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Physics Astrophysics

astro-ph Watch Astrophysics

Monday 12 January

Astrophysics of Galaxies

A survey of molecular clouds in the Galactic center's outflow

Enrico M. Di Teodoro, Mark Heyer, Mark R. Krumholz et al. (+8 more)

The nucleus of the Milky Way is known to drive a large-scale, multiphase galactic outflow, with gas phases ranging from the hot highly-ionized to the cold molecular component. In this work, we present the first systematic search for molecules in the Milky Way wind. We use the Atacama Pathfinder EXperiment (APEX) to observe the 12CO(2-1) emission line in 19 fields centered on previously known high-velocity atomic hydrogen (HI) clouds associated with the outflow. Over 200 CO clumps are detected within 16 different HI clouds. These clumps have typical radii of 1 - 3 parsec, high velocity dispersions of 1 - 6 km/s and molecular gas masses ranging from a few to several hundred solar masses. Molecular clumps in the wind sit on the low-mass end of the mass - size relation of regular molecular clouds, but are far displaced from the mass (or size) - linewidth relation, being generally more turbulent and showing high internal pressures. Nearly 90% of the clumps are gravitationally unbound with virial parameters >> 10 - 100, indicating that these structures are either being disrupted or they must be confined by external pressure from the surrounding hot medium. While the observed properties of CO clumps do not seem to evolve clearly with latitude, we find that molecular gas is not detected in any of the 6 HI clouds with projected distances over 1 kpc from the Galactic Center, suggesting the existence of a maximum timescale of ~ 3 Myr for the dissociation of molecular gas within the wind. Overall, current observations in the Galactic center support a scenario in which a hot wind entrains cold gas clouds from the disk, driving their progressive transformation from molecular to atomic and ultimately ionized gas through stripping, turbulence, and dissociation.
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All authors Enrico M. Di Teodoro, Mark Heyer, Mark R. Krumholz, Lucia Armillotta, Felix J. Lockman, Andrea Afruni, Michael P. Busch, N. M. McClure-Griffiths, Karlie A. Noon, Nicolas Peschken, Qingzheng Yu

Astrophysics of Galaxies

Intermediate-mass black hole incubators. Gas accretion onto stellar black hole clusters in galactic central molecular zones

Jaroslav Haas, Pavel Kroupa and Sergij Mazurenko

The stellar dynamical evolution of massive star clusters formed during starburst periods leads to the segregation of $\gtrsim10^4 M_\odot$ stellar-mass black hole sub-clusters in their centres. In gas-rich environments, such as galactic central molecular zones, these black hole clusters are likely to accrete large amounts of the gas from their surroundings, which in turn affects their internal dynamics. In this Letter we estimated the corresponding accretion rate onto the black hole cluster and its radiative feedback. We assessed whether such an accretion flow can lead to the collapse of the black hole cluster into an intermediate-mass black hole. The estimates were obtained analytically, considering the astrophysical conditions and star formation history reported for the central molecular zone of our Galaxy. We find that a stellar black hole cluster with mass $\gtrsim10^4 M_\odot$ located in the twisted ring of molecular clouds with radius $\approx100$ pc that is observed in the central molecular zone of our Galaxy can accrete about the same mass in gas on a timescale of a few million years. We suggest that this is sufficient for its subsequent collapse into an intermediate-mass black hole. Based on an estimate of the dynamical friction inspiral time, we further argue that the locations of the intermediate-mass black hole candidates recently observed in the central molecular zone are compatible with their formation therein during the last starburst period reported to have occurred $\approx1$ Gyr ago.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

The Scalar Mach-Sciama Theory of Gravitation

Velásquez-Toribio and A. M

We formulate a scalar realization of Sciama's Machian programme within the general Bergmann-Wagoner class of scalar–tensor gravity. Starting from a universally conformally coupled matter sector, we rewrite the field equations in terms of the invariant set $\{{\cal I}_1,{\cal I}_2,{\cal I}_3,\hat g_{\mu\nu}\}$, so that Machian requirements can be stated independently of conformal frame. Sciama's causal postulate is implemented not by modifying the local dynamics, but as a selection rule on the solution space of the invariant scalar equation: the admissible configuration is the retarded response to the matter distribution in the causal past, with any source-free contribution removed. In a spatially flat FLRW universe, and in the light, slowly varying regime, the prescription reduces to an explicit temporal kernel that links the background scalar evolution to the matter content within the Hubble region, reproducing the expected Machian scaling in an expanding background. Universal coupling to a single physical metric implies that structureless test bodies share the same acceleration in a given external configuration, so that the Eötvs parameter vanishes at leading order. Nonuniversal effects can arise only when gravitational binding energy contributes appreciably to the total mass, as in strongly self-gravitating objects. Thus, the theory implements a causal Machian determination of the cosmological inertial scale while remaining consistent with standard weak-field tests.
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Cosmology and Nongalactic Astrophysics

Axion misalignment as a synchronization phenomenon

Veronica Sanz

We propose a dynamical reinterpretation of axion misalignment as an emergent collective phenomenon. Drawing an explicit parallel between axion field dynamics and synchronization in coupled oscillator systems, we show that a macroscopic axion phase can arise dynamically from initially incoherent configurations through gradient-driven ordering in an expanding Universe. In this framework, the misalignment angle is not a fundamental initial condition but a collective variable that becomes well defined only once phase coherence develops. Using a three-dimensional lattice study with full second-order dynamics, we show that this collective phase is selected prior to the onset of axion oscillations in the regimes studied, providing dynamical support for the standard misalignment picture. This perspective offers a new way of organizing axion initial-condition sensitivity and reframes small-angle assumptions in terms of the efficiency of phase ordering in the early Universe.
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Cosmology and Nongalactic Astrophysics

Cosmoglobe DR2. IV. Modelling starlight in DIRBE with Gaia and WISE

M. Galloway, E. Gjerløw, M. San et al. (+20 more)

We present a model of starlight emission in the Diffuse Infrared Background Explorer (DIRBE) data between 1.25 and 25$\,\mu$m based on Gaia and WISE measurements. We include two classes of compact objects, namely bright stars with individual spectral energy densities (SEDs) measured by Gaia, and a combined diffuse background of dim point source emission. Of the 424\ 829 bright sources that we fit, the number of stars with a flux density detected by WISE at Galactic latitudes $|b|>20^{\circ}$ at more than $5\,\sigma$ is 94\,680, for an average of 1.36~stars per DIRBE beam area. For each star, we adopt physical parameters ($T_{\mathrm{eff}}$, $\log g$, and [M/H]) from Gaia; use these to identify a best-fit effective SED with the PHOENIX stellar model library; convolve with the respective DIRBE bandpass; and fit an overall free amplitude per star within the Bayesian end-to-end Cosmoglobe DR2 framework. The contributions from faint sources are accounted for by coadding all 710\ 825\ 587 WISE sources not included as bright stars, and fit one single overall amplitude per DIRBE band. Based on this model we find that total star emission accounts for 91\,% of the observed flux density at 2.2\,$\mu$m; 54\,% at 4.9$\,\mu$m; and 1\,% at 25\,$\mu$m. As shown in companion papers, this new model is sufficiently accurate to support high-precision measurements of both the Cosmic Infrared Background monopole and zodiacal light emission in the three highest DIRBE frequencies.
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All authors M. Galloway, E. Gjerløw, M. San, R. M. Sullivan, D. J. Watts, R. Aurvik, A. Basyrov, L. A. Bianchi, A. Bonato, M. Brilenkov, H. K. Eriksen, U. Fuskeland, K. A. Glasscock, L. T. Hergt, D. Herman, J. G. S. Lunde, A. I. Silva Martins, D. Sponseller, N.-O. Stutzer, H. Thommesen, V. Vikenes, I. K. Wehus, L. Zapelli

Cosmology and Nongalactic Astrophysics

Cosmoglobe DR2. VII. Towards a concordance model of large-scale thermal dust emission for microwave and infrared frequencies

E. Gjerløw, R. M. Sullivan, R. Aurvik et al. (+20 more)

We fit a four-component thermal dust model to COBE-DIRBE data between 3.5 and 240 micron within the global Bayesian end-to-end Cosmoglobe DR2 reanalysis. Following a companion analysis of Planck HFI, the four components of this model correspond to "hot dust", "cold dust", "nearby dust", and "Halpha correlated dust", respectively, and each component is modelled in terms of a fixed spatial template and a spatially isotropic spectral energy density (SED) defined by an overall free amplitude for each DIRBE channel. Except for the cold dust amplitude, which is only robustly detected in the 240 micron channel, we measure statistically significant template amplitudes for all components in all DIRBE channels between 12 and 240 micron. In the 3.5 and 4.9 micron channels, only the hot component is detected, while the 1.25 and 2.2 micron channels are too dominated by starlight emission to allow robust dust detections. The total number of DIRBE-specific degrees of freedom in this model is 25. Despite this low dimensionality, the resulting total SED agrees well with recent astrodust predictions. At both low and high frequencies, more than 95 % of the frequency map variance is captured by the model, while at 60 and 100 micron about 70 % of the signal variance is successfully accounted for. The hot dust component, which in a companion paper has been found to correlate strongly with C ii emission, has the highest absolute amplitude in all DIRBE frequency channels; in particular, at 3.5 micron, which is known to be dominated by polycyclic aromatic hydrocarbon emission, this component accounts for at least 80 % of the total signal. This analysis represents an important step towards establishing a joint concordance model of thermal dust emission applicable to both the microwave and infrared regimes.
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All authors E. Gjerløw, R. M. Sullivan, R. Aurvik, A. Basyrov, L. A. Bianchi, A. Bonato, M. Brilenkov, H. K. Eriksen, U. Fuskeland, M. Galloway, K. A. Glasscock, L. T. Hergt, D. Herman, J. G. S. Lunde, M. San, A. I. Silva Martins, D. Sponseller, N.-O. Stutzer, H. Thommesen, V. Vikenes, D. J. Watts, I. K. Wehus, L. Zapelli

