Radio Emission from the Infrared Tidal Disruption Event WTP14adeqka: The First Directly Resolved Delayed Outflow from a TDE

Christos Panagiotou; Edo Berger; Emil Polisensky; Erin Kara; Harsh Kumar; Kishalay De; Maria Drout; Megan Masterson; Peter K. Blanchard; Raffaella Margutti

REVIEW 3 major objections 4 minor 3 cited by

Radio Emission from the Infrared Tidal Disruption Event WTP14adeqka: The First Directly Resolved Delayed Outflow from a TDE

T0 review · 3 major / 4 minor · reviewed 2026-08-05 · deepseek-v4-flash

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Pith's one-line read A tidal disruption event's radio outflow launched roughly two years after the star was torn apart.

desk verdict A potentially first direct VLBA-resolved delayed TDE outflow, but the abstract leaves the measurement's uncertainties unspecified; deserves a careful referee. read the letter →

arxiv 2508.16756 v1 pith:GGQFCJWI submitted 2025-08-22 astro-ph.HE

Walter W. Golay , Edo Berger , Yvette Cendes , Megan Masterson , Emil Polisensky , Robert L. Mutel , Peter K. Blanchard , Harsh Kumar

show 5 more authors

Raffaella Margutti Maria Drout Christos Panagiotou Kishalay De Erin Kara

This is my paper · ORCID

classification astro-ph.HE

keywords tidaldisruptioneventradioemissionVLBAdelayedoutflowsupermassiveblackholemid-infraredtransientoff-axisjetnon-relativistic

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

This paper reports radio observations of the mid-infrared tidal disruption event WTP14adeqka, a star torn apart by a supermassive black hole. The radio emission rose starting about four years after the infrared discovery, peaked near 6.5 years, and then faded. Very Long Baseline Array images at 8.9 and 9.7 years directly resolve the radio source, which grew from about 0.11 pc to 0.13 pc, implying an expansion velocity of roughly 0.05 times the speed of light. That expansion speed, combined with the light curve, points to an outflow launched about two years after the disruption, not at the moment the star was destroyed. If correct, this rules out an off-axis jet launched at the time of disruption and shows that some tidal disruption events produce delayed, energetic outflows.

What carries the argument

The key measurement is the angular size of the radio source from Very Long Baseline Array imaging at two epochs. Converting the angular size to a physical size using the known distance yields an apparent expansion velocity, and comparing that velocity with the assumption of continuous expansion since disruption yields the launch delay. The radio light curve provides the complementary timing: the onset of bright radio emission years after discovery is what motivated the late-time VLBA observations.

What would settle it

Measure the source at a much lower radio frequency where interstellar scattering is stronger; if the apparent size scales with frequency as expected for scattering, then scattering is significant and the true expansion velocity may be smaller, possibly bringing the launch time back to the disruption epoch.

Watch

Extended reading notes

Core claim

The central finding is that the radio source associated with WTP14adeqka is directly resolved by VLBA observations at two epochs roughly 0.8 years apart. The measured angular size corresponds to a physical radius increase from about 0.11 pc to about 0.13 pc, giving a mean apparent expansion velocity of approximately 0.05c. If the outflow had been launched at the time of disruption, its expected size on these timescales would be much larger, so the observed size implies a delayed launch about two years after the disruption. This direct size measurement rules out the alternative that the radio emission is an off-axis jet launched at the time of disruption, which would have a size of roughly a

Load-bearing premise

The interpretation that the source is expanding at about 0.05c assumes the source distance is accurate and that the measured angular size is not significantly broadened by interstellar scattering along the line of sight.

Editorial extensions

If this is right

If the delayed launch is real, radio monitoring of TDEs must extend for years after the optical or infrared flare, not just months.
The direct resolution rules out an off-axis jet launched at disruption for this object, so any jet must have been delayed or absent.
The outflow energy of about 10^50.7 erg is roughly an order of magnitude higher than typical optical TDE radio outflows, suggesting MIR-selected TDEs may be more energetic.
Future VLBA epochs can distinguish a delayed jet from a quasi-spherical outflow by measuring the source shape and any astrometric motion.
If delayed outflows are common in MIR TDEs, they probe mass accretion and disk formation long after disruption.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

The roughly two-year delay might correspond to the time needed for stellar debris to circularize into an accretion disk and launch a wind or jet, a timescale that can be compared with theoretical disk-formation models.
The absence of an astrometric shift between epochs is consistent with a symmetric or slowly moving outflow; a future observation showing a positional shift would point to a one-sided jet.
If interstellar scattering contributes to the measured size, the intrinsic expansion could be slower; observing the source at multiple radio frequencies would test this directly.
The same delayed-outflow pattern may explain some radio transients observed in other wavebands with no prompt counterpart.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

Dear [Colleague],

Short version: this is a concrete, potentially first-of-kind VLBA resolved-size measurement for a TDE delayed outflow, from a strong team. The abstract alone cannot establish the result, and the stress-test concern about the small angular growth is legitimate. But the paper deserves a careful referee.

