Earth and Planetary Astrophysics
Dynamical environment and stability around Centaur (2060) Chiron
Gustavo Madeira, Bruno Morgado, Chrystian Pereira et al. (+3 more)
A recent
stellar occultation revealed that the Centaur (2060) Chiron hosts a broad disk extending beyond ~200 km from its centre,
embedding three ring-like structures (Chi1R, Chi2R, and Chi3R), while a tenuous outer ring (Chi4R) lies beyond the Roche limit. Here, we present a first dynamical assessment of the system's stability through numerical simulations of test particles, accounting for Chiron's triaxial figure. For an equatorial ellipticity of C22~0.02, as inferred from the most recent shape estimates, our simulations reveal a chaotic inner zone extending to ~260 km, where particle lifetimes reach up to a year, while particles beyond ~260 km can remain stable for at least a decade. These results suggest that the innermost portion of the disk is ephemeral and can only persist if continuously replenished. For lower ellipticity values (C22<0.012), however, the entire disk is located within the stable region, regardless of Chiron's mass. Under the physical parameters currently available in the literature, Chi2R is possibly linked to the 1:3
spin-orbit resonance, while Chi1R cannot be linked to the 1:2 resonance, as previously proposed, since this resonance is unstable. Instead, Chi1R and Chi3R may be associated with the 2:5 and 1:5
spin-orbit resonances, respectively. Both the 1:3 and 1:5 resonances are bifurcated, generating chaotic zones that may explain the gap in Chi2R and the longitudinal asymmetry observed in Chi3R.
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All authors Gustavo Madeira, Bruno Morgado, Chrystian Pereira, Giovana Ramon, Rafael Sfair, Felipe Braga-Ribas
High Energy Astrophysical Phenomena
Search for neutrino emission from LHAASO observed Microquasar with IceCube 10-year data
Rong-Lan Li, Hao-Ning He and Da-Ming Wei
The Large High Altitude Air Shower Observatory (LHAASO) has detected ultra-high-energy (UHE; E>100 TeV) gamma-ray emission from five microquasars, suggesting their potential as
Galactic PeV
cosmic-ray accelerators. At these energies, the Klein-Nishima effect strongly suppresses leptonic processes, making
neutrinos observation a crucial test for hadronic acceleration. We present a search for
neutrino emission from these LHAASO-identified Microquasars using ten years of IceCube
muon-track data. No significant
neutrino signal was found in either single-source or stacking analyses. Our stacking result further shows that the studied microquasars population can only account for a small fraction of the diffuse
neutrino flux along the
Galactic Plane. Finally, we demonstrate that new-generation
neutrino telescopes, such as HUN, will have the sensitivity to probe harmonic emission from these candidate PeVatrons.
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Solar and Stellar Astrophysics
DKIST resolves sub-arcsec photospheric scattering polarization
Franziska Zeuner, Luca Belluzzi, Ernest Alsina Ballester et al. (+4 more)
Scattering polarization signals offer a unique diagnostics of the physical conditions in the
solar atmosphere, in particular
magnetic fields via the Hanle effect. However, their spatial structure remains poorly constrained due to the difficulty of achieving high spatial resolution and polarimetric sensitivity simultaneously. We present the first direct observation of sub-arcsecond structuring in the linear scattering polarization of the photospheric Sr i 4607 Å\, line near the
solar disk center ($\mu$ = 0.74), obtained with the Visible Spectro- Polarimeter (ViSP) at the Daniel K. Inouye
Solar Telescope (DKIST). The data achieve about 0".2 resolution with 30 s integration and sufficient sensitivity to detect fine-scale patterns in the total linear polarization, which are evident in Sr i but absent in a nearby Fe i line that is simultaneously observed. Since this Fe i line is more Zeeman-sensitive than the Sr i 4607 Å\, this disparity confirms that the signals in the Sr i 4607 Å\, line arise from scattering. These data provide the first spatially resolved two-dimensional maps of photospheric scattering polarization at sub-arcsecond scales, enabled by the capabilities of a 4-meter
solar telescope.
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All authors Franziska Zeuner, Luca Belluzzi, Ernest Alsina Ballester, Roberto Casini, David M. Harrington, Tanausú del Pino Alemán, Javier Trujillo Bueno
Cosmology and Nongalactic Astrophysics
Niebla: an open-source code for modeling the extragalactic background light
Sara Porras-Bedmar and Manuel Meyer
The flux of extragalactic gamma rays is attenuated through interactions with optical and infrared
photons of the extragalactic background light (EBL). The EBL is an isotropic, diffuse
photon field that is difficult to measure directly at these wavelengths due to strong foreground emission. We present niebla, the first open-source code to compute the EBL from optical to far-infrared wavelengths using a phenomenological approach that accepts fully customizable inputs. This software enables a detailed modeling of the influence of EBL optical depth on gamma-ray observations and facilitates the distinction between different
dust reemission models. The code models the optical background primarily from
stellar emission, by evolving the spectrum of a single
stellar population as a function of
redshift, considering mean
metallicity evolution and
star formation rate density. Additional sources to the EBL can be provided by the user. The code already includes optional contributions from, e.g., stripped
stars, intra-
halo light, or the decay of
axion dark matter. The optical emissivity is then absorbed by interstellar
dust and reemitted in the infrared regime. We provide multiple prescriptions to model this process, using spectral
dust templates or a combination of blackbodies. We provide three EBL models calculated with different
dust reemission prescriptions, which have been fitted to various observational data sets. In addition, we showcase the versatility of our model through a simulated observation of the blazar Markarian 501 in a high-flux state with the LHAASO array. We find that the simulated VHE spectrum is highly sensitive to the
photon density of the EBL at infrared wavelengths. Our model will therefore allow the community to distinguish between different
dust reemission models and constrain EBL parameters with future observations.
