{"id":"c3d4f07c-59bc-4dcd-a394-92c1ebe339c0","arxiv_id":"2501.05615","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":5,"one_line_summary":"Seven first-time projected stellar obliquities, an updated measurement for HAT-P-41b, four true obliquities, and revised minimum ages for TOI-2046 and Qatar-4 are derived from archival HARPS/HARPS-N data.","lead":"Astronomers used archival HARPS and HARPS-N spectra of eight hot Jupiter systems to measure whether the planets' orbits are aligned with their host stars' spins. They found one clearly tilted orbit and revised the ages of two supposedly young systems, which affects how those systems fit into planet migration theories.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"TOI-2046's true obliquity (psi = 42 deg) depends on an assumed 4.05 d rotation period; a different or non-rotational origin for the periodicity would remove the misaligned-orbit claim.","rationale":"The paper's primary contribution is a set of projected obliquities from R-M modeling. These measurements are the product of a standard, well-established methodology and are likely sound; the reported lambdas are reasonable and the MCMC diagnostics are good. The most load-bearing part of the paper's central claim is the true (3D) obliquity of TOI-2046, which is a headline result in the abstract and Section 4.1. That measurement is entirely dependent on interpreting a 4.05 d TESS periodicity as the stellar rotation period. The authors explicitly state they assume this. The concern is not that the assumption is obviously false; it is that no independent evidence is presented to distinguish rotation from pulsation or other coherent signals, and the authors note two different periods in the same TESS data. If the assumption is wrong, the claimed misaligned true orbit for TOI-2046 disappears, and the paper's conclusion about a misaligned planet in an otherwise aligned sample weakens. The paper is also somewhat overreaching in the abstract's 'ruling out violent events' statement, which the authors themselves qualify in Section 4.3 for WASP-173 Ab, and the Doppler-shadow confirmation of HAT-P-41 uses a prior derived from the authors' own R-M result. These are secondary concerns. On the primary issue, I agree with the reader's identification of the TOI-2046 rotation-period assumption as the weakest link. This does not invalidate the projected lambda measurements, and the paper's central measurements are likely useful; the conditional verdict is appropriate. No change to the reader's verdict is needed.","tokens_in":26987,"tokens_out":17409,"duration_ms":158037,"concrete_test":"Compute the gyrochronological age of TOI-2046 from the 4.05 d period using the Bouma et al. (2023) relation for Teff = 6160 K, and compare it with the lithium-depletion lower limit of 700 Myr. Also estimate the tidal spin-up timescale of the star by the 1.13 MJup planet at a = 0.0248 AU to see whether a 4.05 d period can be maintained at ages >700 Myr. If the gyro age is <700 Myr and tidal spin-up is negligible, the rotation-period interpretation and the derived psi = 42 deg are internally inconsistent; conversely, if tidal spin-up can explain the fast period, the interpretation survives. A complementary check is to run the TESS light-curve analysis sector by sector to verify that a stable 4.05 d phase-coherent signal is present in all seven sectors and that it is not reproduced by a nearby blended source using TESS FFI centroids.","verdict_should_be":"UNCHANGED","load_bearing_attack":"In Section 4.1, the authors detect two photometric periods for TOI-2046 (4.05 d in long-cadence TESS and 4.29 d in short-cadence), adopt 4.05 d 'due to higher SNR', and state the periodicity is 'assumed to be due to differential rotation.' From this period they derive veq = 15.1 km/s, and combined with the R-M v sin i = 8.9 km/s obtain i* = 36 deg and psi = 42 deg. The 4.29 d period implies veq = 14.3 km/s and would still give psi ~40 deg, so the qualitative conclusion is stable against the 4.05/4.29 difference. However, the whole construction fails if the 4.05 d signal is not stellar rotation at all: a coherent pulsation (e.g., a low-frequency gamma-Dor-type mode, given the F8 spectral type) or a blended variable could produce the same periodicity. The two differing periods already suggest the interpretation is not straightforward, and no independent confirmation of rotation (e.g., periodicity in activity indicators, a coherent spot crossing model, or a stable phase across sectors) is provided. There is also an internal tension: for a star claimed to be at least 700 Myr old, a 4.05 d rotation period is unusually fast; the gyrochronological age derived by the authors themselves (0.46 Gyr) sits below their lithium-based lower limit. If the periodicity is not rotation, the derived i* and hence the headline true obliquity for TOI-2046 are unconstrained.