High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Transient PULSE: Code for the Transient Propagation of UltraLight (pseudo)Scalars to Earth
Jason Arakawa, Charles Cheung, Muhammad Hani Zaheer et al. (+2 more)
We present Transient PULSE, a software package that numerically implements a previously developed source-to-detector framework for transient ultralight bosonic signals from astrophysical bursts. Predicting these signals relies on connecting the source emission spectrum to its
evolution during propagation and the resulting observables at a terrestrial detector. The package discretizes a user supplied energy spectrum into momentum modes, propagates them through a specified matter density profile and constructs the time-frequency energy density distribution at Earth, accounting for dispersion and in-medium screening effects. This treatment accommodates non-Gaussian source spectra and provides inputs for detector specific analyses. A complementary analytical module estimates coupling sensitivities, arrival time delays and screening thresholds from parameterized source and detector properties.
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All authors Jason Arakawa, Charles Cheung, Muhammad Hani Zaheer, Volodymyr Takhistov, Marianna Safronova
Instrumentation and Methods for Astrophysics
International Astrophysical Consortium for High-energy Calibration: Summary of the 18th IACHEC Workshop
K. K. Madsen, C. E. Grant, V. Burwitz et al. (+14 more)
In this report we summarize the activities of the International Astronomical Consortium for High Energy Calibration (IACHEC) from the 18th IACHEC Workshop at Pelham, Germany. Fifty-six scientists directly involved in the calibration of operational and future high-energy missions gathered during four days to discuss the status of the cross-calibration between the current international complement of X-ray observatories, and the possibilities to improve it. This summary consists of reports from the Working Groups with topics ranging across: the identification and characterization of standard calibration sources, multi-observatory cross-calibration campaigns, appropriate and new statistical techniques, calibration of instruments and characterization of background, preservation of knowledge, and results for the benefit of the astronomical community.
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All authors K. K. Madsen, C. E. Grant, V. Burwitz, H. Earnshaw, K. Forster, M. Guainazzi, V. L. Kashyap, H. L. Marshall, C. B. Markwardt, F. Meeker-Fürst, E. D. Miller, L. Natalucci, P. P. Plucinsky, M. Shidatsu, H. Suzuki, Y. Terada, A. Tümer
High Energy Astrophysical Phenomena
GRB 181201A: Spectropolarimetric Constraints on Prompt Emission and Magnetic Field Structure
Dhruv S. Bal, Nikita S. Khatiya, Philippe Laurent et al. (+3 more)
Gamma-ray bursts (GRBs) have served as testbeds for high-energy astrophysical phenomena since their discovery over 50 years ago. GRB detections reveal diverse properties across events, complicating efforts to constrain their emission mechanisms,
magnetic fields, jet structures, and compositions. Spectropolarimetry is a powerful tool utilized to disentangle these properties. INTEGRAL/IBIS has previously detected three polarized GRBs 041219A ($65\pm 26$%), 061122 ($>$33%) and 140206A ($>$28%). We present the time-integrated and time-resolved analyses of the fourth-polarized GRB 181201A. This GRB exhibits high polarization ($81.5^{+17.2}_{-15.7}$%) over three time bins with the highest signal-to-noise ratio, and the polarization angle (PA) shows a modest temporal
evolution. The
photon index does not cross the synchrotron line-of-death and shows a hard-to-soft
evolution. A high degree of polarization (PD) tends to disfavor a photospheric emission model, as previous studies indicate that this model yields PD $<$ 20%. A modest
evolution in the PA points towards a non-axisymmetric jet with a multi-patch emission. Our results indicate that under standard synchrotron conditions, the
magnetic field is coherent but lacks global structure. Moreover, the field has multiple patches, but only one or a few dominate due to high degrees of polarization, which overlap with the intrinsic maximum of synchrotron emission within 3$\sigma$ errors. The high PD is also indicative of the Compton Drag scenario, but only under certain conditions, such as viewing the relativistic jet near its edge. However, given our error bars and the scope for improvement in our pipeline, we cannot strongly favor either scenario; both may remain viable.
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All authors Dhruv S. Bal, Nikita S. Khatiya, Philippe Laurent, Diego Götz, Dieter H. Hartmann, Ramandeep Gill
Astrophysics of Galaxies
Binary-lens amplification of starlight: from magnification flares to quasi-periodic tracking of orbital evolution
Hanxi Wang, Bence Kocsis and Miguel Zumalacárregui
Supermassive black hole binaries (SMBHB) are expected at the center of
galaxies as a result of
galaxy mergers. The dynamics and
evolution of SMBHBs shed light on the
evolution and formation of
galaxies, the gravitational wave background and the nature of
gravity. Many methods have been proposed to identify sub-parsec SMBHBs via the detection of gravitational waves or the modulation of the emission from the surrounding gaseous environment. In a previous study, we proposed a new method of identifying SMBHBs in non-active galactic
nuclei via gravitational
lensing. The caustics, i.e. the source positions with a divergent magnification, exhibit a complex extended geometry which rotates with the binary period. Each caustic-crossing produces an extreme magnification by up to a factor of $10^{6}$. In this work, we generalize the previous study and describe the rich phenomenology of binary-lens amplification of starlight (BLAST). We explore the electromagnetic transients produced when accounting for the relative proper motion of the source, either a single or a binary
star, the eccentricity and precession of the SMBHB, and the relative inclination. Systems where a
star rapidly drifts across the caustic produce a single- or double-peaked
flare. In the opposite limit, a
star with no relative proper motion produces quasi-periodic lensed starlight (QPLS), i.e., repeated peaks that track the system's orbital
evolution. We determine the expected magnification and peak duration in different circumstances, and calculate the magnification curves and their
Fourier transforms. This study may help construct search pipelines to identify SMBHBs in electromagnetic time-domain surveys.
