@article{21999, abstract = {JWST has revealed an abundance of supermassive black holes (BHs) in the early Universe, and yet the lowest mass seed BHs that gave rise to these populations remain elusive. Here, we present a systematic search for broad-line active galactic nuclei (AGNs) in some of the faintest high-z galaxies surveyed yet by combining ultra-deep JWST/NIRSpec G395M spectroscopy with the strong lensing aid in AS1063. By employing the profile of the [O iii]λ5007 emission lines as a template for narrow-line components and carefully cross-validating with mock observations, we identify a sample of 10 broad-line AGNs at 4.5 < z < 7.0 (eight secure, two tentative). The inferred BH masses from the broad Hα line explore the intermediate BH mass regime down to ∼105.5 M⊙. The stellar mass (M*) is estimated with a galaxy+AGN composite model, and we find the BH to stellar mass ratio spans down to MBH/M* ≲ 0.1%, unveiling populations on the empirical MBH–M* relation observed in the local Universe. We also derive the BH mass function and investigate its low-mass end at this epoch. While we confirm the agreement of our results with previous studies at MBH ≳ 106.5M⊙, we find the mass range of ∼105.5 M⊙ features an enhanced abundance with respect to the extrapolated best-fit Schechter function. Comparison with theoretical models suggests that a possible origin for this enhanced abundance is the direct-collapse BH formation, supporting the scenario that the direct collapse of massive gas clouds is a significant pathway for the earliest supermassive BHs.}, author = {Fei, Qinyue and Fujimoto, Seiji and Naidu, Rohan P. and Chisholm, John and Atek, Hakim and Brammer, Gabriel and Asada, Yoshihisa and Berg, Danielle A. and Bromm, Volker and Furtak, Lukas J. and Greene, Jenny E. and Hsiao, Tiger Yu Yang and Jeon, Junehyoung and Kokorev, Vasily and Matthee, Jorryt J and Natarajan, Priyamvada and Pan, Richard and Richard, Johan and Saldana-Lopez, Alberto and Schaerer, Daniel and Volonteri, Marta and Zitrin, Adi}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{A GLIMPSE of intermediate mass Black Holes in the epoch of reionization: Witnessing the descendants of direct collapse?}}, doi = {10.3847/1538-4357/ae6248}, volume = {1003}, year = {2026}, } @article{21705, abstract = {We report the discovery of ATLAS J101342.5−451656.8 (hereafter ATLAS J1013−4516), an 8.56 minute orbital-period mass-transferring AM Canum Venaticorum (AM CVn) binary with a mean Gaia magnitude of G = 19.51, identified via periodic variability in light curves from the Asteroid Terrestrial-impact Last Alert System (ATLAS) of Gaia white dwarf candidates. Follow-up with the Large Lenslet Array Magellan Spectrograph shows a helium-dominated accretion disk, and high-speed ULTRACAM photometry reveals pronounced primary and secondary eclipses. We construct a decade-long timing baseline leveraging light curves from the ATLAS and Gaia surveys, as well as the high-speed imagers ULTRACAM on the New Energy Telescope and proto-Lightspeed on the Magellan Clay telescope. From this timing baseline, we measure an orbital period derivative of P 1.60 0.07 10 = ± × 12 s s−1. Interpreted in the context of stable mass transfer, the magnitude and sign of P indicate that the orbital evolution is governed by the interplay between gravitationalwave-driven angular-momentum losses and mass transfer, directly probing the donor’s structural response to mass loss. We constrain the accretor and donor mass based on stable mass-transfer arguments assuming angularmomentum loss dominated by gravitational-wave emission, allowing us to infer the characteristic gravitational wave strain of the binary for future space-based GW observatories such as the Laser Interferometer Space Antenna (LISA). We predict a characteristic strain corresponding to a 4 yr LISA signal-to-noise ratio ≳10, establishing ATLAS J1013−4516 as a strong prospective LISA source that will probe long-term orbital evolution in the mass-transferring regime.}, author = {Chickles, Emma T. and Chakraborty, Joheen and Burdge, Kevin B. and Dhillon, Vik S. and Draghis, Paul and El-Badry, Kareem and Green, Matthew J. and Householder, Aaron and Hughes, Sarah and Layden, Christopher and Littlefair, Stuart P. and Munday, James and Pelisoli, Ingrid and Redden, Maya S. and Tonry, John and van Roestel, Joannes C and Angile, Francesco Elio and Brown, Alex J. and Segura, Noel Castro and Dinsmore, Jack and Dyer, Martin and Furesz, Gabor and Gabutti, Michelle and Garbutt, James and García-Mejía, Juliana and Jarvis, Daniel and Kennedy, Mark R. and Kerry, Paul and Mccormac, James and Mo, Geoffrey and Osip, Dave and Parsons, Steven and Pike, Eleanor and Piotrowski, John J. and Romani, Roger W. and Sahman, David and Simcoe, Rob}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{An eclipsing 8.56 minutes orbital period mass-transferring binary}}, doi = {10.3847/1538-4357/ae4871}, volume = {1000}, year = {2026}, } @article{21710, abstract = {Early results from JWST suggest that Epoch of Reionization (EoR) galaxies produce copious ionizing photons, which, if they escape efficiently, could cause reionization to occur too early. We study this problem using JWST imaging and prism spectroscopy for 412 galaxies at 4.5 < z < 9.0. We fit these data simultaneously with stellar population and nebular emission models that include a parameter for the fraction of ionizing photons that escape the