High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Observable strong field effects of extra spacetime dimension in the braneworld black hole
K. K. Nandi, R. N. Izmailov, R. Kh. Karimov et al. (+1 more)
Inspired by the string theory, the braneworld picture introduces extra dimensions beyond the four that may have observable non-trivial effects in short distance (strong field)
gravity experiments. A case in point is the Randall-Sundrum braneworld picture that projects the $5d$ bulk Weyl tensor onto the $3d$ brane providing a stress tensor in the effective Einstein field equations on the brane. Dadhich, Maartens, Papadopoulos and Rezania (DMPR) derived an exact braneworld black hole solution of the brane
vacuum field equations. The solution formally resembles that of Reissner-Nordström but is physically different from it since the "
tidal charge" $\Upsilon$ in the solution is not the electric charge but an imprint from the fifth dimension allowing both signs in the power law modification $\pm \frac{\Upsilon ^{2}}{r^{2}}$ to the Schwarzschild metric $\left( \Upsilon = 0\right)$. The corresponding black holes are designated as DMPR$\pm$. We study here the effect of $\Upsilon$ on strong field
lensing observables and compare in the eikonal limit the ring down quasinormal mode (QNM) frequencies of DMPR$-$ with those of DMPR$+$, the two variants of
tidal charge modified Schwarzschild black hole ($\Upsilon = 0$). It turns out that the
tidal charge can significantly modify the Schwarzschild
lensing observables and QNM frequencies. In particular, we find that the Pretorius-Khurana critical exponent $\gamma$ of circular null orbits in the DMPR$-$ black hole has a lower value than that for the Schwarzschild black hole, which indicates a stronger Lyapunov instability suggesting that the
accretion disks of DMPR$-$ black holes would appear brighter. The case of the SgrA* black hole is considered for a possible constraint on $\Upsilon$ from the EHT observation of its shadow size.
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All authors K. K. Nandi, R. N. Izmailov, R. Kh. Karimov, A. A. Potapov
Solar and Stellar Astrophysics
Can Asteroseismic Structure Inversions Be Performed in Structure-Dependent Coordinates?
J. M. Joel Ong, Sarbani Basu, Willem Hoogendam et al. (+1 more)
Yes. Unlike other applications of observational asteroseismology, "structure inversions" constrain the physical properties of
stellar interiors in a model-independent fashion. However, existing techniques – which parameterise these quantities as functions of the physical radial or mass coordinate – break down when applied to
stars which differ substantially from the Sun. These difficulties may be overcome by operating in coordinate systems that have long been known to more naturally suit the physical characteristics of the measured normal modes. We derive expressions for transforming inversion kernels in the acoustic and buoyancy radial coordinates, rather than in the physical radius, and make available a numerically performant implementation. These modified inversions directly address several specific known shortcomings of existing inversion procedures. Using the buoyancy radius in
gravity-mode and mixed-mode pulsators permits meaningful comparisons of
stars and models with differently-sized convective and radiative zones, which defeat standard inversions. Even in pressure-mode oscillators, inversions in the acoustic radial coordinate eliminate the methodological requirement for the mass and radius of the true
star being needed to be known in advance.
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All authors J. M. Joel Ong, Sarbani Basu, Willem Hoogendam, Vincent Vanlaer
Instrumentation and Methods for Astrophysics
Analysis of Laser-Satellite Deconfliction for Astronomical Observatories
Christoph Baranec, Reed Riddle, Yuhei Takagi et al. (+1 more)
We present an analysis of
laser-satellite deconfliction across three astronomical
laser observatories for right ascension and declination targets and fixed azimuth and elevation ranges. This study uses new visualization tools to evaluate how different science exposure durations impact the total percentage of available open-time during observing nights. We further assess the operational efficiency of
laser keep-out-cone half-angles from the default 2.5 degrees down to the 0.1-degree minimum. We also directly compare the open-time differences of right ascension and declination targets vs. fixed azimuth and elevation ranges. Finally, we analyze historical trends to quantify the growing effect of satellite mega-constellations and the efficacy of specific waiver protocols on ground-based
laser astronomy.
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All authors Christoph Baranec, Reed Riddle, Yuhei Takagi, Jim Lyke
Astrophysics of Galaxies
The new era of Lyman alpha emitters (LAEs): Efficiency in the selection criteria
P. Layana-Astudillo, I. Laferte-Urrutia, L. Guaita et al. (+6 more)
The ODIN survey has detected thousands of Lyman-alpha emitting
galaxies across seven sky fields, covering nearly one hundred square degrees. One of these regions is the SHELA field, observed with DECam on the Blanco
Telescope, reaching depths of approximately 25.3 AB mag in the N501 and N419 narrowbands and approximately 26.3 AB mag in the g and r broadbands over fifteen square degrees. In this work, we analyze the efficiency of the dual-continuum selection criterion as a function of broadband depth. Applied to the N501/N419 observations, we find that when the broadband data are roughly one magnitude deeper than the narrowband, nearly 80% of the LAEs are recovered, compared to only approximately 20% when both reach the same depth. This result shows that, for a fixed observing budget, the optimal strategy is to obtain broadband images approximately one magnitude deeper than the narrowband, since deeper exposures yield progressively smaller gains in the recovery fraction.
