{"id":"c8d17aef-2d6d-4e27-93e3-3a4d829b4be0","arxiv_id":"2607.25259","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":1,"one_line_summary":"Two microlensing events reveal a pair of roughly Uranus-mass planets orbiting beyond the snow lines of a low-mass M dwarf and a late K dwarf.","lead":"Microlensing surveys spotted two new planets with masses near Uranus's, one orbiting a low-mass M dwarf and one a late K dwarf. Both sit beyond their stars' snow lines, a region where ice-giant cores are expected to form.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"KMT-1160's planetary interpretation is not secure: the binary-source alternative is dismissed using a premise ('can only increase magnification') that is false for flux-weighted binary sources, and no binary-source fit is reported.","rationale":"The reader identified the absence of parallax and prior-dependent Bayesian masses as the weakest assumption, and that is a legitimate concern. However, the more fundamental unresolved step is the dismissal of binary-source models for KMT-2025-BLG-1160. The paper's assertion that a binary-source companion can only increase magnification is not valid for a flux-weighted binary source; a fainter, more off-axis companion can produce a negative residual relative to the best-fit single-lens model. Because KMT-1160's anomaly is a smooth negative dip with no caustic crossing, a binary-source model is a plausible alternative that has not been tested. If it fits, the 'planet' does not exist and all derived physical parameters for that event are moot. This does not invalidate KMT-0975, whose caustic crossings are unambiguous, but it removes one of the two central objects from the paper's claim. The appropriate verdict remains CONDITIONAL: the reader already recommended conditional acceptance, and the condition should now explicitly include a binary-source fit and, if the fit is competitive, an external discriminator. I therefore leave the reader's verdict unchanged, but for a different reason than the one the reader emphasized. Credit is due for the careful light-curve modeling, the resolved caustic crossings in KMT-0975, and the explicit acknowledgment that no parallax was measured. The concrete test I propose directly settles whether the KMT-1160 planetary interpretation is secure.","tokens_in":13557,"tokens_out":22152,"duration_ms":252729,"concrete_test":"Fit a 1L1S+2-source (binary-source) model to the KMT-2025-BLG-1160 photometry (requesting the data from the authors if not public), with free parameters for the secondary-to-primary flux ratio, projected separation, and source trajectory, and compare the best-fit χ² with the close and wide 2L1S planetary solutions. If the binary-source model attains Δχ² ≲ 1 relative to the planetary solutions, the planetary interpretation is degenerate and the reported Uranus-mass planet is not established; if it is disfavored by Δχ² ≫ 10, the concern is resolved.","verdict_should_be":"UNCHANGED","load_bearing_attack":"In §3 the paper excludes the binary-source interpretation for both events with the statement: 'a binary-source companion can only increase the observed magnification, producing positive deviations relative to the standard single-source light curve.' This premise is not generally correct. For a single lens and two sources, the combined magnification is a flux-weighted average of the two individual magnifications, each ≥1. If the fainter companion has a larger impact parameter than the primary, the combined light curve is broader and lower than a single-source model that folds the companion into the source flux, so negative residuals relative to the best-fit 1L1S model are possible. The claim is therefore not a substitute for explicitly fitting a binary-source model. For KMT-2025-BLG-0975, the observed caustic crossings rule out a single-lens binary-source model, so the planet identification there is solid. But KMT-2025-BLG-1160's anomaly is a smooth, purely negative dip with no caustic features and is exactly the regime where a binary-source model can mimic the planetary perturbation. The paper reports no binary-source fit or Δχ² against it. If a binary-source model explains the KMT-1160 light curve comparably, then q ≈ 1.3×10⁻⁴ would not correspond to a planet, and the derived mass M_p ≈ 25 M⊕, the snow-line placement, and the 'Uranus-mass' claim for this event would be unsupported. This concern is more