High Energy Astrophysical Phenomena
Parameter Estimation Horizon of Core-Collapse Supernovae with Current and Next-Generation Gravitational-Wave Detectors
Almat Akhmetali, Y. Sultan Abylkairov, Daniil Orel et al. (+7 more)
Core-collapse
supernovae (CCSNe) are powerful sources of gravitational waves (GWs). These signals propagate essentially unobstructed, providing a unique probe of the
supernova central engine. In this work, we investigate parameter estimation from the bounce and early ring-down GW signal of rotating CCSNe using machine learning. We infer the peak frequency and peak amplitude of the signal as well as the rotation of the core. We extend previous studies in several directions. We consider a range of progenitor models and
nuclear equations of state, and we assess the impact of key physical uncertainties, including bounce-time uncertainty and source inclination. We incorporate both current detector noise and the projected sensitivities of next-generation observatories. We find that uncertainty in the bounce time does not significantly affect parameter estimation when the analysis is performed in the
Fourier domain. In contrast, orientations when the rotation axis is near the line of sight substantially degrade performance. For optimal orientations, next-generation detectors can constrain rotation out to distances exceeding 100 kpc.
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All authors Almat Akhmetali, Y. Sultan Abylkairov, Daniil Orel, Solange Nunes, Aknur Sakan, Alisher Zhunuskanov, Marat Zaidyn, Nurzhan Ussipov, José Antonio Font, Ernazar Abdikamalov
High Energy Astrophysical Phenomena
Sensitivity of the Cherenkov Telescope Array Observatory to Gamma-Ray Signals in Dwarf Irregular Galaxies
Jaume Zuriaga-Puig, Viviana Gammaldi and Miguel Á. Sánchez-Conde
Dwarf irregular
galaxies (dIrrs) are rotationally supported
galaxies with a low
star formation rate. Thus, their gamma-ray astrophysical emission is expected to be low, making them interesting targets for WIMP dark matter (DM) indirect searches. In this work, we build upon previous work on these objects in this DM context, and identify the best four dIrrs to be observed by the forthcoming Cherenkov
Telescope Array Observatory (CTAO). Since dIrrs have not been detected in gamma rays yet, we first explore the prospects for detecting their astrophysical emission with the CTAO. Secondly, we compute the CTAO sensitivity prospects to a DM annihilating signal from these objects, accounting for the presence of DM substructures in them. We do so for both cuspy and cored DM density profiles, as the cusp-core debate remains particularly open for dIrrs. Our best combined limits show the potential to exclude DM annihilation cross-section values around $2\times 10^{-24} \ \mathrm{cm^{3}}\mathrm{s^{-1}}$ for 100 GeV WIMP masses annihilating in the $\tau^+\tau^-$ channel. These prospective results are competitive with and complementary to
benchmark targets such as
galaxy clusters. We also analyze the case of the velocity-dependent annihilation cross-section (Sommerfeld enhancement), obtaining projected DM constraints that exceed those expected for
dwarf spheroidal
galaxies, thanks to the contribution of subhalos to the signal. We conclude that dIrrs are compelling targets for the CTAO, not only for DM indirect searches but also as possible astrophysical sources.
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Earth and Planetary Astrophysics
Exploration of the inner region of the system HD 142527
T. M. H. Tran, M. Langlois, O. Flasseur et al. (+6 more)
HD 142527 is a well-studied intermediate-mass T Tauri
star surrounded by a transitional disk with a large
dust cavity, spiral structures, and an accreting low-mass companion. Despite extensive observations, the system's inner regions remain poorly understood, particularly regarding their influence on disk morphology and
planet formation. This study aims to investigate the inner region of HD 142527 (<50 au) with high detection sensitivity thanks to dedicated postprocessing methods to search for undetected components and explore their potential role affecting the disk's structure and
evolution. We analyze high-contrast imaging data obtained with VLT/SPHERE applying PACO and REXPACO
algorithms, dedicated respectively to the detection of point-like sources and to the reconstruction of circumstellar disks with high reliability, while relying on both angular and spectral variations. We revisit the known companion HD 142527 B and update its photometry, astrometry and
accretion rate estimates. Furthermore, we identify a new candidate companion (CC) at an angular separation of ~0.09" (~14 au), although it may also be a disk feature. Otherwise, it could be a young gas-
giant planet or a brown
dwarf with a mass of 12-50 $M_\rm{Jup}$. Additionally, we report the discovery of a tightly wound H$\alpha$ spiral feature in the inner disk, reconstructed for the first time by high contrast imaging. The spiral implies varying
accretion dynamically linked to the known companion B and possibly to CC, suggesting ongoing interactions that influence the disk's structure. Our findings provide new insights into the complex interactions within the HD 142527 system, highlighting the role of multiple companions in driving disk asymmetries and facilitating
planet formation. Future high-resolution observations and dynamical modeling will be essential to fully understand the system's architecture and
evolution.
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All authors T. M. H. Tran, M. Langlois, O. Flasseur, J.-C. Augereau, A. Boccaletti, P. Delorme, R. Gratton, A. Kaszczyc, A.-M. Lagrange
Cosmology and Nongalactic Astrophysics
Efficient estimators for power spectrum and bispectrum multipole measurements
Yunchen Xie, Ruiyang Zhao, Gan Gu et al. (+6 more)
Large
galaxy surveys demand fast and scalable
estimators for anisotropic clustering statistics beyond the monopole. We present a suite of efficient FFT-based
estimators for power-spectrum and bispectrum multipoles, built upon exact conjugation and parity
symmetries of spherical-harmonic–weighted
Fourier transforms of real fields. These
symmetries eliminate redundant
magnetic sub-configurations, thereby reducing the computational cost by a factor of 2. For the Yamamoto power-spectrum multipoles, we further decrease the cost of high-order even multipoles by algebraically expressing ${L}_{2n}$ in terms of lower-order Legendre
polynomials, thereby measuring modified high-order multipoles using only low-$\ell$ fields with a small and controlled deviation from the traditional definition. We introduce a new TripoSH bispectrum
estimator obtained by compressing the Scoccimarro bispectrum along an alternative triangle side, which substantially reduces the FFT scaling for commonly used quadrupole configurations in the large-$k$-bin limit. We also derive an analytic treatment of bispectrum shot noise by integrating spherical-harmonic kernels over the triangle-constrained $k$-space volumes, avoiding additional FFTs or costly spherical-Bessel evaluations and enabling fast and accurate shot-noise subtraction. Based on these optimizations, we also introduce CosmoNPC, an open-source Python package for large-scale-structure clustering measurements.
