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1. The first days of Type II-P core collapse supernovae in the gamma-ray range

   https://doi.org/10.1093/mnras/stac217  

   Cristofari, P. ; Marcowith, A. ; Renaud, M. ; Dwarkadas, V. V. ; Tatischeff, V. ; Giacinti, G. ; Peretti, E. ; Sol, H. ( January 2022 , Monthly Notices of the Royal Astronomical Society)

   Type II-P supernovæ (SNe), the most common core-collapse SNe type, result from the explosions of red supergiant stars. Their detection in the radio domain testifies of the presence of relativistic electrons, and shows that they are potentially efficient energetic particle accelerators. If hadrons can also be accelerated, these energetic particles are expected to interact with the surrounding medium to produce a gamma-ray signal even in the multi–TeV range. The intensity of this signal depends on various factors, but an essential one is the density of the circumstellar medium. Such a signal should however be limited by electron–positron pair production arising from the interaction of the gamma-ray photons with optical photons emitted by the supernova photosphere, which can potentially degrade the gamma-ray signal by over ten orders of magnitude in the first days/weeks following the explosion. We calculate the gamma-gamma opacity from a detailed modelling of the time evolution of the forward shock and supernova photosphere, taking a full account of the non-isotropy of the photon interactions. We discuss the time-dependent gamma-ray TeV emission from Type II-P SNe as a function of the stellar progenitor radius and mass-loss rate, as well as the explosion energy and mass of the ejected material.more »We evaluate the detectability of the SNe with the next generation of Cherenkov telescopes. We find that, while most extragalactic events may be undetectable, Type II-P SNe exploding in our Galaxy or in the Magellanic Clouds should be detected by gamma-ray observatories such as the upcoming Cherenkov Telescope Array.

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2. Core-collapse supernovae in dense environments – particle acceleration and non-thermal emission

   https://doi.org/10.1093/mnras/stac2234  

   Brose, R. ; Sushch, I. ; Mackey, J. ( August 2022 , Monthly Notices of the Royal Astronomical Society)

   Supernova remnants (SNRs) are known to accelerate cosmic rays from the detection of non-thermal emission in radio waves, X-rays, and gamma-rays. However, the ability to accelerate cosmic rays up to PeV energies has yet to be demonstrated. The presence of cut-offs in the gamma-ray spectra of several young SNRs led to the idea that PeV energies might only be achieved during the first years of a remnant’s evolution. We use our time-dependent acceleration-code RATPaC to study the acceleration of cosmic rays in supernovae expanding into dense environments around massive stars. We performed spherically symmetric one-dimensional (1D) simulations in which we simultaneously solve the transport equations for cosmic rays, magnetic turbulence, and the hydrodynamical flow of the thermal plasma in the test-particle limit. We investigated typical circumstellar-medium (CSM) parameters expected around red supergiant (RSG) and luminous blue variable (LBV) stars for freely expanding winds and accounted for the strong γγ absorption in the first days after explosion. The maximum achievable particle energy is limited to below $600\,$TeV even for the largest considered values of the magnetic field and mass-loss rates. The maximum energy is not expected to surpass $\approx 200\,$ and $\approx 70\,$TeV for LBVs and RSGs that experience moderate mass-lossmore »prior to the explosion. We find gamma-ray peak-luminosities consistent with current upper limits and evaluate that current-generation instruments are able to detect the gamma-rays from Type-IIP explosions at distances up to $\approx 60\,$ kpc and Type-IIn explosions up to $\approx 1.0\,$ Mpc. We also find a good agreement between the thermal X-ray and radio synchrotron emission predicted by our models with a range of observations.

