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

The paper argues that the failed-supernova scenario for the fading of M31-2014-DS1 is highly unlikely due to its requirement for improbable fine-tuning and its prediction of radiation far exceeding observations, thereby favoring a binary interaction dust-ejection model instead.

Original authors: Noam Soker

Published 2026-07-27

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CC BY 4.0

Original authors: Noam Soker

Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

The Great Cosmic Vanishing Act

Imagine the universe as a giant, bustling theater where stars are the main actors. Most of the time, when a massive star reaches the end of its life, it puts on a spectacular show called a supernova—a blinding explosion that outshines entire galaxies. But sometimes, the script goes wrong. Instead of a bang, the star might just fizzle out, collapsing silently into a black hole. This is the "failed supernova." It's a mystery that astronomers are desperate to solve because it tells us how black holes are born and why some stars disappear without a trace.

To understand this story, we need to know about two things: neutrinos and accretion disks. Neutrinos are tiny, ghost-like particles that zip through everything; when a star's core collapses, they carry away a massive amount of energy, acting like a cosmic drain that weakens gravity. An accretion disk is a swirling whirlpool of gas that forms around a black hole, like water going down a drain. As this gas spins and heats up, it can shoot out powerful jets, like a garden hose turned up to maximum pressure. The big question is: when a star fails to explode, does it just quietly vanish, or does it put on a messy, energetic show that we should be able to see?

The Case of the Fading Star

In this paper, astronomer Noam Soker investigates a specific event called M31-2014-DS1. This was a yellow supergiant star in the Andromeda galaxy that started to fade away in 2014, leading some researchers to propose it was a "failed supernova." The idea was that the star's core collapsed into a black hole, and the outer layers of the star were gently pushed away by escaping neutrinos, leaving a faint, dimming remnant.

However, Soker argues that this explanation is highly unlikely. He suggests that for this scenario to work, the universe would have to be incredibly lucky, or "fine-tuned," in a way that just doesn't happen in nature.

Here is the problem: When the star's core collapses, the outer gas doesn't just fall straight in. Because the star was churning with convection (like a boiling pot of soup) before it died, the falling gas has a lot of random spin. Soker explains that this spinning gas would naturally form a swirling disk around the new black hole. Just like water spinning down a drain, this disk would launch powerful jets of energy.

Soker does the math and finds that these jets would be like a firehose blasting against the falling gas. In fact, the energy from these jets would be so strong that they would blow away almost all the remaining gas that was supposed to be falling in. He calculates that for the "failed supernova" story to hold up, the jets would have to be incredibly weak—so weak that they only use less than 1% of the available energy to push the gas away, yet somehow still manage to keep the gas from falling in for over 10 years. Soker calls this "fine-tuning," comparing it to trying to balance a pencil on its tip during an earthquake; it's theoretically possible but practically impossible.

Furthermore, Soker points out a second major flaw: the brightness. When the gas from the jets crashes into the surrounding gas, it should heat up and glow very brightly. Because the gas cools down so quickly (in less than a year), all that energy should be released as light. Soker estimates that this process should make the object shine about 10 times brighter than what astronomers actually observed. Since the star is much dimmer than the "failed supernova" model predicts, the model doesn't fit the evidence.

Instead of a failed supernova, Soker suggests that M31-2014-DS1 was likely a violent interaction between two stars, where dust was thrown out to hide the light—a scenario that fits the observations much better. He concludes that this specific event does not support the idea that black holes form quietly through the neutrino-driven mechanism. While he can't say it's impossible with 100% certainty, the odds are so stacked against the failed-supernova idea that it's probably not the right answer for this star.

Problem
This paper examines the "failed-supernova" scenario proposed by De et al. (2026a, 2026b) to explain the fading of the yellow supergiant M31-2014-DS1. In this scenario, the star's core collapses to form a black hole, and a small fraction of the outer envelope is ejected due to neutrino-driven energy loss, while the remainder falls back. The author, Noam Soker, argues that this specific application of the neutrino-driven mechanism to M31-2014-DS1 requires unlikely, fine-tuned parameters to reconcile theoretical predictions with observational data. The paper seeks to demonstrate that the fallback accretion expected in this scenario is inconsistent with the observed luminosity and duration of the event.