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All authors P. Layana-Astudillo, I. Laferte-Urrutia, L. Guaita, C. Artale, J. Magaña, E. Gawiser, P. Troncoso-Iribarren, K. Lee, N. Firestone
High Energy Astrophysical Phenomena
Supernovae with the Square Kilometre Array
Poonam Chandra, Yuhei Iwata, A. J. Nayana et al. (+2 more)
This chapter presents the science potential of the Square Kilometre Array (SKA) for studying all classes of
supernovae and their environments. It substantially updates and extends the earlier work of Perez-Torres et al. (2015), originally published in the 2015 Advancing Astrophysics with the SKA (AASKA14) volume, reflecting the dramatic progress in time-domain astronomy and
radio instrumentation over the past decade. We outline how SKA1 and its pathfinders will transform the
radio study of core-collapse
supernovae (CCSNe) through sensitive, commensal wide-field surveys capable of discovering hundreds of events per year, providing a
dust-unbiased census of massive-
star deaths and direct measurements of the volumetric CCSN rate. The same data will probe ejecta-circumstellar medium (CSM) interaction, shock microphysics, and progenitor mass-loss histories. Deep, triggered observations of thermonuclear
supernovae (SNe Ia) will allow the SKA to test competing progenitor scenarios by detecting – or definitively excluding – the
prompt radio emission expected from single-degenerate systems. The chapter further explores superluminous
supernovae (SLSNe), delayed interaction
supernovae and synergies with facilities such as ALMA, ngVLA, CTA, IceCube-Gen2, and ULTRASAT. Collectively, these studies will turn
radio supernova astrophysics from a discovery-limited field into one governed by population statistics.
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All authors Poonam Chandra, Yuhei Iwata, A. J. Nayana, Miguel Pérez-Torres, Kovi Rose
Solar and Stellar Astrophysics
Standing oscillations in a resonant sunspot atmosphere captured by integral field spectroscopy
Glen Chambers, David B. Jess, Shahin Jafarzadeh et al. (+8 more)
The
solar atmosphere is replete with magnetohydrodynamic wave activity, with
magnetic structures such as sunspots channelling wave energy flux efficiently into the outer atmosphere. Steep density and temperature gradients between the photosphere and chromosphere provide ideal conditions for magnetoacoustic resonance cavities, amplifying $\sim 5$ mHz oscillatory power in sunspot atmospheres. However, diagnosis of such cavities has largely been limited to lines such as Ca II H/K and He I 10830 Å, with no evidence yet from layers probed by the Na I D$_1$/D$_2$ doublet. Here we use the newly commissioned integral field unit FRANCIS to examine oscillations spanning the formation heights of the Na I D$_1$/D$_2$ lines and determine whether propagating and/or standing modes are present within a sunspot umbra. The RH1.5D code estimated formation heights for three windows: the Na I D$_1$ wing (core $-300$ mÅ; $\approx 355$ km), the Na I D$_1$ core ($\approx 750$ km), and the Na I D$_2$ core ($\approx 850$ km). Wavelet cross-correlation of line-core and bisector Doppler velocities yielded phase spectra versus height, classifying the dominant $\sim 5.5$ mHz oscillations as propagating or standing-like. At the umbra-penumbra boundary we find propagating modes with energy fluxes of $\sim 1.3 \times 10^{4}$ W m$^{-2}$ in the upper photosphere, falling to $\sim 3.1 \times 10^{3}$ W m$^{-2}$ in the lower chromosphere, implying a damping length $L_d \approx 363$ km, comparable to the local density scale height. In contrast, near-zero phase differences dominate regions of enhanced chromospheric power at the umbral centre, evidencing standing-wave behaviour and resonance-cavity dynamics. These results demonstrate the suitability of
solar integral field units for mapping sunspot wave properties, with the Na I D$_1$/D$_2$ lines offering a novel diagnostic of resonance cavities and energy flux.
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All authors Glen Chambers, David B. Jess, Shahin Jafarzadeh, Michele Berretti, Samuel D. T. Grant, Marco Stangalini, H. N. Smitha, Damian J. Christian, Luís E. A. Vieira, Alisson Dal Lago, Fernando L. Guarnieri
Astrophysics of Galaxies
Fast Radio Bursts probe Galaxy Evolution: Evidence and implications of a redshift-dependent FRB host DM
Lluis Mas-Ribas
The
redshift evolution of ionized gas in the full
galaxy-
halo system is a central open question in
galaxy formation, because no existing observable is simultaneously sensitive to all ionized phases. Here we explore fast
radio bursts (FRBs) as a probe of the density
evolution of this gas through the
redshift dependence of the FRB host dispersion measure, ${\rm DM_{host}}(z) \propto (1+z)^{n_z}$. The host DM denotes the electron column density of all ionized gas in the host along the FRB sightline, providing a unified tracer that complements existing phase-specific diagnostics. We apply a forward-modeling framework that accounts for instrumental effects to 90 localized FRBs (69 with confirmed host
redshifts) from the DSA and ASKAP/CRAFT ICS surveys. Our inference yields $n_z = 1.62^{+1.48}_{-1.57}$, ruling out the non-evolving scenario ($n_z = 0$) at $1\,\sigma$, with both
datasets independently favoring $n_z > 0$. The main $n_z$ degeneracy is with the mean host DM and parameters such as $H_0$, highlighting the need to account for a host
evolution in inference analyses and DM-based host
redshift estimates; overestimating
redshifts by up to $\Delta z \approx 0.3$ for DM$_{\rm EG} \sim 1000 - 2000\,{\rm pc\,cm^{-3}}$ otherwise. About 100 ($300-350$) localized hosts from MeerTRAP in coherent mode (DSA/CRAFT) will yield $n_z$ uncertainties of $\sim0.7$. Precise $n_z$ measurements compared with the
evolution of individual phases and
galaxy scaling relations will shed light on ionized gas
evolution in
galaxies and
halos, informing the dominant phase, the driver of the overall
evolution, and FRB progenitor channels.
