The Astrophysical Journal Letters最新文献

Anisotropic Turbulent Flows Observed in Above-the-loop-top Regions during Solar Flares

The Astrophysical Journal Letters Pub Date : 2025-04-24 DOI: 10.3847/2041-8213/adc91b

Xiaoyan Xie, Chengcai Shen, Katharine K. Reeves, Bin Chen, Xiaocan Li, Fan Guo, Sijie Yu, Yuqian Wei and Chuanfei Dong

{"title":"Anisotropic Turbulent Flows Observed in Above-the-loop-top Regions during Solar Flares","authors":"Xiaoyan Xie, Chengcai Shen, Katharine K. Reeves, Bin Chen, Xiaocan Li, Fan Guo, Sijie Yu, Yuqian Wei and Chuanfei Dong","doi":"10.3847/2041-8213/adc91b","DOIUrl":"https://doi.org/10.3847/2041-8213/adc91b","url":null,"abstract":"Solar flare above-the-loop-top (ALT) regions are vital for understanding solar eruptions and fundamental processes in plasma physics. Recent advances in three-dimensional (3D) magnetohydrodynamic (MHD) simulations have revealed unprecedented details on turbulent flows and MHD instabilities in flare ALT regions. Here, for the first time, we examine the observable anisotropic properties of turbulent flows in ALT by applying a flow-tracking algorithm on narrow-band extreme-ultraviolet images that are observed from the face-on viewing perspective. First, the results quantitatively confirm the previous observation that vertical motions dominate and that the anisotropic flows are widely distributed in the entire ALT region with the contribution from both upflows and downflows. Second, the anisotropy shows height-dependent features, with the most substantial anisotropy appearing at a certain middle height in ALT, which agrees well with the MHD modeling results where turbulent flows are caused by Rayleigh–Taylor-type instabilities in the ALT region. Finally, our finding suggests that supra-arcade downflows (SADs), the most prominently visible dynamical structures in ALT regions, are only one aspect of turbulent flows. Among these turbulent flows, we also report the antisunward-moving underdense flows that might develop due to MHD instabilities, as suggested by previous 3D flare models. Our results indicate that the entire flare fan displays group behavior of turbulent flows where the observational bright spikes and relatively dark SADs exhibit similar anisotropic characteristics.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143872737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Discovery of a Radio Megahalo in the Cluster PLCKG287.0+32.9 Using the uGMRT 利用 uGMRT 发现星团 PLCKG287.0+32.9 中的射电巨光环

The Astrophysical Journal Letters Pub Date : 2025-04-23 DOI: 10.3847/2041-8213/adc396

Sameer Salunkhe, Ramananda Santra and Ruta Kale

{"title":"Discovery of a Radio Megahalo in the Cluster PLCKG287.0+32.9 Using the uGMRT","authors":"Sameer Salunkhe, Ramananda Santra and Ruta Kale","doi":"10.3847/2041-8213/adc396","DOIUrl":"https://doi.org/10.3847/2041-8213/adc396","url":null,"abstract":"We report the discovery of a radio megahalo in the merging cluster PLCKG287.0+32.9, based on upgraded Giant Metrewave Radio telescope (uGMRT) observations at frequencies 300–850 MHz. The sensitive radio observations provide a new window to study the complex physics occurring in this system. Apart from significant detections of the known diffuse radio emission in the cluster, we detect the central diffuse emission to a much larger extent of ∼3.2 Mpc, reaching the R500 of the cluster. The radial surface brightness profile shows a distinct flattening beyond ∼0.5R500, dividing the emission into inner and outer components. This outer envelope shows a steep spectral index (≲−1.5) and emissivity ∼20 times lower than the inner component, confirming the megahalo characteristics. The radial profile of the spectral index also distinguishes the steep spectrum megahalo emission. Our observational results align with recent numerical simulations, showing megahalo emission oriented along the merger axis and the reacceleration of electrons driven by late-stage merger-induced turbulence. This is the first detection of a radio megahalo at a frequency higher than the LOFAR 144 MHz, opening the possibilities for more discoveries and spectral studies to understand their origin.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143866970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

