@article{21998,
  abstract     = {Little Red Dots (LRDs), among the most enigmatic high-redshift discoveries by JWST, are commonly believed to be powered by accreting supermassive black holes. Here, we explore the possibility that these sources are globular clusters in formation, with rest-frame UV arising from a very young stellar population and rest-frame optical from a short-lived supermassive (>104 M⊙) star. The spectral profiles of LRDs are broadly consistent with this scenario, though the observed temperatures and bolometric luminosities favor emission reprocessed by optically thick continuum-driven winds not fully captured by current models. The LRD z ∼ 5−7 UV luminosity function naturally evolves, under standard evolutionary and mass-loss prescriptions, into a present-day mass function with a turnover at log10(M*/M⊙) = 5.3 and an exponential cutoff at high masses, consistent with local globular cluster populations. We estimate the total present-day number density of LRDs formed across all redshifts to be ≈0.3 Mpc−3, similar within uncertainties to local globular clusters. The observed LRD redshift range matches the age distribution of metal-poor globular clusters, without current LRD counterparts to the metal-rich population. If LRDs are globular clusters in formation, we predict chemical abundance patterns characteristic of multiple stellar populations, including enhanced He and N, and potential Na–O and Al–Mg anticorrelations. These results offer a local perspective to explore this surprisingly abundant population of distant sources, and a potential new window into extreme stellar astrophysics in the early Universe.},
  author       = {Chisholm, John and Berg, Danielle A. and Boylan-Kolchin, Michael and De Graaff, Anna and Furtak, Lukas J. and Kokorev, Vasily and Matthee, Jorryt J and Muñoz, Julian B. and Naidu, Rohan P. and Sander, Andreas A.C.},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{Little Red Dots as globular clusters in formation}},
  doi          = {10.3847/2041-8213/ae6dae},
  volume       = {1004},
  year         = {2026},
}

@article{21709,
  abstract     = {JWST’s “little red dots” (LRDs) are increasingly interpreted as active galactic nuclei (AGN) obscured by dense thermalized gas rather than dust as evidenced by their X-ray weakness, blackbody-like continua, and Balmer line profiles. Key questions are how LRDs connect to standard UV-luminous AGN, whether transitional phases exist, and whether they are observable. We present the “X-ray dot” (XRD), a compact source at z = 3.28 observed by the NIRSpec Wide Guaranteed Time Observation survey. The XRD exhibits LRD hallmarks: a blackbody-like (Teff ≃ 6400 K) red continuum, a faint but blue rest-UV excess, falling mid-IR emission, and broad Balmer lines (FWHM ∼ 2700–3200 km s−1). Unlike LRDs, however, it is remarkably X-ray luminous (L2−10 keV = 1044.18 erg s−1) and has a continuum inflection that is blueward of the Balmer limit. We find that the red rest-optical and blue mid-IR continuum cannot be reproduced by standard dust-attenuated AGN models without invoking extremely steep extinction curves, nor can the weak mid-IR emission be reconciled with well-established X-ray–torus scaling relations. We therefore consider an alternative scenario: the XRD may be an LRD in transition, where the gas envelope dominates the optical continuum but optically thin sight lines allow X-rays to escape. The XRD may thus provide a physical link between LRDs and standard AGN, offering direct evidence that LRDs are powered by supermassive black holes and providing insight into their accretion properties.},
  author       = {Hviding, Raphael E. and De Graaff, Anna and Liu, Hanpu and Goulding, Andy D. and Ma, Yilun and Greene, Jenny E. and Boogaard, Leindert A. and Bunker, Andrew J. and Cleri, Nikko J. and Franx, Marijn and Hirschmann, Michaela and Leja, Joel and Matthee, Jorryt J and Naidu, Rohan P. and Setton, David J. and Übler, Hannah and Venturi, Giacomo and Wang, Bingjie},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{The X-ray dot: Exotic dust or a late-stage Little Red Dot?}},
  doi          = {10.3847/2041-8213/ae4c88},
  volume       = {1000},
  year         = {2026},
}

@article{21713,
  abstract     = {GW231123 represents the most massive binary–black hole merger detected to date, lying firmly within, or even above, the pair-instability mass gap. The component spins are both exceptionally high (a1 = 0.90 +0.10/-0.19, a2 = 0.80 +0.20/-0.51), which is difficult to explain with repeated mergers. Here we show that the black hole spin vectors are closely aligned with each other while significantly tilted relative to the binary’s orbital angular momentum, pointing to a common accretion-driven origin. We examine astrophysical formation channels capable of producing near-equal, high-mass, and mutually aligned spins consistent with GW231123—particularly binaries embedded in AGN disks and Population III remnants, which grew via coherent misaligned gas accretion. We further argue that other high-mass, high-spin events, e.g., GW190521, may share a similar evolutionary pathway. These findings underscore the critical role of sustained, coherent accretion in shaping the most extreme black hole binaries.},
  author       = {Bartos, Imre and Haiman, Zoltán},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{Accretion is all you need: Black Hole spin alignment in merger GW231123 indicates accretion pathway}},
  doi          = {10.3847/2041-8213/ae2bff},
  volume       = {996},
  year         = {2026},
}

