The Astrophysical Journal最新文献

{"title":"Self-consistent Solutions of Evolving Nuclear Star Clusters with Two-dimensional Monte Carlo Dynamical Simulations","authors":"Fupeng Zhang and Pau Amaro Seoane","doi":"10.3847/1538-4357/adaa7a","DOIUrl":"https://doi.org/10.3847/1538-4357/adaa7a","url":null,"abstract":"We recently developed a Monte Carlo method (GNC) that can simulate the dynamical evolution of a nuclear star cluster (NSC) with a massive black hole (MBH), where the two-body relaxations can be solved by the Fokker–Planck equations in energy and angular momentum space. Here we make a major update of GNC by integrating stellar potential and adiabatic invariant theory, so that we can study the self-consistent dynamics of NSCs with increasing mass of the MBH. We perform tests of the self-adaptation of cluster density due to MBH mass growth and Plummer core collapse, both finding consistent results with previous studies, the latter having a core collapse time of ∼17trh by GNC, where trh is the time of half-mass relaxation. We use GNC to study the cosmological evolution of the properties of NSCs and the mass of MBHs assuming that the mass growth of the MBH is due to loss-cone accretion of stars (e.g., tidal disruption of stars) and stellar black holes, and we compare the simulation results with the observations of NSCs in the Milky Way or nearby galaxies. It is possible for such a scenario to produce MBHs with mass 105–107M⊙ for NSCs with stellar mass of 106–109M⊙. In the Milky Way's NSC, to grow an MBH up to 4 × 106M⊙, its size needs to be ∼1.7 times more compact in early Universe than the current value. MBHs with current masses >6 × 107M⊙ seem difficult to explain by loss-cone accretion alone, and thus they may require other additional accretion channels, such as gas accretion.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143426981","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":"Hunting for Candidates of Changing-look Blazars Using Mclust Clustering Analysis","authors":"Shi-Ju Kang, Shan-Shan Ren, Yong-Gang Zheng and Qingwen Wu","doi":"10.3847/1538-4357/ada7ec","DOIUrl":"https://doi.org/10.3847/1538-4357/ada7ec","url":null,"abstract":"Changing-look blazars (CLBs) are blazars whose optical spectral lines at different epochs show significant changes and present a clear transition between standard FSRQ and BL Lacertae (BL Lac). Changing-look phenomena in blazars are highly significant for enhancing our understanding of certain physical problems of active galactic nuclei (AGNs), such as the potential mechanism of state transition in the accretion process of supermassive black holes in the central engine of AGNs, the possible intrinsic variation of the jet, and the connection between the accretion disk and the jet. Currently, the CLBs reported in the literature are still rare astronomical objects. In our previous work, we found that there are eight physical property parameters of CLBs located between those of FSRQs and BL Lacs. In order to search for more CLB candidates (CLBCs), we employed the mclust Gaussian mixture modeling clustering algorithm to perform clustering analysis for 255 subsets of the eight physical property parameters with 2250 blazars from 4FGL data release 3. We find that there are 29 subsets with three groups (corresponding to bl lacs, fsrqs, and CLBCs), in which there are four subsets with an adjusted Rand index greater than 0.610. The combined clustering results from the four subsets report that there are 111 CLBCs, which include 44 CLBs reported in previous literature and 67 new CLBCs, of which 11 are labeled as BL Lacs and 56 are labeled as FSRQs in the 4FGL catalog.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"51 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143426980","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":"Unraveling the Nature of HAWC J1844–034 with Fermi-LAT Data Analysis and Multiwavelength Modeling","authors":"Sovan Boxi, Saptarshi Ghosh and Nayantara Gupta","doi":"10.3847/1538-4357/adae0e","DOIUrl":"https://doi.org/10.3847/1538-4357/adae0e","url":null,"abstract":"The extended ultra-high-energy (UHE) gamma-ray source HAWC J1844–034 is closely associated with two other sources, HAWC J1843–032 and HWC J1846–025. Moreover, other gamma-ray observatories like HESS, LHAASO, and Tibet ASγ have detected UHE gamma-ray sources whose spatial positions coincide with the position of HAWC J1844–034. The UHE gamma-ray data from several observatories aid analysis of the spectral features of this source in detail at teraelectronvolt energies. Of the four pulsars near HAWC J1844–034, PSR J1844–0346 is closest to it and possibly supplies the cosmic-ray leptons to power this source. We have analyzed the Fermi–Large Area Telescope (LAT) data to explore this source’s morphology and identify its spectral features in the Fermi-LAT energy band. After removing the contribution of the pulsar to the gamma-ray spectral energy distribution (SED) by pulsar-phased analysis, we obtained upper limits on the photon flux and identified the gigaelectronvolt counterpart PS J1844.2–0342 in the Fermi-LAT energy band with more than 5σ significance, which may be a pulsar wind nebula (PWN). Finally, the multiwavelength SED is modeled, assuming HAWC J1844–034 is a PWN.