The Astrophysical Journal Letters最新文献_第5页

Evidence of Gaia Enceladus Experiencing at Least Two Passages around the Milky Way * 土卫二盖亚经历了至少两次环绕银河系的证据*

The Astrophysical Journal Letters Pub Date : 2025-06-15 DOI: 10.3847/2041-8213/addc66

Ása Skúladóttir, Heitor Ernandes, Diane K. Feuillet, Alice Mori, Sofia Feltzing, Romain E. R. Lucchesi and Paola Di Matteo

{"title":"Evidence of Gaia Enceladus Experiencing at Least Two Passages around the Milky Way *","authors":"Ása Skúladóttir, Heitor Ernandes, Diane K. Feuillet, Alice Mori, Sofia Feltzing, Romain E. R. Lucchesi and Paola Di Matteo","doi":"10.3847/2041-8213/addc66","DOIUrl":"https://doi.org/10.3847/2041-8213/addc66","url":null,"abstract":"One of the major recent breakthroughs has been the discovery of the last major merger to happen in the history of the Milky Way. Around 10 Gyr ago, the galaxy Gaia Enceladus with an estimated ∼10% of the Milky Way mass, fell into the potential of our Galaxy, bringing a large amount of stars that can be identified through their unique chemical and kinematic signatures. Simulations have long predicted that a galaxy of this size should experience several passages through the disk of the Milky Way before eventually being fully dispersed. For the first time, we present observational evidence to support this. We identify two subpopulations accreted from Gaia Enceladus: (1) stars that today have large kinematic energy, which originated from the outskirts of Gaia Enceladus and were accreted during early passages; (2) stars with low kinetic energy accreted at later passages, originating from the inner parts of Gaia Enceladus. Through the use of high-precision chemical abundances, crucially including new aluminum measurements, we show that in all observed abundance ratios ([Fe/H], [Al/Fe], [Mg/Fe], and [Mg/Ba]), stars with high energy show evidence of coming from a less chemically evolved outer region of Gaia Enceladus, compared to the stars with low energy. We therefore conclude that Gaia Enceladus experienced several passages before merging with the main body of our Galaxy. This discovery has wide implications for our understanding of this event and consolidates Gaia Enceladus as a benchmark for studying galaxy mergers and hierarchical galaxy formation in extraordinary detail.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"90 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144296034","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

HDO Ice Detected toward an Isolated Low-mass Protostar with JWST 用JWST探测到一个孤立的低质量原恒星的HDO冰

The Astrophysical Journal Letters Pub Date : 2025-06-15 DOI: 10.3847/2041-8213/addb45

Katerina Slavicinska, Łukasz Tychoniec, María Gabriela Navarro, Ewine F. van Dishoeck, John J. Tobin, Martijn L. van Gelder, Yuan Chen, A. C. Adwin Boogert, W. Blake Drechsler, Henrik Beuther, Alessio Caratti o Garatti, S. Thomas Megeath, Pamela Klaassen, Leslie W. Looney, Patrick J. Kavanagh, Nashanty G. C. Brunken, Patrick Sheehan and William J. Fischer

{"title":"HDO Ice Detected toward an Isolated Low-mass Protostar with JWST","authors":"Katerina Slavicinska, Łukasz Tychoniec, María Gabriela Navarro, Ewine F. van Dishoeck, John J. Tobin, Martijn L. van Gelder, Yuan Chen, A. C. Adwin Boogert, W. Blake Drechsler, Henrik Beuther, Alessio Caratti o Garatti, S. Thomas Megeath, Pamela Klaassen, Leslie W. Looney, Patrick J. Kavanagh, Nashanty G. C. Brunken, Patrick Sheehan and William J. Fischer","doi":"10.3847/2041-8213/addb45","DOIUrl":"https://doi.org/10.3847/2041-8213/addb45","url":null,"abstract":"Water is detected in environments representing every stage of star and solar system formation, but its chemical evolution throughout these stages remains poorly constrained. Deuterium ratios offer a means of probing chemical links between water in different cosmic regions because of their sensitivity to physicochemical conditions. Here, we present the first detection of the 4.1 μm HDO ice feature with JWST toward a low-mass protostar, L1527 IRS, which may eventually grow to a Sun-like mass. We measure an ice HDO/H2O ratio of 4.4 × 10−3, where the reported error is dominated by uncertainties in continuum definition and ice band strengths. This fraction is similar to the gas HDO/H2O ratios measured in the warm (>100 K) inner cores of other low-mass protostellar envelopes and protoplanetary disks found in comparably isolated star-forming regions. Such a similarity tentatively supports the assumption that water vapor detected in these regions is not significantly altered by gas-phase reactions following ice sublimation. It also supports the hypothesis that pre- and protostellar water ice is largely inherited in a chemically unaltered state by outer protoplanetary disks. However, the fraction is a factor of ∼4–10 times higher than the gas HDO/H2O ratios measured toward comets and low-mass protostars in clustered star-forming regions. This difference may be due to either gas-phase water reprocessing in protostellar envelopes and protoplanetary disks or differences between prestellar conditions of isolated dense cores and the clustered star-forming regions that are more analogous to the environment in which our Sun formed.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144296035","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

