High Energy Astrophysical Phenomena
Revisiting the Radio Lateral Distribution Function: An amplitude dependence on $X_{\rm max}$ and primary composition
Washington R. Carvalho Jr. and Lech Wiktor Piotrowski
We show that there is a strong dependence of the
radio LDF electric field amplitudes at ground level on the position of $X_{\rm max}$ in the atmosphere, even accounting for differences in the EM energy of the showers. Since an $X_{\rm max}$ dependence leads to a primary composition dependence, this implies that information on the mass composition is encoded not only in the LDF shape but also in its amplitude. This $X_{\rm max}$ dependence can be explained in terms of two competing scalings of the measured electric field: One goes with $(1/\rho)^J$, where $\rho$ is the air density at $X_{\rm max}$ and $J$ is a zenith dependent non-linearity factor describing coherence loss. This density scaling tends to decrease the geomagnetic emission of deeper showers. The other scaling goes with $(1/R)$, where $R$ is the distance from $X_{\rm max}$ to the core at ground, and instead increases the measured electric field of deeper showers. At low zenith angles, the $(1/R)$ scaling is stronger and leads to larger measured electric fields as $X_{\rm max}$ increases. The picture at higher zeniths, i.e., lower densities, is more nuanced. In this region, the deflections due to the Lorentz force are much larger and introduce extra time delays between the particle tracks, decreasing the coherence of the emission. This loss of coherence is highly dependent on the strength of the geomagnetic field and can slow down, or even reverse the increase of the
radio emission with decreasing air density. This strong, yet historically overlooked LDF amplitude dependence on $X_{\rm max}$/composition could be used to directly infer, even bypassing any $X_{\rm max}$ reconstruction, the
cosmic ray primary composition on an event-by-event basis. It could also have some repercussions on other
radio reconstruction methods, such as a possible $X_{\rm max}$/composition bias on shower electromagnetic energy reconstruction methods.
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Earth and Planetary Astrophysics
Exploring Synergies between Twinkle and Ariel: a Pilot Study
Andrea Bocchieri, Luke Booth and Lorenzo V. Mugnai
Launching in 2027 and 2029, respectively, Twinkle and Ariel will conduct the first large-scale homogeneous spectroscopic surveys of the atmospheres of hundreds of diverse
exoplanets. This will fundamentally transition the field to an era of population-level characterisation. In this pilot study, we aim to explore possible synergies between Twinkle and Ariel to determine for instance whether prior Twinkle observations can substantially inform the target selection and observing strategy of Ariel. This study primarily aims to encourage further investigation by both consortium communities by showing what a potential scientific synergy would look like on a promising scientific case that requires further exploration. For this aim, we select a small subset of "cool"
planets that are also particularly well-suited to be observed by Twinkle and therefore Ariel. By using representative noise estimates for both missions, we compute the number of visits required for an observation. Then, we simulate and retrieve transmission spectra of each target, assuming gaseous, H2/He-dominated atmospheres and various atmospheric models. For all candidates, we find that atmospheric parameters are generally retrieved well within 1-sigma to input values, with Ariel typically achieving tighter constraints. We demonstrate that for a small subset of cool gaseous
planets, exploitable synergies exist between Twinkle and Ariel observations and Twinkle may very well provide a vantage point to plan Ariel observations. The true extent of the potential synergies, far beyond our considered sample, will be determined by the final target lists. Once Twinkle is operational and its performance is known, it could reliably inform Ariel's target prioritization and Ariel's capabilities which are already well-established can help define optimal targets and observational approaches for Twinkle.
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High Energy Astrophysical Phenomena
Accretion with two-phase gas supply and its application in black hole X-ray binaries
Yilong Wang, B. F. Liu and Mingjun Liu
Accretion in black hole X-ray binaries is commonly believed to be supplied by the Roche lobe overflow or the
stellar wind. The former is thought to form a geometrically thin disc while the diffuse wind could form a geometrically thick hot
accretion flow. In this paper, we instead consider a more generalised case, i.e.,
accretion with both cold and hot gas supplies, which feed a disc and a corona respectively. We investigate the interaction of disc and corona by analysing the energy coupling and matter exchange, i.e. corona condensation/disc evaporation, with a semi-analytical method. It is found that the
accretion geometry in the radial direction and the resultant emission spectrum depend strongly on both the total gas supply rate and the ratio of cold and hot gases. For gas supply rates of a few percent of the Eddington value, diverse geometries and spectral shapes are possible, depending on the fraction of cold gas supply. This provides an interpretation for the various spectra observed in intermediate states. However, at higher
accretion rates, regardless of the form of the feeding gas, the inner
accretion flow is always disc-dominated, implying an inevitable transition to the soft state, while at very low gas supply rates, hard state spectrum dominated by the hot flow is expected. We also present the predicted hardness-intensity correlation of Cygnus X-1, and constrain the value of the viscosity parameter of the
accretion flow to the range of 0.25–0.35 by comparing our results with MAXI observations.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Implications of $f(R)$ gravity on late-time cosmic structure growth through a complete description of density perturbations
Miguel Barroso Varela and Álvaro de la Cruz-Dombriz
We provide insight about the full form of the equations for matter density perturbations and the scalar Bardeen metric potentials in general $f(R)$ theories of
gravity. When considering viable modifications to the standard $\Lambda$CDM background, the full scale-dependent equations for the metric perturbations are provided and are shown to match the ones obtained with the quasistatic approximation. We investigate the impact of the $n=2$ Hu-Sawicki model on the late-time growth of structures. We find that updated late-time growth of structure data imposes $|f_{R_0}|\lesssim10^{-6}-10^{-5}$ and thus conclude that the Hu-Sawicki $f(R)$ model contributes no significant phenomenology at both background and perturbative level beyond the effective cosmological constant encompassed in its definition. This conclusion points to the survival of the present tension between early and late measurements of $\sigma_8$, as the Hu-Sawicki model can only worsen this issue or at best reproduce the results from the current concordance cosmological model. The generalized perturbative method showcased in this work can be applied to more elaborate $f(R)$ models to isolate genuine higher-order signatures beyond the quasistatic approximation.