galaxy, fesc. We find that the ionization production efficiency, ξion = Q(H0)/LUV, increases with redshift and decreasing UV luminosity, but shows significant scatter, (log ion z, MUV) 0.3 dex. The inferred escape fractions averaged over the population are low, ranging from〈fesc〉 ≃ 2.6% ± 1.4% at 6 < z < 9 to 6.5% ± 2.2% at 4.5 < z < 6, with weak or no indication of evolution with redshift. This implies that in our models most of the ionizing photons need to be absorbed to account for the nebular emission. We compute the impact of our results on reionization, including the distributions for ξion and fesc, and the evolution and uncertainty of the UV luminosity function. Considering galaxies brighter than MUV < −16 mag would produce an intergalactic medium hydrogen-ionized fraction of xe = 0.5 at 5.3 < z < 5.8, possibly too late compared to constraints from from quasistellar object (QSO) sight lines. Including fainter galaxies, MUV < −14 mag, we obtain xe = 0.5 at 6.0 < z < 8.1, fully consistent with QSO and cosmic microwave background data. This implies that EoR galaxies produce plenty of ionizing photons, but that these do not efficiently escape. This may be a result of high gas column densities combined with burstier star formation histories, which limit the time massive stars are able to clear channels through the gas for ionizing photons to escape.}, author = {Papovich, Casey and Cole, Justin W. and Hu, Weida and Finkelstein, Steven L. and Shen, Lu and Arrabal Haro, Pablo and Amorín, Ricardo O. and Backhaus, Bren E. and Bagley, Micaela B. and Bhatawdekar, Rachana and Calabrò, Antonello and Carnall, Adam C. and Cleri, Nikko J. and Daddi, Emanuele and Dickinson, Mark and Grogin, Norman A. and Holwerda, Benne W. and Jaskot, Anne E. and Koekemoer, Anton M. and Llerena, Mario and Lucas, Ray A. and Mascia, Sara and Pacucci, Fabio and Pentericci, Laura and Pérez-González, Pablo G. and Pirzkal, Nor and Raghunathan, Srinivasan and Seillé, Lise Marie and Somerville, Rachel S. and Yung, L. Y.Aaron}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, publisher = {IOP Publishing}, title = {{Galaxies in the epoch of reionization are all bark and no bite-plenty of ionizing photons, low escape fractions}}, doi = {10.3847/1538-4357/ae3b25}, volume = {1000}, year = {2026}, } @article{21712, abstract = {Supermassive black hole binary (SMBHB) systems are expected to form as a consequence of galaxy mergers. At subparsec separations, SMBHBs can be identified as quasars with periodic variability, with previous periodicity searches uncovering significant candidates. However, these searches focused primarily on sinusoidal signals, while theoretical models and hydrodynamical simulations predict that binaries produce more complex non-sinusoidal pulse shapes. Here we examine the efficacy of the Lomb–Scargle periodogram (LSP; one of the most popular tools for periodicity searches in unevenly sampled lightcurves) to detect periodicities with a sawtooth shape mimicking results of hydrodynamical simulations. We simulate idealized well-sampled lightcurves, lightcurves that mimic the data in the Palomar Transient Factory (PTF) analyzed in M. Charisi et al. (2016), and lightcurves that resemble our expectations for single-band data in the upcoming Legacy Survey of Space and Time (LSST) of the Rubin Observatory. We approximate quasar variability with a damped random walk (DRW) model, inject sinusoidal and sawtooth pulse shapes, and assess their statistical significance. We find that in the presence of red noise, the LSP detects a relatively low fraction of the sinusoidal signals (∼45%, ∼24%, and ∼23%, in the PTF-like, idealized, and LSST-like lightcurves, respectively). The fraction is significantly reduced for sawtooth periodicity (with only ∼9% in PTF-like and ∼1% in idealized and LSST-like lightcurves). These low recovery rates imply that previous searches have missed the large majority of binaries. They also have significant implications for the detection of SMBHBs in upcoming LSST necessitating the development of advanced tools that go beyond the simple LSP.}, author = {Lin, Allison and Charisi, Maria and Haiman, Zoltán}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{Lomb-scargle periodogram struggles with non-sinusoidal supermassive Black Hole binary signatures in quasar lightcurves}}, doi = {10.3847/1538-4357/ae29a7}, volume = {997}, year = {2026}, } @article{21715, abstract = {New populations of red active galactic nuclei (known as “little red dots”) discovered by JWST exhibit remarkable spectral energy distributions. Leveraging X-ray through far-infrared observations of two of the most luminous known little red dots, we directly measure their bolometric luminosities. We find evidence that more than half of the bolometric luminosity likely emerges in the rest-frame optical, with Lbol/L5100 = 5, roughly half the value for “standard” active galactic nuclei. Meanwhile, the X-ray emitting corona, UV-emitting blackbody, and reprocessed mid to far-infrared emission are all considerably subdominant, assuming that the far-infrared luminosity is well below current measured limits. We present new bolometric corrections that dramatically lower inferred bolometric luminosities by a factor of 10 compared to published values in the literature. These bolometric corrections are in accord with expectations from models in which gas absorption and reprocessing are responsible for the red rest-frame optical colors of little red dots. We discuss how this lowered luminosity scale suggests a lower mass scale for the population by at least an order of magnitude (e.g., ∼105–107 M⊙ black holes, and ∼108 M⊙ galaxies), alleviating tensions with clustering, overmassive black holes, and the integrated black hole mass density in the Universe.