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All authors Yunchen Xie, Ruiyang Zhao, Gan Gu, Xiaoma Wang, Xiaoyong Mu, Yuting Wang, Gong-Bo Zhao, Florian Beutler, John A. Peacock
High Energy Astrophysical Phenomena
Bayesian parameter estimation for the Core-bounce phase of Rapidly Rotating Core-Collapse Supernovae in real interferometric data
Emmanuel Avila, Michele Zanolin, Javier M. Antelis et al. (+1 more)
We present a novel methodology to estimate the ratio of kinetic to gravitational potential energy in core-collapse
supernova progenitors and to assess the equation of state (EOS) using gravitational-wave signals from the core-bounce phase of rapidly rotating
stars in real interferometric data. We extend a previous phenomenological model by introducing an additional parameter that captures the signal timescale. The agreement between our template and numerical waveform databases is evaluated through fitting factors and
Bayesian model comparison, also assessing consistency across
datasets. The improved model increases the median fitting factor from 88.88% to 90.83%. Parameter estimation is performed via Markov Chain Monte Carlo using real O3aL1 noise. For 452 simulated signals, the rotational parameter $\beta$ is recovered with a median relative error of 11.93% (95th percentile: 38.41%) and an uncertainty of $\sigma_\beta = 1.083 \times 10^{-3}$ at 10 kpc, improving over previous matched-filtering results. We further analyze the impact of prior choices and noise properties, finding that real interferometric noise introduces biases up to 11.9%, while optimized priors can reduce them to 0.6%.
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All authors Emmanuel Avila, Michele Zanolin, Javier M. Antelis, Claudia Moreno
Earth and Planetary Astrophysics
Earth and Mars interior structures set by re-melting of the first solid mantle
Antonio Manjón-Cabeza Córdoba, Maxim D. Ballmer and Oliver Shorttle
Magma ocean crystallisation sets up the early structure and long-term
evolution of terrestrial
planets. Recent seismic evidence signals the presence of a silicate layer at the base of Mars' mantle. Magma-ocean crystallisation and subsequent overturn has been invoked as a hypothesis for this layer's origin. However, while a magma ocean existed in both Earth and Mars, there is no seismic evidence for a basal layer in present-day Earth. In this study, we apply a parameterized-convection model to study whether the effect of partial melting in the growing mantle on overlying magma ocean composition can explain this discrepancy. Melts from the mantle buffer the crystallising magma ocean, limiting progressive differentiation, iron enrichment and the density anomaly of the overturned layer. This buffering is more efficient for larger
planets with more vigorous mantle convection and for
planets that are originally less enriched in iron. Consequently, a shallow magma ocean is more iron enriched and denser on Mars than on Earth, providing an explanation for the Mars-Earth difference in present-day structure of the mantle. We also predict a dichotomy in terrestrial-
exoplanet interior structures, with a population with small, stratified mantles and another with large, mostly-homogeneous mantles.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Singlet-doublet dark matter induced radiative neutrino mass and TeV scale leptogenesis
Partha Kumar Paul, Narendra Sahu and Shashwat Sharma
The singlet-doublet dark matter (SDDM) model is a well-motivated WIMP framework that accommodates viable DM over a broad range of parameter space. In this work, we explore the possibility of TeV-scale leptogenesis within two realizations of the SDDM setup: Majorana SDDM scenario and Dirac SDDM scenario. The light
neutrino mass, in either case, arises radiatively at one loop level. The particles running in the loop are responsible for DM relic and TeV-scale leptogenesis while satisfying other phenomenological constraints. In the Majorana setup, the Standard Model is extended by three generations of singlet
fermions $N_i$ and doublet
fermions $\Psi_i$, and a singlet scalar $\phi$. The CP-violating, out-of-
equilibrium decays of the heavier singlets ($N_{2,3}$) generate
baryon asymmetry via the leptogenesis route, while the first generation of singlet-doublet
fermions give rise to the usual SD Majorana DM. In the Dirac setup, the standard model is extended by three generations of complex scalars ($\phi_i$) and right-handed Dirac partners ($\nu_{R_i}$) of SM
neutrinos ($\nu_{L_i}$), along with a pair of singlet-doublet
fermions $\chi$ and $\Psi$. The CP-violating out-of-
equilibrium decays of the scalar fields $\phi_i$ generate
baryon asymmetry via the Dirac leptogenesis route. We show that in the Majorana setup, successful leptogenesis is possible even in the sub-TeV regime, whereas in the Dirac setup, the leptogenesis scale is at a few TeV. With the particle mass at the TeV scale, the model remains promising for
collider experiments, particularly through signatures such as
prompt decays and displaced vertex searches. In addition, the presence of Dirac
neutrinos can contribute to $\Delta N_{\rm eff}$, providing complementary cosmological signatures.