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High Energy Astrophysical Phenomena
The Regulated GeAs Cycles with the New $^{63}$Ga(p,$\gamma$)$^{64}$Ge and $^{64}$Ge(p,$\gamma$)$^{65}$As Reaction Rates and Their Impact on the GS 1826$-$24 Clocked Bursts and SAX J1808.4$-$3658 Photospheric Radius Expansion Bursts
Yi Hua Lam, Ning Lu, Alexander Heger et al. (+3 more)
The $^{63}$Ga(p,$\gamma$)$^{64}$Ge and $^{64}$Ge(p,$\gamma$)$^{65}$As thermonuclear reactions connect the ZnGa and GeAs cycles by diverting the flow of the rapid
proton capture process from $^{63}$Ga to $^{65}$As. Changes in these two reaction rates regulate the ZnGa and GeAs cycles and may affect the modeled properties matching with the observed counterparts of a type I X-ray burster. We implement the latest $^{63}$Ga(p,$\gamma$)$^{64}$Ge and $^{64}$Ge(p,$\gamma$)$^{65}$As reaction rates to the state-of-the-art self-consistent one-dimensional multi-zone thermo-hydrodynamic code, KEPLER, to study the influence of these new reaction rates on the models of the GS 1826$-$24 clocked burster and SAX J1808.4$-$3658 photospheric radius expansion burster. Both new reaction rates obtained by Lu et al. [Phys. Rev. C 110, 065804 (2024)] are determined from complementing the experimental input with the
nuclear spectroscopic information deduced from the full pf-shell space configuration-interaction shell-model calculations. By constraining the models on reproducing the observed burst peak, light-curve profile, fluence, and recurrence time, we find that the impact of the newly measured
proton thresholds and respective
proton-capture reactions on the burst light-curve profile of the GS 1826$-$24 clocked burster is, in fact, not as significant as claimed by Zhou et al. [Nat. Phys. 19, 1091 (2023)]. With or without the inclusion of the newly determined reaction rate of the highly influential $^{22}$Mg($\alpha$,p)$^{25}$Al reaction, the impact of the new $^{63}$Ga(p,$\gamma$)$^{64}$Ge and $^{64}$Ge(p,$\gamma$)$^{65}$As reaction rates on SAX J1808.4$-$3658 photospheric radius expansion bursts is evident. Our finding indicates that the models reproducing the 2002 October epoch of SAX J1808.4$-$3658 photospheric radius expansion burster is more sensitive to the uncertainties of thermonuclear reaction rates.
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All authors Yi Hua Lam, Ning Lu, Alexander Heger, Zi Xin Liu, Zac Johnston, Hidetoshi Yamaguchi
Instrumentation and Methods for Astrophysics
Singular Value-based Atmospheric Tomography with Fourier Domain Regularization (SAFR)
Lukas Weissinger, Simon Hubmer, Bernadett Stadler et al. (+1 more)
Atmospheric
tomography, the problem of reconstructing atmospheric
turbulence profiles from wavefront sensor measurements, is an integral part of many adaptive optics systems. It is used to enhance the image quality of ground-based
telescopes, such as for the Multiconjugate Adaptive Optics Relay For ELT Observations (MORFEO) instrument on the Extremely Large
Telescope (ELT). To solve this problem, a singular-value decomposition (SVD) based approach has been proposed before. In this paper, we focus on the numerical implementation of the SVD-based Atmospheric
Tomography with
Fourier Domain Regularization
Algorithm (SAFR) and its performance for Multi-Conjugate Adaptive Optics (MCAO) systems. The key features of the SAFR
algorithm are the utilization of the FFT and the pre-computation of computationally demanding parts. Together, this yields a fast
algorithm with less
memory requirements than commonly used
Matrix Vector Multiplication (MVM) approaches. We evaluate the performance of SAFR regarding reconstruction quality and computational expense in numerical experiments using the simulation environment COMPASS, in which we use an MCAO setup resembling the physical parameters of the MORFEO instrument of the ELT.