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper analyzes archival HARPS/HARPS-N transit time series of eight close-in gas giants and models the Rossiter-McLaughlin effect to derive sky-projected stellar obliquities. It reports first-time λ measurements for seven systems and an updated value for HAT-P-41 Ab, finding HAT-P-50b to be prograde but misaligned (λ=41+10/−9 deg) and all others consistent with aligned orbits. For four systems (WASP-140 Ab, WASP-173 Ab, TOI-2046b, Qatar-4b) the paper derives true obliquities from photometric rotation periods, with TOI-2046b showing a misaligned ψ=42+10/−8 deg. The paper also presents revised age estimates for TOI-2046 (≥700 Myr) and Qatar-4 (350–500 Myr), and reports orbit-orbit angles for multi-star systems.","tokens_in":27384,"tokens_out":6243,"duration_ms":58355,"significance":"The main projected-obliquity measurements are valuable: they add seven new systems to the TEPCat sample, use standard R-M fitting with literature priors and MCMC diagnostics, and identify HAT-P-50b as a genuinely misaligned hot Jupiter in a binary, which is a useful constraint for migration scenarios. The paper also provides rotation periods and true-obliquity estimates for four systems, extending the three-dimensional obliquity census. The age estimates for TOI-2046 and Qatar-4, if supported, would correct earlier claims that these systems are very young. The strengths of the paper include full MCMC corner plots and residual figures for every target, explicit prior choices, and the use of archival data, which makes the main λ results transparent and reproducible.","major_comments":[{"comment":"The true obliquity of TOI-2046b (ψ=42+10/−8 deg) is entirely conditional on the assumption that the 4.05 d TESS periodicity is the stellar rotation period. The authors state this assumption explicitly ('This periodicity, that we assume to be due to differential rotation'), and the short-cadence data give a different period of 4.29 d. No independent confirmation of a rotational origin (e.g., phase stability across sectors, activity-index modulation, or spot modeling) is provided. If the 4.05 d signal is not rotation but a pulsation or a blended variable, then the derived v_eq, the stellar inclination i*, and hence the headline ψ are unconstrained. The paper should either add such confirmation or present ψ as conditional on the rotation interpretation, and it should propagate the 4.05/4.29 ambiguity into the quoted uncertainty.","section":"Section 4.1"},{"comment":"The abstract's statement that the aligned orbits 'rule out violent events that would excite the orbits over the history of these systems' is too strong and is internally contradicted. Section 4.3 explicitly states for WASP-173 Ab that 'the high-eccentricity migration scenario cannot be ruled out from the stellar obliquity measurements alone' because the system is likely older than its tidal alignment timescale. Furthermore, TOI-2046b has a misaligned true orbit (ψ=42 deg), so it cannot be counted among the aligned orbits that rule out violent histories. The conclusion should be qualified to say that the projected obliquities are consistent with disk migration for most targets, while noting that tidal realignment or the TOI-2046 true-obliquity result limits any general claim.","section":"Abstract and Section 4.3"},{"comment":"The Doppler-shadow cross-check for HAT-P-41 Ab is not an independent confirmation because the adopted Gaussian prior on λ is centered at −13.1 deg, the mean of the Johnson et al. (2017) value and the authors' own R-M result. The resulting posterior (λ_b=−7.6+7.7/−8.0 deg) is therefore a weighted compromise between the two, so the statement in the main text that this analysis is 'consistent with our classical R-M effect analysis' is partly circular. The authors should either run the fit with a uniform prior and report the (possibly bimodal) posterior, or explicitly label the result as prior-dependent rather than as an independent check.","section":"Appendix B"},{"comment":"The new age lower limit for TOI-2046 (≥700 Myr) is based on lithium non-detection, but the authors' own gyrochronology analysis gives an age of 0.46+0.25/−0.15 Gyr, which is below that limit. The claim in Section C that 'the broad agreement among the various indicators is that these systems are older than previously reported' is