{"id":"35f8a0f1-b469-4e9d-8dda-05a93332d1b7","arxiv_id":"2607.04216","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":7.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":5,"one_line_summary":"Quasi-ISOs from recent outer Oort-cloud erosion return with v_∞ ~0.1 km/s and are rare enough that the observed ISO sample remains truly Galactic.","lead":"Objects unbound from the Solar System can return after Galactic orbits as slow quasi-interstellar objects. They are rare and kinematically distinct from true ISOs, so upcoming surveys should see a clean Galactic sample.","discovery_kind":"new_application","skeptic_critique":{"model":"grok-4.5","headline":"No significant objection identified that overturns the distinguishability claim.","rationale":"The paper's central scientific result is not an absolute number of quasi-ISOs but that any such objects are kinematically distinct (v_∞ ~ 0.1 km s^{-1}, specific radiants) and rare enough that they do not contaminate the forthcoming ISO sample. The reader's identification of the normalization tension is accurate and correctly motivates a CONDITIONAL verdict for absolute rates; it does not undermine the strongest claim. Multiple independent model axes already sample the relevant dynamical uncertainties, and all realistic combinations preserve the low-v_∞, low-rate conclusion. No additional internal inconsistency or hidden assumption that would move quasi-ISOs into the true-ISO kinematic regime was found. The recommended concrete test simply tightens the remaining free parameter (ejection speed) without relying on the disputed absolute normalization. Verdict therefore remains CONDITIONAL for the same reasons the reader gave; no adjustment is required.","tokens_in":22578,"tokens_out":628,"duration_ms":7137,"concrete_test":"Re-run the most realistic correlated-heating + flattened-ejection suite with σ_ej raised from 0.1 to 0.5–1 km s^{-1} (still Oort-like) and recompute the importance-sampled v_∞ distribution of Equation 9 at the present epoch; if the median v_∞ remains ≲ 1 km s^{-1} and the rate stays orders of magnitude below the expected true-ISO rate, the distinguishability claim is confirmed independent of normalization.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The reader's weakest assumption (Oort-cloud normalization tension and ad-hoc 1.1 dex scatter in the flyby-loss formula, Sections 3 and 5.2, Figure 5) is real and correctly limits absolute rates. It does not, however, load-bear on the paper's strongest claim. That claim is kinematic and comparative: quasi-ISOs have v_∞ of order 0.1 km s^{-1} and are rare relative to true ISOs, so the observed sample remains Galactic. Across the suite of heating models (white-noise, correlated, none), ejection geometries (isotropic vs. flattened), and erosion histories (exponentials, N23 timing, Monte-Carlo flybys), the re-encounter probability per ISO stays ≲ 3×10^{-14} yr^{-1} and the excess-velocity distribution for realistic (correlated) heating remains peaked near ~0.2 km s^{-1} (Figures 3 and 6). Early, high-velocity ejections are diluted by stream expansion and do not contribute. Absolute-rate uncertainty therefore scales the height of the rate axis in Figure 5 without moving the objects into the kinematic domain of bona-fide ISOs (~ tens of km s^{-1}). The distinguishability result is robust under the paper's own model variations.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.5","summary":"The paper defines quasi-interstellar objects (quasi-ISOs) as planetesimals unbound from the Solar System (primarily via outer Oort-cloud erosion over the past few hundred Myr) that later re-encounter the inner Solar System after orbiting in the Galactic potential. Using suites of test-particle burst simulations in a smooth MilkyWay2014 potential plus white-noise, correlated (Ornstein–Uhlenbeck), or no dynamical heating, the authors compute re-encounter rates via an importance-sampled flux estimator restricted to incoming trajectories and gravitational focusing (Eqs. 6–11). Convolving with exponential, Nesvorný et al. (2023), and Monte-Carlo flyby erosion histories, they conclude that quasi-ISOs are rare (re-encounter probability ≲3×10^{-14} yr^{-1} per ISO), arrive with v_∞ of order 0.1 km s^{-1}, and occupy preferred radiants near the Galactic plane at ℓ≈−45°/+135°, rendering them kinematically distinct from true Galactic ISOs.","tokens_in":22937,"tokens_out":942,"duration_ms":16828,"significance":"If the kinematic conclusions hold, the work cleanly removes a potential local foreground for the ISO samples expected from LSST and similar surveys, confirming that the observed population will be Galactic rather than Solar-System-derived. Strengths include a carefully constructed encounter-rate estimator that correctly excludes outgoing particles, systematic exploration of heating models and ejection geometries (isotropic vs. midplane-flattened), and falsifiable predictions for v_∞ distributions and on-sky radiants (Figs. 6–9). Absolute rates remain order-of-magnitude uncertain, but the distinguishability result is robust across the model suite and does not rely on the absolute normalization.","major_comments":[{"comment":"§3 and Fig. 5: Absolute quasi-ISO rates scale directly with the highly uncertain number of Oort-cloud objects lost in the past ~0.5 Gyr. The two normalizations (present-day long-period-comet rate vs. ISO number density per star) differ by factors of tens, and the Monte-Carlo flyby model requires an ad-hoc σ_H=1.1 dex scatter (Eq. 20) to match the other erosion histories. While this does not move objects into the kinematic domain of true ISOs, the paper’s claim that quasi-ISOs are “intrinsically rare” relative to the expected ISO detection rate should be accompanied by an explicit sensitivity table or shaded band spanning the full normalization range, rather than two discrete point sets.","section":null},{"comment":"§2.1.2 and Eq. 4: The correlated-heating model enforces spatial correlation only between each ISO and the Sun (via β), neglecting correlations among nearby ISOs when they are far from the Sun. Because most returning particles never travel far (Fig. 2), the approximation may be adequate, but a short test with a fully pairwise correlated realization (or an analytic estimate of the neglected term) is needed to confirm that the v_∞ peak near 0.2 km s^{-1} and the re-encounter probability remain unchanged.","section":null}],"minor_comments":[{"comment":"Fig. 1 caption: the acceleration-line scales differ by column; a single colorbar or explicit scale factors would aid comparison.","section":null},{"comment":"§2.2, Eq. 11: the expression for sin θ_c mixes v and v_∞; a brief intermediate step clarifying the hyperbolic angular-momentum identity would improve readability.","section":null},{"comment":"Appendix sky maps (Figs. 8–9): the median lookback time ˜t is useful; adding the corresponding fractional contribution to the total rate would help the reader judge which panels dominate the stacked prediction.","section":null},{"comment":"References: the Hanse et al. (2018) power-law fit is central; a short note on its domain of validity (mass, impact parameter, velocity) would be helpful given the extrapolation to rare slow encounters.","section":null}],"recommendation":"minor_revision","confidential_remarks":"The absolute-rate uncertainty is real but does not undermine the paper’s strongest, kinematic claim; the work is a solid contribution to the ISO literature and fits the journal’s interdisciplinary scope. No novelty or citation concerns."},"author_rebuttal":null,"desk_editor":{"model":"grok-4.5","letter":"This paper does something useful: it defines and quantifies Solar-System ejecta that leave, orbit in the Galaxy, and come back as quasi-ISOs. The main result is clean. Across heating models, ejection geometries, and Oort-cloud erosion histories, re-encounter probabilities stay ≲3×10^{-14} yr^{-1} per object, and for the realistic correlated-heating cases v_∞ peaks near ~0.2 km s^{-1}. Early, high-velocity ejections dilute away. So the observed ISO sample from LSST-era surveys should be Galactic, not a local foreground. That is the claim that matters, and the suite of models supports it.\n\nWhat is new is the combination: burst integrations with white-noise, correlated, and no-heating prescriptions, an encounter-rate estimator that correctly restricts to incoming trajectories and gravitational focusing (Eqs. 6–11), and convolution with exponential, Nesvorný et al. (2023), and Monte-Carlo flyby loss histories. The preferred radiants (Galactic plane near ℓ ≈ −45°/+135° for flattened ejections) and the flat-q, barely-hyperbolic eccentricity distributions follow directly. The math is careful; the citation pattern is appropriate; the authors’ prior stream work is used for context, not as a circular input.\n\nThe soft spot is absolute normalization, not kinematics. The two Oort-cloud normalizations (present-day long-period-comet rate vs. ISO density per star) differ by factors of tens, and the flyby-loss formula is given an ad-hoc 1.1 dex scatter to match other models. That moves the height of the rate axis in Figure 5 without moving objects into the tens-of-km s^{-1} domain of true ISOs. The paper is honest about this in §5.2. No code is shipped, which is a minor practical annoyance for a methods-heavy paper, not a soundness problem.