Helioseismic Signature of Parker Fragmentation of Magnetic Flux beneath Sunspot Photospheres 太阳黑子光球下帕克磁通量碎片的日震特征

The Astrophysical Journal Letters Pub Date : 2025-06-15 DOI: 10.3847/2041-8213/adc912

Elena G. Broock, Angel Mart Cifuentes, Alina-Catalina Donea and Charles Lindsey

{"title":"Helioseismic Signature of Parker Fragmentation of Magnetic Flux beneath Sunspot Photospheres","authors":"Elena G. Broock, Angel Mart Cifuentes, Alina-Catalina Donea and Charles Lindsey","doi":"10.3847/2041-8213/adc912","DOIUrl":"https://doi.org/10.3847/2041-8213/adc912","url":null,"abstract":"Standard local helioseismic diagnostics of large sunspots show the signature of anomalously strong compact scatterers of p-modes within about 1 Mm beneath their photospheres. We applied standard “subjacent-vantage phase-correlation helioseismic holography” to the major sunspot umbra and inner penumbra in NOAA AR12192 as it crossed central solar meridian on 2014 October 23. This diagnostic delivers diffraction-limited maps of the phase delay in the echos of p-mode noise in the 2.5–4.5 mHz acoustic spectrum impinging upward from the underlying solar interior into the sunspot photosphere. What we recognize as the nominal sunspot umbra sends its echos back into the solar interior up to about 1.2 minutes ahead of those reflected from the quiet Sun. In addition to this, we find multiple compact regions approximately 5 Mm in horizontal diameter whose echos are expedited by a further 30 s ahead of the nominal umbral echos. These “strong acoustic scatterers” appear in both umbrae and inner penumbrae, but in a sunspot whose umbra is large enough to accommodate several of them, they show a decided affinity for the boundary separating the two. Standard focus–defocus depth diagnostics pin the anomalies to within about 1 Mm of the base of the photosphere. We propose that the strong acoustic scatterers are the helioseismic signature of fragmentation of magnetic flux beneath sunspot photospheres predicted by E. N. Parker 4.5 decades ago as a crucial accommodation for the stability of sunspot magnetic flux subject to warpage by a precipitous ambient vertical pressure gradient.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144304544","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 First Detection of Molecular Activity in the Largest Known Oort Cloud Comet: ALMA Imaging of C/2014 UN271 (Bernardinelli–Bernstein) at 16.6 au from the Sun 首次探测到已知最大的奥尔特云彗星的分子活动：距离太阳16.6 au的C/2014 UN271 （Bernardinelli-Bernstein）的ALMA成像

The Astrophysical Journal Letters Pub Date : 2025-06-11 DOI: 10.3847/2041-8213/add526

Nathan X. Roth, Stefanie N. Milam, Martin A. Cordiner, Dominique Bockelée-Morvan, Nicolas Biver, Michael S. P. Kelley, Anthony J. Remijan, Steven B. Charnley, Carrie E. Holt, Kiernan D. Foster, Joseph Chatelain, Edward Gomez, Sarah Greenstreet, Tim Lister and Helen Usher