On the Origin of Long-term Modulation in the Sun’s Magnetic Activity Cycle

The Astrophysical Journal Letters Pub Date : 2025-04-23 DOI: 10.3847/2041-8213/adc91e

Chitradeep Saha, Suprabha Mukhopadhyay, Dibyendu Nandy

{"title":"On the Origin of Long-term Modulation in the Sun’s Magnetic Activity Cycle","authors":"Chitradeep Saha, Suprabha Mukhopadhyay, Dibyendu Nandy","doi":"10.3847/2041-8213/adc91e","DOIUrl":"https://doi.org/10.3847/2041-8213/adc91e","url":null,"abstract":"One of the most striking manifestations of orderly behavior emerging out of complex interactions in any astrophysical system is the 11 yr cycle of sunspots. However, direct sunspot observations and reconstructions of long-term solar activity clearly exhibit amplitude fluctuations beyond the decadal timescale, which may be termed as supradecadal modulation. Whether this long-term modulation in the Sun’s magnetic activity results from nonlinear mechanisms or stochastic perturbations remains controversial and a matter of active debate. Utilizing multimillennial-scale kinematic dynamo simulations based on the Babcock–Leighton paradigm—in the likely (near-critical) regime of operation of the solar dynamo—we demonstrate that this supradecadal modulation in solar activity cannot be explained by nonlinear mechanisms alone; stochastic forcing is essential for the manifestation of observed long-term fluctuations in the near-critical dynamo regime. Our findings substantiate some independent observational and theoretical investigations and provide additional insights into temporal dynamics associated with a plethora of natural phenomena in astronomy and planetary systems arising from weakly nonlinear, nondeterministic processes.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143863011","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The Discovery and Characterization of Earth-crossing Asteroid 2024 YR4

The Astrophysical Journal Letters Pub Date : 2025-04-23 DOI: 10.3847/2041-8213/adc910

Bryce T. Bolin, Josef Hanuš, Larry Denneau, Roberto Bonamico, Laura-May Abron, Marco Delbo, Josef Ďurech, Robert Jedicke, Leo Y. Alcorn, Aleksandar Cikota, Swayamtrupta Panda and Henrique Reggiani

{"title":"The Discovery and Characterization of Earth-crossing Asteroid 2024 YR4","authors":"Bryce T. Bolin, Josef Hanuš, Larry Denneau, Roberto Bonamico, Laura-May Abron, Marco Delbo, Josef Ďurech, Robert Jedicke, Leo Y. Alcorn, Aleksandar Cikota, Swayamtrupta Panda and Henrique Reggiani","doi":"10.3847/2041-8213/adc910","DOIUrl":"https://doi.org/10.3847/2041-8213/adc910","url":null,"abstract":"We describe observations and physical characteristics of Earth-crossing asteroid 2024 YR4, discovered on 2024 December 27 by the Asteroid Terrestrial-impact Last Alert System. The asteroid has semimajor axis a = 2.52 au, eccentricity e = 0.66, inclination i = 3 41, and a ∼0.003 au Earth minimum orbit intersection distance. We obtained g-, r-, i-, and Z-imaging with the Gemini South/Gemini Multi-Object Spectrograph on 2025 February 7 and Y and J imaging with the Keck/Multi-Object Spectrometer for Infrared Exploration on 2025 February 12. We measured a g − i spectral slope of 13% ± 3%/100 nm and color indices g − r = 0.70 ± 0.10, r − i = 0.25 ± 0.06, i − Z = −0.27 ± 0.10, and Y − J = 0.41 ± 0.10. 2024 YR4 has a spectrum that best matches R-type and Sa-type asteroids and a diameter of ∼30–65 m using our measured absolute magnitude of 23.9 ± 0.3 mag and assuming an albedo of 0.15–0.4. The lightcurve of 2024 YR4 shows ∼0.4 mag variations with a rotation period of ∼1170 s. We use photometry of 2024 YR4 from Gemini and other sources taken between 2024 December to 2025 February to determine the asteroid’s spin vector and shape, finding that it has an oblate, ∼3:1 axial ratio and a pole direction of λ, β = ∼ 42∘, ∼−25∘. Finally, we compare the orbital elements of 2024 YR4 with the near-Earth object population model and find that its most likely sources are resonances between the inner and central Main Belt.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"53 4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143866974","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Observations of 1/f Noise at Mercury’s Solar Wind Using MESSENGER Data

