The Astrophysical Journal Letters最新文献

{"title":"Phosphine Depletion in Brown Dwarf Atmospheres Explained due to Metal Phosphide Formation","authors":"Rongzhang Yin, Yan Li, Yanzhang Li and Sara Seager","doi":"10.3847/2041-8213/ae606a","DOIUrl":"https://doi.org/10.3847/2041-8213/ae606a","url":null,"abstract":"Phosphine (PH3) is predicted to be the dominant phosphorus-bearing gas in cool substellar atmospheres, yet observations have revealed a puzzling pattern. While Jupiter and Saturn exhibit measurable PH3 abundances sustained by vertical mixing, most brown dwarfs show severe phosphine depletion. The recent detection of PH3 in two metal-poor brown dwarfs, contrasted with its absence in higher-metallicity counterparts, suggests a metallicity-controlled sequestration mechanism. The origin of this discrepancy has remained unresolved. Here, we show that PH3 is efficiently sequestered in metal-rich brown dwarf atmospheres through the formation of condensed metal phosphides. Through density functional theory calculations and atmospheric chemical equilibrium modeling, we demonstrate that phosphide-forming reactions under brown dwarf temperature–pressure conditions preferentially partition phosphorus into solid phases over gaseous PH3. This mechanism can explain the depletion of PH3 in higher-metallicity brown dwarfs, while its persistence in metal-poor cases reflects the reduced availability of condensing metals. In contrast, in giant planets like Jupiter and Saturn, Fe, Mg, and Ni condense deep below the photosphere into a (dilute) core, largely preventing phosphide formation from depleting atmospheric PH3. Our findings reveal that phosphine abundance is strongly coupled to metallicity and atmospheric condensation chemistry, providing a unified framework to interpret its distribution across substellar atmospheres. Finally, future work is needed to assess the impact of nonequilibrium effects such as kinetics.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147755103","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}

{"title":"A Close Quasar Pair in a Massive Galaxy Merger at z = 5.7","authors":"Minghao Yue, Xiaohui Fan, Anna-Christina Eilers, Feige Wang, Jinyi Yang and Robert A. Simcoe","doi":"10.3847/2041-8213/ae5e5b","DOIUrl":"https://doi.org/10.3847/2041-8213/ae5e5b","url":null,"abstract":"Close quasar pairs are rare products of galaxy mergers in which both supermassive black holes (SMBHs) are actively accreting, offering strong constraints on merger-driven active galactic nuclei evolution. Identifying close quasar pairs at z ≳ 4 is challenging due to the declining quasar number density in the early Universe. Here we report the confirmation of a close quasar pair at z = 5.7, J2037–4537, utilizing high-resolution Atacama Large Millimeter/submillimeter Array observations. The quasar host galaxies exhibit tidal disturbed features in both the far-infrared continuum emission and the [C ii] line emission, ruling out the doubly imaged lensed quasar scenario. The two quasar hosts are massive (Mdyn ≳ 1010M⊙) and star-forming (star formation rate ≳ 500M⊙ yr−1). The confirmation of J2037–4537 puts a lower limit on the quasar pair fraction at 5.5 < z < 6, Fpair > 1.2%, which is much higher than the quasar pair fraction at z ≲ 4. J2037–4537 is expected to form a gravitationally bound SMBH binary within ≲2 Gyr. The elevated quasar pair fraction at z > 5.5, as indicated by J2037–4537, likely contributes to the high gravitational-wave background reported by recent pulsar timing array experiments.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147755067","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}