{"title":"The First Detection of Molecular Activity in the Largest Known Oort Cloud Comet: ALMA Imaging of C/2014 UN271 (Bernardinelli–Bernstein) at 16.6 au from the Sun","authors":"Nathan X. Roth, Stefanie N. Milam, Martin A. Cordiner, Dominique Bockelée-Morvan, Nicolas Biver, Michael S. P. Kelley, Anthony J. Remijan, Steven B. Charnley, Carrie E. Holt, Kiernan D. Foster, Joseph Chatelain, Edward Gomez, Sarah Greenstreet, Tim Lister and Helen Usher","doi":"10.3847/2041-8213/add526","DOIUrl":"https://doi.org/10.3847/2041-8213/add526","url":null,"abstract":"We report observations of comet C/2014 UN271 (Bernardinelli–Bernstein) carried out on UT 2024 March 8 and 17 at a heliocentric distance (rH) of 16.6 au using the Atacama Large Millimeter/submillimeter Array (ALMA). The CO (J = 2–1) line at 230 GHz was detected along with continuum emission from its dust coma and large (∼140 km) nucleus, revealing the nature of the activity drivers and outgassing kinematics of the largest Oort cloud comet discovered to date. This work presents spectrally integrated flux maps, autocorrelation spectra, production rates, and parent scale lengths for CO and a stringent upper limit for the H2CO production rate. CO outgassing displayed multiple active jets that evolved from one epoch to the next. The continuum emission was compact and spatially unresolved and is consistent with thermal emission from the large nucleus and a tentative detection of a dust coma. Complementary optical observations provided activity context for the ALMA epochs, indicating that UN271 underwent an outburst in late February before returning to a quiescent brightness in mid- to late March. These results represent the first secure detection of molecular activity reported in the literature for C/2014 UN271 and highlight the dynamic nature of this distantly active small world.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144278614","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 New Spectral Class of Brown Dwarfs at the Bottom of the IMF in IC 348 IC 348中IMF底部的棕矮星新光谱类

The Astrophysical Journal Letters Pub Date : 2025-06-09 DOI: 10.3847/2041-8213/addc55

K. L. Luhman and C. Alves de Oliveira

{"title":"A New Spectral Class of Brown Dwarfs at the Bottom of the IMF in IC 348","authors":"K. L. Luhman and C. Alves de Oliveira","doi":"10.3847/2041-8213/addc55","DOIUrl":"https://doi.org/10.3847/2041-8213/addc55","url":null,"abstract":"In a previous study, we used James Webb Space Telescope (JWST) to identify three new brown dwarfs in the center of a nearby star-forming cluster, IC 348. The faintest object had an estimated mass of 3–4 MJup, making it a contender for the least massive brown dwarf confirmed with spectroscopy. Two of the new brown dwarfs also exhibited absorption features from an unidentified aliphatic hydrocarbon, which were not predicted by atmospheric models and were not previously detected in atmospheres outside of the solar system. We have used JWST to perform a deeper survey for brown dwarfs across a larger field in IC 348. We have identified 39 brown dwarf candidates in NIRCam images and have obtained spectra for 15 of them with Near-Infrared Spectrograph (NIRSpec), nine of which are classified as substellar members of the cluster. The faintest new members have mass estimates of ∼2 MJup, providing a new constraint on the minimum mass of the IMF. Two new members (∼2 and 10 MJup) exhibit large excess emission from circumstellar disks, demonstrating that they harbor the raw materials for planet formation. Finally, eight of the nine new brown dwarfs and one known member that is newly observed with NIRSpec show the aforementioned hydrocarbon features. Among the total of 11 brown dwarfs in IC 348 that have hydrocarbon detections, the features are stronger at fainter magnitudes, indicating that the hydrocarbon is a natural constituent of the atmospheres of the coolest newborn brown dwarfs. We propose a new spectral class “H” that is defined by the presence of the 3.4 μm fundamental band of the hydrocarbon.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144252257","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

Spectroscopic Observations of Supra-arcade Downflows 超拱廊下流的光谱观测

The Astrophysical Journal Letters Pub Date : 2025-06-09 DOI: 10.3847/2041-8213/adde59