Cosmology and Nongalactic Astrophysics

Cosmoglobe DR2. V. Spatial correlations between thermal dust and ionized carbon emission in Planck HFI and COBE-DIRBE

E. Gjerløw, R. M. Sullivan, R. Aurvik et al. (+20 more)

We fit five tracers of thermal dust emission to ten Planck HFI and COBE-DIRBE frequency maps between 353 GHz and 25 THz, aiming to map the relative importance of each physical host environment as a function of frequency and position on the sky. Four of these correspond to classic thermal dust tracers, namely H i (HI4PI), CO (Dame et al. 2001a), H{\alpha} (WHAM, Haffner et al. (2003a, 2016)), and dust extinction (Gaia; Edenhofer et al. 2024), while the fifth is ionized carbon (C ii) emission as observed by COBE- FIRAS. We jointly fit these five templates to each frequency channel through standard multi-variate linear regression. At frequencies higher than 1 THz, we find that the dominant tracer is in fact C ii, and above 10 THz this component accounts for almost the entire fitted signal; at frequencies below 1 THz, its importance is second only to H i. We further find that all five components are well described by a modified blackbody spectral energy density (SED) up to some component-dependent maximum frequency ranging between 1 and 5 THz. In this interpretation, the C ii-correlated component is the hottest among all five, with an effective temperature of about 25 K. The H{\alpha} component has a temperature of 18 K, and, unlike the other four, is observed in absorption rather than emission. Despite the simplicity of this model, which relies only on external templates coupled to spatially isotropic SEDs, we find that it captures 98 % of the full signal root mean squared (RMS) below 1 THz. This high efficiency suggests that spatial variations in the thermal dust SED, as for instance reported by Planck and other experiments, may be more economically modelled on large angular scales in terms of a spatial mixing of individually isotropic physical components.
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All authors E. Gjerløw, R. M. Sullivan, R. Aurvik, A. Basyrov, L. A. Bianchi, A. Bonato, M. Brilenkov, H. K. Eriksen, U. Fuskeland, M. Galloway, K. A. Glasscock, L. T. Hergt, D. Herman, J. G. S. Lunde, M. San, A. I. Silva Martins, D. Sponseller, N.-O. Stutzer, H. Thommesen, V. Vikenes, D. J. Watts, I. K. Wehus, L. Zapelli

Astrophysics of Galaxies

Testing subhalo abundance matching with galaxy kinematics

Fedir Boreiko, Tariq Yasin, Harry Desmond et al. (+2 more)

The rotation velocities of disc galaxies trace dark matter halo structure, providing direct constraints on the galaxy–halo connection. We construct a Bayesian forward model to connect the dark matter halo population predicted by $\Lambda$CDM with an observed sample of disc galaxies (SPARC) through their maximum rotation velocities. Our approach combines a subhalo abundance matching scheme (accounting for assembly bias) with a parameterised halo response to galaxy formation. When assuming no correlation between selection in the SPARC survey and halo properties, reproducing the observed velocities requires strong halo expansion, low abundance matching scatter ($<0.15$ dex at $1\sigma$) and a halo proxy that strongly suppresses the stellar masses in satellite haloes. This is in clear tension with independent clustering constraints. Allowing for SPARC-like galaxies to preferentially populate low $\Vmax$ haloes at fixed virial mass greatly improves the goodness-of-fit and resolves these tensions: the preferred halo response shifts to mild contraction, the abundance matching scatter increases to $\sint = 0.19^{+0.13}_{-0.11}$ dex and the proxy becomes consistent with clustering. However, the inferred selection threshold is extreme, implying that SPARC galaxies occupy the lowest ${\sim}16$ per cent of the $\Vmaxhalo$ distribution at fixed $\Mvir$. Moreover, even with selection, the inferred scatter remains in statistical disagreement with the low-mass clustering constraints, which are most representative of the SPARC galaxies in our sample. Our analysis highlights the advantage of augmenting clustering-based constraints on the galaxy–halo connection with kinematics and suggests a possible tension using current data.
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All authors Fedir Boreiko, Tariq Yasin, Harry Desmond, Richard Stiskalek, Matt J. Jarvis

Cosmology and Nongalactic Astrophysics

Euclid preparation. Calibrated intrinsic galaxy alignments in the Euclid Flagship simulation

Euclid Collaboration: K. Hoffmann, R. Paviot, B. Joachimi et al. (+297 more)

Intrinsic alignments of galaxies are potentially a major contaminant of cosmological analyses of weak gravitational lensing. We construct a semi-analytic model of galaxy ellipticities and alignments in the \Euclid Flagship simulation to predict this contamination in Euclid's weak lensing observations. Galaxy shapes and orientations are determined by the corresponding properties of the host haloes in the underlying $N$-body simulation, as well as the relative positions of galaxies within their halo. Alignment strengths are moderated via stochastic misalignments, separately for central and satellite galaxies and conditional on the galaxy's redshift, luminosity, and rest-frame colour. The resulting model is calibrated against galaxy ellipticity statistics from the COSMOS Survey, selected alignment measurements based on Sloan Digital Sky Survey samples, and galaxy orientations extracted from the Horizon-AGN hydrodynamic simulation at redshift $z=1$. The best-fit model has a total of 12 alignment parameters and generally reproduces the calibration data sets well within the $1\sigma$ statistical uncertainties of the observations and the \flagship simulation, with notable exceptions for the most luminous sub-samples on small physical scales. The statistical power of the calibration data and the volume of the single \flagship realisation are still too small to provide informative prior ranges for intrinsic alignment amplitudes in relevant galaxy samples. As a first application, we predict that \Euclid end-of-mission tomographic weak gravitational lensing two-point statistics are modified by up to order $10\,\%$ due to intrinsic alignments.
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All authors Euclid Collaboration: K. Hoffmann, R. Paviot, B. Joachimi, N. Tessore, P. Tallada-Crespí, N. E. Chisari, E. J. Gonzalez, A. Loureiro, P. Fosalba, J. Blazek, C. Laigle, Y. Dubois, C. Pichon, B. Altieri, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, S. Bardelli, F. Bernardeau, A. Biviano, E. Branchini, M. Brescia, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, V. F. Cardone, J. Carretero, S. Casas, F. J. Castander, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, A. Da Silva, H. Degaudenzi, G. De Lucia, H. Dole, F. Dubath, C. A. J. Duncan, X. Dupac, S. Dusini, S. Escoffier, M. Farina, R. Farinelli, S. Farrens, S. Ferriol, F. Finelli, N. Fourmanoit, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, S. V. H. Haugan, H. Hoekstra, W. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, E. Keihänen, S. Kermiche, A. Kiessling, M. Kilbinger, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, S. Marcin, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, E. Medinaceli, S. Mei, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, C. Neissner, S.-M. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, V. Pettorino, S. Pires, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, F. Raison, R. Rebolo, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, R. Saglia, Z. Sakr, A. G. Sánchez, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, A. Secroun, E. Sefusatti, G. Seidel, S. Serrano, P. Simon, C. Sirignano, G. Sirri, A. Spurio Mancini, L. Stanco, J. Steinwagner, A. N. Taylor, I. Tereno, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, A. Veropalumbo, Y. Wang, J. Weller, G. Zamorani, F. M. Zerbi, E. Zucca, M. Ballardini, E. Bozzo, C. Burigana, R. Cabanac, M. Calabrese, A. Cappi, D. Di Ferdinando, J. A. Escartin Vigo, L. Gabarra, W. G. Hartley, S. Matthew, M. Maturi, N. Mauri, R. B. Metcalf, A. Pezzotta, M. Pöntinen, C. Porciani, I. Risso, V. Scottez, M. Sereno, M. Tenti, M. Viel, M. Wiesmann, Y. Akrami, S. Alvi, I. T. Andika, S. Anselmi, M. Archidiacono, F. Atrio-Barandela, D. Bertacca, M. Bethermin, A. Blanchard, L. Blot, M. Bonici, S. Borgani, M. L. Brown, S. Bruton, A. Calabro, B. Camacho Quevedo, F. Caro, C. S. Carvalho, T. Castro, F. Cogato, S. Conseil, A. R. Cooray, O. Cucciati, S. Davini, G. Desprez, A. Díaz-Sánchez, J. J. Diaz, S. Di Domizio, J. M. Diego, M. Y. Elkhashab, A. Enia, Y. Fang, A. G. Ferrari, A. Finoguenov, A. Fontana, A. Franco, K. Ganga, J. García-Bellido, T. Gasparetto, V. Gautard, R. Gavazzi, E. Gaztanaga, F. Giacomini, F. Gianotti, G. Gozaliasl, M. Guidi, C. M. Gutierrez, A. Hall, S. Hemmati, H. Hildebrandt, J. Hjorth, S. Joudaki, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, J. Kim, C. C. Kirkpatrick, S. Kruk, J. Le Graet, L. Legrand, M. Lembo, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, L. Leuzzi, T. I. Liaudat, J. Macias-Perez, G. Maggio, M. Magliocchetti, F. Mannucci, R. Maoli, C. J. A. P. Martins, L. Maurin, M. Miluzio, P. Monaco, A. Montoro, C. Moretti, G. Morgante, S. Nadathur, K. Naidoo, A. Navarro-Alsina, S. Nesseris, D. Paoletti, F. Passalacqua, K. Paterson, L. Patrizii, A. Pisani, D. Potter, S. Quai, M. Radovich, P.-F. Rocci, G. Rodighiero, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, J. Schaye, A. Schneider, M. Schultheis, D. Sciotti, E. Sellentin, L. C. Smith, J. G. Sorce, K. Tanidis, C. Tao, G. Testera, R. Teyssier, S. Tosi, A. Troja, M. Tucci, C. Valieri, A. Venhola, D. Vergani, F. Vernizzi, G. Verza, P. Vielzeuf, N. A. Walton