{"title":"Kilonovae and Long-duration Gamma-Ray Bursts","authors":"Marko Ristić, Brandon L. Barker, Samuel Cupp, Axel Gross, Nicole Lloyd-Ronning, Oleg Korobkin, Jonah M. Miller and Matthew R. Mumpower","doi":"10.3847/2041-8213/ae5e53","DOIUrl":"https://doi.org/10.3847/2041-8213/ae5e53","url":null,"abstract":"Recent detections of kilonova-like emission following long-duration gamma-ray bursts GRB 211211A and GRB 230307A have been interpreted as originating from the merger of two neutron stars. In this work, we demonstrate that these observations are also consistent with nucleosynthesis originating from a collapsar scenario. Our model is capable of reproducing the observed optical and infrared light curves using a single, weak r-process component. The absence of lanthanide-rich material in our model, consistent with the data, challenges the prevailing interpretation that a red evolution in such transients necessarily indicates the presence of heavy r-process elements.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"27 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147751716","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}

{"title":"Beyond Large-scale Descriptions of Coronal Mass Ejections: Quantifying Their Substructures in Three Dimensions","authors":"Carlos R. Braga, Manolis K. Georgoulis, Vicki Toy-Edens, Angelos Vourlidas, Guillermo Stenborg and Nour E. Raouafi","doi":"10.3847/2041-8213/ae57a7","DOIUrl":"https://doi.org/10.3847/2041-8213/ae57a7","url":null,"abstract":"Coronal mass ejections (CMEs) are usually characterized by their large-scale properties, even though smaller-scale structures are clearly evident, particularly in observations obtained closer to the Sun. Since the launch of the Parker Solar Probe (PSP) mission, its Wide-field Imager for Solar Probe (WISPR) telescope has enjoyed unprecedented proximity to CMEs in the upper corona and inner heliosphere and has imaged CME substructure in high spatial and temporal detail. Leveraging these observations, we introduce the novel Multi-pOint Single-observatory AnalysIs of Kinematics in Three Dimensions (MOSAIK3D) method to quantitatively characterize CME substructure observable by WISPR. MOSAIK3D uses apparent substructure flows to enable a detailed determination of kinematics in three dimensions. We demonstrate MOSAIK3D on a CME observed on 2024 September 26 with PSP located at approximately 40 solar radii from the Sun center. From a set of point-like features whose apparent two-dimensional speed is inferred using optical flows, we exploit PSP’s fast angular speed to recover their coordinates in three dimensions in qualitative agreement with the graduated cylindrical shell model of the full CME. We then render a contiguous, homogeneous three-dimensional volume of the CME substructure via a convex hull methodology. The recovered kinematics and dynamics offer the most detailed analysis of CME substructure to date, showcasing that the bulk CME properties obtained from global modeling are, in fact, gross simplifications of a significantly more complex and intriguing dynamical evolution at finer scales. We offer a preview of the capabilities of the MOSAIK3D analysis and its potential applications in future work.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"27 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147751760","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}

{"title":"Discovery of a z ≃ 4.9 Lyα Emitter Protocluster: Wavelength-dependent Environmental Effects on Galaxy Structure","authors":"Ronaldo Laishram, Yusei Koyama, Haruka Kusakabe, Satoshi Kikuta, Shunta Shimizu and Tadayuki Kodama","doi":"10.3847/2041-8213/ae5824","DOIUrl":"https://doi.org/10.3847/2041-8213/ae5824","url":null,"abstract":"We report the discovery of a Lyα emitter (LAE) protocluster at z = 4.90 in the COSMOS field, comprising four distinct overdensity peaks spanning ∼65 × 36 cMpc2, with the primary concentration exhibiting a fourfold surface density enhancement relative to the field within a 1.5 proper Mpc (pMpc) radius. Using SILVERRUSH narrowband survey data combined with JWST COSMOS-Web imaging, we perform one of the first systematic rest-frame optical and UV morphological comparisons of protocluster versus field LAEs at this redshift using JWST NIRCam rest-frame UV (F150W, ∼2540 Å) and optical (F277W, ∼4700 Å) imaging. Sérsic profile fitting for 16 protocluster members and 23 field LAEs reveals a size difference: protocluster LAEs are ∼40% larger in rest-optical (median kpc versus kpc, p = 0.041), with no significant difference in rest-UV (p = 0.51) or Sérsic index. At fixed stellar mass, protocluster LAEs are offset by +0.12 dex (≃31%) in rest-optical size from the field size–mass relation (68% confidence interval (CI): [+0.08, +0.21]; Mann–Whitney p = 0.033), with 75% exhibiting positive size residuals compared to 44% of field LAEs. This wavelength-dependent environmental signature suggests that protocluster environments at z ≃ 5 preferentially affect extended stellar populations, possibly through tidal interactions, with no significant environmental difference detected in rest-UV sizes, providing observational evidence for environmental influences on the structure of LAEs during the early buildup phase of cosmic star formation.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"69 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147751715","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}

