⚛️ phenomenology

Constraining high-energy neutrinos from tidal disruption events with IceCube high-energy starting events

Using a 12.5-year IceCube high-energy starting events dataset, this study finds no significant correlation between tidal disruption events and high-energy neutrinos, thereby placing stringent constraints on the fraction of jetted TDEs and their associated cosmic ray energies.

Original authors: Mainak Mukhopadhyay, Patrick Wusinich, Kohta Murase

Published 2026-01-30

📖 5 min read🧠 Deep dive

CC BY 4.0

Original authors: Mainak Mukhopadhyay, Patrick Wusinich, Kohta Murase

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 Big Picture: Hunting for Cosmic Ghosts

Imagine the universe is a giant, dark ocean. Sometimes, massive black holes swallow stars whole. These events are called Tidal Disruption Events (TDEs). Think of a TDE like a cosmic blender: a star gets ripped apart by a black hole's gravity, creating a swirling disk of debris.

Scientists suspect that these "cosmic blenders" might be shooting out high-energy particles called neutrinos. Neutrinos are like "ghost particles"—they have no mass, no electric charge, and they can pass through entire planets without stopping. They are incredibly hard to catch.

The paper asks a simple question: Are these TDEs actually shooting neutrinos at us?

The Tools: A Giant Ice Cube and a Guest List

To answer this, the researchers used two main tools:

IceCube: This is a massive detector buried deep in the ice at the South Pole. It's like a giant, 3D camera made of ice and sensors. When a neutrino hits the ice, it creates a tiny flash of light (Cherenkov radiation), which the sensors catch. The researchers used data from 12.5 years of "High-Energy Starting Events" (HESE). These are the "VIP" neutrinos that started their journey inside the detector, making them easier to study.
The TDE Catalog: The researchers also had a guest list of 89 known TDEs. For each one, they knew exactly where it was in the sky (coordinates) and exactly when it happened (time).

The Method: The "Party" Analogy

The researchers wanted to see if the neutrinos and the TDEs were "partying together."

Imagine you are at a huge party (the universe) with 164 guests (the neutrinos) and 89 hosts (the TDEs).

The Hypothesis: If the hosts are throwing the party, the guests should arrive right at the host's house, at the exact time the host starts the music.
The Test: The researchers used a statistical method called "unbinned likelihood analysis." In plain English, they checked every single neutrino to see if it was close in space (near a TDE) and time (around the time of the TDE's peak brightness).

They didn't just look for one perfect match; they stacked all the possibilities together to see if there was a general pattern. It's like checking if, on average, the guests are clustering around the hosts more than you would expect by pure luck.

The Results: No Connection Found

After running the numbers, the answer was clear: No significant connection.

The Finding: The neutrinos were scattered randomly across the sky and time. They didn't seem to care about the TDEs.
The Conclusion: The data is consistent with the "background only" hypothesis. This means the neutrinos IceCube saw are likely just random noise or coming from other sources, not from these specific TDEs. It's like checking a guest list and realizing the guests arrived at random times and random houses, not specifically at the hosts' parties.

The Silver Lining: Setting the Rules

Even though they didn't find a match, the "null result" (finding nothing) is actually very useful. It allows them to set rules for how these cosmic blenders could work, even if we haven't seen them yet.

They looked at two main variables:

$f_{jet}$ (The "Jet" Fraction): What percentage of TDEs actually shoot out powerful jets of energy? (Imagine some blenders have a nozzle, others don't).
$E_{CR}$ (The Energy Budget): How much total energy is being dumped into cosmic rays? (How much "fuel" is in the blender?).

The Constraint:
The researchers calculated that if more than 60% of TDEs had powerful jets ( $f_{jet} > 0.6$ ), those jets would have to be relatively weak (less than $3 \times 10^{53}$ ergs of energy). If the jets were super powerful, we would have seen the neutrinos by now.

Since we didn't see them, we can rule out the scenario where "almost every TDE is a super-powerful jet engine."

Why This Matters

Think of this like a detective narrowing down a suspect list.

Before: "Maybe every TDE is a giant neutrino factory!"
After: "Okay, we know for a fact that TDEs aren't all giant neutrino factories. If they are factories, they are either rare or not very powerful."

This helps theoretical physicists refine their models. They can't just assume TDEs are the main source of high-energy neutrinos; they have to adjust their theories to fit these new limits.

The Future

The paper concludes by saying that with more data coming from better telescopes (like the Vera C. Rubin Observatory) and bigger neutrino detectors (like IceCube-Gen2), we will have a much bigger guest list and a sharper camera. Eventually, we might finally catch a neutrino coming from a TDE, but for now, the "blenders" are keeping their secrets.

Technical Summary: Constraining High-Energy Neutrinos from Tidal Disruption Events with IceCube HESE

Problem Statement
Tidal Disruption Events (TDEs), where stars are shredded by supermassive black holes, are proposed candidates for high-energy neutrino sources. Theoretical models suggest neutrino production can occur in various regions, including relativistic jets (both successful and choked), accretion disks, coronae, and outflows. While previous studies identified potential coincidences between specific TDEs (e.g., AT2019dsg) and neutrino events, recent improvements in IceCube's directional reconstruction have shown that these reconstructed neutrino directions do not align with the TDE locations. Consequently, a statistical approach is required to determine if TDEs, as a population, contribute to the diffuse high-energy neutrino flux. The primary challenge lies in the low statistics of both the observed TDE catalog and the high-energy neutrino dataset, necessitating a robust stacking analysis to constrain the physical parameters governing neutrino production.

