta ploughing into a massive (9–19M_⊙), extended (outer radius >1 × 10¹⁶cm) H-rich CSM, or alternatively by magnetar-powered models. Interestingly, the host environment consists of a spiral galaxy with a red substructure in the southeastern part, and the SN’s exact location coincides with this quiescent red region (star formation rate $=0.02_{-0.02}^{+0.13}{M}_{\odot }$ yr⁻¹). Given the atypical environment and the obscuring effect of the massive CSM, a thermonuclear (Type Ia-CSM) origin cannot be ruled out. Altogether, SN 2021aaev is a compelling case to study the diversity of SLSN-IIn features and their host environments. 

   more » « less