{"id":"7e22fb40-c8cf-426f-a0d9-34d9863ec8f6","arxiv_id":"2508.13145","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":2,"one_line_summary":"New Rossiter-McLaughlin measurements show two hot Jupiters around M dwarfs, TOI-3714 b and TOI-5293 A b, have aligned stellar obliquities, and a toy model suggests Kozai-Lidov migration is most efficient around M dwarfs.","lead":"Astronomers measured the spin-orbit alignment of two hot Jupiters orbiting small red dwarf stars, finding both are well-aligned. This adds to the few such measurements and supports the idea that red dwarfs efficiently straighten tilted planet orbits through tides.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The central RM/obliquity claim is credible, but the model assumes no occulted starspots or plages; since the paper cannot rule out active-region crossings without simultaneous photometry, the quoted lambda values could be biased at the level of their uncertainties.","rationale":"The measurement core is credible: the RM signals are detected at high significance (7.6-7.8 sigma), the MCMC setup adopts physically motivated priors from the discovery papers, and the stellar parameter updates are carefully decontaminated. The paper's own limitation statement identifies the unverified assumption about occulted active regions, and that is indeed the least secure condition for the central claim. The dLW/CRX test is a concrete, data-in-hand way to settle it because SERVAL provides these metrics alongside the RVs; an occulted spot would perturb the line profile in a way that is independent of the RM velocity signal. The secondary concerns (the unknown linear drift in one TOI-5293 transit and the toy-model assumptions in Section 5.4) are real but less load-bearing: the drift is explicitly modeled and the second transit of TOI-5293 anchors the result, while the toy model is labeled as such and accompanied by caveats. If the dLW/CRX check is clean, the aligned-obliquity claim stands; if not, the projected obliquities could be biased at a level comparable to their uncertainties. The reader's CONDITIONAL verdict is therefore appropriate and unchanged.","tokens_in":26678,"tokens_out":24697,"duration_ms":264650,"concrete_test":"Use the MAROON-X differential line width (dLW) and chromatic index (CRX) time series from the same observations: an occulted spot produces a localized in-transit anomaly in dLW (and often CRX) along the planet's chord, which the classical RM model does not predict. Check each of the three transit sequences for a >2-sigma dLW/CRX deviation during transit; if none is found, the spot concern is mitigated. Additionally, inject into the starry model a spot with the largest filling factor allowed by the observed TESS photometric variability (e.g., 0.1-0.5%) at the transit chord and refit the RVs; if the resulting shift in lambda exceeds roughly 10 degrees (about 1 sigma of the quoted posterior), then the aligned values are not robust without simultaneous photometry. This can be done with the public MAROON-X time series and the published TESS light curves.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim is that both RM detections yield well-aligned projected obliquities (lambda = 21+14/-11 and -12+19/-14 deg). The starry forward model assumes a uniform, unspotted stellar disk apart from limb darkening. An occulted starspot or plage produces a localized flux deficit that perturbs the RM anomaly by roughly (spot filling factor) x (spot contrast) x (local rotational Doppler shift). For these very slowly rotating stars (vsini ~1.1 km/s, RM semi-amplitude 29-31 m/s), even a disk-averaged spot contrast of ~0.5% can create a few m/s distortion, i.e. ~10% of the RM amplitude, enough to shift lambda by up to ~10-15 degrees, comparable to the quoted uncertainties. The paper explicitly states in Section 4.2 that it 'cannot reliably assess the occurrence of an occulted AR with our MAROON-X data, which would benefit from simultaneous photometry,' and only asserts that the impact is expected to be negligible based on low activity. No quantitative upper limit on spot filling factor is derived, and the SERVAL activity metrics (dLW, CRX, H-alpha) are not used to test for occulted regions. If a spot was hidden during either transit, the inferred lambda and vsini would be biased, potentially weakening the aligned conclusion.