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Instrumentation and Methods for Astrophysics
Refurbishment and Cryocooler Upgrade of the CPAPIR Wide-Field Near-Infrared Camera: Design, Integration, and Lessons Learned
Philippe Vallee, Jonathan St-Antoine, Lison Malo et al. (+5 more)
The CAmera PAnoramique Proche Infrarouge (CPAPIR) is a wide-field near-infrared imager that has been operating at the Observatoire du Mont-Mégantic (OMM) since 2004. After more than two decades of service, the instrument required a major refurbishment due to detector degradation, including the loss of one quadrant, as well as operational constraints associated with its
liquid-nitrogen cooling system. To extend the instrument's lifetime and reduce maintenance requirements, the detector was replaced and the cooling system upgraded through the integration of a Sunpower CryoTel DS30 cryocooler. This paper presents the thermal and mechanical redesign of the instrument, including finite element analysis (FEA), three-dimensional CAD modeling, hardware selection, and laboratory validation. Particular
attention is given to the challenges encountered during integration and testing, notably vibration mitigation and cryogenic system implementation. The resulting performance improvements and lessons learned from the upgrade are discussed. The upgraded instrument is scheduled for on-sky commissioning at the Observatoire du Mont-Mégantic in summer 2026.
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All authors Philippe Vallee, Jonathan St-Antoine, Lison Malo, Frederique Baron, Sylvie F Beaulieu, Rene Doyon, Etienne Artigau, Fidele Robichaud
Solar and Stellar Astrophysics
Dynamics of a switchback-like magnetic deflection induced by a propagating coronal jet
Jade Touresse, Etienne Pariat, Clara Froment et al. (+1 more)
Parker Solar Probe (PSP) revealed the ubiquity of switchbacks (SBs), sharp, localised
magnetic deflections in the nascent solar wind, renewing interest in their origin. One proposed mechanism involves solar jets: collimated, impulsive features driven by
magnetic reconnection that launch Alfvénic torsional wavefronts into the heliosphere. We test whether realistic spacecraft sampling of a propagating solar jet produces in-situ signatures consistent with PSP observations. We also examine the 3D
magnetic topology of the resulting structures and how deflection amplitudes evolve with the ambient
plasma environment. We perform a 3D magnetohydrodynamic simulation of a solar jet in the ambient solar wind,
embedding a virtual spacecraft trajectory based on PSP's actual 22nd-perihelion orbit to generate synthetic measurements. The simulation reproduces SB-like signatures with durations and profiles consistent with PSP observations, confirming earlier results from simplified trajectories. We visualise the fully 3D
magnetic topology of a jet-driven SB region, identifying two field-line families: one with a single deflection and another with two sequential deflections along the same field line. Both are outward-propagating Alfvénic structures. Deflection amplitudes depend strongly on background
plasma $\beta$, increasing substantially in low-$\beta$ regions and evolving more moderately where $\beta \sim 1$. These results show that solar jets can produce Alfvénic, SB-like structures along realistic spacecraft trajectories. Their
topology is inherently 3D and structurally diverse, and their
evolution depends on ambient
plasma $\beta$. Complete
magnetic reversals would require longer residence times in low-$\beta$ environments. Our findings support a solar origin for a fraction of SBs and constrain interpretations of their underlying
magnetic structure.
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All authors Jade Touresse, Etienne Pariat, Clara Froment, Peter F. Wyper
Earth and Planetary Astrophysics
Revealing the Spatial Distribution of Dust and Plasma Solitary Waves in Jupiter's Innermost Magnetosphere Using Juno Waves Observations
Wenyu Zhang, Hao Cao, William S. Kurth et al. (+6 more)
Jupiter's faint ring system contains micron- and submicron-sized dust whose dynamics are influenced by the
planet's rapidly rotating
magnetic field. Optical observations have established the morphology of the main ring and
halo, but tenuous dust close to Jupiter remains difficult to characterize. We analyze nearly a decade of in-situ Juno Waves electric-field measurements using a two-stage convolutional neural network to identify and classify dust impacts, solitary waves, and other
plasma waves. These in-situ dust-impact detections reveal a radially evolving structure extending well inside the traditionally observed
halo. In the innermost region, dust is concentrated in a compact, equatorially symmetric layer, indicating that the optical inner boundary does not mark the end of the dust population. Farther outward, the layer expands vertically into a broad
halo before contracting toward the main ring, directly revealing the toroidal morphology of the Jovian
halo. Dust number density is enhanced within the
halo and near the main-ring–
halo transition. The vertical distribution also develops hemispheric asymmetries that vary with radial distance, consistent with an influence of Jupiter's
magnetic geometry on charged-dust dynamics. In contrast, solitary waves occur predominantly at high latitudes, and their mapped
magnetic footprints show a strong spatial correspondence with Jovian auroral structures, particularly the main auroral oval. Together, these in-situ measurements extend the remote-sensing picture of Jupiter's rings and reveal previously unresolved dust and
plasma structures in its innermost magnetosphere.
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All authors Wenyu Zhang, Hao Cao, William S. Kurth, Mitchell M. Shen, Darrelle Wilkinson, Donglai Ma, Martin Brennan, George Hospodarsky, Scott J. Bolton
High Energy Astrophysical Phenomena
Can bosenovae deplete the galactic dark matter?
