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Physics Astrophysics

astro-ph Watch Astrophysics

Monday 16 February

High Energy Astrophysical Phenomena

Pulsar based modeling of point spread function of Fermi Large Area Telescope

J. Blunier, A. Neronov and D. Semikoz

Sensitivity of searches for extended emission around gamma-ray sources is naturally limited by the precision of the knowledge of the Point Spread Function (PSF) of gamma-ray telescopes. Inaccuracies in the PSF models of the Fermi Large Area Telescope (LAT) can potentially lead to false positive detections of source extension. We explore uncertainties in the Fermi/LAT PSF by comparing the PSF models provided by the Fermi/LAT Instrument Response Functions (IRFs) with signals of bright pulsars. We compare the analytical PSF models of Fermi/LAT IRFs with pulsar data and fit the pulsar data with the same analytical model as in the Fermi/LAT IRFs to derive an improved set of PSF parameters. We then apply this revised PSF parameterisation to the search of extended emission around a blazar, Mrk 501. We find that the parameters of the analytical PSF models of Fermi/LAT IRFs are inconsistent with the pulsar data. We obtain an improved set of PSF parameters from the fits to pulsar data that is consistent with observations. We find no evidence of the previously reported extended signal around Mrk 501 if the revised PSF consistent with pulsar data is used in data analysis.
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Cosmology and Nongalactic Astrophysics

Exploring Non-minimal coupling using ultra-diffuse galaxies

Saboura Zamani, Vincenzo Salzano and Dario Bettoni

We investigate whether a non-minimal coupling between dark matter and gravity can influence the internal dynamics of ultra-diffuse galaxies. Within this framework, the gravitational potential is modified by an additional term that captures the interaction between spacetime curvature and the dark matter with a coupling constant determined by a length scale L. Using spherical Jeans modelling, we analyze the kinematic data of three ultra-diffuse galaxies: NGC 1052-DF2, NGC 1052-DF4, and Dragonfly 44, which span the observational extremes from dark matter deficient to dark matter dominated systems. For each galaxy we explore several dark matter halo profiles, two orbital anisotropy models, and both with and without Stellar to Halo Mass Relation scenarios, and we perform a Bayesian parameter inference. We further validate the analysis through a sensitivity test on mock Dragonfly 44 data, which shows that only large couplings, which are already disfavored by the data, produce a detectable imprint, while smaller values remain indistinguishable from General Relativity at the current observational precision. Across all the considered configurations, the constrained astrophysical parameters are consistent with standard ones from General Relativity. The posterior distributions of L show no preference for non-zero values and result only in upper limits. These upper limits should be interpreted as a sensitivity limit of current UDG kinematics rather than as a tight exclusion of the coupling. Future high precision velocity measurements will be essential to determine whether non-minimal coupling effects can become observationally distinguishable in low-acceleration systems.
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High Energy Astrophysical Phenomena

Bounds on Lorentz invariance violation from muon fluctuations at the Pierre Auger Observatory

The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu et al. (+357 more)

Quantum gravity theories often modify spacetime symmetries. In particular, Lorentz invariance may be violated when approaching the Planck scale. Although the scales at which interactions occur in extensive air showers induced by ultra-high-energy cosmic rays in the atmosphere are many orders of magnitude below the Planck scale, these violations might still be observable. In this work, the fluctuations in the number of muons in the extensive air showers measured at the Pierre Auger Observatory are exploited, for the first time, to constrain Lorentz invariance violations. The bounds derived in the hadronic sector are the strongest ever obtained, and do not rely on assumptions about the mass composition of ultra-high-energy cosmic rays. The fluctuations in the number of muons constitute a new and powerful observable to further explore Lorentz invariance in a region of the parameter space not accessible to other observables.
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All authors The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu, M. Aglietta, 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, E. Arnone, J.C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, Y. Balibrea, A. Baluta, F. Barbato, A. Bartz Mocellin, 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, A. Bueno, S. Buitink, M. Büsken, A. Bwembya, 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, Y. Dominguez Ballesteros, Q. Dorosti, R.C. dos Anjos, J. Ebr, F. Ellwanger, R. Engel, I. Epicoco, 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, T. Fitoussi, 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, J.M. González, 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, V.M. Harvey, 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, A. Khakurdikar, V.V. Kizakke Covilakam, H.O. Klages, M. Kleifges, 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, J.P. Lundquist, 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, M.A. Martins, H.-J. Mathes, J. Matthews, G. Matthiae, E. Mayotte, S. Mayotte, P.O. Mazur, G. Medina-Tanco, J. Meinert, 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, S. Panja, G. Parente, T. Paulsen, J. Pawlowsky, M. Pech, J. Pękala, R. Pelayo, V. Pelgrims, C. Pérez Bertolli, L. Perrone, S. Petrera, C. Petrucci, T. Pierog, M. Pimenta, M. Platino, B. Pont, M. Pourmohammad Shahvar, P. Privitera, C. Priyadarshi, M. Prouza, K. Pytel, S. Querchfeld, J. Rautenberg, D. Ravignani, J.V. Reginatto Akim, A. Reuzki, J. Ridky, F. Riehn, M. Risse, V. Rizi, 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, M. Stadelmaier, S. Stanič, J. Stasielak, P. Stassi, S. Strähnz, M. Straub, T. Suomijärvi, A.D. Supanitsky, Z. Svozilikova, Z. Szadkowski, F. Tairli, M. Tambone, 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, 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, C. Watanabe, A.A. Watson, A. Weindl, M. Weitz, L. Wiencke, H. Wilczyński, B. Wundheiler, B. Yue, A. Yushkov, E. Zas, D. Zavrtanik, M. Zavrtanik

High Energy Astrophysical Phenomena

4U 1556-60 as a very faint neutron star X-ray binary at 700 pc with an undetected radio jet

Eliot C. Pattie, Thomas J. Maccarone, Thomas Russell et al. (+3 more)