Cosmology and Nongalactic Astrophysics

Euclid preparation. Testing analytic models of galaxy intrinsic alignments in the Euclid Flagship simulation

Euclid Collaboration: R. Paviot, B. Joachimi, K. Hoffmann et al. (+292 more)

We model intrinsic alignments (IA) in Euclid's Flagship simulation to investigate its impact on Euclid's weak lensing signal. Our IA implementation in the Flagship simulation takes into account photometric properties of galaxies as well as their dark matter host halos. We compare simulations against theory predictions, determining the parameters of two of the most widely used IA models: the Non Linear Alignment (NLA) and the Tidal Alignment and Tidal Torquing (TATT) models. We measure the amplitude of the simulated IA signal as a function of galaxy magnitude and colour in the redshift range $0.1<z<2.1$. We find that both NLA and TATT can accurately describe the IA signal in the simulation down to scales of $6$-$7 \,h^{-1}\,$Mpc. We measure alignment amplitudes for red galaxies comparable to those of the observations, with samples not used in the calibration procedure. For blue galaxies, our constraints are consistent with zero alignments in our first redshift bin $0.1 < z < 0.3$, but we detect a non-negligible signal at higher redshift, which is, however, consistent with the upper limits set by observational constraints. Additionally, several hydrodynamical simulations predict alignment for spiral galaxies, in agreement with our findings. Finally, the evolution of alignment with redshift is realistic and comparable to that determined in the observations. However, we find that the commonly adopted redshift power-law for IA fails to reproduce the simulation alignments above $z=1.1$. A significantly better agreement is obtained when a luminosity dependence is included, capturing the intrinsic luminosity evolution with redshift in magnitude-limited surveys. We conclude that the Flagship IA simulation is a useful tool for translating current IA constraints into predictions for IA contamination of Euclid-like samples.
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All authors Euclid Collaboration: R. Paviot, B. Joachimi, K. Hoffmann, S. Codis, I. Tutusaus, D. Navarro-Gironés, J. Blazek, F. Hervas-Peters, B. Altieri, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, S. Bardelli, A. Biviano, E. Branchini, M. Brescia, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, V. F. Cardone, J. Carretero, S. Casas, F. J. Castander, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, A. Da Silva, H. Degaudenzi, S. de la Torre, G. De Lucia, H. Dole, F. Dubath, C. A. J. Duncan, X. Dupac, S. Dusini, S. Escoffier, M. Farina, R. Farinelli, S. Farrens, S. Ferriol, F. Finelli, P. Fosalba, M. Frailis, E. Franceschi, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, S. V. H. Haugan, H. Hoekstra, W. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, E. Keihänen, S. Kermiche, A. Kiessling, M. Kilbinger, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, S. Marcin, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, S. Maurogordato, E. Medinaceli, S. Mei, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, C. Neissner, S.-M. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, V. Pettorino, S. Pires, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, F. Raison, R. Rebolo, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, R. Saglia, Z. Sakr, A. G. Sánchez, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, A. Secroun, E. Sefusatti, G. Seidel, S. Serrano, P. Simon, C. Sirignano, G. Sirri, A. Spurio Mancini, L. Stanco, J. Steinwagner, P. Tallada-Crespí, A. N. Taylor, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, L. Valenziano, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, A. Veropalumbo, Y. Wang, J. Weller, A. Zacchei, G. Zamorani, F. M. Zerbi, E. Zucca, E. Bozzo, C. Burigana, R. Cabanac, M. Calabrese, J. A. Escartin Vigo, L. Gabarra, W. G. Hartley, S. Matthew, M. Maturi, N. Mauri, R. B. Metcalf, A. Pezzotta, M. Pöntinen, C. Porciani, I. Risso, V. Scottez, M. Sereno, M. Tenti, M. Viel, M. Wiesmann, Y. Akrami, I. T. Andika, S. Anselmi, M. Archidiacono, F. Atrio-Barandela, D. Bertacca, M. Bethermin, A. Blanchard, L. Blot, H. Böhringer, M. Bonici, S. Borgani, M. L. Brown, S. Bruton, A. Calabro, B. Camacho Quevedo, F. Caro, C. S. Carvalho, T. Castro, F. Cogato, S. Conseil, A. R. Cooray, O. Cucciati, S. Davini, F. De Paolis, G. Desprez, A. Díaz-Sánchez, J. J. Diaz, S. Di Domizio, J. M. Diego, P. Dimauro, M. Y. Elkhashab, A. Enia, Y. Fang, A. G. Ferrari, A. Finoguenov, A. Fontana, A. Franco, K. Ganga, J. García-Bellido, T. Gasparetto, V. Gautard, R. Gavazzi, E. Gaztanaga, F. Giacomini, F. Gianotti, G. Gozaliasl, M. Guidi, C. M. Gutierrez, A. Hall, S. Hemmati, H. Hildebrandt, J. Hjorth, S. Joudaki, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, J. Kim, C. C. Kirkpatrick, S. Kruk, J. Le Graet, L. Legrand, M. Lembo, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, T. I. Liaudat, A. Loureiro, J. Macias-Perez, G. Maggio, M. Magliocchetti, F. Mannucci, R. Maoli, C. J. A. P. Martins, L. Maurin, M. Miluzio, P. Monaco, C. Moretti, G. Morgante, S. Nadathur, K. Naidoo, P. Natoli, A. Navarro-Alsina, S. Nesseris, L. Pagano, D. Paoletti, F. Passalacqua, K. Paterson, L. Patrizii, A. Pisani, D. Potter, S. Quai, M. Radovich, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, A. Schneider, M. Schultheis, D. Sciotti, E. Sellentin, L. C. Smith, J. G. Sorce, K. Tanidis, C. Tao, G. Testera, R. Teyssier, S. Tosi, A. Troja, M. Tucci, C. Valieri, A. Venhola, D. Vergani, F. Vernizzi, G. Verza, P. Vielzeuf, N. A. Walton

Cosmology and Nongalactic Astrophysics

Popcorn in the sky: Identifying primordial black holes in the gravitational-wave background

Eleni Bagui, Sébastien Clesse, Federico De Lillo et al. (+2 more)

Primordial black holes (PBHs) are possible sources of a gravitational-wave background (GWB), detectable with the next observing runs of LIGO–Virgo–KAGRA. In case of a detection, it will be crucial to distinguish the possible sources of this GWB. One under-explored possibility is to exploit the duty cycle that quantifies the number of sources present in the time domain signal, which can be very different depending on the nature and population of the sources. We compute the duty cycle for a realistic population of PBH binaries, isolating the shot-noise, popcorn and continuous contributions to the GWB. We identify the dependence of the duty cycle on the signal frequency, duration and amplitude as a crucial metric for distinguishing PBHs from other sources in the GWB and constraining PBH models. Our work motivates the development of specific analysis tools to extract these observables, in order to unlock new cosmological insights with upcoming GW data.
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All authors Eleni Bagui, Sébastien Clesse, Federico De Lillo, Alexander C. Jenkins, Mairi Sakellariadou

Astrophysics of Galaxies

Core Scouring Dynamics and Gravitational Wave Consequences: Constraints on Supermassive Black Hole Binary Hardening

C.J. Harris, Kayhan Gultekin and Laura Blecha

We present a multi-messenger investigation of supermassive black hole binary (SBHB) hardening by jointly comparing models to the observed stellar mass deficits of nearby core galaxies and to nanohertz gravitational-wave background measurements. Using merger trees from the IllustrisTNG cosmological simulations, we construct a synthetic population of core galaxies and predict their stellar mass deficits under binary evolution driven by dynamical friction, stellar scattering, and gravitational-wave emission, assuming circular orbits. We calibrate the efficiency of stellar scattering by matching the observed relation between stellar mass deficit and galaxy stellar mass. The inferred hardening rates reproduce the observed core population when stellar scattering is more efficient than in our baseline prescription, consistent with additional environmental or dynamical effects. However, these rates do not produce the level of low-frequency attenuation required to match the apparent turnover in the nanohertz gravitational-wave background. This tension suggests that either additional physics–such as eccentricity evolution, gas dynamics, recoils, triple interactions, or changes in the black hole–galaxy scaling relation–or contributions from galaxy populations not represented by local core galaxies (e.g., massive power-law ellipticals) may be important. A comprehensive treatment of these effects is required before identifying the dominant mechanisms shaping the gravitational-wave spectrum.
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High Energy Astrophysical Phenomena

A COLIBRI Photometric Study of SN 2025bvm: A Normal, Slowly Declining Type Ia Supernova

Diego Hernando Gonzalez-Buitrago, Maria Teresa Garcia-Diaz, Alberto Emiliano Montoya-Olivo et al. (+2 more)