not supported for TOI-2046, since the gyro and lithium methods disagree. The paper should discuss this discrepancy explicitly (e.g., possible F-star gyrochronology systematics) or soften the age claim to a lithium-based lower limit that is presented as method-dependent.","section":"Appendix C"}],"minor_comments":[{"comment":"The entry for HAT-P-50's T0 − 2450000 lists 56285.99093±0.00034, which is clearly a typo (it should be near 7737, as in Table 3). This should be corrected.","section":"Table 2"},{"comment":"In the summary, 'WASP-40b' is a typo for WASP-48b, and the phrase 'for and ψ =32+14/−13 deg' contains a duplicated 'for'.","section":"Section 5"},{"comment":"The caption contains LaTeX/Unicode artifacts ('uni00A0') that should be cleaned up.","section":"Figure A.1"},{"comment":"Blanco-Cuaresma et al. (2014a) and (2014b) appear to be the same reference with identical author lists and journals; the distinction should be clarified or merged.","section":"References"},{"comment":"The symbol 'τCe' should be 'τCE' for consistency with the text and equations.","section":"Section 4.3"}],"recommendation":"major_revision","confidential_remarks":"The paper's main λ results appear solid and publishable after revision. The most important fix is the TOI-2046 true-obliquity claim: as written, it rests on an unverified rotation-period interpretation, and the abstract overstates the dynamical conclusions relative to Section 4.3. The Appendix B circularity is also a concern but is not central to the main R-M measurements. The age claims have an internal inconsistency that should be acknowledged. The typo in Table 2 is embarrassing but easily corrected."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"This one is worth a serious referee. The paper delivers what it says: first R-M projected obliquities for seven hot Jupiters, a new value for HAT-P-41, true obliquities for four, revised ages for two young-planet candidates, and orbit-orbit angles for five binaries. The lambda measurements are standard Boue-model fits to archival HARPS/HARPS-N RVs, with literature priors, MCMC convergence checks, and residual plots; they look trustworthy. The age revisions (TOI-2046 at least 700 Myr, Qatar-4 at least 350-500 Myr) rest on a real lithium non-detection plus activity and gyro estimates, and the authors are appropriately careful about method caveats.\n\nThe soft spots are real but mostly addressable. First, the abstract says the aligned orbits are 'ruling out violent events,' yet Section 4.3 concedes that for WASP-173 the tidal alignment timescale is shorter than the system age, so high-eccentricity migration cannot be ruled out for that planet. The abstract overstates a sample-level conclusion. Second, the Doppler-shadow cross-check for HAT-P-41 uses a Gaussian prior centered on the mean of the authors' own lambda and the literature value; that is circular. It is a sanity check rather than an independent measurement, and should be labeled as such. Third, the paper itself flags the assumption, but the TOI-2046 true obliquity (psi = 42 deg) depends on adopting the 4.05 d TESS period as rotation while the short-cadence data give 4.29 d, and there is no independent confirmation (activity indicators, spot crossing, stable phase) that the signal is rotation. The period ambiguity alone would not change the qualitative conclusion, but a non-rotational origin would leave psi unconstrained. Projected lambda for TOI-2046 (1 +/- 6 deg) is untouched. Note also that the authors' own gyrochronology age (0.46 Gyr) sits below their lithium lower limit (700 Myr) for the same star; that tension is mentioned but not resolved.\n\nNone of this sinks the core measurements. The new lambda values increase the sample of hot-Jupiter spin-orbit angles, and the binary-orbit analysis adds useful context. I would want the abstract rewritten, the Doppler-shadow prior disclosed as non-independent, and the TOI-2046 rotation period defended or down-weighted before acceptance. This belongs in A&A after revision, and it deserves a referee who knows R-M systematics.","headline":"Useful new obliquity measurements from archival spectra; the core lambda values are sound, but the headline true obliquity for TOI-2046 rests on an unvalidated rotation period and the abstract overclaims.","tokens_in":27970,"tokens_out":2846,"would_cite":true,"duration_ms":26183,"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":"Seven close-in gas giants get first spin-orbit measurements; one is clearly tilted.","keywords":["Rossiter-McLaughlin effect","stellar obliquity","hot Jupiters","spin-orbit alignment","exoplanet