4U 1556-60 is a low-mass X-ray binary that was discovered more than 50 years ago as a persistent X-ray source; however, very little was known about it. Recently, Gaia obtained a parallax for the optical counterpart that places 4U 1556-60 at a distance of only about 700 pc, making it one of the closest X-ray binaries known to date. This close distance drastically alters what was previously assumed about the source. We revisit 4U 1556-60 in light of the newly determined distance of 700 pc, reinterpreting its literature and presenting new X-ray and radio observations to better understand various characteristics of the system. We conclude that a scenario in which 4U 1556-60 is a candidate ultracompact neutron star X-ray binary at a distance of ~700 pc is able to explain the observed properties of the source. It resides at a persistent X-ray luminosity of ~2x10^34 erg/s, an unusual value for a typical X-ray binary, but similar to several ultracompact systems. The ratio of the X-ray to optical luminosity is very high, also suggesting a physically small accretion disk. The radio jet is undetected with a very deep upper limit of 3x10^25 erg/s, which is about 10^3 times fainter than the expected black hole jet correlation, strongly indicating a neutron star accretor. The X-ray spectrum is dominated by a power law, and the X-ray timing properties are also consistent with observations of other very low accretion rate X-ray binaries. No spin or orbital periodicity are found in the X-ray data. Future observations, especially to determine its orbital period, will further aid in understanding 4U 1556-60.
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All authors Eliot C. Pattie, Thomas J. Maccarone, Thomas Russell, Matteo Bachetti, Nathalie Degenaar, Thomas Kupfer

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Investigating the impact of quasi-universal relations on neutron star constraints in third-generation detectors

Natalie Williams, Anna Puecher, Guilherme Grams et al. (+2 more)

Gravitational-wave observations of binary neutron star systems can shed light on the currently unknown dense matter equation of state. The equation of state determines a large number of neutron star properties, such as tidal deformability, radius, and quadrupole moment, several of which directly affect the emitted gravitational-wave signals. To reduce the dimensionality when computing gravitational-waves and when interpreting observational data, quasi-universal relations are commonly employed to connect different neutron star properties. However, quasi-universal relations are not exact and their use may introduce uncertainty and bias. We explore the potential biases arising from different quasi-universal relations in the third generation era: (i) the Love-Q relation connecting the spin-induced quadrupole moment and the tidal deformability, (ii) the relation between the fundamental mode frequency and the tidal deformability, and (iii) the binary Love relation. We find that for the quadrupole relation biases are only present for rapidly rotating systems, for the binary-Love relation induces moderate biases only in the next-to-leading-order tidal parameters, which can however propagate into the inferred equation of state at low masses. Regarding fundamental mode frequencies, we find that the employed relation introduces only negligible biases, while waveform systematic effects can become comparatively large. Our results highlight that while quasi-universal relations remain a useful tool within gravitational-wave analyses, careful treatment is needed to avoid biases in equation of state measurements with next-generation detectors.
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All authors Natalie Williams, Anna Puecher, Guilherme Grams, César V. Flores, Tim Dietrich

High Energy Astrophysical Phenomena

H.E.S.S. detection of the PSR J0855-4644 nebula

F. Aharonian, H. Ashkar, M. Backes et al. (+132 more)

HESS J0852-463 is a TeV {\gamma}-ray source located in the Galactic plane. The region consists of a supernova remnant (SNR, RX J0852.0-4622) with a shell-like morphology, commonly referred to as Vela Junior, and a pulsar denoted PSR J0855-4644. Pulsars are among the most efficient leptonic accelerators in our Galaxy, making this region particularly interesting to study. We utilise the most recent data taken by the High Energy Stereoscopic System (H.E.S.S.), to investigate any {\gamma}-ray emission associated with the pulsar in this region, PSR J0855-4644. We applied a full forward folding method on the H.E.S.S. data. Utilising 3D modelling techniques, we evaluated the TeV {\gamma}-ray emission towards the various components of this complex system. The distinct energy-dependent morphology observed in our data motivates further investigation of this source. We resolved the emission in the Vela Junior region into various components, several of which correspond to the SNR itself. In particular, we find a new extended component which is coincident with the position of PSR J0855-4644. The spectrum follows a power-law distribution with a best-fit index of {\Gamma}E = 1.81 \pm 0.07stat which differs from the properties of the surrounding {\gamma}-ray emission of the Vela Junior SNR. A one-zone leptonic joint fit between the X-rays (from XMM-Newton) and {\gamma}-rays (from H.E.S.S.) leads to a lower limit on the magnetic field of 1.6{\mu}G and a spectral index of {\alpha} = 1.88 \pm 0.01, in line with expectations of pulsar wind nebulae (PWNe). In this paper, we report the first detection of the PWN of PSR J0855-4644 at TeV energies with the H.E.S.S. experiment at a significance of 12.2{\sigma}. This is attributed to the advanced techniques of the 3D analysis. Based on the pulsar's characteristics, its PWN is consistent with the known TeV PWNe population in the Galaxy.
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All authors F. Aharonian, H. Ashkar, M. Backes, R. Batzofin, Y. Becherini, D. Berge, K. Bernlöhr, M. Böttcher, C. Boisson, J. Bolmont, F. Brun, B. Bruno, C. Burger-Scheidlin, T. Bylund, S. Casanova, D. Cecchin Momesso, J. Celic, M. Cerruti, A. Chen, M. Chernyakova, J.O. Chibueze, O. Chibueze, B. Cornejo, G. Cotter, G. Cozzolongo, J. de Assis Scarpin, M. de Bony de Lavergne, M. de Naurois, E. de Oña Wilhelmi, A.G. Delgado Giler, J. Devin, A. Dmytriiev, K. Egberts, K. Egg, J.-P. Ernenwein, C. Escañuela Nieves, P. Fauverge, K. Feijen, M.D. Filipovic, G. Fontaine, S. Funk, S. Gabici, Y.A. Gallant, M. Genaro, J.F. Glicenstein, J. Glombitza, P. Goswami, M.-H. Grondin, L. Heckmann, B. Heß, W. Hofmann, T.L. Holch, M. Holler, D. Horns, M. Jamrozy, F. Jankowsky, A. Jardin-Blicq, I. Jaroschewski, D. Jimeno, I. Jung-Richardt, E. Kasai, K. Katarzyński, D. Kerszberg, B. Khélifi, W. Kluźniak, N. Komin, K. Kosack, D. Kostunin, R.G. Lang, S. Lazarević, A. Lemière, M. Lemoine-Goumard, J.-P. Lenain, P. Liniewicz, A. Luashvili, J. Mackey, D. Malyshev, D. Malyshev, V. Marandon, M.G.F. Mayer, A. Mehta, A.M.W. Mitchell, R. Moderski, L. Mohrmann, E. Moulin, J. Niemiec, P. O'Brien, L. Olivera-Nieto, M.O. Moghadam, S. Panny, M. Panter, R.D. Parsons, P. Pichard, T. Preis, G. Pühlhofer, M. Punch, A. Quirrenbach, A. Reimer, O. Reimer, I. Reis, Q. Remy, H.X. Ren, B. Reville, F. Rieger, G. Rowell, B. Rudak, K. Sabri, V. Sahakian, M. Sasaki, F. Schüssler, J.N.S. Shapopi, W. Si Said, Ł. Stawarz, R. Steenkamp, S. Steinmassl, T. Tanaka, A.M. Taylor, G.L. Taylor, R. Terrier, Y. Tian, M. Tsirou, T. Unbehaunz, C. van Eldik, M. Vecchi, C. Venter, J. Vink, V. Voitsekhovskyi, T. Wach, S.J. Wagner, A. Wierzcholska, M. Zacharias, A. Zech, W. Zhong, F. Acero, L. Giunti