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Cosmology and Nongalactic Astrophysics
A new $H_0$ measurement with SNe Requiem and Encore using $\texttt{Gravity.jl}$
L. Bazzanini, G. Di Rosa, A. Acebron et al. (+24 more)
We present a strong-
lensing (SL) analysis of the
galaxy cluster MACS J0138.0-2155 (z=0.336), the first known lens cluster discovered to host two distinct multiply imaged Type Ia
supernovae (SNe): SN Requiem and SN Encore. Both SNe are located in the massive, multiply imaged red
galaxy MRG-M0138 at z=1.949. The projected total mass of this cluster has been investigated with several independent lens models (Suyu+26; Pierel+26), using a sample of 23 spectroscopically confirmed multiple images from 8 background sources (0.767<z<3.420), identified from HST and JWST imaging data, and VLT/MUSE spectroscopy. In this work, we develop a new SL model based on a novel
Bayesian parametric lens-modelling framework $\texttt{Gravity jl}$, exploiting the same SL
dataset. Our reference mass model accurately reproduces the observed image positions, with an image-plane rms image position residual of 0.15”. Assuming H0 = 70 km/s/Mpc, we predict the future reappearances of highly delayed SNe counter-images, finding $D_t(1d,1a) = 3122_{-70}^{+75}$ d (April-August 2032) for SN Encore and $D_t(2d,2a) = 3902_{-67}^{+72}$ d (January-May 2027) for SN Requiem. By allowing H0 to vary, and using the measured time delays of SN Encore and Requiem together with their statistical uncertainties as observables, we infer the value of H0 jointly with the other lens-model free parameters, by combining the values inferred from 3 mass models. We obtain a new measurement of $H_0 = 69.2_{-8.0}^{+9.6}$ km/s/Mpc, consistent with the value inferred from independent lens models. This error is currently dominated by the large relative uncertainty on the measured time delays (>10%). The forthcoming reappearance of SN Requiem offers an immediate opportunity to significantly improve constraints on H0, provided that lens-model systematics are controlled. These results establish M0138 as a premier anchor for high-precision cluster TDC.
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All authors L. Bazzanini, G. Di Rosa, A. Acebron, P. Bergamini, M. Lombardi, P. Rosati, G. Angora, G. B. Caminha, S. Ertl, G. Granata, A. M. Koekemoer, S. H. Suyu, J. Pierel, A. B. Newman, C. Grillo, S. Schuldt, M. Bulla, S. Cha, M. D'Addona, J. M. Diego, M. Fogliardi, B. L. Frye, M. J. Jee, P. S. Kamieneski, M. Meneghetti, A. Mercurio, E. Vanzella
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
A Solar-System Window for Hidden Stellar Companions
Karim Benakli
Could the closest
stellar or substellar object to the Sun be not an ordinary
star at parsec distance, but a hidden-brane companion at hundreds or thousands of astronomical units? We do not perform a new
Solar-System dynamics analysis; instead we construct a phenomenological mass-distance map using an illustrative ephemeris
tidal envelope calibrated to
Planet-Nine-like constraints. A smooth dark matter
halo cannot supply such an object: the local density contains only a sub-Pluto mass within 1000 AU. A nearby hidden-brane companion must therefore be a structured, gravitationally bound object rather than a typical
halo draw. The illustrative envelope still allows Earth to sub-Saturn masses at 300-1000 AU, rising to Jovian mass near 2000 AU. In a simple QCD-scaled hidden sector with a confinement scale about ten times larger than ordinary QCD, the minimum hidden
stellar mass overlaps the upper part of this window, providing a
benchmark for a genuine hidden-sector
star: bright in dark
photons, electromagnetically dark to us, and visible only through
gravity. We also derive an Earth-based source-strength proxy for brane-to-brane channels and show that, along the ephemeris envelope, it grows as the square of the companion distance: the largest received source scale comes from the most massive companion still allowed, not the nearest one. A probe sent to the companion's gravitational projection would reduce the ordinary source-receiver separation by two to three orders of magnitude relative to Earth-based operation. This is not a detection forecast; the excitation of KK modes, the compact-direction brane-to-brane transfer factor, and the detector response remain model-dependent.
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High Energy Astrophysical Phenomena
Causality alone bounds the maximum radius difference between different-mass neutron stars
Aleksi Kurkela and Tuhin Malik
We investigate how the assumption of a common causal equation of state (EoS) correlates the radii of
neutron stars at different masses and thereby reduces the uncertainties inferred from independent observations. We show that causality, anchored only to the
chiral effective field theory ($\chi$EFT) EoS near saturation density, places a closed-form upper bound on the radius difference, $R(2.0\,M_\odot)\le 1.16\,R(1.4\,M_\odot)-1.1\,$km. The bound is saturated exactly by a one-parameter family of EoSs that we construct analytically. Imposing this prior-independent causal ceiling on the independent NICER posteriors of PSR J0437-4715, PSR J0614-3329, and PSR J0740+6620 retains only 7.5% of their joint product distribution and removes the large-radius tail of the PSR J0740+6620 posterior. Unlike full EoS-informed inferences, our construction cleanly isolates the consequences of the generic physical assumptions of a common causal EoS from those associated with a particular choice of EoS prior, providing a transparent
benchmark for interpreting
neutron-
star observations.
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Cosmology and Nongalactic Astrophysics
A cross-epoch endpoint-consistency test of a single effective scaling from dark energy to inflation
Martin Drobczyk
A cross-epoch endpoint-consistency test is formulated for a single power-law effective scaling, $M_U(\mu)=\beta^{1/4}\,M_P(\mu/M_P)^\gamma$, connecting late-time
cosmic acceleration to the inflationary energy scale. The normalization is anchored at $\mu=H_0$ by the late-time dark energy closure relations of the density-responsive
gravity (DRG) framework and extrapolated to the inflationary Hubble rate $\mu=H_*$. Comparison with the CMB-normalized Starobinsky plateau defines the residual matching factor $C_{\rm infl}\equiv V_0^{A_s}/V_0^{\rm RG}$. The novelty is the formulation of the inflation - dark-energy connection as a quantitative endpoint test between two empirically anchored energy scales. The lever arm $H_*/H_0\sim 10^{55}$ compresses endpoint uncertainties into $\delta\gamma\propto [p\ln(H_*/H_0)]^{-1}\delta\ln X$, so requiring $C_{\rm infl}=\mathcal{O}(1)$ selects a narrow consistency band. For the
benchmark $V_0\propto M_U^4$ with $c_4=\mathcal{O}(1)$, matching requires $\gamma\simeq 0.491$ and $\beta\simeq 0.68$, both $\mathcal{O}(1)$. Varying $p\in[2,8]$ shifts $\gamma$ only mildly (approximately $0.45$–$0.52$), with natural matching favoring $p\simeq 3$–$4$. We present the full uncertainty budget, including cumulative threshold effects ($\Xi$) and observational errors on the late-time anchor ($w_0$, $A_s$, $H_*$). A secondary consequence is that the effective
vacuum sector dilutes as $\rho_\Phi\propto a^{-6\gamma}$ at late times, faster than spatial
curvature for $\gamma>1/3$. In a closed universe, this permits a cosmological turnaround at $|\Omega_K|\sim\mathcal{O}(10^{-4})$, testable with Stage-IV surveys and qualitatively distinct from $\Lambda$CDM.
