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Physics Astrophysics

astro-ph Watch Astrophysics

Wednesday 15 October

High Energy Astrophysical Phenomena

The 2024 outburst of the neutron star LMXB EXO 0748-676: an investigation of bursts and eclipses with AstroSat

Aromal P, Unnati Kashyap, Manoneeta Chakraborty et al. (+3 more)

We present a detailed analysis of the Type-I (thermonuclear) X-ray bursts and eclipses observed from the neutron star low-mass X-ray binary (LMXB) EXO 0748–676 with AstroSat during the second known outburst of the source following a 16-year-long quiescence period. We detect three thermonuclear X-ray bursts, with two displaying simultaneous coverage in the soft X-rays. Simultaneous UV observations show evidence of reprocessed burst emissions in the far-ultraviolet band. The time-resolved spectral analysis reveals the photospheric radius expansion (PRE) nature for two bursts. We estimate the distance to the source to be $7.42\pm0.53$ kpc using the peak flux of PRE. Notably, one of the bursts exhibited a secondary peak, $\sim30$ s after the primary, particularly dominating in the softer X-rays, which reveals a correlation with the evolution of burst hotspot radius with no temperature dependence. The burst properties and corresponding flux values suggest that mixed H/He burning may have fueled the bursts. We also detect evidence of a soft excess during one burst, likely arising from the interaction of the burst photons with the surroundings. We uncover evidence for a hard X-ray deficit during the peak of all bursts and a hard lag of $\sim4$ s, which can be attributed to the Compton cooling of the corona by the burst photons. We also probe the temporal evolution and the energy dependence of the eclipses, which offer insights into the binary environment. Our study helps gain deeper insight into the physics of burst ignition, flame propagation, the burst-accretion interaction, and the evolution of LMXBs.
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All authors Aromal P, Unnati Kashyap, Manoneeta Chakraborty, Sudip Bhattacharyya, Thomas J. Maccarone, Vijay Choudhary

High Energy Astrophysical Phenomena

The Formation Rate and Luminosity Function of Fast X-ray transients from Einstein probe

Yizhou Guo, Houdun Zeng, Junjie Wei et al. (+4 more)

Following its launch on 2024 January 9, the Einstein Probe (EP) telescope has detected hundreds of fast X-ray transients (FXTs), yet their physical origins remain elusive. Understanding their luminosity function and formation rate is crucial for elucidating their nature. Recently, the EP team has provided the latest catalog of EP-detected FXTs. Based on this catalog, we present a model-independent nonparametric approach to derive the luminosity function and formation rate of FXTs. Our analysis reveals significant cosmological luminosity evolution, characterized by a scaling relationship of $(1+z)^{3.58}$. After accounting for this evolution, we establish that the local luminosity function is best represented by a broken power law, with a break luminosity of $(4.17 \pm 0.34) \times 10^{46}$ erg/s. The formation rate exhibits a broken power law as $\rho(z) \propto (1+z)^{-4.25}$ at $z \lessapprox 0.9$ and $\rho(z) \propto (1+z)^{-0.26}$ at $z \gtrapprox 0.9$, yielding a local rate of approximately $153.8_{-95.1}^{+249.4}$ Gpc$^{-3}$ yr$^{-1}$. This rate is higher than that of long gamma-ray bursts (LGRBs). Our findings indicate that a component of FXTs is associated with LGRBs.
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All authors Yizhou Guo, Houdun Zeng, Junjie Wei, Hao Zhou, Zhiping Jin, Xuefeng Wu, Daming Wei

Earth and Planetary Astrophysics

Investigating the Formation of Planets Interior to in situ Hot Jupiters

Devansh Mathur and Juliette Becker

The population of hot Jupiters with adjacent planetary companions is small but growing, and inner companions appear to be a nearly ubiquitous outcome within this subset of the exoplanet census. While most hot Jupiters are believed to form via tidal migration, the presence of adjacent companions is not easily explained by this formation mechanism, requiring consideration of additional formation mechanisms such as disk migration and in situ formation. In this work, we explore the possibility of in situ formation for both hot Jupiters and their interior companions. Using numerical simulations performed with the N-body integrator REBOUND, we investigate the growth of interior companions under various assumptions about disk conditions and hot Jupiter final orbital positions. Our results show that if a sufficiently high density of planetary embryos is transported to short orbital radii, it is feasible for both hot Jupiters and their interior companions to form in situ, providing a viable explanation for a subset of observed planetary architectures.
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Cosmology and Nongalactic Astrophysics

Euclid: Modelling observational effects in cluster counts and cluster clustering

A. Fumagalli, M. Costanzi, T. Castro et al. (+168 more)

This study explores the impact of observational and modelling systematic effects on cluster number counts and cluster clustering and provides model prescriptions for their joint analysis in the context of the Euclid survey. Using 1000 Euclid-like cluster catalogues, we investigated the effect of systematic uncertainties on cluster summary statistics and their auto- and cross-covariance, and performed a likelihood analysis to evaluate their impact on cosmological constraints, with a focus on the matter density parameter, $\Omega_{\rm m}$, and on the power spectrum amplitude, $\sigma_8$. Combining cluster clustering with number counts significantly improves cosmological constraints, with the figure of merit increasing by over 300 % compared to number counts alone. We confirm that the two probes are uncorrelated, and the cosmological constraints derived from their combination are almost insensitive to the cosmology dependence of the covariance. We find that photometric redshift uncertainties broaden cosmological posteriors by 20–30 %, while secondary effects such as redshift-space distortions (RSDs) have a smaller impact on the posteriors – 5 % for clustering alone, 10 % when combining probes – but can significantly bias the constraints if neglected. We show that clustering data below $60\,h^{-1}\,$Mpc provides additional constraining power, while scales larger than the acoustic oscillation scale add almost no information on $\Omega_{\rm m}$ and $\sigma_8$ parameters. The RSDs and photo-$z$ uncertainties also influence the number count covariance, with a significant impact of about 15–20 % on the parameter constraints.
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All authors A. Fumagalli, M. Costanzi, T. Castro, A. Saro, S. Borgani, M. Romanello, F. Marulli, E. Tsaprazi, P. Monaco, B. Altieri, A. Amara, L. Amendola, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, A. Biviano, E. Branchini, M. Brescia, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, J. Carretero, S. Casas, 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, A. M. Di Giorgio, H. Dole, M. Douspis, F. Dubath, C. A. J. Duncan, X. Dupac, S. Dusini, S. Escoffier, M. Farina, R. Farinelli, F. Faustini, S. Ferriol, F. Finelli, P. Fosalba, N. Fourmanoit, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, L. Guzzo, S. V. H. Haugan, W. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, B. Joachimi, E. Keihänen, S. Kermiche, A. Kiessling, 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, O. Marggraf, M. Martinelli, N. Martinet, R. J. Massey, E. Medinaceli, S. Mei, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan, J. J. Mohr, A. Mora, M. Moresco, L. Moscardini, E. Munari, R. Nakajima, 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, C. Rosset, R. Saglia, Z. Sakr, A. G. Sánchez, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, A. Secroun, E. Sefusatti, G. Seidel, M. Seiffert, S. Serrano, P. Simon, C. Sirignano, G. Sirri, A. Spurio Mancini, L. Stanco, J. Steinwagner, P. Tallada-Crespí, D. Tavagnacco, A. N. Taylor, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, A. Veropalumbo, Y. Wang, J. Weller, G. Zamorani, F. M. Zerbi, E. Zucca, C. Burigana, L. Gabarra, M. Maturi, C. Porciani, V. Scottez, M. Sereno, M. Viel

