Peer Revenue Now accepting positions

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Astrophysics

astro-ph Watch Astrophysics

Wednesday 5 August

Cosmology and Nongalactic Astrophysics

Is Dark Matter Really Matter?

Jun-Qian Jiang and Arman Shafieloo

In the standard model of cosmology, it is assumed that dark matter is pressureless with equation of state $w=0$ and dark energy has $w=-1$. We test these assumptions jointly using DESI DR2 distance measurements, including the recent Lyman-$\alpha$ full-shape Alcock-Paczynski (AP) information, DES supernovae, and two complementary CMB treatment. When constant $w_{dm}$ and $w_{de}$ are varied together, we find $w_{dm}=0.000968^{+0.000501}_{-0.000496}$ and $w_{de}=-0.9380^{+0.0259}_{-0.0262}$ (68%). With an alternative CMB treatment that marginalizes over the lensing spectrum, the corresponding constraints are $w_{dm}=0.000870^{+0.000408}_{-0.000410}$ and $w_{de}=-0.9353^{+0.0258}_{-0.0254}$. Both standard $\Lambda$CDM values are disfavored at approximately $2\sigma$ in the joint extension. Neither parameter departs significantly from its standard value when only that parameter is varied. This behavior arises because late-time distances favor $w_{de}>-1$, while maintaining the early-Universe physical matter density requires a compensating positive $w_{dm}$, which changes the mapping to the matter density today. Allowing dynamical dark energy further highlights the complexity of the situation: phantom crossing for dark energy makes $w_{dm}=0$ consistent with the data, whereas a positive $w_{dm}$ preference persists when crossing is forbidden. Interestingly, the Pad'e-$w$ parameterization that provides a flexible description of a class of quintessence models (with no phantom crossing), along with $w_{dm}$ free, is even mildly favored over the phantom-crossing $w_0w_a$ model according to both the best-fit $\chi^2$ and the DIC under both CMB treatments. One can conclude that the apparent preference for phantom crossing may instead reflect deviations in the dark-matter sector rather than dark-energy dynamics alone. [abridged]
Read the full abstract

Cosmology and Nongalactic Astrophysics

Non-Thermal Pressure due to Gas Motions in the Intracluster Medium: Confronting XRISM/Resolve with TNG-Cluster Simulations

Erwin T. Lau, Naomi Ota and Daisuke Nagai

Intracluster medium (ICM) gas motions probe cluster assembly, feedback, and non-thermal pressure support, but recent XRISM observations reveal velocity dispersions and non-thermal pressure fractions systematically lower than simulations predict, with extreme systems such as Abell 2029 falling below nearly all simulated clusters. Using the TNG-Cluster simulations, we show that the non-thermal pressure fraction depends sensitively on cool-core state and formation history, and provide a two-scale fitting function capturing both the inner cool-core suppression and outer rise of the radial profile. By forward-modeling mock XRISM observations and comparing them with both projected and intrinsic three-dimensional quantities, we find that azimuthal variations and projection effects contribute to the deficit in the observed velocity dispersion and non-thermal pressure fraction. This bias increases with radius and partially offsets the intrinsic outward rise in the true three-dimensional non-thermal pressure fraction. However, these effects cannot explain the extremely low values of the non-thermal pressure fraction observed in Abell 2029, which fall below approximately the 0th-6th percentiles of the simulated cool-core cluster distribution at every measured radius under both the turbulence-only and turbulence-plus-bulk definitions. The remaining tension points to rare dynamical conditions or missing physics affecting the amplitude of gas motions in current ICM models.
Read the full abstract

Instrumentation and Methods for Astrophysics

Swept-source heterodyne detection for interferometry in the H band

Félix Gudin and Nicolas Forget

It is well established that direct-detection interferometry outperforms heterodyne interferometry in terms of signal-to-noise ratio at optical wavelengths, not only because of the limited electronic bandwidth of photodetectors (typically <100 GHz), but also due to the shot-noise contribution of the optical local oscillator. The large-scale production of high-quality and cost-effective telecom components in the J+H band, and more recently in the K band, may open new schemes for the heterodyne signal detection and processing (e.g. correlation) as well as for the transport, distribution and control of the local oscillator. We describe how high-repetition-rate frequency-swept sources and telecom components could be exploited to parallelize, at reasonable cost, a large number of coherent detectors to expand the spectral coverage. We also present a first laboratory single-channel proof of concept that achieves a signal-to-noise ratio (SNR) probably sufficient for observing the brightest stars in the H band with telescopes of ~1 m2 at short integration time (<100 ms).
Read the full abstract

Instrumentation and Methods for Astrophysics

Demonstration of a Single-Laser-Diode-Pumped Ti:Sapphire Astrocomb on the Southern African Large Telescope

Ewan Allan, Yuk Shan Cheng, Kamalesh Dadi et al. (+13 more)

Astrocombs – broadband lasers comprising thousands of narrow, uniformly spaced and atomically-referenced spectral lines – offer gold-standard wavelength calibration for ground-based optical telescopes, with the potential for the cm/s precision needed for radial-velocity follow-ups of exoplanet candidates from photometric space missions like Kepler, TESS and PLATO. Current astrocombs, particularly those operating in the visible spectrum, are complex and expensive, putting them beyond the reach of many observatories. Here, we present the first on-instrument demonstration of a new and simple astrocomb concept, providing calibration light across nearly the entire 550 nm to 890 nm red channel of the Southern African Large Telescope's High Resolution Spectrograph (SALT-HRS). An octave-spanning supercontinuum generated in a silicon nitride waveguide by a GPS-referenced diode-pumped Ti:sapphire laser is filtered to 21 GHz before fibre delivery to the spectrograph. Using the astrocomb, we obtain the wavelength solution for one order of SALT-HRS and the wavelength-dependent line-spread function of the instrument. With potential for further extension into the blue spectral region, this uniquely simple architecture brings visible-to-infrared astrocomb technology within the reach of a wider range of astronomical observatories.
Read the full abstract

All authors Ewan Allan, Yuk Shan Cheng, Kamalesh Dadi, Pablo Castro-Marin, Jake M. Charsley, William Newman, Abdullah Alabbadi, Hanna Ostapenko, Richard A. McCracken, Pascal Del'Haye, Thomas Willemsen, Tobias Gross, Daniel L. Holdsworth, Malcolm C. Scarrott, Lisa A. Crause, Derryck T. Reid

Solar and Stellar Astrophysics

Characterization of the variability of the blue supergiant HD 14134

Suryani Guha, Michaela Kraus, Julieta P. Sanchez Arias et al. (+2 more)