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High Energy Astrophysical Phenomena
Symbiotic Magnetogenesis during Radiation Domination
Stephon Alexander, Ariel Marxena Baksh, Lawrence Edmond IV et al. (+1 more)
We present a late-time magnetogenesis mechanism in which a coupled
axion-dilaton system sources a dark $U(1)$ gauge field. The dilaton's exponential coupling drives tachyonic amplification by reshaping the instability band, while the
axion controls the helicity structure of the field. Together, they amplify both gauge helicities and produce a moderately
chiral dark
magnetic field without fine-tuning in either scalar sector. The field is generated in the dark sector, thus the mechanism avoids
plasma-conductivity suppression in the visible sector, while the model remains robust across a broad range of scalar-masses and couplings. Numerical
evolution from $z=10^5$ to matter-radiation equality, combined with a parameter search over the
axion mass, dilaton initial conditions, and dilaton coupling, shows that astrophysically relevant amplification persists across fuzzy-dark-matter and ultralight-
axion regimes. A
benchmark case yields $B\approx0.9 ~\mathrm{nG}$ on $\lambda_0\sim1 \mathrm{Mpc}$, with kinetic mixing transferring the field to the visible sector over a broad range of mixing parameters.
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All authors Stephon Alexander, Ariel Marxena Baksh, Lawrence Edmond IV, Wenrong Sun
Astrophysics of Galaxies
Dust destruction signals shock-accelerated outflows in the nearby active galaxy NGC 1068
Luke R. Holden, Clive N. Tadhunter, Daniel J.B. Smith et al. (+3 more)
Massive gas
outflows driven by active
galactic nuclei (AGN) are a key ingredient in models of
galaxy evolution, in which they are required to regulate
star formation and thus explain the observed properties of the
galaxy population. However, it remains uncertain how such
outflows are accelerated. Here, we use deep spectroscopic observations of the nearby active
galaxy NGC 1068 to directly address this issue. Based on the flux ratios of high-ionisation [NeV]$\lambda$3425 and [FeVII]$\lambda$6087 coronal forbidden lines, we show that the non-outflowing gas in the disk of the
galaxy is characterised by high levels of depletion of refractory elements onto
dust grains, but the outflowing gas just above the disk is largely
dust-free. Consistent results are also found for the ratios of lower-ionisation forbidden lines of refractory and non-refractory elements. Moreover, a range of diagnostic ratios demonstrate that the density of outflowing gas is a factor 19-110 times higher than that of the non-outflowing gas. Together, these results imply that the
outflows in NGC 1068 are accelerated by fast shocks that both compress the gas and destroy much of the
dust. Consistent with the idea that AGN-driven shocks play an important role in heating and accelerating the near-
nuclear gas in
galaxies, this study demonstrates that coronal emission lines are a key diagnostic of the destructive impact of AGN activity.
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All authors Luke R. Holden, Clive N. Tadhunter, Daniel J.B. Smith, Martin A. Bourne, Marina I. Arnaudova, Isaac M. Mutie
Astrophysics of Galaxies
Radio emission from ultra-diffuse galaxies residing in galaxy clusters
Dharam V. Lal and Jeyasiona Murugesh
Ultra-diffuse
galaxies (UDGs), defined by their extremely low surface brightness ($g$-band $\mu \gtrsim 24$ mag arcsec$^{-2}$) and large effective radii (3–10 arcsec), remain one of the most puzzling
galaxy populations in the nearby Universe \citep{vanDokkum2015}. Predominantly found in dense environments, UDGs in the Coma cluster show a preferential
alignment of their major axes toward the cluster centre, suggesting strong environmental influence on their formation and
evolution. Using high-sensitivity, low-frequency
radio data from the upgraded
Giant Metrewave
Radio Telescope (GMRT), a pathfinder instrument we examined all 854 UDGs cataloged in Coma cluster \citep{Yagi2016}. Despite the unprecedented depth of these observations, no individual detections were made. A median stacking analysis in the upgraded GMRT band-3 achieved a 5 $\times$ rms upper limit $\simeq$1.5~$\mu$Jy, providing the most stringent constraint yet on the average (mean)
radio emission from UDGs, corresponding to
star-formation rates $\lesssim$10$^{-3}$~M$_\odot$~yr$^{-1}$ for Coma-cluster-like systems and $\lesssim$10$^{-1}$~M$_\odot$~yr$^{-1}$ at $z \sim 0.05$. Looking ahead, the Square Kilometre Array (SKA) will transform the study of such faint
galaxies. While the early AA$^\star$ configuration will deliver sensitivities comparable to the upgraded GMRT, the AA4 design baseline will achieve sub-$\mu$Jy rms levels at matched frequencies ($\nu \sim 200$~MHz–1.4~GHz), enabling detections of UDGs with
star formation rates as low as 10$^{-4}$–10$^{-3}$~M$_\odot$~yr$^{-1}$ within Virgo and Coma distances. Such capabilities will allow robust discrimination between quenched, dark-matter-dominated systems and those sustaining weak residual
star formation or low-luminosity
nuclear activity.