Instrumentation and Methods for Astrophysics

Design of an Imaging Air Cherenkov Telescope array layout with differential programming

Cyril Alispach, Matthieu Heller and Teresa Montaruli

Current optimization of ground-based Cherenkov telescopes arrays, also called Imaging Air Cherenkov Telescope (IACT) arrays, relies on brute-force human-driven approaches based on large simulations requiring both high amount of storage and long computation time. To explore the full phase space of telescope positioning of a given array even more simulations would be required. To optimize any array layout, we explore the possibility of developing a differential program with surrogate models of IACT arrays based on high-level instrument response functions (IRFs). The simulation time of a single telescope to a cosmic-ray event can be significantly reduced with its instrument response function or with generative models. However, it is not straight forward to model the array of telescopes from a set of single telescope surrogate models as the array is a stereoscopic imaging system. The complexity increases as well if the telescopes in the array are of different types. Additionally, the optimum of the array layout depends on the scientific use case. Current array layout optimization are obtained by minimizing the sensitivity of the array, a metric that depends on several high-level parameters such as the trigger efficiency, the energy and angular resolution, as well as the background rejection capability. The variety of telescopes types in IACT arrays, such as in the Cherenkov Telescope Array Observatory (CTAO), not only extends the sensitive energy range but also allows for cross-calibration of the instruments. Therefore, the optimal array layout is not only which minimizes sensitivity but also which reduces the systematic uncertainties. We focus on the optimization of a telescope array based on the SST-1M IACTs in Hanle, Ladakh India aiming at building a generic optimization pipeline for future ground-based cosmic-ray observatories
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Instrumentation and Methods for Astrophysics

A New Method for Aperture Masking Interferometric Imaging: Demonstration with the JWST

Christopher Carilli, Bojan Nikolic, Laura Torino et al. (+2 more)

We present a new method for aperture masking interferometric (AMI) imaging at near-IR wavelengths using radio astronomical techniques. The method starts with derivation of interferometric visibilities from a Fourier transform of the interferograms. An iterative joint optimization process is then employed, using self-calibration of the interferometric element-based complex voltage gains (i.e. electric fields), and CLEAN deconvolution to obtain the source structure. We demonstrate the efficacy of the method using the NIRISS aperture masking interferometer on the James Webb Space Telescope (JWST) at 4.8~$\mu$m and 3.8~$\mu$m. Due to a number of effects (the large pixel size, charge migration, near-field optics), the method also requires an initial visibility-based amplitude normalization using observations of a well know point-source calibration star. We employ early science observations of the dusty binary Wolf-Rayet star WR137. Images with a dynamic range (peak/rms) of $\sim 240$ on the target, and $\sim 1000$ on the calibrator, are synthesized from a short integration. The self-calibration process determines the photon path-lengths through the optical system to each aperture using data on the target source itself, thereby representing an essentially 'real-time', precise wavefront error sensor. Four independent measures of the JWST mirror segment pistons (two wavelengths for two sources), agree to within 10~nm to 15~nm, comparable to the expected errors based on an analysis of closure phases on the calibrator star. Including a baseline-based phase correction improves the dynamic range of the final images by about 23%.
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All authors Christopher Carilli, Bojan Nikolic, Laura Torino, N. Thyagarajan, Ubaldo Iriso

Solar and Stellar Astrophysics

Recent progress on interstellar radionuclides on Earth and the Moon

Dominik Koll, Sebastian Fichter, Michael Hotchkis et al. (+7 more)

The detection of interstellar radionuclides in geological archives provides insights into nucleosynthesis in stars and stellar explosions as well as interstellar medium dynamics in the Local Bubble and the Local Interstellar Cloud. In this work, current projects to detect interstellar radionuclides with accelerator mass spectrometry will be reviewed. These projects aim to address unsolved questions regarding the timing and the origin of the influxes and to establish new radionuclides for future searches. For the first time, experimental evidence for an inhomogeneous deposition of interstellar 60Fe onEarthwill be presented and another potential source for 60Fe on Earth and the Moon, primary galactic cosmic rays, will be introduced.
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All authors Dominik Koll, Sebastian Fichter, Michael Hotchkis, Martin Martschini, Silke Merchel, Stefan Pavetich, Annabel Rolofs, Steve Tims, Sebastian Zwickel, Anton Wallner