load-bearing than the Bayesian-prior uncertainty because it affects the existence of the planet itself.","agreement_with_reader":"disagree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports two planetary microlensing events from the 2025 bulge season. For KMT-2025-BLG-0975, two resolved caustic crossings yield a unique 2L1S solution with q = 8.6e-4, a measured Einstein radius (θE = 0.108 ± 0.017 mas), and a planet mass of ~30 M⊕ around a low-mass M dwarf or brown dwarf at a projected separation of ~0.8 au. For KMT-2025-BLG-1160, a short negative dip near the peak of a high-magnification event yields close and wide solutions with q ~1.3e-4 and Δχ² = 0.3; only an upper limit on ρ (hence a lower limit on θE) is obtained, and the derived planet mass is ~25 M⊕ around a late K dwarf at ~2.6–3.3 au. The abstract claims both planets are Uranus-mass objects beyond the expected snow lines of their hosts.","tokens_in":13954,"tokens_out":10686,"duration_ms":105096,"significance":"If the KMT-1160 planetary interpretation holds, the paper adds two cold ice giants to the microlensing census, one around an M dwarf and one around a K dwarf, which would be a useful contribution to planet-formation demographics. The KMT-0975 detection is robust: the caustic crossings break the close–wide degeneracy (Δχ² = 267 against wide) and the finite-source effect gives a θE measurement. The Bayesian mass estimates are prior-dominated for both events (no parallax; for KMT-1160 only a θE lower limit), but the uncertainties are honestly reported. The main weakness is that the binary-source alternative for KMT-1160 is not properly excluded, leaving its planetary nature unproven.","major_comments":[{"comment":"The premise that a binary-source companion can only increase the observed magnification is false; the flux-weighted sum of two magnified sources can yield negative residuals relative to a best-fit 1L1S model. For KMT-2025-BLG-0975 the caustic crossings independently rule out a 1L2S model, but for KMT-2025-BLG-1160 the smooth negative dip is exactly the regime where a binary-source model can mimic a planetary perturbation. No 1L2S fit or Δχ² comparison is reported. The authors must fit a 1L2S model to KMT-1160 and demonstrate that the planetary interpretation is preferred; otherwise the derived planet mass, snow-line placement, and 'Uranus-mass' classification for this event are unsupported.","section":"§3, binary-source paragraph"},{"comment":"The statement that both planets lie beyond the snow line is based on a point comparison of the medians of a⊥ and the scaling law asl ≃ 2.7 AU (Mh/M⊙). Given the broad posterior of Mh (e.g., Mh = 0.58+0.35−0.32 M⊙ for KMT-1160) and the unresolved close–wide degeneracy, the posterior probability that a⊥ > asl should be computed and stated. The abstract's wording ('located beyond the expected snow-line distances') is stronger than what the median values alone establish.","section":"§5, Table 5 (snow-line claim)"}],"minor_comments":[{"comment":"The abstract uses 'inner' for KMT-2025-BLG-1160's close solution, while Table 5 uses 'close'; unify the terminology.","section":"Abstract vs. Table 5"},{"comment":"The author list contains LaTeX artifacts such as 'Micha/suppress l' and 'Rados/suppress law'; these should be corrected before submission.","section":"Author list"},{"comment":"In the reference for Kim et al. 2016, 'Lee, C.-U.and Park' is missing a period after 'C.-U.'.","section":"References"},{"comment":"The paper refers to previous studies for the Galactic-model priors but does not specify the mass function, velocity dispersions, or spatial model used. A brief summary or explicit citation of the prior model would improve reproducibility.","section":"Bayesian analysis"}],"recommendation":"major_revision","confidential_remarks":"The binary-source issue is the central obstacle and should be resolved before publication. The authors' citation of Gaudi & Han (2004) as supporting the 'only increase magnification' claim is likely a misreading; that paper is known for discussing binary-source degeneracies with planetary lensing. I recommend requiring a 1L2S fit for KMT-2025-BLG-1160 as a condition for acceptance, and a quantitative posterior assessment of the snow-line placement."