The Astrophysical Journal Letters Pub Date : 2025-04-23 DOI: 10.3847/2041-8213/adc9b2

Rayta A. Pradata, Sohom Roy, William H. Matthaeus, Jiaming Wang, Rohit Chhiber, Francesco Pecora and Yan Yang

{"title":"Observations of 1/f Noise at Mercury’s Solar Wind Using MESSENGER Data","authors":"Rayta A. Pradata, Sohom Roy, William H. Matthaeus, Jiaming Wang, Rohit Chhiber, Francesco Pecora and Yan Yang","doi":"10.3847/2041-8213/adc9b2","DOIUrl":"https://doi.org/10.3847/2041-8213/adc9b2","url":null,"abstract":"Low-frequency signals having a band-limited scale-invariant power, or “1/f” noise, have been detected in the interplanetary medium and inferred from coronal and photospheric observations. Their origin remains under debate, with the principal issue being whether the signal originates from local processes or has a solar origin, possibly emerging from a superposition of scale-invariant structures. Detection of such interplanetary signals at frequencies as low as a few times 10−6 Hz at distances well within 1 au is important in developing an understanding of this phenomenon, but this is challenging due to a lack of the requisite long-duration data records. Here, we employ magnetic field data from the MESSENGER spacecraft, processed to remove Mercury’s wake, to analyze spectra from a year of data. The 1/f signal is detected down to the lowest expected frequencies, consistent with the observed lognormal distribution of correlation times and the Machlup–Montroll–Shlesinger superposition principle. This supports the hypothesis that the observed 1/f signals have an origin in solar processes, possibly the dynamo, and disfavors local in situ generation, as described in W. H. Matthaeus & M. L. Goldstein and W. H. Matthaeus et al.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143866973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Contribution of Alfvénic Waves on the Formation and Deflection of Switchbacks: Insights from Two Decades of WIND Spacecraft Data

The Astrophysical Journal Letters Pub Date : 2025-04-23 DOI: 10.3847/2041-8213/adc9a9

Hui Li, Fanzhuo Dai, Chi Wang, Wence Jiang, Haoyu Li

{"title":"Contribution of Alfvénic Waves on the Formation and Deflection of Switchbacks: Insights from Two Decades of WIND Spacecraft Data","authors":"Hui Li, Fanzhuo Dai, Chi Wang, Wence Jiang, Haoyu Li","doi":"10.3847/2041-8213/adc9a9","DOIUrl":"https://doi.org/10.3847/2041-8213/adc9a9","url":null,"abstract":"Switchbacks, characterized by large-angle deflections of the local interplanetary magnetic field relative to the background, are frequently observed throughout the heliosphere and play a crucial role in the solar wind dynamics. Recent studies have highlighted the importance of local generation mechanisms, such as expanding waves, turbulence, velocity shear, and footpoint motion, in the formation of switchbacks. Utilizing nearly two decades of data from the WIND spacecraft near 1 au, we conducted a detailed investigation into the differences between switchbacks and their surrounding environment, focusing on the influence of solar wind conditions on their occurrence rate and deflection degree. Our findings indicate that switchbacks are embedded within Alfvén waves, and their occurrence rate and maximum deflection degree are significantly enhanced during large-amplitude Alfvén waves. Specifically, the occurrence rate of switchbacks during these periods shows no significant correlation with solar wind velocity, suggesting that Alfvén wave activity is the primary driver of switchback formation. Our results further indicate that the evolution of switchbacks is closely related to the evolution of Alfvén waves, and that velocity shear and footpoint motion do not play an additional role in their evolution. These findings provide valuable insights into the dynamics of switchbacks and their relationship with solar wind conditions, contributing to a deeper understanding of the complex interactions within the heliosphere.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"69 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143863012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Identifying Thorne–Żytkow Objects through Neutrinos

The Astrophysical Journal Letters Pub Date : 2025-04-21 DOI: 10.3847/2041-8213/adc8ab

