New regimes in the observation of core-collapse supernovae

Abstract

Core-collapse Supernovae (CCSNe) mark the deaths of stars more massive than about eight times the mass of the sun (M ) and are intrinsically the most common kind of catastrophic cosmic explosions. They can teach us about many important physical processes, such as nucleosynthesis and stellar evolution, and thus, they have been studied extensively for decades. However, many crucial questions remain unanswered, including the most basic ones regarding which kinds of massive stars achieve which kind of explosions and how. Observationally, this question is related to the open puzzles of whether CCSNe can be divided into distinct types or whether they are drawn from a population with a continuous set of properties, and of what progenitor characteristics drive the diversity of observed explosions. Recent developments in wide-field surveys and rapid-response followup facilities are helping us answer these questions by providing two new tools: (1) large statistical samples which enable population studies of the most common SNe, and reveal rare (but extremely informative) events that question our standard understanding of the explosion physics involved, and (2) observations of early SNe emission taken shortly after explosion which carries signatures of the progenitor structure and mass loss history. Future facilities will increase our capabilities and allow us to answer many open questions related to these extremely energetic phenomena of the Universe.We focus this short review on a few open questions which are being tackled by new facilities for quick discovery and rapidresponse followup, as well as for studying CCSNe in large numbers. For a more exhaustive review of the field see recent compilations such as the Handbook of Supernovae [1]. The CCSN Classification LandscapeSN classification has been a challenge since the 1940's [2], but especially recently, as innovative surveys have brought a large increase of new and debated types. Classification schemes are important as physically motivated ones can give crucial insight into the explosion physics and stellar evolution pathways that lead to the different kinds of important explosions.The classical classification scheme [e.g., 3, 4] relies mostly on spectra and has two main types: Type I SNe (SNe I) which do not show hydrogen lines, and Type II SNe (SNe II) which do.In Figure 1 (left panel), we present spectra around peak brightness of the main CCSN classes. Among them, SNe II are perhaps the most heterogeneous class with a large range of observed photometric and spectroscopic properties. Because of this diversity, they can be further divided into several subclasses. The first historical subclassification was based on the light curve shape: SNe showing a linear decline (in magnitudes) in their light curve were named SNe IIL, while SNe showing a quasiconstant luminosity or a plateau for several weeks were called SNe IIP [13]. Later it was discovered that Type IIP and IIL SNe can also be distinguished by a subtle difference in their spectra, with SNe IIP showing deeper absor...

SN2019dge: A Helium-rich Ultra-stripped Envelope Supernova

“…Its early lightcurve evolution is slower than iPTF14gqr, but similar to iPTF16hgs and several other stripped envelope SNe displaying double-peaked light curves (e.g., see Figure 2 of Fremling et al 2019). Their first peaks have been modeled by cooling emission from an extended envelope around the progenitor after the core-collapse SN (CCSN) shock breaks out (Modjaz et al 2019). After ∼8 days past explosion, T bb flattens to 6000±1000 K, similar to the behavior of normal SNe Ibc at a much later phase (∼30 days after explosion, Taddia et al 2018).…”

Observational properties of extreme supernovae

“…A second key window in the spectral evolution is when SLSNe have spectra similar to their normal luminosity counterparts, but somewhat delayed ( [75]) such as Fe II multiplet λλ4924, 5018, 5169, Na ID and Balmer lines, as well as a high-velocity H feature [76,77]. Generally speaking, during the photospheric phase, SLSNe II temperatures derived from blackbody fits are slightly lower and have a slower evolution with respect to those of SLSNe I [21].…”

“…Nevertheless, despite these objects showing a fast rise and decline (see Fig. 4 for some examples), the majority of them can (and have been) explained with the final outcome of a massive stripped star or a thermonuclear explosion (Review Articles by Jha, Maguire and Sullivan on thermonuclear SNe [100] and Modjaz, Gutierrez and Arcavi on core-collapse SNe [75]) as also hinted by their position in the phase-luminosity diagram (Fig. 1), which is below the lines representing the maximum possible luminosity from a standard SN explosion.…”

Asteroseismology of High-Mass Stars: New Insights of Stellar Interiors With Space Telescopes

“…The lives and energetic deaths of massive stars, i.e., those with birth masses larger than ∼8 times that of the Sun (8 M ⊙ )-play a pivotal role in shaping the Universe (Maeder and Meynet, 2000;Maeder, 2009;Kippenhahn et al, 2012;Langer, 2012). Massive stars were amongst the first stars in our Universe (Bromm and Larson, 2004;Bromm et al, 2009), and are progenitors of core-collapse supernovae and gamma-ray bursts (Heger et al, 2003;Smartt, 2009;Tanvir et al, 2009;Modjaz et al, 2019). The properties of massive stars allow them to be observed at large distances (see e.g., Stark, 2016), hence allow us to study the early epochs of the Universe including the re-ionization of the Universe and the formation of the first galaxies (Bromm and Larson, 2004;Robertson et al, 2010).…”