The post-main sequence (MS) evolution of massive stars encompasses phases in which the stars display high variability. One such class of objects are the blue supergiants which may be in either the pre- or post-red supergiant phase of their evolution. Their variability patterns might provide constraints for a proper classification of the objects. We aim to characterise the observed variability of the B supergiant HD14134 and to investigate the imprint of a time-variable wind on the brightness variation of the star and its impact on the detectability of pulsation signals. Spectroscopic data were collected over a 5-month period and combined with photometry from TESS. Stellar parameters were derived from modelling of the time-averaged spectrum with CMFGEN and the SED and were confirmed with stellar evolution models computed with MESA. The light curves and radial velocity curves of selected lines were analysed to determine pulsation signals. The wind variability and its imprint on the stellar brightness were investigated from an analysis of the Halpha line. Predictions of mode excitations were computed with the GYRE pulsation code and compared to the frequencies determined from the observations. A g-mode with a period of ~19.2 d and its harmonics are consistently detected in all data sets. The spectra unveil strong, non-periodic wind variability and 3 frequency signals were identified as due to this wind variability. The stellar parameters and age derived for HD14134 together with the absence of radial pulsations classify the star as a post-MS object evolving towards the red-supergiant stage, questioning its classification as alpha Cyg variable. The results reinforce that simultaneous long-term spectroscopic and photometric monitoring is indispensable for reliable frequency detections and for disentangling of variabilities imprinted by a time-variable wind from those imposed by pulsations.
Read the full abstract

All authors Suryani Guha, Michaela Kraus, Julieta P. Sanchez Arias, Peter Nemeth, Krzysztof Kaminski

Cosmology and Nongalactic Astrophysics

Fractal properties of the cosmic web

Jaan Einasto

The cosmic web is one of the most complex systems in nature, consisting of galaxies and clusters of galaxies connected by filaments and walls, and separated by large empty regions known as cosmic voids. The most common method for describing the web is the correlation function and its derivative, the structure function and fractal dimension function. In this paper I review the fractal properties of the cosmic web within the concordance {\Lambda}CDM framework. I describe how the fractal function is derived from the angular and spatial distributions of galaxies and discuss the relations between these approaches.
Read the full abstract

High Energy Astrophysical Phenomena

Observation of the Moon and Sun shadows with cosmic rays at an average energy of $\text{7}{\times}\text{10}^\text{17}\,$eV

The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu et al. (+346 more)

Interactions of cosmic rays with the Moon and the Sun produce deficits in their arrival-direction distributions relative to an isotropic flux. Such shadows have been observed previously at energies between $10^{12}\,$eV and $10^{16}\,$eV. We report the first observation of the Moon and Sun shadows at cosmic-ray energies larger than about $10^{16}\,$eV (average energy of $7\times10^{17}\,$eV), using data collected by the Pierre Auger Observatory. We employ data from three detector arrays covering $3000\,\text{km}^2$, $27\,\text{km}^2$, and $2\,\text{km}^2$, with spacings of $1500\,\text{m}$, $750\,\text{m}$, and $433\,\text{m}$, respectively. The data amount to over 10.6 million events. The Moon and Sun shadows are detected with a combined significance of approximately $3\sigma$. These observations confirm the pointing accuracy of the Surface Detector of the Pierre Auger Observatory using celestial bodies. From the combined Sun and Moon shadows, we infer an overall angular resolution of $(0.59^{+0.15}_{-0.11})^\circ$.
Read the full abstract