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Two new cold ice-giant candidates, but only one is on solid ground. KMT-2025-BLG-0975Lb is convincingly detected: two resolved caustic crossings, a tight mass-ratio measurement, and a clear Δχ² against the wide solution. That event alone makes the paper worth reading. KMT-2025-BLG-1160Lb is the problem.\n\nThe paper dismisses the binary-source interpretation for both events with the statement that a binary-source companion 'can only increase the observed magnification, producing positive deviations.' That is not correct. The combined magnification of two sources is a flux-weighted average; the fainter companion can dilute the peak, yielding a smooth negative dip that looks like a planetary perturbation. KMT-1160's anomaly is exactly that: a purely negative, smooth feature near the peak of a high-magnification event. The paper never fits a 1L2S (binary-source) model or reports a Δχ² against it. Without that test, the mass ratio q ≈ 1.3×10⁻⁴ for KMT-1160 is not established as planetary. The stress-test note is right.\n\nThe rest of the analysis is standard and mostly careful. The Bayesian mass estimates use reasonable Galactic-model priors, but for KMT-1160 they rest on the light-curve interpretation; if the anomaly is a binary source, the inferred 25 M⊕ planet disappears. The snow-line scaling (asl ≈ 2.7 AU × Mh/M⊙) is quoted without a reference – a minor issue. For KMT-0975, the host mass posterior extends into the brown-dwarf regime, which is honestly noted.\n\nBottom line: the KMT-0975 result is a solid addition to the microlensing ice-giant sample. The KMT-1160 result needs a genuine binary-source analysis before it can be trusted. As written, the paper should be sent back for that test. It deserves a serious referee – the data are good, the methodology is standard, and the KMT-0975 detection is secure – but it is not ready as is.","headline":"The KMT-0975 planet is securely detected; KMT-1160's planet claim is not, because the binary-source alternative is dismissed with a false argument and never actually fitted.","tokens_in":14600,"tokens_out":3799,"would_cite":true,"duration_ms":37405,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Gravitational microlensing reveals two Uranus-mass planets orbiting beyond the snow line.","keywords":["gravitational microlensing","exoplanets","Uranus-mass planets","ice giants","snow line","Bayesian analysis","close-wide degeneracy","planetary mass function"],"falsifier":"Resolve the lens and source with high-resolution follow-up imaging after the events fade: if the host of KMT-2025-BLG-0975 is measured to be more massive than roughly 0.3 solar masses, or the host of KMT-2025-BLG-1160 is not a roughly 0.4–0.9 solar-mass K dwarf, the Bayesian-derived masses—and with them the Uranus-mass interpretation—would be ruled out.","tokens_in":13495,"feed_emoji":"🪐","tokens_out":6266,"duration_ms":57838,"temperature":0.7,"pith_summary":"The paper reports that two planetary microlensing events from the 2025 bulge season, KMT-2025-BLG-0975 and KMT-2025-BLG-1160, each host a companion with a mass comparable to Uranus: about 30 and 25 Earth masses. In both systems the projected planet–host separation falls beyond the expected snow-line distance of the host—the radius where water ice can condense—placing the planets in the cold ice-giant regime. This matters because microlensing is one of the few techniques that can detect such planets around faint, low-mass stars at wide separations, and these systems add to the sparse census of cold ice giants. The paper further argues that ice-giant formation can occur around hosts as different as a low-mass M dwarf and a late K dwarf. The masses and distances come from Bayesian analysis constrained by the light-curve observables, since no microlens parallax was measured.","feed_headline":"Microlensing finds two Uranus-mass planets beyond the snow line","feed_subtitle":"Both orbit low-mass stars, adding to the sparse census of cold ice giants beyond the snow line.","key_machinery":"The central machinery is the binary-lens single-source (2L1S) model, in which a foreground star with a planetary companion acts as two gravitational lenses and produces the short anomaly near the peak of a background source's light curve. The model yields the planet-to-host mass ratio q and the normalized separation s; the physical scale is set by the angular Einstein radius θE = θ*/ρ, where ρ is the normalized source radius. When the source crosses a caustic, finite-source effects measure ρ, as in the first event; when it only