{"id":"9c40be85-8230-4205-bae7-d1ed76a97be4","arxiv_id":"2608.10065","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":7.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":8,"one_line_summary":"A jetted micro-tidal disruption event, with a rapidly spinning stellar-mass black hole disrupting a Sun-like star, can explain the multi-phase light curve of the ultra-long GRB250702B.","lead":"This paper proposes that the longest gamma-ray burst ever seen, GRB250702B, was powered by a jet launched when a stellar-mass black hole ripped apart and swallowed a Sun-like star. It combines computer simulations of the stellar disruption with a jet-stability model to explain the burst's X-ray precursor, seven-hour gamma-ray phase, and weeks-long X-ray tail.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The t=4 h polar α≈2 density profile is the linchpin of the stability threshold, and no later-time or resolution evidence shows that it persists over the week-long emission window.","rationale":"The reader's weakest_assumption identifies essentially the same linchpin: the polar funnel profile and its persistence. I agree with the CONDITIONAL verdict because the paper is a well-posed, physically motivated hypothesis whose central stability calculation rests on a single, untested-in-time density profile, but no internal contradiction forces rejection. A secondary, independent inconsistency is worth noting: with Ṁ_fb=0, the asymptotic integration of Eqs. (3)–(5) gives M_d∝t^{-(2s+1)/3}, not the t^{-(2s+4)/3} printed in Eq. (7); the accretion-rate scaling in Eq. (8) is unaffected, so this appears to be a typo-level error that should be corrected but does not change the central prediction. The headline concern is concrete: if the t=4 h polar α=2 profile flattens or the funnel closes before the prompt phase ends, the claimed stable-jet parameter space collapses, and the specific fit to GRB250702B loses its engine. The proposed resolution/convergence check would settle this directly, and the verdict remains CONDITIONAL pending that check.","tokens_in":25565,"tokens_out":15541,"duration_ms":158102,"concrete_test":"Re-run the AREPO density extraction at every saved snapshot from 4 h through the end of the simulation (extending at least to 7 days if feasible), at the fiducial and 2× mass resolution; at each epoch, re-fit the polar slope α=-d log ρ/d log r over r=1–30 R_sun, measure the funnel half-opening angle, and recompute L_jet,min via Eq. (14). If α stays within 2.0±0.1 and L_jet,min stays below ~3×10^47 erg/s through the last Fermi trigger, the stability concern is resolved; if α falls below ~2 or the threshold rises above 3×10^47, the fiducial point in Fig. 4 moves into the unstable region.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The most load-bearing assumption is that the polar density profile extracted from AREPO at t=4 h (Fig. 2), with slope α=2 and funnel half-opening angle θ_f≈15°, is a fixed property of the debris envelope throughout the entire emission window. Equation (14) makes Λ independent of z exactly at α=2, and Fig. 3's threshold L_jet,min≈3×10^47 erg/s is quoted at that slope and normalization. If the funnel closes over hours-to-days, or if the polar profile flattens (α<2) as ejected and unbound debris re-fills the axis, Λ becomes z-dependent and can fall below the stability threshold; if the normalization rises, L_jet,min rises. The adopted engine point L_jet≈3×10^47 erg/s (magenta star, Fig. 4) sits just above Λ=2, so a factor of only a few in the threshold would move it into the unstable region and remove the minimum-power solution used to match L_γ,iso. The AREPO runs shown stop at ~0.5–1 day and contain no viscosity, magnetic fields, or jet feedback, so they cannot by themselves guarantee that the funnel persists to the week-long tail. This is precisely the point that the deferred GRMHD follow-up in §6.2 addresses, but the §6.1 claim that stability holds throughout the emission window is stronger than the evidence presented.