What's new: the paper reports two-epoch VLBA observations that directly resolve the radio source of WTP14adeqka, showing a size increase from ~0.11 to ~0.13 pc. If that size change is real, it is the first direct measurement of physical expansion of a delayed TDE outflow, with an expansion velocity of ~0.05c and a likely delayed launch by ~2 years. That is a clean, testable claim and a meaningful step beyond unresolved radio light curve fits. The energy estimate of ~1e50.7 erg and the explicit comparison with the off-axis jet scenario are also useful framing.

The paper does well to present the size growth as a direct measurement rather than a fitted parameter—it is not circularly inferred from a single-epoch fit. That said, the central result is a very small angular change: at ~100 Mpc, 0.02 pc is about 0.04 mas, roughly 4% of the synthesized beam. The abstract gives no error bars on the fitted sizes, no source model, and no discussion of systematic uncertainties. Interstellar scattering would add a resolution-independent size component and could inflate the apparent growth; calibration and uv-coverage differences between the two epochs could also mimic a 20% size increase. The delayed-launch and jet-exclusion conclusions rest entirely on this measurement being real.

None of that is a fatal flaw—these are exactly the things a referee needs to check—but it is the crux. There is also a small internal tension: the abstract quotes a mean expansion velocity of ~0.021c for launch at disruption, while the VLBA size increase implies ~0.05c; I'd like that reconciled.

Bottom line: if the VLBA sizes survive scrutiny, this is a significant result. Right now it is a claim that needs verification, not an established measurement. I'd send it to a referee with VLBI and scattering experience, and I'd want the full data and error analysis before believing the 0.05c expansion. Worth a close read.

Referee Report

3 major / 4 minor

Summary. The paper reports radio observations of the mid-infrared tidal disruption event WTP14adeqka, including a delayed radio rise peaking at ~6.5 years after discovery, multi-frequency radio observations at 8.9 and 9.7 years, and VLBA imaging at the same epochs. The central claim is that the VLBA source size increased from approximately 0.11 pc to 0.13 pc, implying an expansion velocity of ~0.05c and a likely delayed launch by about 2 years after disruption, thereby ruling out an off-axis jet launched at the time of disruption. The authors further infer a mean expansion velocity of ~0.021c for an assumed launch at disruption and an outflow energy of ~10^50.7 erg, concluding that MIR TDEs can launch energetic delayed outflows.

Significance. If the VLBA size increase is robust, this would be an important result: it would be the first directly resolved delayed outflow from a TDE, with implications for the connection between accretion physics, jet launching, and MIR-selected TDEs. The paper also makes a falsifiable prediction that a prompt off-axis jet is excluded and that future VLBA observations can test a delayed jet. The strength of the work lies in direct imaging rather than indirect spectral modeling, and the multi-frequency coverage is appropriate for characterizing the outflow. However, the abstract alone does not provide the quantitative uncertainty analysis needed to certify the central claim, so the significance is currently contingent on the full data presentation.

major comments (3)

[Abstract (VLBA size measurement)] The central claim—that the source size increased from 0.11 pc to 0.13 pc—is reported without uncertainties, source model, or significance test. At the implied distance (order 100 Mpc), this growth is roughly 0.04 mas, only a few percent of a typical VLBA beam at 8 GHz. The source is likely only marginally resolved, so the fitted size could be strongly covariant with the assumed brightness distribution, amplitude calibration, and uv coverage. The abstract should be backed by a table of fitted sizes with statistical errors, a description of the source model, and a comparison of the two epochs' uv coverage and calibration, or the delayed-launch and jet-exclusion conclusions are not secured.
[Abstract (expansion velocity and launch epoch)] The inferred 'mean expansion velocity of ≈0.021c' and 'likely delayed launch by about 2 years' depend on an assumed launch epoch. The text states 0.021c is 'for an assumed launch at the time of disruption', while the 0.05c velocity from the size difference is interpreted as evidence for a delayed launch. This is a model-dependent inference: if the launch epoch is allowed to vary, the same size difference can produce a range of velocities. The paper should present a fit with launch epoch as a free parameter, including confidence intervals and a comparison between a prompt-launch model and a delayed-launch model. Without this, the '2-year delay' is not a measured quantity.
[Abstract (scattering and systematic size contributions)] The conversion from angular size to physical size and expansion velocity assumes that the VLBA size is intrinsic and not broadened by interstellar scattering or source confusion. If scattering contributes a resolution-independent angular size, the apparent size change between epochs could overestimate the intrinsic expansion. The abstract gives no frequency-dependent size check, scatter estimate, or discussion of how scattering was mitigated. This is a load-bearing systematic for the 0.11-to-0.13 pc growth claim, and the full paper must address it quantitatively.

