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Physics Astrophysics

astro-ph Watch Astrophysics

Thursday 16 July

Astrophysics of Galaxies

A JWST, ALMA and VLA survey of the Ophiuchus-A star-forming region: Unveiling hidden dust mass and connecting infrared outflows to their radio origins

Isaac C. Radley, John D. Ilee, Gemma Busquet et al. (+18 more)

We present an infrared, millimetre, and radio survey of 20 Class 0-III young stellar objects in the Ophiuchus A L1688 star-forming cluster, combining high-resolution (7-25 au) VLA and JWST observations with archival ALMA data. We implement physically motivated models to derive dust and ionised gas properties, spectral behaviour and their relative contributions through the millimetre-centimetre radio spectral energy distribution. Our models reveal circumstellar dust disks that are, on average, tens to hundreds of times more massive than millimetre-only estimates (subject to uncertainties arising from the choice of dust opacity) and contain millimetre-sized grains even at the Class 0 stage. Owing to the VLA's high resolution we are able to connect outflows to their origins, detecting protostellar jet emission on scales of 10s-1000s au. Our results represent a homogeneous characterisation of the dust and ionised gas properties in Ophiuchus and present a potential solution to the long-standing 'missing disk mass' problem. However, our understanding is still limited by resolution and sensitivity at frequencies <40 GHz. Future facilities like the SKA and ngVLA are needed to provide the necessary capabilities to fully spatially resolve this emission (<0.18") even in one of the closest star-forming regions.
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All authors Isaac C. Radley, John D. Ilee, Gemma Busquet, Hauyu Baobab Liu, Klaus M. Pontoppidan, Alvaro Ribas, Marc Audard, Eleonora Bianchi, Tyler L. Bourke, Claudio Codella, Audrey Coutens, Josep M. Girart, Melvin G. Hoare, Izaskun Jiménez-Serra, Doug Johnstone, Laurent Loinard, Olja Panić, Jaime E. Pineda, Linda Podio, John J. Tobin, David J. Wilner

High Energy Astrophysical Phenomena

Implications of the UV/optical Plateau of AT2018cow

Wenbin Lu and Anthony L. Piro

AT2018cow, the prototypical luminous fast blue optical transient (LFBOT), shows a slowly fading plateau in the UV/optical light lasting at least 5 years after the explosion. The plateau SED is blackbody-like with temperature $\gtrsim$ 2e4 K and an emission radius ~40 Rsun, which has been attributed to a geometrically thin accretion disk around a compact object. Viscously powered disk models, however, require an unusually massive black hole $\gtrsim$ 200 Msun (for viscosity parameter $\alpha$ > 0.01). Moreover, accretion onto such a massive black hole produces X-ray emission that is likely in tension with the XMM-Newton constraint, unless the X-ray is highly anisotropic or absorbed. We propose instead that the UV/optical emission arises from the photosphere of a super-Eddington wind launched from the inner disk, together with irradiation and reprocessing by the geometrically thin outer disk. Fitting the model to four-band HST photometry at t ~ 4 yr, we find that all accretors from 1.4 Msun neutron star to ~100 Msun black hole produce similarly good fits. This degeneracy arises because the wind photospheric color temperature depends only weakly on the accretor mass. We also find that, at NIR-MIR wavelengths (1 to 10 um), wind free-free emission differs by an order of magnitude across the allowed mass range, providing a potential discriminant accessible to JWST. Another potential signature to differentiate the accretor mass and disk composition is the recombination line emission (HeII1640 or H$\alpha$) from the disk wind. The inferred disk parameters from our model are consistent with a micro-tidal disruption event, either tidal disruption or merger with a companion star, in which an initially geometrically thick disk transitions to a thin phase within the first year and subsequently the thin outer disk evolves on the observed ~10 yr viscous timescale.
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High Energy Astrophysical Phenomena

Assessing the waveform systematics from parameter estimation to population inference with eccentricity

Muhammad Zeeshan, Richard O'Shaughnessy, Natalie Malagon et al. (+1 more)

While masses and spins are routinely used to constrain compact binary formation channels, eccentricity provides an additional and potentially powerful diagnostic of binary origin, particularly for dynamically assembled systems. Recent advances in eccentric waveform modeling now make it possible to search for eccentric signatures in gravitational wave data; however, differences between waveform models can introduce systematic effects that may propagate into astrophysical population inference. In this work, we analyze 153 binary black holes, 2 binary neutron stars and 7 neutron star black hole binaries from the GWTC-4 catalog. We compare the source and population level inferences obtained with two eccentric waveform models, SEOBNRv5EHM and TEOBResumS-DALI, as well as with quasi circular waveform analyses. We find that the two eccentric models give broadly consistent source parameter estimates for most events, but some events exhibit subtle and coherent differences. These small, systematic offsets can accumulate in hierarchical population inference, leading to differences in inferred population properties, most notably in the redshift evolution and effective spin distribution. Because coherent event level biases can grow approximately as $\sqrt{N}$ for a catalog of N events, waveform systematics become increasingly important as gravitational wave catalogs expand. We also introduce a synthetic data framework that generates eccentric populations and corresponding RIFT posterior samples, enabling injection studies that test the recoverability of eccentric population properties.
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All authors Muhammad Zeeshan, Richard O'Shaughnessy, Natalie Malagon, Katelyn J. Wagner

High Energy Astrophysical Phenomena

Triple radio flares from tidal disruption events: jet-wind collisions and the discovery of a third radio flare from AT2020vwl

Andrew Mummery, Adelle Goodwin, Colin Christy et al. (+2 more)