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143426982","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":"Anomalous Neutral Hydrogen Column Densities in Local Interstellar Medium Clouds* * Based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS AR-09525.01A. These observations are associated with programs #12475 and #12596.","authors":"Jeffrey L. Linsky, Seth Redfield","doi":"10.3847/1538-4357/ada89e","DOIUrl":"https://doi.org/10.3847/1538-4357/ada89e","url":null,"abstract":"Analysis of high-resolution spectra of the hydrogen and deuterium Ly<italic toggle=\"yes\">α</italic> lines provides measurements of interstellar neutral hydrogen column densities <italic toggle=\"yes\">N</italic>(H <sc>i</sc>) to 113 stars within 50 pc of the Sun. Plots of <italic toggle=\"yes\">N</italic>(H <sc>i</sc>) versus distance through the LIC, G, Mic, and other clouds in the local interstellar medium (LISM) show very interesting properties. For the LIC and G clouds, nearly all of the observed neutral hydrogen occurs within 3 or 4 pc of the Sun with no significant additional neutral hydrogen at larger distances out to 50 pc, except for several sight lines with anomalously high <italic toggle=\"yes\">N</italic>(H <sc>i</sc>). Scatter about the mean hydrogen column density in the LIC is several times larger than the measurement errors. We evaluate several possible sources of the high <italic toggle=\"yes\">N</italic>(H <sc>i</sc>) sight lines. Seven sight lines with anomalously high <italic toggle=\"yes\">N</italic>(H <sc>i</sc>) are aligned perpendicular to the line connecting the centers of the LIC and G clouds where the two clouds merge creating a mixed cloud region. The high <italic toggle=\"yes\">N</italic>(H <sc>i</sc>) in these seven sight lines can be explained by their paths through an irregularly shaped mixed cloud region where the neutral hydrogen number density is the sum for both clouds. However, the most recent nearby supernova explosion created a shell that is seen in nearly the same direction perpendicular to the LIC/G axis and may also explain these seven high <italic toggle=\"yes\">N</italic>(H <sc>i</sc>) sight lines. Other possible explanations for the high <italic toggle=\"yes\">N</italic>(H <sc>i</sc>) sight lines include interstellar shocks, wakes produced by stars moving rapidly through the LISM, and regions where other clouds may overlap.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"56 1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143417425","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":"The Oxidation–Deuteration Processes of Large, Astronomically Relevant Cationic Polycyclic Aromatic Hydrocarbons","authors":"Xiaoyi Hu, Nian Zhao, Congcong Zhang, Xuejuan Yang, Alexander G. G. M. Tielens, Junfeng Zhen","doi":"10.3847/1538-4357/adabdf","DOIUrl":"https://doi.org/10.3847/1538-4357/adabdf","url":null,"abstract":"In interstellar environments, gas-phase polycyclic aromatic hydrocarbon (PAH) predominantly involves (photo)fragmentation, hydrogenation, and oxidation chemical routes, which lead to the formation of complex organic species. Here the gas-phase reactions between tribenzo-naphtho-pero-pyrene (TNPP, C₄₀H₁₈) cations and ultraviolet, ^18/16O or D atoms are investigated. The oxidized TNPP cations ([C₄₀H_18/17/16O_{<italic toggle=\"yes\">n</italic>}]⁺, <italic toggle=\"yes\">n</italic> = [1, 6]) are newly formed; the collision-induced deoxidation of oxidized TNPP cations is followed by the loss of HCO/CO units. With laser irradiation, the photo-deoxidation of oxidized TNPP cations is identified. Smaller PAH cations, [C_{40−<italic toggle=\"yes\">n</italic>}H_{18−<italic toggle=\"yes\">n</italic>}]⁺, with <italic toggle=\"yes\">n</italic> = [1, 5], i.e., PAHs containing odd carbon numbers (e.g., 39, 37 C atoms), are produced. Furthermore, the oxidized–deuterated TNPP cations ([C₄₀H_{<italic toggle=\"yes\">m</italic>}D_{<italic toggle=\"yes\">n</italic>}O_{<italic toggle=\"yes\">x</italic>}]⁺) are well formed upon simultaneous reaction with O and D atoms. The structure of the oxidized–deuterated TNPP cations and the bonding energy for these reaction pathways were investigated with theoretical calculations. Four oxidation bonding types are identified together with their evolution pathways. The reaction energy is relatively high, and the addition of O/D atoms to the carbon skeleton is a relatively random and independent event, i.e., with no restrictions or requirements for the carbon sites of PAH species. Consequently, the oxidized–deuterated states and forms of PAH compounds are intricate and complex. Furthermore, the calculations confirm that the loss of CO or H+CO is energetically preferable. Importantly, the formation of the carbonyl unit is confirmed. We infer that the collision/photo-induced deoxidation (loss of (H)CO units) of oxidized PAH species is involved in the top-down evolution routes of large PAHs and effectively catalyzes the potential formation of small oxygen-containing species (e.g., OH/HCO/CO) in the interstellar medium.