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"This paper presents MAROON-X radial-velocity observations of transits of the hot Jupiters TOI-3714 b and TOI-5293 A b, with the goal of measuring the Rossiter-McLaughlin effect and hence the stellar obliquities of their M-dwarf hosts. The authors report highly significant RM detections (7.6σ and 7.8σ), projected obliquities λ = 21^{+14}_{-11} deg and -12^{+19}_{-14} deg, and deprojected obliquities ψ = 26^{+11}_{-10} deg and 24^{+11}_{-10} deg, concluding that both systems are well-aligned. They also refine the stellar parameters using decontaminated Ks-band photometry, constrain the wide binary orbits with Gaia DR3 astrometry, evaluate the plausibility of Kozai-Lidov migration in each system, and present a toy model comparing the efficiency of KL migration around A, FGK, and early M stars. The paper argues that KL migration is more efficient around early M dwarfs and that the emerging population of aligned HJMD hosts supports efficient tidal obliquity damping in M dwarfs.","tokens_in":26940,"tokens_out":5342,"duration_ms":59160,"significance":"If the measurements are correct, this paper triples the number of hot Jupiters around M dwarfs with a detected RM effect, from one to three, and provides two of the best-sampled RM signals for such systems. The RM detections are statistically strong, the modeling follows standard practice with starry, and the authors are careful to adopt literature priors from the discovery papers. The stellar parameter refinement via Ks-band decontamination and the Gaia astrometric binary fits are useful contributions in their own right. The population-level KL toy model is explicitly labeled as a toy, and the paper includes a candid caveats section. However, the alignment conclusion rests on an assumed spot-free stellar disk, one transit requires a poorly understood linear detrend, and the KL-efficiency claim depends on several unconstrained model assumptions. Given the small sample, the population interpretation should be treated as preliminary rather than as a definitive measurement.","major_comments":[{"comment":"The forward model assumes a uniform, unspotted stellar disk, but the paper states in §4.2 that it cannot reliably assess the occurrence of an occulted active region with MAROON-X data and that simultaneous photometry would be needed. For these slowly rotating stars (vsini ≈ 1.1 km/s) with RM semi-amplitudes of only 29-31 m/s, an occulted spot or plage with a disk-averaged contrast of roughly 0.5% can produce a perturbation of a few m/s, comparable to ~10% of the RM amplitude and enough to shift the inferred λ by about 10-15 degrees, which is comparable to the quoted uncertainties. Because the central claim that both systems are aligned depends on these λ values, I ask the authors to provide a quantitative assessment of this systematic, for example using TESS photometry, the SERVAL activity metrics (dLW, CRX, Hα), or injection-recovery tests with a spotted-star model, or to weaken the alignment claim accordingly.","section":"§4.2, §5.1"},{"comment":"For the first transit of TOI-5293 A b, the model includes a linear detrending slope of -12.6 ± 2.0 m/s/hr whose physical origin is unknown, despite the strong correlation with BERV (ρ = 0.995). Because this transit contributes to the reported λ and vsini, and because a linear slope can partially absorb the curvature of the RM ingress and egress over the 1.94-hour transit, I request a robustness check such as fitting without the slope, fitting with a BERV-correlated model, or comparing the λ and vsini posteriors from the two transits separately. The paper should also justify why a single linear term is preferred over higher-order or wavelength-dependent systematics.","section":"§4.1, Table 2"},{"comment":"The population-level conclusion that KL migration is more efficient around early M dwarfs and can fully account for the HJMD occurrence rate rests on f_pps = f_in-situ = 0, a fixed binary suppression factor S_bin = 0.3, and f_misaligned = 0.368 from an isotropic mutual-inclination distribution. Under these assumptions, f_HJ/f_HJ,pred is a ratio of observed occurrence rates to an assumed KL contribution, not a physically measured efficiency. The caveats in §5.4.3 are welcome, but the abstract and §6 state the KL-efficiency result more strongly than the model supports. I recommend adding a sensitivity analysis that varies S_bin and relaxes f_pps = 0 (or uses an a-dependent multiplicity treatment), or explicitly demoting these statements to a speculative interpretation in the abstract and conclusions.","section":"§5.4.2, Eq. (5)"}],"minor_comments":[{"comment":"The