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Cosmology and Nongalactic Astrophysics
Blue supergiants and the zero point of the Tully-Fisher relation: a path to a new independent test of the Hubble constant
Rolf-Peter Kudritzki, Fabio Bresolin, Miguel A. Urbaneka et al. (+1 more)
Blue supergiant distances of nearby
galaxies obtained with the flux-weighted
gravity-luminosity relationship are used for a measurement of the zero points of Tully-Fisher relationships at different photometric passbands. The Cousins I-band and the infrared WISE bands W1 and W2 are investigated. The results are compared with previous work using Cepheid and Tip-of-the-Red-
Giant-Branch distances. No significant differences were encountered. This supports the large values of the Hubble constant greater than 73km/s/Mpc found with the Tully-Fisher distance ladder work over the last decade. Applying blue supergiant distances on the I-band Tully-Fisher relation observations yields a Hubble constant H0 = 76.2+/-6.2 km/s/Mpc. The large uncertainty is caused by the still relatively small blue supergiant
galaxies sample size but will be reduced in future work.
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All authors Rolf-Peter Kudritzki, Fabio Bresolin, Miguel A. Urbaneka, Eva Sextl
High Energy Astrophysical Phenomena
Magnetic Field-Line Curvature and Its Role in Particle Acceleration by Magnetically Dominated Turbulence
Samuel Sebastian and Luca Comisso
We employ first-principles, fully kinetic particle-in-
cell simulations to investigate
magnetic field-line
curvature in magnetically dominated turbulent
plasmas and its role in particle acceleration through
curvature-drift motion along the motional electric field. By varying the fluctuation-to-mean
magnetic-field ratio $\delta B_0/B_0$, we examine
curvature $\kappa$ statistics and their connection to particle acceleration. The
curvature probability densities display broad power-law wings, scaling linearly in $\kappa$ below the peak and developing hard high-$\kappa$ tails for $\delta B_0/B_0 \gtrsim 1$. As the mean field strengthens, the high-$\kappa$ tails steepen, and large-
curvature events are suppressed when $\delta B_0/B_0 \ll 1$. The probability density functions of
magnetic field-line contraction, ${\bf v}_E \cdot {\bf \kappa}$, with ${\bf v}_E$ the field-line velocity, develop power-law tails well described by a symmetric Pareto distribution, characteristic of
stochastic energy exchanges, with the tails becoming harder as $\delta B_0/B_0$ increases. Our guiding-center analysis shows that
curvature-drift acceleration accounts for a substantial fraction of the energization via the motional electric field, and that it strengthens with increasing $\delta B_0/B_0$. For well-magnetized particles,
curvature-drift acceleration typically exceeds ${\bf\nabla}B$ drift, polarization drift, and betatron contributions. These results identify
curvature-drift acceleration as a principal pathway through which magnetized
turbulence transfers energy to nonthermal particles in astrophysical
plasmas.
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Solar and Stellar Astrophysics
Assessing the star formation history of all-sky and part-sky 100pc white dwarf samples
Emily K. Roberts, Pier-Emmanuel Tremblay and Antoine Bédard
Thanks to
Gaia and large-scale spectroscopic follow-up surveys (4MOST, DESI, WEAVE, SDSS-V), it is now possible to build representative and minimally biased samples of the local white
dwarf population. Here we analyse several volume-limited 100pc samples of white
dwarfs, constructed from different surveys and studies, to evaluate their completeness and residual biases. We model the underlying
star formation history and
Galactic disc age via comparison with simulated populations of white
dwarfs to quantitatively characterise completeness. We assess whether the benefit of
Gaia XP spectra in
datasets outweighs the reduction in sample size, and to what extent targeted, part-sky, and magnitude limited surveys can be used in comparison to all-sky volume limited surveys. Additionally, we simulate the 4MOST 100PC sub-survey and discuss its use to better understand the local
star formation history.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
QCD corrections to the electroweak sphaleron rate
Dietrich Bödeker and Philipp Klose
The electroweak sphaleron rate in the high temperature phase of the Standard Model is inversely proportional to the weak-isospin conductivity. So far, only electroweak interactions were included in its computation. Here we take into account
quark scattering through strong interactions at leading-log order. These reduce the
quark contribution to the conductivity by up to 15 %, and the total conductivity by up to 6 %.