Cosmology and Nongalactic Astrophysics

Bayesian Cosmic Void Finding with Graph Flows

Leander Thiele

Cosmic voids contain higher-order cosmological information and are of interest for astroparticle physics. Finding genuine matter underdensities in sparse galaxy surveys is, however, an underconstrained problem. Traditional void finding algorithms produce deterministic void catalogs, neglecting the probabilistic nature of the problem. We present a method to sample from the stochastic mapping from galaxy catalogs to arbitrary void definitions. Our algorithm uses a deep graph neural network to evolve "test particles" according to a flow-matching objective. We demonstrate the method in a simplified example setting but outline steps to generalize it towards practically usable void finders. Trained on a deterministic teacher, the model performs well but has considerable stochasticity which we interpret as regularization. Cosmological information in the predicted void catalogs outperforms the teacher. On the one hand, our method can cheaply emulate existing void finders with apparently useful regularization. More importantly, it also allows us to find the Bayes-optimal mapping between observed galaxies and any void definition. This includes definitions operating at the level of simulated matter density and velocity fields.
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Astrophysics of Galaxies

Large-scale and local environmental drivers of quenching: tracing H$\alpha$ concentration in X-ray and optical galaxy groups

Stefania Barsanti, Di Wang, Matthew Colless et al. (+11 more)

To explore the environmental mechanisms causing quenching in nearby star-forming galaxies, we study the variation with local and large-scale environments of a star formation concentration index, C-index $\equiv\log{(r_{50,{\rm H}\alpha}/r_{50,\rm cont}})$, that traces the spatially-resolved distribution of H$\alpha$ emission. Our analysis combines (i) GAMA spectroscopic redshift survey data to optically select galaxy groups and reconstruct the cosmic web, (ii) eROSITA data to identify X-ray-emitting groups, and (iii) SAMI Galaxy Survey data to characterise spatially-resolved star formation. We find that galaxies in X-ray+optical groups exhibit the lowest median C-index and the highest fraction of centrally-concentrated star-forming galaxies relative to optical groups and the field (independently of group or stellar mass). Star-forming galaxies in more X-ray luminous groups at fixed dynamical mass show more concentrated star formation. At large scales, nodes show the lowest median C-index and the highest fraction of centrally-concentrated star-forming galaxies relative to filaments and voids, which have similar C-index distributions. C-index correlates most strongly with the distance to the closest node, leaving no significant role for other local or large-scale environment metrics. Finally, regular star-forming galaxies tend to have spins aligned parallel to filaments, consistent with smooth gas accretion, while centrally-concentrated galaxies tend have spins aligned perpendicular to filaments, likely driven by mergers and associated with bulge growth. These results suggest that multi-scale environmental processes, i.e. locally and at large-scale, act to concentrate star formation toward galaxy centres, via gas-related mechanisms in nodes and ram-pressure stripping in X-ray+optical groups.
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All authors Stefania Barsanti, Di Wang, Matthew Colless, Ang Liu, Esra Bulbul, Matt S. Owers, Scott M. Croom, Benedetta Vulcani, Julia J. Bryant, Yifan Mai, Sree Oh, Andrei Ristea, Sarah M. Sweet, Jesse van de Sande

Solar and Stellar Astrophysics

Infrared spectra of methane-containing ice mixtures for JWST data analyses

Varvara Karteyeva, Ruslan Nakibov, Igor Petrashkevich et al. (+2 more)

Context. Solid methane (CH$_4$) is an important molecule in interstellar and planetary environments, serving as a precursor to complex organic compounds, and it is a potential biosignature in exoplanetary studies. Despite its significance, laboratory data on the low temperature phase of methane below 10 K remain limited. Aims. We obtained spectra of methane in binary mixtures at 10 K and compared them to the spectra obtained at 6.7 K. These temperatures correspond to phases II and II* of pure methane and are representative of dark molecular clouds and protostars in early stages. We also tested whether the data we obtained can be applied to interpret JWST data. Methods. Laboratory reference spectra were obtained with the ISEAge setup via Fourier transform infrared spectroscopy in transmission mode. A weighted $\chi^2$ minimization was used for the fitting. Results. We present infrared spectra with corresponding band strengths of pure methane and binary mixtures with methane: CH$_4$:H$_2$O, CH$_4$:CO$_2$, CH$_4$:CH$_3$OH, and CH$_4$:NH$_3$ at 6.7 K and 10 K. They show an increase of 20% in mixtures compared to the commonly used 10 K band strength value of pure methane. We also tested whether the spectra can be used on open JWST data by probing the spatial distribution of methane in B335. We also present additional experiments concerning the phase transition of methane between phase II* and phase II. Conclusions. Our results reveal distinct spectral features for methane in non-H$_2$O environments that enable a more accurate interpretation of JWST observations. The dataset of spectra is publicly available on Zenodo and can be used for fitting JWST data.
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All authors Varvara Karteyeva, Ruslan Nakibov, Igor Petrashkevich, Mikhail Medvedev, Anton Vasyunin