All authors The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu, M. Aglietta, M. Ahmed, I. Allekotte, K. Almeida Cheminant, R. Aloisio, J. Alvarez-Muñiz, A. Ambrosone, J. Ammerman Yebra, L. Anchordoqui, B. Andrada, L. Andrade Dourado, L. Apollonio, C. Aramo, J.C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, Y. Balibrea, A. Baluta, F. Barbato, A. Bartz Mocellin, O. Batalla Cruz, J.P. Behler, C. Berat, M.E. Bertaina, M. Bianciotto, P.L. Biermann, V. Binet, K. Bismark, T. Bister, J. Biteau, J. Blazek, J. Blümer, M. Boháčová, D. Boncioli, C. Bonifazi, N. Borodai, J. Brack, P.G. Brichetto Orquera, S. Buitink, A. Bwembya, T.R. Caba Pineda, K.S. Caballero-Mora, S. Cabana-Freire, L. Caccianiga, J. Caraça-Valente, R. Caruso, A. Castellina, F. Catalani, G. Cataldi, L. Cazon, M. Cerda, B. Čermáková, A. Cermenati, K. Cerny, J.A. Chinellato, J. Chudoba, L. Chytka, R.W. Clay, A.C. Cobos Cerutti, R. Colalillo, R. Conceição, G. Consolati, M. Conte, F. Convenga, D. Correia dos Santos, P.J. Costa, C.E. Covault, M. Cristinziani, C.S. Cruz Sanchez, S. Dasso, K. Daumiller, B.R. Dawson, R.M. de Almeida, E.-T. de Boone, B. de Errico, J. de Jesús, S.J. de Jong, J.R.T. de Mello Neto, I. De Mitri, D. de Oliveira Franco, F. de Palma, V. de Souza, E. De Vito, A. Del Popolo, O. Deligny, N. Denner, K. Denner Syrokvas, L. Deval, A. di Matteo, C. Dobrigkeit, J.C. D'Olivo, L.M. Domingues Mendes, T. Dominguez, Y. Dominguez Ballesteros, Q. Dorosti, R.C. dos Anjos, J. Ebr, F. Ellwanger, R. Engel, M. Erdmann, A. Etchegoyen, C. Evoli, H. Falcke, G. Farrar, A.C. Fauth, T. Fehler, F. Feldbusch, A. Fernandes, M. Fernández Alonso, B. Fick, J.M. Figueira, P. Filip, A. Filipčič, B. Flaggs, A. Franco, M. Freitas, T. Fujii, A. Fuster, C. Galea, B. García, C. Gaudu, P.L. Ghia, U. Giaccari, M. Giammarco, C. Glaser, F. Gobbi, F. Gollan, G. Golup, P.F. Gómez Vitale, J.P. Gongora, N. González, D. Góra, A. Gorgi, M. Gottowik, F. Guarino, G.P. Guedes, Y.C. Guerra, L. Gülzow, S. Hahn, P. Hamal, M.R. Hampel, P. Hansen, A. Haungs, M. Havelka, T. Hebbeker, C. Hojvat, J.R. Hörandel, P. Horvath, M. Hrabovský, T. Huege, A. Insolia, P.G. Isar, M. Ismaiel, P. Janecek, V. Jilek, K.-H. Kampert, B. Keilhauer, V.V. Kizakke Covilakam, H.O. Klages, M. Kleifges, A. Klingel, J. Köhler, F. Krieger, M. Kubatova, N. Kunka, B.L. Lago, N. Langner, N. Leal, M.A. Leigui de Oliveira, Y. Lema-Capeans, A. Letessier-Selvon, I. Lhenry-Yvon, L. Lopes, M. Mallamaci, S. Mancuso, D. Mandat, P. Mantsch, A.G. Mariazzi, C. Marinelli, I.C. Mariş, G. Marsella, D. Martello, S. Martinelli, O. Martínez Bravo, A. Martínez-Mendez, M.A. Martins, H.-J. Mathes, J. Matthews, G. Matthiae, E. Mayotte, S. Mayotte, P.O. Mazur, G. Medina-Tanco, D. Melo, A. Menshikov, C. Merx, S. Michal, M.I. Micheletti, L. Miramonti, M. Mogarkar, S. Mollerach, F. Montanet, L. Morejon, K. Mulrey, R. Mussa, W.M. Namasaka, S. Negi, L. Nellen, K. Nguyen, G. Nicora, M. Niechciol, D. Nitz, D. Nosek, A. Novikov, V. Novotny, L. Nožka, A. Nucita, L.A. Núñez, S.E. Nuza, J. Ochoa, M. Olegario, C. Oliveira, L. Östman, M. Palatka, J. Pallotta, G. Parente, T. Paulsen, M. Pech, J. Pękala, R. Pelayo, C. Pérez Bertolli, L. Perrone, S. Petrera, T. Pierog, M. Pimenta, M. Platino, P. Privitera, C. Priyadarshi, M. Prouza, K. Pytel, S. Querchfeld, J. Rautenberg, D. Ravignani, J.V. Reginatto Akim, M.Z. Rennó, A. Reuzki, J. Ridky, F. Riehn, M. Risse, V. Rizi, B. Rocha Moldes, E. Rodriguez, G. Rodriguez Fernandez, J. Rodriguez Rojo, S. Rossoni, M. Roth, E. Roulet, A.C. Rovero, A. Saftoiu, M. Saharan, F. Salamida, H. Salazar, G. Salina, P. Sampathkumar, N. San Martin, J.D. Sanabria Gomez, F. Sánchez, F.M. Sánchez Rodriguez, E. Santos, F. Sarazin, R. Sarmento, R. Sato, P. Savina, V. Scherini, H. Schieler, M. Schimp, D. Schmidt, O. Scholten, H. Schoorlemmer, P. Schovánek, F.G. Schröder, J. Schulte, T. Schulz, S.J. Sciutto, M. Scornavacche, A. Sedoski, S. Sehgal, S.U. Shivashankara, G. Sigl, K. Simkova, F. Simon, R. Šmída, S. Soares Sippert, P. Sommers, S. Stanič, J. Stasielak, P. Stassi, S. Strähnz, M. Straub, T. Suomijärvi, A.D. Supanitsky, Z. Svozilikova, Z. Szadkowski, F. Tairli, A. Tapia, C. Taricco, C. Timmermans, O. Tkachenko, P. Tobiska, C.J. Todero Peixoto, B. Tomé, A. Travaini, P. Travnicek, C. Trimarelli, M. Tueros, M. Unger, R. Uzeiroska-Geyik, L. Vaclavek, M. Vacula, I. Vaiman, J.F. Valdés Galicia, L. Valore, P. van Dillen, E. Varela, V. Vašíčková, A. Vásquez-Ramírez, D. Veberič, I.D. Vergara Quispe, S. Verpoest, V. Verzi, J. Vicha, S. Vorobiov, J.B. Vuta, A.A. Watson, A. Weindl, M. Weitz, L. Wiencke, H. Wilczyński, B. Wundheiler, B. Yue, A. Yushkov, E. Zas, D. Zavrtanik, M. Zavrtanik

Astrophysics of Galaxies

MIGHTEE-HI: Environmental effects of cosmic filaments on extragalactic HI detections in the COSMOS and XMM-LSS fields

Seoyoung Lyla Jung, Madalina N. Tudorache, Matt J. Jarvis et al. (+8 more)

Cosmic filaments have been recognised as influencing galaxy evolution, but their connection to galactic cold gas reservoirs is elusive, particularly at low redshifts. We investigate the influence of filaments on neutral hydrogen (HI) detections in galaxies at $0.02<z<0.09$, using the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) survey in the COSMOS and XMM-LSS fields. We measure the fraction of optical galaxies from the Dark Energy Spectroscopic Instrument (DESI) Survey detected in HI emission as a function of stellar mass, morphology, local density, and the distance to the nearest filament. We find that galaxies closer to filaments have higher stellar masses, higher local densities, and a larger early-type fraction, all of which affect the HI detection. After controlling for these dependencies, filaments have measurable effects on HI detection. Late-type galaxies in low-local density environments show reduced HI detection fractions close to filaments across all stellar mass ranges, suggesting potential gas depletion through ram pressure stripping and cosmic web detachment. Massive early-type galaxies show an enhanced HI detection fraction in filaments compared to the voids, suggesting possible gas replenishment through filamentary accretion or gas-rich mergers. Our results suggest that cosmic filaments influence galactic HI gas reservoirs through various competing processes, whose relative importance varies with stellar mass and local density.
Read the full abstract

All authors Seoyoung Lyla Jung, Madalina N. Tudorache, Matt J. Jarvis, Michalina Maksymowicz-Maciata, Maarten Baes, Marcin Glowacki, Natasha Maddox, Anastasia A. Ponomareva, Kristine Spekkens, Tariq Yasin, Bohan Yue

High Energy Astrophysical Phenomena

Population synthesis and detection prospects for Galactic long-period transients with LISA

Arthur G. Suvorov, Nikolaos Karnesis and Valeriya Korol

The recently-discovered long-period radio transients represent a puzzling new class of astrophysical sources, some of which are thought to be compact binary systems emitting a pulse once per orbit. If this interpretation is correct, the orbital period–and therefore the gravitational-wave frequency–is directly encoded in the radio signal, which typically lies in the millihertz band. In this work, we explore whether these systems can be detected by the Laser Interferometer Space Antenna (LISA). Assuming that this phase-locking between radio pulses and orbital motion applies broadly across the population, we construct synthetic source catalogues informed by both observations and theoretical models of related systems, such as cataclysmic variables. We estimate that between $\sim 0.05\%$ and $\sim 6\%$ of long-period transients will be detectable within four years of observation with LISA, depending on astrophysical assumptions. For detectable systems, we find injected frequencies are recoverable to one part in $\sim 10^{5}$, amplitudes to within a factor $\sim 2$, and the sky positions to within $\sim$30 square degrees. Our results demonstrate that gravitational-wave observations can provide direct evidence for the binary nature of these sources and, importantly, can guide future radio surveys by predicting pulse periods, sky positions, and orbital properties. The mismatch between extracted frequency derivatives and that imposed by gravitational-wave decay is also computed to show that the likelihood of electromotive losses driving orbital evolution can be assessed for each detectable candidate.
Read the full abstract