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Solar and Stellar Astrophysics
Scaler data from the Pierre Auger Observatory as a proxy of solar activity
C. Taricco, I. Bizzarri, C. Dionese et al. (+1 more)
Solar activity variations strongly impact the modulation of the flux of low-energy
Galactic Cosmic Rays (GCRs) reaching the Earth. The secondary particles, which originate from the interaction of GCRs with the atmosphere, can be revealed by an array of ground detectors. We show that the low-threshold rate (scaler) time series recorded over 16 years of operation by the surface detectors of the Pierre Auger Observatory in Malargüe (Argentina) strongly reflects
solar activity and can be considered as a new proxy of
solar variability. To achieve this result, we apply advanced spectral methods to this time series and to the classical
solar sunspot number and sunspot area series. We detect and compare highly significant variations with periods ranging from the decadal to the daily scale and identify the origin of each variability mode. In conclusion, we show that the Auger scaler data, thanks to the very low noise level and high statistical significance related to the very high count rates ($\sim 10^6$ counts per second), allow for a thorough and detailed investigation of the GCR flux variations in the heliosphere.
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All authors C. Taricco, I. Bizzarri, C. Dionese, S. Mancuso
Astrophysics of Galaxies
After 54 years of bar instability studies: a fresh surprise
J. A. Sellwood, Victor P. Debattista and R. G. Carlberg
The well-known bar instability of rotationally-supported disk
galaxy models has been studied extensively since its first discovery over half a century ago. We were therefore very surprised to find cases of disks embedded in rigid
halos, which on the basis of widely-cited criteria should be unstable, that appeared to be robustly stable. Here we show that the unstable bar mode in such simulations was being suppressed by changes to the disk caused by other instabilities having higher angular
symmetry that were the first to saturate. Although this may seem like a promising solution to the long-standing puzzle presented by the apparent stability of real disk
galaxies, we also show that instability is restored in the same models when the rigid
halo is replaced by a live population of particles, where the usual stability conditions apply. Our study has been confined to a narrow range of models, and we cannot therefore exclude the possibility that mode interference may be able to prevent bar formation in other models having live
halos.
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Astrophysics of Galaxies
Strong Lensing Model and Dust Extinction Maps of the Host Galaxy of Type Ia Supernova H0pe
A. Galan, S. Schuldt, G. B. Caminha et al. (+11 more)
Strong gravitational
lensing by massive
galaxy clusters offers rare opportunities to observe multiple images of distant ($z \gtrsim 2$) Type Ia
supernovae (SNe) and to resolve the properties of their host
galaxies. A recent outstanding example is the Type Ia SN H0pe ($z = 1.78$), which the James Webb Space
Telescope (JWST) discovered in NIRCam images, when the
galaxy cluster PLCK G165.7+67.0 (G165, $z = 0.35$) still produced three images of it. In this work, we build a new strong
lensing model of G165, first using only the positions of multiple images of background
galaxies. We then significantly increase the number of constraints around the position of SN H0pe by modeling the extended surface brightness of the SN host
galaxy. Including extended image information reduces the average uncertainty on mass model parameters by more than an order of magnitude. We also study the spatial distribution of
dust in the arc to estimate the
dust extinction at the position of SN H0pe. We find good statistical agreement of the extinction estimate, at $\lesssim 1\sigma$, with three fully independent methods based on spectral energy distribution fitting. Moreover, our extended-image lens model of G165 allows us to map the
dust distribution of the host
galaxy from the image plane to the source plane.
Supernova H0pe exploded in a region with a relatively high extinction ($A_V \approx 0.9$ mag) at around $\sim 1$ kpc from its host center. This work shows that extended image modeling in
lensing clusters simultaneously reduces the uncertainty on lens model parameters and enables spatially resolved analyses of lensed transients' host
galaxies. Such modeling advances are expected to play an important role in future cosmological analyses using strongly lensed SNe.
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All authors A. Galan, S. Schuldt, G. B. Caminha, S. H. Suyu, R. Cañameras, S. Ertl, C. Grillo, A. Acebron, B. Frye, A. M. Koekemoer, M. Pascale, R. Windhorst, J. M. Diego, N. Foo
Earth and Planetary Astrophysics
High-Resolution Echelle Spectroscopy for Solar System Planets: A Planet-as-Point-Source Analogy
Parvathy Menon, Sivarani T, Sriram S et al. (+4 more)
Transmission spectroscopy has proven to be an effective technique for characterizing
exoplanet atmospheres. However, transmission spectroscopy requires planetary transits, which occur for only a small fraction of planetary systems due to
geometric alignment constraints; hence, characterizing
exoplanets through their reflected spectrum of host
stars will be helpful for a large number of
exoplanets. The upcoming extremely large
telescopes (ELTs) will be able to study the reflected spectra of
exoplanets. Here, we present a preliminary optical design and a detailed throughput analysis of the instrumentation that interfaces the 2.34 m Vainu Bappu
Telescope prime focus to an existing high-resolution echelle spectrograph with disk-integrated light from
solar system objects. One of the primary objectives is to obtain high-resolution, high signal-to-noise reflected spectra from the
solar system objects.