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Astrophysics of Galaxies
Early phases of star formation with SKAO: synchrotron emission from dense starless cores in molecular clouds
Andrea Bracco, Tyler L. Bourke, Stefano Bovino et al. (+8 more)
Magnetic fields play a central role in the
star-formation process, from diffuse gas to the dense, starless, molecular cloud cores that represent the first gravitationally bound structures on the path to
star formation. Yet, the
evolution of
magnetic fields during this critical phase remains poorly understood. Recent studies suggest that
cosmic-ray electrons interacting with
magnetic fields in prestellar cores can produce detectable synchrotron emission at low
radio frequencies, offering a novel probe of their magnetization in tandem with existing observational techniques. However, current instruments lack the angular resolution and sensitivity to exploit this signature. The Square Kilometre Array Observatory (SKAO) will provide the required capabilities enabling detections in nearby
star-forming regions within a reasonable number of observation hours in AA* and AA4. Thanks to its large field of view, observations of low- to high-mass
star-forming regions within the first kiloparsec from the Sun will enable both targeted studies of individual objects and statistical analyses over several hundreds of prestellar cores per pointing, marking a breakthrough in our understanding of their
magnetic field properties. This chapter outlines the scientific context, observational challenges, and prospects for probing
magnetic fields in prestellar cores with SKAO, and highlights synergies with complementary facilities such as ALMA, as well as cross-disciplinary collaborations within the SKAO community.
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All authors Andrea Bracco, Tyler L. Bourke, Stefano Bovino, Clive Dickinson, Daniele Galli, Michael Kuffmeier, Marco Padovani, Stefania Pezzuto, Thushara G.S. Pillai, Giovanni Sabatini, Alessio Traficante
Solar and Stellar Astrophysics
Ba Isotope Ratio in CEMP-s and CEMP-rs Stars as a Signature of s-Process and i-Process
Tatyana Sitnova and Lyudmila Mashonkina
We present a spectroscopic analysis of three carbon-enhanced metal-poor (CEMP)
stars of type CEMP-s and CEMP-rs and determine their non-local thermodynamic
equilibrium (NLTE) abundances of Ba and the fractions of the odd Ba isotopes (F$_{\rm odd}$). We found F$_{\rm odd}$ = 0.65$_{-0.34}^{+0.35}$ in SDSS J1349-0229, which is known in the literature as a CEMP-rs
star, while the other two
stars, BPS CS 29512-073 and SDSS J1036+1212, exhibit lower F$_{\rm odd}$ = 0.23$_{-0.10}^{+0.19}$ and 0.23$_{-0.11}^{+0.22}$, respectively, and they are known in the literature as CEMP-s
stars. The present result supports our earlier finding about distinct F$_{\rm odd}$ in CEMP-s and CEMP-rs
stars. For obtaining observational constraints on i-process nucleosynthesis, further NLTE abundance determinations for many chemical elements are required. We provide a tool for generating the lists of Ba II lines for a given F$_{\rm odd}$ and it is available on GitHub https://github.com/sitamih/ba_linelist.
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High Energy Astrophysical Phenomena
Unique Science Opportunities for Space VLBI Systems with the SKA Telescopes
Y. Y. Kovalev, G. Bruni, T. An et al. (+17 more)
To date, two dedicated Space Very Long Baseline Interferometry (SVLBI) missions, the VLBI Space Observatory Programme (VSOP) and RadioAstron, have provided groundbreaking insights into the Universe at angular resolutions as fine as ~10 microarcseconds. The phased SKA-Mid, with its exceptional sensitivity and broad frequency coverage, will form a unique ground-based anchor for future SVLBI missions, driving major advances into previously unexplored regions of the angular resolution-sensitivity parameter space. The discovery of extreme brightness temperatures in blazars by RadioAstron demands detailed investigation with next-generation SVLBI. Such studies are crucial for understanding particle (re-)acceleration mechanisms, with direct implications for the search for high-energy
neutrino sources. Combining centimeter-wavelength SVLBI with millimeter ground-based VLBI at comparable resolutions will enable detailed studies of
plasma stratification and instabilities in Active
Galactic Nuclei (AGN) jets, as well as the processes of jet formation, acceleration, collimation, and
magnetic field
evolution, for example through Faraday rotation mapping. The unprecedented sensitivity of the SKA-Mid will allow observations of active
galactic nuclei to very high
redshifts, tracing their
evolution and overcoming opacity caused by the (1+z) shift of intrinsic emission frequencies. Future centimeter SVLBI experiments will also probe scattering in the interstellar medium through
pulsar, maser, and AGN observations. Finally, the combination of multiple tied-array beams from the SKA
telescopes and the extremely long SVLBI baselines will enable ultra-precise astrometry using the next-generation MultiView technique, allowing measurements of extragalactic parallaxes of
pulsars and megamasers, proper motions of supermassive black holes, and even the astrometric detection of
exoplanets.
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All authors Y. Y. Kovalev, G. Bruni, T. An, H. E. Bignall, P. G. Edwards, C. Garcia-Miro, M. Giroletti, L. I. Gurvits, M. Kadler, J.-Y. Kim, E. V. Kravchenko, I. Liodakis, Y. Q. Liu, A. V. Plavin, A. V. Popkov, A. B. Pushkarev, T. Savolainen, Z.-Q. Shen, A. Tamar, E. Traianou
Cosmology and Nongalactic Astrophysics
Superoscillatory initial states during inflation: theory, CMB constraints, and prospects for galaxy clustering
Ali Nayeri
We construct an explicit boundary-action realization of superoscillatory initial states (SIS) for inflation, in which
quantum interference within a band-limited initial wavefunctional generates a spectrally localized Bogoliubov excitation with a rapidly winding phase. Starting from a quadratic boundary term on the initial time surface, we derive the Bogoliubov coefficients and the resulting
primordial curvature spectrum, obtaining a localized oscillatory feature fixed by the superoscillatory parameters $(a,N)$ rather than imposed phenomenologically. We compute the projection of this feature onto CMB angular power spectra and show that transfer-function smearing strongly suppresses the oscillatory component; full CAMB calculations confirm the qualitative effect and show that a simple Gaussian approximation overestimates the peak signal by about a factor of three. Using Planck 2018 TT data, we obtain an indicative matched-filter bound $\lambda \lesssim 0.05$ for a representative feature centered near the first acoustic peak, $\Delta k/k_* = 0.05$ at $k_* = 1.45\times 10^{-2}\,\mathrm{Mpc}^{-1}$. We further derive correlated predictions for polarization and the bispectrum, identify structural constraints that distinguish SIS from generic excited-state models, and show that
galaxy clustering provides a qualitatively more powerful probe because it preserves the full oscillatory structure that CMB projection suppresses. This framework provides a concrete and testable realization of how initial-state
quantum interference can imprint itself on cosmological observables.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Halo-Independent Quantum Sensor Probes of Low-Velocity Dark Matter
Muping Chen, Graciela B. Gelmini, Volodymyr Takhistov et al. (+1 more)
We present a
halo-independent framework for sub-GeV dark matter (DM) direct detection using
quantum sensors with sub-eV energy thresholds. Such detectors enable access to low DM velocities and may be sensitive to departures from the Standard
Halo Model that are challenging to probe with conventional direct DM detection experiments. The method expresses the DM scattering event rate in terms of a detector and particle model-dependent response function, and a universal
halo function common to all experiments to be determined from data. This allows the local DM velocity distribution to be constrained. As representative implementations, we consider TES (Al) and MKID (TiN)-like sensors and show that their differing material responses probe complementary regimes of the DM velocity distribution. Applying the framework to mock data derived from several
benchmark local
halo models, we demonstrate how the assumed
halo function could be reconstructed. This framework demonstrates the potential of
quantum sensors as a new avenue for mapping the local DM velocity distribution.