@article{21714,
  abstract     = {Be stars are rapidly rotating main-sequence stars that play a crucial role in understanding stellar evolution and binary interactions. In this Letter, we propose a new formation scenario for black hole (BH) + Be star binaries (hereafter BHBe binaries), where the Be star is produced through the wind Roche lobe overflow (WRLOF) mechanism. Our analysis is based on numerical simulations of the WRLOF process in massive binaries, building on recent theoretical work. We demonstrate that the WRLOF model can efficiently form BHBe binaries under reasonable assumptions on stellar wind velocities. Using rapid binary population synthesis, we estimate the population of such systems in the Milky Way, predicting ∼1800−3200 currently existing BHBe binaries originating from the WRLOF channel. These systems are characterized by high eccentricities and exceptionally wide orbits, with typical orbital periods exceeding 1000 days and a peak distribution around ∼10,000 days. Due to their long orbital separations, these BHBe binaries are promising targets for future detection via astrometric and interferometric observations.},
  author       = {Li, Zhenwei and Jia, Shi and Wei, Dandan and Ge, Hongwei and Chen, Hailiang and Zhang, Yangyang and Chen, Xuefei and Han, Zhanwen},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{Formation of Be stars via wind accretion: Case study on Black Hole + Be star binaries}},
  doi          = {10.3847/2041-8213/ae3008},
  volume       = {996},
  year         = {2026},
}

@article{21846,
  abstract     = {We compile a sample of 83 little red dots (LRDs) with JWST imaging and find that a substantial fraction (∼43%, rising to ≳80% for the most luminous LRDs) host one or more spatially offset, UV-bright companions at projected separations of 0.5 kpc ≲ d ≲ 5 kpc, with median 〈d〉 = 1.0 kpc. This fraction is even higher when smaller spatial scales are probed at high signal-to-noise ratio: the two most strongly lensed LRDs, A383-LRD1 and the newly discovered A68-LRD1, both have UV-bright companions at separations of only d ∼ 0.3 kpc, below the resolution limit of most unlensed JWST samples. We explore whether these ubiquitous red/blue configurations may be physically linked to the formation of LRDs, in analogy with the “synchronized pair” scenario originally proposed for direct-collapse black hole formation. In this picture, UV radiation from the companions, with typically modest stellar masses (M∗ ∼ 108−109 M⊙), suppresses molecular hydrogen cooling in nearby gas, allowing nearly isothermal collapse and the formation of extremely compact objects, such as massive black holes, supermassive stars, or quasi-stars. Using component-resolved photometry and spectral energy distribution modeling, we infer Lyman–Werner radiation fields of J21,LW ∼ 102.5–105 at the locations of the red components, comparable to those required in direct-collapse models, suggesting that the necessary photodissociation conditions are realized in many LRD systems. This framework provides a simple and self-consistent explanation for the extreme compactness and distinctive spectral properties of LRDs and links long-standing theoretical models for early compact object formation directly to a population now observed with JWST in the early Universe.},
  author       = {Baggen, Josephine F.W. and Scoggins, Matthew T. and Van Dokkum, Pieter and Haiman, Zoltán and Torralba Torregrosa, Alberto and Matthee, Jorryt J},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{Connecting the dots: UV-bright companions of Little Red Dots as Lyman–Werner sources enabling direct-collapse Black Hole formation}},
  doi          = {10.3847/2041-8213/ae58a5},
  volume       = {1002},
  year         = {2026},
}

@article{22263,
  abstract     = {Recent studies at high redshift have revealed an enigmatic class of little red dots (LRDs) with extreme Balmer breaks, stronger than in any stellar atmosphere. However, it is unclear whether such objects exist at lower redshift, especially given the low number of LRDs reported at z ≲ 2. Here, we report the discovery of PAN-BH*-1, an LRD with an extreme Balmer break at z = 1.73, identified from JWST/NIRCam pure-parallel imaging taken by the PANORAMIC survey, and confirmed by deep VLT/X-Shooter spectroscopy. The rest-optical to near-infrared spectral energy distribution of PAN-BH*-1 is consistent with a photospheric continuum with effective temperature Teff ≈ 4800 K. The broad Hα emission line shows remarkably deep absorption, stronger than previously measured in any LRD. The absorption trough spans from −520 to +267 km s−1 with respect to the systemic redshift. The presence of blue- and red-shifted absorption suggests complex dynamics of the obscuring gas along the line of sight. We speculate that the absorption trough can be produced by a thick wind launched from a thick, rotating photospheric disk, the latter being the source of the red optical continuum. While the source is unresolved in the rest-optical JWST data (reff < 47 pc), the rest-near-UV Hubble Space Telescope imaging shows an extended morphology with (formular displayed) kpc, which we interpret as a host galaxy with a stellar mass of ∼10^8 M⊙, in line with the narrow Hα emission. The discovery of this object at cosmic noon highlights the feasibility of systematic searches for extreme LRDs with wide-area facilities such as Euclid and Roman.},
  author       = {Torralba Torregrosa, Alberto and Matthee, Jorryt J and Weibel, Andrea and Naidu, Rohan P. and Ma, Yilun and Cloonan, Aidan P. and Desai, Aayush A and De Graaff, Anna and Greene, Jenny E. and Jespersen, Christian Kragh and Kramarenko, Ivan and Mascia, Sara and Oesch, Pascal A. and Sun, Wendy Q. and Williams, Christina C.},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{A black hole star at cosmic noon: Extreme Balmer break, photospheric continuum, and broad absorption by thick winds in a Little Red Dot at z = 1.7}},
  doi          = {10.3847/2041-8213/ae7bfd},
  volume       = {1005},
  year         = {2026},
}