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All authors Parvathy Menon, Sivarani T, Sriram S, Manjunath Bestha, Devika K Divakar, Rajaguru S P, Arun Surya
Solar and Stellar Astrophysics
Barium abundances of A–F–G type stars in the Hyades cluster
Yoichi Takeda
With an aim of clarifying the extent and parameter-dependence of compositional anomaly of barium in A-type
stars, Ba abundances were spectroscopically determined based on BaII 6141/6496 lines for 89 (23 A-type and 66 F–G-type) main-sequence
stars belonging to the members of Hyades cluster by taking into account the non-LTE effect and the hyper-fine-structure effect. While the non-LTE effect tends to strengthen lines in G
stars, it acts in the direction of line weakening in the regime of A
stars due to increasing imortance of overionization. The Ba abundances of G
stars turned out almost constant (<A>= 2.33), indicating that the
primordial composition of Ba in Hyades is mildly supersolar by ~+0.2dex. In contrast, A-type
stars show Ba overabundances of considerably large dispersion (0~<[Ba/H]~<2). Since this Ba excess tends to increase with an increase/decrease in Teff/vsini, these two parameters may be essential for producing or controling the anomaly. Regarding Hyades F-type
stars, their Ba abundances are not uniform but show a broad depression (by <~0.3dex) around Teff~6500K, interestingly coinciding with the location of Li-dip.
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High Energy Astrophysical Phenomena
Non-conservative Mass Transfer in the Neutron Star Stripping Model
Nikita Kramarev and Andrey Yudin
The process of long-term stable mass transfer (or stripping) in a close
neutron star binary system is possible at a sufficiently large initial asymmetry of the component masses. At the final stage of the
evolution of such systems, the low-mass
neutron star fills its Roche lobe, whereupon its mass is gradually transferred to the more massive component. At a certain point, the stability of the mass transfer is lost, causing the minimum-mass
neutron star to explode. In the present stripping calculations, the effect of non-conservative mass transfer has been taken into account for the first time, resulting in an increase in the duration of stable mass transfer from a few tenths of a second to a few seconds. This allows the time delay of 1.7 s between the loss of the gravitational-wave signal and the detection of the gamma-ray burst from the multimessenger event GW170817-GRB170817A to be naturally explained. The interaction of the envelope of the exploded minimum-mass
neutron star with the matter ejected during non-conservative mass transfer may explain two episodes in the light curve of this gamma-ray burst.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.flu-dyn
Are heuristic switches necessary to control dissipation in modern smoothed particle hydrodynamics ?
Domingo García-Senz and Rubén M. Cabezón
Artificial viscosity is commonly employed in smoothed particle hydrodynamics (SPH) to model dissipation in hydrodynamic simulations. However, its practical implementation today relies, in many cases, on complex numerical switches to restrict its application to regions where dissipation is physically warranted, such as shocks. These switches, while essential, are imperfect and can introduce additional numerical noise. In this work we develop and validate a more efficient shock capture scheme for SPH that does not rely on artificial viscosity switches. Recent studies have proposed that subtracting the linear component of the velocity field can suppress spurious dissipation in shear-dominated regions. Building on this idea, we implement a velocity-reconstruction technique that removes the bulk linear motion from the local velocity field and uses the Balsara correction to modulate the dissipation. The presented methodology yields a balanced dissipation scheme that performs well across a range of regimes, including subsonic instabilities, shear flows, and strong shocks. We demonstrate that this approach yields improved accuracy and lower spurious dissipation, compared to the reference viscosity switch used in this work.
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High Energy Astrophysical Phenomena
Detection of ultra-high-energy cosmic rays in the southern hemisphere with FAST: data acquisition and preliminary results
Jakub Kmec, Petr Boril, Fraser Bradfield et al. (+29 more)
Ultra-high-energy
cosmic rays (UHECRs) remain one of the greatest mysteries in astroparticle physics. The Fluorescence detector Array of Single-pixel
Telescopes (FAST) is a next-generation
cosmic ray experiment which utilizes ground-based fluorescence
telescopes designed to detect these extremely rare particles at energies exceeding 30 EeV. FAST offers a cost-effective and low-maintenance solution to cover the huge detection areas required for UHECR observation. FAST
telescopes are currently installed and remotely operated in both hemispheres, at the Pierre Auger Observatory and the
Telescope Array experiment. To enable fully autonomous operation, a sophisticated trigger for data acquisition is essential. In this paper, we present two novel triggering
algorithms inspired by those used at the largest observatories, but improved to meet the specific requirements imposed by the FAST design. Their performance is validated using Monte Carlo simulations of extensive air showers and UHECR events detected by the FAST
telescope in the southern hemisphere. Finally, we present the sensitivity analysis estimate for FAST.