Samuel Gómez Gómez and Joshua Eby
No: neither through the bosenovae of gravitational atoms formed around
stars and compact objects, nor through those of
boson stars formed in the galactic dark-matter
halo. We assume that all the dark matter consists of ultralight
bosons with attractive self-interactions, which can be captured in the gravitational potential of astrophysical objects or condense into self-gravitating configurations. When these systems collapse in a bosenova, part of their mass is turned into relativistic radiation that escapes the
galaxy. We bound the mass that a single object can eject and sum it over realistic models of the Milky Way and of other types of
galaxies. For gravitational atoms, with realistic stellar populations and stellar
evolution, the
stars of the Milky Way deplete at most $\epsilon^{\rm GA}_\star\simeq3\times10^{-9}$ of its
halo, and the pump is equally negligible in other
galaxies. The central black hole, Sgr A$^*$, could reach $\epsilon^{\rm GA}\sim10^{-3}$, but only for a
boson mass disfavoured by ultrafaint dwarf
galaxies and beyond the validity of the perturbative treatment, where only a
geometric bound on the dark matter flux is available. For
boson stars feeding on the rest of the
halo, these would radiate at most $\sim3\times10^{-5}$ of the Milky-Way
halo and $0.1\%$ of a DF2-like one.
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Solar and Stellar Astrophysics
Modelling the 6.7 GHz Methanol Flaring in G358.93-0.03 Using the Maxwell-Bloch Framework
Ningyan Fang, Toktam Rashidi, Yoshinori Yonekura et al. (+4 more)
We model selected 6.7 GHz methanol
flare profiles in G358.93-0.03 using the one-dimensional Maxwell-Bloch framework. The 2019 non-periodic
flare, associated with an
accretion burst, produced complex single-dish light curves characterized by sharp rises, multiple peaks, secondary structure, and extended decays. For six representative velocity channels, we model each light curve as a sum of scaled intensity responses from effective emitting systems driven by phenomenological pump pulses of fixed width but with component-dependent background rates, amplitudes, and arrival times. The inferred initial inverted column densities correspond to characteristic superradiance timescales $T_{R,0} \simeq 0.3$-$1.4~{\rm d}$, which are shorter than the adopted dephasing and relaxation timescales, $T_2 = 6.9~{\rm d}$ and $T_1 = 144.4~{\rm d}$. The fitted components therefore lie in the fast-transient superradiance regime. Existent VLBI observations motivate the possibility that a single-dish velocity channel blends emission from multiple unresolved flaring regions, although these observations are not used as direct fitting constraints. Although the decomposition is not unique, it provides a physically motivated description of the complex
flare morphology within a unified Maxwell-Bloch framework.
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All authors Ningyan Fang, Toktam Rashidi, Yoshinori Yonekura, Vahid Anari, Ross A. Burns, Martin Houde, Fereshteh Rajabi
Astrophysics of Galaxies
A Step-Like Transition Underlying the Life and Death of Galaxies
Zhicheng He, Enci Wang, Luis C. Ho et al. (+6 more)
How
galaxies stop forming
stars is a complex and central problem in astrophysics. Numerous physical mechanisms have been proposed, yet a simple, unified framework connecting these mechanisms remains lacking. Here, we derive a step-function quenching response from the fundamental principle of gas mass conservation, governed by the competition between gas-supply and gas-depletion timescales. This response also enables the gas-supply timescale to be inferred from the observed quenched fraction. Applying this method to approximately 350,000
galaxies, we find a characteristic gas-supply timescale of ~1 Gyr, reveal distinct inside-out and outside-in quenching signatures associated with supermassive black holes and dark matter
halos, respectively, and identify
galaxies with intermediate stellar surface mass densities as occupying a critical state for quenching and rejuvenation. Our work establishes a unified physical framework in which a simple step-function response captures how diverse physical processes regulate
galaxy quenching and the resumption of
star formation through their effects on the competition between gas-supply and gas-depletion timescales.
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All authors Zhicheng He, Enci Wang, Luis C. Ho, Yingjie Peng, Huiyuan Wang, Yong Shi, Tao Wang, Yongquan Xue, Tinggui Wang
High Energy Astrophysical Phenomena
A Parsec-Scale Transient High-Frequency-Peaked Radio Source in the Very Large Array Sky Survey Brightening and Fading over a Decadal Timescale
Yuyang Chen, B. M. Gaensler, Maria R. Drout et al. (+10 more)
A subset of active galactic
nuclei (AGN) manifests as compact
radio sources with peaked
radio spectra, commonly referred to as peaked-spectrum (PS) sources. Generally, PS sources are interpreted as young
radio jets, but the early
evolution of the jet is rarely observed and not fully understood. Here, we present VT J182357-234511 (VT J1823-2345), a
radio transient in the Very Large Array Sky Survey (VLASS) that resembles a PS source. Notable properties of VT J1823-2345 include: (i) brightening by a factor of 3 between 1996 and 2021 at 1.4 GHz, (ii) peaked spectra with high frequency peaks at $\nu_{\mathrm{p,obs}}\gtrsim6\,\mathrm{GHz}$, (iii) a peaked 3 GHz light curve that has been fading since 2023, (iv) a resolved Gaussian (major-axis) size of 0.4 mas in 2024, and (v) a linear polarization fraction $p_{\mathrm{L}}\simeq0.73\%$ at 8.8 GHz with an extreme Faraday rotation measure $\mathrm{RM_{\mathrm{obs}}} \sim +12,000\,\mathrm{rad}\,\mathrm{m}^{-2}$. On the sky, VT J1823-2345 coincides with a
supernova remnant and an F-type
star, but no background
galaxy is seen. Based on the multi-wavelength properties, we disfavor Galactic transients, explosive extragalactic transients, and blazar variability as plausible explanations. We argue that VT J1823-2345 is consistent with a "short-lived" parsec-scale PS source with a decades-old jet that does not grow into a large-scale
radio galaxy. From comparing the full VLASS light curves, we speculate that VT J1823-2345 is similar to many VLASS nuclear transients reported in the literature, which may represent an emerging class of transient
radio jets, perhaps related to episodic AGN activity or jetted tidal disruption events.