@article{21058,
  abstract     = {Luminous broad Hα emission and red rest-optical spectral energy distributions (SEDs) are the hallmark of compact little red dots (LRDs), implying highly attenuated dusty starbursts and/or obscured active galactic nuclei (AGN). However, the lack of observed far-infrared (FIR) emission has proved difficult to reconcile with the implied attenuated luminosity in these models. Here, we utilize deep new Atacama Large Millimeter/submillimeter Array imaging, new and existing JWST/MIRI imaging, and archival Spitzer/Herschel imaging of two of the rest-optically brightest LRDs (z = 3.1 and z = 4.47) to place the strongest constraints on the IR luminosity in LRDs to date. The detections at λrest = 1–4 μm imply flat slopes in the rest-IR, ruling out a contribution from hot (T ≳ 500 K) dust. Similarly, FIR nondetections rule out any appreciable cold (T ≲ 75 K) dust component. Assuming energy balance, these observations are inconsistent with the typical FIR dust emission of dusty starbursts and quasar tori, which usually show a mixture of cold and hot dust. Additionally, our [C ii] nondetections rule out typical dusty starbursts. We compute empirical maximum IR SEDs and find that both LRDs must have log(LIR/L ) 12.2 at the 3σ level. These limits are in tension with the predictions of rest-optical spectrophotometric fits, be they galaxy-only, AGN-only, or composite. It is unlikely that LRDs are highly dust-reddened intrinsically blue sources with a dust temperature distribution that conspires to avoid current observing facilities. Rather, we favor an intrinsically redder LRD SED model that alleviates the need for strong dust attenuation.},
  author       = {Setton, David J. and Greene, Jenny E. and Spilker, Justin S. and Williams, Christina C. and Labbé, Ivo and Ma, Yilun 逸伦 and Wang, Bingjie 冰洁 and Whitaker, Katherine E. and Leja, Joel and de Graaff, Anna and Alberts, Stacey and Bezanson, Rachel and Boogaard, Leindert A. and Brammer, Gabriel and Cutler, Sam E. and Cleri, Nikko J. and Cooper, Olivia R. and Dayal, Pratika and Fujimoto, Seiji and Furtak, Lukas J. and Goulding, Andy D. and Hirschmann, Michaela and Kokorev, Vasily and Maseda, Michael V. and McConachie, Ian and Matthee, Jorryt J and Miller, Tim B. and Naidu, Rohan P. and Oesch, Pascal A. and Pan, Richard and Price, Sedona H. and Suess, Katherine A. and Weaver, John R. and Xiao, Mengyuan and Zhang, Yunchong and Zitrin, Adi},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  publisher    = {IOP Publishing},
  title        = {{A confirmed deficit of hot and cold dust emission in the most luminous Little Red Dots}},
  doi          = {10.3847/2041-8213/ade78b},
  volume       = {991},
  year         = {2025},
}

@article{21121,
  abstract     = {The relation between the masses of supermassive black holes (SMBHs) and their host galaxies encodes information on their mode of growth, especially at the earliest epochs. The James Webb Space Telescope (JWST) has opened such investigations by detecting the host galaxies of active galactic nuclei (AGN) and more luminous quasars within the first billion years of the Universe (z ≳ 6). Here, we evaluate the relation between the mass of SMBHs and the total stellar mass of their host galaxies using a sample of nine quasars at 6.18 ≤ z ≤ 6.4 from the Subaru High-z Exploration of Low-luminosity Quasars survey with NIRCam and NIRSpec observations. We find that the observed location of these quasars in the SMBH–galaxy mass plane (logMBH/M 8–9; logM*/M 9.5–11) is consistent with a nonevolving intrinsic mass relation with dispersion (0.80 +0.23 -0.28 dex) higher than the local value (∼0.3–0.4 dex) of their more massive descendants. Our analysis is based on a forward model of systematics and includes a consideration of the impact of selection effects and measurement uncertainties with an assumption on the slope of the mass relation. While degeneracies between parameters persist, the best-fit solution has a reasonable AGN fraction (2.3%) of galaxies at z ∼ 6 with an actively growing UV-unobscured black hole. In particular, models with a substantially higher normalisation in MBH would require an unrealistically low intrinsic dispersion (∼0.22 dex). Consequently, our results predict a large population of AGN at lower black hole masses, as are now just starting to be discovered in focused efforts with JWST.},
  author       = {Silverman, John David and Li, Junyao and Ding, Xuheng and Onoue, Masafusa and Strauss, Michael A. and Matsuoka, Yoshiki and Izumi, Takuma and Jahnke, Knud and Treu, Tommaso and Volonteri, Marta and Phillips, Camryn L. and Andika, Irham T. and Aoki, Kentaro and Arita, Junya and Baba, Shunsuke and Bosman, Sarah E. I. and Eilers, Anna-Christina and Fan, Xiaohui and Fujimoto, Seiji and Habouzit, Melanie and Haiman, Zoltán and Imanishi, Masatoshi and Inayoshi, Kohei and Iwasawa, Kazushi and Kashikawa, Nobunari and Kawaguchi, Toshihiro and Lee, Chien-Hsiu and Lupi, Alessandro and Nagao, Tohru and Schindler, Jan-Torge and Schramm, Malte and Shimasaku, Kazuhiro and Toba, Yoshiki and Trakhtenbrot, Benny and Umehata, Hideki and Vestergaard, Marianne and Walter, Fabian and Wang, Feige and Yang, Jinyi},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{SHELLQs–JWST perspective on the intrinsic mass relation between supermassive black holes and their host galaxies at z > 6}},
  doi          = {10.3847/2041-8213/ae279c},
  volume       = {995},
  year         = {2025},
}

