More Like this

1. Final Moments. I. Precursor Emission, Envelope Inflation, and Enhanced Mass Loss Preceding the Luminous Type II Supernova 2020tlf

   https://doi.org/10.3847/1538-4357/ac3f3a  

   Jacobson-Galán, W. V.; Dessart, L.; Jones, D. O.; Margutti, R.; Coppejans, D. L.; Dimitriadis, G.; Foley, R. J.; Kilpatrick, C. D.; Matthews, D. J.; Rest, S.; et al (January 2022, The Astrophysical Journal)

   Abstract We present panchromatic observations and modeling of supernova (SN) 2020tlf, the first normal Type II-P/L SN with confirmed precursor emission, as detected by the Young Supernova Experiment transient survey. Pre-SN activity was detected in riz -bands at −130 days and persisted at relatively constant flux until first light. Soon after discovery, “flash” spectroscopy of SN 2020tlf revealed narrow, symmetric emission lines that resulted from the photoionization of circumstellar material (CSM) shed in progenitor mass-loss episodes before explosion. Surprisingly, this novel display of pre-SN emission and associated mass loss occurred in a red supergiant (RSG) progenitor with zero-age main-sequence mass of only 10–12 M ⊙ , as inferred from nebular spectra. Modeling of the light curve and multi-epoch spectra with the non-LTE radiative-transfer code CMFGEN and radiation-hydrodynamical code HERACLES suggests a dense CSM limited to r ≈ 10 15 cm, and mass-loss rate of 10 −2 M ⊙ yr −1 . The luminous light-curve plateau and persistent blue excess indicates an extended progenitor, compatible with an RSG model with R ⋆ = 1100 R ⊙ . Limits on the shock-powered X-ray and radio luminosity are consistent with model conclusions and suggest a CSM density of ρ < 2 × 10 −16 g cm −3 for distances from the progenitor star of r ≈ 5 × 10 15 cm, as well as a mass-loss rate of M ̇ < 1.3 × 10 − 5 M ☉ yr − 1 at larger distances. A promising power source for the observed precursor emission is the ejection of stellar material following energy disposition into the stellar envelope as a result of gravity waves emitted during either neon/oxygen burning or a nuclear flash from silicon combustion. 

   more » « less
2. Weak Mass Loss from the Red Supergiant Progenitor of the Type II SN 2021yja

   https://doi.org/10.3847/1538-4357/ac75f0  

   Hosseinzadeh, Griffin; Kilpatrick, Charles D.; Dong, Yize; Sand, David J.; Andrews, Jennifer E.; Bostroem, K. Azalee; Janzen, Daryl; Jencson, Jacob E.; Lundquist, Michael; Meza Retamal, Nicolas E.; et al (August 2022, The Astrophysical Journal)

   Abstract We present high-cadence optical, ultraviolet (UV), and near-infrared data of the nearby ( D ≈ 23 Mpc) Type II supernova (SN) 2021yja. Many Type II SNe show signs of interaction with circumstellar material (CSM) during the first few days after explosion, implying that their red supergiant (RSG) progenitors experience episodic or eruptive mass loss. However, because it is difficult to discover SNe early, the diversity of CSM configurations in RSGs has not been fully mapped. SN 2021yja, first detected within ≈ 5.4 hours of explosion, shows some signatures of CSM interaction (high UV luminosity and radio and x-ray emission) but without the narrow emission lines or early light-curve peak that can accompany CSM. Here we analyze the densely sampled early light curve and spectral series of this nearby SN to infer the properties of its progenitor and CSM. We find that the most likely progenitor was an RSG with an extended envelope, encompassed by low-density CSM. We also present archival Hubble Space Telescope imaging of the host galaxy of SN 2021yja, which allows us to place a stringent upper limit of ≲ 9 M ☉ on the progenitor mass. However, this is in tension with some aspects of the SN evolution, which point to a more massive progenitor. Our analysis highlights the need to consider progenitor structure when making inferences about CSM properties, and that a comprehensive view of CSM tracers should be made to give a fuller view of the last years of RSG evolution. 

   more » « less
3. The superluminous Type IIn supernova ASASSN-15ua: part of a continuum in extreme precursor mass-loss