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All authors Yuyang Chen, B. M. Gaensler, Maria R. Drout, Dillon Z. Dong, Emmanuel Momjian, Tracy Clarke, Wendy Peters, Emil Polisensky, Ariel D. Amaral, Katie Auchettl, Ylva Götberg, Kovi Rose, Peter Senchyna
High Energy Astrophysical Phenomena
LHAASO Constraints on New-Source Cosmic Rays:Abundance Scenarios and Injection Spectral Indices
Xu-Lin Dong, Pei-Pei Zhang, Qi-Ling Chen et al. (+2 more)
Recent LHAASO observations indicate that microquasars and massive
star clusters contribute to Galactic
cosmic rays, and likely also to the pre-knee spectral hardening. Their markedly different astrophysical environments, compared with
supernova remnants (SNRs), may imprint distinct
cosmic-ray abundances. We investigate the spectra and composition of new-source
cosmic rays under two abundance scenarios: Case-1, the SNR-like composition with enhanced heavy
nuclei, and Case-2, the surface abundances of microquasar companion
stars. We constrain injection spectral indices using LHAASO
proton, helium, and all-particle spectra, and use their <lnA> data for model discrimination. Under the assumption of a unified heavy-element injection spectrum, Case-2 fits the <lnA> data significantly better than Case-1, but at the cost of large, physically unmotivated differences between heavy-element and He injection indices. This suggests the need to either relax the unified heavy-element injection-index assumption or explore alternative abundance patterns. We predict that if the new-source composition follows Case-1, the individual elemental spectral indices before the knee should remain nearly consistent; if it follows Case-2, the Mg, Si, and Fe spectra will be significantly softer than those of He, C, and O. Future element-resolved energy-spectrum measurements by HERD and LHAASO will provide a decisive test of this discriminating feature.
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All authors Xu-Lin Dong, Pei-Pei Zhang, Qi-Ling Chen, Shu-Wang Cu, Yi-Qing Guo
Astrophysics of Galaxies
The contact frontier in Galactic civilization networks: radial structure and the Galactic habitable zone
Kohji Tsumura
The probability of interstellar contact depends not only on the abundance of technological civilizations but also on their spatial connectivity. Treating civilizations as nodes linked whenever their separation is smaller than the distance a signal travels within a communicative lifetime, we determine the radial structure of Galactic civilization networks. An exponential stellar disc replaces the uniform disc of earlier work, and the fraction of
stars hosting civilizations may vary with radius as a Galactic Habitable Zone (GHZ). The isolation, contact and network transitions are frontiers several kiloparsecs wide, not boundaries: the contact frontier is set entirely by the disc scale length, and the network frontier, broadened by gradient percolation, stays near 1.5 scale lengths. The two frontiers overlap over a band containing the Sun, where both transitions proceed at once. Within this factorized GHZ model, the radius of peak civilization density depends only logarithmically on the strength of
supernova sterilization, and the wide range of published peak radii, from the Galactic centre to 12 kpc, is reproduced primarily by varying that one parameter. Under the present normalization, the location of the zone has only a modest effect on the local contact probability, whereas the modelled Galactic connectivity is minimized when the civilization-density peak lies near the solar Galactocentric radius, where current determinations place the peak.
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Cosmology and Nongalactic Astrophysics
Joint Line Intensity Recovery from Multi-Tracer Cross-Correlations
Carlos E. Sierra and Kirit S. Karkare
Line intensity mapping (LIM) provides a unique window into the high-
redshift universe, but the separation of signals from overlapping emission lines and bright continuum foregrounds remains a central analysis challenge. At millimeter wavelengths in particular, [CII], [CI] and numerous CO transitions overlap with comparable brightness, leading to significant spectral confusion. This work presents a joint likelihood framework that incorporates multi-tracer cross-correlations both between distinct LIM tracers and with external
galaxy surveys. By jointly fitting all auto- and cross-spectra between the LIM and
galaxy data, this approach combines the spatial and spectral information in each
dataset to break degeneracies between overlapping lines and recover individual bias-weighted line intensities at fixed cosmology, even at
redshifts where no direct cross-correlation is available. We validate this framework on realistic mocks of an extended SPT-SLIM-like survey spanning 125-175 GHz over 100 deg$^2$, combined with an LSST Y1-like photometric
galaxy catalog, and recover CO(2-1) through CO(6-5) and [CI](1-0) over $0.3\lesssim z\lesssim4$ in the presence of bright continuum foregrounds. We demonstrate that adding the photometric
galaxy data tightens line constraints by a factor of $\sim$3-4 where the
galaxies overlap the lines in
redshift, and by $\sim$20-50% at higher
redshifts beyond the
galaxy coverage, where the gain comes indirectly from constraining the low-
redshift interlopers. These results highlight external tracer overlap as a primary consideration when optimizing the frequency coverage and footprint of near-future LIM experiments.
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Instrumentation and Methods for Astrophysics
Updates to STIS NUV Dark Calibration
Jacqueline Brown, Sean Lockwood, TalaWanda Monroe et al. (+2 more)
We present new superdark calibration files (DARKFILEs) and a new dark correction table (TDCTAB) for use with data taken by the Space
Telescope Imaging Spectrograph near-ultraviolet microchannel array (STIS NUV-MAMA) detector for HST Cycle 19 onward. These superdarks include 12 years of NUV dark exposures and make use of an updated temperature scaling equation developed in 2013 to more accurately characterize the dark rate. In tested
datasets, the new superdarks provide an average 3% increase in SNR and smooth out a ring artifact left previously by oversubtraction of the dark rate. The new superdarks and TDCTAB have been delivered to the Calibration Reference Data System (CRDS) and have been used to recalibrate all affected
datasets in the Mikulski Archive for Space
Telescopes (MAST).