}, author = {Greene, Jenny E. and Setton, David J. and Furtak, Lukas J. and Naidu, Rohan P. and Volonteri, Marta and Dayal, Pratika and Labbe, Ivo and Van Dokkum, Pieter and Bezanson, Rachel and Brammer, Gabriel and Cutler, Sam E. and Glazebrook, Karl and De Graaff, Anna and Hirschmann, Michaela and Hviding, Raphael E. and Kokorev, Vasily and Leja, Joel and Liu, Hanpu and Ma, Yilun and Matthee, Jorryt J and Nanayakkara, Themiya and Oesch, Pascal A. and Pan, Richard and Price, Sedona H. and Spilker, Justin S. and Wang, Bingjie and Weaver, John R. and Whitaker, Katherine E. and Williams, Christina C. and Zitrin, Adi}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{What you see is what you get: Empirically measured bolometric luminosities of Little Red Dots}}, doi = {10.3847/1538-4357/ae1836}, volume = {996}, year = {2026}, } @article{21725, abstract = {The initial–final mass relation (IFMR) links a star’s birth mass to the mass of its white dwarf (WD) remnant, providing key constraints on stellar evolution. Open clusters offer the most straightforward way to empirically determine the IFMR, as their well-defined ages allow for direct progenitor lifetime estimates. We construct the most comprehensive open cluster WD IFMR to date by combining new spectroscopy of 22 WDs with an extensive literature review of WDs with strong cluster associations. To minimize systematics, we restrict our analysis to spectroscopically confirmed hydrogen-atmosphere (DA) WDs consistent with single-stellar origins. We separately analyze a subset with reliable Gaia-based astrometric membership assessments, as well as a full sample that adds WDs with strong cluster associations whose membership cannot be reliably assessed with Gaia. The Gaia-based sample includes 69 spectroscopically confirmed DA WDs, more than doubling the sample size of previous Gaia-based open cluster IFMRs. The full sample, which includes 53 additional literature WDs, increases the total number of cluster WDs by over 50% relative to earlier works. We provide functional forms for both the Gaia-based and full-sample IFMRs. The Gaia-based result useful for Mi � 2.67 M⊙ is Mf = [0.179 0.100H (Mi 3.84 M )] × (Mi 3.84 M ) + 0.628 M , where H(x) is the Heaviside step function. Comparing our IFMR to recent literature, we identify significant deviations from best-fit IFMRs derived from both Gaia-based volume-limited samples of field WDs and double WD binaries, with the largest discrepancy occurring for initial masses of about 5 M⊙.}, author = {Miller, David R. and Caiazzo, Ilaria and Heyl, Jeremy and Richer, Harvey B. and Hollands, Mark A. and Tremblay, Pier Emmanuel and El-Badry, Kareem and Rodriguez, Antonio C. and Vanderbosch, Zachary P.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, keywords = {White dwarf stars, Open star clusters, Compact objects, Stellar evolution}, number = {1}, publisher = {IOP Publishing}, title = {{The White Dwarf initial–final mass relation from open clusters in Gaia DR3}}, doi = {10.3847/1538-4357/ae18c8}, volume = {996}, year = {2026}, } @article{21760, abstract = {3I/ATLAS is the third interstellar object discovered to date, following 1I/‘Oumuamua and 2I/Borisov. Its unusually high excess velocity and active cometary nature make it a key probe of the Galactic population of icy planetesimals. Understanding its origin requires its past trajectory through the Galaxy to be traced and the possible role of stellar encounters to be assessed, both as a potential origin and a perturber to its orbit. We integrated the orbit of 3I/ATLAS backward in time for 10 Myr, together with a sample of Gaia DR3 stars with high-quality astrometry and radial velocities, to identify close passages within 2 pc. We identify 93 nominal encounters, 62 of which are significant at the 2σ level. However, none of these encounters produced any meaningful perturbation. The strongest perturber Gaia DR3 6863591389529611264 at 0.30 pc and with a relative velocity of 35 km s−1, imparted only a velocity change of ∣Δv∣ ≃ 5 × 10−4 km s−1 to the orbit of 3I/ATLAS. Our results indicate that no stellar flybys within the past 10 Myr and 500 pc contained in Gaia DR3 can account for the present trajectory of 3I/ATLAS or be associated with its origin. We further show that 3I/ATLAS is kinematically consistent with a thin-disk population, despite its large peculiar velocity.}, author = {Pérez-Couto, X. and Torres Rodriguez, Santiago and Villaver, E. and Mustill, A. J. and Manteiga, M.