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All authors Lukas Weissinger, Simon Hubmer, Bernadett Stadler, Ronny Ramlau
High Energy Astrophysical Phenomena
Probing Accretion Disk Winds of Stratified Nature with Fe XXVI Doublet in Black Hole X-ray Binaries
Keigo Fukumura, Shoji Ogawa, Atsushi Tanimoto et al. (+6 more)
Powerful ionized
accretion disk winds are often observed during episodic outbursts in
Galactic black hole transients. Among those X-ray absorbers, \fexxvi\ doublet structure (Ly$\alpha_1$+Ly$\alpha_2$ with $\sim 20$eV apart) has a unique potential to better probe the underlying physical nature of the wind; i.e. density and kinematics. We demonstrate, based on a physically-motivated
magnetic disk wind scenario of a stratified structure in density and velocity, that the doublet line profile can be effectively utilized as a diagnostics to measure wind density and associated velocity dispersion (due to thermal
turbulence and/or dynamical shear motion in winds). Our simulated doublet spectra with post-process radiative transfer calculations indicate that the profile can be (1) broad with a single peak for higher velocity dispersion ($\gsim 5,000$ km~s$^{-1}$), (2) a standard shape with 1:2 canonical flux ratio for moderate dispersion ($\sim 1,000-5,000$ km~s$^{-1}$) or (3) double-peaked with its flux ratio approaching 1:1 for lower velocity dispersion ($\lsim 1,000$ km~s$^{-1}$) in optically-thin regime, allowing various line shape. Such a diversity in doublet profile is indeed unambiguously seen in recent observations with XRISM/Resolve at microcalorimeter resolution. We show that some implications inferred from the model will help constrain the local wind physics where \fexxvi\ is predominantly produced in a large-scale, stratified wind.
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All authors Keigo Fukumura, Shoji Ogawa, Atsushi Tanimoto, Francesco Tombesi, Alfredo Luminari, Maxime Parra, Megumi Shidatsu, Liyi Gu, Ehud Behar
Astrophysics of Galaxies
XRISM mock observations of simulated AGN jets in the core of a galaxy cluster
Mahiro Shirotori and Yutaka Fujita
Jets from active
galactic nuclei (AGNs) are expected to heat the surrounding intracluster medium (ICM). We investigate how the interaction between jets and the ICM appears in high-resolution X-ray observations using mock X-ray observations based on two-dimensional hydrodynamic simulations. We constructed a model of an active
galactic nucleus (AGN) similar to Cygnus A (Cyg A), a powerful FR II
radio galaxy. Our simulations model bipolar jets propagating into a stratified ICM, forming forward shocks and low-density cocoons. Based on these results, we generate synthetic spectra that incorporate both shocked and unshocked ICM components. Then, we perform mock observations using the XRISM/Resolve X-ray spectrometer. We focus particularly on viewing angle effects. Our mock observations revealed that the smallest line broadening, observed as velocity dispersion, associated with the cocoon's bulk expansion occurs when observing along the jet direction, where the expansion velocity is highest. Although this may appear counterintuitive, it occurs because the rapidly expanding jet head contributes little to X-ray emission due to its high temperature and low density. Our results highlight the importance of considering the temperature and density structure of AGN-driven shocks and cocoons when interpreting XRISM data. These findings lay the groundwork for XRISM's observations of AGN jets and will improve our understanding of AGN feedback processes in
galaxy clusters.
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High Energy Astrophysical Phenomena
Can we ignore the time dependence in matter neutrino resonance?
Owais Ullah Faiz, Mushahid Hussain and Shashank Shalgar
In the vicinity of
neutron star mergers (NSMs), it is possible for the
neutrino self-interaction potential to cancel with the matter potential leading to matter
neutrino resonance (MNR). MNR is one of the most interesting mechanisms by which
neutrino flavor evolution can occur in dense astrophysical environments. Previous studies have typically assumed that the
neutrino flavor field evolves to a steady state – a simplification also used in other self-interaction models such as the
neutrino-bulb model. Here, we perform reproducible calculations of MNR using both time-independent and time-dependent formalisms and show that they yield qualitatively different
flavor survival probabilities. The time-independent approach produces unstable steady-state solutions that differ fundamentally from the dynamical behavior captured in time-dependent simulations. These results demonstrate that the steady-state assumption is generally invalid, and physical interpretations based on time-independent calculations of dense
neutrino systems require re-evaluation.