Radio flares from tidal disruption events (TDEs) are observed on two distinct timescales: prompt (around the time of optical peak) and delayed (hundreds to thousands of days after optical peak). A recent framework put forward to explain this diversity suggests that super-Eddington winds produce prompt flares while jets launched during a disk state transition at low accretion rates produce delayed flares. A unique observational prediction of this framework is that individual sources showing both types of flares may be expected to show a third flare. This third flare will occur when the (faster) jet catches up with the (slower) wind. The observational appearance of the third flare depends on the system parameters. As the two shock fronts collide the (brighter) jet encounters a change in density, modifying its synchrotron-self-absorption frequency and observed flux. Here we discuss the observational appearance of such a scenario, and then show, in new long-term monitoring radio observations of the TDE AT2020vwl, the discovery of a third radio flare. This flare is coincident with the time at which forward modeling of the first two flares in a wind-jet framework predicts a collision between the two shock fronts. We make predictions for the long-term radio evolution of two other TDEs showing double radio flares: ASASSN-15oi (which may show a weak flare or flattening of the lightcurve) and AT2024tvd (which is predicted to imminently undergo a third flare).
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All authors Andrew Mummery, Adelle Goodwin, Colin Christy, Kate Alexander, Noah Franz

Cosmology and Nongalactic Astrophysics

Two-component large-scale radio emission in Abell 2244

M. Cianfaglione, F. De Gasperin, V. Cuciti et al. (+9 more)

Context. In recent years, clusters have been observed that host multi-component haloes, both in non-merging and merging systems. The existence of these multi-component haloes suggests that there is no clear distinction between the single components. Aims. Abell 2244 is an intermediate-mass cluster that hosts a double component diffuse radio emission. The aim of this paper is to carry out a in-depth study of the diffuse radio emission to constrain its origin and characterize its main radio properties. Methods. In this work we present LOFAR HBA, MeerKAT UHF, and L-band observations of the cluster Abell 2244. We investigated the nature of the diffuse radio emission, combining high sensitivity radio data with XMM-Newton deep X-ray observations. We also used mock LOFAR observations to investigate contamination of the emission from faint radio sources. Results. We find an integrated spectral index of $\alpha^{1279}_{144} = 0.9 \pm 0.1$ for both components, where only the radio halo shows spectral steepening at higher frequencies. These values are comparable with the spectral indices observed in disturbed massive clusters. The outer component does not follow the same radio X-ray correlation as the radio halo, which suggests a different physical origin. Conclusions. By analysing the physical and morphological properties of the diffuse emission, we find that the characteristics of the outer component of the emission are intermediate between those of radio haloes and of known megahaloes. Hence, we speculate that the source is either a morphologically disturbed radio halo, caused by a minor merger interaction, or a megahalo but we cannot reach a final classification. From the mock observations, we find that it is unlikely that the emission is caused by faint sources at low resolutions.
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All authors M. Cianfaglione, F. De Gasperin, V. Cuciti, M. Balboni, R. J. van Weeren, C. Groeneveld, J. M. Boxelaar, M. Della Chiesa, A. Bonafede, G. Di Gennaro, F. Gastaldello, G. Brunetti

High Energy Astrophysical Phenomena

A Multiwavelength Study of a Long-Duration VHE Flare from BL Lacertae with VERITAS

Atreya Acharyya, Avery Archer, Priyadarshini Bangale et al. (+72 more)

We report the first observations of a long-duration very-high-energy (VHE; $E > 100$ GeV) flare from BL Lacertae (VER J2202+422), taken with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). On October 15, 2022, the Fermi-Large Area Telescope (LAT) detected elevated GeV activity originating from this blazar. This triggered a multiwavelength campaign, which includes observations from VERITAS, Swift, NuSTAR, and select optical and radio observatories. VERITAS observed the source for a total of $\sim 9.8$ hours between September 1, 2022 and December 1, 2022. An analysis of these data yields a $\sim 28 \sigma$ detection of the source. While previously observed VHE flares from BL Lacertae have lasted on time-scales of minutes to days, VERITAS continued to detect flaring activity from the source for over a month ($\sim 40$ days) after the original flaring activity was detected with Fermi-LAT. Broadband spectral modeling shows that a synchrotron self-Compton (SSC) model with an external inverse-Compton (EC) component is preferred over a one-zone SSC model.
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All authors Atreya Acharyya, Avery Archer, Priyadarshini Bangale, Joshua Bartkoske, Wystan Benbow, James Buckley, Yu Chen, Jodi Christiansen, Alisha Chromey, Anne Duerr, Manel Errando, Miguel Escobar Godoy, Juan Escudero Pedrosa, Abe Falcone, Sydney Feldman, Qi Feng, Simon Filbert, Lucy Fortson, Amy Furniss, William Hanlon, Olivier Hervet, Claire Hinrichs, Jamie Holder, Zach Hughes, Thomas Humensky, Weidong Jin, Madalyn Johnson, Philip Kaaret, Mary P. Kertzman, Maria Kherlakian, Tobias Kleiner, Nikolas Korzoun, Sanchari Kundu, Mark Lang, Matthew Lundy, Eileen Meyer, John Millis, Connor Mooney, Patrick Moriarty, Reshmi Mukherjee, Wenmeng Ning, Rene A. Ong, Ashwani Pandey, Martin Pohl, Elisa Pueschel, John Quinn, Pazit Rabinowitz, Kenneth J. Ragan, Paul Reynolds, Deivid Ribeiro, Leandro Rizk, Emmet Thomas Roache, Iftach Sadeh, Alberto Sadun, Lab Saha, Glenn Sembroski, Ruo Shang, Megan Splettstoesser, Donggeun Tak, Anjana Talluri, James Tucci, Janeth Valverde, David Williams, Sam Wong, Margo Aller, Masoud Asadi-Zeydabadi, Ryan Hickox, Svetlana Jorstad, Sebastian Kiehlmann, Piatra Lusen, Allen Marscher, Walter Max-Moerbeck, Philipe De La Parra, Anthony Readhead, Katie Riley