@article{21317,
  abstract     = {Accreting white dwarfs (WDs) in close binary systems, commonly known as cataclysmic variables (CVs), with orbital periods below the canonical period minimum (≈80 minutes) are rare. Such short periods can only be reached if the donor star in the CV is either significantly evolved before initiating mass transfer to the WD or is metal-poor. We present optical photometry and spectroscopy of Gaia19bxc, a high-amplitude variable identified as a polar CV with an exceptionally short orbital period of 64.42 minutes—well below the canonical CV period minimum. High-speed photometry confirms persistent double-peaked variability consistent with cyclotron beaming, thus indicating the presence of a magnetic WD. Phase-resolved Keck/Low-Resolution Imaging Spectrometer (LRIS) spectroscopy reveals strong hydrogen and helium emission lines but no donor features, indicating the accretor is a magnetic WD and the donor is hydrogen-rich, but cold and faint. The absence of a detectable donor and the low inferred temperature (≲3500 K) disfavor an evolved donor scenario. Instead, the short period and the system’s halo-like kinematics suggest Gaia19bxc may be the first known metal-poor polar. Because metal-poor donors are more compact than solar-metallicity donors of the same mass, they can reach shorter minimum periods. Gaia19bxc is one of only a handful of known metal-poor CVs below the canonical period minimum and has the shortest period of any such magnetic system discovered to date.},
  author       = {Galiullin, Ilkham and Rodriguez, Antonio C. and El-Badry, Kareem and Caiazzo, Ilaria and Szkody, Paula and Nagarajan, Pranav and Whitebook, Samuel},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{Optical spectroscopy of the most compact accreting binary harboring a magnetic White Dwarf and a hydrogen-rich donor}},
  doi          = {10.3847/2041-8213/adff82},
  volume       = {990},
  year         = {2025},
}

@article{19638,
  abstract     = {The James Webb Space Telescope has revealed low-luminosity active galactic nuclei at redshifts of z ≳ 4–7, many of which host accreting massive black holes (BHs) with BH-to-galaxy mass (MBH/M⋆) ratios exceeding the local values by more than an order of magnitude. The origin of these overmassive BHs remains unclear but requires potential contributions from heavy seeds and/or episodes of super-Eddington accretion. We present a growth model coupled with dark matter halo assembly to explore the evolution of the MBH/M⋆ ratio under different seeding and feedback scenarios. Given the gas inflow rates in protogalaxies, BHs grow episodically at moderate super-Eddington rates, and the mass ratio increases early on, despite significant mass loss through feedback. Regardless of seeding mechanisms, the mass ratio converges to a universal value ∼0.1–0.3, set by the balance between gas feeding and star formation efficiency in the nucleus. This behavior defines an attractor in the MBH–M⋆ diagram, where overmassive BHs grow more slowly than their hosts, while undermassive seeds experience rapid growth before aligning with the attractor. We derive an analytical expression for the universal mass ratio, linking it to feedback strength and halo growth. The convergence of evolutionary tracks erases seeding information from the mass ratio by z ∼ 4–6. Detecting BHs with ∼105−6 M⊙ at higher redshifts that deviate from the convergence trend would provide key diagnostics of their birth conditions.},
  author       = {Hu, Haojie and Inayoshi, Kohei and Haiman, Zoltán and Ho, Luis C. and Ohsuga, Ken},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{The convergence of heavy and light seeds to overmassive black holes at cosmic dawn}},
  doi          = {10.3847/2041-8213/adc680},
  volume       = {983},
  year         = {2025},
}