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High Energy Astrophysical Phenomena
AGILE detection of transient {\gamma}-ray emission from the region of the supergiant fast X-ray transient source IGR J17354-3255
Andrea Bulgarelli, Gabriele Panebianco, Vito Sguera et al. (+16 more)
Context. On April 14, 2009, the AGILE satellite detected a {\gamma}-ray
flare from an unknown transient source. Subsequent X-ray follow-up observations with Swift and INTEGRAL identified the supergiant fast X-ray transient (SFXT) IGR J17354-3255 as the best candidate counterpart, based on positional coincidence and a similar temporal behaviour. Aside from this hint, no SFXT has been firmly detected at high energies to date. Overall, SFXTs comprise a subclass of high-mass X-ray binaries (HMXBs) that host a massive OB supergiant
star as a companion donor. They tend to display the most extreme X-ray variability among HMXBs. These systems might be able to emit
photons at MeV-TeV energies in the form of fast
flares lasting from hours to a few days, with a low-duty cycle. Aims. In this work, we analyse archival AGILE data to search for {\gamma}-ray
flares consistent with IGR J17354-3255 and evaluate their possible physical origin. Methods. We identified a transient source, AGL J1736-3250, which emitted 19 {\gamma}-ray
flares and was seen to be positionally consistent with IGR J17354-3255. Most
flares, detected on a 1 d timescale, concentrate most of their emission on two, four, and six hour timescales, resembling those observed in the X-ray band from IGR J17354-3255. Results. An orbital phase analysis revealed that approximately half of the {\gamma}-ray activity occurs around the apastron passage of the compact object hosted in the binary system. We also incorporated archival Swift and INTEGRAL observations to provide phase-folded light curves at lower energies. Our collected results strongly support a physical association between IGR J17354-3255 and AGL J1736-3250, offering evidence that SFXTs could constitute a new class of
Galactic high-energy transient emitters.
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All authors Andrea Bulgarelli, Gabriele Panebianco, Vito Sguera, Marco Tavani, Valentina Fioretti, Ambra di Piano, Nicolò Parmiggiani, Patrizia Romano, Stefano Vercellone, Alessio Aboudan, Francesco Longo, Giacomo Principe, Francesco De Palma, Emanuele Dolera, Carlotta Pittori, Fabrizio Lucarelli, Francesco Verrecchia, Andrew W. Chen, Angela Bazzano
Cosmology and Nongalactic Astrophysics
Primordial black holes from inflation: on the decoupling between large and small scales
Laura Iacconi
Primordial black holes (PBHs) can be produced from inflation if the
primordial curvature power spectrum is strongly enhanced on scales much shorter than those probed by
cosmic microwave background (CMB) experiments. In single-field models this typically requires a transient departure from slow-roll, attractor dynamics, for example realized through a brief ultra-slow-roll phase. In these scenarios, there is reasonable concern that large-scale modes, whose statistics is tightly constrained by CMB observations, might back-react to the amplified perturbations on much shorter scales. In a perturbative expansion for the long-mode power spectrum, this effect first appears at 1-loop. In these proceedings we summarize recent works on this issue, based on the application of the separate-universe framework and its general extension with multi-point propagators. We show that back-reaction at 1-loop is due to either (i) non-linear super-horizon
evolution, or (ii) 1-loop-corrected initial conditions. By assuming separation of scales and adiabaticity of the long mode, we show that the 1-loop back-reaction is not observable and large scales decouple from enhanced short ones. While we demonstrate that PBH production within single-field inflation does not disrupt large-scale predictions, we close by discussing scenarios to which our results do not apply.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Charged current neutrino processes in hot nuclear matter with a recent Skyrme parametrization constrained by microscopic calculations
Mingya Duan and Michael Urban
Neutrino processes are important in the modeling of
supernova explosions, proto-
neutron star evolution, and binary
neutron star mergers. We study
neutrino production and absorption in proto-
neutron star and
supernova matter and direct Urca
neutrino emission of
neutron star matter in the framework of the random phase approximation (RPA). As interactions, we employ the recent extended Skyrme parametrization Sky3s whose effective masses and
spin-dependent terms were adjusted to microscopic calculations, and the SLy4 parametrization that was used in previous calculations of
neutrino rates. The rates obtained for Sky3s differ from those for SLy4 by up to one order of magnitude for some processes and energy regions. We also determine the electron,
muon, and
proton fractions that lead to a stationary composition of matter for a density above the direct Urca threshold, and find that with Sky3s the standard $\beta$
equilibrium condition is not as badly violated at finite temperature as predicted in the literature. There are also minor differences between the full RPA and the common Landau approximation, but they are probably not significant for astrophysical simulations. We conclude that it would be worthwhile to repeat the calculation of
neutrino rates for the use in astrophysical simulations, and the corresponding simulations, with several and better constrained interactions than SLy4, such as Sky3s.
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Astrophysics of Galaxies
Connecting the long-term variability behaviour of active galactic nuclei to their central engines
Sofia Kankkunen, Merja Tornikoski and Talvikki Hovatta
Analysing the long-term
radio variability of active
galactic nuclei (AGNs) is essential to understanding the physics of relativistic jets launched by supermassive black holes. We aim to connect the characteristic timescales obtained from a prior power spectral density (PSD) analysis to the decomposed timescales of the light curves. In addition, we probe for potential associations between the timescales and the physical characteristics of the relativistic jet as well as the central engine. We decomposed the long-term
radio light curves of 54 sources observed at the Aalto University Metsähovi
Radio Observatory into individual
flares to understand which timescale of variability is related to the low-frequency bend in the PSD. In addition, we used the obtained rise times of the brightest
flares to look for associations between the emission-region size in the jet and different central engine parameters. We found that the inverse of the PSD bend frequency of
radio light curves best corresponds to the mean duration of the brightest
flares. For some sources, the mean
flare separation had a similar timescale. Using the
flare durations and separations as proxies for the PSD timescale, we found a positive correlation with black hole mass divided by the normalised mass
accretion rate. This suggests that the variability timescales obtained from the PSDs of
radio light curves are associated with the central engine. Furthermore, when comparing the obtained rise times of the brightest
flares to the jet and central engine parameters, we found weak tentative correlations, but they may be driven by a common dependency on
redshift.