{"title":"Measurement of the Full Shape of the Thermal Sunyaev–Zel’dovich Power Spectrum from the South Pole Telescope and Herschel–SPIRE Observations","authors":"S. Raghunathan, P. A. R. Ade, D. Anbajagane, A. J. Anderson, B. Ansarinejad, M. Archipley, J. E. Austermann, L. Balkenhol, D. R. Barron, P. S. Barry, J. A. Beall, K. Benabed, A. N. Bender, B. A. Benson, F. Bianchini, L. E. Bleem, J. Bock, S. Bocquet, F. R. Bouchet, L. Bryant, E. Camphuis, M. G. Campitiello, J. E. Carlstrom, J. Carron, C. L. Chang, P. Chaubal, H. C. Chiang, P. M. Chichura, A. Chokshi, T.-L. Chou, R. Citron, A. Coerver, C. Corbett Moran, T. M. Crawford, A. T. Crites, C. Daley, T. de Haan, K. R. Dibert, M. A. Dobbs, M. Doohan, A. Doussot, D. Dutcher, W. Everett, C. Feng, K. R. Ferguson, N. C. Ferree, K. Fichman, A. Foster, S. Galli, J. Gallicchio, A. E. Gambrel, A. K. Gao, R. W. Gardner, F. Ge, E. M. George, N. Goeckner-Wald, R. Gualtieri, F. Guidi, S. Guns, N. Gupta, N. W. Halverson, E. Hivon, A. Y. Q. Ho, G. P. Holder, W. L. Holzapfel, J. C. Hood, J. D. Hrubes, A. Hryciuk, N. Huang, J. Hubmayr, K. D. Irwin, T. Jhaveri, F. Kéruzoré, A. R. Khalife, L. Knox, M. K..","doi":"10.3847/2041-8213/ae5c07","DOIUrl":"https://doi.org/10.3847/2041-8213/ae5c07","url":null,"abstract":"We present a measurement of the full shape of the power spectrum of the thermal Sunyaev–Zel’dovich (tSZ) effect down to arcminute scales using cosmic microwave background (CMB) data from the South Pole Telescope (SPT) over a roughly 100 deg2 field. The analysis incorporates data from the 2019–2020 seasons of the SPT-3G survey in bands centered at 95, 150, and 220 GHz; from the full SPTpol dataset at 150 GHz; and from the Herschel–SPIRE survey in bands centered at 600 and 857 GHz. We combine data from all the above bands using linear combination (LC) techniques to produce a tSZ or Compton-y map. We modify the LC weights to produce multiple versions of the Compton-y map, including minimum-variance (MV) and foreground-minimized (-min) maps. We measure the auto- and cross-power spectra of a subset of these maps in the range ℓ ∈ [500, 5000]. While this power spectrum includes contributions from signals other than tSZ, we present numerous checks to show that the most challenging foreground signal, the cosmic infrared background (CIB), is much lower than the desired tSZ signal in the scales of interest in this work. The final tSZ power spectrum is measured at 9.3σ with both the MV and CIB-min maps. Our results are consistent with those reported in other CMB surveys across the literature. Using the difference in the tSZ power spectrum from the MV and CIB-min maps, we reconstruct the scale-dependent tSZ–CIB cross correlation , finding 3.1σ evidence for a nonzero correlation coefficient that is positive on large scales and approaches zero for ℓ > 2500. This result represents the deepest tSZ maps ever produced and provides new constraints that can help refine astrophysical feedback mechanisms and models of the intracluster medium.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147736764","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}