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{3I/ATLAS: In search of the witnesses to its voyage}}, doi = {10.3847/1538-4357/ae56ff}, volume = {1001}, year = {2026}, } @article{21844, abstract = {Little red dots (LRDs) are a newly identified class of broad-line active galactic nuclei (AGNs) with a distinctive V-shaped spectrum characterized by red optical and blue UV continuum emission. Their high abundance at redshifts of z ∼ 6–8 and decline at lower redshifts suggest a transient origin. We propose that the spectral shape of LRDs originates from compact binary black hole systems, in which each black hole is surrounded by a mini-disk and embedded within a larger circumbinary disk. With a binary separation of ≲103 Schwarzschild radii, the Wien tail of a T ≃ 5000 K blackbody spectrum at the inner edge of the circumbinary disk produces the red optical emission, while the mini-disks power the UV continuum. Binary torques carve out a gap between the circumbinary disk and the mini-disks, setting the turnover wavelength of the V-shaped spectrum around the Balmer limit. This scenario naturally reproduces LRD spectra requiring only modest dust attenuation (AV ≲ 1 mag), resolving overestimated luminosities for LRDs in previous studies and alleviating a tension with the so-called Sołtan argument. This model predicts distinct spectral evolution as the binary orbit decays through binary disk interactions and gravitational-wave (GW) emission, linking early-stage “proto-LRD” binaries to the broader AGN population and late-stage “LRD descendants” to coalescing binaries detectable in GW experiments.}, author = {Inayoshi, Kohei and Shangguan, Jinyi and Chen, Xian and Ho, Luis C. and Haiman, Zoltán}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, publisher = {IOP Publishing}, title = {{The emergence of Little Red Dots from binary massive black holes}}, doi = {10.3847/1538-4357/ae548d}, volume = {1002}, year = {2026}, } @article{21882, abstract = {The nature of little red dots (LRDs) has largely been investigated through their continuum emission, with lines assumed to arise from a broad-line region. In this paper, we instead use recombination lines to infer the intrinsic properties of the central engine. Our analysis first reveals a tension between the ionizing properties implied from Hα and He ii λ4686. The high Hα EWs require copious H-ionizing photons, more than the bluest active galactic nucleus (AGN) ionizing spectra can provide. In contrast, He ii emission is marginally detected, and its low EW is, at most, consistent with the softest AGN spectra. The low He ii/Hβ (∼10−2, <20× local AGN median) further points to an unusually soft ionizing spectrum. We extend our analysis to dense gas envelopes (quasi-star/black-hole star) and find that hydrogen recombination lines become optically thick and lose diagnostic power, but He ii remains optically thin and a robust tracer. Photoionization modeling with Cloudy rules out standard AGN accretion disk spectra. Alternative explanations include exotic AGN with red rest-optical emission, high average optical depth (>10) from gas/dust, and soft ionizing spectra with abundant H-ionizing photons, consistent with, e.g., a cold accretion disk or a composite of AGN and stars. The latter is an intriguing scenario since high hydrogen densities are highly conducive for star formation, and nuclear star clusters are found in the vicinity of local massive black holes. While previous studies have mostly focused on features dominated by the absorbing hydrogen cloud, the He ii-based diagnostic proposed here represents a crucial step toward understanding the central engine of LRDs.}, author = {Wang, Bingjie and Leja, Joel and Katz, Harley and Inayoshi, Kohei and Cleri, Nikko J. and De Graaff, Anna and Hviding, Raphael E. and Van Dokkum, Pieter and Greene, Jenny E. and Labbé, Ivo and Matthee, Jorryt J and Mcconachie, Ian and Naidu, Rohan P. and Nelson, Erica J.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, publisher = {IOP Publishing}, title = {{The missing hard photons of Little Red Dots: Their incident ionizing spectra resemble massive stars}}, doi = {10.3847/1538-4357/ae5bab}, volume = {1003}, year = {2026}, } @article{21930, abstract = {We present the discovery of extreme nitrogen enrichment by Wolf Rayet nitrogen (WN) stars in the metal-poor (∼10%Z⊙), lensed, compact (Reff ∼ 20 pc) galaxy RXCJ2248 at z = 6.1, revealed by unprecedentedly deep JWST/NIRSpec medium-resolution spectroscopy from the GLIMPSE-D Survey. The exquisite signal-to-noise ratio reveals multiple high-ionization nebular lines and broad Balmer and [O III] components (FWHM ∼700–3000 km s −1 ). We detect broadened He II λ1640 and λ4687 (FWHM ∼ 530 km s −1 ) and strong N III λ4642 emission consistent with a population of WN stars, making RXCJ2248 the most distant galaxy with confirmed Wolf Rayet (WR) features to date. We measure the multiphase nebular density across five ions, the direct-method metallicity ( 12 + log(O/H) = 7.753 ± 0.025 ), and a nonuniform elemental enrichment pattern of extreme N/O enhancement ( log(N/O) = 0.391 ± 0.037 from N+, N+2 , and N+3 ) but suppressed C/O relative to empirical C/N trends. We show that this abundance pattern can be explained by enrichment from a dual-burst with a low WR carbon/WN ratio, as expected at low metallicities. Crucially, these signatures can only arise during a brief, rare evolutionary window shortly after a burst (∼3–6 Myr), when WN stars dominate chemical feedback but before dilution by later yields (e.g., supernovae). The observed frequency of strong N emitters at high−z implies a ∼50 Myr burst duty cycle, suggesting that N/O outliers may represent a brief but ubiquitous phase in the evolution of highly star-forming early galaxies. The WN detection in RXCJ2248, therefore, provides the first direct evidence of WR-driven nitrogen enrichment in the first billion years of the Universe and a novel timing argument for the bursty star formation cycles that shaped galaxies at cosmic dawn.