title contains a typo: 'F ormation' should be 'Formation'.","section":"Title"},{"comment":"The section heading 'Kozi-Lidov migration' should be 'Kozai-Lidov migration'.","section":"§5.4.3"},{"comment":"The formatting of the TOI-5293 A rows for v0 and m, with upper and lower values for different transits, is ambiguous; please label the rows or add a footnote so the reader can tell which value corresponds to which transit.","section":"Table 2"},{"comment":"The shaded in-transit windows are not labeled with the transit times; adding tick labels or annotation would make the figure easier to interpret.","section":"Figure 1"},{"comment":"The deprojected obliquity ψ depends on the literature rotation period Prot through i⋆, but the text does not propagate the possible systematic error in Prot; a brief discussion of how ψ changes for the 1σ range of Prot would be helpful.","section":"§5.2"}],"recommendation":"major_revision","confidential_remarks":"The two RM detections and the stellar parameter work are likely to be valuable and publishable. My main concern is that the population-level KL interpretation in §5.4, while clearly labeled as a toy model, is presented in the abstract and conclusions with more certainty than the assumptions justify. The spot-contamination and detrending issues can likely be addressed with additional analysis or softened language, so I would support publication after these revisions."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The useful thing in this paper is the measurements. TOI-3714 b and TOI-5293 A b become only the second and third hot Jupiters around M dwarfs with an RM detection, and both look aligned. The RM signals are strong (7.6 and 7.8 sigma), the modeling is standard starry with sensible priors from the discovery papers, and the time series are included as CSV files in the arXiv source. Credit where due: the authors also refine the stellar parameters with dilution corrections and put Gaia astrometry to work on the binary orbits. Their treatment of the odd linear drift in the first TOI-5293 transit is honest: they find a strong BERV correlation, fit a slope, and let the other transits constrain it.\n\nThe soft spots are real but mostly minor. The starspot/plage issue is the one I would want addressed. The starry model assumes a uniform disk, and the paper admits it cannot assess an occulted active region without simultaneous photometry. For vsini of about 1 km/s and RM amplitudes near 30 m/s, a small spot crossing can shift lambda by 10-15 degrees, comparable to the quoted uncertainties. That does not overturn the aligned conclusion, since both systems are consistent with zero and are low-activity, but it means the individual lambda values are not as clean as the error bars suggest. A quantitative upper limit on spot filling factor, even from the SERVAL activity metrics, would tighten this. Second, the deprojected psi values rely on photometric rotation periods and inferred stellar inclinations, so the roughly 10 degree uncertainties there are believable but not hard. Third, the first TOI-5293 transit's detrending slope has an unknown physical origin; minor, because the second transit agrees.\n\nThe KL toy model is the weakest link. The efficiency numbers depend on setting planet-planet scattering and in-situ formation to zero, choosing S_bin = 0.3, and assuming an isotropic mutual inclination distribution. The authors list these caveats, and I believe them. But the conclusion that KL migration can fully account for HJMDs is stronger than the toy model supports. That claim should be softened or more heavily conditioned.\n\nCitation pattern looks fine. This is a paper for the obliquity and hot Jupiter formation communities. It deserves a serious referee; I would send it to peer review and ask for the spot-occultation caveat to be quantified or the KL claim softened.","headline":"The two new RM detections are credible and genuinely useful; the KL population toy model is the softest part and should be framed as speculation.","tokens_in":27522,"tokens_out":2326,"would_cite":true,"duration_ms":26179,"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":"Two more hot Jupiters around M dwarfs orbit aligned with their stars","keywords":["hot Jupiters","M dwarf stars","stellar obliquities","Rossiter-McLaughlin effect","Kozai-Lidov migration","tidal damping","radial velocity","binary stars"],"falsifier":"Re-observe a transit of TOI-3714 b or TOI-5293 A b with simultaneous high-precision space photometry and