@article{20030,
  abstract     = {We report the discovery of a Lyα emitter (LAE) candidate in the immediate foreground of the quasar PSO J158-14 at zQSO = 6.0685 at a projected distance ∼29 pkpc that is associated with an extremely metal-poor absorption system. This system was found in archival observations of the quasar field with the Very Large Telescope (VLT)/Multi-Unit Spectroscopic Explorer (MUSE) and was previously missed in searches of absorption systems using quasar absorption line spectroscopy, as it imparts no detectable metal absorption lines on the background quasar spectrum. The detected Lyα emission line at a redshift of zLAE = 6.0323 is well aligned with the outer edge of the quasar’s proximity zone and can plausibly cause its observed damping wing if it is associated with a proximate subdamped Lyα absorption system with a column density of log Nhi/cm^-2 19.7. A >10 hr medium-resolution spectrum of the quasar observed with the Magellan/Folded-port InfraRed Echellette (FIRE) and VLT/X-Shooter spectrographs reveals a metallicity constraint of [Z/H] < −3. Such low metallicity makes this system an extremely metal-poor galaxy candidate and provides an exciting site to study possible signatures of Population III stars.},
  author       = {Ďurovčíková, Dominika and Eilers, Anna Christina and Simcoe, Robert A. and Welsh, Louise and Meyer, Romain A. and Matthee, Jorryt J and Ryan-Weber, Emma V. and Yue, Minghao and Katz, Harley and Satyavolu, Sindhu and Becker, George and Davies, Frederick B. and Farina, Emanuele Paolo},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{An extremely metal-poor Lyα emitter candidate at z = 6 revealed through absorption spectroscopy}},
  doi          = {10.3847/2041-8213/ade71c},
  volume       = {987},
  year         = {2025},
}

@article{20425,
  abstract     = {Ultraviolet (UV) radiation from accreting black holes ionizes the intergalactic gas around early quasars, carving out highly ionized bubbles in their surroundings. Any changes in a quasar’s luminosity are therefore predicted to produce outward-propagating ionization gradients, affecting the Lyα absorption opacity near the quasar’s systemic redshift. This “proximity effect” is well-documented in rest-UV quasar spectra but only provides a one-dimensional probe along our line of sight. Here we present deep spectroscopic observations with the James Webb Space Telescope (JWST) of galaxies in the background of a superluminous quasar at zQSO ≈ 6.3, which reveal the quasar’s “light echo” with Lyα tomography in the transverse direction. This transverse proximity effect is detected for the first time toward multiple galaxy sightlines, allowing us to map the extent and geometry of the quasar’s ionization cone. We obtain constraints on the orientation and inclination of the cone, as well as an upper limit on the obscured solid angle fraction of fobsc < 91%. Additionally, we find a timescale of the quasar’s UV radiation of tqso = 10^5.6+0.1-0.3 yr, which is significantly shorter than would be required to build up the central supermassive black hole (SMBH) with conventional growth models, but is consistent with independent measurements of the quasars’ duty cycle. Our inferred obscured fraction disfavors a scenario where short quasar lifetimes can be explained exclusively by geometric obscuration, and instead supports the idea that radiatively inefficient accretion or growth in initially heavily enshrouded cocoons plays a pivotal role in early SMBH growth. Our results pave the way for novel studies of quasars’ ionizing geometries and radiative histories at early cosmic times.},
  author       = {Eilers, Anna Christina and Yue, Minghao and Matthee, Jorryt J and Hennawi, Joseph F. and Davies, Frederick B. and Simcoe, Robert A. and Teague, Richard and Bordoloi, Rongmon and Brammer, Gabriel and Kang, Yi and Kashino, Daichi and Mackenzie, Ruari and Naidu, Rohan P. and Navarrete, Benjamín},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{The light echo of a high-redshift quasar mapped with Lyα tomography}},
  doi          = {10.3847/2041-8213/ae057a},
  volume       = {991},
  year         = {2025},
}

@article{20493,
  abstract     = {We propose a formation pathway linking black holes (BHs) observed in gravitational-wave (GW) mergers, wide BH–stellar systems uncovered by Gaia, and accreting low-mass X-ray binaries (LMXBs). In this scenario, a stellar-mass BH binary undergoes isolated binary evolution and merges while hosting a distant, dynamically unimportant tertiary stellar companion. The tertiary becomes relevant only after the merger, when the remnant BH receives a GW recoil kick. Depending on the kick velocity and system configuration, the outcome can be: (1) a bright electromagnetic (EM) counterpart to the GW merger; (2) an LMXB; (3) a wide BH–stellar companion system resembling the Gaia BH population; or (4) an unbound isolated BH. Modeling the three-body dynamics, we find that ∼0.02% of LIGO–Virgo–KAGRA (LVK) mergers may be followed by an EM counterpart within ∼10 days, produced by tidal disruption of the star by the BH. The flare is likely brightest in the optical–UV and lasts for days to weeks; in some cases, partial disruption causes recurring flares with a period of ∼2 months. We further estimate that this channel can produce ∼1%–10% of Gaia BH systems in the Milky Way. This scenario provides the first physically motivated link between GW sources, Gaia BHs, and some X-ray binaries, and predicts a rare but robust pathway for EM counterparts to binary BH mergers, potentially detectable in LVK’s O5 run.},
  author       = {Naoz, Smadar and Haiman, Zoltán and Quataert, Eliot and Holzknecht, Liz},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{Triples as links between binary Black Hole mergers, their electromagnetic counterparts, and galactic Black Holes}},
  doi          = {10.3847/2041-8213/ae0a20},
  volume       = {992},
  year         = {2025},
}