Solar and Stellar Astrophysics

Seismic detection of core magnetic fields in red giants using the gravity offset

Matisse Villate, Sébastien Deheuvels and Jérôme Ballot

Magnetic fields are known to efficiently redistribute angular momentum in stars. They have been recently measured in the cores of red giant stars using asteroseismology. It was shown that core magnetic fields, if unaccounted for, can bias the measurements of the gravity offset $\epsilon_g$, which is otherwise well characterised for red giants. Exploiting this bias as a way to detect magnetic fields in the cores of red giants, we wish to increase the number of magnetic field detections in red giants, but also to establish a method that could be widely applicable to all red giants. We selected 218 Kepler red giants showing abnormal measured values of $\epsilon_g$. We used robust statistical criteria based on the expected lifetime of mixed modes to identify significant modes. We then adjusted an asymptotic expression for mixed modes to the observed frequencies, taking magnetic field and rotation into account, using Bayesian inference. We then assessed the probability of magnetic field detection and measured the magnetic field intensity using stellar models for the favourable cases. We found new magnetic red giant stars with fields ranging from 34 to 260 kG. For these stars, we measured values for $\epsilon_g$ now in agreement with the expected value. Adding these new detections to those of previous studies, we showed that the mass distribution of magnetic giants is similar to that of the complete catalogue of red giants, but different from the mass distribution of red giants with suppressed dipole modes. We also found that the core rotation of magnetic red giants follows a similar distribution as red giants in general. This could either mean that the detected fields do not have a predominant impact on the redistribution of angular momentum, or that other red giants also harbour an internal field that is currently non-detectable or has not yet been detected.
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High Energy Astrophysical Phenomena

Human versus Artificial Intelligence; various significant examples in astrophysics

A. De Rújula

In a recent arXiv posting [1] I reported the result of an experiment: asking Perplexity.ai to compare three items concerning (ordinary) Gamma Ray Burts (GRBs): the data, the standard paradigm(s) and the "Cannonball" (CB) model. Here I ask the same URL to extend this comparison to long–lasting GRBs, binary Neutron-Star mergers and their associated short–hard GRBs, low–luminosity GRBs, X–ray flashes, X–ray transients, and non–solar cosmic rays. The results of this experiment are enlightening but worrisome. Except for this abstract, two footnotes and two other references to standard [2] and CB-model [3] articles and talks, all of what follows is, verbatim, what the cited AI "opines".
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Cosmology and Nongalactic Astrophysics

Multiscale feature integration network for inpainting of full-sky CMB $B$-modes

Reyhan D. Lambaga, Vipin Sudevan and Pisin Chen

Foreground masking and incomplete sky coverage complicate CMB polarization analyses by inducing mode coupling and imperfect E/B separation, with particularly strong impact on searches for primordial $B$-modes. We present SkyReconNet-P, a convolutional neural network for inpainting CMB polarization maps that extends the SkyReconNet framework to jointly reconstruct the polarization $(Q,U)$ maps from partial-sky observations. The method combines regional processing with a hybrid design, utilizing standard convolution and dilated convolution to do a multiscale feature integration. We evaluate performance at both the map and power spectrum level using two masking scenarios: a generated random mask and the Planck 2018 common polarization inpainting mask. For both masking scenarios, SkyReconNet-P reproduces the large-scale morphology of the target maps. In power-spectrum space, we find that the reconstructed $E$-mode spectrum closely tracks the target at low multipoles, while small biases emerge at higher $\ell$. For $B$-mode, the raw reconstructed spectra exhibit a larger multipole-dependent bias, which we mitigate using a simulation-based linear calibration. We show that the calibrated $B$-mode spectrum preserve more information by comparing it with spectrum estimation using pseudo-$C_\ell$. Finally, we demonstrate cosmological parameter inference from calibrated reconstructed spectra by fitting $(r, A_{\rm lens})$ with a Gaussian bandpower likelihood, recovering posteriors consistent with injected parameters across three test ensembles down to $r \sim 10^{-3}$. These results support inpainting as a complementary route to cut-sky approaches when downstream pipelines can greatly benefit from statistically well-characterized, gap-filled polarization maps.
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Cosmology and Nongalactic Astrophysics

Zel'dovich smearing approximation of the BAO feature for model-agnostic cosmological inference

Aseem Paranjape and Ravi K. Sheth

A model-agnostic description of the baryon acoustic oscillation (BAO) feature in redshift space requires a number of ingredients. Physically, one must describe the impact of cosmological bulk flows which progressively and anisotropically smear out the feature over time. One must also model the effects of the scale dependence of tracer bias and the mode coupling between short and long scales. All of these can be incorporated using the Zel'dovich approximation alone, without reference to any particular cosmological model. On the technical front, one needs a robust, complete and cosmology-independent basis to describe the shape of the real space BAO feature in linear theory, which can then be propagated to the nonlinearly evolved, measured feature in redshift space. In this work, we describe how these ingredients – which we have systematically constructed in recent work – come together in an accurate framework capable of describing the BAO-scale pairwise measurements of state-of-the-art galaxy surveys. Using mock observations and $N$-body simulations, we show that our template-free framework can potentially produce unbiased and precise cosmological constraints for samples with realistic levels of nonlinearity. This work represents one of the final steps towards constructing a data-ready analysis framework for model-agnostic cosmological inference from the BAO feature.
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High Energy Astrophysical Phenomena · Cross-listed from stat.ML

Accelerating Posterior Inference from Pulsar Light Curves via Learned Latent Representations and Local Simulator-Guided Optimization

Farhana Taiyebah, Abu Bucker Siddik, Indronil Bhattacharjee et al. (+4 more)