approaches a caustic, ρ is unconstrained and θE becomes a lower limit. With neither event showing a measurable parallax, Bayesian analysis with Galactic-model priors","core_discovery":"The central claim is that two short-lived anomalies near the peaks of two 2025 microlensing light curves are caused by planetary companions with mass ratios q = 8.6 × 10⁻⁴ and q = 1.3 × 10⁻⁴. For KMT-2025-BLG-0975, two resolved caustic crossings in the anomaly fix the geometry and yield a measured angular Einstein radius θE = 0.108 ± 0.017 mas. For KMT-2025-BLG-1160, a high-magnification event (Amax ≈ 133) shows a purely negative deviation, but finite-source effects are not detected, so only a lower limit θE > 0.20 mas is obtained and a close–wide degeneracy remains (Δχ² = 0.3). Using Bayesian analysis with the measured timescales and Einstein radii, the paper infers planet masses of 29.8 an","pith_inferences":["A testable extension: high-resolution imaging a few years after the events could resolve the lens and source; the measured host mass would independently check the Bayesian masses and, for KMT-2025-BLG-1160, would break the close–wide degeneracy.","If the host of KMT-2025-BLG-0975 actually sits at the brown-dwarf end of its posterior, the system would be a rare planet-brown-dwarf case and the snow-line comparison would be even more extreme.","The broader claim that ice-giant formation is common across host masses is suggestive rather than statistical; combining these detections with other microlensing planets would allow a quantitative test of whether cold ice-giant occurrence depends on host mass.","If the Galactic-model priors overestimate the lens distance, the projected separations could shift inward, but the paper's stated snow-line conclusion remains robust within the quoted uncertainties."],"forward_implications":["The two planets join the microlensing census of cold ice giants, strengthening statistics on how often intermediate-mass planets form beyond the snow line.","The systems show that Uranus-mass planets can form and survive around a low-mass M dwarf and a late K dwarf, not only around solar-type stars.","The inferred snow-line location supports the core-accretion expectation that ice-giant cores grow most efficiently where ices condense.","With next-generation telescopes, these systems are candidates for direct-imaging follow-up that could turn the measured mass ratios into direct planet masses.","For KMT-2025-BLG-1160, either the close or wide solution places the planet beyond the snow line, so the cold-ice-giant conclusion is robust to the degeneracy."],"fun_headline_variants":["Two Uranus-mass planets found beyond the snow line","Microlensing reveals pair of cold ice giants","Uranus-sized exoplanets discovered in 2025 bulge","Snow line crossed: two ice giants by microlensing","Twin ice giants from 2025 microlensing events"],"cache_read_input_tokens":2304,"weakest_assumption_plain":"Neither event gave a direct distance measurement (no microlens parallax), and one event produced only a lower limit on the Einstein ring size, so the planet masses and snow-line placements come from Bayesian priors; if those priors misrepresent the true lens populations, the Uranus-mass and snow-line conclusions could shift.","fun_headline_variants_meta":{"raw":{"variants":["Two Uranus-mass planets found beyond the snow line","Microlensing reveals pair of cold ice giants","Uranus-sized exoplanets discovered in 2025 bulge","Snow line crossed: two ice giants by microlensing","Twin ice giants from 2025 microlensing events"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000238,"raw_usage":{"total_tokens":1530,"prompt_tokens":1110,"completion_tokens":420,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":854,"completion_tokens_details":{"reasoning_tokens":354}},"tokens_in":854,"tokens_out":420,"duration_ms":5144,"temperature":1.0,"reasoning_tokens":354,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-01T02:56:06.867928+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Resolve the lens and source with high-resolution follow-up imaging after the events fade: if the host of KMT-2025-BLG-0975 is measured to be more massive than roughly 0.3 solar masses, or the host of KMT-2025-BLG-1160 is not a roughly 0.4–0.9 solar-mass K dwarf, the Bayesian-derived masses—and with them the Uranus-mass interpretation—would be ruled out.","supporting_citations":[],"review_version":1}