@article{20649,
  abstract     = {Ionized proximity zones around luminous quasars provide a unique laboratory to characterize the Lyα emission lines from z > 6 galaxies without significant attenuation from the intergalactic medium (IGM). However, Lyα line measurements for galaxies within high-redshift quasars’ proximity zones have been rare so far. Here we present deep spectroscopic observations obtained with the NIRSpec/Micro-Shutter Assembly (MSA) instrument on the James Webb Space Telescope of galaxies in two z > 6 quasar fields. We measure the Lyα line fluxes for 50 galaxies at 6 < z < 7 with UV absolute magnitude M UV < −19 (median M UV = −19.97), among which 15 are located near the luminous quasars, i.e., within Δv < 2500 km s−1. We find that galaxies near the quasars show significant flux blueward of the systemic Lyα wavelength, and have higher Lyα equivalent width compared to galaxies at similar redshifts that are not located within the quasars’ environment. Our result indicates little or no redshift evolution for the Lyα emitter fraction from z ∼ 6.4 to z ∼ 5. Leveraging the low IGM opacity in the quasars’ vicinity, we evaluate the Lyα escape fraction (f esc Ly α) of high-redshift galaxies. Our analysis suggests that galaxies at 〈z〉 ≈ 6.4 have an average f esc Ly α = 0.14 ± 0.04. This value is consistent with reionization models where the Lyman continuum escape fraction is low ( fescLyC ≲ 0.1 ) for luminous galaxies, and where the most luminous galaxies have only a minor contribution to the total ionizing photon budget. © 2025. The Author(s). Published by the American Astronomical Society.},
  author       = {Yue, Minghao and Eilers, Anna Christina and Matthee, Jorryt J and Naidu, Rohan P. and Bordoloi, Rongmon and Davies, Frederick B. and Hennawi, Joseph F. and Kashino, Daichi and Mackenzie, Ruari and Simcoe, Robert A.},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{Escape fractions from unattenuated Lyα emitters around luminous z > 6 quasars}},
  doi          = {10.3847/2041-8213/ae0e0e},
  volume       = {993},
  year         = {2025},
}

@article{18760,
  abstract     = {With the remarkable sensitivity and resolution of JWST in the infrared, measuring rest-optical kinematics of galaxies at z > 5 has become possible for the first time. This study pilots a new method for measuring galaxy dynamics for highly multiplexed, unbiased samples by combining FRESCO NIRCam grism spectroscopy and JADES medium-band imaging. Here we present one of the first JWST kinematic measurements for a galaxy at z > 5. We find a significant velocity gradient, which, if interpreted as rotation, yields Vrot = 305 ± 70 km s−1, and we hence refer to this galaxy as Twister-z5. With a rest-frame optical effective radius of re = 2.25 kpc, the high rotation velocity in this galaxy is not due to a compact size, as may be expected in the early Universe, but rather to a high total mass, (math formula). This is a factor of roughly 10× higher than the stellar mass within re. We also observe that the radial Hα equivalent width profile and the specific star formation rate map from resolved stellar population modeling are centrally depressed by a factor of ∼1.5 from the center to re. Combined with the morphology of the line-emitting gas in comparison to the continuum, this centrally suppressed star formation is consistent with a star-forming disk surrounding a bulge growing inside out. While large, rapidly rotating disks are common to z ∼ 2, the existence of one after only 1 Gyr of cosmic time, shown for the first time in ionized gas, adds to the growing evidence that some galaxies matured earlier than expected in the history of the Universe.},
  author       = {Nelson, Erica and Brammer, Gabriel and Giménez-Arteaga, Clara and Oesch, Pascal A. and Naidu, Rohan P. and Übler, Hannah and Matharu, Jasleen and Shapley, Alice E. and Whitaker, Katherine E. and Wisnioski, Emily and Förster Schreiber, Natascha M. and Smit, Renske and Van Dokkum, Pieter and Chisholm, John and Endsley, Ryan and Hartley, Abigail I. and Gibson, Justus and Giovinazzo, Emma and Illingworth, Garth and Labbe, Ivo and Maseda, Michael V. and Matthee, Jorryt J and Covelo Paz, Alba and Price, Sedona H. and Reddy, Naveen A. and Shivaei, Irene and Weibel, Andrea and Wuyts, Stijn and Xiao, Mengyuan and Alberts, Stacey and Baker, William M. and Bunker, Andrew J. and Cameron, Alex J. and Charlot, Stephane and Eisenstein, Daniel J. and De Graaff, Anna and Ji, Zhiyuan and Johnson, Benjamin D. and Jones, Gareth C. and Maiolino, Roberto and Robertson, Brant and Sandles, Lester and Suess, Katherine A. and Tacchella, Sandro and Williams, Christina C. and Witstok, Joris},
  issn         = {2041-8213},
  journal      = {Astrophysical Journal Letters},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{Ionized gas kinematics with FRESCO: An extended, massive, rapidly rotating galaxy at z = 5.4}},
  doi          = {10.3847/2041-8213/ad7b17},
  volume       = {976},
  year         = {2024},
}