Earth and Planetary Astrophysics

Chaotic Dynamics and Zero-Velocity Structures in the Pluto-Charon CR3BP

Abdul Wahab Jbara

Pluto and Charon are a dwarf binary system with a high mass ratio $\mu$, preventing Trojan companions. This instability creates ideal intersections for low-energy pathways that spacecraft can traverse and serves as an important test case for stability at Lagrange points for high $\mu$ binaries. This study models the Pluto-Charon system in the planar Circular Restricted Three-Body Problem (CR3BP) and compares the tadpole and horseshoe orbits of a massless particle with known low-$\mu$ orbits. Moreover, it compares the trajectories for instances where the L1 neck is opened and closed, and exhibits the corresponding zero-velocity curves; RK4 integration was used to update the position and velocity of the particle. The simulations consistently showed chaotic and unpredictable trajectories, where small changes in initial parameters could completely alter the results; trajectories displayed the influence of higher values of $\mu$ on the stability of binary systems. These findings confirm that Pluto-Charon cannot host long-lived Trojan companions and instead behaves as a system of chaotic transport. Future work could extend the study to include the spatial or elliptic three-body problem, further refining the understanding of instability in high-$\mu$ binaries.
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Cosmology and Nongalactic Astrophysics

Probing Primordial black holes with the distortion of Stochastic Gravitational Wave Background

Mingqi Sun, Kai Liao and Xi-Long Fan

The stochastic gravitational-wave background (SGWB), arising from the incoherent superposition of numerous compact binary coalescences, serves as a powerful probe of both astrophysical populations and fundamental physics. In this work, we investigate the influence of gravitational lensing on the SGWB, focusing on primordial black holes (PBHs) as potential lenses. Assuming PBHs as dark matter candidates with a broad cosmic distribution, we show that their lensing optical depth can be significantly enhanced, producing pronounced effects with relative deviations at the 10^-1 level. By systematically varying the PBH mass (M_PBH) and abundance (f_PBH), we demonstrate that the mass predominantly determines the frequency-dependent diffraction features of the spectrum, while the abundance primarily amplifies the overall lensing-induced deviation. Although the SGWB from binary black holes has not yet been observed, our analytical results provide theoretical insight into the possible imprint of lensing on its spectrum and suggest that future detections could offer a novel avenue to constrain dark matter scenarios.
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Cosmology and Nongalactic Astrophysics

Examining a new form of non-standard dark matter using DESI DR2 data

Yan-Hong Yao, Yi-Hao Shen, Tian-Nuo Li et al. (+2 more)

In this work, we propose a non-standard dark matter (NSDM) model in which the equation of state (EoS) of dark matter (DM) is parameterized as $w_{\rm dm} = w_2 a^2$, and this DM model is motivated by the idea that DM must become cold dark matter (CDM) in the neighborhood of the scale factor $a = 0$, which implies that both the EoS of DM, $w_{\rm dm}$, and its derivative with respect to the scale factor, ${\rm d}w_{\rm dm}/{\rm d}a$, vanish at $a = 0$. By incorporating the latest cosmological datasets – including the Planck2018 Cosmic Microwave Background (CMB) distance priors, the Baryon Acoustic Oscillation measurements from the Data Release 2 of the Dark Energy Spectroscopic Instrument (DESI), together with three independent Type Ia Supernova datasets, namely the Dark Energy Survey Year 5 (DESY5) compilation, the Union3 compilation, and the PantheonPlus sample – we constrain the $\Lambda w_2$DM, $ww_2$DM, and $w_0w_aw_2$DM models, which are constructed by replacing CDM with NSDM in the $\Lambda $CDM, $w$CDM, and $w_0w_a$CDM models, respectively. We find that there is a preference for a negative DM EoS at more than the $3\sigma$ confidence level for the data combinations CMB+DESI+Union3 and CMB+DESI+DESY5. Moreover, for all data combinations, replacing CDM with NSDM in the $w$CDM and $w_0w_a$CDM models significantly reduces the probability of violating the null energy condition. Furthermore, both $ww_2$DM and $w_0w_aw_2$DM are favored over $\Lambda $CDM with a significance comparable to that of the $w_0w_a$CDM model.
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All authors Yan-Hong Yao, Yi-Hao Shen, Tian-Nuo Li, Guo-Hong Du, Yungui Gong

High Energy Astrophysical Phenomena

Evidence for Neutrino Emission from X-Ray-bright Active Galactic Nuclei with IceCube