{"title":"A Tale of Two Jets: Double Relativistic Outflows from Close Binary Gamma-Ray Burst Progenitors","authors":"He Gao","doi":"10.3847/2041-8213/ae5d46","DOIUrl":"https://doi.org/10.3847/2041-8213/ae5d46","url":null,"abstract":"Gravitational-wave astronomy has revealed that close binaries with compact companions are widespread. Long gamma-ray bursts (LGRBs) from massive star collapse face persistent challenges in achieving the rapid core rotation required by the collapsar model. Binary interaction via tidal spin-up offers a natural solution; recent population synthesis studies suggest a substantial fraction of LGRBs may originate from close binaries with a compact companion. In this scenario, supernova ejecta from the primary can be accreted by the companion, potentially launching a second relativistic jet after a delay set by the binary separation. We develop a comprehensive model for these double-jet systems, analyzing the dynamics of the second jet and its interaction with the first. The resulting observational signatures depend critically on the Lorentz factor ratio, the alignment angle, and the time delay. For aligned jets, two regimes arise: a fast second jet producing multiple gamma-ray triggers with distinct spectral/polarization evolution, and a slow second jet where its emission appears as an X-ray flare followed by an afterglow plateau from energy injection. For misaligned jets, the observed signal ranges from normal gamma-ray bursts (GRBs) with late-time radio structures to fast X-ray transients followed by off-axis rebrightening. These features have observational parallels in existing GRB data. High-resolution radio interferometry with SKA, time-resolved polarimetry with eXTP, and multiwavelength surveys with Einstein Probe and SVOM will test these predictions, providing constraints on the evolution of close massive binaries as progenitors of GRBs and gravitational-wave sources.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"148 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147736801","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}

{"title":"A Major Geomagnetic Storm in 2024 October Linked to Sympathetic Coronal Mass Ejection–Prominence Eruptions","authors":"Rui Wang, Huidong Hu, Xiaowei Zhao, Chong Chen, Suli Ma, Zhongwei Yang, Lei Lu, Li Feng, Wenshuai Cheng, Chong Huang, Quan Wang, Xiaoshuai Zhu, Bei Zhu and Yiming Jiao","doi":"10.3847/2041-8213/ae5801","DOIUrl":"https://doi.org/10.3847/2041-8213/ae5801","url":null,"abstract":"Improving predictions of the geomagnetic impact of coronal mass ejections (CMEs) requires understanding how solar source properties relate to in situ measurements at Earth. However, major geomagnetic storms frequently arise from interacting CMEs, complicating the link back to their solar origins. We analyze a CME interaction event that caused a major geomagnetic storm in 2024 October 10–11 (Dst ∼ −333 nT). Multiviewpoint observations reveal that the storm was related to a sympathetic eruption involving a quiescent filament and an active-region CME. The coronagraph on board the Advanced Space-based Solar Observatory clearly shows that this sympathetic eruption resulted in two distinct CMEs. Due to the overlap of the CMEs in the coronagraph field of view (FOV), a spheroid shock model was used to fit the observed shock. Kinematic analysis indicates that the interacting CMEs had completed their impulsive acceleration phase before entering the coronagraph FOV, with a slow deceleration continuing beyond 100 R⊙. In situ measurements indicate that the enhanced southward magnetic fields, arising from compression during CME interactions, were the primary driver of the storm. Compared to photospheric fields, the in situ magnetic fields suggest that the trailing CME maintained flux-rope-like signatures consistent with the source region. In contrast, the compressed leading CME displayed varying magnetic configurations between Wind and STEREO-A, featuring distorted flux-rope signatures and inconsistent inferred axis orientations. Our study bridges solar source dynamics to in situ multipoint measurements, providing key insights for space weather prediction. Nevertheless, the direct linkage between source-region magnetic field configurations and these measurements remains tentative and requires further investigation.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"115 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147736763","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}