High Energy Astrophysical Phenomena

Type I X-Ray Burst Models With Rotation

David Martin and Jordi Jose

Type I X-ray bursts are powered by unstable thermonuclear burning on the surface of accreting neutron stars in close binary systems. These brief X-ray flashes, with light curves featuring rise times of $1-10$ s, durations of $10-100$ s, and recurrence periods of hours to days, represent the most frequent stellar explosions in our Galaxy. With typical energies of $\sim 10^{39}-10^{40}$ erg, they rank among the most powerful astrophysical transients after supernovae and classical novae. To date, roughly 120 bursting X-ray binaries have been identified in the Milky Way. Several studies have been conducted to characterize the dynamics of these events, with emphasis on reproducing the observed recurrence periods and light curve shapes. In this paper we show, for the first time, that rotation is a key factor shaping the properties of Type I X-ray bursts in rapidly spinning systems. The inclusion of centrifugal forces, together with a suite of rotationally-induced mixing mechanisms, such as meridional circulation and shear-induced turbulent diffusion, reduce surface gravity, shortening the recurrence times and lowering burst energies. Rotation also modifies the extent of the nuclear activity during these events and affects the morphology of their light curves, which are distinctly broader for rapidly rotating neutron stars.
Read the full abstract

Earth and Planetary Astrophysics

Diffractive Sail H-Reversal Trajectory: Theoretical Feasibility, Design Strategies, and Applications

Jinkai Zhang, Shuyue Fu, Di Wu et al. (+2 more)

With the growing threat of near-Earth asteroid, planetary defense serves as a vital shield against catastrophic disasters. Kinetic impact utilizing an angular momentum reversal (H-reversal) trajectory of a solar sail is a highly advantageous defense approach. However, traditional reflective sails (RS) are constrained during these maneuvers by attitude-thrust coupling and a degradation of solar radiation pressure utilization at the high cone angles required for transverse acceleration. To enhance impact performance and simplify control, this paper proposes an H-reversal impact scheme utilizing a Sun-facing diffractive sail (SFDS) under a one-stage diffraction angle {\theta}d strategy and a two-stage {\theta}d strategy. The feasible parameter spaces for both strategies were mapped using the hodograph method. Tailored trajectory design methods were established for both strategies based on the feasibility analysis. Apophis impact scenario was considered, and the corresponding trajectories were constructed. Simulations demonstrate that the one-stage {\theta}d SFDS outperforms RS through a 21% increase in the impact velocity and a 35% decrease in the mission duration. Furthermore, the proposed two-stage {\theta}d strategy yields an additional 9km/s gain in impact velocity. By utilizing SFDS H-reversal trajectories, this research establishes an emergency planetary defense framework characterized by rapid response and high kinetic energy.
Read the full abstract

All authors Jinkai Zhang, Shuyue Fu, Di Wu, Lin Cheng, Shengping Gong

Solar and Stellar Astrophysics

A matter of class and flare Flare productivity in solar active regions and power-law constraints on the flare frequency distribution

A.G.M. Pietrow

Solar active regions are the source of virtually all significant space weather events, therefore the relationship between their observable properties and flare production is important to characterize. The flare productivity of solar active regions is analyzed across solar cycles 23–25 as a function of magnetic complexity, sunspot area, and solar-cycle phase. Additionally, the power-law index of the peak flux frequency distribution is estimated. The GOES soft X-ray event reports matched with daily Solar Region Summaries (SRS) are used to create a robust active region catalog. This catalog is supplemented with the 50-year HEK flare catalog and the newly released STIX flare catalog from Solar Orbiter to estimate the power-law index. Magnetically complex active regions ($\beta\gamma$, $\beta\delta$, $\beta\gamma\delta$) produce the majority of M- and X-class flares while comprising only $\sim$13% of all daily active-region observations, showing that larger flares disproportionately occur in larger area sunspots. All three catalogs can be represented with a consistent power-law index of $\alpha = 2.02 \pm 0.01$ for the peak flux frequency distribution. However, a class-by-class analysis of the C/X and M/X flare ratios reveals that the distribution steepens significantly towards higher energies. Fitting this steepening as a lognormal tail and extrapolating two decades beyond the X-class threshold predicts a recurrence time of $370^{+292}_{-159}$~yr for an X100-class (`Carrington-type') superflare, compared to only $\sim$26~yr from a naive single power-law extrapolation. While $\alpha \approx 2$ provides a useful global description of the flare frequency distribution, the steepening area-productivity relation and the divergence between C/X and M/X derived slopes both point to a deficit of the most energetic flares ...
Read the full abstract

Astrophysics of Galaxies

The two faces of tides: gravitational instability during galaxy mergers

Trisha Khan and Ayush Hazarika

Gravitational instability is a fundamental mechanism driving collapse of interstellar gas, yet in dynamically evolving environments such as galaxy mergers, external tidal fields can significantly alter the conditions for collapse. In this work, we develop an analytical framework to investigate how the tidal field of a companion galaxy modifies the classical Jeans instability by incorporating its anisotropic and time-dependent nature into the dispersion relation. We find that the tidal field introduces a critical angle between the cloud's position vector and the merger axis, $\theta_c \approx 54.7^\circ$, separating disruptive and compressive regimes of the radial tidal component. Disruptive tides suppress instability by increasing the characteristic length scale and restricting the range of unstable modes, whereas compressive tides enhance collapse by extending the unstable spectrum and increasing the growth rate of perturbations. The impact of tidal fields depends sensitively on gas density, being significant in diffuse media but negligible in dense molecular environments where the classical Jeans limit is recovered. All tidal effects peak near pericentric passage due to the strong dependence on galaxy separation. Since the free-fall time of diffuse gas is comparable to the duration of the close passage, tidally assisted collapse in the diffuse medium lags pericentre by roughly a free-fall time, whereas dense gas responds essentially instantaneously. These results demonstrate that companion-induced tidal fields play a key role in regulating the scale and efficiency of gravitational instability of diffuse interstellar gas in galaxy mergers. The code underlying this work is publicly available.
Read the full abstract