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All authors Jacqueline Brown, Sean Lockwood, TalaWanda Monroe, Amy Jones, Joleen Carlberg
High Energy Astrophysical Phenomena
Rotochemical heating of neutron stars in 2D
Mikhail V. Beznogov, Jerome Novak, Dany Page et al. (+1 more)
The matter inside a spinning-down
neutron star (NS) undergoes a slow compression that may drive it out of chemical
equilibrium and, consequently, trigger non-
equilibrium nuclear reactions that can heat up the
star. This phenomenon is called rotochemical heating, and it is relatively well-investigated in the literature. Historically, it has been studied almost exclusively via 1D spherically symmetric models. However, rapidly rotating NSs are not spherically symmetric. We present pioneering simulations of rotochemical heating in full General Relativity in 2D axially symmetric models without relying on the slow rotation approximation. We explicitly follow thermal, mechanical, and chemical
evolution of rotating NSs as they
spin down taking into account both radial and angular distributions of temperature, composition, and mechanical structure. The simplest model is employed: only nucleonic composition, only the non-
equilibrium modified Urca process as the main heating/cooling mechanism, and no superfluidity. We analyze the impact of the
magnetic field strength as well as the effects of the heat blanketing envelope, initial rotation frequency, NS mass, and core EOS. Most of our conclusions coincide with the results of previous works on this topic, with one important exception. We have found a strong dependence of the cooling curves during the rotochemical heating phases on the core EOS, whereas in the literature it was regarded as very weak. The most likely explanation for this discrepancy is that the authors of the previous works have not considered EOSs with wide enough range of variation of the
symmetry energy as a function of density.
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All authors Mikhail V. Beznogov, Jerome Novak, Dany Page, Adriana R. Raduta
Earth and Planetary Astrophysics
Probing Planet Formation within 10 au: Dust Substructures in Extremely Compact Protoplanetary Disks
Pietro Curone, Gijs D. Mulders, Nienke van der Marel et al. (+1 more)
ALMA high-resolution surveys have so far focused mainly on large, bright protoplanetary disks, where substructures are routinely detected, leaving compact disks poorly characterized. Yet, the survival of millimeter emission in Class II sources implies that radial drift must have been halted by pressure traps, previously undetected due to limited angular resolution. We present ALMA Band 7 (0.9 mm) continuum observations of 11 of the smallest ($R_{68} < 10$ au) Class II disks in Lupus, reaching $0.02''$ (2 au) resolution, the highest currently available with ALMA at this wavelength. We detect substructures in 4 disks, including a clear inner cavity of radius 1.6 au, and hints of substructure in 3 more. Two disks also host faint outer rings beyond their bright inner core. Combining these results with demographic information on Class II disks observed with ALMA, we examine how the substructure detection rate varies with disk size, restricting to disks whose diameter is resolved by at least 3 resolution elements. We find that nearly all disks ($\gtrsim$95%) larger than 30 au show substructures, compared to a still substantial $\sim$50% between 3 and 30 au, with the lower rate likely affected by optical depth. The
planet masses required to open gaps within 5 au fall in the super-Earth to mini-Neptune regime. These results demonstrate that substructures are ubiquitous across the disk population, and that
planet formation conditions can be probed down to a few au from the host
star.
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All authors Pietro Curone, Gijs D. Mulders, Nienke van der Marel, Laura M. Pérez
Cosmology and Nongalactic Astrophysics
Origin of the red spectral tilt in Inflation without an Inflaton
Raul Jimenez, Daniele Bertacca, Mariam Abdelaziz et al. (+3 more)
In Inflation without an Inflaton (IWI), a de Sitter (dS) background drives inflation, and the graviton bilinear generates scalar perturbations at second order, with no inflaton or additional fundamental scalar field. We investigate how this scenario can account for the observed scalar spectral tilt. The tensor-mode dependence of the scalar power spectrum gives the consistency relation $n_s-1=2n_T$, since it contains four tensor mode functions. The scalar spectral tilt $n_s\simeq0.9649$ at CMB scales therefore gives $n_T\simeq-0.0175$, independent of the tensor-to-scalar ratio $r$, hence different from the standard single-field slow-roll prediction $n_T=-r/8$. A full time-dependent calculation of $\phi_2$ in exact dS leads to an almost scale-invariant scalar power spectrum, with a small blue infrared residual on the order of $n_s-1\simeq+4\times10^{-4}$. In order to account for the observed red tilt, we introduce a slow drift in the Hubble rate, parametrized by $\varepsilon=-\dot H/H^2$. The tensor tilt is then given by $n_T=-2\varepsilon$, implying $n_s-1\simeq-4\varepsilon$, at leading order. The observed tilt requires $\varepsilon_\ast\simeq0.0088$, far exceeding the drift that can be sustained by the classical graviton backreaction, for which we find $|\varepsilon_{\rm self}|\lesssim10^{-11}$. Therefore, we investigate the
quantum break-time of dS as the origin of the background
evolution. In this picture, the scalar tilt becomes $n_s-1=-4C_qN_{sp}(H/m_{pl})^2$, where $C_q$ is an order-one depletion coefficient, and the tilt is directly connected to the particle content of dS, $N_{sp}$. The
evolution of the drift itself further predicts a positive running of $\alpha_s=+\tfrac12(1-n_s)^2\simeq+6\times10^{-4}$. These results conclude the distinctive observational predictions of the IWI scenario, establishing it as a falsifiable alternative to standard inflaton-driven models.