}, author = {Berg, Danielle A. and Naidu, Rohan P. and Chisholm, John and Atek, Hakim and Fujimoto, Seiji and Kokorev, Vasily and Furtak, Lukas J. and Kobayashi, Chiaki and Schaerer, Daniel and Adamo, Angela and Fei, Qinyue and Korber, Damien and Matthee, Jorryt J and Marques-Chaves, Rui and Martinez, Zorayda and Mcquinn, Kristen B.W. and Muñoz, Julian B. and Oesch, Pascal A. and Saldana-Lopez, Alberto and Stark, Daniel P. and Stephenson, Mabel G. and Hsiao, Tiger Yu Yang}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{A fleeting GLIMPSE of N/O enrichment at cosmic dawn: Evidence for Wolf Rayet N stars in a z = 6.1 galaxy}}, doi = {10.3847/1538-4357/ae5e4c}, volume = {1003}, year = {2026}, } @article{22264, abstract = {The correlation between galaxy stellar mass and gas-phase metallicity, known as the mass–metallicity relation (MZR), gives key insights into the processes that govern galaxy evolution. However, unquantified observational and selection biases can result in systematic errors in attempts to recover the intrinsic MZR, particularly at higher redshifts. We characterize the MZR at z ∼ 3–6 within a fully Bayesian framework using JWST/NIRSpec spectra of 191 galaxies from the RUBIES survey. We forward model the observed mass–metallicity surface using prospector-generated spectra to account for two selection biases: the survey selection function and the success in observing high signal-to-noise ratio emission lines. We demonstrate that the RUBIES selection function, based on F444W magnitude and F150W – F444W color, has a negligible effect on our measured MZR. A correct treatment of the non-Gaussian metallicity uncertainties from strong-line calibrations lowers the derived MZR normalization by 0.2 dex and flattens the slope by ∼20%; forward modeling the effect of emission line observability steepens the slope by ∼15%. Both of these biases must be taken into account in order to properly measure the intrinsic MZR. This novel forward-modeling process motivates careful consideration of selection functions in future surveys, and paves the way for robust, high-redshift chemical enrichment studies that trace the evolution of the MZR across cosmic time.}, author = {Lewis, Zach and Maseda, Michael V. and De Graaff, Anna and Leja, Joel and Wang, Bingjie and Rix, Hans Walter and Mcconachie, Ian and Cleri, Nikko J. and Bezanson, Rachel and Boogaard, Leindert A. and Brammer, Gabriel and Greene, Jenny E. and Hirschmann, Michaela and Katz, Harley and Labbé, Ivo and Matthee, Jorryt J and Miller, Tim B. and Naidu, Rohan P. and Oesch, Pascal A. and Setton, David J. and Suess, Katherine A. and Weibel, Andrea and Whitaker, Katherine E. and Williams, Christina C.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, keywords = {Galaxy evolution, Chemical enrichment, Metallicity, Galaxy abundances, Scaling relations}, number = {2}, publisher = {IOP Publishing}, title = {{The mass–metallicity relation and its observational effects at z ∼ 3–6}}, doi = {10.3847/1538-4357/ae7bfc}, volume = {1005}, year = {2026}, } @article{22262, abstract = {Mixed modes are observed in many low-mass evolved stars. They provide information about core rotation rates of these stars, which are lower than predicted by stellar evolution models. The mixed modes themselves have been invoked as an angular momentum (AM) transport mechanism, but estimating their transport efficiency requires knowledge of their amplitudes. We constrain, for the first time, the mixed-mode amplitudes in 2D hydrodynamical simulations of a 1.3M⊙ red giant using the code MUSIC. We perform two simulations with outer radial truncations at fractional radii ro/r⋆ = 0.90 and 0.98. We compare the modes in the simulation with those found using both GYRE and a Dedalus eigenvalue solver. Excellent frequency agreement is found for all p-dominated modes, with minor discrepancies for g-dominated modes, especially in the frequency range [60, 240] μHz. We find excellent eigenfunction agreement for all modes except those in this frequency range. According to empirical predictions, the largest kinetic energies are located around Vmax= 312.μHz, but in both simulations, the modes with frequencies of ν < 50 μHz have the largest kinetic energies. In the simulation with r/r⋆ = 0.98, the simulated modes have extrapolated surface velocities comparable to the empirical predictions, with the highest surface velocities in a bell-shaped curve peaking around ν = 700 μHz. The extrapolated surface velocities of the low-frequency modes are small and thus hard to observe, but their large kinetic energies deeper in the interior could significantly impact AM transport, which has not yet been investigated.