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All authors Muping Chen, Graciela B. Gelmini, Volodymyr Takhistov, Koichiro Yasuda
Astrophysics of Galaxies
The new era of Lyman alpha emitters (LAEs): Typical star formation histories of LAEs in the ILLUSTRIS simulation
I. Laferte-Urrutia, P.Troncoso-Iribarren, Alex Vera-Casanova et al. (+8 more)
This work seeks to understand the nature of Lyman-alpha emitting
galaxies in a cosmological context by analyzing their
star-formation histories in the IllustrisTNG100 simulation, applying a recent selection criterion. The sample at z = 2.0 includes 6051 Lyman-alpha emitters, classified into four classes (35%, 33%, 21%, and 11%) using KMeans, an unsupervised machine-learning clustering method. The first class reproduces the typical
star-formation history, characterized by the most intense
star formation at the time of observation. The remaining classes exhibit atypical
star-formation histories, with bursts occurring 0.3, 0.7, and 1.3 Gyr before the time of observation. The first class corresponds to
galaxies with lower mass, Lyman-alpha luminosity, and total
star-formation rate. We conclude that the classical definition of Lyman-alpha emitting
galaxies-low mass, low
dust content, and a single dominant burst-remains the most representative population (35% of the total sample), although other classes account for the remaining 65% of the cosmological sample.
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All authors I. Laferte-Urrutia, P.Troncoso-Iribarren, Alex Vera-Casanova, C. Artale, L. Guaita, E. Gawiser, Juan Magaña, C. Vega-Martínez, K. Lee, N. Firestone, P. Layana-Astudillo
High Energy Astrophysical Phenomena
3D particle-in-cell simulations of pulsar wind-disk interaction: application to the transitional millisecond pulsar PSR J1023+0038
Valentina Richard-Romei, Benoît Cerutti, Alessandro Papitto et al. (+1 more)
Transitional millisecond
pulsars constitute a peculiar subclass of
neutron stars in which the
pulsar alternates between
accretion-powered and rotation-powered states, depending on the variations in the mass
accretion flow coming from a low-mass companion
star. A third intermediate state, referred to as “sub-luminous disk state”, has been identified. During this state, observations indicate the presence of a disk surrounding the
pulsar, and the system exhibits intriguing features, such as broad optical and X-ray pulsations characterized by a high luminosity. To date, no ab initio model of a
pulsar wind interacting with an
accretion disk has been developed to address these observables. We perform three-dimensional particle-in-
cell simulations of a
pulsar magnetosphere surrounded by a perfectly conducting
torus to model the interaction between the
pulsar wind and the disk. We find that the presence of the disk induces a significant reconfiguration of the magnetosphere compared to the rotation-powered state, leading to enhanced
plasma density at the inner disk boundary, increased
magnetic field strength, and more efficient
plasma isotropization and particle acceleration. As a result, the synchrotron radiation is substantially enhanced, and characterized by a strong continuous component and either one or two-peaked light curves, depending on the
pulsar's
magnetic obliquity. The polarization degree is reduced compared to isolated systems, and its energy dependence is explored. The rotation of the polarization angle can also be altered, depending on the observer's viewing angle. The model successfully reproduces some of the main features of the optical and X-ray pulsed emission originating from PSR J1023+0038, thereby corroborating the scenario in which these pulsations originate from synchrotron radiation generated as the
pulsar wind interacts with the inner edge of the disk.
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All authors Valentina Richard-Romei, Benoît Cerutti, Alessandro Papitto, Riccardo La Placa
Cosmology and Nongalactic Astrophysics
Bridging Theory and Observation in the SKA Era: A Cosmological Polarized Radiative Transfer Framework for Point-to-Point Polarized Sky Comparisons
Jennifer Y. H. Chan, Alvina Y. L. On, Paul C. W. Lai et al. (+1 more)
Realizing the full scientific potential of the SKA requires not only revolutionary instrumentation but also accurate modeling of light propagation in an evolving, expanding Universe, in order to translate intensity and polarization data into physical insight about
magnetic fields and
cosmic plasma. When all-sky cosmological polarized radiative transfer (CPRT) calculations meets SKA observations, theory and data interlock to deliver a predictive, and testable picture of the evolving magneto-ionic Universe. This synergy transforms polarization observations – assembled into empirical maps of diffuse emission and rotation-measure (RM) grids of discrete sources – from descriptive data products into powerful astrophysical probes, advancing our understanding of
cosmic magnetism across space and time. The CPRT formalism – derived from fundamental conservation laws and incorporating relativistic, cosmological, and full radiative-transfer effects – provides a robust platform and a common framework for observers, theorists, and simulation experts to pursue shared scientific goals. Observers gain synthetic templates to interpret RM grids and polarization maps; theorists can directly confront models of magnetogenesis and
magnetic-field
evolution with data; and simulation experts obtain a post-processing tool to transform cosmological magneto-hydrodynamic (MHD) outputs into observable skies. Furthermore, CPRT serves as a powerful testbed when traditional RM-based methods reach their limitations – for example, in interpreting complex Faraday spectra, disentangling multiple intervening magnetized media, or achieving a coherent picture when diverse observational diagnostics – such as dispersion measure, synchrotron emission and spectral index, and
dust polarization – are combined.