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Instrumentation and Methods for Astrophysics
Advances in detector response and background modelling in the ANAIS-112 experiment for annual modulation and other rare event searches
Tamara Pardo Yanguas
Numerous astronomical and cosmological observations point to the existence of dark matter, which constitutes about 27% of the Universe. Despite extensive efforts, only the DAMA/LIBRA experiment, using NaI(Tl) detectors at Gran Sasso National Laboratory, has reported a positive dark matter signal. To independently verify this result, using the same NaI target is essential. This is the goal of ANAIS-112, operating with 112.5 kg of NaI(Tl) scintillators since 2017 at the Canfranc Underground Laboratory (LSC). This thesis presents work within ANAIS-112, focusing on data analysis and the development of Geant4-based simulations to reduce systematics and increase sensitivity. Efforts have focused on understanding the ANAIS-112
crystals' response to
nuclear recoils. Systematic uncertainties related to the scintillation quenching factors (QFs) of sodium and iodine recoiling in NaI(Tl) must be addressed to ensure reliable comparisons with DAMA/LIBRA and other experiments. For that purpose, onsite
neutron calibrations in ANAIS-112 have been performed since 2021 at LSC using 252Cf sources. This work has compared calibration data with Geant4-based
neutron simulations, which has revealed Geant4 deficiencies in certain decay processes and cross sections in some versions. The simulations have proven highly sensitive to the QF used, favouring models in which the QF increases with energy and disfavouring DAMA values. In parallel, this thesis has contributed to improving the ANAIS-112 background model through a multiparametric fit of its background components. New physics searches have been conducted using ANAIS-112 data, including a reanalysis of the annual modulation signal and a search for
solar axions using six years of exposure. Finally, this thesis also includes work within the COSINUS experiment, focused on background modelling and the impact of internal backgrounds on the experiment's sensitivity.
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Astrophysics of Galaxies
WALLABY: an untargeted search for H I-bearing ultra-diffuse galaxies uncovers the first known ultra-diffuse galaxy pair
T. O'Beirne, V. A. Kilborn, M. E. Cluver et al. (+14 more)
Using the Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY) we performed an untargeted search for H I-bearing ultra-diffuse
galaxies (UDGs). We identified a core sample of 10 UDGs defined by $\mu_{g,0}\ge24$ mag arcsec$^{-2}$ and $R_{e}\ge1.5$ kpc, and a broader sample including 12 additional faint diffuse
galaxies ($\mu_{g,0}\ge23.7$ mag arcsec$^{-2}$ and $R_{e}\ge1.3$ kpc). Within the core sample, we highlight the first discovery of a UDG pair. Their projected separation is just 75 arcsec (22 kpc at 61.9 Mpc), with a central H I velocity difference of 34 km s$^{-1}$. The North-Western UDG (WALLABY J104513-262755-UDG-1) has a larger H I reservoir, $\log_{10}(M_{HI}/\rm M_{\odot}) = 8.95\pm0.03$, compared to the South-Eastern UDG (WALLABY J104513-262755-UDG-2), $\log_{10}(M_{HI}/\rm M_{\odot}) = 8.60\pm0.04$. UDG-1's
stellar mass and
star formation rate are also approximately an order of magnitude larger at $\log_{10}(M_*/\rm M_{\odot}) = 8.07\pm0.12$ and $\log_{10}(SFR/\rm M_{\odot}~yr^{-1}) = -1.26\pm0.12$ respectively. The pair has an isolated local environment, with no other
galaxies or H I sources within 30 arcmin (525 kpc) and $\pm1000$ km s$^{-1}$. However, in the context of the larger-scale structure, the pair is located outside the virial radius of the Hydra cluster, with its position on the phase-space diagram indicating that it is infalling into the cluster. The identification of this H I-bearing UDG pair raises important questions around the formation of such a unique system and the
evolution of UDGs in a transitional phase before ram pressure stripping and cluster infall.
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All authors T. O'Beirne, V. A. Kilborn, M. E. Cluver, O. I. Wong, N. Deg, K. Spekkens, N. Arora, R. Dudley, B. Catinella, H. Dénes, K. Lee-Waddell, P. E. Mancera Piña, C. Murugeshan, J. Rhee, L. Staveley-Smith, A. X. Shen, T. Westmeier
High Energy Astrophysical Phenomena
Interacting supernovae and where to find them
Robert Brose, Iurii Sushch, Jonathan Mackey et al. (+1 more)
Early interaction of
supernova blast waves with CSM has the potential to accelerate particles to PeV energies, although this has not yet been detected. Current models for this interaction assume the shock expands into a smooth
stellar wind, although observations of many SNe do not support this assumption. We extend previous work by considering shocks expanding into complex density profiles consisting of smooth winds with dense CSM shells at various distances from the progenitor
star. We aim to predict the gamma-ray and multiwavelength signatures of CSM interaction. We used the PION code to model the CSM around LBV including a brief episode of enhanced mass-loss and to simulate the formation of photoionization-confined shells around RSGs. Consequently, we used the time-dependent acceleration-code RATPaC to study the acceleration of
cosmic rays in SNe expanding into these media and to evaluate the emitted radiation across the whole electromagnetic spectrum. We find that the interaction with the CSM shells can significantly boost the gamma-ray emission, with the emission peaking weeks to years after the explosion. The peak luminosity for Type-IIP and Type-IIn remnants can exceed the luminosity expected for smooth winds by orders of magnitude. For Type-IIP explosions, the light-curve peak is only reached years after the explosion. We evaluate the multiwavelength signatures expected from the interaction of the blast wave with a dense CSM shell from
radio, over optical, to thermal X-rays. We identify high-cadence optical surveys and continuous monitoring of nearby SN in
radio and mm wavelengths as the best-suited strategies for identifying targets that should be followed-up by gamma-ray observatories. We predict that gamma-rays from interaction with dense CSM shells may be detectable out to a few Mpc for late interaction, and tens of Mpc for early interaction.