high-resolution spectroscopy: a spot-crossing anomaly in the light curve overlapping the Rossiter-McLaughlin sequence would break the clean-signal assumption and could shift $\\lambda$; alternatively, one additional old hot-Jupiter-hosting M dwarf with a short tidal-damping timescale and $\\psi \\gtrsim 40^\\circ$ would contradict the claim that M dwarfs efficiently align their hot Jupiters.","tokens_in":26459,"feed_emoji":"🪐","tokens_out":13934,"duration_ms":134147,"temperature":0.7,"pith_summary":"Hot Jupiters, giant planets on orbits of a few days, are two to three times rarer around small, cool M dwarf stars than around Sun-like stars, suggesting a different formation pathway. The paper reports the second and third detections of the Rossiter-McLaughlin effect for hot Jupiters around M dwarfs, using transits of TOI-3714 b and TOI-5293 A b observed at high spectral resolution. Both measurements are consistent with aligned stellar obliquities: $\\lambda = 21^{+14}_{-11}{}^\\circ$ and $-12^{+19}_{-14}{}^\\circ$. If these systems are representative, the emerging sample of aligned hot-Jupiter hosts supports the view that M dwarfs, with their deep convective envelopes, tidally realign misaligned orbits produced by high-eccentricity migration.","feed_headline":"Two more hot Jupiters orbit M dwarfs in step with their stars","feed_subtitle":"RM detections bring the M-dwarf hot Jupiter sample to three aligned systems, pointing to tidal taming.","key_machinery":"The central mechanism is the Rossiter-McLaughlin effect, the anomalous radial-velocity distortion produced when a transiting planet occults different Doppler-shifted parts of the rotating stellar disk; its shape encodes the sky-projected obliquity $\\lambda$. The forward model is computed with a spherical-harmonic-based stellar surface code, fitting $v\\sin i_\\star$, $\\lambda$, velocity offsets, jitter, and linear trends while adopting orbital and transit priors from each planet's discovery paper. Deprojected obliquities $\\psi$ follow from the geometric relation $\\cos\\psi = \\cos i_\\star \\cos i_p + \\sin i_\\star \\sin i_p \\cos\\lambda$, with stellar inclinations inferred probabilistically from $v\\sin i_\\star$, rotation periods, and radii. The dynamical context comes from Kozai-Lidov oscillations, a secular angular-momentum exchange between a planet and a wide binary companion that cycles eccentricity and mutual inclination, and from tidal obliquity damping timescales computed from convective-zone masses.","core_discovery":"Measured through the Rossiter-McLaughlin effect, the projected spin-orbit angles of TOI-3714 b and TOI-5293 A b are $\\lambda = 21^{+14}_{-11}{}^\\circ$ and $-12^{+19}_{-14}{}^\\circ$, with deprojected obliquities $\\psi = 26^{+11}_{-10}{}^\\circ$ and $24^{+11}_{-10}{}^\\circ$; both are consistent with well-aligned orbits. The signals are detected at $7.6\\sigma$ and $7.8\\sigma$, establishing these as just the second and third hot Jupiters around M dwarfs with a Rossiter-McLaughlin detection. The paper argues that because a wide binary companion in each system can drive Kozai-Lidov oscillations on timescales far shorter than the system ages, while the stellar tidal damping timescales are about $10^3$\\,--\\,$10^4$ years, the alignment is naturally explained if these planets once had high eccentricities and inclinations that were later damped. A population-level toy model adds that Kozai-Lidov migration is more efficient around early M dwarfs than around A or FGK stars and can by itself account for the observed hot Jupiter occurrence rate around M dwarfs.","pith_inferences":["This reading implies that a genuinely misaligned hot-Jupiter-hosting M dwarf, if found, would most plausibly be young or have an unusually long damping timescale; age and stellar mass should therefore correlate with obliquity in a larger sample.","A direct test of the main systematic worry is available: simultaneous space-based photometry during a future transit would reveal occulted starspots, whose absence is currently assumed rather than demonstrated.","The toy model's neglect of in-situ formation and planet-planet scattering around M dwarfs could be tested by searching for cold Jupiter companions and inner planet populations in these systems; a firm detection of either would shift some of the inferred Kozai-Lidov efficiency to other channels.","The mild $2\\sigma$ offsets in $\\psi$ might sharpen into real misalignments if stellar rotation periods or radii are revised, so independent rotation