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All authors Jennifer Y. H. Chan, Alvina Y. L. On, Paul C. W. Lai, Kinwah Wu
Cosmology and Nongalactic Astrophysics
An SKA-Low RM Grid for constraining the origin of cosmic magnetism
Shane P. O'Sullivan, Franco Vazza, Ettore Carretti et al. (+2 more)
Understanding the origin and
evolution of
cosmic magnetic fields is a key science goal for the SKAO. Recent advances in metre-wavelength (m-$\lambda$) Faraday rotation measure (RM) grids are enabling precision probes of
cosmic magnetism, with implications extending to early-Universe physics, AGN feedback, and the magnetized circumgalactic medium. Here we model the m-$\lambda$ polarized source counts to predict an RM Grid density with SKA-Low of $N(>P) \sim 5 ({P}/{100{\rm \mu Jy}})^{-0.75}\,\, {\rm deg}^{-2} $, where $P$ is the polarized intensity detection threshold. This represents at least an order of magnitude improvement over the current state-of-the-art. For a representative wide-area SKA-Low AA4 survey covering 10,000 deg$^2$ in $\sim$3,200 hours, we predict more than 50,000 RMs. Coupled with an expected RM precision of $\sim$0.05 rad/m$^2$, SKA-Low promises to produce the leading RM Grid survey for constraining the origin of
cosmic magnetism in the SKA era. These predictions can be partially tested during the Science Verification phase using the AA* Sky Model data. For example, at a nominal detection threshold of 240~$\mu$Jy/beam (8 times the noise in Stokes $Q$ and $U$), we expect $\sim$2.6 RMs/deg$^2$ (5x the current best m-$\lambda$ RM Grid density). Combining both wide-area and all-sky data, SKA-Low could detect up to 100,000 m-$\lambda$ RMs across its observable sky. Finally, we demonstrate new constraints on the origin of
cosmic magnetism by comparing cosmological MHD simulations with the LOFAR m-$\lambda$ RMs, and highlight the transformative advances an SKA-Low RM Grid will enable for precision studies of
cosmic magnetism.
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All authors Shane P. O'Sullivan, Franco Vazza, Ettore Carretti, Valentina Vacca, Francesca Loi
Astrophysics of Galaxies
The Multi-phase HI of the Milky Way and Nearby Galaxies
Marc-Antoine Miville-Deschênes, J. R. Dawson, Narendra Nath Patra et al. (+30 more)
Atomic hydrogen (HI) is the dominant baryonic component of the interstellar medium (ISM) in Milky Way-like
galaxies and the reservoir from which molecular clouds and
stars ultimately form. The condensation of diffuse HI into cold structures is governed by a complex interplay between radiative cooling,
turbulence,
magnetic fields,
stellar feedback, and
galactic dynamics, acting over scales ranging from astronomical units to kiloparsecs. Understanding how these processes regulate the thermal structure of the HI, the formation of cold clouds, and the transfer of matter and energy across scales is essential for connecting the small-scale physics of the ISM to the
evolution of
galaxies. Recent advances from SKA precursors have transformed our view of the atomic ISM, revealing a highly structured and filamentary cold medium, increasing the density of HI absorption measurements by orders of magnitude, and enabling new approaches to infer the thermodynamic and
magnetic properties of the gas from spectral-line
datasets. SKA-mid will provide the first comprehensive characterization of HI as a multi-phase, turbulent, and magnetized medium across the Milky Way and nearby
galaxies. Its combination of sensitivity, angular resolution, spectral resolution, and survey speed will enable matched emission-absorption studies, dense optical-depth grids, and detailed mapping of the atomic-to-molecular transition over a broad range of environments. Combined with polarization, Zeeman, recombination-line, and multi-wavelength observations, SKA-mid will establish a unified observational framework to study the
evolution of diffuse matter in
galaxies, in connection with
star formation, from the
Solar neighborhood to
galactic scales.