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3. Circumstellar Medium Constraints on the Environment of Two Nearby Type Ia Supernovae: SN 2017cbv and SN 2020nlb

   https://doi.org/10.3847/1538-4357/ac20da  

   Sand, D. J. ; Sarbadhicary, S. K. ; Pellegrino, C. ; Misra, K. ; Dastidar, R. ; Brown, P. J. ; Itagaki, K. ; Valenti, S. ; Swift, Jonathan J. ; Andrews, J. E. ; et al ( November 2021 , The Astrophysical Journal)

   Abstract We present deep Chandra X-ray observations of two nearby Type Ia supernovae, SN 2017cbv and SN 2020nlb, which reveal no X-ray emission down to a luminosity L X ≲ 5.3 × 10 37 and ≲ 5.4 × 10 37 erg s −1 (0.3–10 keV), respectively, at ∼16–18 days after the explosion. With these limits, we constrain the pre-explosion mass-loss rate of the progenitor system to be M ̇ < 7.2 × 10 −9 and < 9.7 × 10 −9 M ⊙ yr −1 for each (at a wind velocity v w = 100 km s −1 and a radius of R ≈ 10 16 cm), assuming any X-ray emission would originate from inverse Compton emission from optical photons upscattered by the supernova shock. If the supernova environment was a constant-density medium, we would find a number density limit of n CSM < 36 and < 65 cm −3 , respectively. These X-ray limits rule out all plausible symbiotic progenitor systems, as well as large swathes of parameter space associated with the single degenerate scenario, such as mass loss at the outer Lagrange point and accretion winds. We also present late-time optical spectroscopy of SN 2020nlb, and set strong limitsmore »on any swept up hydrogen ( L H α < 2.7 × 10 37 erg s −1 ) and helium ( L He, λ 6678 < 2.7 × 10 37 erg s −1 ) from a nondegenerate companion, corresponding to M H ≲ 0.7–2 × 10 −3 M ⊙ and M He ≲ 4 × 10 −3 M ⊙ . Radio observations of SN 2020nlb at 14.6 days after explosion also yield a non-detection, ruling out most plausible symbiotic progenitor systems. While we have doubled the sample of normal Type Ia supernovae with deep X-ray limits, more observations are needed to sample the full range of luminosities and subtypes of these explosions, and set statistical constraints on their circumbinary environments.« less
4. Luminous Late-time Radio Emission from Supernovae Detected by the Karl G. Jansky Very Large Array Sky Survey (VLASS)

   https://doi.org/10.3847/2041-8213/ac375e  

   Stroh, Michael C. ; Terreran, Giacomo ; Coppejans, Deanne L. ; Bright, Joe S. ; Margutti, Raffaella ; Bietenholz, Michael F. ; De Colle, Fabio ; DeMarchi, Lindsay ; Duran, Rodolfo Barniol ; Milisavljevic, Danny ; et al ( December 2021 , The Astrophysical Journal Letters)

   Abstract We present a population of 19 radio-luminous supernovae (SNe) with emission reaching L ν ∼ 10 26 –10 29 erg s −1 Hz −1 in the first epoch of the Very Large Array Sky Survey (VLASS) at 2–4 GHz. Our sample includes one long gamma-ray burst, SN 2017iuk/GRB 171205A, and 18 core-collapse SNe detected at ≈1–60 yr after explosion. No thermonuclear explosion shows evidence for bright radio emission, and hydrogen-poor progenitors dominate the subsample of core-collapse events with spectroscopic classification at the time of explosion (79%). We interpret these findings in the context of the expected radio emission from the forward shock interaction with the circumstellar medium (CSM). We conclude that these observations require a departure from the single wind–like density profile (i.e., ρ CSM ∝ r −2 ) that is expected around massive stars and/or from a spherical Newtonian shock. Viable alternatives include the shock interaction with a detached, dense shell of CSM formed by a large effective progenitor mass-loss rate, M ̇ ∼ 10 − 4 – 10 − 1 M ⊙ yr −1 (for an assumed wind velocity of 1000 km s −1 ); emission from an off-axis relativistic jet entering our line of sight; ormore »the emergence of emission from a newly born pulsar-wind nebula. The relativistic SN 2012ap that is detected 5.7 and 8.5 yr after explosion with L ν ∼ 10 28 erg s −1 Hz −1 might constitute the first detections of an off-axis jet+cocoon system in a massive star. However, none of the VLASS SNe with archival data points are consistent with our model off-axis jet light curves. Future multiwavelength observations will distinguish among these scenarios. Our VLASS source catalogs, which were used to perform the VLASS cross-matching, are publicly available at https://doi.org/10.5281/zenodo.4895112 .« less
5. The extraplanar type II supernova ASASSN-14jb in the nearby edge-on galaxy ESO 467-G051