We present 121 days of multi-band (\Bband, \gband, \rband, \iband) optical photometry of the Type Ia supernova SN 2025bvm, obtained with the COLIBRI telescope at OAN-SPM. The light curves show a photometric decline of $\Delta m_{15}(B) = 0.867 \pm 0.051$~mag, characteristic of a slow-declining Type Ia supernova. After correcting for host galaxy extinction ($E(B-V)_{host} = 0.308 \pm 0.030$~mag) and adopting a distance of 70~Mpc, we derive a peak absolute magnitude of $M_B = -19.13 \pm 0.40$~mag. This luminosity is fully consistent with its slow decline rate, placing SN 2025bvm within the population of normal Type Ia supernovae. We conclude that SN 2025bvm is a normal Type Ia supernova, whose photometric properties, such as a slow late-time decline and a prominent \iband-band secondary maximum, suggest an explosion that resulted in a particularly massive ejecta.
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All authors Diego Hernando Gonzalez-Buitrago, Maria Teresa Garcia-Diaz, Alberto Emiliano Montoya-Olivo, Sergio Sanchez-Sanjuan, Hector Avila-Mogollon

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

Systematic Biases in Gravitational-Wave Parameter Estimation from Neglecting Orbital Eccentricity in Space-Based Detectors

Jin-Zhao Yang, Jia-Hao Zhong and Tao Yang

Accurate modeling of gravitational-wave signals is essential for reliable inference of compact-binary source parameters, particularly for future space-based detectors operating in the milli- and deci-Hertz bands. In this work, we systematically investigate the parameter-estimation biases induced by neglecting orbital eccentricity when analyzing eccentric compact-binary coalescences with quasicircular waveform templates. Focusing on the deci-Hertz detector B-DECIGO and the milli-Hertz detector LISA, we model eccentric inspiral signals using a frequency-domain waveform that incorporates eccentricity-induced higher harmonics and the time-dependent response of spaceborne detectors. We quantify systematic biases in the chirp mass, symmetric mass ratio, and luminosity distance using both Bayesian inference and the Fisher-Cutler-Vallisneri (FCV) formalism, and assess their significance relative to statistical uncertainties. By constructing mock gravitational-wave catalogs spanning stellar-mass and massive black-hole binaries, we identify critical initial eccentricities at which systematic errors become comparable to statistical errors. We find that, for B-DECIGO, adopting a one-year observation period with f_min$ = 0.1$ Hz, even very small eccentricities, $e_0 \sim 10^{-4}-10^{-3}$ at 0.1 Hz, can lead to significant biases, whereas for LISA, adopting a five-year observation period with f_min$ = 10^{-4}$ Hz, such effects typically arise at larger eccentricities, $e_0 \sim 10^{-2}-10^{-1}$ at $10^{-4}$ Hz, due to the smaller number of in-band cycles. Comparisons between FCV predictions and full Bayesian analyses show good agreement over most of the initial eccentricity range, but diverge at high eccentricity, where Bayesian inference is required. Our results highlight the necessity of incorporating eccentricity in waveform models for future space-based gravitational-wave observations.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Rotation-dependent $I$-Love-$Q$-$\delta M$ relations in perturbation theory

Eneko Aranguren

The so-called $I$-Love-$Q$ relations link some normalized versions of the moment of inertia, the Love number, and the quadrupole moment of a star. These relations, in principle, enable the inference of two of the quantities given the third. However, their use has been limited because the normalized versions of the multipole moments rely on the static mass derived from the Tolman-Oppenheimer-Volkoff equation, which is not directly observable. In this work, using perturbation theory, we find that the $I$-Love-$Q$ relations can also be formulated in terms of an alternative set of normalized quantities that do not depend on the static mass, but on the actual (observable) mass.
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Solar and Stellar Astrophysics · Cross-listed from nucl-th

Learning the relations between neutron star and nuclear matter properties with symbolic regression

N. K. Patra, Tuhin Malik, Kai Zhou et al. (+1 more)

The equation of state (EOS) of dense matter in neutron stars (NSs) remains uncertain, particularly at supra-nuclear densities where complex nuclear interactions and the potential presence of exotic matter, like hyperons, come into play. The complex relationships existing between nuclear matter and neutron star properties are investigated. The focus is on their nonlinearities and interdependencies. In our analysis, we apply a machine learning algorithm known as symbolic regression, paired with principal component analysis, to datasets generated from Bayesian inference over relativistic mean-field models. A systematic Principal Component Analysis has allowed to break down the percentage contribution of each element or feature in the relationships obtained. This study examines two main models (datasets): the NL model, which includes nucleonic degrees of freedom; and the NL-hyp model, which includes hyperons in addition to nucleons. Our analysis confirms a robust correlation between the tidal deformability of a 1.4 \(M_\odot\) neutron star and $\beta$-equilibrium pressure at twice the nuclear saturation density. This correlation remains once hyperons are included. The contribution of the different nuclear matter properties at saturation to the radius and tidal deformability was calculated. It was shown that the isovector properties have the largest impact, with a contribution of about 90%. We also studied the relationship between the proton fraction at different densities and various symmetry energy parameters defined at saturation density. For the hyperon data set, we took into account the effects of the negatively charged hyperon $\Xi$ in order to recover the relationships. Our study reveals the individual impact of various symmetry energy parameters on proton fractions at different densities.
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All authors N. K. Patra, Tuhin Malik, Kai Zhou, Constança Providência

Solar and Stellar Astrophysics · Cross-listed from nucl-th

Multi-Physics Bayesian Analysis of Neutron Star Crust Using Relativistic Mean-Field Model

Vishal Parmar and Ignazio Bombaci

We study the properties of neutron-star crust within a Bayesian framework based on a unified relativistic mean-field (RMF) description of dense matter. The analysis focuses on the posterior distributions of crust properties, constrained by nuclear experimental data, chiral effective field theory, and multimessenger neutron-star observations. In the inference, the outer crust is fixed using the AME2020 nuclear mass table, supplemented by Hartree–Fock–Bogoliubov mass models, while the inner crust is described using a compressible liquid-drop model consistently coupled to the RMF interaction. The same RMF framework is used to describe the uniform core, ensuring a unified treatment across all density regimes. From the resulting posteriors, we extract key crustal observables, including the crust–core transition density and pressure, crust thickness, crust mass, and the fractional crustal moment of inertia. We find that the transition density is primarily governed by the symmetry-energy slope $L$ and curvature $K_{\rm sym}$ evaluated at sub-saturation densities, while the transition pressure plays a central role in determining global crustal properties. The inner-crust equation of state reflects a collective interplay between isovector nuclear-matter properties rather than a dependence on any single parameter. We also assess the impact of using matched crust–core constructions and show that they can introduce systematic differences in predicted neutron-star properties when compared with fully unified treatments.
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Cosmology and Nongalactic Astrophysics

Induced gravitational waves – beyond linear cosmological perturbation theory

Raphael Picard

This thesis focuses on gravitational waves (GWs) that arise beyond linear order in cosmological perturbation theory. In recent years, scalar-induced GWs have attracted significant attention because they may serve as the observational signature of primordial black holes (PBHs) formed in the early universe. The formation of PBHs requires large density perturbations, which can naturally emerge in some models of inflation. When these large density fluctuations couple, they act as a source for scalar-induced GWs at second order. In this work, we extend the existing formalism by including linear tensor fluctuations as an additional source term. This gives rise to two new classes of second-order GWs: those sourced by scalar-tensor couplings (scalar-tensor induced GWs) and those quadratic in tensor modes (tensor-tensor induced GWs). We find that the scalar-tensor contribution becomes significant if first-order tensor modes are enhanced, whilst the tensor-tensor contribution remains subdominant. Moreover, we demonstrate that the spectrum of scalar-tensor induced GWs exhibits an unphysical enhancement in the UV limit when the primordial scalar power spectrum is insufficiently peaked. To investigate whether this can be resolved, we study third-order induced GWs and their correlation with primordial GWs. We find that this new contribution suppresses the overall signal but does not cancel the unphysical enhancement. Possible explanations for this behaviour are discussed and left for future work. Finally, we explore the effect of primordial scalar non-Gaussianity on the spectrum of scalar-tensor induced GWs, building on previous results showing its impact on scalar-induced GWs.
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Instrumentation and Methods for Astrophysics

Brightness Characterization and Modeling for Amazon Leo Satellites

Anthony Mallama, Richard E. Cole, Hui Zhi et al. (+4 more)

The mean apparent magnitude of Amazon Leo satellites is 6.28 based on 1,938 observations. For spacecraft in their operational mode, 92% exceeded the brightness limit recommended by the IAU for interference with research, while 25% distract from aesthetic appreciation of the night sky. The reflective characteristics are similar to Version 1 Starlink spacecraft.
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All authors Anthony Mallama, Richard E. Cole, Hui Zhi, Brad Young, Jay Respler, Olga Zamora, Michelle Dadighat

High Energy Astrophysical Phenomena

Brightest GRB flare observed in GRB 221009A: bridge the last gap between flare and prompt emission in GRB

Zheng-Hang Yu, Chen-Wei Wang, Shao-Lin Xiong et al. (+46 more)