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper proposes that the ultra-long gamma-ray burst GRB250702B, with its day-long soft X-ray precursor, seven-hour prompt gamma-ray emission, and week-long X-ray tail, is powered by a jetted micro-tidal disruption event (micro-TDE). Using 3D hydrodynamic AREPO simulations of a 1 M_sun star disrupted by a 10 M_sun black hole, the authors find that within about a day the debris forms a disk with a low-density polar funnel with density profile rho ~ r^-2 and half-opening angle about 15 degrees. They apply an analytic kink-instability criterion to this profile and conclude that jets with L_jet >~ 10^47 erg/s can propagate stably through the funnel. They then combine a semi-analytic wind-modified viscous disk model with a Blandford-Znajek jet efficiency and free beaming/radiative efficiency parameters to reproduce the observed light curve: a stream-fed precursor before disk formation, a narrowly beamed prompt jet, a steep t^-4 decline during the EP-WXT phase attributed to linear jet widening, and a t^-2 week-long X-ray tail from wind-driven disk spreading. The central claim is that all three phases of GRB250702B come from one jetted micro-TDE engine.","tokens_in":25954,"tokens_out":4118,"duration_ms":40369,"significance":"If the central claim holds, jetted micro-TDEs would be a physically motivated and previously largely unquantified ULGRB engine, and the paper would provide a coherent single-engine interpretation of an extraordinary event. The AREPO simulations are state-of-the-art and the finding of a persistent low-density polar funnel in both grazing and deep encounters is a substantive, interesting result. The application of the Bromberg-Tchekhovskoy stability criterion to the simulated profile is a natural and valuable step, and the three-phase interpretation is creative and observationally grounded. However, the paper's light-curve 'reproduction' is in part a parameterized fit rather than a prediction, and the stability threshold depends on the polar profile persisting well beyond the simulated time window. The claimed establishment of jetted micro-TDEs as a ULGRB engine is therefore somewhat stronger than the evidence currently supports.","major_comments":[{"comment":"The stability threshold L_jet,min ~ 3e47 erg/s and the conclusion that stable propagation holds 'throughout the emission window' rely on the polar density profile remaining rho ~ r^-2 with a ~15 degree funnel for weeks, but the AREPO outputs shown are at t=4 hours (Fig. 2) and t=0.5 day (Fig. 1), and the simulations do not include viscosity, magnetic fields, or jet feedback. Because the adopted engine point in Fig. 4 sits just above Lambda=2, a modest change in the threshold from funnel steepening, closure, or normalization would move it into the unstable region. Please provide later-time or resolution evidence for the funnel's persistence, or explicitly restrict the stability claim to the timescale over which the profile is simulated.","section":"§4.3, Fig. 3, §6.1"},{"comment":"The EP-WXT t^-4 decay is produced by inserting a linear jet-widening law theta_b proportional to t from 0.7 to 2.8 degrees over 4e4 s, with eta_X=0.01 chosen to match the peak luminosity. The widening mechanism is described in §6.2 as phenomenological and deferred to future GRMHD simulations, so the WXT phase is a fit rather than a model prediction. To support the abstract's claim that the model 'reproduces' this phase, the widening law should either be calibrated with a jet propagation simulation or the WXT phase should be explicitly presented as a fit parameterized to match the data.","section":"§5.2.1, Eq. (11)"},{"comment":"The peak luminosities in all three bands are set by adjusting eta_X, eta_gamma, theta_b, a_bullet, r_acc, and s, so the multi-phase 'reproduction' is partially a normalization exercise. The paper would be strengthened by clearly separating the model's genuine predictions--the temporal slopes t^-2 and t^-4, the relative timing of the precursor and prompt phases, and the kink-stability threshold--from the fitted normalizations, and by stating this distinction in the summary and §6.","section":"§5.2, §5.2.1, Fig. 5"}],"minor_comments":[{"comment":"The event name is given as 'GRB250702' in the sentence 'the peak γ-ray isotropic equivalent luminosity of GRB250702 (L_γ,iso~10^51.6 erg/s)', while the rest of the paper uses 'GRB250702B'; please make the name consistent.","section":"§5.2"},{"comment":"The caption states that the solid red line matches the observed luminosity 'for unity radiative efficiency (η_γ=1)', but the dotted lines for lower η_γ are also shown; please clarify in the text or caption that the fiducial solution adopts η_γ=1 and that lower efficiencies require higher jet powers.","section":"Fig. 4 caption"},{"comment":"The code name 'arepo' is sometimes written lowercase in the text; please use a consistent style (e.g., 'AREPO' or 'Arepo') throughout.","section":"General"},{"comment":"The numerical coefficient of the Lense-Thirring precession