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Astrophysics of Galaxies
Contribution of interstellar objects to local dark matter density
Dieter Horns, Niklas Knop and Mohammad Mohammadidoust
The recent discovery of three interstellar comets in the
solar system indicates the presence of so-far unaccounted baryonic matter in the
Galaxy as a population of inter-
stellar objects (ISO). The contribution of ISOs to the overall mass budget of the
Galaxy affects the estimates on mass of the non-baryonic dark matter
halo. We are attempting to estimate the mass density of non-baryonic Dark Matter after including a
Galactic ISO contribution to the
Galactic rotation curve. The object 3I/ATLAS is a surprisingly massive object with estimates of the
nuclear radius reaching up to few kilo-metres. The observed incidence rate of interstellar objects (ISO) passing through the inner
solar system in combination with estimates on the mass density and size provides an estimate of the local mass density if ISOs in the interstellar medium. The resulting estimate carries large uncertainties which are the consequence of the difficulties to constrain or measure the
nuclear radius. The large kinematic age of 3I/ATLAS motivates a model where ISO objects are distributed in a thick (0.8~kpc) disk with a large radial scale length of $\approx 7$~kpc estimated from a fit to rotational velocity measurements from
GAIA DR3 data. We find that the ISO contribution to the baryonic mass budget could reach a total mass of $5\times 10^{10}~M_\odot$ which leads to a reduction of the local Dark Matter
halo density to $0.24$~GeV/cm$^3$. Even though this scenario requires an overly optimistic fraction of matter to be released in the form of ISO objects, it is plausible that the local Dark Matter
halo density is biased towards large values given our ignorance of non-detectable baryonic matter in the
Galaxy.
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High Energy Astrophysical Phenomena
Exact solutions, trajectories and radiation patterns in the classical relativistic Störmer problem
Tiberiu Harko and Francisco S. N. Lobo
We investigate the relativistic generalization of the classical Störmer problem, which describes the motion of charged particles in a purely
magnetic dipole field. By incorporating special relativistic effects, the particle dynamics is governed by a strongly nonlinear system of second-order differential equations derived from the Lorentz force law. We present a rigorous and fully covariant derivation of the relativistic equations of motion, together with the associated conservation laws. An exact solution for planar motions is obtained in parametric form, providing analytical insight into the structure of the trajectories. In addition, we perform a detailed numerical analysis of the particle dynamics across both nonrelativistic and relativistic regimes, exploring a range of initial conditions and highlighting the impact of relativistic corrections. The electromagnetic radiation emitted by the accelerated charges is also examined. We compute the time dependence of the total radiated power and determine the corresponding frequency spectrum. Our results provide a comprehensive characterization of
magnetic dipole–type radiation associated with Störmer-like motion. In particular, the power spectral density consistently exhibits distinct peaks, indicating the presence of preferred frequency bands in the emitted radiation.
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Instrumentation and Methods for Astrophysics
The Next-Generation 21CMA Telescope: Design, Commissioning, and Instrumental Effects in an SKA-LFAA-Like System
Jun-Hua Gu, Quan Guo, Liang Dong et al. (+11 more)
As the Square Kilometre Array (SKA) approaches operational status, its complex digital architecture introduces new instrumental challenges. To explore relevant observational and data processing strategies, we have upgraded the 21CMA
telescope to the Next-Generation 21CMA (Ng21CMA). This paper presents the design and commissioning of the Ng21CMA system, featuring a digital backend capable of real-time beamforming. We demonstrate its performance through interferometric observations and high-time-resolution
pulsar measurements, validating the system's sensitivity and operational stability. As a representative example of instrumental effects accessible with this platform, we investigate the impact of the two-stage channelization strategy used in SKA-LFAA-like systems. We show that it introduces a sawtooth-like spectral structure (SLOSS), characterized using both simulations and observational data. These results provide useful references for understanding instrument-induced spectral features and for guiding system design and calibration in future large-scale aperture arrays.
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All authors Jun-Hua Gu, Quan Guo, Liang Dong, Yu-Kai Zhou, Kuan-Jun Li, Yan Huang, Jing-Ying Wang, Wei-Wei Zhu, You-Ling Yue, Rui Cao, Guo-Liang Peng, Xiao-Hui Tao, Li-Hui Jiang, Ya-Jun Wu
Earth and Planetary Astrophysics
Accessible does not mean exploitable: HiPERCAM reveals the ultra-fast rotation of 2022 OB$_5$
Miguel R. Alarcon, Javier Licandro, Miquel Serra-Ricart et al. (+2 more)
2022 OB$_5$ is a sub-10-metre Apollo-type near-Earth asteroid whose orbital configuration placed it among the most dynamically accessible small bodies in near-Earth space, motivating its selection as the target of the first commercial asteroid-prospecting mission. We present its first photometric characterisation, based on high-cadence simultaneous five-band $u_sg_sr_si_sz_s$ observations obtained with HiPERCAM at the 10.4-m Gran Telescopio Canarias (GTC). Analysis of the light curves yields a rotation period of $P_{\rm rot} = 1.542 \pm 0.001$ min, independently confirmed with observations taken by the Two-meter Twin
Telescope, establishing 2022 OB$_5$ as an ultra-fast rotator. The reflectance spectrum derived from the simultaneous multiband photometry is featureless and moderately red, consistent with the X-complex. Despite its good orbital accessibility, the ultra-fast rotation of 2022 OB$_5$ poses severe practical challenges for any surface operation with current technology, regardless of compositional interest. This illustrates a population-level challenge: at the sizes and $\Delta v$ values most favourable for in-situ missions, fast rotation is the dominant
spin state, and rotation period measurement is therefore an indispensable prerequisite for evaluating the resource potential of asteroid mission candidates.