Posterior inference from pulsar observations in the form of light curves is commonly performed using Markov chain Monte Carlo methods, which are accurate but computationally expensive. We introduce a framework that accelerates posterior inference while maintaining accuracy by combining learned latent representations with local simulator-guided optimization. A masked U-Net is first pretrained to reconstruct complete light curves from partial observations and to produce informative latent embeddings. Given a query light curve, we identify similar simulated light curves from the simulation bank by measuring similarity in the learned embedding space produced by pretrained U-Net encoder, yielding an initial empirical approximation to the posterior over parameters. This initialization is then refined using a local optimization procedure using hill-climbing updates, guided by a forward simulator, progressively shifting the empirical posterior toward higher-likelihood parameter regions. Experiments on the observed light curve of PSR J0030+0451, captured by NASA's Neutron Star Interior Composition Explorer (NICER), show that our method closely matches posterior estimates obtained using traditional MCMC methods while achieving 120 times reduction in inference time (from 24 hours to 12 minutes), demonstrating the effectiveness of learned representations and simulator-guided optimization for accelerated posterior inference.
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All authors Farhana Taiyebah, Abu Bucker Siddik, Indronil Bhattacharjee, Diane Oyen, Soumi De, Greg Olmschenk, Constantinos Kalapotharakos

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

MOND from Second-Order Moment Modified Acceleration and Quantum Equivalence Principle

M.J.Luo

This paper proposes a novel non-inertial quantum effect wherein particle spectra show second-order moment extra Gaussian broadening due to local short-time (non-uniform) acceleration, as well as in a deSitter spacetime background. Although the effect is too small to be detected, it provides a mechanism for the cosmological constant to enter the local kinematics of particles in the form of acceleration. The acceleration composition relation of a proper motion acceleration and the cosmological constant playing the role of a background acceleration, which is required in the Modified Newtonian Dynamics (MOND). The origin of acceleration discrepancies lies in the importance of the intrinsic second moment quantum fluctuations in the deSitter background, so that the mean value of derivative (modified effective acceleration) does not equal to the derivative of mean value (the first moment acceleration given by the unmodified Newtonian gravity). Such an interpretation of MOND as a second moment effect necessitates a quantum equivalence principle as its physical foundation, that is, extending the classical equivalence at the level of mean values (first-order moments) to the quantum equivalence at the level of second moment quantum fluctuations. The effective distance quadratic form, effective curvature and effective acceleration, etc., modified by the universal second moments all behave as if they were real geometrical or physical quantities. This effect also offers a unified framework for understanding the accelerated expansion of the universe and the anomalies in galactic rotation curves or radial acceleration.
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Astrophysics of Galaxies

Back to Normal Again: Possible Destinies of JWST overmassive SMBHs and "Little Red Dots" in the View of Shin-Uchuu Simulation

Haojie Hu, Hiroto Yanagisawa, Moka Nishigaki et al. (+3 more)

The James Webb Space Telescope (JWST) has enabled the discovery of hundreds of supermassive black holes (SMBHs) at redshifts $z\gtrsim 4-7$. A non-negligible fraction of these SMBHs are hosted in galaxies with BH-to-galaxy mass ratios ($M_{\rm BH}/M_\star$) being excessively larger than that for local SMBHs by $\sim 1-2$ dex. The origin of these “overmassive” BHs remains elusive, demanding either a heavy seed formation scenario or rapid growth of seed BHs. Their deviation from local scaling relations challenges our understanding of how SMBHs and their host galaxies coevolve across cosmic time. In this paper, we apply phenomenological modelings for BHs and galaxies to dark matter halo merger histories from N-body simulations to investigate the subsequent evolution of JWST-discovered “overmassive” SMBHs. We find that early evolution of “overmassive” SMBHs is dominated by stunted accretion leading to gradual decreases in $M_{\rm BH}/M_\star$ ratios. In contrast, less massive SMBHs experience super-Eddington accretion during their early evolution, resulting in a slow increase of mass ratios toward $M_{\rm BH}/M_\star \sim 0.01$. Convergence occurs at $M_{\rm BH}\sim 10^8~M_\odot$ with $M_{\rm BH}/M_\star \sim 0.01$. At lower redshift, nearly all SMBHs evolve onto local relations, as expected given that our models adopt empirical relations derived from low-redshift observations. This suggests that the global feedback mechanisms regulating the coevolution of $M_{\rm BH}/M_\star$ ratios are implicitly encoded in local relations in terms of star-formation rate distribution, black hole accretion rate distribution and their active (quiescent) fractions.
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All authors Haojie Hu, Hiroto Yanagisawa, Moka Nishigaki, Tomokazu Kiyota, Tomoaki Ishiyama, Ken Ohsuga

High Energy Astrophysical Phenomena

Circular orbits and observational features of the rotating Simpson-Visser black hole surrounded by a thin accretion disk

Ziyang Li, Shou-Qi Liu and Jia-Hui Huang

We present a systematic investigation of the radiative properties and optical appearance of rotating SV black holes surrounded by a thin accretion disks, and mainly analyze the influence of the regularization parameter $g$ on related observables. The results show that although the kinetic quantities and the location of the innermost stable circular orbit (ISCO) depend on the regularization parameter $g$, the radiative efficiency of the rotating SV black hole is the same as its Kerr counterpart. Within the Novikov-Thorne thin-disk model, the radiative flux, effective temperature, and spectral luminosity are studied, and by adopting observational parameters relevant to SgrA* and M87*, concrete examples of the rotating SV black holes are calculated and compared with that of the Kerr black holes. The results show that the parameter $g$ suppresses the maximum values of these quantities. In addition, using a backward ray-tracing technique, we numerically simulate the optical appearance of rotating SV black holes and analyze the corresponding intensity images, redshift and observed flux distributions. Our results show that these quantities are affected by $g$. In particular, as $g$ increases, the observed intensity is significantly suppressed and the photon ring region has remarkable increase in its width. Our findings suggest that accretion-disk-related observables may provide important avenues to distinguish rotating SV black holes and Kerr black holes, and offer theoretical guidance for future high-resolution observations.
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High Energy Astrophysical Phenomena

The Physical Properties of PS1-12sk and the implications for its Progenitor System

Kai-Li Mi, Shan-Qin Wang, Wen-Pei Gan et al. (+3 more)