R. Abbasi, M. Ackermann, J. Adams et al. (+429 more)

Recently, IceCube reported neutrino emission from the Seyfert galaxy NGC 1068. Using 13.1 years of IceCube data, we present a follow-up search for neutrino sources in the northern sky. NGC 1068 remains the most significant neutrino source among 110 preselected gamma-ray emitters while also being spatially compatible with the most significant location in the northern sky. Its energy spectrum is characterized by an unbroken power-law with spectral index $\gamma = 3.4 \pm 0.2$. Consistent with previous results, the observed neutrino flux exceeds its gamma-ray counterpart by at least two orders of magnitude. Motivated by this disparity and the high X-ray luminosity of the source, we selected 47 X-ray bright Seyfert galaxies from the Swift/BAT spectroscopic survey that were not included in the list of gamma-ray emitters. When testing this collection for neutrino emission, we observe a 3.3$\sigma$ excess from an ensemble of 11 sources, with NGC 1068 excluded from the sample. Our results strengthen the evidence that X-ray bright cores of active galactic nuclei are neutrino emitters.
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All authors 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, B. 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, 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, 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, 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, X. 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. Lamoureux, M. J. Larson, F. Lauber, J. P. Lazar, K. Leonard DeHolton, A. Leszczyńska, 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. Martinez-Soler, R. Maruyama, J. Mauro, F. Mayhew, F. McNally, J. V. Mead, K. Meagher, S. Mechbal, A. Medina, M. Meier, Y. Merckx, L. Merten, J. Mitchell, L. Molchany, S. Mondal, T. Montaruli, R. W. Moore, Y. Morii, A. Mosbrugger, M. Moulai, D. Mousadi, E. Moyaux, T. Mukherjee, R. Naab, M. Nakos, U. Naumann, J. Necker, L. Neste, M. Neumann, H. Niederhausen, M. U. Nisa, K. Noda, A. Noell, A. Novikov, A. Obertacke, V. O'Dell, A. Olivas, R. Orsoe, J. Osborn, E. O'Sullivan, V. Palusova, H. Pandya, A. Parenti, N. Park, V. Parrish, E. N. Paudel, L. Paul, C. Pérez de los Heros, T. Pernice, T. C. Petersen, J. Peterson, M. Plum, A. Pontén, V. Poojyam, Y. Popovych, M. Prado Rodriguez, B. Pries, R. Procter-Murphy, G. T. Przybylski, L. Pyras, C. Raab, J. Rack-Helleis, N. Rad, M. Ravn, K. Rawlins, Z. Rechav, A. Rehman, I. Reistroffer, E. Resconi, S. Reusch, C. D. Rho, W. Rhode, L. Ricca, B. Riedel, A. Rifaie, E. J. Roberts, M. Rongen, A. Rosted, C. Rott, T. Ruhe, L. Ruohan, D. Ryckbosch, J. Saffer, D. Salazar-Gallegos, P. Sampathkumar, A. Sandrock, G. Sanger-Johnson, M. Santander, S. Sarkar, J. Savelberg, M. Scarnera, P. Schaile, M. Schaufel, H. Schieler, S. Schindler, L. Schlickmann, B. Schlüter, F. Schlüter, N. Schmeisser, T. Schmidt, F. G. Schröder, L. Schumacher, S. Schwirn, S. Sclafani, D. Seckel, L. Seen, M. Seikh, S. Seunarine, P. A. Sevle Myhr, R. Shah, S. Shefali, N. Shimizu, B. Skrzypek, R. Snihur, J. Soedingrekso, A. Søgaard, D. Soldin, P. Soldin, G. Sommani, C. Spannfellner, G. M. Spiczak, C. Spiering, J. Stachurska, M. Stamatikos, T. Stanev, T. Stezelberger, T. Stürwald, T. Stuttard, G. W. Sullivan, I. Taboada, S. Ter-Antonyan, A. Terliuk, A. Thakuri, M. Thiesmeyer, W. G. Thompson, J. Thwaites, S. Tilav, K. Tollefson, S. Toscano, D. Tosi, A. Trettin, A. K. Upadhyay, K. Upshaw, A. Vaidyanathan, N. Valtonen-Mattila, J. Valverde, J. Vandenbroucke, T. Van Eeden, N. van Eijndhoven, L. Van Rootselaar, J. van Santen, J. Vara, F. Varsi, M. Venugopal, M. Vereecken, S. Vergara Carrasco, S. Verpoest, D. Veske, A. Vijai, J. Villarreal, C. Walck, A. Wang, E. H. S. Warrick, C. Weaver, P. Weigel, A. Weindl, J. Weldert, A. Y. Wen, C. Wendt, J. Werthebach, M. Weyrauch, N. Whitehorn, C. H. Wiebusch, D. R. Williams, L. Witthaus, M. Wolf, G. Wrede, X. W. Xu, J. P. Yanez, Y. Yao, E. Yildizci, S. Yoshida, R. Young, F. Yu, S. Yu, T. Yuan, A. Zander Jurowitzki, A. Zegarelli, S. Zhang, Z. Zhang, P. Zhelnin, P. Zilberman

Solar and Stellar Astrophysics

ON the stability of triangular Lagrangian points in the spatial restricted three-body problem

Stepan P. Sosnitskii

In the present paper, which is a development of an earlier study by the author \cite{Sosnitskii08}, we consider the stability of triangular libration points in the spatial circular restricted three-body problem and improve the result of author's work \cite{Sosnitskii08}. Unlike \cite{Sosnitskii08}, where the instability of libration points was established on the base of reduced approximate equations, we succeeded in this paper to use a new approach that made it possible to prove the instability of triangular libration points on the base of a closed complete system of equations. The relationship between the Lyapunov stability and Birkhoff stability (formal stability) is also discussed
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Solar and Stellar Astrophysics

Abundance of heavy r-process elements in CEMP-rs stars: The role of the i-process

A. M. Riyas, D. Karinkuzhi, S. Van Eck et al. (+6 more)

Carbon-enhanced metal-poor (CEMP) stars are ancient stars enriched in carbon and heavy elements. Some of these stars exhibit enhanced s-process and/or r-process elements, hence are classified as CEMP-s, CEMP-rs, or CEMP-r. This classification is challenging due to the limited availability of heavy element abundances, particularly among r-process elements. Heavy r-process elements such as terbium, holmium, thulium, ytterbium, lutetium, tantalum, and iridium have rarely been measured because their sensitive lines are located in the ultraviolet. However, they provide sensitive diagnostics of the s-, r-, and i- nucleosynthetic processes. In this work, we aim to obtain a secure classification of CEMP-s and -rs stars and investigate whether the i-process can account for the measured abundance patterns in CEMP-rs stars. We derive the abundance profiles, notably for twelve heavy r-elements, including, in some cases, tantalum, using high-resolution UVES spectra of seventeen CEMP-s and -rs stars. Based on indicators such as the [s/r] abundance ratio or the model-independent 'abundance distance', nine stars are confirmed as CEMP-rs and six as CEMP-s. The classification of two objects remains uncertain. The i-process satisfactorily reproduces the abundance patterns of CEMP-rs stars. However, larger samples are needed to confirm trends with metallicity and clarify how CEMP-rs stars differ from CEMP-s stars.
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All authors A. M. Riyas, D. Karinkuzhi, S. Van Eck, A. Choplin, S. Goriely, L. Siess, M. V. Keerthy, A. Jorissen, T. Merle

High Energy Astrophysical Phenomena

Relativistic reflection within an extended hot plasma geometry

Alexey D. Nekrasov, Thomas Dauser, Javier A. Garcia et al. (+9 more)