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All authors Jakub Kmec, Petr Boril, Fraser Bradfield, Karel Cerny, Ladislav Chytka, Toshihiro Fujii, Pavel Horvath, Miroslav Hrabovsky, Vlastimil Jilek, Jiri Kvita, Max Malacari, Massimo Mastrodicasa, John N. Matthews, Stanislav Michal, Marcus Niechciol, Libor Nozka, Miroslav Palatka, Miroslav Pech, Paolo Privitera, Francesco Salamida, Shunsuke Sakurai, Petr Schovanek, Radomir Smida, Zuzana Svozilikova, Haruka Tachibana, Akimichi Taketa, Stan B. Thomas, Petr Travnicek, Martin Vacula, Jiri Zahora, Dusan Mandat, Petr Hamal
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Fitting NANOGrav 15-year data and ACT data with modified inflation in entropic cosmology
Simone D'Onofrio, Sergei Odintsov and Tanmoy Paul
Recent evidences of
stochastic gravitational wave background (SGWB) through
Pulsar Time Array (PTA) observations hint towards an alternative inflationary scenario, compared to the usual inflation, for describing the early stage of the universe in order to be compatible with the PTA data. Moreover, currently the Atacama Cosmology
Telescope (combined with the Planck 2018 and BAO) refines the constraint on inflationary observables, compared to the only-Planck 2018 measurements. In the present work, we simultaneously address these two issues by incorporating certain modification during inflation over the usual inflationary scenario. Such modification amplifies the
primordial tensor perturbation over the modes that are sensitive to the NANOGrav frequency region. For this purpose, we take the thermodynamic route of cosmology where the
entropy of the apparent horizon is given by a generalized form of
entropy that is able to generalize the other known form of horizon
entropies for suitable representations. The constraints on the model parameters coming from the ACT data also fit the NANOGrav 15-year data (based on numerical analysis), which reveal the model's compatibility with both the ACT and the PTA data.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
GUT-Scale Smooth Hybrid Inflation with a Stabilized Modulus in Light of ACT and SPT Data
Waqas Ahmed, Constantinos Pallis and Mansoor Ur Rehman
We analyze a generalized framework of smooth F-term hybrid inflation (smFHI) consistent with gauge coupling unification within the Minimal Supersymmetric Standard Model (MSSM). The
embedding of the model in two specific Supergravity settings addresses at the same time the $\eta$ problem and the compatibility with the recent ACT or SPT data. The one relies on the choice of a shift-symmetric Kähler potential for the inflaton which revitalizes the SUSY predictions of smFHI, whereas the other employs a Kähler potential associated with an
hyperbolic Kähler
manifold. An essential role in both our constructions is played by a decoupled superheavy field without superpotential and Kaehler potential inspired by string- and D-brane–based models. Our proposal can be realized for a variety of representations for the
Higgs fields involved in smFHI and assures monotonic inflationary potential.
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Astrophysics of Galaxies
The effect of triaxiality on the dynamics of triple supermassive black holes in a cosmological context
Navonil Saha, Peter Berczik, Andreas Just et al. (+1 more)
The hierarchical nature of
galaxy formation in the $\Lambda$CDM framework often leads to multiple supermassive black holes (SMBHs) in the
galactic nuclei. The timescale over which
galaxies merge, plays a crucial role in shaping the dynamical
evolution and the merger dynamics of their central SMBHs. While binary SMBH
evolution is well studied, the long-term dynamics of triple SMBH systems, particularly in non-spherical potentials, remain less understood. We investigate the role of triaxiality in the
evolution and dynamics of triple SMBHs with initial conditions drawn from the ROMULUS25 cosmological simulation, using high-resolution gravitodynamical N-body simulations. We explore different orbital configurations and host shapes, tracking the
evolution from
galactic inspiral to hard binary formation at sub-parsec scales. In all cases, the two most massive SMBHs form a rapidly hardening binary that coalesces within a fraction of a Hubble time, while the third forms a stable hierarchical triple system with the heavier binary, or remains on a wide orbit.
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All authors Navonil Saha, Peter Berczik, Andreas Just, Margarita Sobolenko
Solar and Stellar Astrophysics
Mass-radius relationship and gravitational wave emission from magnetized spheroidal quark stars
Rajasmita Sahoo, Arunkarthiheyan Thiyagarajan, Asutosh Panda et al. (+1 more)
In this work, we investigate the structure and gravitational wave (GW) signatures of strongly magnetized, oblate spheroidal
quark stars by employing an anisotropic equation of state (EoS) derived from the MIT Bag model, extended to include the effects of density-dependent strong
magnetic fields and the resulting pressure anisotropy arising from the breaking of spatial
symmetry. Both magnetized strange
quark matter (MSQM) and magnetized color-
flavor locked (MCFL) phases are examined within the framework of the $\gamma$-metric formalism, which captures the deviation from spherical
symmetry. We compute the mass-radius relation, ellipticity, gravitational
redshift, mass quadrupole moment and
tidal deformability for representative bag constants of $\rm{65\,MeV/fm^3}$ and $\rm{75\,MeV/fm^3}$. Using the obtained quadrupole moments, we further estimate the continuous gravitational wave strain amplitude ($h_{0}$) for isolated deformed rotating
quark stars. Our results indicate that density-dependent strong
magnetic fields and color superconductivity can significantly alter
stellar compactness and yield gravitational wave signals, potentially detectable by next generation observatories like the Einstein
Telescope and
Cosmic Explorer.