}, author = {De Vries, Nils B. and Le Saux, Arthur and Baraffe, Isabelle and Guillet, Thomas and Townsend, Richard H.D. and Leclerc, Armand and Morison, Adrien}, issn = {1538-4357}, journal = {The Astrophysical Journal}, keywords = {Stellar physics, Stellar interiors, Asteroseismology, Stellar oscillations, Hydrodynamical simulations}, number = {2}, publisher = {IOP Publishing}, title = {{Revealing mixed modes in compressible hydrodynamical simulations of red giant stars}}, doi = {10.3847/1538-4357/ae7a3c}, volume = {1005}, year = {2026}, } @article{22296, abstract = {The detection of strong Balmer breaks and absorption features in Little Red Dots (LRDs) suggests they host active galactic nuclei embedded within dense gas envelopes, potentially powered by super-Eddington accretion. We present GLIMPSE-17775, a luminous (Lbol ∼ 1045 erg s−1) LRD at z = 3.501 behind Abell S1063 (μ ∼ 2), observed with deep JWST/NIRCam and a ∼20 hr (80 hr delensed) NIRSpec G395M spectrum. The data reveal over 40 emission and absorption features, including a rich forest of low-ionization Fe ii lines and numerous broad hydrogen recombination transitions. We use this depth to test the dense-gas interpretation through five independent diagnostics. Nearly all permitted lines show exponential wings with consistent FWHM, a signature of Thomson scattering requiring ne ≳ 108 cm−3. Adopting this width yields MBH ∼ 106.7M⊙, a factor of 10 lower than Gaussian fits, and λEdd ∼ 1.8. Additional diagnostics support the same picture: a pronounced Balmer break (fν,4050/fν,3670 = 2.0 ± 0.1), enhanced He i λ7065 and λ10830 with P-Cygni absorption, Bowen-fluorescent O i λ8446–λ11290 emission requiring Lyβ pumping, and 16 Fe ii lines matching fluorescence models. These features indicate a dense (n ∼ 108 cm−3), partially ionized cocoon where scattering and fluorescence dominate line formation, providing strong evidence that at least some LRDs are powered by super-Eddington black hole growth in the early Universe.}, author = {Kokorev, Vasily and Chisholm, John and Naidu, Rohan P. and Fujimoto, Seiji and Atek, Hakim and Brammer, Gabriel and Finkelstein, Steven L. and Akins, Hollis B. and Berg, Danielle A. and Furtak, Lukas J. and Fei, Qinyue and Hsiao, Tiger Yu-Yang and Labbé, Ivo and Matthee, Jorryt J and Muñoz, Julian B. and Oesch, Pascal A. and Pan, Richard and Rinaldi, Pierluigi and Saldana-Lopez, Alberto and Schaerer, Daniel and Volonteri, Marta and Zitrin, Adi}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{The Deepest GLIMPSE of a dense gas cocoon enshrouding a Little Red Dot}}, doi = {10.3847/1538-4357/ae4ed7}, volume = {1004}, year = {2026}, } @article{22364, abstract = {Finding the first generation of (Population III or Pop III) stars is one of the most ambitious and exciting challenges of astrophysics. JWST opened concrete prospects for their detection during the Epoch of Reionization, where increasing evidence suggests that residual Pop III formation may persist, even within pristine pockets of high-mass halos, due to inhomogeneous enrichment. However, the identification of Pop III stars within globally enriched environments will be challenging. We investigate the detectability of a subdominant Pop III component in/around massive (M⋆ ≳ 10^9 M⊙) galaxies at z ≈ 6.5–9 from the dustyGadget cosmological simulation suite, and the confusion arising from second-generation (Pop II) stars in their surroundings. We find that young (≲1 Myr), massive (MIII ∼ 6 × 10^5 M⊙) Pop III clusters forming within these galaxy environments are responsible for strong HeII1640 line emission (LHeII1640 ≳ 10^41 erg ^s−1), which would be detectable with ≈10(50) hr of medium-resolution observations with NIRSpec/IFU at z ≈ 6(10). These bright luminosities cannot be produced by standard Pop II populations alone. On the other hand, the dominant Pop II component within massive “hybrid” Pop III hosts powers strong metal line emission (L[OIII]5007 ≳ 10^42 erg s^−1), indicating that the detection of metal lines alone cannot exclude the presence of Pop IIIs in high-z galaxy environments. We further discuss candidate selection strategies based on Lyα, Hα, and Hβ emission, and how spatially resolved observations may enable the detection of isolated, pristine pockets in the outskirts of massive halos.}, author = {Venditti, Alessandra and Graziani, Luca and Schneider, Raffaella and Bromm, Volker and Muñoz, Julian B. and Di Cesare, Claudia and Valiante, Rosa and Calabrò, Antonello and Maiolino, Roberto and Finkelstein, Steven L. and Parente, Massimiliano and Saggini, Matteo and Chisholm, John}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{Catching the nebular needle in a polluted haystack: Line-emission signatures from population III-forming pockets around massive galaxies at the end of reionization}}, doi = {10.3847/1538-4357/ae7b2c}, volume = {1005}, year = {2026}, } @article{22616, abstract = {Accretion disks in active galactic nuclei (AGN) are promising sites for mergers of stellar-mass black holes (BHs) detectable via gravitational waves (GWs). These environments facilitate both in situ formation and dynamical capture of compact objects and their subsequent mergers. The uncertain origin of GW events detected by LIGO, Virgo, and KAGRA motivates searching for accompanying electromagnetic (EM) signatures. Here, we investigate postmerger EM flares associated with jets launched from merger remnants, as well as from the shocked ambient gas as the jet breaks out of the disk. We find that jet breakout produces luminous gamma-ray emission, detectable with MeV-band telescopes. Cooling emission from a shocked circum-BH minidisk, winds, and background AGN disk peaks in the UV and optical, with durations ranging from about an hour to a month, and can be identified through year-long monitoring of ∼103 AGNs with luminosities ranging from ∼1044 to ∼1045 erg s−1. With a single set of parameters, this postmerger jet model produces gamma-ray, hard X-ray, and optical flares similar to those claimed to be associated with GW events. Furthermore, by incorporating a transition from a high- to low-angular-momentum accretion state after the merger, the model avoids excessive BH growth, alleviating tensions with hyper-Eddington accretion scenarios.