Flares are usually observed during the afterglow phase of Gamma-Ray Bursts (GRBs) in soft X-ray, optical and radio bands, but rarely in gamma-ray band. Despite the extraordinary brightness, GECAM-C has accurately measured both the bright prompt emission and flare emission of GRB 221009A without instrumental effects, offering a good opportunity to study the relation between them. In this work, we present a comprehensive analysis of flare emission of GRB 221009A, which is composed of a series of flares. Among them, we identify an exceptionally bright flare with a record-breaking isotropic energy $E_{\rm iso} = 1.82 \times 10^{53}$ erg of GRB flares. It exhibits the highest peak energy ever detected in GRB flares, $E_{\rm peak} \sim 300$ keV, making it a genuine gamma-ray flare. It also shows rapid rise and decay timescales, significantly shorter than those of typical X-ray flares observed in soft X-ray or optical band, but comparable to those observed in prompt emissions. Despite these exceptional properties, the flare shares several common properties with typical GRB flares. We note that this is the first observation of a GRB flare in the keV-MeV band with sufficiently high temporal resolution and high statistics, which bridges the last gap between prompt emission and flare.
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All authors Zheng-Hang Yu, Chen-Wei Wang, Shao-Lin Xiong, Shuang-Xi Yi, Wen-Long Zhang, Wen-Jun Tan, Yan-Qiu Zhang, Chao Zheng, Hao-Xuan Guo, Jia-Cong Liu, Yang-Zhao Ren, Yue Wang, Sheng-Lun Xie, Wang-Chen Xue, Jin-Peng Zhang, Peng Zhang, Zheng-Hua An, Ce Cai, Pei-Yi Feng, Min Gao, Ke Gong, Dongya Guo, Yue Huang, Bing Li, Cheng-Kui Li, Xiao-Bo Li, Xin-Qiao Li, Ya-Qing Liu, Xiao-Jing Liu, Xiang Ma, Wenxi Peng, Rui Qiao, Li-Ming Song, Jin Wang, Jin-Zhou Wang, Ping Wang, Xiang-Yang Wen, Shuo Xiao, Sheng Yang, Shu-Xu Yi, Qi-Bin Yi, Da-Li Zhang, Fan Zhang, Shuang-Nan Zhang, Yan-Ting Zhang, Zhen Zhang, Xiao-Yun Zhao, Yi Zhao, Shi-Jie Zheng

Cosmology and Nongalactic Astrophysics

Tachyonic gravitational dark matter production after inflation

Giorgio Laverda, Tomás Mendes and Javier Rubio

We propose a novel gravitational mechanism for the non-thermal production of dark matter driven by curvature-induced tachyonic instabilities after inflation. Departing from the commonly studied non-minimal couplings to gravity, our framework considers a real spectator scalar field coupled quadratically to spacetime curvature invariants. We show that the rapid reorganization of spacetime curvature at the end of inflation can dynamically render the dark matter field tachyonic, triggering a short-lived phase of spontaneous symmetry breaking and explosive particle production. As a concrete and theoretically controlled example, we focus on the Gauss-Bonnet topological invariant. By combining analytical estimates with $3+1$ classical lattice simulations in the spectator field approximation, we track the out-of-equilibrium evolution of the system and compute the resulting dark matter abundance. We find that this purely gravitational mechanism can robustly reproduce the observed dark matter relic density over a wide range of masses and inflationary scales, providing also a simple fitting function that enables a lattice-independent application of our results.
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Astrophysics of Galaxies · Cross-listed from physics.flu-dyn

Landau damping of disturbances in nearly inviscid inflectional shear flows

Evgeny V. Polyachenko, Ilia G. Shukhman and Michael Karp

We investigate the structure of damped two-dimensional perturbations in unstable plane-parallel shear flows with an inflection point. In inviscid flows within the stable wavenumber region $k$, no regular eigenmodes exist – the frequency spectrum $\omega$ consists of a continuous set of singular van Kampen modes with real frequencies. Nevertheless, initial perturbations of the total vorticity integrated across the flow decay exponentially, resembling the behavior of an eigenmode with complex eigenfrequency ${\rm Im}\,\omega<0$ (Landau damping). However, the vorticity itself does not decay but becomes increasingly corrugated across the flow. We demonstrate that accounting for arbitrarily small viscosity transforms this exponentially decaying perturbation into a true eigenmode in which the vorticity preserves its spatial form. We numerically trace the transformation of the vorticity structure of this mode and its disappearance as viscosity approaches zero. We discuss similarities and differences between the behavior of damped perturbations in the transition from inviscid to nearly inviscid flows in hydrodynamics and their behavior in plasma and homogeneous stellar systems during the analogous transition from collisionless to very weakly collisional systems.
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Cosmology and Nongalactic Astrophysics

CHEX-MATE: Relationship between X-ray and millimetre inferences of galaxy cluster temperature profiles

F. De Luca, H. Bourdin, P. Mazzotta et al. (+25 more)

Thermodynamic profiles from X-ray and millimetre observations of galaxy clusters are often compared under the simplifying assumptions of smooth, spherically symmetric intracluster medium. These approximations lead to expected discrepancies in the inferred profiles, which can provide insights about the cluster structure or cosmology. Motivated by this, we present a joint XMM-Newton and Planck analysis of 116 CHEX-MATE clusters to measure $\eta_T = T_X/T_{SZ,X}$, the ratio between spectroscopic X-ray temperatures and a temperature proxy derived from Sunyaev-Zel'dovich (SZ) pressures and X-ray densities. We considered relativistic corrections to the thermal SZ signal and implemented X-ray absorption by Galactic molecular hydrogen. The $\eta_T$ distribution has a mean of $1.01 \pm 0.03$, with average changes of $8.1\%$ and $2.7\%$ when relativistic corrections and molecular hydrogen absorption are not included, respectively. The $\eta_T$ distribution is positively skewed, with the scatter mostly affected by cluster morphology: relaxed clusters are closer to unity and less scattered than mixed and disturbed systems. We find little or no correlation with redshift, mass, or temperature.
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All authors F. De Luca, H. Bourdin, P. Mazzotta, G. Luzzi, M.G. Campitiello, M. De Petris, D. Eckert, S. Ettori, A. Ferragamo, W. Forman, M. Gaspari, F. Gastaldello, S. Ghizzardi, M. Gitti, S.T. Kay, J. Kim, L. Lovisari, J.F. Macías-Pérez, B.J. Maughan, M. Muñoz-Echeverría, F. Oppizzi, E. Pointecouteau, G.W. Pratt, E. Rasia, M. Rossetti, H. Saxena, J. Sayers, M. Sereno

High Energy Astrophysical Phenomena

A Unified Charge-Dependent Modulation Model for AMS-02 Proton and Antiproton Fluxes during Solar Minimum

Hui-Ming Zhang, Su-Jie Lin, Jie Feng et al. (+4 more)

We develop a unified charge-dependent solar modulation model by solving the three-dimensional Parker transport equation, incorporating a realistic wavy heliospheric current sheet to treat drift effects self-consistently. Using a local interstellar spectrum from GALPROP constrained by Voyager data, we fit the model to time-resolved proton and antiproton fluxes measured by the Alpha Magnetic Spectrometer-02 (AMS-02) from May 2011 to June 2022, excluding the heliospheric magnetic field (HMF) polarity-reversal epoch (mid-2012 to early 2015). To enable rapid parameter scans, we employ neural-network-based surrogate models to compute propagation and modulation matrices efficiently. The results demonstrate that the model simultaneously describes the observed proton and antiproton fluxes with physically reasonable parameters, providing a unified account of charge-dependent modulation.
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All authors Hui-Ming Zhang, Su-Jie Lin, Jie Feng, Jie-Teng Jiang, Yu-Dong Cui, Yi-Han Liu, Li-Li Yang

Solar and Stellar Astrophysics

Impact of Nuclear Reaction Rates on Calcium Production in Population III Stars: A Global Analysis

Qing Wang, Ertao Li, Yinwen Guan et al. (+13 more)

We investigate the sensitivity of calcium production to nuclear reaction rates of a 40 solar-mass Population III star using 1D multi-zone stellar models. A comprehensive nuclear reaction network was constructed, and all $(p,\gamma)$ and $(p,\alpha)$ reaction rates were individually varied by a factor of 10 up and down, identifying 13 preliminary key reactions for calcium production. To propagate the reaction rate uncertainties on calcium production, two sets of Monte Carlo simulations were performed for these key reactions: one adopting STARLIB reaction rates and the other incorporating updated rates from recent experimental data and evaluations. Our results show that Monte Carlo simulations using the updated rates show good agreement with the observed calcium abundance of the extremely iron-poor star SMSS J031300.36-670839.3 within the 68% confidence interval predicted by the models. In contrast, the observed calcium abundance lies marginally outside the 68% C.I. when using the STARLIB rates. Spearman rank-order correlation analysis and SHAP values show that the $(p,\gamma)$ and $(p,\alpha)$ reactions of F18 and F19 exhibit strong coupled effects on calcium production. These reaction-rate uncertainties need to be reduced to constrain the stellar model predictions. Our study provides insights for future nuclear physics experiments aimed at reducing reaction rate uncertainties in the nucleosynthesis of Population III Stars. Additionally, comparisons between 20 solar-mass and 40 solar-mass Population III stellar models confirm that the latter, with updated reaction rates, is more capable of reproducing the observed Ca abundance and [Ca/Mg] ratio.
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All authors Qing Wang, Ertao Li, Yinwen Guan, Zhihong Li, Jianjun He, Liyong Zhang, Bing Guo, Youbao Wang, Yunju Li, Jun Su, Xiaodong Tang, Shipeng Hu, Yu Liu, Dong Xiang, Lei Yang, Weiping Liu

Instrumentation and Methods for Astrophysics · Cross-listed from physics.space-ph

Coordinate Systems and Transforms in Space Physics: Terms, Definitions, Implementations, and Recommendations for Reproducibility

R.S. Weigel, A.Y. Shih, R. Ringuette et al. (+6 more)