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All authors Rajasmita Sahoo, Arunkarthiheyan Thiyagarajan, Asutosh Panda, Somnath Mukhopadhyay
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Symbolic Regression and Differentiable Fits in Beyond the Standard Model Physics
Shehu AbdusSalam, Steven Abel, Deaglan Bartlett et al. (+1 more)
We demonstrate the efficacy of symbolic regression (SR) to probe models of particle physics Beyond the Standard Model (BSM), by considering the so-called Constrained Minimal Supersymmetric Standard Model (CMSSM). Like many incarnations of BSM physics this model has a number (four) of arbitrary parameters, which determine the experimental signals, and cosmological observables such as the dark matter relic density. We show that analysis of the phenomenology can be greatly accelerated by using symbolic expressions derived for the observables in terms of the input parameters. Here we focus on the
Higgs mass, the cold dark matter relic density, and the contribution to the anomalous
magnetic moment of the
muon. We find that SR can produce remarkably accurate expressions. Using them we make global fits to derive the posterior probability densities of the CMSSM input parameters which are in good agreement with those performed using conventional methods. Moreover, we demonstrate a major advantage of SR which is the ability to make fits using differentiable methods rather than sampling methods. We also compare the method with neural network (NN) regression. SR produces more globally robust results, while NNs require data that is focussed on the promising regions in order to be equally performant.
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All authors Shehu AbdusSalam, Steven Abel, Deaglan Bartlett, Miguel Crispim Romão
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Probing cosmic strings via gravitational-wave lensing
Oleg Bulashenko, Nino Villanueva, Roberto Bada Nerin et al. (+1 more)
We present a framework for detecting gravitational-wave signals lensed by
cosmic strings (CSs), addressing a key gap in current searches. CSs, whose detection would provide a unique probe of high-energy physics and the early Universe, possess distinct topological and
geometric features that require a dedicated search strategy. Our approach employs a full-wave transmission factor, expressed analytically via Fresnel integrals, which captures the characteristic diffraction and interference effects of the conical spacetime around a straight CS. We contrast CS
lensing with the well-studied point mass lens (PML) model, highlighting their fundamental differences: CS
lensing depends on cosmological distances, string tension $\Delta$, and wavelength $\lambda$, and produces two non-amplified images set by the global conical geometry. In contrast, PML
lensing is governed by the distance-independent ratio $\sim M_{Lz}/\lambda$, where $M_{Lz}$ represents the redshifted mass of the lens, with image properties derived from the lens equation. For BBH mergers lensed by CSs, we show that the waveforms exhibit a characteristic beating pattern or time-separated exact replicas. We derive a detectability bound on the string tension and, using
Bayesian model selection, demonstrate that CS
lensing is distinguishable from both unlensed and PML-lensed signals across a wide region of parameter space.
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All authors Oleg Bulashenko, Nino Villanueva, Roberto Bada Nerin, José A. Font
Earth and Planetary Astrophysics
Addressing wavelength-correlated systematics in exoplanet transmission spectroscopy: a 2D Gaussian Process approach
Lokesh Manickavasaham, Manjunath Bestha, Sivarani Thirupathi et al. (+2 more)
Ground-based transmission spectroscopy is often dominated by systematics, which obstructs our ability to leverage the advantages of larger aperture sizes compared to space-based observations. These systematics could be time-correlated, uniform across all spectroscopic light curves, or wavelength-correlated, which could significantly affect the characterization of
exoplanet atmospheres. Gaussian Processes were introduced in transmission spectroscopy by Gibson et al. (2012) to model correlated systematics in a non-parametric way. The technique uses auxiliary information about the observation and independently fits each spectroscopic light curve to provide robust atmospheric
retrievals. However, this method assumes that the uncertainties in the transmission spectrum are uncorrelated in wavelength, which can cause discrepancies and degrade the precision of atmospheric
retrievals. To address this limitation, we explore a 2D GP framework formulated by Fortune et al. (2024) to simultaneously model time- and wavelength-correlated systematics. We present its application to ground-based observations of TOI-4153b obtained using the 2-m Himalayan Chandra
Telescope (HCT). As we move towards detecting smaller and cooler
planets, developing new methods to address complex systematics becomes increasingly essential.
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All authors Lokesh Manickavasaham, Manjunath Bestha, Sivarani Thirupathi, Arun Surya, Athira Unni
Solar and Stellar Astrophysics
The impact of stellar winds and tidal locking effects on the habitability of Earth-like exoplanets around M dwarf stars
J. P. Hidalgo, D. R. G Schleicher and D. P. González
We present an assessment of the effects of
stellar wind
magnetic and mechanical components on the habitability of Earth-like
exoplanets orbiting the inner and outer radii of the habitable zone (HZ) of M
dwarfs. We consider
stars with masses in the range of $0.09 - 0.75 M_\odot$ and
planets with a surface dipolar
magnetic field of 0.5 G. We estimate the size of the magnetospheres of such
exoplanets using the pressure balance equation including the contribution of
magnetic and ram pressures from
stellar winds. We explore different scenarios, including fast and slow
stellar winds, to assess the relevance of kinetic contribution. Furthermore, the effect of
tidal locking and potential deviations from the Parker spiral, typically used to describe the interplanetary
magnetic field, are analyzed. We show that for low mass
stars ($M < 0.15 M_\odot$), the ram pressure exerted by
stellar winds affects the size of the magnetosphere more than the
stellar wind
magnetic pressure. Interestingly, when the ram pressure is not much stronger than the
magnetic pressure, typically for higher mass
stars, the inclusion of ram pressure can be beneficial to the magnetosphere due to the magnetopause currents. A magnetosphere with the size of that of modern Earth is difficult to achieve with the current assumptions. However, an early Earth magnetosphere is achieved by roughly half of our hypothetical
planets orbiting the outer radius of the HZ in most of the considered cases. We find that deviations from the Parker spiral can affect the results significantly, reducing the magnetosphere by $56\%$ in extreme cases. Most of the hypothetical
planets are most likely (or might be) tidally locked, with the notable exception of those orbiting the outer HZ of GJ 846 and V1005 Ori.