High Energy Astrophysical Phenomena

Uncovering Hierarchical Sub-Population of Binary Black Holes

Muhammad Zeeshan and Richard O'Shaughnessy

Enabled by improved instruments with increasing sensitivity, the ongoing gravitational wave census now contains 259 binary black holes, numerous enough to unveil trends, substructure, and subpopulations which may provide key clues to their underlying formation mechanisms. In this work, motivated by evidence for multiple formation channels including hierarchical formation, we build a natively multi component mixture model for the binary black hole population, in which each component has an independently recovered rate, mass, spin, and spin misalignment model. (The components share a common redshift distribution.) Using a model carefully tuned to avoid parameter degeneracies, a powerlaw model plus five successively higher mass gaussians, we recover overall merger rates versus mass and trends versus redshift which are consistent with previously published results. Too, we recover previously identified overall trends versus spin: preferential alignment and low spin at low mass; large spin and isotropic spins at high mass. Critically, however, our multi-component model disagrees with previously published results, finding all components except the lowest mass are consistent with isotropy. Too, our multi-component model has a roughly hierarchical spectrum of gaussian mass peaks, but without the expected correlations between spin and mass expected from naked hierarchical formation
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Solar and Stellar Astrophysics

Pre-main Sequence B Stars Surrounding the Orion Nebula

P.H.F.B. Braz, A. Roman-Lopes, W.J.B. Corradi et al. (+6 more)

Pre-main sequence (PMS) early-type stars are rare due to their rapid evolution. Confirming PMS B stars is accordingly valuable for constraining higher mass star formation scenarios. Although the Orion Nebula (ON) region offers an ideal laboratory for such studies, its population of B stars remains poorly characterized. We aim to determine spectral types, masses, and ages of B and early A stars surrounding the ON, to identify robust PMS candidates. We combine optical and near-infrared spectroscopy to estimate spectral types using Brackett, He, Si, and Mg lines. Photometry from Gaia, 2MASS, and WISE is used to construct colour-magnitude diagrams to fit isochrones via chi-square minimisation, yielding stellar ages and masses. Dynamical masses from eclipsing binaries are employed as independent constraints on the mass range allowed for each spectral subtype. We derive stellar ages and masses for 53 stars and spectral classifications for 48 of them, identifying 30 PMS candidates, including some that were previously assigned to luminosity classes I-III. Several stars show spectroscopic variability, potentially linked to circumstellar material or binarity. Our combined spectroscopic and photometric approach identifies robust PMS B-star candidates and provides a validated framework for distinguishing them from evolved counterparts - in this instance, refining the census of early-types young stars in Orion. The age distribution of the PMS candidates offers preliminary clues about the star formation history of the ON region.
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All authors P.H.F.B. Braz, A. Roman-Lopes, W.J.B. Corradi, E. B. Amôres, M. S. Angelo, F. S. S. Maia, J. F. C. Santos Jr., A. E. Piatti, W. Reis

High Energy Astrophysical Phenomena

Large-scale emission from gamma-ray binaries: the case of LS 5039

J. R. Martinez and V. Bosch-Ramon

Abridged abstract: Context: Gamma-ray binaries hosting a non-accreting neutron star and a massive star exhibit multi-wavelength emission on different spatial scales. The interaction between their winds produces an outflow that can inflate a bubble or form a bow shock as it interacts with the surrounding medium. LS 5039 shows extended (1 pc-scale) X-ray emission that may arise from one of these large-scale structures. Aims: We explain and predict the large-scale emission from LS 5039. Methods: We modelled the thermal and non-thermal emission from five scenarios, representing different evolutionary phases, assuming particle acceleration at the mixed-wind termination shock: three bubble scenarios, treated with a one-zone model, and two bow-shock scenarios, studied with a multi-zone approach. We also investigated the radiation from escaping particles. Results: The extended X-rays are best explained as synchrotron radiation. Some scenarios predict detectable radio emission, while escaping particles may provide a minor steady contribution to the gamma rays in the powerful bow-shock scenario. Escaping protons with energies of 0.1-1 PeV could also inject up to $\sim10^{36}$ erg s$^{-1}$ into Galactic cosmic rays for optimistic injection luminosities. Conclusions: Gamma-ray binaries can efficiently accelerate particles on large scales, producing broadband emission and 0.1-1 PeV cosmic rays. Our results can guide future multi-wavelength observations to constrain the large-scale interaction, age, and birthplace of LS 5039.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph

Solar-System Abundances of $p$-Nuclides Probe Collective Neutrino Oscillations in Supernovae

Alexander Friedland, Derek J. Li, Giuseppe Lucente et al. (+3 more)

Direct evidence for collective neutrino oscillations in core-collapse supernovae remains elusive. We show that this quantum phenomenon leaves a footprint on the abundance pattern of proton-rich nuclides in the solar system. Modeling the $\nu p$-process using a $20\,M_\odot$ progenitor, we map out the dependence of the total yields on the starting radius of the oscillations, self-consistently coupling hydrodynamics and nucleosynthesis. The oscillations boost key $p$-nuclides ($^{92,94}\text{Mo}$, $^{96,98}\text{Ru}$) and long-lived $^{92}\text{Nb}$ by up to two orders of magnitude, bringing their abundances into agreement with the observations. The best match is found when oscillations commence within $10\text{ km}$ of the proto-neutron star surface, indicating fast collective oscillations.
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All authors Alexander Friedland, Derek J. Li, Giuseppe Lucente, Payel Mukhopadhyay, Ian Padilla-Gay, Amol V. Patwardhan

Earth and Planetary Astrophysics

Ephemeris Refinement for Qatar-4 b, HAT-P-18 b, and CoRoT-1 b with Small Telescope and TESS Observations

Heather B. Hewitt, Mikaela Chamlee, Trinity Hockman et al. (+45 more)