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All authors Raul Jimenez, Daniele Bertacca, Mariam Abdelaziz, Sabino Matarrese, Angelo Ricciardone, Marisol Traforetti
Cosmology and Nongalactic Astrophysics
Bouncing Bianchi Type I Universes with Interacting Vacuum
Marco Bruni, Rodrigo Maier and Thomas Waters
We investigate the global dynamics and cosmological viability of non-singular solutions in an anisotropic Bianchi type I universe featuring an interacting
vacuum energy component $V$ and a perfect fluid $\rho$, extending previous work based on a Robertson-Walker geometry. By modeling the energy-momentum transfer via a phenomenological four-vector $Q_\mu$, we reduce the field equations to a four-dimensional autonomous dynamical system for the expansion rate $\Theta$, total shear $\sigma$, energy density $\rho$, and
vacuum component $V$. We examine two distinct forms for how the interaction depends on $\rho$ and $V$: a linear coupling $Q_1 \propto \Theta[\xi(V_\Lambda - V) + \chi \rho]$ and a non-linear coupling $Q_2 \propto \Theta \rho (1 - V/V_\Lambda)$. Using a potential-energy analogy and phase-space analysis, we show that the linear model $Q_1$ naturally admits non-singular bouncing trajectories. In contrast, unlike the Robertson-Walker case, for the non-linear interaction $Q_2$, invariant boundary surfaces in phase space strictly constrain the domain of expansion ruling out cosmological bounce scenarios for physical matter configurations.
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Astrophysics of Galaxies
IRAC-Excess Galaxies in the NIRSpec Wide Survey: physical properties of bright EELGs at $z\sim7$ and implications for Reionization
Katherine Ormerod, Renske Smit, Joris Witstok et al. (+4 more)
We present an analysis of 23 Spitzer/IRAC excess
galaxies at $5.66 < z < 7.64$, observed as part of the NIRSpec Wide GTO survey. With NIRSpec PRISM spectroscopy, we measure a median rest-frame [OIII]$+\rm{H}\beta$ EW $=1583$~Å, consistent with predictions from the pre-JWST selection and we identify $17/23$ $(\sim74\%)$ of our sample as extreme emission line
galaxies (EELGs), based on a selection of [OIII]$+\rm{H}\beta$ EW $\geq1000$~Å. The typical EELG is powered by
star-formation rather than active galactic
nuclei (AGN) based on their line widths, line ratios and absence of high-ionization lines, though we cannot exclude an AGN contribution in a few individual sources. We find that our luminous ($\langle M_\mathrm{UV}\rangle=-20.7$) EELG sample is characterised by sub-solar
metallicities $(7.38 < \rm 12 + \log(O/H) < 8.12)$, young stellar populations ($t_\star \sim 20$ Myr), and enhanced ionizing
photon production efficiencies, with median $\log_{10}(\xi_\mathrm{ion}/\mathrm{erg}^{-1}~\mathrm{Hz}) = 25.62$. We find that more UV luminous ($\sim L_\mathrm{UV, z=7}^\ast$) EELGs exhibit systematically lower O32 ratios than fainter ($\sim 0.1\times L_\mathrm{UV}^\ast$) EELGs at fixed [OIII]$+\rm{H}\beta$ EW, indicating less extreme radiation fields and/or lower gas densities than their fainter counterparts. Furthermore, bright EELGs exhibit low neutral hydrogen column densities, consistent with a scenario in which they have largely ionized their circumgalactic medium (CGM). Despite this, we find very low Lyman-$\alpha$ escape fractions ($<2$%), suggesting these systems reside in relatively small ($\lesssim 0.25$~pMpc) ionized regions of the intergalactic medium (IGM), possibly suggesting that bright
galaxies have a minor contribution to reionization.
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All authors Katherine Ormerod, Renske Smit, Joris Witstok, Anna de Graaff, Michael V. Maseda, Andrew J. Bunker, Chris Willott
Cosmology and Nongalactic Astrophysics
Thermalization of the Primordial Stochastic Gravitational-Wave Background
Hongguang Zhang, Zhengyang Qiu, Sirui Wang et al. (+1 more)
It is conventionally believed that the
Stochastic Gravitational-Wave Background (SGWB) from inflation provides information about the earliest universe. However, in this Letter, we present a different picture. Our analysis starts from the observation that the inflation-predicted spectrum implies gravitons reside in high-occupation states, which significantly enhances their self-interactions and triggers rapid thermalization. We show that approximately $80\%$ of the primordial gravitons participate in this thermalization, forming a Bose–Einstein distribution and thereby erasing the primordial information. Evaluated using typical inflation parameters, this thermalized spectrum yields a present-day peak frequency of $f_{0, \text{peak}}^{(\text{th})} \sim 1.4 \times 10^8 \, \mathrm{Hz}$ in the hundred-megahertz band with a peak amplitude of $\Omega_{0, \text{peak}}^{(\text{th})} \sim 3.5 \times 10^{-13}$. Due to the sharp drop-off away from the peak, the resulting spectrum lies beyond the reach of low-frequency observatories like PTAs, LISA, and LIGO, but remains uniquely accessible to high-frequency detectors such as microwave cavity resonators and dielectric haloscopes.