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All authors Robert Brose, Iurii Sushch, Jonathan Mackey, Maria Arias
High Energy Astrophysical Phenomena
The impact of superradiance on the spin evolution of variably accreting massive black holes
Adithya Nandakumar, Ricarda S. Beckmann and Vid Irsic
This paper explores how time-varying increases in mass
accretion onto rapidly spinning black holes influence their long-term
spin evolution when affected by superradiance - a process where energy is extracted from the black hole by a surrounding
axion field. Using simulations the study tracks how sudden
accretion boosts affect a critical
spin-down phase (the superradiance drop) during which the black hole's
spin rapidly decreases while its mass remains nearly constant. The black hole
spin evolution is controlled by the competition between two processes: how fast angular momentum is added through
accretion, and how fast it is removed by the
axion cloud. One major conclusion is that boosts to the
accretion rate before the superradiance drop have the strongest effect, as they can delay or reshape the drop and significantly shrink the region of the mass-
spin plane depopulated due to the superradiance. In particular, a super-Eddington
accretion rate of 5 times Eddington
accretion, lasting for 4 Myr and occurring 30 Myr before the superradiance drop can reduce the superradiance exclusion region in the mass-
spin plane by 40 percent. In contrast, boosts to the
accretion rate after the superradiance drop only cause temporary changes in the black hole
spin. The study also shows that black holes with lighter
axion clouds are more sensitive to these early boosts and can show observable
spin changes lasting tens to hundreds of millions of years. Heavier
axion clouds, however, require much stronger or longer-lasting boosts to produce similar effects, making them more stable under variable
accretion.
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High Energy Astrophysical Phenomena
Application and development of advanced mathematical tools for population and time series analysis in pulsar astrophysics
C.R. García
In this thesis, we introduce novel methods for analyzing
pulsar populations using a variety of mathematical techniques. These tools-particularly graph theory-have been thoroughly validated in advanced mathematics, enabling us to overcome some of the constraints (even dimensional) inherent in conventional visualization approaches. This exploration benefits from dimensionality reduction techniques, which not only lessen computational demands but also highlight potential for describing physical characteristics. The resulting structures encode information about
pulsar similarities that extend beyond standard
spin parameters, revealing relationships that are not readily apparent in traditional diagrams. With a physically motivated topological perspective, we leverage the strengths of these methods and present results that span from prospective source classification and the emergence of new classes to catalog comparison, among other applications. This new approach enables fresh interpretations of longstanding problems, laying a new foundation for visualizing the
pulsar population and categorizing sources. Building on this, we identify several sources as likely members of specific binary subclasses and investigate the potential transitional nature of others. Furthermore, we extend the use of graph theory to the boundary of machine learning, demonstrating its capability for binary separation in an unsupervised context. Finally, we introduce and apply an innovative, flexible time-series
alignment technique to the field of gamma-ray astrophysics. The method identifies notable similarities among the light curves of gamma-ray
pulsars. The results presented here are promising, offering a refreshing direction for the field and new pathways for rigorous mathematical analysis, ultimately providing meaningful alternatives to traditional approaches in high-energy astrophysics.
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Astrophysics of Galaxies
Modeling Globular Cluster Counts with Bayesian Latent Models
Rafael S. de Souza and Ana L. Chies-Santos
We present a
Bayesian latent model to describe the scaling relation between globular cluster populations and their host
galaxies, updating the framework proposed in de Souza 2015. GC counts are drawn from a negative-binomial (NB) process linked to host
stellar mass, augmented with a newly introduced Gaussian observation layer that enables efficient propagation of measurement errors. The revised formulation preserves the underlying NB process while improving computational tractability. The code snippets, implemented in Nimble and PyMC are released under the MIT license at https://github.com/COINtoolbox/Generalized-Linear-Models-Tutorial/blob/master/Count/readme.md
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High Energy Astrophysical Phenomena
Anomalous scattering of pulsars towards the Gum Nebula
M. A. Krishnakumar, Bhal Chandra Joshi and P. K. Manoharan
We report wideband scatter-broadening estimates of 14
pulsars towards the Gum nebula region using the Band-3 of the upgraded GMRT. This work increases the measurements of frequency scaling index of scatter-broadening ($\alpha$) across the nebula by more than 3 times. A strong correlation between the distance and the scattering strength is observed for
pulsars behind the nebula. It is also observed that for distant
pulsars ($> 2 kpc$), the effect of the Gum nebula in DM and scattering strength is not substantial. We also report a much flatter $\alpha$ for the Vela
pulsar and argue that its scattering is not caused by the Gum nebula, but the Vela
supernova remnant.