In space physics, acronyms for coordinate systems (e.g., GEI, GSM) are commonly used; however, differences in their definitions and implementations can prevent reproducibility. In this work, we compare definitions in online resources, software packages, and frequently cited journal articles and show that implementation differences can lead to transformations between same-named coordinate systems and position values from different data providers to differ significantly. Based on these comparisons and results, and to enable reproducibility, we recommend that (a) a standard for acronyms and definitions for coordinate systems is developed, similar to equivalents in astronomy or earth sciences; (b) a standards body develops a citable database of reference data needed for these transforms. For software that computes coordinate transforms, we also recommend that their developers provide explicit comparisons of their implementations with the results of (b) and documentation on implementation choices. Additionally, we provide recommendations for scientists and metadata developers to ensure that sufficient information is provided to enable reproducibility. Finally, we document that spacecraft positions from data providers can differ both because of differences in how they implemented transforms and because of differences in the original source of the position data, and provide recommendations to improve the documentation of spacecraft positional datasets.
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All authors R.S. Weigel, A.Y. Shih, R. Ringuette, I. Christopher, S.M. Petrinec, S. Turner, R.M. Candey, G.K. Stephens, B. Cecconi

Astrophysics of Galaxies

Galaxy Mergers in UNIONS – II: Predicting Timescales in the Post-Merger Regime

Leonardo Ferreira, Sara L. Ellison, David R. Patton et al. (+3 more)

Galaxy mergers are critical events that influence galaxy evolution by driving processes such as enhanced star formation, quenching, and active galactic nucleus (AGN) activity. However, constraining the timescales over which these processes occur in the post-merger phase has remained a significant challenge. This study extends the MUlti-Model Merger Identifier (Mummi) framework to predict post-merger timescales ($T_{PM}$) for galaxies, leveraging machine learning models trained on realism-enhanced mock observations derived from the IllustrisTNG simulations. By classifying post-merger galaxies into four temporal bins spanning 0 to 1.76 Gyr after coalescence, Mummi achieves time classification accuracies exceeding 70 per cent. We apply this framework to the Ultraviolet Near Infrared Optical Northern Survey (UNIONS), yielding a catalog of 8,716 post-merger galaxies with $T_{PM}$ predictions and stellar masses $\log(M_*/M_\odot) \geq 10$ at redshifts 0.03 < z < 0.3. These results provide a robust methodology to connect galaxy interaction timescales with physical processes, enabling detailed studies of galaxy evolution in the post-merger regime.
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All authors Leonardo Ferreira, Sara L. Ellison, David R. Patton, Shoshannah Byrne-Mamahit, Scott Wilkinson, Robert W. Bickley

High Energy Astrophysical Phenomena

Deep Search for Joint Sources of Gravitational Waves and High-Energy Neutrinos with IceCube During the Third Observing Run of LIGO and Virgo

The IceCube Collaboration: R. Abbasi, M. Ackermann, J. Adams et al. (+2212 more)