We present updated transit timing measurements for three hot Jupiters (Qatar-4 b, HAT-P-18 b, and CoRoT-1 b) by leveraging data collected from the MicroObservatory Telescope Network, a network of small, robotic ground-based telescopes, and the NASA Transiting Exoplanet Survey Satellite (TESS). By combining these data with archival published results, we present the most precise orbital solutions to date for all three systems, allowing for precise transit time predictions for future missions. We report an updated mid-transit time for Qatar-4 b of 2458919.5838 $\pm$ 0.000089 $\mathrm{BJD}_{\mathrm{TDB}}$ and an updated orbital period of 1.80536560 $\pm$ 0.00000021 days. For HAT-P-18 b, we find a mid-transit time of 2459743.85340 $\pm$ 0.000022 $\mathrm{BJD}_{\mathrm{TDB}}$ and an updated orbital period of 5.50802957 $\pm$ 0.00000012 days. For CoRoT-1 b, we report a mid-transit time of 2456268.99083 $\pm$ 0.000099 $\mathrm{BJD}_{\mathrm{TDB}}$ and an updated orbital period of 1.50896846 $\pm$ 0.000000071 days. Our results demonstrate improvements over recently published ephemerides, with reductions of 36.4%, 4.35%, and 17.5% in mid-transit time uncertainties and 65.0%, 77.4%, and 16.9% in orbital period uncertainties for Qatar-4 b, HAT-P-18 b, and CoRoT-1 b, respectively. The results of this study improve the precision of future transit predictions and demonstrate the value of coordinated small-telescope monitoring (and citizen science initiatives) when updating the orbital parameters of hot Jupiters.
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All authors Heather B. Hewitt, Mikaela Chamlee, Trinity Hockman, Annalise Igyarto, Dan van der Burg, Federico R. Noguer, Ira Bell, Jeremie Abides, Simon Abshear, Philip Arthur Ellis, Shashank Avinash Araokar, Eurico Bras, Jamie Buckingham, Dion Bumpus, Kartavya Chauhan, Logan Conrad, Koty Creel, Courtney Dammann, Samantha Duarte Rodriguez, Jeffrey Ensor, Benjamen Erickson, Adam Facciponti, Logan Farrar, Blaise Foca, Holly Foreman, Mark Foreman, Haley Fournier, Jeff Franklin, Keith Goss, Dustin Hubbartt, Nicolette Jeantilus, Justin Kobrin, Spencer Lunsford, Wyatt McCormick, Zachary McNeely, Kurtis Merrill, Sarah Miller, Dean Miller, Sofie Miura, Cody Montgomery, Karina Munoz, Keith Norton, Anna Plum, Jake Raby, Jay Thompson, Sohley Wallace-Pichardo, Molly N. Simon, Robert T. Zellem

Solar and Stellar Astrophysics

Luminous Red Novae as shock-powered transients I: Electron-scattering wings and deviations from Case B

Albert Sneppen, Kenta Hotokezaka and Christopher M. Irwin

Luminous red novae (LRNe) are a class of optical transients resulting from the mergers of binary stars or common envelope events. The population displays heterogeneous light curves with extended luminosity plateaus and/or secondary peaks, suggested to be powered by hydrogen recombination or shocks between pre- and post-merger ejecta. However, much of their spectroscopic behaviour remains unexplained. Using a sample of six LRNe, we identify telltale spectral evidence for shock processes across the LRNe luminosity range ($10^{38}$-$10^{41}\,\mathrm{erg/s}$): (i) fast ejecta sweeping up slower upstream material; (ii) composite epochs with two distinct components, namely a cool stellar-like continuum underneath a hot nebular recombination region; and (iii) extremely broad line wings extending to $1000$-$10\,000\,\mathrm{km/s}$. Such line profiles reveal photons scattering off hot electrons in an outflow ($T_e\sim5000$-$10\,000 \,\mathrm{K},\,v_{es}\!\sim\!300$-$500\, \mathrm{km/s}$), with recombination seen from both the upstream and downstream of the shock surface. Additionally, constraints on the density of the upstream medium are obtained from recombination-line ratios, where brighter LRNe show deviations from Case B, consistent with denser surrounding environments. Given the outflow's velocity and surrounding density constraints, the shock luminosity is sufficient to account for the total energetics of LRNe without requiring other energy-injection mechanisms. During the plateau phase, the scattering wings are hidden and line ratios are affected by radiative transport effects, which highlights the utility of post-plateau phase spectroscopy.
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Instrumentation and Methods for Astrophysics

Assembly, integration, and verification of MITESI: an optical testbed for simulating the ELT in the laboratory

Daniel J Ahrer, M. Concepción Cárdenas Vázquez, Thomas Bertram et al. (+5 more)

MITESI is an optical testbed which simulates key characteristics of the ELT, ultimately producing an artificial natural guide star. It was designed primarily to enable testing of the METIS instrument's SCAO system in closed loop. In this contribution, we discuss the assembly, integration and verification process of the testbed, taking the project from design to assembled hardware.
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All authors Daniel J Ahrer, M. Concepción Cárdenas Vázquez, Thomas Bertram, Peter Bizenberger, Armin Huber, Raphaël Pourcelot, Silvia Scheithauer, Horst Steuer

Solar and Stellar Astrophysics

Stellar heavy-element slope index

Gerd Roepke, Friedrich K. Roepke and David Blaschke

The distribution of heavy elements in stars is described using a phenomenological approach, in which Lagrange parameters related to temperature and the chemical potentials of protons and neutrons are introduced within a freeze-out concept. Slope parameters are considered which describe the gross behavior of the distribution of the heavy elements. Universality and deviations from universality are discussed, and various examples are provided. These slope parameters may be of interest for characterizing the conditions under which heavy elements form, but the astrophysical sites where heavy elements are produced remain to be determined.
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High Energy Astrophysical Phenomena

Multimessenger prospects of quasi-periodic eruptions

Vojtěch Witzany, Alessia Franchini, Matteo Bonetti et al. (+1 more)

Quasi-Periodic Eruptions (QPEs) are recurring soft X-ray transients that may be generated by inspirals of stellar-mass objects spiraling into supermassive black holes, known as extreme mass ratio inspirals (EMRIs). Independently, EMRIs and the gravitational-wave signals they generate are one of the key targets for the Laser Interferometer Space Antenna (LISA). What is the potential of a coincident detection of EMRIs both as a QPE and by LISA? Electromagnetic counterparts to LISA events would provide sky localization, enable standard siren measurements of the Hubble constant and constrain formation mechanisms of the corresponding inspirals. Combined observations would link the accurate measurements of black hole masses and spins to their galactic nuclear environments and would thus enable lasting synergies with various observations across the electromagnetic spectrum. However, most of the currently known QPEs imply EMRI orbital periods that place the frequencies of the corresponding gravitational-wave signal out of the LISA sensitivity band. Additionally, the selection biases of QPE detections and the LISA instrument may preclude a coincident detection. Future searches should focus on expanding the QPE catalogs and ultimately hunt for “golden” short-period QPEs that correspond to EMRIs that fall within the LISA band.
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All authors Vojtěch Witzany, Alessia Franchini, Matteo Bonetti, Luca Broggi