\n\nThis is for people working on ISO demographics, Oort-cloud erosion, or Galactic small-body streams. It deserves a serious referee. I would cite the distinguishability result and the radiant maps. Engage with it.","headline":"Quasi-ISOs are a real, kinematically distinct foreground that is rare and slow; absolute rates are uncertain but the distinguishability claim holds.","tokens_in":23525,"tokens_out":545,"would_cite":true,"duration_ms":5543,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.5","headline":"Solar System ejecta that return as quasi-interstellar objects are rare, slow, and easily told apart from true Galactic ISOs.","keywords":["interstellar objects","Oort cloud","quasi-interstellar objects","Galactic dynamics","dynamical heating","hyperbolic orbits","Solar System small bodies"],"falsifier":"A clear detection of an unbound small body with v_∞ of order 0.1 km s^{-1} arriving near the Galactic-plane intersections at Galactic longitudes ~−45° and +135°, or a measured rate of such objects that exceeds roughly one per decade within 5 au.","tokens_in":23461,"feed_emoji":"☄️","tokens_out":719,"duration_ms":7386,"temperature":0.7,"pith_summary":"Upcoming surveys will find many interstellar objects, raising the worry that some of them are simply Solar System debris that left and came back. This paper asks whether small bodies unbound from the outer Oort cloud can orbit in the Galactic potential and re-enter the inner Solar System on hyperbolic trajectories. Using test-particle bursts launched at different lookback times, evolved under smooth and heated Galactic potentials, and reweighted by several Oort-cloud erosion histories, the authors find that only recent outer-Oort losses (roughly the last few hundred million years, excluding the last ~10 Myr) can produce returners. Those returners, which they call quasi-interstellar objects, arrive with excess speeds of order 0.1 km/s and from preferred directions near the Galactic plane. Because those speeds and sky positions differ sharply from the expected distribution of true interstellar objects, the sample that surveys will collect can be treated as genuinely Galactic. A confirmed quasi-ISO would itself be informative: it would signal either larger Oort losses than currently assumed or a major flyby tens to hundreds of Myr ago that no other tracer can recover.","feed_headline":"Returned Solar System debris is rare and slow","feed_subtitle":"Quasi-ISOs arrive at ~0.1 km/s and will not contaminate the true Galactic interstellar-object sample","key_machinery":"Burst-ejection test-particle integrations of Solar System ISOs, evolved under white-noise, correlated, or no dynamical heating in a Galactic potential, then convolved with Oort-cloud loss-rate models (exponentials, flyby Monte Carlo, and N-body ejection timings) to obtain present-day re-encounter rates and v_∞ distributions.","core_discovery":"Quasi-interstellar objects—Solar System planetesimals that leave through outer Oort-cloud erosion and later re-encounter the Sun—are intrinsically rare, carry hyperbolic excess velocities of order 0.1 km s^{-1}, and arrive from restricted sky patches near the Galactic plane. Early, high-volume ejections are too dispersed to contribute, so the observed interstellar-object sample will remain a clean Galactic population.","pith_inferences":[],"forward_implications":[],"fun_headline_variants":["Quasi-ISOs rare and slow at 0.1 km/s, clean ISO sample","Returned Oort debris re-encounters rare and easy to spot","Solar planetesimals leave and return too rarely to contaminate","Quasi-ISOs from outer Oort cloud: rare, 0.1 km/s, Galactic clean","Early Solar ejections too dispersed; late quasi-ISOs rare and slow"],"cache_read_input_tokens":16512,"weakest_assumption_plain":"The absolute number of returners scales directly with how many outer Oort-cloud objects were lost in the past half-billion years, a quantity that differs by factors of tens depending on whether one normalizes to today’s long-period comets or to the interstellar-object density per star.","fun_headline_variants_meta":{"raw":{"variants":["Quasi-ISOs rare and slow at 0.1 km/s, clean ISO sample","Returned Oort debris re-encounters rare and easy to spot","Solar planetesimals leave and return too rarely to contaminate","Quasi-ISOs from outer Oort cloud: rare, 0.1 km/s, Galactic clean","Early Solar ejections too dispersed; late quasi-ISOs rare and slow"]},"model":"grok-4.5","effort":"low","cost_usd":0.003852,"raw_usage":{"total_tokens":1244,"prompt_tokens":807,"num_sources_used":0,"completion_tokens":109,"cost_in_usd_ticks":38520000,"prompt_tokens_details":{"text_tokens":807,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":328,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":807,"tokens_out":109,"duration_ms":3835,"temperature":1.0,"reasoning_tokens":328,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-11T20:52:53.463932+00:00","model_set":{"reader":"grok-4.5"},"falsifier":"A clear detection of an unbound small body with v_∞ of order 0.1 km s^{-1} arriving near the Galactic-plane intersections at Galactic longitudes ~−45° and +135°, or a measured rate of such objects that exceeds roughly one per decade within 5 au.","supporting_citations":[],"review_version":1}