The discovery of joint sources of high-energy neutrinos and gravitational waves has been a primary target for the LIGO, Virgo, KAGRA, and IceCube observatories. The joint detection of high-energy neutrinos and gravitational waves would provide insight into cosmic processes, from the dynamics of compact object mergers and stellar collapses to the mechanisms driving relativistic outflows. The joint detection of multiple cosmic messengers can also elevate the significance of the common observation even when some or all of the constituent messengers are sub-threshold, i.e. not significant enough to declare their detection individually. Using data from the LIGO, Virgo, and IceCube observatories, including sub-threshold events, we searched for common sources of gravitational waves and high-energy neutrinos during the third observing run of Advanced LIGO and Advanced Virgo detectors. Our search did not identify significant joint sources. We derive constraints on the rate densities of joint sources. Our results constrain the isotropic neutrino emission from gravitational-wave sources for very high values of the total energy emitted in neutrinos (> $10^{52} - 10^{54}$ erg).
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All authors The IceCube Collaboration: R. Abbasi, M. Ackermann, J. Adams, S. K. Agarwalla, J. A. Aguilar, M. Ahlers, J.M. Alameddine, S. Ali, N. M. Amin, K. Andeen, C. Argüelles, Y. Ashida, S. Athanasiadou, S. N. Axani, R. Babu, X. Bai, J. Baines-Holmes, A. Balagopal V., S. W. Barwick, S. Bash, V. Basu, R. Bay, J. J. Beatty, J. Becker Tjus, P. Behrens, J. Beise, C. Bellenghi, S. Benkel, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, E. Blaufuss, L. Bloom, S. Blot, I. Bodo, F. Bontempo, J. Y. Book Motzkin, C. Boscolo Meneguolo, S. Böser, O. Botner, J. Böttcher, J. Braun, B. Brinson, Z. Brisson-Tsavoussis, R. T. Burley, D. Butterfield, M. A. Campana, K. Carloni, J. Carpio, S. Chattopadhyay, N. Chau, Z. Chen, D. Chirkin, S. Choi, B. A. Clark, A. Coleman, P. Coleman, G. H. Collin, D. A. Coloma Borja, A. Connolly, J. M. Conrad, S. T. Countryman, D. F. Cowen, C. De Clercq, J. J. DeLaunay, D. Delgado, T. Delmeulle, S. Deng, P. Desiati, K. D. de Vries, G. de Wasseige, T. DeYoung, J. C. Díaz-Vélez, S. DiKerby, T. Ding, M. Dittmer, A. Domi, L. Draper, L. Dueser, D. Durnford, K. Dutta, M. A. DuVernois, T. Ehrhardt, L. Eidenschink, A. Eimer, C. Eldridge, P. Eller, E. Ellinger, D. Elsässer, R. Engel, H. Erpenbeck, W. Esmail, S. Eulig, J. Evans, P. A. Evenson, K. L. Fan, K. Fang, K. Farrag, A. R. Fazely, A. Fedynitch, N. Feigl, C. Finley, L. Fischer, D. Fox, A. Franckowiak, S. Fukami, P. Fürst, J. Gallagher, E. Ganster, A. Garcia, M. Garcia, G. Garg, E. Genton, L. Gerhardt, A. Ghadimi, C. Glaser, T. Glüsenkamp, J. G. Gonzalez, S. Goswami, A. Granados, D. Grant, S. J. Gray, S. Griffin, S. Griswold, K. M. Groth, D. Guevel, C. Günther, P. Gutjahr, C. Ha, C. Haack, A. Hallgren, L. Halve, F. Halzen, L. Hamacher, M. Ha Minh, M. Handt, K. Hanson, J. Hardin, A. A. Harnisch, P. Hatch, A. Haungs, J. Häußler, K. Helbing, J. Hellrung, B. Henke, L. Hennig, F. Henningsen, L. Heuermann, R. Hewett, N. Heyer, S. Hickford, A. Hidvegi, C. Hill, G. C. Hill, R. Hmaid, K. D. Hoffman, D. Hooper, S. Hori, K. Hoshina, M. Hostert, W. Hou, M. Hrywniak, T. Huber, K. Hultqvist, K. Hymon, A. Ishihara, W. Iwakiri, M. Jacquart, S. Jain, O. Janik, M. Jansson, M. Jeong, M. Jin, N. Kamp, D. Kang, W. Kang, A. Kappes, L. Kardum, T. Karg, M. Karl, A. Karle, A. Katil, M. Kauer, J. L. Kelley, M. Khanal, A. Khatee Zathul, A. Kheirandish, H. Kimku, J. Kiryluk, C. Klein, S. R. Klein, Y. Kobayashi, A. Kochocki, R. Koirala, H. Kolanoski, T. Kontrimas, L. Köpke, C. Kopper, D. J. Koskinen, P. Koundal, M. Kowalski, T. Kozynets, A. Kravka, N. Krieger, J. Krishnamoorthi, T. Krishnan, K. Kruiswijk, E. Krupczak, A. Kumar, E. Kun, N. Kurahashi, N. Lad, C. Lagunas Gualda, L. Lallement Arnaud, M. J. Larson, F. Lauber, J. P. Lazar, K. Leonard DeHolton, A. Leszczyńska, C. Li, J. Liao, C. Lin, Q. R. Liu, Y. T. Liu, M. Liubarska, C. Love, L. Lu, F. Lucarelli, W. Luszczak, Y. Lyu, M. Macdonald, J. Madsen, E. Magnus, Y. Makino, E. Manao, S. Mancina, A. Mand, I. C. Mariş, S. Marka, Z. Marka, L. Marten, I. 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Krishnendu, A. Królak, K. Kruska, G. Kuehn, P. Kuijer, S. Kulkarni, A. Kulur Ramamohan, A. Kumar, Praveen Kumar, Prayush Kumar, Rahul Kumar, Rakesh Kumar, J. Kume, K. Kuns, N. Kuntimaddi, S. Kuroyanagi, N. J. Kurth, S. Kuwahara, K. Kwak, K. Kwan, J. Kwok, G. Lacaille, P. Lagabbe, D. Laghi, S. Lai, A. H. Laity, M. H. Lakkis, E. Lalande, M. Lalleman, P. C. Lalremruati, M. Landry, B. B. Lane, R. N. Lang, J. Lange, B. Lantz, A. La Rana, I. La Rosa, A. Lartaux-Vollard, P. D. Lasky, J. Lawrence, M. N. Lawrence, M. Laxen, A. Lazzarini, C. Lazzaro, P. Leaci, Y. K. Lecoeuche, H. M. Lee, H. W. Lee, K. Lee, R.-K. Lee, R. Lee, S. Lee, Y. Lee, I. N. Legred, J. Lehmann, L. Lehner, M. Le Jean, A. Lemaître, M. Lenti, M. Leonardi, M. Lequime, N. Leroy, M. Lesovsky, N. Letendre, M. Lethuillier, S. E. Levin, Y. Levin, K. Leyde, A. K. Y. Li, K. L. Li, T. G. F. Li, X. Li, Z. Li, A. Lihos, C-Y. Lin, C.-Y. Lin, E. T. Lin, F. Lin, H. Lin, L. C.-C. Lin, Y.-C. Lin, F. Linde, S. D. Linker, T. B. Littenberg, A. Liu, G. C. Liu, Jian Liu, F. Llamas Villarreal, J. Llobera-Querol, R. K. L. Lo, J.-P. Locquet, L. T. London, A. Longo, D. Lopez, M. Lopez Portilla, A. Lorenzo-Medina, V. Loriette, M. Lormand, G. Losurdo, T. P. Lott IV, J. D. Lough, H. A. Loughlin, C. O. Lousto, M. J. Lowry, N. Lu, H. Lück, A. P. Lundgren, A. W. Lussier, L.-T. Ma, S. Ma, M. Ma'arif, R. Macas, A. Macedo, M. MacInnis, R. R. Maciy, D. M. Macleod, I. A. O. MacMillan, A. Macquet, D. Macri, K. Maeda, S. Maenaut, I. Magaña Hernandez, S. S. Magare, C. Magazzù, R. M. Magee, E. Maggio, R. Maggiore, M. Magnozzi, M. Mahesh, S. Mahesh, M. Maini, S. Majhi, E. Majorana, C. N. Makarem, E. Makelele, J. A. Malaquias-Reis, U. Mali, S. Maliakal, A. Malik, N. Man, V. Mandic, V. Mangano, B. Mannix, G. L. Mansell, G. Mansingh, M. Manske, M. Mantovani, M. Mapelli, F. Marchesoni, D. Marín Pina, F. Marion, S. Márka, Z. Márka, A. S. Markosyan, A. Markowitz, E. Maros, S. Marsat, F. Martelli, I. W. Martin, R. M. Martin, B. B. Martinez, M. Martinez, V. Martinez, A. Martini, K. Martinovic, J. C. Martins, D. V. Martynov, E. J. Marx, L. Massaro, A. Masserot, M. Masso-Reid, M. Mastrodicasa, S. Mastrogiovanni, T. Matcovich, M. Matiushechkina, M. Matsuyama, N. Mavalvala, N. Maxwell, G. McCarrol, R. McCarthy, D. E. McClelland, S. McCormick, L. McCuller, S. McEachin, C. McElhenny, G. I. McGhee, J. McGinn, K. B. M. McGowan, J. McIver, A. McLeod, T. McRae, D. Meacher, Q. Meijer, A. Melatos, S. Mellaerts, A. Menendez-Vazquez, C. S. Menoni, F. Mera, R. A. Mercer, L. Mereni, K. Merfeld, E. L. Merilh, J. R. Mérou, J. D. Merritt, M. Merzougui, C. Messenger, C. Messick, M. Meyer-Conde, F. Meylahn, A. Mhaske, A. Miani, H. Miao, I. Michaloliakos, C. Michel, Y. Michimura, H. Middleton, S. Miller, M. Millhouse, E. Milotti, V. Milotti, Y. Minenkov, N. Mio, Ll. M. Mir, L. Mirasola, M. Miravet-Tenés, C.-A. Miritescu, A. K. Mishra, A. Mishra, C. Mishra, T. Mishra, A. L. Mitchell, J. G. Mitchell, S. Mitra, V. P. Mitrofanov, R. Mittleman, O. Miyakawa, S. Miyamoto, S. Miyoki, G. Mo, L. Mobilia, S. R. P. Mohapatra, S. R. Mohite, M. Molina-Ruiz, C. Mondal, M. Mondin, M. Montani, C. J. Moore, D. Moraru, A. More, S. More, G. Moreno, C. Morgan, S. Morisaki, Y. Moriwaki, G. Morras, A. Moscatello, P. Mourier, B. Mours, C. M. Mow-Lowry, F. Muciaccia, Arunava Mukherjee, D. Mukherjee, Samanwaya Mukherjee, Soma Mukherjee, Subroto Mukherjee, Suvodip Mukherjee, N. Mukund, A. Mullavey, J. Munch, J. Mundi, C. L. Mungioli, W. R. Munn Oberg, Y. Murakami, M. Murakoshi, P. G. Murray, S. Muusse, D. Nabari, S. L. Nadji, A. Nagar, N. Nagarajan, K. N. Nagler, K. Nakagaki, K. Nakamura, H. Nakano, M. Nakano, D. Nandi, V. Napolano, P. Narayan, I. Nardecchia, T. Narikawa, H. Narola, L. Naticchioni, R. K. Nayak, J. Neilson, A. Nelson, T. J. N. Nelson, M. Nery, A. Neunzert, S. Ng, L. Nguyen Quynh, S. A. Nichols, A. B. Nielsen, G. Nieradka, A. Niko, Y. Nishino, A. Nishizawa, S. Nissanke, E. Nitoglia, W. Niu, F. Nocera, M. Norman, C. North, J. Novak, J. F. Nuño Siles, L. K. Nuttall, K. Obayashi, J. Oberling, J. O'Dell, M. Oertel, A. Offermans, G. Oganesyan, J. J. Oh, K. Oh, T. O'Hanlon, M. Ohashi, M. Ohkawa, F. Ohme, A. S. Oliveira, R. Oliveri, B. O'Neal, K. Oohara, B. O'Reilly, N. D. Ormsby, M. Orselli, R. O'Shaughnessy, S. O'Shea, Y. Oshima, S. Oshino, S. Ossokine, C. Osthelder, I. Ota, D. J. Ottaway, A. Ouzriat, H. Overmier, B. J. Owen, A. E. Pace, R. Pagano, M. A. Page, A. Pai, A. Pal, S. Pal, M. A. Palaia, M. Pálfi, P. P. Palma, C. Palomba, P. Palud, H. Pan, J. Pan, K. C. Pan, R. Panai, P. K. Panda, S. Pandey, L. Panebianco, P. T. H. Pang, F. Pannarale, K. A. Pannone, B. C. Pant, F. H. Panther, F. Paoletti, A. Paolone, E. E. Papalexakis, L. Papalini, G. Papigkiotis, A. Paquis, A. Parisi, B.-J. Park, J. Park, W. Parker, G. Pascale, D. Pascucci, A. Pasqualetti, R. Passaquieti, L. Passenger, D. Passuello, O. Patane, D. Pathak, M. Pathak, A. Patra, B. Patricelli, A. S. Patron, K. Paul, S. Paul, E. Payne, T. Pearce, M. Pedraza, R. Pegna, A. Pele, F. E. Peña Arellano, S. Penn, M. D. Penuliar, A. Perego, Z. Pereira, J. J. Perez, C. Périgois, G. Perna, A. Perreca, J. Perret, S. Perriès, J. W. Perry, D. Pesios, S. Petracca, C. Petrillo, H. P. Pfeiffer, H. Pham, K. A. Pham, K. S. Phukon, H. Phurailatpam, M. Piarulli, L. Piccari, O. J. Piccinni, M. Pichot, M. Piendibene, F. Piergiovanni, L. Pierini, G. Pierra, V. Pierro, M. Pietrzak, M. Pillas, F. Pilo, L. Pinard, I. M. Pinto, M. Pinto, B. J. Piotrzkowski, M. Pirello, M. D. Pitkin, A. Placidi, E. Placidi, M. L. Planas, W. Plastino, R. Poggiani, E. Polini, L. Pompili, J. Poon, E. Porcelli, E. K. Porter, C. Posnansky, R. Poulton, J. Powell, M. Pracchia, B. K. Pradhan, T. Pradier, A. K. Prajapati, K. Prasai, R. Prasanna, P. Prasia, G. Pratten, G. Principe, M. Principe, G. A. Prodi, L. Prokhorov, P. Prosposito, A. Puecher, J. Pullin, M. Punturo, P. Puppo, M. Pürrer, H. Qi, J. Qin, G. Quéméner, V. Quetschke, C. Quigley, P. J. Quinonez, F. J. Raab, S. S. Raabith, G. Raaijmakers, S. Raja, C. Rajan, B. Rajbhandari, K. E. Ramirez, F. A. Ramis Vidal, A. Ramos-Buades, D. Rana, S. Ranjan, K. Ransom, P. Rapagnani, B. Ratto, S. Rawat, A. Ray, V. Raymond, M. Razzano, J. Read, M. Recaman Payo, T. Regimbau, L. Rei, S. Reid, D. H. Reitze, P. Relton, A. I. Renzini, P. Rettegno, B. Revenu, R. Reyes, A. S. Rezaei, F. Ricci, M. Ricci, A. Ricciardone, J. W. Richardson, M. Richardson, A. Rijal, K. Riles, H. K. Riley, S. Rinaldi, J. Rittmeyer, C. Robertson, F. Robinet, M. Robinson, A. Rocchi, L. Rolland, J. G. Rollins, A. E. Romano, R. Romano, A. Romero, I. M. Romero-Shaw, J. H. Romie, S. Ronchini, T. J. Roocke, L. Rosa, T. J. Rosauer, C. A. Rose, D. Rosińska, M. P. Ross, M. Rossello, S. Rowan, S. K. Roy, S. Roy, D. Rozza, P. Ruggi, N. Ruhama, E. Ruiz Morales, K. Ruiz-Rocha, S. Sachdev, T. Sadecki, J. Sadiq, P. Saffarieh, M. R. Sah, S. S. Saha, S. Saha, T. Sainrat, S. Sajith Menon, K. Sakai, M. Sakellariadou, S. Sakon, O. S. Salafia, F. Salces-Carcoba, L. Salconi, M. Saleem, F. Salemi, M. Sallé, S. Salvador, A. Sanchez, E. J. Sanchez, J. H. Sanchez, L. E. Sanchez, N. Sanchis-Gual, J. R. Sanders, E. M. Sänger, F. Santoliquido, T. R. Saravanan, N. Sarin, S. Sasaoka, A. Sasli, P. Sassi, B. Sassolas, H. Satari, R. Sato, Y. Sato, O. Sauter, R. L. Savage, T. Sawada, H. L. Sawant, S. Sayah, V. Scacco, D. Schaetzl, M. Scheel, A. Schiebelbein, M. G. Schiworski, P. Schmidt, S. Schmidt, R. Schnabel, M. Schneewind, R. M. S. Schofield, K. Schouteden, B. W. Schulte, B. F. Schutz, E. Schwartz, M. Scialpi, J. Scott, S. M. Scott, T. C. Seetharamu, M. Seglar-Arroyo, Y. Sekiguchi, D. Sellers, A. S. Sengupta, D. Sentenac, E. G. Seo, J. W. Seo, V. Sequino, M. Serra, G. Servignat, A. Sevrin, T. Shaffer, U. S. Shah, M. A. Shaikh, L. Shao, A. K. Sharma, P. Sharma, S. Sharma-Chaudhary, M. R. Shaw, P. Shawhan, N. S. Shcheblanov, E. Sheridan, Y. Shikano, M. Shikauchi, K. Shimode, H. Shinkai, J. Shiota, D. H. Shoemaker, D. M. Shoemaker, R. W. Short, S. ShyamSundar, A. Sider, H. Siegel, M. Sieniawska, D. Sigg, L. Silenzi, M. Simmonds, L. P. Singer, A. Singh, D. Singh, M. K. Singh, S. Singh, A. Singha, A. M. Sintes, V. Sipala, V. Skliris, B. J. J. Slagmolen, T. J. Slaven-Blair, J. Smetana, J. R. Smith, L. Smith, R. J. E. Smith, W. J. Smith, J. Soldateschi, K. Somiya, I. Song, K. Soni, S. Soni, V. Sordini, F. Sorrentino, N. Sorrentino, H. Sotani, R. Soulard, A. Southgate, V. Spagnuolo, A. P. Spencer, M. Spera, P. Spinicelli, J. B. Spoon, C. A. Sprague, A. K. Srivastava, F. Stachurski, D. A. Steer, J. Steinlechner, S. Steinlechner, N. Stergioulas, P. Stevens, M. StPierre, G. Stratta, M. D. Strong, A. Strunk, R. Sturani, A. L. Stuver, M. Suchenek, S. Sudhagar, N. Sueltmann, L. Suleiman, K. D. Sullivan, L. Sun, S. Sunil, J. Suresh, P. J. Sutton, T. Suzuki, Y. Suzuki, B. L. Swinkels, A. Syx, M. J. Szczepańczyk, P. Szewczyk, M. Tacca, H. Tagoshi, S. C. Tait, H. Takahashi, R. Takahashi, A. Takamori, T. Takase, K. Takatani, H. Takeda, K. Takeshita, C. Talbot, M. Tamaki, N. Tamanini, D. Tanabe, K. Tanaka, S. J. Tanaka, T. Tanaka, D. Tang, S. Tanioka, D. B. Tanner, L. Tao, R. D. Tapia, E. N. Tapia San Martín, R. Tarafder, C. Taranto, A. Taruya, J. D. Tasson, M. Teloi, R. Tenorio, H. Themann, A. Theodoropoulos, M. P. Thirugnanasambandam, L. M. Thomas, M. Thomas, P. Thomas, J. E. Thompson, S. R. Thondapu, K. A. Thorne, E. Thrane, J. Tissino, A. Tiwari, P. Tiwari, S. Tiwari, V. Tiwari, M. R. Todd, A. M. Toivonen, K. Toland, A. E. Tolley, T. Tomaru, K. Tomita, T. Tomura, C. Tong-Yu, A. Toriyama, N. Toropov, A. Torres-Forné, C. I. Torrie, M. Toscani, I. Tosta e Melo, E. Tournefier, A. Trapananti, F. Travasso, G. Traylor, M. Trevor, M. C. Tringali, A. Tripathee, G. Troian, L. Troiano, A. Trovato, L. Trozzo, R. J. Trudeau, T. T. L. Tsang, R. Tso, S. Tsuchida, L. Tsukada, T. Tsutsui, K. Turbang, M. Turconi, C. Turski, H. Ubach, N. Uchikata, T. Uchiyama, R. P. Udall, T. Uehara, M. Uematsu, K. Ueno, S. Ueno, V. Undheim, T. 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Walker, G. S. Wallace, L. Wallace, H. Wang, J. Z. Wang, W. H. Wang, Z. Wang, G. Waratkar, J. Warner, M. Was, T. Washimi, N. Y. Washington, D. Watarai, K. E. Wayt, B. R. Weaver, B. Weaver, C. R. Weaving, S. A. Webster, M. Weinert, A. J. Weinstein, R. Weiss, F. Wellmann, L. Wen, P. Weßels, K. Wette, J. T. Whelan, B. F. Whiting, C. Whittle, J. B. Wildberger, O. S. Wilk, D. Wilken, A. T. Wilkin, D. J. Willadsen, K. Willetts, D. Williams, M. J. Williams, N. S. Williams, J. L. Willis, B. Willke, M. Wils, J. Winterflood, C. C. Wipf, G. Woan, J. Woehler, J. K. Wofford, N. E. Wolfe, H. T. Wong, H. W. Y. Wong, I. C. F. Wong, J. L. Wright, M. Wright, C. Wu, D. S. Wu, H. Wu, E. Wuchner, D. M. Wysocki, V. A. Xu, Y. Xu, N. Yadav, H. Yamamoto, K. Yamamoto, T. S. Yamamoto, T. Yamamoto, S. Yamamura, R. Yamazaki, S. Yan, T. Yan, F. W. Yang, F. Yang, K. Z. Yang, Y. Yang, Z. Yarbrough, H. Yasui, S.-W. Yeh, A. B. Yelikar, X. Yin, J. Yokoyama, T. Yokozawa, J. Yoo, H. Yu, S. Yuan, H. Yuzurihara, A. Zadrożny, M. Zanolin, M. Zeeshan, T. Zelenova, J.-P. Zendri, M. Zeoli, M. Zerrad, M. Zevin, A. C. Zhang, L. Zhang, R. Zhang, T. Zhang, Y. Zhang, C. Zhao, Yue Zhao, Yuhang Zhao, Y. Zheng, H. Zhong, R. Zhou, X.-J. Zhu, Z.-H. Zhu, A. B. Zimmerman, M. E. Zucker, J. Zweizig