High Energy Astrophysical Phenomena

Observations of X-ray quasi-periodic eruptions

Thomas Wevers, Joheen Chakraborty, Erwan Quintin et al. (+2 more)

Quasi-periodic eruptions (QPEs) are a novel class of repeating nuclear transients, discovered exclusively in the X-ray band to date. Since their initial discovery in 2019, the QPE sample has grown to 13 sources, exhibiting large amplitude, quasi-regular eruptive variability patterns that are distinct from previously known modes of massive black hole variability. In this chapter, we provide a comprehensive overview of their observational characteristics. We review the X-ray spectral and timing properties of QPE eruptions, their long-term evolution, as well as the underlying quiescent emission, which is well described by thermally dominated, compact accretion disks. We discuss population-level emerging trends and selection biases, and present an updated census of their host galaxy properties. We also highlight the growing body of evidence pointing to strong connections between QPEs and tidal disruption events. Finally, we briefly summarize the key observational constraints on proposed QPE model interpretations, before looking ahead to the observational challenges and opportunities that will shape future progress in understanding this emerging population of nuclear transients.
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All authors Thomas Wevers, Joheen Chakraborty, Erwan Quintin, Michal Zajaček, Margherita Giustini

Astrophysics of Galaxies

Non-Thermal Physics Drives Compact, Self-Regulated Galaxy Morphologies at Cosmic Dawn

Michelle S. Park, Sergio Martin-Alvarez and Risa H. Wechsler

James Webb Space Telescope (JWST) has discovered unexpectedly bright, rapidly growing galaxies in the early universe, which were not predicted by most previously existing galaxy formation models. Using synthetic JWST observations of the Azahar simulation suite, we show that comprehensive non-thermal physics ("Full-Physics") produces compact, self-regulated galaxies that match observations from $z = 12$ to $z = 3$. This model also produces broad surface brightness distributions, where the bright end is dominated by compact sizes and bursty star formation. This compact starburst scenario naturally explains the detection of bright $z > 10$ galaxies in flux-limited surveys. By contrast, a model with standard hydrodynamics yields systems that are smaller and more concentrated than current data, while a model with calibrated supernova feedback produces unphysically large systems nearly twice the size of those observed. At lower masses ($\mathrm{M}_{*} < 10^{8}\,\mathrm{M}_{\odot}$), the Full-Physics model predicts sizes that are smaller than can be resolved with JWST, consistent with extrapolations from observations of higher-mass systems. Future observations with higher resolution could resolve this population and elucidate the physics driving the formation of the first galaxies.
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Earth and Planetary Astrophysics

Very Large Telescope observations of interstellar comet 3I/ATLAS III: High-resolution monitoring of CN and forbidden oxygen emission across the perihelion passage with ESPRESSO

Baltasar Luco, Thomas H. Puzia, Rohan Rahatgaonkar et al. (+2 more)

We characterize in 3I/ATLAS the heliocentric evolution of the CN production rate and the forbidden [OI] emission, describe the broader emission line inventory, and release the analysis tools and reduced data products to the community. We obtained high-resolution spectroscopy of 3I/ATLAS with VLT/ESPRESSO ($r_{\rm h}\!=\!1.67\!-\!2.45$ au). The CN production rates were derived by fitting the $B^2\Sigma^+\!-\!X^2\Sigma^+$ band using CometSpec, a publicly released Python package for flexible fluorescence modeling. The three forbidden [OI] lines were modeled to derive the green-to-red (G/R) flux ratio and a $\rm CO_2 / H_2O$ proxy. We fit $\text{Q}_{\rm CN}=a\,(r_{\rm h}/1\text{ au})^{\,b}$ to the production rate versus heliocentric distance relation. The pre-perihelion CN power-law index is $b_{\rm pre}\!=\!-4.62^{+1.25}_{-1.22}$, which is within the range observed for Solar System comets. The CN residuals about the smooth model show substantial scatter that we attribute to a combination of systematics and possible physical drivers that the current cadence cannot disentangle. The G/R ratio decreases from $\sim\!0.42\!\pm\!0.14$ at $r_{\rm h}\!\simeq\!2.4$ au to $\sim\!0.114\!\pm\!0.004$ near perihelion. The $\rm CO_2 / H_2O$ proxy spans $\sim 0.06 - 1.06$ and is comparable to the values reported by Subaru/HDS and SPHEREx and to those measured for 2I/Borisov. We additionally identify NiI and FeI and report post-perihelion production rates for $\rm C_2$ and CH. Our high-resolution monitoring of 3I/ATLAS reveals a $\rm CO_2$-rich coma that becomes progressively $\rm H_2O$-dominated near perihelion. Together with the public release of CometSpec and the reduced data, these results provide an empirical reference and a methodological framework for the next generation of interstellar object monitoring campaigns.
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All authors Baltasar Luco, Thomas H. Puzia, Rohan Rahatgaonkar, Juan Pablo Carvajal, Prasanta K. Nayak

Cosmology and Nongalactic Astrophysics

Tunnelling out of Starobinsky inflation: Raising the spectral tilt

Jose A. R. Cembranos, Jesús Luque and Javier Rubio

We propose a hybrid realization of Starobinsky inflation in which the inflationary epoch ends through vacuum decay. The model consists of an effective two-field system with a metastable Starobinsky branch shifted with respect to the true one. During the observable stage, the inflaton slow-rolls along the false branch, until a first-order phase transition in an orthogonal direction connects it to the true branch and ends inflation abruptly. This old-inflation-like exit skips the last part of the would-be Starobinsky trajectory. As a result, the Cosmic Microwave Background pivot scale exits the Hubble radius further from the minimum of the false branch than in ordinary Starobinsky inflation, raising the scalar spectral tilt $n_s$ while preserving the characteristic small tensor-to-scalar ratio. This provides a simple way of moving Starobinsky inflation towards the high-$n_s$ region favoured by recent ACT-related combinations. The same vacuum transition leaves a stochastic gravitational-wave relic whose peak frequency is controlled by the tunnelling timescale and the subsequent reheating history.
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Astrophysics of Galaxies