Methodology
The author employs a theoretical analysis of the hydrodynamics and angular momentum properties of the fallback material surrounding the newly formed black hole.

Angular Momentum Analysis: The study utilizes a stellar model of a post-red-supergiant (yellow supergiant) with an initial mass of $20 M_\odot$ (from Cohen et al. 2026) to estimate the convective velocity and specific angular momentum ( $j_{conv}$ ) in the pre-collapse envelope. The author calculates the initial radius of the accretion disk ( $R_{d,0}$ ) formed by fallback gas due to stochastic angular momentum fluctuations.
Jet and Wind Dynamics: The paper models the interaction between the fallback material and the black hole, assuming the formation of intermittent accretion disks that launch jets or disk winds. The author calculates the kinetic energy and momentum transfer of these outflows relative to the binding energy of the remaining bound gas.
Radiative Cooling Constraints: The study evaluates the radiative cooling time of the interaction zone between the outflowing gas and the bound envelope. By comparing the cooling time to the dynamical time, the author estimates the fraction of kinetic energy converted into radiation versus kinetic energy of the outflow.
Comparative Analysis: The calculated theoretical luminosities and energy budgets are compared against the observed upper limits and average luminosity of M31-2014-DS1 over a 10-year period.

Key Contributions and Results

Angular Momentum and Disk Formation: The analysis shows that the stochastic specific angular momentum from pre-collapse convection ( $j_{conv} \simeq 7 \times 10^{18} \text{ cm}^2 \text{ s}^{-1}$ ) is sufficient to form an accretion disk at a radius of $R_{d,0} \simeq 1 R_\odot$ . This contradicts the assumption that a "centrifugal barrier" near the horizon would prevent disk formation and efficient jet launching.
Jet Feedback and Accretion Shutdown: The author demonstrates that the jets or disk winds launched by the initial fallback material (within the first year) carry sufficient energy and momentum to expel the majority of the remaining bound gas. Specifically, for typical jet efficiency parameters ( $f_j \simeq 0.01 - 0.1$ ), the outflow would completely shut down further fallback accretion, preventing the sustained activity required by the De et al. (2026b) model.
Luminosity Discrepancy: Due to the rapid radiative cooling of the interaction zone ( $\tau_{cool} \lesssim 0.007$ yr), the kinetic energy of the outflow is efficiently converted into radiation. The calculated average power of the outflow over 10 years is approximately $3.7 \times 10^5 L_\odot$ , which is an order of magnitude (or more) higher than the observed luminosity of M31-2014-DS1.
Fine-Tuning Requirement: To match observations, the failed-supernova scenario would require that the jets expel $>99\%$ of the bound material without completely ejecting it for over 10 years, and that the fraction of accreted mass converted to jet energy be exceptionally low. The author identifies these as "fine-tuned" and atypical parameters for astrophysical objects.

Significance and Claims
The paper concludes that the failed-supernova scenario for M31-2014-DS1 is unlikely because it relies on parameters that are not typical for stellar evolution and accretion physics. The author argues that the event does not support the neutrino-driven explosion mechanism's prediction of failed supernovae. Instead, the findings support the alternative "Type II intermediate-luminosity optical transient" (ILOT) scenario, where fading is caused by dust ejection during a violent binary interaction (as proposed by Beasor et al. 2026). The author asserts that the analysis by De et al. (2026b) does not provide cohesive insights into black hole formation via low-energy explosions, as the required physical conditions are inconsistent with the observed data and standard hydrodynamic expectations. The paper advocates for a balanced community discussion between the neutrino-driven mechanism and the Jittering Jets Explosion Mechanism (JJEM), noting that the latter predicts no failed supernovae.

The Great Cosmic Vanishing Act

The Case of the Fading Star

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