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Earth and Planetary Astrophysics
A Stochastic Parameterization of Non-Orographic Gravity Waves Induced Mixing for Mars Planetary Climate Model
Jiandong Liu, Ehouarn Millour, François Forget et al. (+2 more)
This paper presents a formalism of mixing induced by non-orographic
gravity waves (GWs) to integrate with the
stochastic GWs scheme in the Mars Planetary
Climate Model. We derive the formalism of GWs and their mixing under the same assumptions, integrating the two schemes within a unified framework. Specifically, a surface-to-exosphere parameterization of GW-induced
turbulence has been derived in terms of the eddy
diffusion coefficient. Simulations show that the coefficient is on the order of 1E4 to 1E9 cm2 s-1 and a turbopause is at altitudes of 70 to 140 km, varying with seasons. The triggered mixing has minor effects on model temperatures, yet it substantially impacts upper atmospheric abundances. Simulations are consistent with observations from the Mars
Climate Sounder and the Neutral Gas and Ion Mass Spectrometer. Mixing enhances the tracer transports in the middle and upper atmosphere, governing the dynamics of these regions. The scheme reveals how non-orographic GW-induced
turbulence can regulate upper atmospheric processes, such as tracer escape.
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All authors Jiandong Liu, Ehouarn Millour, François Forget, François Lott, Jean-Yves Chaufray
Astrophysics of Galaxies
FAST-SBF: an automatic procedure for the measurement of Surface Brightness Fluctuations for large sky surveys
Gabriele Riccio, Michele Cantiello, Rebecca Habas et al. (+9 more)
The Surface Brightness Fluctuation method is one of the most reliable and efficient ways of measuring distances to
galaxies within 100 Mpc. While recent implementations have increasingly relied on space-based observations, SBF remains effective when applied to ground-based data. In particular, deep, wide-field imaging surveys with sub-arcsecond seeing conditions allows us for accurate SBF measurements across large samples of
galaxies. With the upcoming next generation wide-area imaging surveys, the thousands of
galaxies suitable for SBF measurements will give us the opportunity to constrain the 3D structure of the local universe. We present FAST-SBF, a new Python-based pipeline for measuring SBF, developed to support the analysis of large
datasets from upcoming wide-field imaging surveys such as LSST, Euclid, and Roman. The procedure, still in the testing and development stage, is designed for automation and minimal user intervention, offering a fast and flexible approach to SBF distance estimation. We validate the performance of the procedure on high-quality imaging data from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP), a precursor to LSST, analyzing a sample of both luminous early-type
galaxies and fainter
dwarfs. Our measurements are also compared with recent results from the Next Generation Virgo Cluster Survey (NGVS) and with the SPoT
stellar population synthesis models. The results show excellent agreement with published distances, with the capability of measuring the SBF signal also for faint
dwarf galaxies. The pipeline allows the user to completely analyze a
galaxy in relatively short time ($\approx$ minutes) and significantly reduces the need for user intervention. reduces at minimum the user intervention. The FAST-SBF tool is planned for public release to support the community in using SBF as a distance indicator in next-generation surveys.
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All authors Gabriele Riccio, Michele Cantiello, Rebecca Habas, Nandini Hazra, Giuseppe D'Ago, Gabriella Raimondo, John P. Blakeslee, Joseph B. Jensen, Marco Mirabile, Enzo Brocato, Massimo Brescia, Claudia M. Raiteri
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Data-driven exploration of the neutron $^3\text{P}_2$ pairing gap using Cassiopeia A neutron star observational data: Direct $\chi^2$ minimization
Yoonhak Nam and Kazuyuki Sekizawa
The rapid cooling observed in the Cassiopeia~A
neutron star (Cas~A NS) is one of the most stringent tests for
neutron-
star cooling theory. While Cooper-pair breaking and formation (PBF)
neutrino emission is a leading candidate, uncertainties remain regarding the PBF efficiency factor $q$ and the
neutron ${}^{3}\mathrm{P}_{2}$ pairing gap. This work explores in a data-driven manner how the optimized gap shape responds to variations of the PBF emissivity parameter $q$ within a fixed cooling setup. We introduce a novel gap parametrization, in which each parameter carries direct physical meaning and controls the gap amplitude, peak location, width, and asymmetry. Using a Fortran-based cooling code and the BSk24 equation of state, we perform parameter-space exploration guided by the Cas~A NS data. Global optimization is carried out with Optuna's tree-structured Parzen
estimator, followed by local refinement using the Nelder–Mead method. The optimized solutions yield physically reasonable gaps with peak amplitudes $\Delta_{\max}\approx0.5$–$0.6~\mathrm{MeV}$. Although the multi-objective formulation explores the parameter space more broadly, the single-objective $\chi^{2}$-only optimization achieves the lowest $\chi^{2}$. For $M_{\mathrm{NS}}=1.4\,M_{\odot}$, increasing $q$ drives the optimized gap and critical-temperature profiles toward smoother and more localized shapes, improving consistency with the observed trend. Models with $q\gtrsim0.4$ reproduce the decline rate within the $1\sigma$ confidence interval, whereas the baseline case $q\simeq0.19$ lies near the $3\sigma$ level. Our results suggest larger effective PBF emissivities than the baseline estimate, although robust constraints on $q$ require future
Bayesian inference including uncertainties in mass, envelope composition, equation of state, pairing microphysics, and age offset. (Shortened due to the arXiv abstract length limit.)
