{"id":"b4f626c1-b964-4bc3-9003-e66a5773032f","arxiv_id":"2508.16756","paper_version":1,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":7.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":1,"one_line_summary":"VLBA imaging resolves the expanding radio source of TDE WTP14adeqka, measuring an expansion velocity of about 0.05c and implying a delayed launch about two years after disruption.","lead":"Radio observations of the tidal disruption event WTP14adeqka directly resolve an expanding radio source, showing an outflow that appears to have been launched about two years after the star was shredded. This is the first direct size measurement of such delayed radio emission and it rules out an off-axis jet formed at the time of disruption.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The VLBA size difference is load-bearing but the abstract gives no error bars; at plausible distances the 0.02 pc growth is ~0.04 mas, so the reality of the expansion is not yet established.","rationale":"The reader's weakest assumption pointed to distance and interstellar scattering. Those are valid, but the more immediate, load-bearing issue is whether the VLBA size increase itself is statistically significant: the abstract gives no error bars, the angular growth is a tiny fraction of the beam, and the two-epoch comparison can be biased by uv coverage and calibration. This concern does not accuse the authors of an error; it simply notes that the abstract, as the only evidence available, does not establish the central measurement. If the full paper demonstrates a >3σ size increase robust to model choices, the conclusion would stand. Since the reader's verdict was already UNVERDICTED, our concern reinforces that no verdict can be reached from the abstract alone. We therefore leave the verdict unchanged.","tokens_in":831,"tokens_out":9872,"duration_ms":118008,"concrete_test":"Reproduce the VLBA size measurements from the calibrated visibilities: simultaneously fit an elliptical-Gaussian-plus-point-source model to both epochs under a common flux model, and use a bootstrap or Monte Carlo to obtain the posterior on the size difference. Require the 0.11→0.13 pc increase to be >3σ after marginalizing over amplitude calibration factors and after restricting both epochs to a common (u,v) range. If the size difference is not >3σ or changes sign under model variation, the claimed expansion velocity and delayed launch are not supported.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The paper's central claims—expansion at ~0.05c, delayed launch by ~2 years, and the exclusion of an off-axis jet launched at disruption—all rest on the VLBA source size increasing from 0.11 pc to 0.13 pc between epochs at 8.9 and 9.7 years. At a distance of ~100 Mpc, this corresponds to an angular change of ~0.04 mas, about 4% of the VLBA synthesized beam at 8 GHz. The abstract does not report uncertainties on the fitted sizes, the source model used, or a comparison of the two epochs' uv coverage and amplitude calibration. Because the source is only marginally resolved, the fitted size is strongly covariant with the assumed brightness distribution and with calibration errors; a 20% apparent size change could be produced by systematic differences between the two observed epochs rather than by physical expansion. In addition, interstellar scattering would add a resolution-independent angular size, further reducing the inferred intrinsic growth. Without a significance test or a third epoch, the delayed-launch interpretation and the jet-exclusion argument are not secured.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","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.","tokens_in":1128,"tokens_out":2383,"duration_ms":29666,"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":[{"comment":"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.","section":"Abstract (VLBA size measurement)"},{"comment":"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.","section":"Abstract (expansion velocity and launch epoch)"},{"comment":"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.","section":"Abstract (scattering and systematic size contributions)"}],"minor_comments":[{"comment":"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?","section":"Abstract"},{"comment":"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.","section":"Abstract"},{"comment":"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.","section":"Abstract"},{"comment":"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.","section":"Abstract"}],"recommendation":"major_revision","confidential_remarks":"This report is based solely on the abstract because the full text was not provided to the referee. The central VLBA size-change claim is plausible but requires the full quantitative analysis—especially error bars, source modeling, uv-coverage comparison, and scattering discussion—before it can be accepted. I recommend the editor ensure the manuscript contains those details and that the revised version explicitly reports the significance of the size increase."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Dear [Colleague],\n\nShort 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.\n\nWhat'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.\n\nThe 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.\n\nNone 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.\n\nBottom 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.","headline":"A potentially first direct VLBA-resolved delayed TDE outflow, but the abstract leaves the measurement's uncertainties unspecified; deserves a careful referee.","tokens_in":1563,"tokens_out":5000,"would_cite":true,"duration_ms":47967,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"A tidal disruption event's radio outflow launched roughly two years after the star was torn apart.","keywords":["tidal disruption event","radio emission","VLBA","delayed outflow","supermassive black hole","mid-infrared transient","off-axis jet","non-relativistic outflow"],"falsifier":"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.","tokens_in":812,"feed_emoji":"📡","tokens_out":4229,"duration_ms":43503,"temperature":0.7,"pith_summary":"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.","feed_headline":"Shredded star's radio blast began 2 years late, telescope images show","feed_subtitle":"Direct images show the outflow expanding at 5 percent of light speed, ruling out an on-time jet.","key_machinery":"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.","core_discovery":"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","pith_inferences":["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."],"forward_implications":["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."],"supporting_citations":[],"fun_headline_variants":["Radio outflow from shredded star launched 2 years late, images show","TDE's delayed outflow directly imaged at 5% light speed","Delayed jet ruled out: TDE outflow slowly expands at 0.05c","Infrared TDE's delayed outflow directly seen expanding at 0.05c","Direct images catch shredded star's delayed outflow at 0.05c"],"cache_read_input_tokens":2688,"weakest_assumption_plain":"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.","fun_headline_variants_meta":{"raw":{"variants":["Radio outflow from shredded star launched 2 years late, images show","TDE's delayed outflow directly imaged at 5% light speed","Delayed jet ruled out: TDE outflow slowly expands at 0.05c","Infrared TDE's delayed outflow directly seen expanding at 0.05c","Direct images catch shredded star's delayed outflow at 0.05c"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000981,"raw_usage":{"total_tokens":4073,"prompt_tokens":889,"completion_tokens":3184,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":633,"completion_tokens_details":{"reasoning_tokens":3094}},"tokens_in":633,"tokens_out":3184,"duration_ms":23154,"temperature":1.0,"reasoning_tokens":3094,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-05T17:10:00.118348+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"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.","supporting_citations":[],"review_version":1}