Ryan J. French, Maria D. Kazachenko, Teodora Mihailescu and Katharine K. Reeves

{"title":"Spectroscopic Observations of Supra-arcade Downflows","authors":"Ryan J. French, Maria D. Kazachenko, Teodora Mihailescu and Katharine K. Reeves","doi":"10.3847/2041-8213/adde59","DOIUrl":"https://doi.org/10.3847/2041-8213/adde59","url":null,"abstract":"Despite their somewhat frequent appearance in extreme-ultraviolet (EUV) imaging of off-limb flares, the origins of supra-arcade downflows (SADs) remain a mystery. Appearing as dark, tendril-like downflows above growing flare loop arcades, SADs themselves are yet to be tied into the standard model of solar flares. The uncertainty of their origin is, in part, due to a lack of spectral observations, with the last published SAD spectral observations dating back to the Solar and Heliospheric Observatory/Solar Ultraviolet Measurements of Emitted Radiation era in 2003. In this work, we present new observations of SADs within an M-class solar flare on 2022 April 2, observed by the Hinode EUV Imaging Spectrometer (EIS) and the NASA Solar Dynamics Observatory. We measure Fe XXIV 192.02 Å Doppler downflows and nonthermal velocities in the low-intensity SAD features, exceeding values measured in the surrounding flare fan. The ratio of temperature-sensitive Fe XXIV 255.11 Å and Fe XXIII 263.41 Å lines also allows the measurement of electron temperature, revealing temperatures within the range of the surrounding flare fan. We compare EIS line-of-sight Doppler velocities with plane-of-sky velocities measured by Atmospheric Imaging Assembly, to construct the 3D velocity profile of four prominent SADs, finding evidence for their divergence above the flare loop arcade—possibly related to the presence of a high-altitude termination shock. Finally, we detect “stealth” SADs, which produce SAD-like Doppler signals, yet with no change in intensity.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144260241","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 Sulfur Plume in the Horsehead Nebula: New Detections of S2H, SH+, and CO+ 马头星云中的硫羽：S2H、SH+和CO+的新探测

The Astrophysical Journal Letters Pub Date : 2025-06-09 DOI: 10.3847/2041-8213/addbd3

A. Fuente, G. Esplugues, P. Rivière-Marichalar, D. Navarro-Almaida, R. Martín-Doménech, G. M. Muñoz-Caro, A. Sánchez-Monge, A. Taillard, H. Carrascosa, J. J. Miranzo-Pastor, A. Tasa-Chaveli, P. Fernández-Ruiz, V. V. Guzmán, J. R. Goicoechea, M. Gerin and J. Pety

{"title":"The Sulfur Plume in the Horsehead Nebula: New Detections of S2H, SH+, and CO+","authors":"A. Fuente, G. Esplugues, P. Rivière-Marichalar, D. Navarro-Almaida, R. Martín-Doménech, G. M. Muñoz-Caro, A. Sánchez-Monge, A. Taillard, H. Carrascosa, J. J. Miranzo-Pastor, A. Tasa-Chaveli, P. Fernández-Ruiz, V. V. Guzmán, J. R. Goicoechea, M. Gerin and J. Pety","doi":"10.3847/2041-8213/addbd3","DOIUrl":"https://doi.org/10.3847/2041-8213/addbd3","url":null,"abstract":"Sulfur is essential for life, but its abundance and distribution in the interstellar medium remain uncertain, with over 90% of sulfur undetected in cold molecular clouds. Sulfur allotropes (Sn) have been proposed as possible reservoirs, but the only detected interstellar molecule with a disulfide bond is S2H in the Horsehead Nebula, making the estimation of sulfur chains abundances difficult. Here we present total-power Atacama Large Millimeter/submillimeter Array images of H2S, S2H, SO2, CO+, and SH+ toward the Horsehead Nebula. These observations, with unprecedented sensitivity (rms ∼1.5 mK), provide the first detections of SH+ and CO+ in this region, together with the identification of a new S2H line. The comparison of the spectroscopic images of H2S, S2H, SO2, CO+, and SH+ shows that the S2H emission originates from a warm gas layer adjacent to the photodissociation front. The emission peak of S2H is offset from those of reactive ions such as SH+, CO+, and SO+, suggesting that gas-phase reactions involving SH+ and H2S are not the dominant formation pathway of S2H. Instead, we propose that S2H is desorbed from irradiated grain surfaces by nonthermal processes. The SH+ detection indicates that sulfur is not significantly depleted at the UV-irradiated edge of the molecular cloud, arguing against a major refractory sulfur reservoir in the interior of molecular clouds.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"50 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144260597","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