}, author = {Tagawa, Hiromichi and Haiman, Zoltán and Kimura, Shigeo S. and Yesuf, Hassen M. and Guo, Hengxiao}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{Electromagnetic flares from compact-object mergers in active galactic nucleus disks: Signatures and predictions}}, doi = {10.3847/1538-4357/ae7d29}, volume = {1006}, year = {2026}, } @article{22814, abstract = {We present a study of a pseudo little red dot with no metal lines (Pseudo-LRD-NOM), a highly magnified lowmass galaxy behind the lensing cluster A370 at z = 5.96. We classify this object as a pseudo-LRD because its red rest-frame optical color is contaminated by a prominent Hα line (with EW0 ≳ 800 Å) present in its JWST NIRSpec spectrum. Hα is dominated by a narrow component and also has a minor broad component indicative of an active black hole with MBH ≈ 5.6 × 10^6 M⊙. A narrow Hβ emission line is also detected (where the signal-tonoise ratio, S/N, is 8), producing a Balmer decrement (narrow) Hα/Hβ = 11. The rest-frame UV spectral slope is ßspec/uv = - 1.20 ± 0.28. All these features can be ascribed to high dust attenuation. However, no [O III]λ5007 or any other metal lines are detected in the spectrum, so [O III]5007/Hβ < 0.25, at odds with a simple dust attenuation explanation. Accounting for all the spectral properties requires the model of a starburst with moderate color excess E(B − V )≈0.2–0.5, high gas density (nH ≳ 10^6 cm^−3 ), and low- to extremely-low gas/stellar metallicities (Z = 0.01–0.1 Z⊙). The demagnified stellar mass is × 2.25+ 0 1 . . 8 3 3 0 10^7 M , and the stellar-mass surface density is = + * 418 M pc 310 725 2, similar to that of massive/nuclear star clusters. Pseudo-LRD-NOM provides evidence of massive black-hole growth occurring in a high-density, dusty starburst that is at the early stages of its chemical enrichment, and is likely a precursor to a real LRD.}, author = {Caputi, Karina I. and Cooper, Ryan A. and Rinaldi, Pierluigi and Navarro-Carrera, Rafael and Iani, Edoardo and Tumborang, Abigail A.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{Pseudo Little Red Dot: An active black hole embedded in a dense and dusty, metal-poor starburst galaxy at z = 5.96}}, doi = {10.3847/1538-4357/ae80b9}, volume = {1007}, year = {2026}, } @article{21997, abstract = {The massive binary common envelope (CE) phase plays a pivotal role in the formation of close black hole (BH)/neutron star binaries, yet significant uncertainties remain in our understanding of this process. In this study, we aim to constrain the massive binary CE phase by systematically reconstructing three observed BH X-ray binaries (BHXBs): GRO J1655-40, SAX J1819.3-2525, and 4U 1543-47. Through comprehensive binary evolution simulations and parametric supernova modeling, we establish lower limits for the CE efficiency parameters under different energy considerations within the standard energy formalism. Specifically, we derive minimum values for three cases: α0.5U and αU, representing CE efficiencies with half and all of the internal energy contributing to the envelope ejection, respectively, and αH, accounting for the envelope’s enthalpy. Our analysis reveals that the self-consistent formation of these three BHXBs requires CE efficiency parameters satisfying α0.5U ≳ 6.7, αU ≳ 4.2, and αH ≳ 1.7. Notably, we find no viable solutions with CE efficiency values below unity, even when considering the most extreme scenarios, in which the envelope binding energy is significantly reduced through enthalpy inclusion. Our results strongly imply that either additional energy sources are required or the formalism itself must be revised. Furthermore, we quantitatively assess the impact of BH natal kicks on our results. A key finding is that 4U 1543-47’s formation requires substantial natal kicks (≳50 km s−1), as lower kick velocities are incompatible with isolated binary evolution.}, author = {Li, Zhenwei and Wei, Dandan and Jia, Shi and Chen, Hailiang and Ge, Hongwei and Chen, Zhuo and Zhang, Yangyang and Chen, Xuefei and Han, Zhanwen}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, publisher = {IOP Publishing}, title = {{A path to constraints on common envelope ejection in massive binaries: Full evolutionary reconstruction of three Black Hole X-ray binaries}}, doi = {10.3847/1538-4357/ae66fd}, volume = {1004}, year = {2026}, } @article{22950, abstract = {Little red dots (LRDs) are compact, red sources discovered by JWST at high redshift (z ≳ 4), marked by distinctive “V-shaped” spectral energy distributions (SEDs) and often interpreted as rapidly accreting active galactic nuclei (AGNs). Their true nature remains unclear though, and their evolutionary connection to their lower-redshift counterparts is still poorly constrained. Thus, we present WISEA J123635.56+621424.2 (here dubbed the Saguaro), a z = 2.0145 galaxy in GOODS-North, as a possible analog of high-redshift LRDs and a potential missing link in their evolutionary path toward lower-redshift systems. It features a compact LRD-like nucleus surrounded by a face-on spiral host. Its connections to LRDs include the following: (1) its nuclear spectrum shows a clear “V-shaped” SED, and (2) when redshifted to z = 7, surface brightness dimming makes the host undetectable, thus mimicking an LRD. This suggests that high-redshift LRDs may be embedded in extended hosts. To test this, we stack rest-frame UV images of 99 photometrically selected LRDs, revealing faint, diffuse emission. Stacking in redshift bins reveals mild radial growth, consistent with the expected galaxy size evolution. A simple analytic model confirms that surface brightness dimming alone can explain their compact appearance. Lastly, we show that the Saguaro is not unique by describing similar objects from the literature at z ≲ 3.5. Taken together, our results support a scenario in which LRDs may not be a distinct population, but could be the visible nuclei of galaxies undergoing a short-lived, (perhaps) AGN-dominated evolutionary phase, with their compact, red appearance driven largely by observational biases.