migration","HARPS/HARPS-N spectroscopy","stellar rotation period","multi-star systems"],"falsifier":"Compare the 4.05-day and 4.29-day periodicities in TOI-2046 with independent rotation indicators, such as spot-modulated line-profile variations or a longer TESS baseline; if the true rotation period is 4.29 days instead of 4.05 days, recomputing $\\sin i_*$ changes the inferred $\\psi = 42^\\circ$, and the misalignment claim would fail.","tokens_in":26819,"feed_emoji":"🪐","tokens_out":5970,"duration_ms":49250,"temperature":0.7,"pith_summary":"Using archival HARPS and HARPS-N spectra, the paper measures the Rossiter-McLaughlin effect for eight close-in gas giants and reports first-time projected stellar obliquities for seven of them. The central result is that HAT-P-50b is prograde but misaligned, with $\\lambda = 41^\\circ\\,^{+10}_{-9}$, while the other seven planets are consistent with alignment, $|\\lambda| \\le 13^\\circ$. For four systems the paper also derives the true three-dimensional obliquity, finding that TOI-2046b is genuinely misaligned at $\\psi = 42^\\circ\\,^{+10}_{-8}$ even though its projected value looks aligned. The paper further argues that TOI-2046 and Qatar-4 are much older than previously claimed, at least 700 Myr and 350$-$500 Myr respectively. These measurements matter because spin-orbit alignment is a diagnostic of whether hot Jupiters migrated gently through a disk or were scattered into eccentric orbits by companions.","feed_headline":"First obliquities for seven hot Jupiters reveal one tilted orbit","feed_subtitle":"HAT-P-50b sits 41 degrees off its star's spin; the other seven align, favoring gentle disk migration.","key_machinery":"The central object is the Rossiter-McLaughlin anomaly, the transient spectral-line distortion that shifts apparent radial velocities during transit. The paper fits it with ARoMEpy, a Python implementation of the Boué et al. model, jointly with a Keplerian orbit via MCMC, using literature priors on transit parameters and fixed limb-darkening coefficients. For true obliquity, the paper uses the spherical law of cosines $\\cos\\psi = \\sin i_* \\sin i \\cos|\\lambda| + \\cos i_* \\cos i$, following the Masuda & Winn approach to handle the dependency between $v$ and $v\\sin i_*$. Rotation periods come from Lomb-Scargle periodograms of ASAS-SN and TESS light curves. Age estimates use lithium non-detection, gyrochronology, and $R'_{HK}$ activity indices.","core_discovery":"The paper analyzes archival HARPS and HARPS-N transit time series of eight gas giants on short orbits and fits the Rossiter-McLaughlin anomaly with a Keplerian plus R-M model. It reports first-time projected obliquities for WASP-48b, WASP-59b, WASP-140 Ab, WASP-173 Ab, TOI-2046b, HAT-P-50b and Qatar-4b, together with an updated value for HAT-P-41 Ab. The headline result is that HAT-P-50b is prograde but misaligned ($\\lambda = 41^\\circ\\,^{+10}_{-9}$), while the other seven are consistent with alignment ($|\\lambda| \\le 13^\\circ$). For four systems with measured stellar rotation periods, the paper derives true obliquities via the spherical law of cosines, finding $\\psi = 42^\\circ\\,^{+10}_{-8}$ for TOI-2046b, $\\psi = 30^\\circ\\,^{+18}_{-15}$ for WASP-140 Ab, $\\psi = 21^\\circ\\,^{+9}_{-10}$ for WASP-173 Ab, and $\\psi = 32^\\circ\\,^{+14}_{-13}$ for Qatar-4b. It also revises the ages of TOI-2046 and Qatar-4 upward, concluding that both systems are substantially older than previous estimates.","pith_inferences":["If HAT-P-41 Ab's orbit is indeed aligned as newly measured, the planet's high atmospheric metallicity becomes consistent with disk migration, resolving a tension; a subsequent solar-metallicity measurement would reopen the question.","The hidden misalignment of TOI-2046b demonstrates that projected obliquities alone can miss true misalignments, so expanding true-obliquity samples with reliable rotation periods would clarify how common such projection-hiding geometries are.","The two systems with line-of-sight orbit-orbit misalignment (WASP-140 and HAT-P-41) could be re-tested with forthcoming Gaia astrometry, which would either confirm or dissolve the current $\\gamma$ values.","Doppler tomography of HAT-P-50b would provide an independent check of the 41-degree misalignment without relying on the assumptions of the Boué-model R-M fit."],"forward_implications":["HAT-P-50b's 41-degree misalignment, together with its 327 au stellar companion and a Kozai-Lidov timescale of roughly 0.1$-$1 Gyr, makes high-eccentricity migration a plausible formation route.","The other seven systems are aligned to within 13 