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All authors Miguel R. Alarcon, Javier Licandro, Miquel Serra-Ricart, David Garcia-Álvarez, Antonio Cabrera-Lavers
Astrophysics of Galaxies
Statistical evidence for massive black hole recoils in active galactic nuclei
Bence Bécsy, Peter Raffai, Zoltán Haiman et al. (+2 more)
We search for a population-level signature of gravitational-wave recoiling supermassive black holes: a positive correlation between
dust obscuration and the magnitude of the line-of-sight velocity offset of broad emission lines relative to the host. Using the SDSS DR16
quasar catalogue, we estimate the velocity offset, $\Delta v$, as the difference between the broad H$\beta$
redshift and a noise-weighted
redshift from narrow lines ([O III] 5007, [O II] 3728, and Ca II 3934). We adopt the
redshift-relative colour excess $\Delta(g-i)$ as a proxy for
dust column density. Analysing $\sim10^{5}$
quasars that meet basic spectral quality requirements, we find a modest but highly significant positive correlation between $|\Delta v|$ and $\Delta(g-i)$ (Spearman $r\simeq0.12$ and Pearson $r\simeq0.13$, with $p\ll10^{-10}$ in both cases). The fraction of highly obscured
quasars increases with $|\Delta v|$, indicating that the correlation is driven by a
dust-reddened subpopulation. The result is robust to the choice of minimum $|\Delta v|$ threshold and to the line
redshift estimator (peak vs. centroid). As expected, the correlation is largely absent when velocity offsets are computed between narrow emission lines. We find systematic differences between redshifted and blueshifted subsamples, which may point to residual velocity biases or additional physical effects (e.g. winds, inflows, orientation-dependent obscuration, or asymmetric broad-line regions). Recoiling massive black holes provide a natural explanation for the observed correlation, but alternative scenarios should be explored. If confirmed, this would enable population-level constraints on massive black hole merger rates,
recoil dynamics, and active
galactic nuclei disc properties.
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All authors Bence Bécsy, Peter Raffai, Zoltán Haiman, Andor Budai, Zsolt Frei
Astrophysics of Galaxies
Redshift Evolution of the Ratio of Supermassive Black Hole Mass to Stellar Mass
Ziyong Wu, Renyue Cen and Romain Teyssier
We run and analyze a suite of high-
redshift zoom-in cosmological simulations with varying
supernova feedback and supermassive black hole (SMBH)
accretion prescriptions to study the joint
evolution of
stellar and SMBH mass in high-
redshift galaxies down to $z=10$. The simulations reproduce the observed high-$z$ $M_{\mathrm{BH}}/M_{\star}$ relation if super-Eddington
accretion is allowed prior to the final self-regulated phase. To extend the
evolution to lower
redshift, we model subsequent black hole and host growth using analytic
halo assembly histories combined with a
redshift-dependent effective Eddington duty cycle, $f_{\rm duty}=0.0004(1+z)^3$, calibrated to observations at $z\le6$, with conservative uncertainties at higher
redshift. Within this framework, $M_{\mathrm{BH}}/M_{\star}$ exhibits a broad peak at $z\sim7$–10, reaching a few percent up to $\sim30\%$, followed by a steady, approximately power-law decline toward $z=0$. The model predicts $M_{\mathrm{BH}}/M_{\star}\sim(0.002,0.003,0.006,0.016,0.071,0.156)$ at $z=(0,1,2,3,5,10)$, consistent with available observations. This
evolution is driven by rapid SMBH growth at high
redshift, with effective mass e-folding times shorter than those of
stellar mass, while at later times
galaxy growth dominates, leading to the decline in $M_{\mathrm{BH}}/M_{\star}$. These results demonstrate that the emergence of a high-
redshift peak and subsequent decline is robust despite uncertainties in the duty-cycle normalization.
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High Energy Astrophysical Phenomena
Confirmation of Binary Clustering in Gamma-Ray Bursts through an Integrated $p$-value from Multiple Nonparametric Tests of Hypotheses
Soumita Modak
The paper applies a new, nonparametric, interpoint distance-based measure to confirm the inherent groups prevailing in the brightest source of light in the universe: gamma-ray bursts. Our effective metric, in association with clustering methods like Gaussian-mixture model-based and $K$-means
algorithms, resolves the conflict regarding the possibility about existence of more than binary clusters in the gamma-ray burst population. Here we carry out multiple nonparametric statistical tests of hypotheses, as many as the number of bursts available from the `BATSE' catalog. An integrated $p$-value achieved from the aforesaid dependent tests solves our concern confirming two groups of short and long bursts.
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Earth and Planetary Astrophysics
Activity and composition of periodic comets 67P/Churyumov-Gerasimenko and 103P/Hartley 2 at two different perihelion passages
E. Hemmen, M. Vander Donckt, E. Jehin et al. (+6 more)
Through photometry and spectroscopy, we studied the
evolution of the activity and chemical composition of comet 67P during its 2025 and 2021 perihelion passages and of comet 103P during its 2010 and 2023 passages. For each comet, we aim to compare their behavior from one apparition to another. We used the TRAPPIST
telescopes to monitor the comets using broadband and narrowband filters. From the broadband images, we produced light curves and computed color indices for each passage, and we derived the activity slopes. We used a Haser model to compute the production rates of five gaseous species (CN, C2, C3, OH, and NH) and derived the proxy parameter Afrho for
dust activity. We also observed both comets in spectroscopy during their most recent apparition using the Himalayan Chandra
Telescope and compared the spectroscopic data to our results obtained through photometry. For both comets, our analysis of coma colors does not reveal any significant change from one passage to the other, indicating that the properties of the released
dust grains are similar. Our values of the color indices are consistent with the mean values for Jupiter-family comets. We measured a slight increase in the gas and
dust activities of comet 67P between 2015 and 2021, probably due to the small change in the comet's orbit that led the perihelion distance to decrease from 1.24 au for the first apparition to 1.21 au for the second one. Regarding 103P, we unambiguously measured a decrease (of at least 50%) in the gas and
dust activities between 2010 and 2023, showing a different behavior for this young, active comet. We find a typical chemical composition for both comets and detect no variation of the C2-to-CN production rate ratios and
dust-to-gas ratios from one passage to the other, indicating constant compositions, even if the level of activity has changed for 103P.
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All authors E. Hemmen, M. Vander Donckt, E. Jehin, S. Hmiddouch, K. Aravind, J. Manfroid, Z. Benkhaldoun, A. Jabiri, S. Ganesh
High Energy Astrophysical Phenomena
Theoretical Constraints on Neutron Star Superfluidity from Her X-1 Precession
Anton Biryukov, Amir Levinson and Pavel Abolmasov
Recent IXPE observations of Her X-1 reveal correlations between flux, polarization degree, and polarization angle with its 35-day superorbital cycle. These measurements have been interpreted as strong evidence that the 35-day period is driven by nearly free precession of the
neutron star. We show that this interpretation carries far-reaching implications for the dynamics of the crustal superfluid. In particular, maintaining precession over the $\sim 50$-year observational baseline of Her X-1 would require that superfluid
vortices remain unpinned for centuries and experience extremely weak mutual friction while traversing the heavy-ion
lattice of the inner crust – conditions that challenge conventional wisdom and standard models of glitch dynamics.