The first three-dimensional map of thermal phases in the local interstellar medium

Jonathan Shelest, Shmuel Bialy, Troy A. Porter et al. (+3 more)

The thermal state of interstellar gas controls whether it remains warm and diffuse or cools into dense clouds. Twenty-one centimetre observations have established a statistical picture of neutral-gas phases, but their three-dimensional architecture has not previously been mapped. Here we present $\mathcal{P}_{\rm 3D}$, a three-dimensional reconstruction of thermal phase in the local interstellar medium (ISM), covering a 1 kpc-diameter region centred on the Sun and sampled on a 2 pc Cartesian grid. $\mathcal{P}_{\rm 3D}$ combines high-resolution 3D maps of dust extinction and interstellar far-ultraviolet radiation with a neutral-ISM thermochemical model. The reconstruction reveals cold clouds surrounded by thermally unstable envelopes and embedded in a pervasive warm phase. Within $|z| \leq 150$ pc of the Galactic midplane, $\sim$41 % of the dust-traced neutral mass is thermally unstable, implying phase cycling on a timescale of $\sim$2.9-6 Myr. Yet the cold phase has a narrow density distribution, consistent with internal Mach numbers that are transonic at most ($\mathcal{M}_s \lesssim 1.5$). Together, these findings favour a dynamically cycling multiphase interstellar medium and motivate reassessing star-formation models that assume a single-phase, strongly supersonic cold-gas density field.
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All authors Jonathan Shelest, Shmuel Bialy, Troy A. Porter, Mark Wolfire, Matan Berko, Margarita Grinberg

Solar and Stellar Astrophysics

Polarization geometry of magnetohydrodynamic turbulence

Raphael Skalidis

We introduce a geometric framework that organizes the second-order statistics of the Elasser fields into polarization states on generalized Poincaré spheres. In this representation, energy, cross-helicity, residual energy, and the phase lag between counter-propagating wave packets emerge as complementary polarization parameters. We derive a Bloch-analogue equation governing the evolution of polarization states and show that distinct polarization geometries are associated with different cascade dynamics. The framework predicts that transitions in the turbulent spectral scaling coincide with changes in the polarization state of the interacting modes.
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Astrophysics of Galaxies

The Azahar Project: Non-Thermal Physics Drives Star Formation Burstiness and the Evolution of the UV Luminosity Density at Cosmic Dawn

Sergio Martin-Alvarez, Risa H. Wechsler and Debora Sijacki

JWST observations, which have pushed the discovery and characterization of galaxies to cosmic dawn, have revealed significant deficiencies in state-of-the-art galaxy formation simulations, motivating the need for novel, physically grounded models. We present the first results from the Azahar suite of ten high-resolution ($\sim$20 pc), large-volume zoom-in cosmological simulations, which follow the formation of thousands of galaxies and progressively incorporate radiative transfer (RT), cosmic rays (CRs), and magnetohydrodynamics in addition to the 'standard' baryonic physics. Our Non-Thermal model, which simultaneously includes RT and CRs on the fly, reproduces the observed UV luminosity function from high redshifts ($z \sim 14$) to cosmic noon ($z \sim 3$), as well as the evolution of the stellar mass function, the galaxy main sequence, and observed gas metallicities. It does so through a combination of burstier star formation, with enhanced variability on both long ($\gtrsim 50$ Myr) and short ($\lesssim 10$ Myr) timescales, and a transition from high to low outflow mass-loading factors over cosmic time as CR pressure builds up in the ISM. We find that simple (boosted) thermal SN feedback models fail to capture the cosmic evolution of the very first galaxies because they lack realistic feedback channels that operate on different timescales and have distinct thermodynamical properties, thereby either overproducing stellar mass or driving overly explosive outflows. Our results indicate that non-thermal galaxy formation physics is crucial for providing a robust theoretical framework with which to interpret the high-redshift galaxy populations now being uncovered by JWST.
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High Energy Astrophysical Phenomena

Ultraviolet to Infrared Spectroscopy of the Type Ibn SN 2023tsz Suggests a Lower-mass Progenitor

Sergiy S. Vasylyev, Griffin Hosseinzadeh, Luc Dessart et al. (+42 more)

Type Ibn supernovae are stripped-envelope explosions whose spectra indicate interaction with dense, helium-rich and hydrogen-poor circumstellar material (CSM), making them important probes of late-stage mass loss and progenitor stripping. We present extensive ultraviolet-to-near-infrared spectrophotometry of the Type Ibn SN 2023tsz, including two epochs of HST/STIS ultraviolet (UV) spectroscopy and ground-based optical and near-infrared follow-up observations. The spectra are dominated by intermediate-width emission lines at all phases after maximum light, suggesting that much of the luminosity originates in a cold dense shell (CDS) formed by interaction between the ejecta and CSM. We compare the observations to one-dimensional non-local-thermodynamic-equilibrium radiative-transfer models of a helium-star explosion with a mass of $4 M_{\odot}$ at the onset of helium burning. The models reproduce the strong optical and near-infrared He I lines and require an added X-ray irradiation field to match the highly ionized UV features. The spectra are best reproduced by models with an X-ray irradiation power of $L_X \approx 10^8 L_{\odot}$, with the preferred models favoring CDS radii of order $(1.5$–$2) \times 10^{15}$ cm, velocities of $\sim 5 \times 10^7$ cm s$^{-1}$, and interaction powers of a few times $10^{42}$ erg s$^{-1}$. In the optical, the preferred models shift from higher interaction power and smaller radii at early times to lower power and larger radii at later times. These results add to the growing evidence that at least some SNe Ibn arise from lower-mass helium stars whose final evolution is shaped by binary interaction.
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All authors Sergiy S. Vasylyev, Griffin Hosseinzadeh, Luc Dessart, Ori Fox, David J. Sand, Alexei V. Filippenko, Qinan Wang, D. Andrew Howell, Jennifer E. Andrews, Moira Andrews, Pallas Beddow, K. Azalee Bostroem, Thomas G. Brink, Peter J. Brown, Asia deGraw, Yize Dong, Joseph Farah, Thomas R. Geballe, Sebastian Gomez, Emily T. Hoang, Brian Hsu, Saurabh W. Jha, Patrick Kelly, Curtis McCully, Darshana Mehta, Megan Newsome, Yuan Q. Ni, Seong Hyun Park, Jeniveve Pearson, Neil Pichay, Justin Pierel, Aravind P. Ravi, Nicolas E. Meza Retamal, Melissa Shahbandeh, Manisha Shrestha, Nathan Smith, Bhagya M. Subrayan, Tamás Szalai, Stefano Valenti, Schuyler D. Van Dyk, Jeonghee Rho, Kathryn Wynn, Yi Yang, Yossef Zenati, WeiKang Zheng