Methodology
The authors perform an unbinned maximum likelihood analysis to search for spatial and temporal correlations between the IceCube 12.5-year High-Energy Starting Events (HESE) dataset and a catalog of 89 TDEs.

Data Catalogs:
- TDEs: A sample of 89 TDEs was selected from a catalog of 134 events [73]. The selection criteria required the availability of time-series photometry to determine the time of peak brightness ( $t_{peak}$ ) using a Bayesian Blocks algorithm. The sample spans various redshifts and includes events detected in multiple optical bands (ZTF, ATLAS, ASASSN, etc.).
- Neutrinos: The analysis utilizes 164 HESE events from the IceCube 12.5-year dataset (June 2010 – August 2022). The dataset includes reconstructed arrival directions modeled by an 8-parameter Fisher-Bingham (FB8) distribution to account for anisotropic localization uncertainties.
Likelihood Analysis:
- The analysis employs an unbinned likelihood function (Eq. 3.1) that stacks associations between each TDE and all neutrino events in the temporal and spatial vicinity.
- Signal PDF ( $S_i$ ): Modeled as the product of temporal and spatial components. The temporal component assumes a Gaussian distribution centered at a delay of $\lambda_T = 100$ days relative to the TDE optical peak, with a spread of $\sigma_T = 10$ days, motivated by models of delayed jet launching (e.g., Magnetically Arrested Disk states). The spatial component utilizes the FB8 directional probability density provided by IceCube.
- Background PDF ( $B_i$ ): Assumes a uniform distribution in time (within a $\sim$ 50-day window) and uniform distribution over the sky.
- Test Statistic (TS): Defined as $TS = 2 \log(L(ns)/L(ns=0))$ , where $ns$ is the signal strength parameter. The observed TS ( $TS_{obs}$ ) is compared against a distribution of $TS_{max}$ generated from $10^5$ mock catalogs with randomly generated TDE positions and times to establish significance.
Upper Limits and Signal Injection:
- To constrain physical parameters, the authors generate synthetic TDE catalogs and perform artificial signal injection. They vary two key parameters: the fraction of TDEs harboring intrinsic jets ( $f_{jet}$ ) and the isotropic-equivalent cosmic ray energy ( $E_{CR}$ ).
- Mock catalogs are constructed by selecting a subsample of jetted TDEs based on $f_{jet}$ , calculating expected neutrino yields based on $E_{CR}$ , and injecting signal pairs into the dataset with perfect spatial correlation and temporally correlated delays.

Key Results

Correlation Search: The analysis of the observed data yields a maximum test statistic of $TS_{max} = 0$ at $ns = 0$. The observed data is consistent with the background-only hypothesis, showing no significant spatial or temporal correlation between the 89 TDEs and the 164 HESE neutrinos.
Constraints on Physical Parameters: Using the null result, the authors place upper limits on the parameter space of $f_{jet}$ $f_{j e t}$ and $E_{CR}$ $E_{C R}$ .
- Even with limited statistics, the analysis constrains the region where $f_{jet} \gtrsim 0.6$ and $E_{CR} \gtrsim 3 \times 10^{53}$ erg at greater than 90% confidence level (C.L.).
- For the specific case where all TDEs are neutrino emitters ( $f_{jet} = 1$ ), the isotropic-equivalent CR energy is constrained to $E_{CR} < 2 \times 10^{53}$ erg at 90% C.L.
Theoretical Implications:
- The derived limits constrain the efficiency ( $\epsilon_{CR}$ ) of converting gravitational binding energy into cosmic rays. For a standard $1 M_\odot$ star and $10^8 M_\odot$ black hole, the limits imply $\epsilon_{CR} \lesssim 0.5$ (for $f_{jet}=1$ ) or $\epsilon_{CR} \lesssim 0.75 f_b$ (for $f_{jet} < 0.6$ ).
- The results suggest that while successful, radio-loud jets (which constitute a tiny fraction of TDEs) are unlikely to dominate the diffuse flux, scenarios involving "hidden" winds, choked jets, or isotropic emission from non-jetted TDEs remain viable but are constrained by the energy budget.
- The calculated upper limit on the all-sky diffuse neutrino flux from TDEs is currently weak ( $\sim 10^{-7}$ GeV cm $^{-2}$ s $^{-1}$ sr $^{-1}$ ) compared to the observed IceCube flux, but the authors note this will improve with future data.

Significance and Claims
The paper claims to be the first stacking search correlating the IceCube HESE dataset with a specific catalog of observed TDEs. The primary significance lies in establishing that current data does not support a strong correlation, thereby ruling out models where a large fraction of TDEs ( $f_{jet} \gtrsim 0.6$ ) produce extremely high-energy cosmic rays ( $E_{CR} \gtrsim 3 \times 10^{53}$ erg).

The authors emphasize that their methodology provides a framework to place stringent constraints on TDE physical parameters as statistics improve. They explicitly state that with the advent of the Vera C. Rubin Observatory (LSST), which is expected to detect $\sim$ 1000 TDEs per year, and future neutrino observatories (IceCube-Gen2, KM3NeT, GRAND, etc.), the current limits can be significantly tightened. The paper modestly concludes that while current statistics are limited, the analysis demonstrates the potential to constrain the energy budget and jet fractions of TDEs, offering a path to understanding their role in the high-energy neutrino sky.