   https://doi.org/10.1093/mnras/stad3631  

   Dickinson, Danielle; Smith, Nathan; Andrews, Jennifer E.; Milne, Peter; Kilpatrick, Charles D.; Milisavljevic, Dan (November 2023, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We present a series of ground-based photometry and spectroscopy of the superluminous Type IIn supernova (SN) ASASSN-15ua, which shows evidence for strong interaction with pre-existing dense circumstellar material (CSM). Our observations constrain the speed, mass-loss rate, and extent of the progenitor wind shortly before explosion. A narrow P Cygni absorption component reveals a progenitor wind speed of ∼100 km s−1. As observed in previous SNe IIn, the intermediate-width H α emission became more asymmetric and blueshifted over time, suggesting either asymmetric CSM, an asymmetric explosion, or increasing selective extinction from dust within the post-shock shell or SN ejecta. Based on the CSM radius and speed, we find that the progenitor suffered extreme eruptive mass-loss with a rate of 0.1–1 M⊙ yr−1 during the ∼12 yr immediately before the death of the star that imparted ∼ 1048 erg of kinetic energy to the CSM. Integrating its V-band light curve over the first 170 d after discovery, we find that ASASSN-15ua radiated at least 3 × 1050 erg in visual light alone, giving a lower limit to the total radiated energy that may have approached 1051 erg. ASASSN-15ua exhibits many similarities to two well-studied superluminous SNe IIn: SN 2006tf and SN 2010jl. Based on a detailed comparison of these three, we find that ASASSN-15ua falls in between these two events in a wide variety of observed properties and derived physical parameters, illustrating a continuum of behaviour across superluminous SNe IIn. 

   more » « less
4. The Type Ibn Supernova 2019kbj: Indications for Diversity in Type Ibn Supernova Progenitors

   https://doi.org/10.3847/1538-4357/acb432  

   Ben-Ami, Tom; Arcavi, Iair; Newsome, Megan; Farah, Joseph; Pellegrino, Craig; Terreran, Giacomo; Burke, Jamison; Hosseinzadeh, Griffin; McCully, Curtis; Hiramatsu, Daichi; et al (March 2023, The Astrophysical Journal)

   Abstract Type Ibn supernovae (SNe) are a rare class of stellar explosions whose progenitor systems are not yet well determined. We present and analyze observations of the Type Ibn SN 2019kbj, and model its light curve in order to constrain its progenitor and explosion parameters. SN 2019kbj shows roughly constant temperature during the first month after peak, indicating a power source (likely circumstellar material interaction) that keeps the continuum emission hot at ∼15,000 K. Indeed, we find that the radioactive decay of⁵⁶Ni is disfavored as the sole power source of the bolometric light curve. A radioactive decay + circumstellar material (CSM) interaction model, on the other hand, does reproduce the bolometric emission well. The fits prefer a uniform-density CSM shell rather than CSM due to a steady mass-loss wind, similar to what is seen in other Type Ibn SNe. The uniform-density CSM shell model requires ∼0.1M_⊙of⁵⁶Ni and ∼1M_⊙total ejecta mass to reproduce the light curve. SN 2019kbj differs in this manner from another Type Ibn SN with derived physical parameters, SN 2019uo, for which an order of magnitude lower⁵⁶Ni mass and larger ejecta mass were derived. This points toward a possible diversity in SN Ibn progenitor systems and explosions. 

   more » « less
5. The X-Ray Luminous Type Ibn SN 2022ablq: Estimates of Preexplosion Mass Loss and Constraints on Precursor Emission

   https://doi.org/10.3847/1538-4357/ad8bc5  

   Pellegrino, C.; Modjaz, M.; Takei, Y.; Tsuna, D.; Newsome, M.; Pritchard, T.; Baer-Way, R.; Bostroem, K_A; Chandra, P.; Charalampopoulos, P.; et al (November 2024, The Astrophysical Journal)

   Abstract Type Ibn supernovae (SNe Ibn) are rare stellar explosions powered primarily by interaction between the SN ejecta and H-poor, He-rich material lost by their progenitor stars. Multiwavelength observations, particularly in the X-rays, of SNe Ibn constrain their poorly understood progenitor channels and mass-loss mechanisms. Here we present Swift X-ray, ultraviolet, and ground-based optical observations of the Type Ibn SN 2022ablq, only the second SN Ibn with X-ray detections to date. While similar to the prototypical Type Ibn SN 2006jc in the optical, SN 2022ablq is roughly an order of magnitude more luminous in the X-rays, reaching unabsorbed luminositiesL_X∼ 4 × 10⁴⁰erg s⁻¹between 0.2–10 keV. From these X-ray observations we infer time-varying mass-loss rates between 0.05 and 0.5M_⊙yr⁻¹peaking 0.5–2 yr before explosion. This complex mass-loss history and circumstellar environment disfavor steady-state winds as the primary progenitor mass-loss mechanism. We also search for precursor emission from alternative mass-loss mechanisms, such as eruptive outbursts, in forced photometry during the 2 yr before explosion. We find no statistically significant detections brighter thanM≈ −14—too shallow to rule out precursor events similar to those observed for other SNe Ibn. Finally, numerical models of the explosion of an ∼15M_⊙helium star that undergoes an eruptive outburst ≈1.8 yr before explosion are consistent with the observed bolometric light curve. We conclude that our observations disfavor a Wolf–Rayet star progenitor losing He-rich material via stellar winds and instead favor lower-mass progenitor models, including Roche-lobe overflow in helium stars with compact binary companions or stars that undergo eruptive outbursts during late-stage nucleosynthesis stages. 

   more » « less