Cosmology and Nongalactic Astrophysics

Forest without Trees is still Fruitful: Constraints on the thermal state of the neutral IGM at $z\approx5.6$ with the 21-cm forest power spectrum

Tomáš Šoltinský, Arnab Chakraborty, Girish Kulkarni et al. (+10 more)

Neutral regions of the intergalactic medium (IGM) during the Epoch of Reionization (EoR) remain largely unexplored due to the limitations of existing probes. Owing to discoveries of numerous high-redshift radio-bright sources, the 21-cm forest, a series of absorption features imprinted by the neutral IGM in the spectra of such sources, now offers an attractive probe of the thermal and ionization state of the predominantly neutral IGM at $z\gtrsim5.5$. We analyse archival upgraded Giant Metrewave Radio Telescope (uGMRT) observations of J352-15, the brightest known radio-loud quasar in the EoR ($z=5.82$), to measure the one-dimensional (1D) power spectrum of the 21-cm forest. By comparing the observed power spectrum with forward-modelled synthetic spectra generated from cosmological simulations spanning a wide range of ionization and X-ray pre-heating scenarios, we perform Bayesian inference even in the absence of a statistical detection. We also present an independent Murchison Widefield Array measurement, although its lower sensitivity prevents competitive constraints. Using uGMRT, we achieve a sensitivity of $3.62\,\rm mJy\,beam^{-1}$ per $6.1\,\rm kHz$ channel. While we do not detect the 21-cm forest statistically, the null detection jointly constrains the mean neutral hydrogen fraction, $\langle x_{\rm HI}\rangle$, and the mean temperature of the neutral IGM, $\langle T_{\rm HI}\rangle$. At the $68\%$ credible level, our analysis disfavours cold and substantially neutral IGM models at $z\approx5.6$, including models with $\langle T_{\rm HI}\rangle \lesssim 27\,\rm K$ for $\langle x_{\rm HI}\rangle=0.1$. These limits probe parameter space allowed by existing Ly$\alpha$ and 21-cm observations, indicating substantial pre-heating of the neutral IGM above the adiabatic cooling floor. This demonstrates that the 21-cm forest has entered the regime of observationally informative statistics.
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All authors Tomáš Šoltinský, Arnab Chakraborty, Girish Kulkarni, Matteo Viel, Cathryn M. Trott, Rashmi Sagar, Nithyanandan Thyagarajan, James S. Bolton, Benedetta Ciardi, Emma V. Ryan-Weber, Soumak Maitra, Abhirup Datta, Nirupam Roy

Astrophysics of Galaxies

How large can galaxies be? Ultra-deep imaging of IC 1101, the most extended known galaxy

Carlos Marrero-de la Rosa, Ignacio Trujillo, Ignacio Ruiz Cejudo et al. (+12 more)

The maximum physical extent that galaxies can reach is poorly understood. In this regard, IC 1101, one of the most extended and massive galaxies known, provides a valuable opportunity to constrain the upper limit of galaxy sizes at the present epoch. Previous deep imaging of the system confirmed its enormous extension, but did not indicate whether it has an edge. We explore this issue using the deepest images ever taken of this galaxy; ultra-deep g- and r- band imaging from the INT/WFC, reaching {\mu} = 30 mag arcsec^-2 (3{\sigma} in an area equivalent to 10 x 10 arcsec^2). We model and subtract the scattered light from both stars and the galaxy itself using an extended PSF characterization and a hybrid wavelet-based deconvolution. Using a combination of surface brightness, colour, and stellar mass density profiles oriented at different position angles, we find that the main body of IC 1101 extends to Redge = 260 kpc along the semi-major axis (assuming the redshift of Abell 2029, z = 0.077), enclosing 3.4 x 10^12 M_sun in stars. This Redge is among the largest edge radii measured for any galaxy to date, placing IC 1101 at the extreme upper end of the mass-size relation. In addition, we report a large number of asymmetrical, very low surface brightness features around the galaxy that are spatially consistent with the large-scale disturbances observed in the intracluster medium through X-ray studies of the Abell 2029 cluster, in which IC 1101 is embedded. With a confirmed diameter of around 520 kpc, IC 1101 stands as the largest galaxy known to date; yet, its outskirts show clear signatures of ongoing mass assembly, indicating that its spatial extent is still growing.
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All authors Carlos Marrero-de la Rosa, Ignacio Trujillo, Ignacio Ruiz Cejudo, Mireia Montes, Fernando Buitrago, Giulia Golini, Sergio Guerra Arencibia, Andrés Asensio Ramos, Raúl Infante-Sainz, Adriana de Lorenzo-Cáceres, Jairo Méndez-Abreu, Samane Raji, Javier Román, Manuel Sánchez-Benavente, Zahra Sharbaf

Astrophysics of Galaxies

Tighter Dark Matter Constraints from the Projected Mass Method: A Neural Network Enhanced Method for Galaxy Groups and Clusters