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143417431","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":"Adiabatic Index in Fluid Models of Collisionless Black Hole Accretion","authors":"Charles F. Gammie","doi":"10.3847/1538-4357/adaea3","DOIUrl":"https://doi.org/10.3847/1538-4357/adaea3","url":null,"abstract":"Models of highly sub-Eddington accretion onto black holes commonly use a single-fluid model for the collisionless, near-horizon plasma. These models must specify an equation of state. It is common to use an ideal gas with <italic toggle=\"yes\">p</italic> = (<italic toggle=\"yes\">γ</italic> − 1)<italic toggle=\"yes\">u</italic> and <italic toggle=\"yes\">γ</italic> = 4/3, 13/9, or 5/3, but these produce significantly different outcomes. We discuss the origins of this discrepancy and the assumptions underlying the single-fluid model. The main result of this investigation is that under conditions relevant to low-luminosity black hole accretion the best choice of single-fluid adiabatic index is close to but slightly less than 5/3. Along the way we provide a simple equilibrium model for the relation between the ion-to-electron dissipation ratio and the ion-to-electron temperature ratio, and explore the implications for electron temperature fluctuations in Event Horizon Telescope sources.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143417433","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":"The Fallibility of Equipartition Magnetic Field Strengths from Synchrotron Emission Using Synthetically Observed Galaxies","authors":"Tara Dacunha, Sergio Martin-Alvarez, Susan E. Clark, Enrique Lopez-Rodriguez","doi":"10.3847/1538-4357/adab72","DOIUrl":"https://doi.org/10.3847/1538-4357/adab72","url":null,"abstract":"Understanding the role that magnetic fields play on the stage of galaxy formation requires accurate methods for inferring the properties of extragalactic magnetic fields. Radio synchrotron emission has been the most promising avenue to infer magnetic field strengths across galaxies, with the application of a central assumption: that galactic cosmic rays are in energy equipartition with the magnetic field. In this work, we leverage flexible synthetic observations of a high-resolution magnetohydrodynamic simulation of a Milky Way–like galaxy to review whether true equipartition is capable of reproducing radio observations of galaxies, and investigate its impact on the inference of magnetic field strengths when varying the properties and density distribution of the cosmic rays. We find that imposing equipartition (regardless of scale length) results in cosmic ray electron densities that are unable to generate either the amplitude or the shape of the radio intensity profiles typically observed in spiral galaxies. Instead, observationally motivated smooth distributions of cosmic ray electrons across the galaxy provide a remarkable match to observations. We further demonstrate that assuming equipartition with those mock observations can lead to significant overestimation of the magnetic field strength. This misestimation varies with cosmic ray electron densities, cosmic ray spectrum power-law index, and galactic environment, aggravated in inter-arm regions and attenuated in star-forming regions. Our results promote caution when assuming equipartition in observations, and suggest that additional theoretical and numerical work is required to leverage the upcoming generation of radio observations poised to revolutionize our understanding of astrophysical magnetic fields.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143417430","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":"Resolving an Asteroseismic Catastrophe: Structural Diagnostics from p-mode Phase Functions off the Main Sequence","authors":"J. M. Joel Ong, Christopher J. Lindsay, Claudia Reyes, Dennis Stello, Ian W. Roxburgh","doi":"10.3847/1538-4357/ada949","DOIUrl":"https://doi.org/10.3847/1538-4357/ada949","url":null,"abstract":"On the main sequence, the asteroseismic small frequency separation <italic toggle=\"yes\">δν</italic>₀₂ between radial and quadrupole <italic toggle=\"yes\">p</italic>-modes is customarily interpreted to be a direct diagnostic of internal structure. Such an interpretation is based on a well-known integral estimator relating <italic toggle=\"yes\">δν</italic>₀₂ to a radially averaged sound-speed gradient. However, this estimator fails, catastrophically, when evaluated on structural models of red giants: their small separations must therefore be interpreted differently. We derive a single expression that both reduces to the classical estimator when applied to main-sequence stellar models and reproduces the qualitative features of the small separation for stellar models of very evolved red giants. This expression indicates that the small separations of red giants scale primarily with their global seismic properties as <inline-formula>\u0000<tex-math>\u0000<?CDATA $delta {nu }_{02}propto {rm{Delta }}{nu }^{2}/{nu }_{{rm{max }}}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mi>δ</mml:mi><mml:msub><mml:mrow><mml:mi>ν</mml:mi></mml:mrow><mml:mrow><mml:mn>02</mml:mn></mml:mrow></mml:msub><mml:mo>∝</mml:mo><mml:mo