Astrophysics of Galaxies

Detection and Properties of Lyman Break Galaxies at $1.6 \leq z \leq 3.0$ in GOODS-North

Bibhuprasad Mishra, Kanak Saha, Divya Pandey et al. (+1 more)

Lyman Break Galaxies (LBGs) are actively star-forming galaxies identified through their characteristic rest-frame ultraviolet spectral break, making them powerful probes of galaxy evolution across cosmic time. We present a search for LBGs at redshifts $1.6 \leq z \leq 3.0$ in the GOODS-North field using the dropout technique combined with color selection from the 3D-HST data. We utilize two selection criteria to identify LBG candidates at $z \sim 2.1$ and $z \sim 2.7$ via F275W- and F336W-dropouts, yielding 192 and 135 newly identified LBG candidates in the redshift ranges $1.6 \leq z \leq 2.3$ and $2.3 < z \leq 3.0$, respectively. We estimate the physical properties of the LBG candidates, including stellar age, stellar mass, and star formation rate (SFR), using spectral energy distribution (SED) fitting. Morphological analysis shows that the majority of galaxies in our sample exhibit disc-like structures. Overall, the results indicate that these LBGs are low- to intermediate-mass compact galaxies with effective half-light radii of approximately 3.5 kpc.
Read the full abstract

All authors Bibhuprasad Mishra, Kanak Saha, Divya Pandey, Ananta C. pradhan

Earth and Planetary Astrophysics

A Formation-Stage Bottleneck for Exomoons around Close-in Rocky Planets

Rongxi Bi, Hongping Deng, Christian Reinhardt et al. (+2 more)

Massive moons around rocky exoplanets are expected outcomes of giant impacts, yet no exomoon has been securely confirmed. We address this problem using meshless finite-mass simulations of giant impacts between differentiated rocky planets that include stellar tidal and Coriolis forces in a local co-rotating frame for orbital periods of 1–300 days, and compare these simulations with otherwise identical collisions in isolation. We find that stellar perturbations impose a severe formation-stage bottleneck on moon-forming disks. Ultra-short-period impacts leave essentially no surviving circumplanetary disk, whereas 10-day systems retain only strongly depleted, radially truncated, and dynamically compact disks. High impact velocities, expected for close-in planets, are devastating for disk generation, while retrograde impacts can slightly compensate for disk mass depletion. These results show that stellar perturbations can suppress exomoon formation around close-in rocky planets, reshaping expectations for the demographics of exomoons.
Read the full abstract

All authors Rongxi Bi, Hongping Deng, Christian Reinhardt, Shangfei Liu, Yun Liu

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Relativistic Signatures of Dark Matter Equations of State in Static Spherically Symmetric Spacetimes

Akash Yadav, Sudhava Yadav and K.K. Venkataratnam

We study how three physically motivated dark matter equations of state alter the spacetime geometry of static, spherically symmetric black holes in General Relativity. The models considered are anisotropic perfect fluid dark matter (PFDM), isotropic constant-$\omega$ dark matter, and Bose-Einstein condensate (BEC) dark matter with a polytropic equation of state (EoS). For each model, we derive the Einstein field equations and solve for the metric function analytically in the PFDM and constant-$\omega$ cases, and numerically via the Tolman-Oppenheimer-Volkoff equations for BEC dark matter. We then compute the key strong gravity observables: event horizon radius, photon sphere radius, black hole shadow radius, innermost stable circular orbit (ISCO), and circular orbital velocity profiles. The shadow radii obtained for each model are compared against the Event Horizon Telescope constraints to place bounds on the dark matter parameters. Physical viability is assessed through the null, weak, dominant, and strong energy conditions, along with causality requirements on the sound speed. Our results show that PFDM produces near Schwarzschild geometry with mild anisotropic corrections, the constant-$\omega$ model is strongly restricted by causality to $0 \leq \omega \leq 1$, and BEC dark matter generates smooth, bounded deviations governed by the bosonic self-interaction parameter K. Taken together, these findings show that strong gravity observables can serve as practical tools for distinguishing between competing dark matter models through their geometric imprints on black hole space times.
Read the full abstract

Instrumentation and Methods for Astrophysics

FIRST-PL: Commissioning the first visible photonic lantern spectrograph for sub-diffraction-limit astronomy on Subaru/SCExAO

Sebastien Vievard, Elsa Huby, Sylvestre Lacour et al. (+18 more)

FIRST-PL (Fibered Imager foR a Single Telescope - Photonic Lantern) is a newly commissioned visible-light instrument on Subaru/SCExAO achieving spectroscopy below the diffraction limit. The instrument uses a Photonic Lantern (PL)-converting multimode fiber into 19 single-mode outputs-feeding a mid-resolution spectrograph (R 3000, 630-790 nm). On-sky performance demonstrates 40% injection efficiency at 680 nm (Strehl 30%) and 12x throughput improvement over single-mode fibers. Three operational modes enable spectro-astrometry (50 microarcseconds precision demonstrated on beta-CMi), image reconstruction, and high-contrast imaging. FIRST-PL represents a significant advancement in high-throughput photonic instrumentation.
Read the full abstract

All authors Sebastien Vievard, Elsa Huby, Sylvestre Lacour, Olivier Guyon, Manon Lallement, Mathias Nowak, Yoo Jung Kim, Aidan Walk, Jehanne Sarrazin, Sergio Leon-Saval, Chris Betters, Julien. Lozi, Miles Lucas, Vincent Deo, Nemanja Jovanovic, Michael Fitzgerald, Barnaby Norris, Thayne Currie, Garima Singh, Sandrine Juillard, Guy Perrin

Astrophysics of Galaxies

FAST Ultra-Deep Survey: the baryonic Tully-Fisher relation in FUDS0 field

Hongwei Xi, Lister Staveley-Smith, Bo Peng et al. (+4 more)

The Baryonic Tully-Fisher relation (BTFR) is one of the tightest scaling relations for disk galaxies in the local Universe, and therefore is an important tool for studying the fomation and evolution of galaxies. However, the evolution of the BTFR over cosmic time is poorly understood due to the limited sample of HI galaxies beyond the local Universe, limitations of optically-derived rotation curves, and selection effects. In this work, we explore the BTFR at redshifts up to $z=0.42$ from galaxies detected in the pilot FAST Ultra-Deep Survey (FUDS) field, FUDS0. As found in previous work, we identify two components in the plane of baryonic mass versus rotational velocity, $C_{\rm BTFR}$ (tight) and $C_{\rm Outlier}$ (dispersed). A Gaussian mixture model is employed to recover the BTFR, yielding the best fit parameters for the slope $k=3.32_{-0.11}^{+0.12}$, zero point $b=10.07_{-0.03}^{+0.03}$, and intrinsic scatter $\sigma_{\rm BTFR}=0.036_{-0.009}^{+0.010}$. A random forest classifier is used to investigate the origin of the outlier component. We find that low signal significance and inaccurate inclinations are the key factors that contribute to the outlier population, indicating that observational effects are the dominant origin. Evolutionary trends are examined in three different redshift bins. Both the slope and zero point show consistency within 1-$\sigma$ uncertainty in the two low redshift bins, indicating no significant evolution. The indirectly inferred BTFR parameters from the $C_{\rm Outlier}$ component in the highest redshift bin aligns with the conclusion. The ongoing full FUDS survey will provide a larger sample to enable more accurate constraints on BTFR evolution.
Read the full abstract