PS1-12sk is a type Ibn supernova (SN) found in a host environment showing no obvious ongoing star formation, which challenges the massive star explosion scenario. We use the ejecta-circumstellar medium (CSM) interaction (CSI) and the CSI plus $^{56}$Ni models in the context of double white dwarf (WD) merger to fit the bolometric light curve (LC) of PS1-12sk, since the He emission lines at the photospheric phases indicated the interaction between the SN ejecta and He-rich CSM. We find that the CSI model failed to explain the LC, but the CSI plus $^{56}$Ni model can account for the bolometric LC. The derived masses of the two WDs and $^{56}$Ni are $\sim 0.70 M_\odot$, $\sim 0.40 M_\odot$, and $\sim 0.09\,M_\odot$, respectively. The facts that the ejecta mass ($\sim 0.984 M_\odot$) is well below the Chandrasekhar limit ($\sim 1.4 M_\odot$) and that the $^{56}$Ni mass is comparable to the $^{56}$Ni yields of the explosions of some sub-Chandrasekhar explosion models support the scenario that PS1-12sk might be from a sub-Chandrasekhar explosion induced by the merger of two low-mass WDs. The derived innermost radius ($\sim 13.81 \times 10^{12}$ cm) and the mass of the CSM ($\sim 0.116 M_\odot$) disfavor the possibility that the CSM was formed in the merger phase. We suggest that the flybys before the merger can account for the position and mass of the CSM.
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All authors Kai-Li Mi, Shan-Qin Wang, Wen-Pei Gan, Qiu-Ping Huang, Tao Wang, En-Wei Liang

Cosmology and Nongalactic Astrophysics

Quintessence with tachyonic resonance and late-time cosmic-microwave-background and gravitational-wave signals

Shun Yoshioka, Kiyotomo Ichiki, Yuichiro Tada et al. (+1 more)

Combinations of recent cosmological observations, including Dark Energy Spectroscopic Instrument (DESI), show hints of a dynamical nature for dark energy. While the data suggest the possibility of the phantom crossing, it is worth thoroughly exploring quintessence models. Given that phenomenological parametrisations of the equation-of-state parameter $w(a)$ with a sharp transitional feature fit the data well, we study the realisation of such models in quintessence. In the late Universe, the quintessence field begins to oscillate abruptly, changing the behaviour of $w$. Naturally, such a model entails tachyonic instability, and particle production modifies $w$. We perform numerical lattice simulations to study the time dependence of $w$. In addition, the violent particle production produces significant density perturbations and the stochastic gravitational-wave background, whose characteristic scale depends on the mass scale of the quintessence around the minimum of the potential. We discuss the observability of these late-time cosmological signals through cosmic microwave background, quasar astrometry, pulsar timing arrays, and other observational probes.
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All authors Shun Yoshioka, Kiyotomo Ichiki, Yuichiro Tada, Takahiro Terada

High Energy Astrophysical Phenomena

Effects of the symmetry energy slope on magnetized neutron stars

Luiz L. Lopes, Cesar V. Flores and Débora P. Menezes

In this work, we study the effect of the symmetry slope on the observables of weakly and strongly magnetized neutron stars within the chaotic magnetic field approximation. We investigate the impact of the symmetry energy slope in the equation of state, as well as on the observables of neutron stars, by calculating their masses, radii, redshifts, tidal deformabilities, and fundamental-mode gravitational-wave frequencies. We show that the effect of the magnetic field is strong on low mass stars, producing a softer equation of state and correspondingly lower values of radii. Furthermore, the magnetic field also causes a significant drop in the dimensionless tidal parameter even when the effects on the radii are small. At the end of the paper, we discuss the effects of the magnetic field in neutron stars' universal relations.
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High Energy Astrophysical Phenomena

Estimation of neutron star mass and radius of FRB 20240114A by identification of crustal oscillations

Hajime Sotani, Zorawar Wadiasingh and Cecilia Chirenti

By identifying quasi-periodic oscillations (QPOs) reported in FRB 20240114A (from the Five-hundred-meter Aperture Spherical Telescope) with neutron star crustal torsional oscillations, together with experimental constraints on the incompressibility $K_0$ of symmetric nuclear matter at saturation density, we constrain the mass and radius of an extragalactic neutron star at redshift $z\approx0.13$. Identifying the low-order QPO frequencies as fundamental oscillations, and frequencies of $567.7\,\mathrm{Hz}$ or $655.5\,\mathrm{Hz}$ (rest frame) as first overtone candidates, implies neutron star mass ranges of $1.00$–$1.55\,M_\odot$ or $1.17$–$1.76\,M_\odot$, respectively. The radius is also constrained, with a self-consistent value around $13$~km, consistent with the calculation of the NS structure within the low-mass/low-central density regime. Simultaneously, we also constrain another nuclear saturation parameter, namely the density dependence of the nuclear symmetry energy at saturation density (i.e., the slope parameter), $L$, and determine it to be $L=59.5-96.8$ MeV with $\sim 10\%$ systematic uncertainty, which is broadly consistent with previous constraints on $L$ obtained from experiments and astronomical observations. Thus, a mapping of FRB QPOs to crustal torsional modes seems reasonable. This interpretation will be tested with the discovery of additional QPOs in upcoming FRB surveys.
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Sunday 15 February

Instrumentation and Methods for Astrophysics

GW-FALCON: A Novel Feature-Driven Deep Learning Approach for Early Warning Alerts of BNS and NSBH Inspirals in Next-Generation GW Observatories

Grigorios Papigkiotis, Georgios Vardakas and Nikolaos Stergioulas

Next-generation GW observatories such as the ET and CE will detect BNS and NSBH inspirals with high SNRs and long in-band durations, making systematic early-warning alerts both feasible and scientifically valuable. Such triggers are essential for coordinating rapid electromagnetic follow-up. In this work, we introduce GW-FALCON, a novel feature-driven DL framework for early-time detection between GW signal+noise and noise-only data in next-generation detectors. Instead of feeding raw time series to CNN or more complex neural network architectures, we first extract a large set of statistical, temporal, and spectral quantities from short observational time windows using the TSFEL library. The resulting fixed-length feature vectors are then used as input to feed-forward ANNs suitable for low-latency operation. We demonstrate the method using simulated BNS and NSBH inspiral waveforms injected into colored Gaussian noise generated from the ET and CE design PSDs. We train separate ANNs on feature sets extracted from partial-inspiral windows characterized by different maximum instantaneous frequencies, enabling early-warning triggers from tens to hundreds of seconds before merger. Across all detector configurations and datasets, the resulting classifiers achieve high accuracy and detection efficiency, with ET-like networks typically reaching test accuracies of order 90% and CE-like ones exceeding 97% at low false-alarm probability. To the best of our knowledge, this work presents the first comprehensive feature-based DL detection framework for Next-generation GW observatories, connecting feature extraction from strain time series data to robust signal-noise classification within a setup that can be extended to real data and to more advanced neural network architectures.
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Earth and Planetary Astrophysics