minor comments (4)

[Abstract] The phrase 'no apparent astrometric shift' should be quantified: what astrometric uncertainty is implied, and does the source position agree with the host galaxy position within that uncertainty?
[Abstract] The statement that the radio luminosity is 'about an order of magnitude larger than in typical optical TDEs' would benefit from a reference to the comparison sample and the exact luminosity range used.
[Abstract] The claim that 'MIR TDEs can launch energetic, delayed outflows' is based on a single object; the wording should make clear that this is one case study, with the plural form supported only by the broader sample discussion.
[Abstract] The abstract says VLBA observations were taken 'at the same epochs' as the multi-frequency radio observations; specify the exact dates or time offsets so the reader can assess the simultaneity of the measurements.

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity identified in abstract-level evidence

full rationale

The analysis is based on the abstract only, since the full text was not provided. The central claim is a direct observational measurement: VLBA observations at two epochs resolve the source and show an increase in size from approximately 0.11 pc to 0.13 pc. This is a measured quantity, not a fitted parameter renamed as a prediction. The derived expansion velocity (~0.05c) and the inferred delayed launch (~2 years) are kinematic interpretations of that measured size difference under assumed source distance and scattering properties; such model dependence is not circularity. The phrase 'for an assumed launch at the time of disruption' explicitly labels an assumption rather than smuggling in the conclusion. No equations, fitted parameters, or self-citations are visible in the abstract that would reduce the derivation to its own inputs. Therefore, no significant circularity can be identified at this level of evidence.

Assumptions & free parameters 1 free parameters · 2 assumptions · 0 invented entities

The central result rests on a direct size measurement, but the conversion to velocity and launch delay depends on the assumed distance and the absence of scattering. No new particles or forces are introduced.

free parameters (1)

launch_epoch = assumed at time of MIR discovery (roughly 2018-2019)
Used to convert the observed source size into a mean expansion velocity of 0.021c; the inferred delay of about 2 years depends on this assumption.

assumptions (2)

domain assumption The VLBA angular size translates to a physical size through the TDE's distance.
Physical size in pc depends on the source distance and cosmology; no distance uncertainty is given in the abstract.
domain assumption The radio source is not significantly broadened by interstellar scattering.
Scatter broadening would inflate the apparent source size and bias the expansion velocity and inferred launch delay.

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Cite this review

Pith. "Pith review of Radio Emission from the Infrared Tidal Disruption Event WTP14adeqka: The First Directly Resolved Delayed Outflow from a TDE." pith.science (2026). https://pith.science/paper/GGQFCJWI

@misc{pith2026250816756,
  author       = {Pith},
  title        = {Pith review of: Radio Emission from the Infrared Tidal Disruption Event WTP14adeqka: The First Directly Resolved Delayed Outflow from a TDE},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/GGQFCJWI}},
  note         = {Machine review of arXiv:2508.16756}
}

abstract

We present detailed radio observations of the mid-infrared (MIR) tidal disruption event (TDE) WTP14adeqka. We detect rising radio emission starting $\approx 4$ years after the discovery of the MIR emission (and about 2 years after its peak), peaking at $\approx 6.5$ years and declining thereafter, reminiscent of the delayed radio emission recently identified in optically discovered TDEs. The peak radio luminosity, $\nu L_\nu\approx 2\times 10^{39}$ erg s$^{-1}$, is comparable to the brightest radio emission in optical TDEs. Multi-frequency radio observations at 8.9 and 9.7 years reveal a non-relativistic outflow with a mean expansion velocity of $\approx 0.021c$ (for an assumed launch at the time of disruption) and an energy of $\approx 10^{50.7}$ erg, about an order of magnitude larger than in typical optical TDEs. More importantly, Very Long Baseline Array (VLBA) observations at the same epochs directly resolve the radio source and reveal an increase in size from approximately 0.11 pc to 0.13 pc (with no apparent astrometric shift), corresponding to an expansion velocity of $\approx 0.05c$, and a likely delayed launch by about 2 years. The VLBA size measurements rule out an off-axis jet launched at the time of disruption, which would have an expected size of $\gtrsim {\rm pc}$ on these timescales; the possibility of a delayed jet can be evaluated with future VLBA observations. We conclude that MIR TDEs can launch energetic, delayed outflows. Ongoing radio observations of the full MIR TDE sample will reveal whether this behavior is ubiquitous.

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Forward citations

Cited by 3 Pith papers

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With its projected sensitivity, low-frequency coverage, and VLBI, the SKA would shift tidal disruption event radio studies from a handful of events to hundreds, enabling population-level inference on jets, black-hole ...

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Reviewed August 5, 2026 · model on record in the stance chip above.