All authors Hongwei Xi, Lister Staveley-Smith, Bo Peng, Bi-Qing For, Bin Liu, Dejian Ding, Jianbin Li

Astrophysics of Galaxies

Cold Dark Matter and Self-Interacting Dark Matter Interpretations of Cloud-9

Morgan Ohana, Xingyu Zhang and Hai-Bo Yu

Recently, the Five-hundred-meter Aperture Spherical Telescope discovered a gas-rich hydrogen cloud near M94 in the $21\,{\rm cm}$ band. Lacking an optical counterpart, this object, dubbed Cloud-9, has been identified as a compelling Reionization Limited Hi Cloud (RELHIC). RELHICs provide exceptionally clean laboratories for probing dark matter, free from the baryonic complexities associated with star formation and feedback. We show that the observed hydrogen column density profile of Cloud-9 is consistent with a gas cloud embedded in either a cuspy halo predicted by the standard cold dark matter (CDM) model or a cored halo produced by self-interacting dark matter (SIDM). In both cases, the halo must have an unusually diffuse central density. The best-fitting CDM halo lies around $7\sigma$ below the cosmological concentration–mass relation, whereas SIDM core-forming halos reduce the tension to only around $3\sigma$. We further identify Cloud-9 analogs in the Concerto suite of cosmological zoom-in simulations with velocity-dependent SIDM, demonstrating that RELHICs provide a promising new probe of dark matter self-interactions.
Read the full abstract

Cosmology and Nongalactic Astrophysics

Revisiting the equation of state of dark energy from DESI BAO with SNe Ia and CMB

Jie Zheng, Da-Chun Qiang, Zhi-Qiang You et al. (+1 more)

The Dark Energy Spectroscopic Instrument (DESI) measurements of baryon acoustic oscillations (BAO) have recently shown a mild preference for dynamical dark energy over the standard $\rm \Lambda$CDM model. In this paper, we analyze the $w_0w_a$CDM model using DESI BAO DR2, Pantheon+ SNe Ia, and Planck 2018 CMB distance prior data. To examine how different parts of the data affect the apparent deviation from $\rm \Lambda$CDM, we adopt two complementary redshift-cut strategies, dividing the dataset into $z<z_{\rm cut}$ and $z>z_{\rm cut}$ subsamples. We find that the most noticeable shifts occur when BAO and SNe Ia data in the redshift range $z\sim0.4$–$0.8$ are included, reaching a significance of about $\sim2\sigma$. Within this framework, the inclusion of higher-redshift measurements progressively weakens this deviation and brings the constraints closer to the $\rm \Lambda$CDM expectation. Moreover, the information criteria show no statistically significant preference between the $w_0w_a$CDM and $\rm \Lambda$CDM models, while the Bayesian information criterion consistently favors the $\rm \Lambda$CDM model. In addition, a parameter-shift consistency test reveals no statistically significant tension between complementary redshift subsamples. Within the DESI BAO DR2, Pantheon+, and CMB distance prior framework adopted here, these results do not provide statistically robust evidence favoring the $w_0w_a$CDM model over $\rm \Lambda$CDM. They instead indicate that the apparent parameter shifts under different redshift cuts may be affected by statistical fluctuations and by the limited precision and number of datapoints in the current subsamples. Our analysis provides a complementary redshift-dependent diagnostic for assessing how the inferred cosmological constraints vary under different redshift selections.
Read the full abstract

All authors Jie Zheng, Da-Chun Qiang, Zhi-Qiang You, Darshan Kumar

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Corrections to Hawking radiation from asteroid-mass primordial black holes: analytic and numerical evaluation of the stochastic charge effect

Gabriel Vasquez, Bowen Chen, Cara Nel et al. (+3 more)

Hawking radiation sets stringent constraints on Primordial Black Holes (PBHs) as a dark matter candidate in the $M\sim 10^{16}$ g regime based on the evaporation products produced by the black hole, motivating the need to rigorously model the photon, electron, and positron emission spectra. This manuscript is the second in a series of two papers (see Vasquez et al. [Phys. Rev. D, 112:063002 (2025)] for the first paper in the series) with the goal of proving the stochastic emission of electrons and positrons, known as the "stochastic charge effect" and first predicted by Page [Phys. Rev. D, 16:2402 (1977)] using semi-classical arguments, arises from quantum electrodynamics (QED) on a Schwarzschild spacetime. We derive the corrections to the $e^\pm$ from the relevant term in the Hamiltonian (the long-range monopole: $H_{\rm int,0L}$) to first order in the fine structure constant ($\alpha$), and show that the semi-classical terms are also present in the QED calculation. We also highlight which terms in our analysis only appear within our quantum mechanical approach and cannot be explained otherwise. We find that due to some cancellation of terms, over the range of $2.2\times 10^{16}$ - $1.7\times 10^{17}$ g, the net correction to the $e^\pm$ emission rate is less than 2%, versus the suppression of up to 5% previously found by semi-classical arguments.
Read the full abstract

All authors Gabriel Vasquez, Bowen Chen, Cara Nel, Emily Koivu, Makana Silva, Christopher M. Hirata

Instrumentation and Methods for Astrophysics

Life 2.0: A Scalable Distributed Space-Telescope Array for Biosignature Spectroscopy

Jian Ge, Zhangqi Dang, Ziru Zhang et al. (+15 more)