Atmospheric constraints on GJ 1214 b from CRIRES+ and prospects for characterisation with ANDES

A. Peláez-Torres, A. Sánchez-López, C. Jiang et al. (+5 more)

In this study, we aim to constrain the atmospheric composition of GJ 1214 b using all available transits observed with the upgraded CRIRES+ spectrograph at the VLT by searching for the signatures of water vapour, methane, and carbon dioxide. We analysed eight CRIRES+ transit datasets covering the K band (1.90-2.45 microns) at a resolving power of R ~ 100,000. We used the SysRem algorithm to correct for telluric and stellar contributions and employed the cross-correlation technique with templates from petitRADTRANS to search for H2O, CH4, and CO2. Injection-recovery tests across a grid of metallicities (Z) and cloud-deck pressures (pc) were performed to quantify detection limits. We also generated predictions for ANDES observations using end-to-end simulated datasets with EXoPLORE. We detect no significant H2O, CH4, or CO2 signatures. Injection-recovery tests show that such non-detections exclude atmospheres with low-altitude clouds and moderate or low metallicities. CH4 yields the tightest empirical limits, with CO2 unexpectedly ruling out intermediate metallicities (~ 100xsolar) with clouds deeper due to its rapidly rising opacity in compressed, high-Z atmospheres. Our constraints are in line with either a high-Z or a high-altitude aerosol layer, in agreement with recent JWST inferences. The combined analysis of eight CRIRES+ datasets provides the most stringent high-resolution constraints on the atmospheric properties of GJ 1214 b to date. Simulations of a single transit observed with ANDES on the ELT predict modest improvements for H2O, a substantially expanded detectable region for CH4, and the strongest gains for CO2, making the latter a particularly effective tracer for characterising high-metallicity atmospheres in sub-Neptunes.
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All authors A. Peláez-Torres, A. Sánchez-López, C. Jiang, E. Pallé, J. Orell-Miquel, M. López-Puertas, L. T. Parker, H. Diamond-Lowe

Instrumentation and Methods for Astrophysics

Predicting New Concept-Object Associations in Astronomy by Mining the Literature

Jinchu Li, Yuan-Sen Ting, Alberto Accomazzi et al. (+2 more)

We construct a concept-object knowledge graph from the full astro-ph corpus through July 2025. Using an automated pipeline, we extract named astrophysical objects from OCR-processed papers, resolve them to SIMBAD identifiers, and link them to scientific concepts annotated in the source corpus. We then test whether historical graph structure can forecast new concept-object associations before they appear in print. Because the concepts are derived from clustering and therefore overlap semantically, we apply an inference-time concept-similarity smoothing step uniformly to all methods. Across four temporal cutoffs on a physically meaningful subset of concepts, an implicit-feedback matrix factorization model (alternating least squares, ALS) with smoothing outperforms the strongest neighborhood baseline (KNN using text-embedding concept similarity) by 16.8% on NDCG@100 (0.144 vs 0.123) and 19.8% on Recall@100 (0.175 vs 0.146), and exceeds the best recency heuristic by 96% and 88%, respectively. These results indicate that historical literature encodes predictive structure not captured by global heuristics or local neighborhood voting, suggesting a path toward tools that could help triage follow-up targets for scarce telescope time.
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All authors Jinchu Li, Yuan-Sen Ting, Alberto Accomazzi, Tirthankar Ghosal, Nesar Ramachandra

Earth and Planetary Astrophysics

Formation and Survival of Complex Organic Molecules in the Jovian Circumplanetary Disk

Olivier Mousis, Clément Petetin, Tom Benest Couzinou et al. (+2 more)

Europa, Ganymede, and Callisto are key targets in the search for habitability due to the potential presence of subsurface oceans. Detecting complex organic molecules (COMs), essential for prebiotic chemistry, is crucial to assessing their potential. Though COMs remain undetected on these moons, ESA's JUICE and NASA's Europa Clipper missions aim to fill this gap with their science payloads. This study explores the formation and transport of COMs within Jupiter's circumplanetary disk (CPD), a critical environment for the formation of the Galilean moons. Using a time-dependent model that couples the evolving CPD structure with the dynamics of icy particles of varying sizes and release times, we assess two primary COM formation pathways: thermal processing of ices and UV photochemistry. The results indicate that heating, particularly of NH3:CO2 ices, occurs efficiently before substantial irradiation, making it the dominant pathway for COM formation in the Jovian CPD. However, the relative efficiencies of these two processes are governed by particle density, disk viscosity, accretion rate, and UV flux, which collectively determine drift timescales and exposure to favorable thermodynamic environments. Existing models indicate that Europa's accretion was relatively cold and prolonged, possibly allowing some COMs to survive incorporation, whereas Ganymede and Callisto likely formed under even cooler conditions conducive to preserving COM-rich material. These results highlight the potential inheritance of complex organics by the Galilean moons and offer a framework for interpreting upcoming compositional data from JUICE and Europa Clipper.
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All authors Olivier Mousis, Clément Petetin, Tom Benest Couzinou, Antoine Schneeberger, Yannis Bennacer

Cosmology and Nongalactic Astrophysics

Gravitational waves from supercooled phase transitions and pulsar timing array signals

Jinzheng Li and Pran Nath

The recent detection of a gravitational wave background in the nano-Hertz frequency range by Pulsar Timing Array (PTA) collaborations, including NANOGrav, EPTA, and PPTA, has opened a new avenue for exploring fundamental physics in the early universe. In this work, we analyze a supercooled first-order phase transition in a hidden sector with a spontaneously broken $U(1)_X$ gauge symmetry as a source for this signal. We demonstrate that the thermal history of the hidden and visible sectors plays a crucial role in the gravitational wave power spectrum analysis. Our analysis shows that supercooled phase transitions can generate gravitational waves strong enough to explain the PTA observations while satisfying cosmological constraints from Big Bang Nucleosynthesis.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph

Measuring neutrino mixing above 1 TeV with astrophysical neutrinos

Mauricio Bustamante, Qinrui Liu and Gabriela Barenboim

We assess the potential for measuring neutrino mixing parameters at energies above 1~TeV, for the first time, using the flavor composition of TeV–PeV astrophysical neutrinos, i.e., the proportion of $\nu_e$, $\nu_\mu$, and $\nu_\tau$. Today, flavor measurements inferred from the 11.4-year IceCube Medium Energy Starting Events sample are insufficient to constrain the mixing parameters due to limited statistics, challenges in flavor identification, and uncertainty in neutrino production. Yet, upcoming multi-neutrino-telescope observations – even using only existing telescopes – may achieve sensitivity to $\theta_{23}$ and $\theta_{13}$ when combined with traditional oscillation experiments. We establish the current status and future prospects for testing the three-flavor mixing framework in the previously unexplored TeV–PeV regime and quantify the minimum detectable size of flavor-modifying beyond-Standard-Model effects, providing a roadmap for high-energy neutrino mixing measurements.
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Solar and Stellar Astrophysics

I-Band Asymptotic Giant Branch (IAGB) Stars: II. A First Estimate of their Precision and a Differential Zero Point

Wendy L. Freedman, Barry F. Madore, Taylor Hoyt et al. (+3 more)

Hubble Space Telescope (HST) observations of 92 galaxies that have a strong showing of I-band Asymptotic Giant Branch (IAGB) stars in their color-magnitude diagrams (CMDs), are used to measure the relative offset between the mean apparent I-band magnitudes of the IAGB population and the corresponding apparent I-band magnitudes of the TRGB as measured in the same frames (and CMDs) of those individual galaxies. This first exploratory, large-sample comparison is independent of any extinction (foreground or internal) that may be shared by these two populations. The marginalized luminosity functions used to determine the modal value of the IAGB population are well fit by a single, symmetric Gaussian. The difference in the two apparent magnitudes (in the sense IAGB minus TRGB) is -0.589 mag, with a combined standard deviation of +/- 0.119 mag. Adopting M_I = -4.05 mag for the TRGB stars, the modal absolute magnitude of the IAGB is then calculated to be M_I(IAGB) = -4.64 +/- 0.12 mag. The ensemble dispersion quoted above gives a standard error on the mean of +/- 0.012 mag (based on the full sample of 92 galaxies). Independently, the three geometry-based zero points for I-band AGB stars are found (in Paper I) to be M_I = -4.49 +/- 0.003~mag in the LMC (4204 stars), M_I = -4.67 +/- 0.008 mag, for the SMC (916 stars) and M_I = -4.78 +/- 0.030 mag for NGC4258 (62 stars), leading to a global zero-point (weighted) average of <M_I> = -4.64 +/- 0.15 mag (stat). The scatter found in the anchors is comparable to the scatter in the field sample discussed here, but the calibration sample is small. The application of this method to galaxies well outside of the Local Group, shows that these standard candles can readily be found and measured out to at least 9 Mpc, using already available archival data
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All authors Wendy L. Freedman, Barry F. Madore, Taylor Hoyt, In Sung Jang, Abigail J. Lee, Kayla A. Owens

High Energy Astrophysical Phenomena

Production of Jets before Neutron Star Mergers

Praveen Sharma, Slava G. Turyshev, Maxim V. Barkov et al. (+1 more)

We demonstrate that magnetospheric interactions between merging neutron stars (NSs) generate dual-jetted current outflows, analogous to the Alfvén wings observed during planetary interactions in the Solar System. Using 3D relativistic MHD simulations, we model the interaction as a conducting sphere moving through a highly magnetized plasma of the companion's magnetosphere. Unusually, the interaction operates in a regime that is relativistic yet sub-Alfvénic. Electromagnetic draping amplifies magnetic fields in a narrow layer near the stellar surface, leading to the generation of electric currents along the local magnetic field. The generation of beamed outflows enhances the instantaneous power of the pulsar-like radio and high-energy emission, produces spin/orbital modulations, and is likely to lead to observable precursor emission preceding the main gravitational wave event.
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All authors Praveen Sharma, Slava G. Turyshev, Maxim V. Barkov, Maxim Lyutikov

Solar and Stellar Astrophysics

Gaia FGK Benchmark Stars: Selecting Infrared Lines for Abundance Determination

Scarlet Elgueta, Paula Jofré, Claudia Aguilera-Gómez et al. (+7 more)

The advent of new and more powerful infrared spectrographs has significantly motivated the advancement of the study of atomic and molecular line lists and stellar atmosphere models. While optical abundance determinations rely on extensively validated line lists and modeling frameworks, infrared measurements still face larger uncertainties, largely driven by the choice of atmospheric models and the quality of the available atomic data. In this work, we aim to deliver a homogeneous and reproducible set of atomic absorption lines in the Y, J, and H bands (9800 - 18000 (Angstrom)), based exclusively on laboratory atomic data. We analyse CRIRES spectra of six Gaia FGK Benchmark Stars spanning a wide range in effective temperature, surface gravity, and chemical composition. Synthetic spectra are computed using the benchmark stellar parameters, and each transition is evaluated independently in every star through a quantitative sequence that examines line depth, saturation, blending (purity), and the agreement between observed and synthetic line profiles. We identify a set of robust atomic transitions in these bands that remain consistent across the full range of stellar parameters represented in our sample. Lines of alpha-elements such as Mg I, Si I, and Ca I, together with several Fe I transitions, satisfy all robustness criteria. Among the neutron-capture species explored, only Sr II provides lines that consistently meet our requirements. Beyond the specific list of accepted transitions, this study demonstrates that a fully quantitative, multi-criteria framework provides a transparent and reproducible foundation for near-infrared line validation as laboratory data, stellar atmosphere models, and instrumentation continue to improve.
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All authors Scarlet Elgueta, Paula Jofré, Claudia Aguilera-Gómez, Ditte Slumstrup, Álvaro Rojas-Arriagada, Ulrike Heiter, Laia Casamiquela, Manuela Zoccali, Clare Worley, Caroline Soubiran