}, author = {Rinaldi, Pierluigi and Rieke, George H. and Wu, Zihao and Gilbert, Carys J. E. and Pacucci, Fabio and Barchiesi, Luigi and Alberts, Stacey and Carniani, Stefano and Bunker, Andrew J. and Bhatawdekar, Rachana and D’Eugenio, Francesco and Ji, Zhiyuan and Johnson, Benjamin D. and Hainline, Kevin and Kokorev, Vasily and Kumari, Nimisha and Iani, Edoardo and Lyu, Jianwei and Maiolino, Roberto and Parlanti, Eleonora and Robertson, Brant E. and Sun, Yang and Vignali, Cristian and Williams, Christina C. and Willmer, Christopher N. A. and Zhu, Yongda}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{Beyond the dot: An LRD-like nucleus at the heart of an IR-bright galaxy and its implications for high-redshift LRDs}}, doi = {10.3847/1538-4357/ae80cd}, volume = {1006}, year = {2026}, } @article{22964, abstract = {We investigate whether the nonaccreting phases found in thin, locally isothermal circumbinary disks survive when the disk thermodynamics are evolved self-consistently. We present grid-based hydrodynamics simulations of circumbinary accretion with an energy equation that includes viscous and hydrodynamic heating coupled to radiative blackbody cooling in the high-Mach number regime. We find that, although gas accumulates and heats at the far edge of the circumbinary cavity, the regions that launch accretion streams remain comparatively cold, leading to potentially long-lived suppression of the binary accretion rate as the large-scale feeding rate is reduced towards the Eddington limit. This runaway nonaccretion problem, however, is weakened relative to locally isothermal solutions. Despite their low accretion rates, binaries interacting with disks in a nonaccreting phase can remain sufficiently luminous and variable at optical and near-infrared frequencies to be detectable in upcoming wide-field surveys such as LSST and the Roman Space Telescope. Because of the effective truncation of the surrounding disk, though, such systems are comparatively faint in high energy, photoionizing emission, and may therefore appear as intrinsically X-ray–weak active galactic nuclei with weak or absent emission line features. We additionally suggest an update to grid-based sink prescriptions for approximating mass loss across an unresolved horizon when including an energy conservation equation.}, author = {Tiede, Christopher and O'Neill, David W and D’Orazio, Daniel J.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, publisher = {IOP Publishing}, title = {{Dynamics and detectability of long-lived nonaccretion phases for massive Black Hole binaries in cold thermally regulating disks}}, doi = {10.3847/1538-4357/ae914e}, volume = {1008}, year = {2026}, } @article{23051, abstract = {Most massive stars (∼8–25M⊙) interact with a binary companion during their lifetimes. These interactions can remove the hydrogen-rich envelope, producing intermediate-mass (∼2–8M⊙) and helium-rich stars. These “stripped stars” are predicted to emit predominantly in the ultraviolet (UV) and can therefore be identified via a UV excess—provided they are not outshone by their companion. However, despite their importance to binary evolution, supernovae, and ionizing feedback, few stripped stars have been confirmed. This is likely due to the scarcity of wide-field, high angular-resolution, UV surveys of stellar populations with reliable distances and extinction estimates. To address this, we present the Stripped-Star Ultraviolet Magellanic Clouds Survey catalog. We use the Tractor forward modeling software to perform point-spread function photometry on 2420 Swift UVOT images of the LMC and SMC. The resulting catalog contains 734,862 sources in three UV filters to a depth of ∼20 Vega mag. We perform validation tests on the photometry pipeline and highlight the catalog’s broad applicability. We then identify sources with excess UV light compared to main-sequence stars and apply a series of quality cuts. From this, we identify 522 candidate stripped stars in the LMC and 298 in the SMC. We assess the potential contamination from other UV excess systems and argue the dominant uncertainty to be dust: early main-sequence stars can mimic the colors of stripped-star binaries when extinction is overcorrected. This survey lays the groundwork for the first systematic census of stripped stars and opens new windows into binary evolution and massive star populations.}, author = {Ludwig, B. and Drout, M. R. and Götberg, Ylva Louise Linsdotter and Lang, D. and Laroche, A.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, publisher = {IOP Publishing}, title = {{The Stripped-Star Ultraviolet Magellanic Cloud Survey (SUMS): The ultraviolet photometric catalog and stripped-star candidate selection}}, doi = {10.3847/1538-4357/ae2d13}, volume = {999}, year = {2026}, }