mathvariant=\"normal\">Δ</mml:mo><mml:msup><mml:mrow><mml:mi>ν</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup><mml:mo>/</mml:mo><mml:msub><mml:mrow><mml:mi>ν</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant=\"normal\">max</mml:mi></mml:mrow></mml:msub></mml:math>\u0000<inline-graphic xlink:href=\"apjada949ieqn1.gif\"></inline-graphic>\u0000</inline-formula>, rather than being in any way sensitive to their internal structure. Departures from this asymptotic behavior, during the transition from the main-sequence to red giant regimes, have been recently reported in open-cluster Christensen–Dalsgaard (C-D) diagrams from K2 mission data. Investigating them in detail, we demonstrate that they occur when the convective envelope boundary passes a specific acoustic distance—roughly one-third of a wavelength at <inline-formula>\u0000<tex-math>\u0000<?CDATA ${nu }_{{rm{max }}}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:msub><mml:mrow><mml:mi>ν</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant=\"normal\">max</mml:mi></mml:mrow></mml:msub></mml:math>\u0000<inline-graphic xlink:href=\"apjada949ieqn2.gif\"></inline-graphic>\u0000</inline-formula>—from the center of the star, at which point radial modes become maximally sensitive to the position of the boundary. The shape of the corresponding features on <italic toggle=\"yes\">ϵ</italic>_{<italic toggle=\"yes\">p</italic>} and C-D (or <italic toggle=\"yes\">r</italic>₀₂) diagrams may be useful in constraining the nature of convective boundary mixing in the context of undershooting beneath a convective envelope.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"184 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143417428","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":"The Impact of Extended CO2 Cross Sections on Temperate Anoxic Planet Atmospheres","authors":"Wynter Broussard, Edward W. Schwieterman, Clara Sousa-Silva, Grace Sanger-Johnson, Sukrit Ranjan, Olivia Venot","doi":"10.3847/1538-4357/adaaf0","DOIUrl":"https://doi.org/10.3847/1538-4357/adaaf0","url":null,"abstract":"Our interpretation of terrestrial exoplanet atmospheric spectra will always be limited by the accuracy of the data we use as input in our forward and retrieval models. Ultraviolet molecular absorption cross sections are one category of these essential model inputs; however, they are often poorly characterized at the longest wavelengths relevant to photodissociation. Photolysis reactions dominate the chemical kinetics of temperate terrestrial planet atmospheres. One molecule of particular importance is CO₂, which is likely present in all terrestrial planet atmospheres. The photolysis of CO₂ can introduce CO and O, as well as shield tropospheric water vapor from undergoing photolysis. This is important because H₂O photolysis produces OH, which serves as a major reactive sink to many atmospheric trace gases. Here, we construct CO₂ cross-section prescriptions at 195 K and 300 K extrapolated beyond 200 nm from measured cross sections. We compare results from the implementation of these new cross sections to the most commonly used CO₂ prescriptions for temperate terrestrial planets with Archean-like atmospheres. We generally find that the observational consequences of CO₂ dissociation beyond 200 nm are minimal so long as our least conservative (highest opacity) prescription can be ruled out. Moreover, implementing our recommended extended CO₂ cross sections does not substantially alter previous results that show the consequential photochemical impact of extended H₂O cross sections.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"36 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143418371","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 Novel Survey for Young Substellar Objects with the W-band Filter. VII. Water-bearing Objects in the Core of the ρ Ophiuchi Cloud Complex","authors":"Tanvi Sharma, Wen Ping Chen, Beth Biller, Loïc Albert, Belinda Damian, Jessy Jose, Bhavana Lalchand, Michael C. Liu, Yumiko Oasa","doi":"10.3847/1538-4357/ada3c3","DOIUrl":"https://doi.org/10.3847/1538-4357/ada3c3","url":null,"abstract":"We present a study of very low mass stars and brown dwarfs in the rich star-forming core of the <italic toggle=\"yes\">ρ</italic> Ophiuchi cloud complex. The selection of the sample relies on detecting the inherent water absorption characteristic in young substellar objects. Of the 22 water-bearing candidates selected, 15 have a spectral type of M6 or later. Brown dwarf candidates too faint for membership determination by Gaia have their proper motions derived by deep-infrared images spanning 6 yr. Astrometric analysis confirms 21/22 sources as members, with one identified as a contaminant. Infrared colors and the spectral energy distribution of each water-bearing candidate are used to diagnose the mass, age, and possible existence of circumstellar dust. A total of 15 sources exhibit evidence of disks in their spectral energy distributions, as late as in M8-type objects. Spectroscopy for bright candidates has confirmed one as an M8 member and verified two sources (with disks) exhibiting signatures of magnetospheric accretion.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143417403","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}