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.app-ph
Comparative Analysis of Thermal Models for Test Masses in Next-Generation Gravitational Wave Interferometers
Vincenzo Pierro, Vincenzo Fiumara, Guerino Avallone et al. (+8 more)
Accurate thermal modeling of Terminal Test Masses (TTMs) is crucial for optimizing the sensitivity of gravitational wave interferometers like Virgo. In fact, in such gravitational wave detectors even minimal
laser power absorption can induce performance-limiting thermal effects. This paper presents a detailed investigation into the steady-state thermal behavior of TTMs. In particular, future scenarios of increased intracavity
laser beam power and optical coating absorption are considered. We develop and compare two numerical models: a comprehensive model incorporating volumetric heat absorption in both the multilayer coating and the bulk substrate, and a simplified reduced model where the coating's thermal impact is represented as an effective surface boundary condition on the substrate. Our simulations were focused on a ternary coating design, which is a candidate for use in next-generation detectors. Results reveal that higher coating absorption localizes peak temperatures near the coating–
vacuum interface. Importantly, the comparative analysis demonstrates that temperature predictions from the reduced model differ from the detailed model by only milli-Kelvins, a discrepancy often within the experimental uncertainties of the system's thermo-physical parameters. This finding suggests that computationally efficient reduced models can provide sufficiently accurate results for thermal management and first-order distortion analyses. Moreover, the critical role of accurately characterizing the total power absorbed by the coating is emphasized.
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All authors Vincenzo Pierro, Vincenzo Fiumara, Guerino Avallone, Giovanni Carapella, Francesco Chiadini, Roberta De Simone, Rosalba Fittipaldi, Gerardo Iannone, Alessandro Magalotti, Enrico Silva, Veronica Granata
Instrumentation and Methods for Astrophysics
Capability of using the normalizing flows for extraction rare gamma events in the TAIGA experiment
A.P. Kryukov, A.Yu. Razumov, A.P. Demichev et al. (+6 more)
The objective of this work is to develop a method for detecting rare gamma quanta against the background of charged particles in the fluxes from sources in the Universe with the help of the deep learning and normalizing flows based method designed for anomaly detection. It is shown that the suggested method has a potential for the gamma detection. The method was tested on model data from the TAIGA-IACT experiment. The obtained quantitative performance indicators are still inferior to other approaches, and therefore possible ways to improve the implementation of the method are proposed.
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All authors A.P. Kryukov, A.Yu. Razumov, A.P. Demichev, J.J. Dubenskaya, E.O. Gres, S.P. Polyakov, E.B. Postnikov, P.A. Volchugov, D.P. Zhurov
Earth and Planetary Astrophysics
3D analytical theory of the perturbed single-synchronous state. Application to the post-impact Didymos-Dimorphos system
Michalis Gaitanas, Christos Efthymiopoulos, Ioannis Gkolias et al. (+2 more)
We develop the 3D generalization of the planar analytical theory presented in Gaitanas et. al., 2024, which deals with states slightly perturbed from the exact `single-synchronous
equilibrium state' (SSES) of the full two-body problem. The SSES corresponds to two non-spherical gravitationally interacting bodies, settled in nearly circular relative orbit, with rotation axes normal to the orbital plane, rapid rotation of the primary and synchronous rotation of the secondary. In the present paper we remove all simplifying assumptions of our previous work Gaitanas et. al., 2024, and show how to compute analytical solutions describing a 3-dimensional perturbation of the system from the SSES in the framework of two distinct theories, called `linear' and `nonlinear'. Linear theory stems from averaging the equations of motion over the primary's rapid rotation angle. This maps the SSES to an
equilibrium point of the averaged system, around which analytical solutions can be computed by linearization of the equations of motion. In nonlinear theory, instead, we compute a high order normal form for the
Hamiltonian of motion through a sequence of canonical transformations in the form of series. Resonances between the basic system's frequencies appear in the nonlinear theory as small divisors. We show that, close to resonances, the nonlinear theory leads to a partially integrable model, sufficient to analytically describe the
evolution of the relative orbit, but only of some of the Euler angles of the system. As a basic application, we compute analytical solutions representing various possible Didymos-Dimorphos post-impact orbital and rotational states. In this case, all analytical formulas here proposed are of direct utility in fitting
algorithms exploiting available time series of post-impact observational data.}}
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All authors Michalis Gaitanas, Christos Efthymiopoulos, Ioannis Gkolias, George Voyatzis, Kleomenis Tsiganis