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Astrophysics of Galaxies
Compact, AGN-hosting Dwarf Galaxies with "Little Red Dots"-like SEDs in the Local Universe
Lulu Bao, Chao-Wei Tsai, Jingwen Wu et al. (+1 more)
Local active
galactic nuclei (AGNs) in
dwarf galaxies are often considered as analogs for the earliest supermassive black holes, although their connections require more comprehensive examinations. Motivated by finding the local analogs of "Little Red Dots" (LRDs), the compact, red
galaxies discovered by JWST at z > 5 characterized by "V-shaped" SEDs, we compile a sample of local AGN-hosting
dwarf galaxies (ADGs) with comparable luminosities to statistically evaluate this connection. By applying K-means clustering to SED shapes and morphological sizes, we classified four groups which trace a sequence in physical properties, including
metallicity,
star formation rate, and
dust emission, mainly driven by their distinct UV-optical slopes. Within these groups, we find that about half of the ADGs exhibit "V-shaped" SEDs and relatively compact morphologies. However, a direct comparison reveals fundamental physical differences: local "V-shaped", compact ADGs appear significantly more evolved than high-z LRDs, characterized by systematically larger effective radii and distinct ionization states. Our results suggest that local compact ADGs likely follow a different formation pathway from LRDs, highlighting the complexity of black hole-
galaxy co-
evolution across
cosmic time.
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All authors Lulu Bao, Chao-Wei Tsai, Jingwen Wu, Jialai Wang
Astrophysics of Galaxies
The MeerKAT Massive Distant Clusters Survey: a search for diffuse radio emission in 30 massive SZ-selected clusters at $z > 1$
Dakalo G. Phuravhathu, M. Hilton, S. P. Sikhosana et al. (+10 more)
We present the results of a search for diffuse
radio emission in a uniformly selected sample of 30 of the most massive Sunyaev-Zel'dovich selected
galaxy clusters at $z > 1$, providing the first statistical constraints on the
evolution of cluster-scale diffuse emission beyond this
redshift. We also analyse the scaling relations between
radio power ($P_{1.4\,\mathrm{GHz}}$) and cluster mass ($M_{\rm 500c}$) in this high-
redshift sample. It is well established that
radio halos are primarily found in the most massive clusters, where turbulent energy from major mergers can re-accelerate relativistic electrons and amplify
magnetic fields on megaparsec scales. Deep MeerKAT 1.28 GHz observations reveal diffuse
radio halos in eight clusters (27$\%$), while the remaining 21 (70$\%$) show no emission; one additional cluster (3$\%$) was excluded from the
radio analysis due to poor data quality. The
halo detection rate in this high-
redshift sample is lower than at intermediate
redshift, but remains higher than the $\lesssim 10\%$ occurrence generally predicted by theoretical models at $z \gtrsim 1$. The detected
radio halos scatter around the best-fitting $P_{1.4\,\mathrm{GHz}}$-$M_{\rm 500c}^{\rm {Unc}}$ relation derived for the MMDCS sample, whereas non-detections populate the lower envelope of the
radio power-mass plane, similar to trends seen at lower
redshift. No cluster-scale
radio relics or mini-
halos are identified. Our findings highlight MeerKAT's ability to probe non-thermal processes in the most distant clusters and the need for deeper, lower-frequency surveys to uncover faint diffuse emission and test the persistence of the $P_{1.4\,\mathrm{GHz}}$-$M_{\rm 500}$ relation across
cosmic time.
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All authors Dakalo G. Phuravhathu, M. Hilton, S. P. Sikhosana, D. Y. Klutse, K. Knowles, J. van Marrewijk, K. Moodley, T. Mroczkowski, N. Oozeer, B. Partridge, Y. C. Perrott, C. Sifón, U. Sureshkumar
Astrophysics of Galaxies
A spectroscopic map of the Galactic centre: Integrated light and dynamical modelling
A. Feldmeier-Krause, T. I. Maindl, G. van de Ven et al. (+3 more)
The centre of the Milky Way is occupied by a
nuclear star cluster that contains the supermassive black hole Sgr A*. The cluster is embedded in the larger surrounding
nuclear stellar disc. These three components dominate the mass budget of the
Galactic centre at different radial scales. The mass distribution of the
Galactic centre has been studied extensively using observations of individual bright
stars and various dynamical modelling approaches. The situation differs for external
galaxies, where observations are often limited to the integrated line-of-sight kinematics. For such systems, triaxial orbit-based dynamical modelling has become a standard method of deriving mass distributions and
stellar orbit distributions. We aim to apply and test this method on the
Galactic centre. We extracted
stellar line-of-sight kinematic maps of the inner ~3 pc x 66 pc region of the
Galactic centre. We used the DYNAMITE code, which calculates an orbit library in a given gravitational potential and computes model kinematic maps. These maps were then compared to the observed kinematic maps, and the gravitational potential and orbit distribution of the
Galactic centre were constrained. We recover the correct mass of Sgr A*, and our
stellar mass distributions are in agreement with the literature, albeit with larger uncertainties. The
stellar structures are at most mildly triaxial and close to oblate. The
stellar orbit distribution in the inner region is dominated by dynamically warm and hot orbits. At larger scales, dynamically cold – highly rotating – orbits have the largest weights. The dominance of hot and warm orbits is a consequence of short dynamical timescales in the inner
Galactic centre, causing dynamical heating. The presence of cold orbits at large radii may be explained by the longer heating timescales in this region, and by the
stars in the outer
nuclear stellar disc being younger.[abridged]
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All authors A. Feldmeier-Krause, T. I. Maindl, G. van de Ven, S. Thater, P. Jethwa, I. Breda
Astrophysics of Galaxies
Revealing the cold skeleton of the Magellanic Clouds and the Magellanic Bridge with ASKAP
James Dempsey, N. M. McClure-Griffiths, Antoine Marchal et al. (+14 more)
We present the GASKAP-HI pilot absorption survey of neutral hydrogen (HI) in the Magellanic system. This survey provides 3219 sightlines across the Large (LMC) and Small Magellanic Clouds (SMC) and the Magellanic Bridge (MB) towards 1.4-GHz continuum sources, representing a 15-fold increase on pre–GASKAP-HI sampling of the Magellanic System. We find 344 candidate detections of cold gas at Magellanic velocities (vLSRK >= 90 km s-1), with signal-to-noise ratio > 3 detection rates of 44% (LMC; 192 of 438), 73% (SMC; 85 of 117) and 4% (MB; 35 of 793). We examine the candidate detections within the MB, Gaussian decompose these and examine the cold gas across the MB. Here we find that the majority of cold gas detections are found closer to the SMC. We also find potential evidence of the recent formation of cold gas on the outskirts of a shell within the MB. We find a mean cold gas fraction of fCNM = 0.12 +- 0.08 for the MB, which is very similar to the SMC and lower than the LMC value of 0.14. Overall, we reveal cold gas distributed extensively across the Magellanic system, including within the MB, and surmise that the cold gas in the MB is either pulled from the SMC as part of the formation of the MB, or formed in the
turbulence of those same interactions.