Answering the question "Are we alone?" requires atmospheric spectroscopy of nearby terrestrial planets. For an Earth–Sun analog, even the strongest transmission signals are expected to be of order 1 part per million (ppm). Unlike short-period planets, Earth 2.0 planets transit only about once per year, so single-transit sensitivity, rather than stacking repeated observations, is the fundamental design driver. Life 2.0 is a scalable space-mission concept linking Earth 2.0 candidates discovered by PLATO and the Earth 2.0 (ET) mission with atmospheric characterization and biosignature assessment. The baseline architecture comprises 900 one-meter space telescopes, each equipped with a high-throughput Waveguide Integrated Miniature Spectrograph and an ultra-low-read-noise CMOS detector. After independent calibration, spectra acquired simultaneously during a transit are combined, providing the photon-collecting capability of an approximately 30-m aperture at the selected spectral resolution while retaining a modular architecture. The baseline 0.2–1.05 $\mu$m range covers O$_3$, O$_2$, H$_2$O, Rayleigh scattering, and other diagnostics, with extension into the infrared as detector technologies mature. Prototype Waveguide Spectral Lens devices have demonstrated 40–66% throughput at resolving powers from $R \sim 200$ to $R \sim 20{,}000$. Lightweight silicon-carbide mirrors and sub-electron-noise CMOS detectors support replicated production. Life 2.0 must address detector systematics, instrument stability, and stellar variability; rather than assuming these limitations disappear, it builds on calibration, detector-characterization, and data-analysis techniques advanced during the JWST era. The concept offers a scalable alternative to a monolithic 30-m-class space telescope and a staged pathway toward biosignature spectroscopy of nearby Earth-like planets.
Read the full abstract

All authors Jian Ge, Zhangqi Dang, Ziru Zhang, Chenxu Gao, Shijie Ke, Ziyang Zhang, Rong Shu, Wen Chen, Jie Yin, Yunzhou Zhu, Leiming Lei, Zhongming Chen, Jiancheng Ji, Xiangsen Tian, Jun Yang, Xinyi Song, Rafael Luque, Enric Palle

Instrumentation and Methods for Astrophysics

He'e-Lab: A modular testbed for astrophotonics and wavefront sensing development

Sebastien Vievard, Christopher Hamner, Nour Skaf et al. (+14 more)

Advanced astronomical instrumentation requires accessible, reconfigurable platforms to validate novel technologies and algorithms before on-sky deployment. We present the design, architecture, and alignment validation of the Hawaii Experimental Engineering Lab (He'e-Lab), a state-of-the-art modular testbed dedicated to two complementary research tracks: (A) the integration and characterization of astrophotonics components within a real-time computing loop, and (B) the development of advanced wavefront sensing and control (WFS&C) algorithms. The testbed features a broadband supercontinuum source (500 nm to 2 microns), a high-order 1k-actuator Boston Micromachines deformable mirror, and a 37-segment hexagonal mirror assembly providing piston-tip-tilt control to emulate segmented apertures like Keck and JWST. Downstream capabilities include a HASO 126 Shack-Hartmann sensor, a real-time computing environment driven by the CACAO package, and a modular injection platform coupled to a visible-wavelength spectrograph (R3, 000). We report on the successful system alignment and outline the roadmap for upcoming adaptive optics and photonic device validation frameworks.
Read the full abstract

All authors Sebastien Vievard, Christopher Hamner, Nour Skaf, Dylan Hively, Michael Bottom, Mark Chun, Christoph Baranec, Olivier Guyon, Julien Lozi, Aidan Walk, Josh Corn, Branden Allen, Elsa Huby, Sylvestre Lacour, Guillermo Martin, Manon Lallement, Vincent Deo

Solar and Stellar Astrophysics

Doppler-shifted Signatures in the Chromospheric Line Profiles of II Pegasi

Cao Dongtao and Gu shenghong

Stellar flares are frequently accompanied by prominence eruptions, coronal mass ejections (CMEs), and other forms of plasma motion. Based on the long-term high-resolution spectroscopic monitoring data set of the RS CVn-type star II Pegasi (II Peg), we search for stellar prominence eruptions and potential CMEs by investigating asymmetric signatures in the H$_{\alpha}$ and H$_{\beta}$ line profiles during the flare events. We observed seven optical flares with asymmetric spectral profiles, releasing low limit energies of $10^{33}$–$10^{34}$ erg in the H$_{\alpha}$ line. Five of these flares were associated with six potential CMEs, identified through the Doppler-shifted emission signatures in the chromospheric line profiles, particularly the H$_{\alpha}$ line. The mass estimates for the CME candidates range from $10^{19}$ to $10^{20}$ g, while the kinetic energies are calculated to be around $10^{33}$–$10^{34}$ erg. The most massive CME candidate was simultaneously recorded in the H$_{\alpha}$, H$_{\beta}$, and He I D$_{3}$ lines. For II Peg, the possible flare-CME association rate is about 30%. There were also some redshifted excess absorption signatures in the H$_{\alpha}$ line profiles. These signatures could not only be observed in the flaring spectra but also in the spectra without flare, which could be interpreted as features resulting from flare-driven coronal rain and quiescent rain, respectively.
Read the full abstract

High Energy Astrophysical Phenomena

A Real-Time Jet Laboratory in Swift J1727.8-1613

Callan M. Wood, James C. A. Miller-Jones, Arash Bahramian et al. (+16 more)

We present the results of our intensive VLBI campaign on the black-hole low-mass X-ray binary (LMXB) Swift J1727.8-1613 during its 2023-2024 outburst. We observed the repeated quenching and re establishment of the highly-extended continuous jet during several transitions between hard-intermediate and soft-intermediate states, and the repeated ejection of transient jets. Using time-dependent visibility model fitting, we tracked the motion of nine discrete jet knots, obtaining some of the most precise measurements of transient jet proper motions and ejection dates in an LMXB. These ejecta were only detectable for a short time with VLBI, and some showed rapid intra-observation flux density variability that was not captured in image reconstructions. For the first time, we use time-dependent visibility modelling to fit a piecewise model for the jet knot flux densities, allowing us to create complex, non-parametric light curves of their intra-observation variability. We observed the launching of multiple ejecta across several state transitions, however, we could not identify a consistent signature of jet ejection in the available X-ray intensity or hardness data. We constrained the intrinsic speeds and bulk Lorentz factors of the jet knots, finding that Swift J1727.8-1613 launched both mildly relativistic and highly relativistic ejecta throughout its outburst. We used their proper motions to constrain a posterior distribution for the maximum inclination angle of the jet axis, which had 50th, 84th, and 99th percentiles of 40{\deg}, 50{\deg}, and 66{\deg}, respectively. These unique observations of the repeated ejection of transient jets by a single LMXB reveal that fixed parameters such as black-hole mass, black-hole spin, and spin-orbit misalignment do not uniquely determine the varying properties of transient jets, particularly their speeds and Lorentz factors.
Read the full abstract

All authors Callan M. Wood, James C. A. Miller-Jones, Arash Bahramian, Steven J. Tingay, Sara E. Motta, Hongmin Cao, Thomas D. Russell, Francesco Carotenuto, Pikky Atri, Diego Altamirano, Alexandra J. Tetarenko, Rob Fender, Elmar Körding, Dipankar Maitra, Sera Markoff, David M. Russell, Gregory R. Sivakoff, Roberto Soria, Valeriu Tudose