The reflection of X-rays at the inner accretion disk around black holes imprints relativistically broadened features in the observed spectrum. Aside from the black hole properties and the ionization and density of the accretion disk, these features also depend on the location and geometry of the primary source of X-rays, often referred to as the corona. We present a fast general relativistic model for spectral fitting of a radially extended, ring-like corona above the accretion disk. A common approach used to explain observed X-ray reflection spectra is the lamp post geometry, which assumes a point-like source on the rotational axis of the black hole. While it is typically able to explain the observations, this geometric model does not allow for any constraint to be placed on the radial size of the corona. We therefore extended the publicly available relativistic reflection model relxill by implementing a radially extended, ring-like primary source. With the new RELXILL model allowing us to vary the position of the primary source in two dimensions, we present simulated line profiles and spectra and discuss the implications of carrying out a data fitting, in comparison to the lamp post model. We applied this extended RELXILL model to XMM-Newton and NuSTAR data of the radio-quiet Seyfert-2 active galactic nucleus (AGN) ESO 033-G002. The new model describes the data well and we are able to constrain the distance of the source to the black hole to be less than three gravitational radii, while the angular position of the source is poorly constrained. We show that a compact, radially extended corona close to the innermost stable circular orbit is able to explain the observed relativistic reflection as well as the lamp post corona does. This model has been made freely available to the community.
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All authors Alexey D. Nekrasov, Thomas Dauser, Javier A. Garcia, Dominic J. Walton, Christian M. Fromm, Andrew J. Young, Fergus J. E. Baker, Amy M. Joyce, Ole Koenig, Stefan Licklederer, Julia Haefner, Joern Wilms

Cosmology and Nongalactic Astrophysics

Global linear analysis of the magneto-thermal instability in a stratified spherical model of the intracluster medium

J.M. Kempf and H. Latter

The buoyancy stability properties of the ICM are modified because of the anisotropic transport of heat along the magnetic field lines. This feature gives rise to the MTI when the temperature gradient is aligned with the gravity, which occurs in the outskirts of galaxy clusters. Most previous linear analyses of the MTI adopted a local, Boussinesq approach. However, the conduction length, which sets the characteristic length scale of the MTI, might be a non-negligible fraction of the scale height in the ICM. We want to assess the impact of locality assumptions on the linear physics of the MTI. Another goal is to unveil the deeper connections between these global MTI modes and their MRI counterparts in accretion discs. Our third objective is to provide a new benchmark against which any numerical code implementing the Braginskii heat flux in spherical geometry can be tested. We perform a global linear analysis of the MTI in a spherical stratified model of the ICM. We use a combination of analytical results, corroborated by numerical results obtained with both a pseudo-spectral solver and IDEFIX, to better explain the physics of the global MTI modes. We obtain scaling laws and approximate expressions for the growth rates of the global modes. We show that the associated functions are confined within an inner region, limited by a turning point, where the mode is allowed to grow. The most unstable local MTI modes correspond to the portion of the global mode localised near the turning point. This phenomenology is similar to that of the global MRI modes. Finally, direct simulations successfully reproduce the global MTI modes and their growth rates, with errors smaller than 1%. Overall, this study provides us with new insights on the linear theory of the global MTI in the ICM, and a useful numerical test bench for any astrophysical fluid dynamics code embedding anisotropic heat flux.
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Astrophysics of Galaxies

Old open clusters NGC 188 and M 67 in Gaia DR3

Anton F. Seleznev and Maxim V. Kulesh

We performed a statistical study of two old open clusters NGC 188 and M 67 using Gaia DR3 data. No tidal tails of the clusters were detected, which most likely had been destroyed when the cluster passed through the Galactic plane. The size estimates of the clusters depend on the range of astrometric parameters and stellar magnitudes of the stars used for star counts. The mass spectra of two clusters differ significantly. NGC 188 shows a deficit of low-mass stars compared to M 67. In the halo region of NGC 188 (compared to the core region of the cluster), there is a relative excess of the low-mass stars (just as in the case of M 67) and a deficit of stars in the mass range from 0.66 to 0.9 solar masses. Comparison with the Hunt & Reffert samples showed that almost all the stars from these samples are contained among the stars we selected for counting. Moreover, the group probability of these stars belonging to clusters, estimated by the uniform background method, is higher than 60%. It is shown that the velocity dispersion of single stars (selected according to the `stellar magnitude – color index' diagrams) is significantly smaller than the velocity dispersion of unresolved binary stars.
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High Energy Astrophysical Phenomena

Monte Carlo simulation of the Compton scattering and disk reflection of a cylinder with hot electrons moving away from a black hole

Wei Meng, Yuan You, Shuang-Nan Zhang et al. (+1 more)

For accreting black holes (BHs), the lamp-post scenario is a simple and popular model: a hot and point-like corona is located above the black hole, irradiating the accretion disk with hard X-ray radiation, which is believed to be generated by inverse Compton scattering in the corona. Although the lamp-post model successfully explains the disk reflection component, it fails to address the origin of seed photons and the geometry of the hot corona, because this model simplistically treats the corona as a point-like source generating a cutoff powerlaw spectrum. In this paper, we make simulations on a possible physical realization of the lamp-post scenario: the shape of the scattering zone is set to be a cylinder, corresponding to the jet base near a BH. The source of seed photons in this system is assumed to be the multicolor blackbody radiation of the accretion disk. In our simulations, the Compton scattering process is simulated with a custom Monte Carlo program based on the Geant4 package and the disk reflection process is simulated with the xilconv model in XSPEC. Our simulation results have confirmed that the relativistic motion of the jet can weaken or even completely suppress the reflection of the accretion disk, and simultaneously, the Comptonization of disk photons in the jet can still make a major contribution to the observed X-ray spectrum in high energy range. We discuss the implications of our simulation results, in light of the recent observations of a very weak reflection component in the presence of a strong hard X-ray radiation from the outburst of Swift J1727.8-1613.
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All authors Wei Meng, Yuan You, Shuang-Nan Zhang, Jia-Ying Cao

Astrophysics of Galaxies

The dependence of black hole formation in open clusters on the cluster formation process

Jian-Wen Zhou

We performed N-body simulations of both individual cluster evolution and subcluster coalescence, demonstrating that cluster evolution and its outcomes strongly depend on the cluster formation process through comparisons of different gas expulsion modes and formation channels. The evolution of star clusters is significantly shaped by the gas expulsion mode, with faster expulsion producing greater mass loss. A broader degeneracy exists among initial cluster mass, gas expulsion timescale, and formation channel (monolithic vs. coalescence), which manifests in both evolutionary pathways and black hole production. In individual cluster simulations, slower gas expulsion enables progressively lower-mass clusters to retain central black holes within the tidal radius. As the gas expulsion mode transitions from fast to moderate to slow, the fraction of high-velocity stars decreases. Variations in gas expulsion mode and formation channel ultimately influence the stellar velocity distribution (within the tidal radius), and thus the expansion speed, which governs both cluster mass loss and black hole retention. Slowly expanding clusters are more likely to retain black holes and multiple systems, making them prime candidates for black hole searches with Gaia. Our results highlight the crucial influence of early gas expulsion and cluster formation mechanisms on the dynamical evolution of star clusters and black hole production. These factors should be carefully incorporated into the initial conditions of N-body simulations, which necessarily rely on input from the star formation community.
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Astrophysics of Galaxies

Discovery of red galaxy candidates at z ~ 12: Early dust growth or significant nebular emission with high-temperature stars?