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Instrumentation and Methods for Astrophysics
Segmentation and Celestial Mapping of Unobservable Regions in Nighttime All-sky Images for the Mephisto Observations
Jian Cui, Guo-Wang Du, Xin-Zhong Er et al. (+5 more)
Accurate identification of unobservable regions in nighttime is essential for autonomous scheduling and data quality control in observations.Traditional methods-such as infrared sensing or photometric extinction-provide only coarse,non-spatial estimates of sky clarity,making them insufficient for real-time decision-making.This not only wastes observing time but also introduces contamination when
telescopes are directed toward cloud-covered or moonlight-affected regions.To address these limitations,we propose a deep learning-based
segmentation framework that provides pixel-level masks of unobservable areas using all-sky images.Supported by a manually annotated
dataset of nighttime images,our method enables precise detection of cloud- and moonlight-affected regions.The
segmentation results are further mapped to celestial coordinates through Zenithal Equal-Area projection,allowing seamless integration with observation control systems (OCS) for real-time cloud-aware scheduling.While developed for the Mephisto
telescope,the framework is generalizable and applicable to other wide-field robotic observatories equipped with all-sky monitoring.
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All authors Jian Cui, Guo-Wang Du, Xin-Zhong Er, Chu-Xiang Li, Jun-Fan Hou, Yu-Xin Xin, Xiang-kun Liu, Xiao-Wei Liu
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Charge distribution of the gauge-mediation type Q ball
Shinta Kasuya and Masahiro Kawasaki
We numerically study the formation of the gauge-mediation type Q balls in the logarithmic square potential on three-dimensional
lattices. We obtain the broad charge distribution of the Q ball of this type for the first time, to the best of our knowledge. The charge of the Q ball at the peak of the distribution is smaller than what we estimated as the average of the largest tens of the Q balls in the logarithmic potential for the same initial amplitude of the field at the onset of its oscillation. We also discuss some impacts of the broad distribution on cosmology and astrophysics. In the B ball (Q being the
baryon number) case, the broad distribution would lead to the coexistence of both stable and unstable B balls. We find that stable B balls can account for the dark matter of the universe without affecting successful big bang nucleosynthesis by the decay of the unstable B balls, but the
baryon number of the universe cannot be explained by them. On the other hand, the large L balls (Q being the
lepton number) would be the dark matter as well while avoiding the constraints on the X and/or gamma rays from the decay of the smaller L balls.
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Astrophysics of Galaxies
On the origins, growth, and radiative efficiency of J0529-4351, reportedly the fastest-growing known black hole
Yash Aggarwal
SMSS J0521-4351 is reportedly the most luminous
quasar known to date, and assuming a mean radiative efficiency of 0.1, it is inferred to be the fastest-growing black hole, accreting approximately one
solar mass per day. Assessing the implications of this assumption on the seed mass and inception time of J0529-4351, we show that the inferred
accretion rate is unreasonably high and that its radiative efficiency must be much greater than 0.1. Then, we derive its
accretion rate and seed mass, and for comparison of three other similar-size (~1-2E+10
solar masses) black holes at various
redshifts, using well-tested empirical scaling relations. The results indicate that J0529-4351 grew from a heavy seed (~2-3E+04
solar masses), and that its
accretion rate (~10-13
solar masses/year) is the lowest of the four black holes. However, its radiative efficiency inferred from its bolometric luminosity and the derived
accretion rate is the highest, which explains why it is the most luminous despite having the lowest
accretion rate. This study challenges the prevailing notion that a higher luminosity or a higher Eddington ratio implies a higher
accretion rate, highlights the dependence of a black hole's luminosity on radiative efficiency, reveals the pitfalls of inferring black hole properties assuming a standard value for radiative efficiency, and suggests that the Eddington ratios of high-luminosity BHs may be significantly overestimated.
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Cosmology and Nongalactic Astrophysics
Nearly Monochromatic Primordial Black Holes as total Dark Matter from Bubble Collapse
Haonan Wang, Ying-li Zhang and Teruaki Suyama
We propose a two-field model where the inflaton $\chi$ is non-minimally coupled to the instanton $\phi$. By choosing an appropriate coupling function, we realize the scenario where the difference of the values of potential between false
vacuum (FV) and true
vacuum (TV) is maximized during inflation. Most of the bubbles are created at this time. After inflation ends, the potential value of FV drops below that of TV so that these bubbles collapse to form
primordial black holes (PBHs). By tuning the parameters of our model, we analyze the Coleman-de Luccia (CDL) and Hawking-Moss (HM) process, finding that the corresponding mass function of PBHs is sharply peaked, implying that we can realize either PBHs as cold dark matter, sub-
solar PBHs, or supermassive PBHs in this scenario without enhancement of
primordial curvature perturbations.