   https://doi.org/10.1051/0004-6361/201834972  

   Meza, Nicolás ; Prieto, J. L. ; Clocchiatti, A. ; Galbany, L. ; Anderson, J. P. ; Falco, E. ; Kochanek, C. S. ; Kuncarayakti, H. ; Sánchez, S. F. ; Brimacombe, J. ; et al ( September 2019 , Astronomy & Astrophysics)

   We present optical photometry and spectroscopy of the Type II supernova ASASSN-14jb, together with Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE) integral field observations of its host galaxy and a nebular-phase spectrum. This supernova, in the nearby galaxy ESO 467-G051 ( z  = 0.006), was discovered and followed-up by the all-sky automated survey for supernovae (ASAS-SN). We obtained well-sampled las cumbres network (LCOGTN) B V g r i and Swift w 2 m 1 w 1 u b v optical, near-UV/optical light curves, and several optical spectra in the early photospheric phases. The transient ASASSN-14jb exploded ∼2 kpc above the star-forming disk of ESO 467-G051, an edge-on disk galaxy. The large projected distance from the disk of the supernova position and the non-detection of any H II region in a 1.4 kpc radius in projection are in conflict with the standard environment of core-collapse supernova progenitors and suggests the possible scenario that the progenitor received a kick in a binary interaction. We present analysis of the optical light curves and spectra, from which we derived a distance of 25 ± 2 Mpc using state-of-the-art empirical methods for Type II SNe, physical properties of the SN explosion ( 56 Ni mass, explosionmore »energy, and ejected mass), and properties of the progenitor; namely the progenitor radius, mass, and metallicity. Our analysis yields a 56 Ni mass of 0.0210  ±  0.0025  M ⊙ , an explosion energy of ≈0.25 × 10 51 ergs, and an ejected mass of ≈6  M ⊙ . We also constrained the progenitor radius to be R *  = 580  ±  28  R ⊙ which seems to be consistent with the sub-Solar metallicity of 0.3  ±  0.1  Z ⊙ derived from the supernova Fe II λ 5018 line. The nebular spectrum constrains strongly the progenitor mass to be in the range 10–12 M ⊙ . From the Spitzer data archive we detect ASASSN-14jb ≈330 days past explosion and we derived a total dust mass of 10 −4   M ⊙ from the 3.6 μ m and 4.5 μ m photometry. Using the F U V , N U V , B V g r i , K s , 3.6 μ m, and 4.5 μ m total magnitudes for the host galaxy, we fit stellar population synthesis models, which give an estimate of M *  ≈ 1 × 10 9   M ⊙ , an age of 3.2 Gyr, and a SFR ≈0.07  M ⊙ yr −1 . We also discuss the low oxygen abundance of the host galaxy derived from the MUSE data, having an average of 12 + log(O/H) = 8.27 +0.16 −0.20 using the O 3 N 2 diagnostic with strong line methods. We compared it with the supernova spectra, which is also consistent with a sub-Solar metallicity progenitor. Following recent observations of extraplanar H II regions in nearby edge-on galaxies, we derived the metallicity offset from the disk, being positive, but consistent with zero at 2 σ , suggesting enrichment from disk outflows. We finally discuss the possible scenarios for the unusual environment for ASASSN-14jb and conclude that either the in-situ star formation or runaway scenario would imply a low-mass progenitor, agreeing with our estimate from the supernova nebular spectrum. Regardless of the true origin of ASASSN-14jb, we show that the detailed study of the environment roughly agree with the stronger constraints from the observation of the transient.« less