period is quoted with units 'day' inside the expression; for clarity, please write the prefactor as a dimensionless number times a day, or state the units explicitly in the text.","section":"Eq. (13)"}],"recommendation":"major_revision","confidential_remarks":"The paper is timely and the simulations are a valuable step, but the strength of the claims in the abstract and §6 exceeds what the evidence supports: the funnel-persistence assumption and the phenomenological jet-widening law are load-bearing, and the light-curve match is partly a fit. A revision that tempers the 'establishes' language, adds a sensitivity analysis of the stability threshold to the funnel slope/normalization, and clearly separates predicted from fitted quantities would make the contribution solid and appropriate for the journal."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Read this one: a jetted micro-TDE model for the longest GRB on record, with a new AREPO result that the debris forms a low-density polar funnel with rho ~ r^-2. The funnel result is the genuine advance. The light-curve story is plausible but partly assembled, not predicted.\n\nThe paper's good parts: the 3D hydro sims show both grazing and deep encounters develop a bipolar funnel with rho ~ r^-2 and half-opening angle ~15 degrees at t = 4 hours. The kink-stability application to that profile is clean: at alpha = 2, Lambda is z-independent, so the stability threshold L_jet ~ 3e47 erg/s does not depend on breakout height. The disk-wind accretion model (s = 0.5, M_acc ~ t^-2) and the jet-widening prescription theta_b ~ t producing t^-4 is a neat way to connect the three phases. The authors are honest that the widening is phenomenological.\n\nThe soft spots are real but not fatal. The entire stability argument leans on the t = 4 h funnel persisting through the week-long tail. The sims stop at 0.5-1 day, have no viscosity, magnetic fields, or jet feedback, and the funnel could close or flatten as unbound debris re-fills the axis. If alpha < 2 or the normalization rises, Lambda becomes z-dependent, the threshold moves, and the adopted solution (the magenta star sits just above Lambda = 2) could shift into unstable territory. The \"reproduction\" of the WXT phase is also partly constructed: peak luminosity is normalized via beaming and radiative efficiencies, and the t^-4 decay is inserted as a linear widening law. The choice of beta = 5 is post hoc to match the late-time slope.\n\nThe citation pattern looks fine, and the paper flags the GRMHD follow-up needed to test the funnel's persistence. The overclaim is mild: Section 6.1 says stability holds throughout the emission window, but the evidence only shows a stable funnel at t = 4 h. Readers should treat Section 5 as a scenario, not a confirmed prediction.\n\nI'd send this to a serious referee. With one or two more simulations - later-time AREPO or GRMHD with feedback - the central claim could be strengthened significantly. As is, it is a solid, physically motivated hypothesis that deserves publication with the caveats stated.","headline":"Worth refereeing: the funnel simulation is a real new input, but the funnel's persistence over weeks is load-bearing and not demonstrated.","tokens_in":26470,"tokens_out":2601,"would_cite":true,"duration_ms":25848,"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 jetted micro-tidal disruption event explains all three phases of the longest gamma-ray burst on record.","keywords":["ultra-long gamma-ray burst","micro-tidal disruption event","relativistic jet","X-ray precursor","jet stability","kink instability","Blandford-Znajek mechanism","black hole accretion"],"falsifier":"Run the same hydrodynamic setup for a week or more and measure the polar funnel at late times: if the polar profile steepens to $\\rho\\propto r^{-3}$ or the half-opening angle shrinks below about 10 degrees, the stability threshold rises above the inferred $L_{\\rm jet}\\simeq3\\times10^{47}$ erg s$^{-1}$ and the jet would not survive breakout. Observationally, a late-time X-ray light curve that decays as $t^{-5/3}$ (pure fallback) rather than the predicted $t^{-2}$, or a jet opening-angle evolution that does not saturate near $2.8^\\circ$, would break the model.","tokens_in":25370,"feed_emoji":"🌠","tokens_out":7507,"duration_ms":62467,"temperature":0.7,"pith_summary":"The paper proposes that GRB250702B, the longest gamma-ray burst ever detected, was powered by a jetted micro-tidal disruption event: a spinning 10-solar-mass black hole tore apart a Sun-like