An official website of the United States government
Abstract The dynamics and spectral characteristics of supernova ejecta reveal details of the supernova energetics, explosive nucleosynthesis, and evolution of the progenitor. However, in practice, this important diagnostic information is only derived from CCD-resolution X-ray spectra of shock-heated material. If the spectra were to be observed at higher resolution, then important clues to the explosion energetics would be obvious through measurements of bulk Doppler motions and turbulence in the ejecta. Likewise, the unshocked ejecta in supernovae and young remnants are responsible for obscuring the emission from ejecta on the back side of the remnant. In light of these important effects, we present line-of-sight spectral maps of core-collapse supernova remnant models. We explore the bulk Doppler broadening of spectral lines, including line-of-sight effects. We also explore the time-dependent absorption from both shocked and unshocked ejecta. Finally, we discuss how future X-ray missions such as XRISM and Athena will be able to resolve these effects in nearby and extragalactic supernovae and their remnants.
more »
« less
A Physical Model of Delayed Rebrightenings in Shock-interacting Supernovae without Narrow-line Emission
Abstract Core-collapse supernovae can display evidence of interaction with preexisting, circumstellar shells of material by rebrightening and forming spectral lines, and can even change types as hydrogen appears in previously hydrogen-poor spectra. However, a recently observed core-collapse supernova—SN 2019tsf—was found to brighten after roughly 100 days after it was first observed, suggesting that the supernova ejecta was interacting with surrounding material, but it lacked any observable emission lines and thereby challenged the standard supernova-interaction picture. We show through linear perturbation theory that delayed rebrightenings without the formation of spectral lines are generated as a consequence of the finite sound-crossing time of the postshock gas left in the wake of a supernova explosion. In particular, we demonstrate that sound waves—generated in the postshock flow as a consequence of the interaction between a shock and a density enhancement—traverse the shocked ejecta and impinge upon the shock from behind in a finite time, generating sudden changes in the shock properties in the absence of ambient density enhancements. We also show that a blast wave dominated by gas pressure and propagating in a wind-fed medium is unstable from the standpoint that small perturbations lead to the formation of reverse shocks within the postshock flow, implying that the gas within the inner regions of these blast waves should be highly turbulent.
more »
« less
- Award ID(s):
- 2006684
- PAR ID:
- 10350419
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 927
- Issue:
- 2
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 148
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
ABSTRACT Hydrogen-rich Type II supernovae (SNe II) are the most frequently observed class of core-collapse SNe (CCSNe). However, most studies that analyse large samples of SNe II lack events with absolute peak magnitudes brighter than −18.5 mag at rest-frame optical wavelengths. Thanks to modern surveys, the detected number of such luminous SNe II (LSNe II) is growing. There exist several mechanisms that could produce luminous SNe II. The most popular propose either the presence of a central engine (a magnetar gradually spinning down or a black hole accreting fallback material) or the interaction of supernova ejecta with circumstellar material (CSM) that turns kinetic energy into radiation energy. In this work, we study the light curves and spectral series of a small sample of six LSNe II that show peculiarities in their H α profile, to attempt to understand the underlying powering mechanism. We favour an interaction scenario with CSM that is not dense enough to be optically thick to electron scattering on large scales – thus, no narrow emission lines are observed. This conclusion is based on the observed light curve (higher luminosity, fast decline, blue colours) and spectral features (lack of persistent narrow lines, broad H α emission, lack of H α absorption, weak, or non-existent metal lines) together with comparison to other luminous events available in the literature. We add to the growing evidence that transients powered by ejecta–CSM interaction do not necessarily display persistent narrow emission lines.more » « less
-
ABSTRACT A core-collapse supernova is generated by the passage of a shock wave through the envelope of a massive star, where the shock wave is initially launched from the ‘bounce’ of the neutron star formed during the collapse of the stellar core. Instead of successfully exploding the star, however, numerical investigations of core-collapse supernovae find that this shock tends to ‘stall’ at small radii (≲10 neutron star radii), with stellar material accreting on to the central object through the standing shock. Here, we present time-steady, adiabatic solutions for the density, pressure, and velocity of the shocked fluid that accretes on to the compact object through the stalled shock, and we include the effects of general relativity in the Schwarzschild metric. Similar to previous works that were carried out in the Newtonian limit, we find that the gas ‘settles’ interior to the stalled shock; in the relativistic regime analysed here, the velocity asymptotically approaches zero near the Schwarzschild radius. These solutions can represent accretion on to a material surface if the radius of the compact object is outside of its event horizon, such as a neutron star; we also discuss the possibility that these solutions can approximately represent the accretion of gas on to a newly formed black hole following a core-collapse event. Our findings and solutions are particularly relevant in weak and failed supernovae, where the shock is pushed to small radii and relativistic effects are large.more » « less
-
A core collapse supernova occurs when exothermic fusion ceases in the core of a massive star, which is typically caused by exhaustion of nuclear fuel. Theory predicts that fusion could be interrupted earlier by merging of the star with a compact binary companion. We report a luminous radio transient, VT J121001+495647, found in the Very Large Array Sky Survey. The radio emission is consistent with supernova ejecta colliding with a dense shell of material, potentially ejected by binary interaction in the centuries before explosion. We associate the supernova with an archival x-ray transient, which implies that a relativistic jet was launched during the explosion. The combination of an early relativistic jet and late-time dense interaction is consistent with expectations for a merger-driven explosion.more » « less
-
The discovery of a star formed out of pair-instability supernova ejecta would have massive implications for the Population III star initial mass function and the existence of stars over 100 Msun, but none have yet been found. Recently, the star LAMOST J1010+2358 was claimed to be a star that formed out of gas enriched by a pair-instability supernova. We present a non-LTE abundance analysis of a new high-resolution Keck/HIRES spectrum of J1010+2358. We determined the carbon and aluminum abundances needed to definitively distinguish between enrichment by a pair-instability and core-collapse supernova. Our new analysis demonstrates that J1010+2358 does not have the unique abundance pattern of a a pair-instability supernova, but was instead enriched by the ejecta of a low mass core-collapse supernova. Thus, there are still no known stars displaying unambiguous signatures of pair-instability supernovae.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3847/1538-4357/ac4033
