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The failed failed-supernova scenario of M31-2014-DS1

Noam Soker

TL;DR

This paper challenges the interpretation of M31-2014-DS1 as a neutrino-driven failed supernova by evaluating the dynamical and radiative consequences of fallback accretion with angular-momentum fluctuations. It argues that intermittent accretion disks and jets would eject most bound material and that rapid radiative cooling would make the outflow energy appear as bright radiation, conflicting with the observed faint fading over a decade. The analysis favors the Type II ILOT scenario, involving dust ejection in a binary interaction, as more consistent with the data, and calls for considering both neutrino-driven and jittering jets explosion mechanism (JJEM) frameworks in CCSN discussions. Overall, the work suggests that long-term fallback-powered emission predicted by some failed-SN models is not supported by the observations of M31-2014-DS1.

Abstract

I examine a recently proposed failed-supernova scenario for the fading of the yellow supergiant event M31-2014-DS1, and find that it requires unlikely fine-tuned parameters to work, if at all. In the failed-supernova scenario, most of the yellow supergiant collapsed to form a black hole. Due to the energy carried by neutrinos from the cooling, collapsing core, gravity decreases, leading to the ejection of a small fraction of the outer envelope, some of which remains bound. The fallback accreted gas possesses large angular-momentum fluctuations due to the pre-collapse envelope convection. The fallback material forms intermittent accretion disks around the black hole that launch jets (or disk wind), which unbind most of the bound material. The failed-supernova scenario for M31-2014-DS1 requires that only <1% of the bound material be accreted by the black hole, but the jets do not shut down the backflow for over 10 years. I find this fine-tuned requirement unlikely. I also find that, due to the rapid radiative cooling of the outflow interaction zone with the outer gas, the expected radiation is about an order of magnitude or more above the observed value. These, as well as earlier challenges raised against the failed-supernova scenario, make the alternative type II intermediate-luminosity optical transient scenario, in which fading is due to dust ejection in a violent binary interaction, more likely. The fading event M31-2014-DS1 does not support the failed-supernova scenario predicted by the neutrino-driven explosion mechanism of core-collapse supernovae.

The failed failed-supernova scenario of M31-2014-DS1

TL;DR

This paper challenges the interpretation of M31-2014-DS1 as a neutrino-driven failed supernova by evaluating the dynamical and radiative consequences of fallback accretion with angular-momentum fluctuations. It argues that intermittent accretion disks and jets would eject most bound material and that rapid radiative cooling would make the outflow energy appear as bright radiation, conflicting with the observed faint fading over a decade. The analysis favors the Type II ILOT scenario, involving dust ejection in a binary interaction, as more consistent with the data, and calls for considering both neutrino-driven and jittering jets explosion mechanism (JJEM) frameworks in CCSN discussions. Overall, the work suggests that long-term fallback-powered emission predicted by some failed-SN models is not supported by the observations of M31-2014-DS1.

Abstract

I examine a recently proposed failed-supernova scenario for the fading of the yellow supergiant event M31-2014-DS1, and find that it requires unlikely fine-tuned parameters to work, if at all. In the failed-supernova scenario, most of the yellow supergiant collapsed to form a black hole. Due to the energy carried by neutrinos from the cooling, collapsing core, gravity decreases, leading to the ejection of a small fraction of the outer envelope, some of which remains bound. The fallback accreted gas possesses large angular-momentum fluctuations due to the pre-collapse envelope convection. The fallback material forms intermittent accretion disks around the black hole that launch jets (or disk wind), which unbind most of the bound material. The failed-supernova scenario for M31-2014-DS1 requires that only <1% of the bound material be accreted by the black hole, but the jets do not shut down the backflow for over 10 years. I find this fine-tuned requirement unlikely. I also find that, due to the rapid radiative cooling of the outflow interaction zone with the outer gas, the expected radiation is about an order of magnitude or more above the observed value. These, as well as earlier challenges raised against the failed-supernova scenario, make the alternative type II intermediate-luminosity optical transient scenario, in which fading is due to dust ejection in a violent binary interaction, more likely. The fading event M31-2014-DS1 does not support the failed-supernova scenario predicted by the neutrino-driven explosion mechanism of core-collapse supernovae.
Paper Structure (4 sections, 7 equations, 1 figure)

This paper contains 4 sections, 7 equations, 1 figure.

Table of Contents

  1. Introduction
  2. The flow properties
  3. Luminosity constraints
  4. Summary

Figures (1)

  • Figure 1: A stellar model of a post-red-supergiant star, a yellow supergiant, which was stripped of most of its hydrogen-rich envelope (from CohenBearSoker20256). The initial stellar mass was $M_{\rm ZAMS}=20 M_\odot$. At the time shown, the total mass is $M_\ast= 9.5 M_\odot$, the total hydrogen mass is $M_{\rm H}=1.6 M_\odot$, the stellar luminosity is $L_\ast=7.9 \times 10^4 L_\odot$, the effective temperature is $T_{\rm eff}=4680 ~\rm{K}$, and its radius is $R_\ast=427 R_\odot$. The blue line is the convective velocity $v_{\rm conv}(r)$, while the red line is the mass $m(r)$.