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All authors James Dempsey, N. M. McClure-Griffiths, Antoine Marchal, S. E. Clark, John M. Dickey, Min-Young Lee, Claire Murray, Hiep Nguyen, Nickolas M. Pingel, Snežana Stanimirović, Jacco Th. van Loon, Helga Dénes, Steven J. Gibson, Katie Jameson, Ian Kemp, Callum Lynn, Yik Ki Ma
High Energy Astrophysical Phenomena
Dynamics and Radiative Signatures of Accretion Flows onto a Kerr-like Wormhole
Jing-ze Xia, Hong-xuan Jiang, Cheng Liu et al. (+1 more)
Wormholes are a hypothetical object that connects disparate points in spacetime. It is a theoretically well-motivated black hole alternative and offers a potential observationally testable arena for probing strong-field
gravity with horizon-scale images. We perform general relativistic magnetohydrodynamic (GRMHD) simulations and general relativistic radiative transfer (GRRT) calculations of
accretion flows onto a Kerr-like wormhole. Adopting a Kerr black-bounce metric with a fixed throat parameter $\ell = 2.5\,\rm M$, we explore the effects of
spin using both two- and three-dimensional simulations. The
accretion flow is initialized as a magnetized geometrically thick
torus near one mouth of the wormhole, while the opposite mouth is initially gas-free. We find that the
spin parameter influences the dynamical properties on both sides of the wormhole through the frame-dragging effects. Based on the GRMHD results, we compute ray-traced images at $230\,\mathrm{GHz}$ using RAPTOR, and analyze the horizon-scale image structure through higher-order
photon trajectories. Our GRRT calculations show that emissions originating from the immediate vicinity of the throat can dominate, in contrast to the case of a Kerr black hole. It provides the variable component of the signal and imprints a clear quasi-periodic modulation in the light curves. These properties would be useful to either confirm or rule out such exotic compact objects through horizon-scale observations.
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All authors Jing-ze Xia, Hong-xuan Jiang, Cheng Liu, Yosuke Mizuno
High Energy Astrophysical Phenomena
Spectro-Polarimetric Observations of TeV Sources (SPOTS): First results
J. Barnard, B. van Soelen, I.P. van der Westhuizen et al. (+5 more)
Blazars are jetted active
galactic nuclei, with the jet aligned along the observer's line of sight. Their spectral energy distributions are dominated by non-thermal emission, with an underlying thermal component at optical/ultraviolet wavelengths. However, the underlying jet
magnetic field structure and particle acceleration mechanisms requirements for the non-thermal emission are still under debate. Polarization measurements can provide critical insights, and we investigate the optical polarization properties of TeV-emitting blazars using long-term optical monitoring. We present results from the first 21-months of the Spectro-Polarimetric Observations of TeV Sources (SPOTS) campaign, using the Southern African Large
Telescope, of 14 blazars. Overall, observations of the sample during this campaign showed a low average optical polarization ($\Pi\lesssim10\%$). While some sources exhibited smooth polarization angle rotations on timescales of days to weeks, others showed
stochastic variations consistent with turbulent
magnetic fields. The average ordering of the
magnetic field was low ($F_B\lesssim0.10$), consistent with emission arising in extended, turbulent regions of the jet. For individual sources, correlations between polarization and its frequency dependence were found, but were not found across the entire sample. The nature of the frequency dependence varied between observations, indicating that simple one-zone models are insufficient and that $F_B$ must be wavelength dependent. This study highlights the complex nature of blazar jets and underscores the importance of long-term, multi-wavelength polarimetric monitoring. This comprehensive
dataset enables detailed modelling of individual sources, and provides valuable context for future X-ray polarimetry observations.