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All authors Hongguang Zhang, Zhengyang Qiu, Sirui Wang, Jiayi Wei
Instrumentation and Methods for Astrophysics
Geometrical and Optical Design of the GUEST Laser-Ranged Test Masses for the Detection of Gravitational Waves in the $\mu$Hz range
Dario Vetrano, Giada Bargiacchi, Nicolò Burzillà et al. (+5 more)
The GUEST (Gravitational Universe Exploration with Satellite Tracking) mission aims at detecting gravitational waves in the yet almost unexplored $\mu$Hz frequency range through high-precision orbital tracking. The unprecedented scientific objectives of this experiment demand equally advanced optical solutions: the highly eccentric orbit imposes dual measurement regimes; a low-velocity, long-range scenario at apogee and a high-velocity, short-range scenario at perigee. The substantial disparity between these conditions is addressed through a novel optical architecture incorporating two distinct types of Corner-Cube Retroreflectors (CCRs) with 1" and 2" apertures (CCR1 and CCR2, respectively). The proposed layout has been designed to ensure isotropy and homogeneity of the optical response while maintaining efficient packing over the spherical surface of the spacecraft. The resulting Optical Cross-Section (OCS) has been evaluated using a custom reduced-order model, which captures the behavior of individual CCRs under varying illumination conditions. This model has been calibrated by reconstructing the optical response of the LARES-2 satellite and has enabled a detailed assessment of the contributions of each CCR type along the GUEST orbit. Finally, sensitivity analyses have been conducted to investigate the impact of key design parameters, including the ratio between CCR types,
laser wavelength, spacecraft diameter, Dihedral Angle Offsets (DAOs), and mechanical configurations.
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All authors Dario Vetrano, Giada Bargiacchi, Nicolò Burzillà, Roberto Campagnola, Francesco Del Ferraro Iacobelli, Luca Porcelli, Simone Dell'Agnello, Diego Blas
Astrophysics of Galaxies
The ringing Large Magellanic Cloud: evidence for a recent dwarf-dwarf collision
Slater J. Oden, Bethany Garver, Joshua Povick et al. (+2 more)
Galaxy interactions are ubiquitous in the Universe and represent a primary pathway for
galaxy growth. Close passages of dwarf
galaxies can induce large-scale vertical oscillations in stellar disks, a phenomenon first identified in the Milky Way within the past decade. Here, we use recent red clump distance maps of the Large Magellanic Cloud (LMC) to show that its stellar periphery is vertically offset from the central disk plane by $\sim$1.2 kpc at radii of $\sim$8.5 kpc and exhibits an S-shaped warp reaching $\sim$3.6 kpc at $\sim$11.5 kpc. We compare these observations to an $N$-body simulation of the LMC-Small Magellanic Cloud (SMC) system, in which a direct collision between the Clouds excites vertical oscillations in the outer LMC disk with amplitudes of $\sim$1~kpc and a period of $\sim$600~Myr. The simulated disk best matches the observed vertical structure $\sim$260~Myr after the collision, although this timing depends on the adopted LMC model. At that time, the simulation reproduces the sign and radial onset of the observed offset and the orientation of the warp, but underpredicts the amplitude of the warp by a factor of $\sim$4-5. These results support a collision-driven origin for the large-scale vertical structure of the LMC disk and demonstrate that dwarf–dwarf interactions can reshape stellar disks on galactic scales.
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All authors Slater J. Oden, Bethany Garver, Joshua Povick, David L. Nidever, Victor P. Debattista
Solar and Stellar Astrophysics
HD 120678: a classical Be star with a tilting heartbeat disk
Dietrich Baade, Jonathan Labadie-Bartz and Thomas Rivinius
Classical Oe/Be/Ae
stars possess Keplerian circum-equatorial decretion disks which produce not just the eponymous emission lines but also the bewildering diversity of photometric variations on timescales above a few days. The variability is due to varying amounts and
geometric distributions of the circumstellar gas. The ASAS-3 V-band light curve of HD 120678 between March 2005 and November 2008 resembled an inverse P Cygni profile, which may have been a one-off event. The peak-to-valley amplitude reached ~0.9 mag. Before and after this photometric event, the Balmer emission lines and their variability matched those of classical Be
stars with an intermediate to low inclination angle. At the sharp minimum of the light curve, Gamen et al. (2012) observed shell-type profiles implying an edge-on (high-inclination) view. For the historical activity phases of gamma Cas and 59 Cyg, such a Be => Be-shell => Be sequence has been successfully interpreted as rotations of the disk plane. HD 120678 and a few other Be
stars add a not previously recognized phenomenon to the plethora of Be-
star variabilities, namely heartbeat light curves. Analogously to the distortion of heartbeat
stars, the variability is due to heartbeat disks gravitationally tilted by an additional
star as modeled by Marr et al. (2022) for Pleione. While the typical amplitudes of heartbeat
stars are only a few 0.01 mag, heartbeat disks can explain the ten times larger amplitudes observed in Be
stars.
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Astrophysics of Galaxies
Constrain the Size of Broad Line Region in NGC 1068 Using Sub-millimeter Excess
Qi Guo, Junzhi Wang, Lingrui Lin et al. (+3 more)
Constraining the size of broad-line region (BLR) close to the
accretion disk in active galactic
nuclei (AGNs) is key to understand the central engine and
evolution of AGN. We propose a new method to constrain the BLR size, based on millimeter to sub-millimeter spectral energy distribution (SED), from which a sub-millimeter excess may be found. Such excess can be used to determine the solid angle of the free-free emission region from BLR, as a region with high electron density and optically thick at sub-millimeter wavelength for free-free continuum. Millimeter to sub-millimeter SED analysis toward the central source S1 in a nearby type II AGN NGC 1068 was done, which gave an upper limit on the solid angle of BLR region as(4.94 +/- 0.61) *10^-6 arcsec^2, corresponding to a radius no more than 0.085 pc. Such a constraint on the BLR size is important for estimating the masses of central supermassive black holes in AGNs.