@article{17234,
  abstract     = {The identification of red, apparently massive galaxies at z > 7 in early James Webb Space Telescope (JWST) photometry suggests a strongly accelerated time line compared to standard models of galaxy growth. A major uncertainty in the interpretation is whether the red colors are caused by evolved stellar populations, dust, or other effects such as emission lines or active galactic nuclei (AGNs). Here we show that three of the massive galaxy candidates at z = 6.7–8.4 have prominent Balmer breaks in JWST/NIRSpec spectroscopy from the RUBIES program. The Balmer breaks demonstrate unambiguously that stellar emission dominates at λrest = 0.4 μm and require formation histories extending hundreds of millions of years into the past in galaxies only 600–800 Myr after the big bang. Two of the three galaxies also show broad Balmer lines, with Hβ FWHM > 2500 km s−1, suggesting that dust-reddened AGNs contribute to, or even dominate, the spectral energy distributions of these galaxies at λrest ≳ 0.6 μm. All three galaxies have relatively narrow [O iii] lines, seemingly ruling out a high-mass interpretation if the lines arise in dynamically relaxed, inclined disks. Yet the inferred masses also remain highly uncertain. We model the high-quality spectra using Prospector to decompose the continuum into stellar and AGN components and explore limiting cases in stellar/AGN contribution. This produces a wide range of possible stellar masses, spanning M⋆ ∼ 109−1011M⊙. Nevertheless, all fits suggest a very early and rapid formation, most of which follow with a truncation in star formation. Potential origins and evolutionary tracks for these objects are discussed, from the cores of massive galaxies to low-mass galaxies with overmassive black holes. Intriguingly, we find all of these explanations to be incomplete; deeper and redder data are needed to understand the physics of these systems.},
  author       = {Wang, Bingjie and Leja, Joel and De Graaff, Anna and Brammer, Gabriel B. and Weibel, Andrea and Van Dokkum, Pieter and Baggen, Josephine F.W. and Suess, Katherine A. and Greene, Jenny E. and Bezanson, Rachel and Cleri, Nikko J. and Hirschmann, Michaela and Labbé, Ivo and Matthee, Jorryt J and Mcconachie, Ian and Naidu, Rohan P. and Nelson, Erica and Oesch, Pascal A. and Setton, David J. and Williams, Christina C.},
  issn         = {2041-8213},
  journal      = {Astrophysical Journal Letters},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{RUBIES: Evolved stellar populations with extended formation histories at z ∼ 7-8 in candidate massive galaxies identified with JWST/NIRSpec}},
  doi          = {10.3847/2041-8213/ad55f7},
  volume       = {969},
  year         = {2024},
}

@article{18111,
  abstract     = {Observations of tidal disruption events (TDEs) show signs of nitrogen enrichment reminiscent of other astrophysical sources such as active galactic nuclei and star-forming galaxies. Given that TDEs probe the gas from a single star, it is possible to test whether the observed enrichment is consistent with expectations from the CNO cycle by looking at the observed nitrogen/carbon (N/C) abundance ratios. Given that ≈20% of solar-mass stars (and an even larger fraction of more massive stars) live in close binaries, it is worthwhile to also consider what TDEs from stars influenced by binary evolution would look like. We show here that TDEs from stars stripped of their hydrogen-rich (and nitrogen-poor) envelopes through previous binary-induced mass loss can produce much higher observable N/C enhancements than even TDEs from massive stars. Additionally, we predict that the time dependence of the N/C abundance ratio in the mass fallback rate of stripped stars will follow the inverse behavior of main-sequence stars, enabling a more accurate characterization of the disrupted star.},
  author       = {Mockler, Brenna and Gallegos-Garcia, Monica and Götberg, Ylva Louise Linsdotter and Miller, Jon M. and Ramirez-Ruiz, Enrico},
  issn         = {2041-8213},
  journal      = {Astrophysical Journal Letters},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{Tidal disruption events from stripped stars}},
  doi          = {10.3847/2041-8213/ad6c34},
  volume       = {973},
  year         = {2024},
}

