Constraining Type Ia Supernova Progenitors (original) (raw)
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We argue that type Ia supernovae (SNe Ia) are the result of head-on collisions of White Dwarfs (WDs) in triple systems. The thermonuclear explosions resulting from the zero-impact-parameter collisions of WDs are calculated from first principles by using 2D hydrodynamical simulations. Collisions of typical WDs with masses 0.5-0.9 M_Sun result in explosions that synthesize Ni56 masses in the range of 0.15-0.8 M_Sun, spanning the wide distribution of yields observed for the majority of SNe Ia. The robustness of the shock ignition process is verified with a detailed study using a one-dimensional toy model and analytic tools. The late-time (~50 days after peak) bolometric light curve is equal to the instantaneous energy deposition and is calculated exactly, by solving the transport of gamma-rays emitted by the decay of Ni56 using a Monte-Carlo code. All collisions are found to have the same late-time light curves, when normalized to the amount of synthesized Ni56. This universal light cu...
HEAD-ON COLLISIONS OF WHITE DWARFS IN TRIPLE SYSTEMS COULD EXPLAIN TYPE Ia SUPERNOVAE
The Astrophysical Journal, 2013
Type Ia supernovae (SNe Ia), thermonuclear explosions of carbon-oxygen white dwarfs (CO-WDs), are currently the best cosmological "standard candles", but the triggering mechanism of the explosion is unknown. It was recently shown that the rate of head-on collisions of typical field CO-WDs in triple systems may be comparable to the SNe Ia rate. Here we provide evidence supporting a scenario in which the majority of SNe Ia are the result of such head-on collisions of CO-WDs. In this case, the nuclear detonation is due to a well understood shock ignition, devoid of commonly introduced free parameters such as the deflagration velocity or transition to detonation criteria. By using two-dimensional hydrodynamical simulations with a fully resolved ignition process, we show that zero-impact-parameter collisions of typical CO-WDs with masses 0.5 − 1 M ⊙ result in explosions that synthesize 56 Ni masses in the range of ∼ 0.1 − 1 M ⊙ , spanning the wide distribution of yields observed for the majority of SNe Ia. All collision models yield the same late-time (∼ > 60 days since explosion) bolometric light curve when normalized by 56 Ni masses (to better than 30%), in agreement with observations. The calculated widths of the 56 Ni-mass-weighted-line-of-sight velocity distributions are correlated with the calculated 56 Ni yield, agreeing with the observed correlation. The strong correlation, shown here for the first time, between 56 Ni yield and total mass of the colliding CO-WDs (insensitive to their mass ratio), is suggestive as the source for the continuous distribution of observed SN Ia features, possibly including the Philips relation.
Type Ia supernovae and the formation of single low-mass white dwarfs
Astronomy & Astrophysics, 2009
There is still considerable debate over the progenitors of type Ia supernovae (SNe Ia). Likewise, it is not agreed how single white dwarfs with masses less than ~0.5 Msun can be formed in the field, even though they are known to exist. We consider whether single low-mass white dwarfs (LMWDs) could have been formed in binary systems where their companions have exploded as a SN Ia. In this model, the observed single LMWDs are the remnants of giant-branch donor stars whose envelopes have been stripped off by the supernova explosion. We investigate the likely remnants of SNe Ia, including the effects of the explosion on the envelope of the donor star. We also use evolutionary arguments to examine alternative formation channels for single LMWDs. In addition, we calculate the expected kinematics of the potential remnants of SNe Ia. SN Ia in systems with giant-branch donor stars can naturally explain the production of single LMWDs. It seems difficult for any other formation mechanism to account for the observations, especially for those single LMWDs with masses less than ~0.4 Msun. Independent of those results, we find that the kinematics of one potentially useful population containing single LMWDs is consistent with our model. Studying remnant white-dwarf kinematics seems to be a promising way to investigate SN Ia progenitors. The existence of single LMWDs appears to constitute evidence for the production of SNe Ia in binary systems with a red-giant donor star. Other single white dwarfs with higher space velocities support a second, probably dominant, population of SN Ia progenitors which contained main-sequence or subgiant donor stars at the time of explosion. The runaway stars LP400-22 and US 708 suggest the possibility of a third formation channnel for some SNe Ia in systems where the donor stars are hot subdwarfs.