Yinbo Huang and David Benisty

Measuring the total mass of the Milky Way and nearby galaxy groups is difficult because classical dynamical estimators rely on assumptions about satellite orbital geometry that are rarely satisfied in practice, and because only a handful of satellite galaxies are typically available as kinematic tracers. We present a new framework that corrects the well-known Projected Mass Estimator (PME) using a residual neural network trained on thousands of simulated galaxy groups from the IllustrisTNG cosmological simulation. Separate networks are trained for each satellite sample size, from as few as 5 satellites up to 50, so that the correction automatically accounts for the statistical noise that dominates when only a small number of tracers is available. In tests on simulated halos, the classical PME systematically overestimates halo masses by factors of $M_{\rm proj}/M_{\rm true} = 1.30^{+0.72}_{-0.62}$ (using the 2D distance) and $1.46^{+0.97}_{-0.72}$ (using the 3D distance), with RMSE of 0.29 and 0.32 dex respectively. The neural-network correction reduces this to $M_{\rm proj}/M_{\rm true} = 1.02^{+0.30}_{-0.26}$ with an RMSE of 0.13 dex. Applied to the Milky Way, the method yields a total mass of $M_{\rm MW} = 1.144^{+0.399}_{-0.296}\times10^{12}\,M_\odot$, with estimates based on the brightest 5-10 satellites favoring a somewhat lower range of $(0.8-0.95)\times10^{12}\,M_\odot$. The modified PME gives a tighter constraint on the virial masses and the inferred dark matter content of galaxy groups and clusters.
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Cosmology and Nongalactic Astrophysics

Searching for Folded Primordial Non-Gaussianity with Galaxy Surveys

Si-Xiang Yang and Oliver H. E. Philcox

Large-scale structure provides a powerful probe of inflationary physics through primordial non-Gaussianity (PNG): the galaxy power spectrum depends on local PNG through scale-dependent bias, while the galaxy bispectrum depends sensitively on both equilateral and orthogonal PNG. In this paper, we study whether galaxy surveys can also probe folded PNG, whose shape is enhanced near $k_1+k_2-k_3\rightarrow0$. We consider three inflationary models with folded PNG, including excited initial states, imaginary speeds of sound, and dissipative inflation. These models fall into two classes: cutoff-regulated cases in which the folded-enhanced region has a power-law width, and dissipation-regulated cases in which the enhanced region is exponentially narrow. We develop a numerical pipeline for computing the corresponding PNG contributions to the redshift-space galaxy power spectrum multipoles and bispectrum monopole within the EFTofLSS. Using Fisher forecasts, we show that most of the constraining power on folded PNG comes from the galaxy bispectrum. For the cutoff-regulated models, nuisance parameter marginalization causes only a mild loss of information at large folded enhancement, but finite Fourier-space binning degrades constraints once the folded region becomes narrower than the bin width. For the dissipation-regulated models, the exponentially narrow folded enhancement is hard to resolve and the observable signal instead comes from the broader support of the template, leading to weaker binning dependence but larger overlap with the equilateral template. Our results show that folded PNG is a distinctive and promising target for galaxy bispectrum analyses, and the detectability depends on the width and morphology of the folded enhancement. The numerical pipeline developed in this work is general and can be used to study a wide class of non-separable primordial bispectra.
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Cosmology and Nongalactic Astrophysics

Primordial tensor mode from the neutrino sector

Shohei Saga and Shuichiro Yokoyama

We show that a regular solution for primordial tensor fluctuations can arise from the higher-order multipoles of the collisionless neutrino distribution after neutrino decoupling. Focusing on the leading case with the neutrino octupole mode (tensor-octupole mode), we derive the initial conditions for the Einstein-Boltzmann system and calculate angular power spectra for the cosmic microwave background (CMB) anisotropies. Compared with the standard gravitational-wave mode, the tensor-octupole mode has a weaker large-scale metric response. It therefore gives a suppressed reionization bump and a different oscillation phase in the tensor CMB power spectra, providing a way to separate it from the standard tensor mode.
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Astrophysics of Galaxies

On the reconstruction of the Rotation Curve for Milky Way and its spacetime implications: a Machine Learning approach

Aritra Sanyal, Swapan Das, Farook Rahaman et al. (+1 more)

We propose a machine learning-assisted analytical reconstruction of the Milky Way rotation curve and discuss its implications in a relativistic spacetime context. The rotation curve is reconstructed using 73 observational data points over the range 0.1-95.56 kpc, and we compare the performances of Ridge regression, LASSO regression, and feed-forward neural networks using a physically motivated functional basis. Ridge regression yields the most stable prediction with R2 = 0.9824 +/- 0.0064 and RMSE = 3.75 km/s, while retaining analytical interpretability. We embed the reconstructed velocity profile into a static, spherically symmetric spacetime, enabling the determination of the redshift function and the mass function through Einstein's equations. We verify that all energy conditions are satisfied, the sound speed remains subluminal, the circular orbits are stable, and the gravitational energy is negative, confirming the attractive nature of gravity. This framework provides a statistically validated, data-driven alternative to conventional dark matter halo models and establishes a direct connection between kinematical observables and relativistic spacetime geometry.
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All authors Aritra Sanyal, Swapan Das, Farook Rahaman, Saibal Ray

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Particle production from bubble collisions

Anish Ghoshal, Pratyay Pal and Alessandro Strumia

Collisions of ultra-relativistic bubbles during cosmological phase transitions can produce particles much heavier than the transition scale. Previous analyses modelled this process as the off-shell decay of the scalar background. We show that its results parametrically overestimate hard particle production and depend on the gauge choice and the coordinate choice in field space. We propose an alternative formalism, analogous to the partonic description of high-energy collisions. In the ultra-relativistic limit, the colliding bubbles undergo nearly free passage and hard production arises from on-shell scatterings among the quanta constituting the Lorentz-contracted walls. We apply this approach to heavy scalar, fermion, and vector particle production, and study the implications for dark matter, leptogenesis, graviton production and primordial gravitational waves.
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