@article{18306,
  abstract     = {Neutral sodium (Na i) is an alkali metal with a favorable absorption cross section such that tenuous gases are easily illuminated at select transiting exoplanet systems. We examine both the time-averaged and time-series alkali spectral flux individually, over 4 nights at a hot Saturn system on a ∼2.8 day orbit about a Sun-like star WASP-49 A. Very Large Telescope/ESPRESSO observations are analyzed, providing new constraints. We recover the previously confirmed residual sodium flux uniquely when averaged, whereas night-to-night Na i varies by more than an order of magnitude. On HARPS/3.6 m Epoch II, we report a Doppler redshift at vΓ,NaD = + 9.7 ± 1.6 km s−1 with respect to the planet's rest frame. Upon examining the lightcurves, we confirm night-to-night variability, on the order of ∼1%–4% in NaD, rarely coinciding with exoplanet transit, not readily explained by stellar activity, starspots, tellurics, or the interstellar medium. Coincident with the ∼+10 km s−1 Doppler redshift, we detect a transient sodium absorption event dFNaD/F⋆ = 3.6% ± 1% at a relative difference of ΔFNaD(t) ∼ 4.4% ± 1%, lasting ΔtNaD ≳ 40 minutes. Since exoplanetary alkali signatures are blueshifted due to the natural vector of radiation pressure, estimated here at roughly ∼−5.7 km s−1, the radial velocity is rather at +15.4 km s−1, far larger than any known exoplanet system. Given that the redshift magnitude vΓ is in between the Roche limit and dynamically stable satellite orbits, the transient sodium may be a putative indication of a natural satellite orbiting WASP-49 A b.},
  author       = {Oza, Apurva V. and Seidel, Julia V. and Hoeijmakers, H. Jens and Unni, Athira and Kesseli, Aurora Y. and Schmidt, Carl A. and Sivarani, Thirupathi and Bello-Arufe, Aaron and Gebek, Andrea and Meyer Zu Westram, Moritz and Sousa, Sérgio G. and Lopes, Rosaly M.C. and Hu, Renyu and De Kleer, Katherine and Fisher, Chloe and Charnoz, Sébastien and Baker, Ashley D. and Halverson, Samuel P. and Schneider, Nick M. and Psaridi, Angelica and Wyttenbach, Aurélien and Torres Rodriguez, Santiago and Bhatnagar, Ishita and Johnson, Robert E.},
  issn         = {2041-8213},
  journal      = {Astrophysical Journal Letters},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{Redshifted sodium transient near exoplanet transit}},
  doi          = {10.3847/2041-8213/ad6b29},
  volume       = {973},
  year         = {2024},
}

@article{18564,
  abstract     = {The recently discovered Pa 30 nebula, the putative type Iax supernova remnant associated with the historical supernova of 1181 AD, shows puzzling characteristics that make it unique among known supernova remnants. In particular, Pa 30 exhibits a complex morphology, with a unique radial and filamentary structure, and it hosts a hot stellar remnant at its center, which displays oxygen-dominated, ultrafast winds. Because of the surviving stellar remnant and the lack of hydrogen and helium in its filaments, it has been suggested that Pa 30 is the product of a failed thermonuclear explosion in a near- or super-Chandrasekhar white dwarf, which created a subluminous transient, a rare subtype of the Ia class of supernovae called type Iax. We present here a detailed study of the 3D structure and velocities of a full radial section of the remnant. The Integral Field Unit observations, obtained with the new red channel of the Keck Cosmic Web Imager spectrograph, reveal that the ejecta are consistent with being ballistic, with velocities close to the free-expansion velocity. Additionally, we detect a large cavity inside the supernova remnant and a sharp inner edge to the filamentary structure, which coincides with the outer edge of a bright ring detected in infrared images. Finally, we detect a strong asymmetry in the amount of ejecta along the line of sight, which might hint at an asymmetric explosion. Our analysis provides strong confirmation that the explosion originated from SN 1181.},
  author       = {Cunningham, Tim and Caiazzo, Ilaria and Prusinski, Nikolaus Z. and Fuller, James and Raymond, John C. and Kulkarni, S. R. and Neill, James D. and Duffell, Paul and Martin, Chris and Toloza, Odette and Charbonneau, David and Kenyon, Scott J. and Lin, Zeren and Matuszewski, Mateusz and McGurk, Rosalie and Polin, Abigail and Yao, Philippe Z.},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{Expansion properties of the young supernova type Iax remnant Pa 30 revealed}},
  doi          = {10.3847/2041-8213/ad713b},
  volume       = {975},
  year         = {2024},
}

@article{15192,
  abstract     = {We searched the Gaia DR3 database for ultramassive white dwarfs with kinematics consistent with having escaped the nearby Hyades open cluster, identifying three such candidates. Two of these candidates have masses estimated from Gaia photometry of approximately 1.1 solar masses; their status as products of single-stellar evolution that have escaped the cluster was deemed too questionable for immediate follow-up analysis. The remaining candidate has an expected mass >1.3 solar masses, significantly reducing the probability of it being an interloper. Analysis of follow-up Gemini GMOS spectroscopy for this source reveals a nonmagnetized hydrogen atmosphere white dwarf with a mass and age consistent with having formed from a single star. Assuming a single-stellar-evolution formation channel, we estimate a 97.8% chance that the candidate is a true escapee from the Hyades. With a determined mass of 1.317 solar masses, this is potentially the most massive known single-evolution white dwarf and is by far the most massive with a strong association with an open cluster.},
  author       = {Miller, David R. and Caiazzo, Ilaria and Heyl, Jeremy and Richer, Harvey B. and El-Badry, Kareem and Rodriguez, Antonio C. and Vanderbosch, Zachary P. and van Roestel, Jan},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {2},
  publisher    = {American Astronomical Society},
  title        = {{An extremely massive white dwarf escaped from the Hyades star cluster}},
  doi          = {10.3847/2041-8213/acffc4},
  volume       = {956},
  year         = {2023},
}