Ikki Mitsuhashi, Katherine A. Suess, Joel Leja et al. (+18 more)

We report the discovery of two z ~ 12 galaxy candidates with unusually red UV slopes (betaUV ~> -1.5), and probe the origin of such colors at cosmic dawn. From Prospector fits to the UNCOVER/MegaScience dataset – deep JWST/NIRCam imaging of Abell 2744 in 20 broad- and medium-bands – we identify several new z > 10 galaxies. Medium-band data improve redshift estimates, revealing two lensed (mu ~ 3.3) z ~ 12 galaxies in a close pair with beta_UV ~> -1.5 at an UV absolute magnitude of M_UV ~ -19 mag, lying away from typical scatter on previously known MUV-betaUV relations. SED fitting with Prospector, Bagpipes, and EAZY support their high-z nature, with probability of low-z interlopers of p(z < 7) < 10%. The potential low-z interlopers are z ~ 3 quiescent galaxies (QGs), but unexpected to be detected at the given field of view unless z ~ 3 QG stellar mass function has a strong turn up at log Mstar/Msun ~ 9. Unlike typical blue high-redshift candidates (beta_UV ~< -2.0), these red slopes require either dust or nebular continuum reddening. The dust scenario implies Av ~ 0.8 mag, which is larger than theoretical predictions, but is consistent with a dust-to-stellar mass ratio (log M_dust/M_star ~ -3). The nebular scenario demands dense gas (log nH /cm^3 ~ 4.0) around hot stars (log Teff [K] ~ 4.9). Spectroscopic follow-up is essential to determine their true nature and reveal missing galaxies at the cosmic dawn.
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All authors Ikki Mitsuhashi, Katherine A. Suess, Joel Leja, Pratika Dayal, Robert Feldmann, Seiji Fujimoto, Harley Katz, Themiya Nanayakkara, Desika Narayanan, Sedona H. Price, John R. Weaver, Christina C. Williams, Ivo Labbe, Rachel Bezanson, Hakim Atek, Gabriel Brammer, Sam E. Cutler, Lukas J. Furtak, Richard Pan, Bingjie Wang, Katherine E. Whitaker

Earth and Planetary Astrophysics

Prospects for the Crossing of Comet 3I/ATLAS's Ion Tail

Samuel R. Grant and Geraint H. Jones

During October - November 2025, interstellar comet 3I/ATLAS, will pass upstream of the Europa Clipper and Hera spacecraft. Here, we identify two potential opportunities for in-situ observations of 3I's ion tail by immersion, facilitated by the close alignment between the comet's hyperbolic trajectory with the ecliptic plane. During the period 30 October - 6 November 2025, it is predicted that Europa Clipper will potentially be immersed within the ion tail of 3I/ATLAS, providing the opportunity to detect the signatures of an interstellar comet's ion tail. Characteristic changes to the solar wind are also expected to be observed; a magnetic draping structure associated with the comet may be identifiable. It is further predicted that spacecraft Hera will possibly be immersed within the ion tail of 3I/ATLAS during the period 25 October - 1 November 2025.
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High Energy Astrophysical Phenomena

Some problems associated with the standardization of the light curve of type 1a supernovae

A. P. Mahtessian, G. S. Karapetian, H. F. Khachatryan et al. (+4 more)

We show that the parameters used to standardize the luminosity of Type 1a supernovae in the SALT2 and SiFTO models are strongly dependent on the redshift z. Consequently, when standardized with increasing z, the average absolute magnitudes of Type 1a supernovae are artificially increased. This means that for a given apparent magnitude they are, on average, assigned larger distances than they actually are, creating the appearance of their recession with acceleration and requiring the introduction of the concept of antigravity (dark energy) to explain it. We also show that after standardization, Type 1a supernovae cease to be standard candles. We therefore argue that such a standardization is not suitable for measuring the distances to Type 1a supernovae, and hence the accelerating expansion of the Universe is called into question.
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All authors A. P. Mahtessian, G. S. Karapetian, H. F. Khachatryan, M. A. Hovhannisyan, L. A. Mahtessian, L. E. Byzalov, J. M. Sarkissian

Astrophysics of Galaxies

Dependency of the Bar Formation Timescale On The Halo Spin

Bin-Hui Chen, Sandeep Kumar Kataria, Juntai Shen et al. (+1 more)

Bars are among the most prominent structures in disk galaxies. While the widely accepted swing-amplification theory provides a qualitative framework for their formation, the detailed physical processes remain incompletely understood. Previous studies have shown that the bar formation timescale in isolated galaxies depends exponentially on the disk mass fraction (the so-called "Fujii relation") and linearly on disk hotness and thickness. However, the influence of dark matter halo spin on bar formation has not been systematically investigated. In this work, we construct a suite of $N$-body models of disk and halo with varying disk mass fractions and amounts of random motions. By introducing prograde and retrograde spins in the dark matter halo, we explore how halo spin modifies the established empirical relations governing bar formation timescales. We find that these relations remain valid in both prograde and retrograde halo spin models. For rapid bar formation (short timescale), the effect of halo spin is nearly negligible. In contrast, for moderately slow bar formation, prograde (retrograde) halo spin tends to accelerate (suppress) bar onset. In cases of extremely slow bar formation, halo spin introduces a stronger but more stochastic influence. These trends might arise from the exchange of angular momentum between the stellar disk and the dark matter halo.
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All authors Bin-Hui Chen, Sandeep Kumar Kataria, Juntai Shen, Meng Guo