Pablo Martínez-Miravé, Irene Tamborra and Alejandro Vigna-Gómez

{"title":"Identifying Thorne–Żytkow Objects through Neutrinos","authors":"Pablo Martínez-Miravé, Irene Tamborra and Alejandro Vigna-Gómez","doi":"10.3847/2041-8213/adc8ab","DOIUrl":"https://doi.org/10.3847/2041-8213/adc8ab","url":null,"abstract":"Thorne–Żytkow objects (T Os) have been predicted to form when a neutron star is engulfed by a diffuse, convective giant envelope. Accretion onto a neutron star at a rate that is larger than 10−4M⊙ yr−1 is expected to lead to significant emission of neutrinos of all flavors with energy of 1–100 MeV. Since the neutrino signal is expected to largely vary in time (from milliseconds to thousands of years), we outline detection strategies tailored to the signal duration. We find that neutrino detection from T Os up to the Small Magellanic Cloud is within the reach of current- and next-generation neutrino observatories, such as Super- and Hyper-Kamiokande, the IceCube Neutrino Observatory, and JUNO. Interestingly, if targeted searches for neutrinos from T O candidates (e.g., VX Sgr in our Galaxy as well as HV 2112 and HV 11417 in the Small Magellanic Cloud) should lead to positive results, neutrinos could positively identify the nature of such sources and their accretion rate. Furthermore, the diffuse supernova neutrino background may be able to rule out extreme scenarios for the formation and accretion rates of TŻOs. Our findings should serve as motivation for establishing dedicated searches for neutrino emission from T Os. This is especially timely since it is challenging to detect TŻOs via electromagnetic radiation unambiguously, and the T O gravitational-wave signal could be probed with next-generation detectors for sources within our Galaxy only.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143857497","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Solar Cycle Variations in Meridional Flows and Rotational Shear within the Sun’s Near-surface Shear Layer

The Astrophysical Journal Letters Pub Date : 2025-04-21 DOI: 10.3847/2041-8213/adc919

Anisha Sen, S. P. Rajaguru, Abhinav Govindan Iyer, Ruizhu Chen, Junwei Zhao and Shukur Kholikov

{"title":"Solar Cycle Variations in Meridional Flows and Rotational Shear within the Sun’s Near-surface Shear Layer","authors":"Anisha Sen, S. P. Rajaguru, Abhinav Govindan Iyer, Ruizhu Chen, Junwei Zhao and Shukur Kholikov","doi":"10.3847/2041-8213/adc919","DOIUrl":"https://doi.org/10.3847/2041-8213/adc919","url":null,"abstract":"Using solar cycle–long helioseismic measurements of meridional and zonal flows in the near-surface shear layer (NSSL) of the Sun, we study their spatiotemporal variations and connections to active regions. We find that near-surface inflows toward active latitudes are part of a local circulation with an outflow away from them at depths around 0.97 R⊙, which is also the location where the deviations in the radial gradient of rotation change sign. These results, together with opposite signed changes, over latitude and depth, in the above quantities observed during the solar minimum period, point to the action of the Coriolis force on large-scale flows as the primary cause of changes in rotation gradient within the NSSL. We also find that such Coriolis force mediated changes in near-surface flows toward active latitudes only marginally change the amplitude of zonal flow and hence are not likely to be its driving force. Our measurements typically achieve a high signal-to-noise ratio (>5σ) for near-surface flows but can drop to 3σ near the base (0.95 R⊙) of the NSSL. Close agreements between the depth profiles of changes in rotation gradient and in meridional flows measured from quite different global and local helioseismic techniques, respectively, show that the results are not dependent on the analysis techniques.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143857499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A Disintegrating Rocky Planet with Prominent Comet-like Tails around a Bright Star

The Astrophysical Journal Letters Pub Date : 2025-04-21 DOI: 10.3847/2041-8213/adbf21

Marc Hon, Saul Rappaport, Avi Shporer, Andrew Vanderburg, Karen A. Collins, Cristilyn N. Watkins, Richard P. Schwarz, Khalid Barkaoui, Samuel W. Yee, Joshua N. Winn, Alex S. Polanski, Emily A. Gilbert, David R. Ciardi, Jeroen Audenaert, William Fong, Jack Haviland, Katharine Hesse, Daniel Muthukrishna, Glen Petitpas, Ellie Hadjiyska Schmelzer, Norio Narita, Akihiko Fukui, Sara Seager and George R. Ricker