star and launched a relativistic jet. It claims that the three observed phases—a soft X-ray precursor about a day earlier, seven hours of episodic gamma-ray emission, and a weeks-long X-ray tail—are one continuous story told by the same engine. The X-ray precursor comes from stream-fed accretion before a disk forms; the prompt burst is a tightly beamed jet escaping through a low-density polar funnel; and the long tail is the disk draining under wind-driven viscous accretion while the jet gradually widens. If the model is right, jetted micro-TDEs become a physically motivated engine for ultra-long GRBs, removing the need for a supernova or an exotic progenitor.","feed_headline":"A shredded star's jet explains the longest gamma-ray burst","feed_subtitle":"A polar funnel in the debris keeps the jet stable; wind-driven accretion and jet widening match all three observed phases.","key_machinery":"The load-bearing object is the low-density polar funnel created by the debris envelope: a bipolar cavity with $\\rho\\propto r^{-2}$ and half-opening angle $\\theta_f\\approx15^\\circ$, extracted from 3D hydrodynamic simulations. Because the product $\\rho_a z_h^2$ is constant when the density slope is $\\alpha=2$, the kink-stability parameter $\\Lambda \\propto [L_{\\rm jet}/(\\rho_a z_h^2 \\gamma_j^2 c^3)]^{1/6}$ becomes independent of height, so a jet of fixed power either stays stable at all radii or fails at all radii. The other key ingredient is the wind-modified viscous disk model, in which disk winds carry away mass with a radial slope $s=0.5$, driving the late-time accretion rate to $\\dot{M}_{\\rm acc}\\propto t^{-2}$, and the jet-widening prescription $\\theta_b\\propto t$ that converts that engine decay into the observed $t^{-4}$ X-ray phase.","core_discovery":"The central claim is that one micro-tidal disruption can produce all observed phases of GRB250702B without repeated stripping, multiple engines, or external-shock afterglow physics. In 3D hydrodynamic simulations of a 1 solar-mass star disrupted by a 10 solar-mass black hole, the debris settles within about a day into a rotationally supported disk surrounded by a quasi-steady envelope with a bipolar low-density funnel along the disk axis; the polar density profile is $\\rho\\propto r^{-2}$ with a half-opening angle of about 15 degrees. That particular slope puts the jet stability parameter $\\Lambda$ exactly at the critical value where it becomes independent of jet-head distance, so a jet with power $L_{\\rm jet}\\gtrsim 10^{47}$ erg s$^{-1}$ remains stable against the kink instability all the way to breakout. The paper then couples this picture to a wind-modified viscous disk model whose accretion rate decays as $\\dot{M}_{\\rm acc}\\propto t^{-2}$, and shows that a jet that widens linearly in time ($\\theta_b\\propto t$) produces the steep $L_{\\rm X,iso}\\propto t^{-4}$ X-ray decline seen by EP-WXT, followed by the $t^{-2}$ tail seen by EP-FXT, Swift, and Chandra. The recommended engine parameters—black hole spin $a_\\bullet\\approx0.9$, beaming angle $\\theta_b\\simeq0.7^\\circ$ widening to $2.8^\\circ$, wind index $s=0.5$—jointly reproduce the observed peak gamma-ray luminosity and the multi-week decay.","pith_inferences":["If jetted micro-TDEs are common, ultra-long GRB rates should trace globular clusters and other dynamical environments more than star-forming regions; a systematic search of Fermi and Einstein Probe events could test this by comparing host-galaxy offsets of ULGRBs with micro-TDE rate predictions.","The jet-widening prescription is purely phenomenological; a direct test would be a GRMHD simulation of jet propagation through the simulated funnel to see whether the lateral expansion indeed follows $\\theta_b\\propto t$ and whether reconnection-driven dissipation produces the same $t^{-4}$ decay.","The same framework may apply to other transients with precursors and slow decays, such as some fast radio bursts or long X-ray flares, where a compact-object disruption is suspected; the wind-modified $t^{-2}$ slope is a distinctive observable fingerprint.","A remaining untested implication is that the quasi-regular roughly 2825-second spacing of the prompt episodes can be produced by debris fallback modulating the jet, as the paper suggests qualitatively; measuring the same periodicity in a future event would give a new probe of the fallback geometry."],"forward_implications":["The same engine can explain the day-long X-ray precursor, the roughly seven-hour prompt gamma-ray episodes, and