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Cosmology and Nongalactic Astrophysics
BaryonBridge: Stochastic Interpolant Model for Fast Hydrodynamical Simulations
Benjamin Horowitz, Carolina Cuesta-Lazaro and Omar Yehia
Constructing a general-purpose framework for mapping between dark matter simulations and observable hydrodynamical simulation outputs is a long-standing problem in modern astrophysics. In this work, we present a new approach utilizing
stochastic interpolants to map between cheap fast particle mesh simulations and baryonic quantities in three dimensions, requiring a total of 7 GPU minutes per 256^3 grid size simulation. Using the CAMELS multifield
dataset, we are able to condition our mapping on both cosmological and astrophysical properties. We focus this work on hydrodynamical quantities suitable for Lya observables finding excellent agreement up to small spatial scales, k ~ 10.0 (h^(-1) Mpc) at z=2.0, for Lya flux statistics. Our approach is fully convolutional, allowing training on comparatively small volumes and application to larger volumes, which was tested on TNG50.
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High Energy Astrophysical Phenomena
An XMM long look at the accretion disk plasma in the dipping neutron star LMXB 4U1624-490
Eleonora Caruso, Elisa Costantini, Nathalie Degenaar et al. (+1 more)
Dipping
neutron star low-mass X-ray binaries (NS LMXBs) are systems that exhibit periodic drops in their X-ray light curves. These are believed to be caused by material at the impact point of the gas stream onto the
accretion disk, the bulge. Dipping systems are observed at high inclination and provide exceptional opportunities to address important open questions about
accretion disks, such as the physical properties of the bulge, and the connection between disk atmospheres and disk winds. We aimed to characterize the
accretion disk
plasmas present in the 21h-period NS LMXB 4U 1624-490, and perform a detailed spectral analysis of the material present at the impact region. We used four XMM EPIC pn observations that were specifically targeting dips, and allow us to probe dipping activity over different timescales (i.e. consecutive orbits and $\sim$6 months). We use both time- and flux-resolved spectroscopic analysis to probe the structural properties of the bulge moving along the line of sight and its homogeneity, respectively. During dipping, the primary spectrum is modulated by an ionized (log$\xi\sim$ 3.4) absorber with varying column density and covering factor, as well as a colder absorber. This suggests that the bulge is a multiphase and clumpy absorbing medium. From size scale arguments, we estimate the number of clumps in the bulge to be $>$7$\times10^{3}$. A highly ionized disk atmosphere becomes evident only when different phases of absorption are analyzed individually. This work demonstrates the feasibility of constructing a physical picture of the bulge, and highlights how future research could reveal how its properties depend on system parameters, and whether the bulge could influence the dynamics of the
accretion disk.
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All authors Eleonora Caruso, Elisa Costantini, Nathalie Degenaar, Maria Diaz Trigo
Cosmology and Nongalactic Astrophysics
Transfer Learning Beyond the Standard Model
Veena Krishnaraj, Adrian E. Bayer, Christian Kragh Jespersen et al. (+1 more)
Machine learning enables powerful cosmological inference but typically requires many high-fidelity simulations covering many cosmological models. Transfer learning offers a way to reduce the simulation cost by reusing knowledge across models. We show that pre-training on the standard model of cosmology, $\Lambda$CDM, and fine-tuning on various beyond-$\Lambda$CDM scenarios – including massive
neutrinos, modified
gravity, and
primordial non-Gaussianities – can enable inference with significantly fewer beyond-$\Lambda$CDM simulations. However, we also show that negative transfer can occur when strong physical degeneracies exist between $\Lambda$CDM and beyond-$\Lambda$CDM parameters. We consider various transfer architectures, finding that including bottleneck structures provides the best performance. Our findings illustrate the opportunities and pitfalls of foundation-model approaches in physics: pre-training can accelerate inference, but may also hinder learning new physics.
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All authors Veena Krishnaraj, Adrian E. Bayer, Christian Kragh Jespersen, Peter Melchior
Earth and Planetary Astrophysics
A Compact Multi-Planet System of Three Transiting Giant Planets Around TIC118798035
Rafael Brahm, Trifon Trifonov, Andrés Jordán et al. (+20 more)
We report the discovery and characterization of three transiting
giant planets in the TIC118798035 system. The three
planets were identified as transiting candidates from data of the TESS mission, and confirmed with ground-based photometric transit observations along with radial velocity variations obtained with FEROS, HARPS and ESPRESSO. The three
planets present transit timing variations (TTVs). We performed a N-body orbital fitting to the TTVs and radial velocities finding that TIC118798035 b is as warm low-density Neptune with a mass of 0.0250$\pm$0.0023 $M_J$, a radius of 0.655$\pm$0.018 $R_J$, and an orbital period of 11.507 d; TIC118798035 c is a warm Saturn with a mass of 0.403$\pm$0.024 $M_J$, a radius of 0.973$\pm$0.023 $R_J$, and an orbital period of 22.564 d; and TIC118798035 d is a warm Jupiter with a mass of 0.773$\pm$0.052 $M_J$, a radius of 0.923$\pm$0.044 $R_J$, and an orbital period of 48.925 d. The bulk
metallicities of the three
planets don't fully follow the mass-
metallicity correlation found for the
giant planets of the
solar system, which hints at a somewhat different formation history for the
planets of the TIC118798035 system. TIC118798035 is the only system having more than two transiting
planets larger than 0.5 $R_J$ with a precise orbital and physical characterization, amenable for future atmospheric studies.