Dust Clumping in Outer Protoplanetary Disks: The Interplay among Four Instabilities 外原行星盘的尘埃团块：四种不稳定性之间的相互作用

The Astrophysical Journal Letters Pub Date : 2025-06-08 DOI: 10.3847/2041-8213/adcebb

Pinghui Huang and Xue-Ning Bai

{"title":"Dust Clumping in Outer Protoplanetary Disks: The Interplay among Four Instabilities","authors":"Pinghui Huang and Xue-Ning Bai","doi":"10.3847/2041-8213/adcebb","DOIUrl":"https://doi.org/10.3847/2041-8213/adcebb","url":null,"abstract":"Dust concentration in protoplanetary disks (PPDs) is the first step toward planetesimal formation, a crucial yet highly uncertain stage in planet formation. Although the streaming instability (SI) is widely recognized as a powerful mechanism for planetesimal formation, its properties can be sensitive to the gas dynamical environment. The outer region of PPDs is subject to the vertical shear instability (VSI), which could further induce the Rossby wave instability (RWI) to generate numerous vortices. In this work, we use the multifluid dust module in Athena++ to perform a 3D global simulation with mesh refinement to achieve an adequate domain size and resolution to resolve and accommodate all these instabilities. The VSI mainly governs the overall gas dynamics, which are dominated by the breathing mode due to dust mass loading. The dust strongly settles to the midplane layer, which is much more densely populated with small vortices compared to the dust-free case. Strong dust clumping is observed, which is likely owing to the joint action of the SI and dusty RWI, and those sufficient for planetesimal formation reside only in a small fraction of such vortices. Dust clumping becomes stronger with increasing resolution, and has not yet achieved numerical convergence in our exploration. In addition, we find evidence of the Kelvin–Helmholtz instability operating at certain parts of the dust–gas interface, which may contribute to the temporary destruction of dust clumps.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144238090","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

High-resolution Observations of a C9.3 White-light Flare and Its Impact on the Solar Photosphere C9.3白光耀斑的高分辨率观测及其对太阳光球层的影响

The Astrophysical Journal Letters Pub Date : 2025-06-08 DOI: 10.3847/2041-8213/adddb2

Zhe Xu, Xiaoli Yan, Zhentong Li, Liheng Yang, Zhike Xue, Jincheng Wang and Yian Zhou

引用次数: 0

3D Simulations Demonstrate Propagating Thermohaline Convection for Polluted White Dwarfs 三维模拟显示受污染白矮星的热盐对流传播

The Astrophysical Journal Letters Pub Date : 2025-06-05 DOI: 10.3847/2041-8213/addbd5

Imogen G. Cresswell, Adrian E. Fraser, Evan B. Bauer, Evan H. Anders and Benjamin P. Brown

{"title":"3D Simulations Demonstrate Propagating Thermohaline Convection for Polluted White Dwarfs","authors":"Imogen G. Cresswell, Adrian E. Fraser, Evan B. Bauer, Evan H. Anders and Benjamin P. Brown","doi":"10.3847/2041-8213/addbd5","DOIUrl":"https://doi.org/10.3847/2041-8213/addbd5","url":null,"abstract":"Polluted white dwarfs (WDs) with small surface convection zones deposit significant concentrations of heavy elements to the underlying radiative interior, presumably driving thermohaline convection. Current models of polluted WDs frequently fail to account for this effect, although its inclusion can increase the inferred accretion rate by orders of magnitude. It has been argued that this instability cannot be treated as a continuous mixing process and thus should not be considered in these models. In this work, we study 3D simulations of a thermohaline-unstable layer propagating into an underlying stable region, approximating the polluted WD scenario. We find that although thermohaline convection works to reduce driving gradients somewhat, the front continues to propagate and the system remains unstable. Importantly, the turbulent flux of metals broadly dominates over the diffusive flux in quantitative agreement with existing mixing prescriptions implemented in some stellar evolution models (except slightly below the boundary of the propagating front, where recent prescriptions neglect overshoot-like effects). Thus, our results broadly support polluted WD models that include thermohaline mixing in their estimates of the settling rate.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144228704","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