the weeks-long X-ray tail of GRB250702B, so these phases need not come from separate physical processes.","Jetted micro-TDEs become a physically motivated ULGRB engine: their hours-to-days viscous timescales naturally set ultra-long durations, and their polar funnel geometry allows stable jet breakout for $L_{\\rm jet}\\gtrsim10^{47}$ erg s$^{-1}$.","The model predicts the late-time X-ray decay tracks the wind-modified accretion rate, $L_{\\rm X,iso}\\propto t^{-2}$, once the jet beaming angle saturates at about $2.8^\\circ$; the steep $t^{-4}$ phase is a transient geometric effect of jet widening and should not persist.","Because the stability threshold is lowest for slow, wide jets, the jet is expected to remain stable throughout the entire emission window, including the late low-power phase.","The absence of a supernova and the 5.7 kiloparsec host-galaxy offset become natural rather than problematic features, since micro-TDEs occur in dense stellar environments distributed broadly across galaxies."],"supporting_citations":[{"why":"Supplies the micro-TDE simulation method and fallback-rate construction the paper uses to define the debris envelope and disk.","marker":"Kremer et al. (2022)"},{"why":"Provides the mechanism by which a spinning black hole launches the relativistic jet, linking the accretion rate to the jet power.","marker":"Blandford & Znajek (1977)"},{"why":"Defines the jet stability parameter $\\Lambda$ and the critical ambient density slope $\\alpha=2$ that make the funnel stable.","marker":"Bromberg & Tchekhovskoy (2016)"},{"why":"Extends the kink-instability analysis to magnetically dominated jets, justifying the stability threshold adopted in this work.","marker":"Tchekhovskoy & Bromberg (2016)"},{"why":"Supplies the wind-modified viscous disk evolution equations and the $t^{-2}$ accretion decay that sets the late-time X-ray tail.","marker":"Metzger et al. (2008)"},{"why":"Provides GRMHD wind-slope values ($s\\simeq0.66$–$0.87$) that bracket the adopted $s=0.5$ and motivate the wind prescription.","marker":"Lalakos et al. (2025)"},{"why":"Supplies the Fermi/GBM observations of GRB250702B: duration, episodic structure, variability, redshift, and isotropic gamma-ray luminosity.","marker":"Neights et al. (2026)"},{"why":"Reports the Einstein Probe detection of the soft X-ray precursor and the EP-WXT light curve.","marker":"Cheng et al. (2025)"},{"why":"Provides the EP-FXT/Swift/Chandra X-ray data that the model fits with its late-time $t^{-2}$ tail.","marker":"Eyles-Ferris et al. (2026)"}],"fun_headline_variants":["Shredded star's jet explains longest GRB's three phases","Micro-TDE jet unifies all GRB250702B phases","Longest GRB traced to jet from shredded Sun-like star","Jetted micro-TDE model fits GRB250702B from precursor to decay"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The whole argument leans on the polar funnel maintaining its $\\rho\\propto r^{-2}$ density profile and roughly 15-degree opening angle over the weeks-long emission window; the stability and collimation results hold only for that specific slope, which was extracted from simulations at about four hours post-disruption.","fun_headline_variants_meta":{"raw":{"variants":["Shredded star's jet explains longest GRB's three phases","Micro-TDE jet unifies all GRB250702B phases","Longest GRB traced to jet from shredded Sun-like star","Jetted micro-TDE model fits GRB250702B from precursor to decay"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000258,"raw_usage":{"total_tokens":1776,"prompt_tokens":1331,"completion_tokens":445,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":947,"completion_tokens_details":{"reasoning_tokens":368}},"tokens_in":947,"tokens_out":445,"duration_ms":4525,"temperature":1.0,"reasoning_tokens":368,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-14T04:15:02.853361+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Run the same hydrodynamic setup for a week or more and measure the polar funnel at late times: if the polar profile steepens to $\\rho\\propto r^{-3}$ or the half-opening angle shrinks below about 10 degrees, the stability threshold rises above the inferred $L_{\\rm jet}\\simeq3\\times10^{47}$ erg s$^{-1}$ and the jet would not survive breakout. Observationally, a late-time X-ray light curve that decays as $t^{-5/3}$ (pure fallback) rather than the predicted $t^{-2}$, or a jet opening-angle evolution that does not saturate near $2.8^\\circ$, would break the model.","supporting_citations":[],"review_version":1}