High Energy Astrophysical Phenomena

Timing Gamma-ray Pulsars using Gibbs Sampling

Colin J. Clark, Serena Valtolina, Lars Nieder et al. (+1 more)

Timing analyses of gamma-ray pulsars in the Fermi Large Area Telescope data set can provide sensitive probes of many astrophysical processes, including timing noise in young pulsars, orbital period variations in redback binaries, and the stochastic gravitational wave background (GWB). These goals can require careful accounting of stochastic noise processes, but existing methods developed to achieve this in radio pulsar timing analyses cannot be immediately applied to the discrete gamma-ray arrival time data. To address this, we have developed a new method for timing gamma-ray pulsars, in which the timing model fit is transformed into a weighted least squares problem by randomly assigning each photon to an individual Gaussian component of a template pulse profile. These random assignments are then numerically marginalised over through a Gibbs sampling scheme. This method allows for efficient estimation of timing and noise model parameters, while taking into account uncertainties in the pulse profile shape. We simulated Fermi-LAT data sets for gamma-ray pulsars with power-law timing noise processes, showing that this method provides robust estimates of timing noise parameters. We also describe a Gaussian-process model for orbital period variations in black-widow and redback binary systems that can be fit using this new timing method. We demonstrate this method on the black-widow binary millisecond pulsar B1957+20, where the orbital period varies significantly over the LAT data, but which provides one of the most stringent gamma-ray upper limits on the GWB.
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All authors Colin J. Clark, Serena Valtolina, Lars Nieder, Rutger van Haasteren

High Energy Astrophysical Phenomena

Cosmic rays, gamma rays and neutrinos from discrete black hole X-ray binary ejecta

Nicolas J. Bacon, Alex J. Cooper, Dimitrios Kantzas et al. (+2 more)

The origin of cosmic rays from outside the Solar system are unknown, as they are deflected by the interstellar magnetic field. Supernova remnants are the main candidate for cosmic rays up to PeV energies but due to lack of evidence, they cannot be concluded as the sources of the most energetic Galactic CRs. We investigate discrete ejecta produced in state transitions of black hole X-ray binary systems as a potential source of cosmic rays, motivated by recent $>100$ TeV $\gamma$-ray detections by LHAASO. Starting from MAXI J1820+070, we examine the multi-wavelength observations and find that efficient particle acceleration may take place (i.e. into a robust power-law), up to $\sim2\times 10^{16}\mu^{-1/2}$ eV, where $\mu$ is the ratio of particle energy to magnetic energy. From these calculations, we estimate the global contribution of ejecta to the entire Galactic spectrum to be $\sim1\%$, with the cosmic ray contribution rising to $\sim5\%$ at PeV energies, assuming roughly equal energy in non-thermal protons, non-thermal electrons and magnetic fields. In addition, we calculate associated $\gamma$-ray and neutrino spectra of the MAXI J1820+070 ejecta to investigate new detection methods with CTAO, which provide strong constraints on initial ejecta size of order $10^7$ Schwarzschild radii ($10^{-5}$ pc) assuming a period of adiabatic expansion.
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All authors Nicolas J. Bacon, Alex J. Cooper, Dimitrios Kantzas, James H. Matthews, Rob Fender