degrees, with tidal alignment timescales longer than their ages, so their current spin-orbit angles likely reflect their initial configurations and are consistent with slow disk migration.","TOI-2046b is misaligned in three dimensions ($\\psi = 42^\\circ$) even though its projected obliquity is near zero, showing that projection can hide real misalignment.","TOI-2046 and Qatar-4 are not the young ($<200$ Myr) systems previously claimed; lithium non-detection and gyrochronology place them at $\\ge 700$ Myr and $\\ge 350$-$500$ Myr, respectively.","The updated alignment of HAT-P-41 Ab reconciles its high atmospheric metallicity with disk migration and removes the tension that led to its withdrawal from a homogeneous JWST atmospheric sample."],"supporting_citations":[{"why":"Supplies the Rossiter-McLaughlin anomaly model that ARoMEpy implements for the RV fits.","marker":"Boué et al. 2013"},{"why":"Provides the ARoMEpy package used to fit the Keplerian plus R-M composite model.","marker":"Sedaghati et al. 2023"},{"why":"Establishes the fitting methodology that this paper follows.","marker":"Zak et al. 2024a"},{"why":"Gives the previous HAT-P-41 Ab obliquity measurement that this paper updates.","marker":"Johnson et al. 2017"},{"why":"Provides the approach for converting projected obliquity to true obliquity using v and v sin i*.","marker":"Masuda & Winn 2020"},{"why":"Supplies the tidal alignment timescale formulas used to interpret the measured obliquities.","marker":"Albrecht et al. 2012"},{"why":"Invoked for the Kozai-Lidov mechanism proposed for HAT-P-50b's misalignment.","marker":"Fabrycky & Tremaine 2007"},{"why":"Provides the close binary companion parameters for HAT-P-50 used to estimate the Kozai-Lidov timescale.","marker":"Lester et al. 2021"},{"why":"Provides lithium depletion models used to set lower age limits for TOI-2046 and Qatar-4.","marker":"Jeffries et al. 2023"},{"why":"Supplies the gyrochronology interpolation tool used for the new stellar age estimates.","marker":"Bouma et al. 2023"}],"fun_headline_variants":["One hot Jupiter tilts 41 degrees, seven align—gentle migration wins","HAT-P-50b tilts 41°; seven other hot Jupiters stay aligned","Obliquities for 8 hot Jupiters: one misaligned, seven on track","Tilted HAT-P-50b vs seven aligned: gentle migration supported","8 hot Jupiters: 7 aligned, 1 tilted 41°—gentle migration favored"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The claim that TOI-2046b is genuinely misaligned ($\\psi = 42^\\circ$) rests on interpreting a 4.05-day TESS periodicity as the stellar rotation period of TOI-2046, even though short-cadence data give 4.29 days; if that period is wrong, the stellar inclination and hence the true obliquity are not determined.","fun_headline_variants_meta":{"raw":{"variants":["One hot Jupiter tilts 41 degrees, seven align—gentle migration wins","HAT-P-50b tilts 41°; seven other hot Jupiters stay aligned","Obliquities for 8 hot Jupiters: one misaligned, seven on track","Tilted HAT-P-50b vs seven aligned: gentle migration supported","8 hot Jupiters: 7 aligned, 1 tilted 41°—gentle migration favored"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000927,"raw_usage":{"total_tokens":4166,"prompt_tokens":1333,"completion_tokens":2833,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":949,"completion_tokens_details":{"reasoning_tokens":2714}},"tokens_in":949,"tokens_out":2833,"duration_ms":18484,"temperature":1.0,"reasoning_tokens":2714,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-10T21:13:22.656441+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Compare the 4.05-day and 4.29-day periodicities in TOI-2046 with independent rotation indicators, such as spot-modulated line-profile variations or a longer TESS baseline; if the true rotation period is 4.29 days instead of 4.05 days, recomputing $\\sin i_*$ changes the inferred $\\psi = 42^\\circ$, and the misalignment claim would fail.","supporting_citations":[{"cited_title":"2023, , 166, 130","cited_arxiv_id":null,"evidence_quote":"Provides the ARoMEpy package used to fit the Keplerian plus R-M composite model."},{"cited_title":"C., Cochran , W","cited_arxiv_id":null,"evidence_quote":"Gives the previous HAT-P-41 Ab obliquity measurement that this paper updates."},{"cited_title":"V., Matson , R","cited_arxiv_id":null,"evidence_quote":"Provides the close binary companion parameters for HAT-P-50 used to estimate the Kozai-Lidov timescale."},{"cited_title":"D., Jackson , R","cited_arxiv_id":null,"evidence_quote":"Provides lithium depletion models used to set lower age limits for TOI-2046 and Qatar-4."}],"review_version":1}