{"title":"A Disintegrating Rocky Planet with Prominent Comet-like Tails around a Bright Star","authors":"Marc Hon, Saul Rappaport, Avi Shporer, Andrew Vanderburg, Karen A. Collins, Cristilyn N. Watkins, Richard P. Schwarz, Khalid Barkaoui, Samuel W. Yee, Joshua N. Winn, Alex S. Polanski, Emily A. Gilbert, David R. Ciardi, Jeroen Audenaert, William Fong, Jack Haviland, Katharine Hesse, Daniel Muthukrishna, Glen Petitpas, Ellie Hadjiyska Schmelzer, Norio Narita, Akihiko Fukui, Sara Seager and George R. Ricker","doi":"10.3847/2041-8213/adbf21","DOIUrl":"https://doi.org/10.3847/2041-8213/adbf21","url":null,"abstract":"We report the discovery of BD+05 4868 Ab, a transiting exoplanet orbiting a bright (V = 10.16) K-dwarf (TIC 466376085) with a period of 1.27 days. Observations from NASA’s Transiting Exoplanet Survey Satellite reveal variable transit depths and asymmetric transit profiles that are characteristic of comet-like tails formed by dusty effluents emanating from a disintegrating planet. Unique to BD+05 4868 Ab is the presence of prominent dust tails in both the trailing and leading directions that contribute to the extinction of starlight from the host star. By fitting the observed transit profile and analytically modeling the drift of dust grains within both dust tails, we infer large grain sizes (∼1–10 μm) and a mass-loss rate of 10 M⊕ Gyr−1, suggestive of a lunar-mass object with a disintegration timescale of only several Myr. The host star is probably older than the Sun and is accompanied by an M-dwarf companion at a projected physical separation of 130 au. The brightness of the host star, combined with the planet’s relatively deep transits (0.8%–2.0%), presents BD+05 4868 Ab as a prime target for compositional studies of rocky exoplanets and investigations into the nature of catastrophically evaporating planets.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143857496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

From Misaligned Sub-Saturns to Aligned Brown Dwarfs: The Highest M p /M * Systems Exhibit Low Obliquities, Even around Hot Stars*

The Astrophysical Journal Letters Pub Date : 2025-04-16 DOI: 10.3847/2041-8213/adc129

Jace Rusznak, Xian-Yu Wang, Malena Rice and Songhu Wang

{"title":"From Misaligned Sub-Saturns to Aligned Brown Dwarfs: The Highest M p /M * Systems Exhibit Low Obliquities, Even around Hot Stars*","authors":"Jace Rusznak, Xian-Yu Wang, Malena Rice and Songhu Wang","doi":"10.3847/2041-8213/adc129","DOIUrl":"https://doi.org/10.3847/2041-8213/adc129","url":null,"abstract":"We present a pattern emerging from stellar obliquity measurements in single-star systems: planets with high planet-to-star mass ratios (MP/M* ≥ 2 × 10−3)—such as super-Jupiters, brown dwarf companions, and M dwarfs hosting Jupiter-like planets—tend to be aligned, even around hot stars. This alignment represents a 3.7σ deviation from the obliquity distribution observed in systems with lower mass ratios (MP/M* < 2 × 10−3), which predominantly include Jupiters and sub-Saturns. The only known outlier system, XO-3, exhibits misalignment confirmed via our newly collected Rossiter–McLaughlin effect measurement (λ = ). However, the relatively large Gaia renormalized unit weight error of XO-3 suggests that it may harbor an undetected binary companion, potentially contributing to its misalignment. Given that tidal realignment mechanisms are weak for hot stars, the observed alignment in high MP/M* systems is likely primordial rather than resulting from tidal interactions. One possible explanation is that only dynamically isolated planets can continue accreting gas and evolve into super-Jupiters while maintaining their primordial alignment. Conversely, planets formed in compact configurations may be unable to grow beyond the gap-opening mass, for which our work suggests an empirical boundary MP/M* = 2 × 10−3 identified between aligned high MP/M* systems and misaligned low MP/M* systems, with dynamical instabilities contributing to the diverse spin–orbit misalignments observed in the latter.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"37 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143847056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0