Sub-luminous type Ia supernovae from the mergers of equal-mass white dwarfs with mass ∼0.9M⊙
Nature, 2010
Type Ia supernovae (SNe Ia) are thought to result from thermonuclear explosions of carbon-oxygen white dwarf stars 1 . Existing models 2 generally explain the observed properties, with the exception of the sub-luminous 1991-bg-like supernovae 3 . It has long been suspected that the merger of two white dwarfs could give rise to a type Ia event 4,5 , but hitherto simulations have failed to produce an explosion 6,7 . Here we report a simulation of the merger of two equal-mass white dwarfs that leads to an underluminous explosion, though at the expense of requiring a single common-envelope phase, and component masses of ~0.9 M ʘ . The light curve is too broad, but the synthesized spectra, red colour and low expansion velocities are all close to what is observed for sub-luminous 1991bg-like events.
On Type Ia supernovae from the collisions of two white dwarfs
Monthly Notices of the Royal Astronomical Society: Letters, 2009
We explore collisions between two white dwarfs as a pathway for making Type Ia Supernovae (SNIa). White dwarf number densities in globular clusters allow 10 − 100 redshift 1 collisions per year, and observations by (Chomiuk et al. 2008) of globular clusters in the nearby S0 galaxy NGC 7457 have detected what is likely to be a SNIa remnant. We carry out simulations of the collision between two 0.6 M white dwarfs at various impact parameters and mass resolutions. For impact parameters less than half the radius of the white dwarf, we find such collisions produce ≈ 0.4 M of 56 Ni, making such events potential candidates for underluminous SNIa or a new class of transients between Novae and SNIa.
Signatures of progenitors of Type Ia supernovae
2017
Thermonuclear Supernovae (SNe Ia) are one of the building blocks of modern cosmology and laboratories for the explosion physics of White Dwarf star/s (WD) in close binary systems. The second star may be a WD (double degenerate systems, DD), or a non-degenerated star (SD) with a main sequence star, red giant or a helium star as companion (Branch et al. 1995; Nomoto et al. 2003; Wang & Han 2012). Light curves and spectra of the explosion look similar because a ’stellar amnesia’ (Höflich et al. 2006). Basic nuclear physics determines the progenitor structure and the explosion physics, breaking the link between progenitor evolution, and the explosion, resulting in three main classes of explosion scenarios: a) dynamical merging of two WD and a heating on time scales of seconds (Webbink 1984; Isern et al. 2011), b) surface helium detonations on top of a WD which ignite the central C/O by a detonation wave traveling inwards (Nomoto 1982; Hoeflich & Khokhlov 1996; Kromer et al. 2010); c) co...
On the Progenitors of Type IA Supernovae
Cosmic Chemical Evolution, 2002
Models for Type Ia Supernovae (SNe Ia) are reviewed. It is shown that there are strong reasons to believe that SNe Ia represent thermonuclear disruptions of C-O white dwarfs, when these white dwarfs reach the Chandrasekhar limit and ignite carbon at their centers.
Constraining the Progenitor System of the Type Ia Supernova 2021aefx
The Astrophysical Journal Letters
We present high-cadence optical and ultraviolet light curves of the normal Type Ia supernova (SN) 2021aefx, which shows an early bump during the first two days of observation. This bump may be a signature of interaction between the exploding white dwarf and a nondegenerate binary companion, or it may be intrinsic to the white dwarf explosion mechanism. In the case of the former, the short duration of the bump implies a relatively compact main-sequence companion star, although this conclusion is viewing-angle dependent. Our best-fit companion-shocking and double-detonation models both overpredict the UV luminosity during the bump, and existing nickel-shell models do not match the strength and timescale of the bump. We also present nebular spectra of SN 2021aefx, which do not show the hydrogen or helium emission expected from a nondegenerate companion, as well as a radio nondetection that rules out all symbiotic progenitor systems and most accretion disk winds. Our analysis places str...