Solar and Stellar Astrophysics

Further Investigation on Chromospheric Activity Patterns of the RS Canum Venaticorum Star V711 Tauri

Cao Dongtao and Gu Shenghong

We present new long-term spectroscopic observations of the very active RS Canum Venaticorum (RS CVn) star V711 Tauri (V711 Tau), obtained during several observing runs from 2005 to 2021. By means of spectral subtraction technique, several optical chromospheric activity indicators $\mbox{Ca {\sc ii}}$ infrared triplet, H$_{\alpha}$, $\mbox{Na {\sc i}}$ D$_{1}$, D$_{2}$ doublet, $\mbox{He {\sc i}}$ D$_{3}$, and H$_{\beta}$ lines, are analyzed. V711 Tau shows strong excess emission in the chromospheric activity lines, and the emission is mainly associated with the K1 IV primary component. The G5 V secondary component also shows weak emission features. There are four optical flare events during our observations, characterized by the $\mbox{He {\sc i}}$ D$_{3}$ line emission features and stronger emission in other activity lines, which have similar order of magnitude as the strong flares of other active RS CVn-type stars. We separate our long-term observations to twelve observing groups, and find that V711 Tau has two active longitudes around phases 0.25 and 0.75 to dominate the activity in most of time. The chromospheric activity level shows a long-term variation, indicating possible chromospheric activity cycle. Moreover, a close spatial connection between photospheric spots and chromospheric active regions in short and long timescale is found for V711 Tau.
Read the full abstract

Tuesday 4 August

High Energy Astrophysical Phenomena

Multimessenger Constraints on the Central Engine in SN 2023ixf: Neutron Star or Black Hole?

Maryam Aghaei Abchouyeh, Maurice H.P.M. van Putten and Massimo Della Valle

The physical trigger of core-collapse supernova (CC-SNe) is a central theme in modern surveys of the transient Universe. A multi-messenger approach may provide a unique window to CC-SNe produced by a newly born neutron star (NS) or black hole (BH). Here we apply joint electromagnetic-gravitational wave (EM-GW) analysis to the nearby event SN 2023ixf using a model-independent broadband search with a GW-energy detection threshold of a few times $10^{-5} M_\odot c^2$ for chirps and $10^{-2}$ $M_\odot c^2$ for noise-like emission below 1\,kHz. No joint LIGO Hanford-Livingston (H1-L1) signal associated with SN 2023ixf is observed over a 2.5 day window proceeding the first discovery. Together with EM photometric-spectroscopic data, we interpret this null result to indicate the absence of BH formation, in part by mass-scaling of the BH powering GW170817B following GW170817. This multi-messenger outcome supports, hereby, scenarios consistent with NS formation, consistent with a progenitor mass likely below $\sim 20 M_\odot$ estimated by EM interpretations.
Read the full abstract

Instrumentation and Methods for Astrophysics · Cross-listed from physics.data-an

Learned proposals in trans-dimensional inference are optimal at equilibrium, not during assembly

Argyro Sasli, Nikolaos Karnesis, Minas Karamanis et al. (+5 more)

Inferring the dimension of a model - the number of components needed to explain data - jointly with the parameters is a pervasive problem, from counting sources in an image to mixture modeling, and reversible-jump Markov chain Monte Carlo solves it exactly but mixes slowly. Learned proposals are well established at fixed dimension, but whether they can accelerate the dimension-changing moves themselves has remained largely untested. We show that the answer has a structural origin: the optimal proposal for the dimension-changing birth move is a different object in different phases of the run. While the fit is being assembled it must match the current residual - a state-dependent quantity no state-independent network can represent - but at equilibrium it degenerates to the posterior's single-component marginal, which is exactly the distribution an adaptive normalizing flow learns from the sampler's own history. A learned state-independent birth proposal is therefore useless in one phase and optimal in the other. Controlled experiments confirm the attribution: applied with an exact Metropolis–Hastings correction that leaves the target invariant for any network, the learned births leave acceptance rates unchanged yet accelerate model-order mixing - in a ten-seed benchmark they meet a pre-specified stopping rule in six of ten runs, typically several times sooner, where a strong hand-tuned baseline meets it in one (one-sided p=0.03) - and an isolation experiment shows the same flow deployed within-model buys nothing. Making no domain-specific assumptions, the same sampler counts sources in a noisy image and reconstructs signals across scientific domains, including gravitational waves from ground- and space-based detectors and a scalp EEG recording. We release the method as HyperWave, an open-source package.
Read the full abstract

All authors Argyro Sasli, Nikolaos Karnesis, Minas Karamanis, Michael L. Katz, Dimitrios Kourtesis, Michael W. Coughlin, Vuk Mandic, Nikolaos Stergioulas

Instrumentation and Methods for Astrophysics · Cross-listed from cs.CV

Real-time physics inversion for retrieval of sub-pixel wildfire temperatures from VSWIR imaging spectroscopy

William R. Keely, Philip G. Brodrick, Katherine Mistick et al. (+3 more)

In this work, we present a wildfire temperature retrieval framework for VSWIR imaging spectroscopy data, employed on data from NASA's Airborne Visible Infrared Imaging Spectrometer (AVIRIS-3). The retrieval framework utilizes a full-physics approach in which a forward model is employed to resolve both solar and emitted radiance derived from a temperature distribution and utilizes the full spectral range in the residual fit. To optimize the forward model retrieval, we use state-of-the-art nonlinear least squares methods implemented for fast convergence on the on-board GPU, allowing for estimation of effective fire temperature within flight cadence. We verify the forward model assumptions on simulated spectra with an injected thermal signature and find good agreement with an RMSE of $41.8$ Kelvin (K). We apply the retrieval over the full 2025 FireSense AVIRIS-3 campaign, totaling 168 overflights with probable active fire spectra, and demonstrate a residual radiance fit of $\leq 10\%$ across bands in the short-wave infrared (SWIR). Lastly, we verify the applicability of the retrieved posterior fire temperature parameters to generalize to space-borne imaging spectrometers such as EMIT, by retrieving at coarsened spatial resolution. We find that the posterior distribution exhibits good coverage of the underlying sub-pixel temperature range with an absolute error of $30$ K across quantiles and a mean absolute error of $27.16$ K between spatial resolutions.
Read the full abstract

All authors William R. Keely, Philip G. Brodrick, Katherine Mistick, Adam Chlus, Robert O. Green, Philip E. Dennison