Astrophysics of Galaxies

The Dependency of Bar Formation Timescale on Disk Mass Fraction, Toomre $Q$, and Scale Height

Bin-Hui Chen and Juntai Shen

Bars are one of the most prominent galactic structures. The classical swing-amplification theory can qualitatively describe the spontaneous bar instability of stellar disks. Still, it cannot quantify the bar formation process or explain why some disk galaxies do not have a bar. Recent studies found that the bar formation timescale depends exponentially on the disk mass fraction of the host galaxy (dubbed as "Fujii relation"), but they only explored a limited parameter space, where the physical effects of Toomre $Q$ (local disk stability parameter) and disk scale height of the host galaxies are not fully explored. In this work, we check the robustness of the Fujii relation in a higher-dimensional parameter space of disk mass fraction, Toomre $Q$, and scale height. We find that the Fujii relation holds for disk galaxies with physically reasonable Toomre $Q$ and scale height. Furthermore, the bar formation timescale also approximately linearly depends on both Toomre $Q$ and scale height, with a more prolonged bar formation in a hotter or thicker disk. We propose an empirical relation to combine the dependency of the bar formation timescale on the three parameters. Based on the empirical relation and recent observations, we estimate that the bar formation timescale in pure stellar disks ranges from $0.20_{-0.06}^{+0.09}~\mathrm{Gyr}$ to $12.20_{-2.80}^{+3.37}~\mathrm{Gyr}$ or even significantly beyond the Hubble timescale in some extreme cases.
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Astrophysics of Galaxies · Cross-listed from physics.flu-dyn

Statistical properties of compressible isothermal turbulence from sub- to supersonic conditions

F. Thiesset and C. Federrath

This paper investigates the statistical properties of isothermal turbulence in both the subsonic and supersonic regimes. The focus is on the influence of the Mach number ($Ma$) and the Reynolds number ($Re$) on both the space-local and scale-dependent fluctuations of relevant gas variables, the density, velocity, their derivatives, and the kinetic energy. We carry out hydrodynamical simulations with explicit viscosity and therefore controlled $Re$. We confirm previous work that the probability density functions (PDFs) of the gas density are approximately log-normal and depend on $Ma$. In contrast, derivatives of the density and velocity field are sensitive to $Re$, with the probability of extreme events growing with $Re$. The PDFs of the density gradient and velocity divergence (dilatation) exhibit increasingly heavy tails with growing $Ma$, signalling enhanced internal intermittency. At sufficiently high $Ma$, the statistics of dilatation are observed to saturate at a level determined solely by $Re$, suggesting that turbulent dilatation becomes limited by viscous effects. We also examine the scale-by-scale distribution of kinetic energy through a compressible form of the Kármán-Howarth-Monin (KHM) equation. In the intermediate range of scales, a marked difference is found between subsonic and supersonic turbulence: while Kolmogorov-like scaling applies in the sub- and transonic regimes, supersonic turbulence aligns more closely with Burgers turbulence predictions. The analysis of individual terms in the KHM equation highlights the role of the pressure-velocity coupling as an additional mechanism for converting kinetic energy from large to small scales. Moreover, the contributions of the KHM terms exhibit non-monotonic behaviour with increasing $Ma$, with dilatational effects becoming more pronounced and acting to oppose the cascade of kinetic energy.
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Astrophysics of Galaxies

Galaxy Protoclusters as Drivers of Cosmic Reionization: I. Bubble Overlap at Redshift z ~ 7 in LAGER-z7OD1

Crystal L. Martin, Weida Hu, Isak G. B. Wold et al. (+17 more)

Since the launch of JWST, the sample size of reionization-era Lyman-alpha-emitters (LAEs) has been steadily growing; yet inferences about the neutral hydrogen fraction in the intergalactic medium exhibit increasing variance at redshift z ~ 7, possibly indicating significant field-to-field fluctuations in the progression of cosmic reionization. In this paper, we present new JWST/NIRSpec and Keck/LRIS spectra of nine LAEs in the redshift z ~ 7 protocluster, LAGER-z7OD1. Measurements of Lyman-alpha-transmission and Lyman-alpha velocity offset along multiple sightlines map the Lyman-alpha damping wing optical depth across the galaxy overdensity. In the standard context of inside-out ionization, we estimate radii of ionized bubbles (R(min) = 0.07 - 0.69 Mpc) based on the distance from each LAE to the first neutral patch along the sightline. The resulting 3D topology reveals three distinct sub-clusters where the ionized bubbles are approaching overlap. Five of the nine LAEs plausibly ionized their bubbles, a few bursts of star formation and a modest escape fraction are sufficient. We demonstrate, however, that the actual ionized volumes are likely larger, at least R(ism) = 0.42 - 1.29 Mpc, based on an empirical model for interstellar attenuation of Lyman-alpha. Modeling galactic attenuation of Lyman-alpha significantly increases the inferred intergalactic transmission (thus enlarging the ionized pathlength). The errorbars on the reddening correction allow fully overlapping bubbles, and our results are consistent with accelerated reionization in the protocluster.
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All authors Crystal L. Martin, Weida Hu, Isak G. B. Wold, Andreas Faisst, Cristobal Moya-Sierralta, Sangeeta Malhotra, James E. Rhoads, Luis Felipe Barrientos, Yuichi Harikane, Leopoldo Infante, Anton Koekemoer, Jorge Gonzalez Lopez, Masami Ouchi, Junyan Xu, Jiayang Yang, L. Y. Aaron Yung, John R. Weaver, Henry McCracken, Zhenya Zheng, Junxian Wang