measurements would discriminate between true alignment and a slight viewing-geometry effect."],"forward_implications":["Together with TOI-4201 b, all three hot Jupiters around M dwarfs with a Rossiter-McLaughlin detection now have obliquities consistent with zero, giving the first empirical alignment sample for this population.","The measured tidal damping timescales, roughly $10^3$ to $10^4$ years, are orders of magnitude shorter than the system ages, so aligned orbits are the expected endpoint even if the planets arrived via high-eccentricity migration.","The toy model yields Kozai-Lidov hot Jupiter formation efficiencies of $0.16^{+0.12}_{-0.06}$, $0.65^{+0.14}_{-0.12}$, and $1.01^{+0.42}_{-0.36}$ for A, FGK, and early M stars, implying the channel is fully capable of producing the M-dwarf hot Jupiter population.","The elevated multiplicity fraction among hot-Jupiter-hosting M dwarfs, $0.47\\pm0.16$ versus $0.28\\pm0.08$ for field M dwarfs, is consistent with a binary-driven formation route.","If tidal damping is as efficient as these numbers suggest, future Rossiter-McLaughlin measurements of other hot-Jupiter-hosting M dwarfs should continue to find aligned systems rather than a scattered obliquity distribution."],"supporting_citations":[{"why":"Discovery paper for TOI-3714 b; supplies the orbital and transit priors used in the RM fit.","marker":"C22"},{"why":"Discovery paper for TOI-5293 A b; supplies the orbital and transit priors used in the RM fit.","marker":"C23"},{"why":"Previous RM detection for TOI-4201 b, the only earlier hot-Jupiter-M-dwarf measurement and the direct comparison point.","marker":"T. Gan et al. 2024"},{"why":"Spherical-harmonic stellar surface code used to compute the classical RM effect model.","marker":"R. Luger et al. 2019"},{"why":"Supplies the template-matching radial-velocity extraction method used on the observed spectra.","marker":"M. Zechmeister et al. 2018"},{"why":"Provides the probabilistic method for converting $v\\sin i_\\star$ and rotation period into stellar inclination $i_\\star$ for deprojection.","marker":"K. Masuda & J. N. Winn 2020"},{"why":"Supplies the population-level eccentricity-obliquity context and the tidal calibration constant used in the damping timescale.","marker":"M. Rice et al. 2022"},{"why":"Source of the DR3 astrometry used to fit the wide binary orbits and infer minimum mutual inclinations.","marker":"Gaia Collaboration et al. 2023"},{"why":"Gives the binary suppression factor for planet occurrence used in the toy model of Kozai-Lidov migration efficiency.","marker":"M. Moe & K. M. Kratter 2021"}],"fun_headline_variants":["Two Hot Jupiters Around M Dwarfs Are Aligned, MAROON-X Shows","M Dwarf Hot Jupiters Stay Aligned, Shedding Light on Formation","Aligned Orbits of Two Hot Jupiters Hint at Tidal Damping","Rare Aligned Hot Jupiters Around M Dwarfs Constrain Formation"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing assumption is that no occulted starspot or plage crossed the stellar disk during either transit; a hidden active region would distort the Rossiter-McLaughlin shape and bias the inferred obliquity, and the paper cannot rule this out without simultaneous photometry.","fun_headline_variants_meta":{"raw":{"variants":["Two Hot Jupiters Around M Dwarfs Are Aligned, MAROON-X Shows","M Dwarf Hot Jupiters Stay Aligned, Shedding Light on Formation","Aligned Orbits of Two Hot Jupiters Hint at Tidal Damping","Rare Aligned Hot Jupiters Around M Dwarfs Constrain Formation"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000264,"raw_usage":{"total_tokens":1747,"prompt_tokens":1234,"completion_tokens":513,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":850,"completion_tokens_details":{"reasoning_tokens":422}},"tokens_in":850,"tokens_out":513,"duration_ms":5940,"temperature":1.0,"reasoning_tokens":422,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-15T17:15:03.207545+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Re-observe a transit of TOI-3714 b or TOI-5293 A b with simultaneous high-precision space photometry and high-resolution spectroscopy: a spot-crossing anomaly in the light curve overlapping the Rossiter-McLaughlin sequence would break the clean-signal assumption and could shift $\\lambda$; alternatively, one additional old hot-Jupiter-hosting M dwarf with a short tidal-damping timescale and $\\psi \\gtrsim 40^\\circ$ would contradict the claim that M dwarfs efficiently align their hot Jupiters.","supporting_citations":[],"review_version":1}