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All authors Rafael Brahm, Trifon Trifonov, Andrés Jordán, Thomas Henning, Néstor Espinoza, Felipe I. Rojas, Marcelo Tala Pinto, Matías I. Jones, Daniel Thorngren, Lorena Acuña, Jan Eberhardt, Yared Reinarz, Helem Salinas, Michaela Vítková, Juan I. Espinoza-Retamal, Gaspar Bakos, Attila Bódi, Gavin Boyle, Zoltan Csubry, Joel Hartman, Anthony Keyes, Vincent Suc, Geert Jan Talens
Cosmology and Nongalactic Astrophysics
$H_0$ Without the Sound Horizon (or Supernovae): A 2% Measurement in DESI DR1
E. A. Zaborowski, P. Taylor, K. Honscheid et al. (+58 more)
The sound horizon scale $r_s$ is a key source of information for early-time $H_0$ measurements, and is therefore a common target of new physics proposed to solve the Hubble tension. We present a sub-2% measurement of the Hubble constant that is independent of this scale, using data from the first data release of the Dark Energy Spectroscopic Instrument (DESI DR1). Building on previous work, we remove dependency on the sound horizon size using a heuristic rescaling procedure at the power spectrum level. A key innovation is the inclusion of uncalibrated (agnostic to $r_s$) post-reconstruction BAO measurements from DESI DR1, as well as using the CMB acoustic scale $\theta_*$ as a high-
redshift anchor. Uncalibrated type-Ia
supernovae are often included as an independent source of $\Omega_m$ information; here we demonstrate the robustness of our results by additionally considering two
supernova-independent alternative
datasets. We find somewhat higher values of $H_0$ relative to our previous work: $69.2^{+1.3}_{-1.4}$, $70.3^{+1.4}_{-1.2}$, and $69.6^{+1.3}_{-1.8}\,{\rm km\,s^{-1}\,Mpc^{-1}}$ respectively when including measurements from i) Planck/ACT CMB
lensing $\times$ unWISE
galaxies, ii) the DES Year 3 6$\times$2pt analysis, and iii) Planck/ACT CMB
lensing + the DES Year 5
supernova analysis. These remarkably consistent constraints achieve better than 2% precision; they are among the most stringent sound horizon-independent measurements from LSS to date, and provide a powerful avenue for probing the origin of the Hubble tension.
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All authors E. A. Zaborowski, P. Taylor, K. Honscheid, A. Cuceu, A. de Mattia, A. Krolewski, M. Rashkovetskyi, A. J. Ross, C. To, J. Aguilar, S. Ahlen, A. Anand, S. BenZvi, D. Bianchi, D. Brooks, F. J. Castander, T. Claybaugh, A. de la Macorra, J. Della Costa, P. Doel, S. Ferraro, A. Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, G. Gutierrez, H. K. Herrera-Alcantar, C. Howlett, D. Huterer, M. Ishak, R. Joyce, D. Kirkby, T. Kisner, A. Kremin, O. Lahav, C. Lamman, M. Landriau, L. Le Guillou, M. Manera, P. Martini, A. Meisner, R. Miquel, J. Moustakas, S. Nadathur, G. Niz, N. Palanque-Delabrouille, W. J. Percival, F. Prada, I. Pérez-Ràfols, G. Rossi, L. Samushia, E. Sanchez, D. Schlegel, M. Schubnell, H. Seo, J. Silber, D. Sprayberry, G. Tarlé, B. A. Weaver, P. Zarrouk, R. Zhou, H. Zou
High Energy Astrophysical Phenomena
Fast Radio Bursts
J. I. Katz
Eighteen years after their discovery, the astronomical sources and radiation mechanisms of fast
radio bursts remain mysterious. Their radiation is as bright as that of
pulsars, with brightness temperatures as high as $\sim 10^{36}$ K, implying coherent emission, but the
plasma physics that forms the coherent charge bunches, with net charges of order a Coulomb, is not understood. Some FRB have been identified with
galaxies at
redshifts of a few tenths, but one originated within a globular cluster in the
galaxy M81 at a distance of 3.6 Mpc. A minority of FRB have been observed to repeat, in some cases thousands of times. The vast majority of FRB have not been observed to repeat, but it is not known if they are truly “one-offs” or repeat at unobservably long intervals. Some FRB originate within dense, rapidly varying,
plasma environments, while others appear to be surrounded by high
vacuum. Hypotheses for their sources include magnetars and black hole
accretion discs.
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