Cosmology and Nongalactic Astrophysics

Numerical Cosmology

Romain Teyssier

In these lecture notes, we describe the current state-of-the-art for numerical simulations of large-scale structure and galaxy formation. Numerical simulations play a central role in the preparation and the exploitation of large-scale galaxy surveys, in which galaxies are the fundamental observational objects. We first describe basic methods for collisionless N-body dynamics that enable us to model dark matter accurately by solving the Vlasov-Poisson equations. We then discuss simple methods to populate dark matter halos with galaxies, such as Halo and Sub-halo Abundance Matching techniques and baryonification techniques for capturing baryonic effects on the matter distribution. We finally describe how to model the gas component by solving the Euler-Poisson equations, focusing on the foundational assumptions behind these equations, namely local thermo-dynamical equilibrium, and the nature of the truncation errors of the numerical scheme, namely numerical diffusion. We show a few examples of simulations of a Milky-Way-like halo without cooling, with cooling and with star formation. We finally describe different subgrid prescriptions recently developed to model star formation, supernovae feedback and active galactic nuclei and how they impact cosmological simulations.
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Cosmology and Nongalactic Astrophysics

Strong Progenitor Age-bias in Supernova Cosmology. II. Alignment with DESI BAO and Signs of a Non-Accelerating Universe

Junhyuk Son, Young-Wook Lee, Chul Chung et al. (+2 more)

Supernova (SN) cosmology is based on the key assumption that the luminosity standardization process of Type Ia SNe remains invariant with progenitor age. However, direct and extensive age measurements of SN host galaxies reveal a significant (5.5{\sigma}) correlation between standardized SN magnitude and progenitor age, which is expected to introduce a serious systematic bias with redshift in SN cosmology. This systematic bias is largely uncorrected by the commonly used mass-step correction, as progenitor age and host galaxy mass evolve very differently with redshift. After correcting for this age-bias as a function of redshift, the SN dataset aligns more closely with the w0waCDM model recently suggested by the DESI BAO project from a combined analysis using only BAO and CMB data. This result is further supported by an evolution-free test that uses only SNe from young, coeval host galaxies across the full redshift range. When the three cosmological probes (SNe, BAO, CMB) are combined, we find a significantly stronger (> 9{\sigma}) tension with the {\Lambda}CDM model than that reported in the DESI papers, suggesting a time-varying dark energy equation of state in a currently non-accelerating universe.
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All authors Junhyuk Son, Young-Wook Lee, Chul Chung, Seunghyun Park, Hyejeon Cho

High Energy Astrophysical Phenomena

Gravitational-Wave Signatures of Highly Eccentric Stellar Binary Black-Holes in Galactic Nuclei

Evgeni Grishin, Isobel M. Romero-Shaw and Alessandro A. Trani

A significant fraction of gravitational-wave mergers are expected to be eccentric in the Laser-Interferometer-Space-Antenna (LISA) frequency band, $10^{-4} - 10^{-1}$ Hz. Several LIGO-Virgo-KAGRA events show potential hints of residual eccentricity at 10 Hz, pointing to dynamical or triple origins for part of the population, where von-Zeipel-Lidov-Kozai oscillations can perturb both the eccentricity and the inclination of the binary. Moreover, the argument of pericentre, $\omega$ could be fully circulating, or librating, with a limited range for $\omega$. We use TSUNAMI, a regularised N-body code with 3.5PN corrections to identify four different orbital families: (i) circulating, (ii) small-amplitude and (iii) large-amplitude librating, and (iv) merging. We develop a new method to construct gravitational-wave waveforms using the quadrupole formula from the instantaneous acceleration in TSUNAMI. The four orbital families have distinct waveform phenomenologies, enabling them to be distinguished if observed in LISA. In particular, the properties of the tertiary companion can be inferred and serve as an independent mass measurement and distinguish field triple dynamics from galactic dynamics.
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Astrophysics of Galaxies

Galactic chemical evolution with the short-lived isotopes Mn-53, Fe-60, Hf-182, and Pu-244

Benjamin Wehmeyer, Andrés Yagüe López, Benoit Côté et al. (+3 more)

We run a three-dimensional Galactic chemical evolution (GCE) model to follow the propagation of Mn-53 from supernovae of type Ia (SNIa), Fe-60 from core-collapse supernovae (CCSNe), Hf-182 from intermediate mass stars (IMSs), and Pu-244 from neutron star mergers (NSMs) in the Galaxy. We compare the GCE of these short-lived radioactive isotopes (SLRs) to recent detections on the deep-sea floor. We find that although these SLRs originate from different sites, they often arrive conjointly on Earth.
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All authors Benjamin Wehmeyer, Andrés Yagüe López, Benoit Côté, Maria K. Pető, Chiaki Kobayashi, Maria Lugaro

High Energy Astrophysical Phenomena

Gravitational-Wave Signatures of Highly Eccentric Stellar-Mass Binary Black Holes in Galactic Nuclei

Evgeni Grishin, Isobel M. Romero-Shaw and Alessandro A. Trani

A significant fraction of compact-object mergers in galactic nuclei are expected to be eccentric in the Laser Interferometer Space Antenna (LISA) frequency sensitivity range, $10^{-4} - 10^{-1}\ \rm Hz$. Several compact binaries detected by the LIGO-Virgo-KAGRA Collaboration may retain hints of residual eccentricity at $\sim 10$ Hz, suggesting dynamical or triple origins for a significant fraction of the gravitational-wave-observable population. In triple systems, von-Zeipel-Lidov-Kozai oscillations perturb both the eccentricity and the argument of pericentre, $\omega$, of the inner black hole binary. The latter could be fully circulating, where $\omega$ cycles through $2\pi$, or may librate, with $\omega$ ranges about a fixed value with small or large variation. We use TSUNAMI, a regularised N-body code with up to 3.5 post-Newtonian (PN) term corrections, to identify four different families of orbits: (i) circulating, (ii) small and (iii) large amplitude librating, and (iv) merging orbits. We develop and demonstrate a new method to construct gravitational waveforms using the quadrupole formula utilising the instantaneous total acceleration of each binary component in TSUNAMI. We show that the four orbital families have distinct waveform phenomenologies, enabling them to be distinguished if observed in LISA. The orbits are also distinguishable from an isolated binary or from a binary perturbed by a different tertiary orbit, even if the secular timescale is the same. Future burst timing models will be able to distinguish the different orbital configurations. For efficient binary formation, about $\sim 1000$ binaries can have highly eccentric, librating orbits in the Galactic Centre.
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