{"title":"A Kiloparsec-scale Stellar Cavity in the Center of A402-BCG May Be Caused by Dynamic Interactions with an Ultramassive Black Hole","authors":"Michael McDonald, Gourav Khullar, David Lagattuta, Guillaume Mahler, Shashank Dattathri, Jose M. Diego, Alastair C. Edge, Benjamin Floyd, Michael D. Gladders, Scott A. Hughes, Mathilde Jauzac, Nader Khonji, Gavin Leroy, Richard Massey, Mireia Montes, Priyamvada Natarajan, Michael Reefe, Keren Sharon, Frank van den Bosch, Stepane Werner and Adi Zitrin","doi":"10.3847/2041-8213/ae5bbe","DOIUrl":"https://doi.org/10.3847/2041-8213/ae5bbe","url":null,"abstract":"We present new observations from JWST that reveal a striking kiloparsec-wide cavity in the stellar distribution of the central galaxy in the cluster A402. Supporting data from the Hubble Space Telescope (HST) allow us to rule out extinction due to dust as an explanation, and instead, suggest that this is a localized depression in the stellar density field corresponding to ∼2 × 109M⊙ in missing stars within a volume of 0.5 kpc3. On larger scales, both the JWST and HST data show evidence for a 2.2 kpc flattened core in the stellar distribution (on which the smaller-scale cavity is superimposed), which implies the presence of a central ultramassive black hole with MBH ∼ 5 × 1010M⊙. We report evidence for a mid-IR-bright point source at one edge of the cavity, suggesting that this black hole is actively accreting. MUSE spectroscopy reveals that this source is a low-ionization nuclear emission-line region active galactic nucleus (AGN) and that there is a second candidate AGN on the opposite side of the cavity with a relative velocity of 370 km s−1—if real, this implies the presence of a kiloparsec-separation dual AGN with a total binary mass of 6 ± 2 × 1010M⊙, which would make this the most massive binary black hole system discovered to date. We propose that this unique stellar cavity is the result of a short-lived dynamical interaction between at least one supermassive black hole and the background stellar density field, caused either by three-body scattering during binary hardening or the induction of a dipole instability in the stellar density field.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147736487","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}

{"title":"Toward Early-type Eclipsing Binaries as Extragalactic Milestones: First Calibration of the SBCR from O- and B-type Stars in Detached Eclipsing Binaries","authors":"Mónica Taormina, G. Pietrzyński, B. Pilecki, R.-P. Kudritzki, D. Graczyk, J. Puls and M. Górski","doi":"10.3847/2041-8213/ae5b84","DOIUrl":"https://doi.org/10.3847/2041-8213/ae5b84","url":null,"abstract":"To measure precise distances beyond the Magellanic Clouds and determine an accurate value of the Hubble constant, eclipsing binary systems composed of early-type stars can play a crucial role. However, it is fundamental to first obtain a reliable empirical surface brightness–color relation (SBCR) for the hottest possible stars. Based on our previous study of six detached eclipsing binaries composed of O- and B-type stars in the Large Magellanic Cloud, we calibrated the SBCR using 12 stars with V − Ks < –0.6 mag. We found a significant difference between O-type and B-type stars in SBCRs, which are clearly separated in mass. The relation based on B-type stars is consistent with the relation for redder stars from the literature. This allowed us to provide a combined relation valid for stars less massive than ∼16 M⊙in the wide color range −0.9 < V − Ks < 2.1 mag, with σ = 0.025 mag. Such a relation can provide extragalactic distances precise to as high as ∼1.2% given the sufficient quality and number of target objects. The relation for O-type stars (σ = 0.055 mag) remains uncertain due to its strong dependence on the method used to determine reddening and requires further study. However, we tested it on the only known eclipsing system in M33 and obtained distance modulus DM = 24.90 ± 0.17 mag, which perfectly agrees with the published distance to the system.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"140 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147736485","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}