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All authors J. Barnard, B. van Soelen, I.P. van der Westhuizen, M. Böttcher, A. Martin-Carrillo, H.M. Schutte, S. van der Merwe, M. Zacharias
Solar and Stellar Astrophysics
Spectroscopic Disentangling Revealed the Tertiary Component in the Multiple System EM Boo
Ö. H. Y{\i}ld{\i}z, H. Bak{\i}ş and B. Özkardeş
We present a comprehensive photometric and spectroscopic study of the triple
stellar system EM\,Boo. The system is composed of detached, low-mass components, and for the first time in the literature, the spectrum of the tertiary component has been successfully disentangled from the composite spectrum using the KOREL code. Synthetic spectra were generated for each disentangled component, allowing determination of their atmospheric parameters. The depth of the H$_\alpha$ line in the tertiary spectrum indicates that it is an intermediate-temperature
star, consistent with spectral types between A and F, and its effective temperature was determined to be 7000~K. By analyzing the radial velocity and light curves simultaneously, the fundamental physical parameters of the system were derived, and its detailed evolutionary status was investigated using MESA models. The HIPPARCOS trigonometric parallax ($\varpi_{\rm Hip}=1.33\pm1.45$ mas) and
Gaia DR3 trigonometric parallax ($\varpi_{\rm Gaia}=3.9699\pm0.1812$ mas) show a significant discrepancy, most likely related to the system's multiplicity and the limitations of single-
star astrometric solutions. To provide independent distance estimates, we modeled the spectral energy distribution (SED) using multi-wavelength flux data, yielding $E(B-V)=0.05$ mag and a trigonometric parallax $\varpi_{\rm SED}=3.2$ mas, corresponding to $d_{\rm SED}=313$ pc. Furthermore, photometric distance estimates based on the components' absolute magnitudes yield $d_{1}=299$ pc and $d_{2}=301$ pc, in good agreement with the SED-based distance. Both the SED-based and photometric distances converge around $d=300$ pc, indicating that the
Gaia trigonometric parallax underestimates the true distance of EM\,Boo.
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Earth and Planetary Astrophysics
Mitigating stellar radial velocity jitter using orthogonal activity indices and a time-aware neural network
Jordi Blanco-Pozo, Manuel Perger, Guillem Anglada-Escudé et al. (+7 more)
Despite recent advances in the precision of high-resolution spectrographs, the detection of Earth-like
exoplanets is still limited by the effects of
stellar activity, which introduce radial velocity variations at the metre-per-second level or larger. We present a framework to disentangle
stellar effects from planetary signals by exploiting high-order distortions of the cross-correlation function (CCF; a measure of the average spectral line profile), thus moving beyond the commonly applied Gaussian fit approximation. We decomposed the CCF using a Gram-Schmidt orthogonal basis function, enabling the separation of pure line shifts from line-shape distortions. To model activity-induced contributions to the radial velocities, we have developed a time-aware convolutional
attention network dubbed CANSTAR. This network was trained on synthetic line-shape distortion coefficients produced with the realistic
stellar simulator StarSim to learn the temporal
evolution of
stellar activity features. We validated our framework using HARPS and CARMENES observations of two active
stars, ${\epsilon}$ Eridani and TZ Arietis. The network effectively mitigates
stellar activity, reducing the radial velocity RMS to 52.5 % and 62.4 % of the uncorrected variability, respectively. This correction enables a more precise determination of the orbital parameters of TZ Arietis b compared to a Gaussian process regression. Our results demonstrate that neural networks that incorporate the temporal context can outperform state-of-the-art methods in complex activity regimes. Future improvements on StarSim that will allow us to train CANSTAR on 3D magnetohydrodynamic spectra and more complex instrumental modelling are expected to bridge the performance gap between synthetic and real data, offering a robust pathway towards detecting Earth-mass
planets around Sun-like
stars.
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All authors Jordi Blanco-Pozo, Manuel Perger, Guillem Anglada-Escudé, Ignasi Ribas, David Baroch, Marina Lafarga, Juan Carlos Morales, Òscar Porqueras-León, Sophie Stucki, David Vallmanya Poch
Solar and Stellar Astrophysics
The magnetic fields in Be stars are stronger than previously suggested
S. Hubrig, S. P. Järvinen, M. Schöller et al. (+1 more)
Recent observational studies suggest that Be
stars most likely are formed through the process of mass transfer in binary systems. In view of the wide consensus that the origin of the
magnetic field in
stars with radiative envelopes involves binary interaction processes, searching for
magnetic fields in Be
stars appears especially promising. As a pilot project, we searched for the presence of
magnetic fields in a sample of seven well-known Be
stars. We used high-resolution HARPSpol spectra to measure the mean longitudinal
magnetic field, employing the least squares deconvolution technique. A dedicated measurement procedure introduced by our group in recent years was applied. Opposite to previous spectropolarimetric studies reporting that
magnetic fields in Be
stars are weak and usually below 100 G, our study presents the first observational evidence that
magnetic fields in Be
stars can be as strong as a few hundred gauss.
Magnetic fields are detected in all studied Be
stars, with the strongest
magnetic field being about -460 G for the B0.5 III
star HD 184915.
Magnetic fields in the range between 338 and 380 G (in absolute values) are detected in three other Be
stars, HD 209409, HD 209522, and HD 224686. Due to the fact that
magnetic fields in Be
stars are stronger than previously believed, we must re-evaluate our understanding of the initial conditions of massive binaries to be able to determine the origin of such systems.
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All authors S. Hubrig, S. P. Järvinen, M. Schöller, I. Ilyin
High Energy Astrophysical Phenomena
HD3191, the high-mass X-ray binary that wasn't there
Gregor Rauw, Yaël Nazé and Piotr Antoni Kołaczek-Szymański
The rapidly rotating B1 IV:nn
star HD3191 lies within the error box of a flaring
Fermi gamma-ray source. Although the counterpart of the
Fermi source is likely an active
galaxy, HD3191 has nevertheless been suggested to be a high-mass X-ray binary, possibly hosting a black hole companion. The
star displays roughly sinusoidal photometric variations with amplitudes of about 12 mmag for two frequencies $\nu_1$ = 0.1235 d$^{-1}$ and $\nu_2$ = 1.6038 d$^{-1}$. Half of the former frequency ($\nu_1$/2) had previously been interpreted as the orbital frequency of a high-mass X-ray binary in which the B1 IV:nn primary undergoes ellipsoidal variations. We show that this scenario fails to account for the lack of significant radial velocity variations and for the overall properties of the
star. Our spectroscopic observations instead unveil line profile variations, suggesting that the photometric and line profile variations arise from multi-mode pulsations rather than from orbital effects. Whilst we cannot rule out the possibility that HD3191 could be a nascent binary, consisting of a B1 IV:nn with a low-mass pre-main sequence companion, the most likely scenario is a single
star displaying non-radial pulsations. The fast
stellar rotation would thus be intrinsic to the B1 IV:nn
star rather than being the result of a
spin-up during a past mass-transfer episode.
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