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All authors Marc-Antoine Miville-Deschênes, J. R. Dawson, Narendra Nath Patra, Erwan Allys, Prerana Biswas, Frances Buckland-Willis, Susan E. Clark, James Dempsey, John Dickey, Adriana Gazol, Benjamin Godard, Patrick Hennebelle, Alex S. Hill, Min-Young Lee, Minjie Lei, Callum Lynn, Antoine Marchal, Naomi McClure-Griffiths, Claire Murray, Van Hiep Nguyen, Marta Nowotka, Theo J. O'Neill, Josh E. G. Peek, Nickolas M. Pingel, Mary Putman, Daniel Rybarczyk, Nirupam Roy, Amit Seta, Sarkar Sougata, Juan Diego Soler, Enrique Vazquez-Semadeni, Trey V. Wenger, Catherine Zucker
Cosmology and Nongalactic Astrophysics
Cosmology from Clustering of Continuum Galaxies
Jacobo Asorey, Catherine L. Hale, Sebastian von Hausegger et al. (+6 more)
The distribution of
radio continuum
galaxies is a useful, fast, and accessible probe of the matter distribution in the Universe, enlightening us about the Universe's initial conditions, the physics of dark matter, and the nature of the mysterious dark energy. However,
radio continuum
galaxies alone cannot easily be localised in the radial direction, and cross-identification of host sources from optical catalogues is challenging across wide area surveys. Moreover, there are several
redshift-dependent properties of
radio galaxy populations that all need accurate modelling to make reliable inferences about fundamental physics. These include accurate measurements of the
redshift distribution of
radio sources ($dN/dz$), the coupling between
radio galaxies and the underlying matter distribution (quantified by the
galaxy bias, $b(z)$), and the true flux distribution $N(S,z)$ of the
radio sources (magnification bias). The amount of encoded cosmological information depends on the survey properties and the level of homogeneity across its footprint. In this chapter, we demonstrate the cosmological potential of a 20,000 sq. deg survey with the SKAO in AA4 configuration, using 10,000 hours of observations. Such a survey will reach $\mathcal{O}(\mu\mathrm{Jy/beam)}$ sensitivities and detect $\mathcal{O}$(300-400 million)
radio sources, the largest sample of
radio continuum
galaxies to date. This surpasses the number of sources assumed for the previous SKA cosmology Red Book. We predict the angular clustering of such a survey, using mocks accounting for potential
telescope systematics, and discuss which data corrections may be needed when these systematics cannot be accurately modelled.}
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All authors Jacobo Asorey, Catherine L. Hale, Sebastian von Hausegger, David Parkinson, Chandra Shekhar Saraf, Jonah D. Wagenveld, Benedict Bahr-Kalus, Syed Faisal ur Rahman, Ziad Sakr
Astrophysics of Galaxies
Small-scale Magnetic Fields in the Milky Way and Nearby Galaxies
Yik Ki Ma, Amit Seta, Aritra Basu et al. (+13 more)
Magnetic fields in
galaxies span decades in physical scale, from the coherent
magnetic fields on
galactic scales (> kpc) to the random
magnetic fields from 100 pc to the resistive scale of the
galactic plasma (i.e. ~1e6 cm). While many
radio studies to date have placed more emphasis on the large-scale
galactic magnetic fields than the small-scale counterparts, the emerging SKA will greatly facilitate accurate, detailed studies of the small-scale (< 100 pc)
galactic magnetic fields. In this Chapter, we highlight the importance of understanding the small-scale
galactic magnetic fields in furthering our understanding of
star formation,
galaxy evolution, and the fundamental physics of magnetohydrodynamics. Furthermore, we discuss some open questions in the research field and outline several possible large observation programmes with the SKA Array Assembly 4 (AA4).
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All authors Yik Ki Ma, Amit Seta, Aritra Basu, Sebastian Hutschenreuter, Marco Padovani, Georgia V. Panopoulou, Jeroen M. Stil, Craig S. Anderson, Lucia Armillotta, Jennifer Y. H. Chan, Marijke Haverkorn, Roland M. Crocker, Timea O. Kovacs, Sunil Malik, S. A. Mao, Kierra J. Weatherhead
Earth and Planetary Astrophysics
A Look at Eight Outbursts of Comet 7P/Pons-Winnecke
Ky Huynh, Michael S. P. Kelley, Jessica M. Sunshine et al. (+6 more)
Cometary outbursts may be used as a means to infer the physical processes occurring on cometary
nuclei. To that end, we studied eight outbursts of comet 7P/Pons-Winnecke identified between 2021 June 3 and 2021 August 31. The data analyzed consisted of optical images and derived photometry of the comet from the Las Cumbres Observatory network of
telescopes. The outburst strengths relative to the ambient coma ranged from -0.2 to -1.1 mag, and the ejecta themselves had apparent brightnesses ranging from 17.4 to 13.3 mag. The morphologies of the ejecta varied, suggesting that the events may have originated from different sources across the
nucleus. An order of magnitude estimation of the ejecta masses ranged from 10$^{5}$ - 10$^{6}$ kg, similar to other mini-outbursts of comets. The surface-area normalized outburst rate estimated during this time period is similar to comets 41P/Tuttle-Giacobini-Kresák, 9P/Tempel 1 and 46P/Wirtanen, but 10 times larger than that observed at comet 49P/Arend-Rigaux. However, a comparison to the mini-outburst rate of comet 67P/Churyumov-Gerasimenko reveals significant discrepancies between Rosetta spacecraft results and those from ground-based
telescopes. We also investigate whether or not cometary outbursts from 7P in the 19th century are needed to explain outbursts in meteor shower rates observed in the 20th century.
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All authors Ky Huynh, Michael S. P. Kelley, Jessica M. Sunshine, Quanzhi Ye, Tim Lister, Dennis Bodewits, Adam McKay, Megan E. Schwamb, Helen Usher
Earth and Planetary Astrophysics
A Potential Signature of HD 7977's Passage Among Observed Long-Period Comet Orbits
Nathan A. Kaib and Sean N. Raymond
It is generally presumed that the
tidal field of the Milky Way's disk is the main perturbation that has driven observed long-period comets (LPCs) from the Oort cloud into the inner
solar system. The tide's influence on the Oort cloud should produce a distinct anisotropy in the arguments of perihelion ($\omega$) of dynamically new LPCs with semimajor axes ($a$) over 10$^4$ au. Simulating LPC production dominated by the
Galactic tide, we find that observed dynamically new LPCs are more isotropic than expected. Meanwhile, our simulation exhibits much better agreement between simulated and observed “returning” LPCs that have made a handful of passages through the inner
solar system prior to discovery. The isotropy of new LPCs can be explained if the Oort cloud is much less centrally concentrated than the conventional Oort cloud formation model predicts. However, a second possibility also exists. Additional simulations we perform show that the observed $\omega$ distributions of new and returning LPCs can both be well-replicated if the
star HD 7977 passed within $\sim$6000–10000 au of the Sun $\sim$2.5 Myrs ago. In such a scenario, our
solar system is still undergoing the latter stages of a comet shower. These simulations imply the modern observed LPC flux is $\sim$twice as high as the longer-term (tide-dominated) rate. This also implies that estimates of the Oort cloud's population should be revised downward by a factor of $\sim$2. Our LPC analysis predicts the upcoming
Gaia data release will favor an HD 7977 impact parameter of $\sim$6000–10000 au.
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