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All authors Qi Guo, Junzhi Wang, Lingrui Lin, Yuqiang Li, Zhi-yu Zhang, Fengyao Zhu
Solar and Stellar Astrophysics · Cross-listed from nucl-ex
$^{16}$O(p,$\gamma$)$^{17}$F Reaction and the C and O Isotopic Ratios in Red Giant Branch Stars
D. Robb, P. McGlynn, M. Aliotta et al. (+55 more)
The $^{16}$O/$^{17}$O isotopic ratio is a widely used tracer of nucleosynthesis and mixing processes in red giant
stars. Its value depends on the rates of the
proton-capture reactions responsible for the production and destruction of $^{16}$O and $^{17}$O among which the $^{16}$O(p,$\gamma$)$^{17}$F reaction plays a central role, as it involves both isotopes. This work reports on a new measurement of the $^{16}$O(p,$\gamma$)$^{17}$F cross section carried out at the Laboratory for Underground Nuclear Astrophysics (LUNA) over a center-of-mass energy range of 200 - 380 keV, a region previously unexplored by experimental studies. Two complementary techniques were employed:
prompt gamma-ray detection and activation. The results obtained with the two techniques are consistent within experimental uncertainties. From the measured cross sections and existing literature data, we evaluate a new thermonuclear reaction rate, which is then used to demonstrate how simultaneous measurements of stellar carbon and oxygen isotopic ratios constrain the initial mass and the extent of the mixing events in red giant branch
stars. In particular, we demonstrate how the $^{12}$C/$^{13}$C abundance ratio is primarily sensitive to the temperature T$_{\textrm{max}}$ attained during mixing, whereas the $^{16}$O/$^{17}$O abundance ratio is highly sensitive to the initial stellar mass M$_i$. Therefore, simultaneous measurements of these isotopic ratios can disentangle and place stringent constraints on M$_i$ and T$_{\textrm{max}}$, and the remaining uncertainty is now dominated by stellar abundance measurements rather than nuclear-physics inputs.
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All authors D. Robb, P. McGlynn, M. Aliotta, C. Ananna, F. Barile, L. Barbieri, D. Bemmerer, A. Best, R. Biasissi, A. Boeltzig, R. Bonnell, C. Broggini, C.G. Bruno, A. Caciolli, M. Campostrini, F. Casaburo, F. Cavanna, G.F. Ciani, T. Chillery, P. Colombetti, A. Compagnucci, P. Corvisiero, L. Csedreki, T. Davinson, R. Depalo, A. Di Leva, Z. Elekes, F. Ferraro, A. Formicola, Zs. Fülöp, G. Gervino, R. M. Gesuè, G. Gosta, Gy. Gyürky, A. Guglielmetti, C. Gustavino, C. Hebborn, G. Imbriani, M. Junker, M. Lugaro, J. Marsh, E. Masha, R. Menegazzo, D. Mercogliano, V. Paticchio, D. Piatti, P. Prati, D. Rapagnani, V. Rigato, M. Rossi, R. Sariyal, R.S. Sidhu, J. Skowronski, O. Straniero, T. Szücs, S. Turkat, M. Vagnoni, S. Zavatarelli
Cosmology and Nongalactic Astrophysics
Exact map-space beam convolution via spin-mapmaking
Camille Demay, Magdy Morshed, Martina Gerbino et al. (+1 more)
Forthcoming
cosmic microwave background (CMB) experiments are targeting ambitious science goals, including the exploration of the particle content of the Universe across
cosmic times and the search for the faint signal from primordial gravitational waves. To pursue these goals, CMB experiments will house an unprecedented high number of detectors that will dramatically enhance their sensitivity. This will in turn require a tight control of instrumental systematics, demanding efficient and precise simulation of systematic effects. Leveraging
spin-mapmaking, we present a map-based method to propagate beam convolution systematics to the map-level, especially well-suited for main-beam studies. From the scanning strategy information compressed into precomputed h-maps and the beam and sky harmonic coefficients, our method directly outputs beam convolved maps. We validate against pixel-centered TOD-level 4{\pi} convolution for circular, elliptical, and Planck HFI scanning beams, demonstrating that our method retains agreement to numerical precision, while operating in map space. This formalism enables efficient simulation of beam convolution systematics across the full focal plane of upcoming experiments. As a first practical application, we demonstrate the ability to efficiently produce beam-convolved simulated Planck maps, showing excellent agreement with the QuickPol pipeline at the power-spectrum level. We release a public code, Smarties4Planck, to easily generate such maps for broader use.
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All authors Camille Demay, Magdy Morshed, Martina Gerbino, Luca Pagano
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Biases in Ringdown Tests of General Relativity from Gravitational-Wave Microlensing
Sreelakshmi Mundakkal Dasan, Anuj Mishra and Apratim Ganguly
Gravitational-wave (GW) ringdown signals provide a powerful probe of the strong-field regime of general relativity (GR) through black hole spectroscopy and tests of the Kerr hypothesis. However, unmodeled propagation effects can bias the inference of remnant properties and the interpretation of ringdown features. We investigate the impact of gravitational
lensing on ringdown inference and tests of GR using GW150914-like simulated signals spanning the long-wavelength, wave-optics, and
geometric-optics regimes. We perform complementary time-domain post-merger and frequency-domain full inspiral–merger–ringdown analyses using unlensed waveform models. We find that
lensing in the wave-optics regime can produce substantial biases in the inferred remnant mass and
spin and can strongly affect the inferred modal content of the ringdown. In particular, it can spuriously favor the presence of the first overtone, with $\log_{10}\mathcal{B}^{221}_{220}\sim40$, even though the injected signal has no support for it. Parameterized ringdown tests can likewise yield strong apparent support for deviations from the Kerr quasinormal mode (QNM) spectrum, with $\log_{10}\mathcal{B}^{\rm modGR}_{\rm GR}\sim8$. In contrast, the evidence for higher-order modes remains largely unchanged for the simulated signals considered here. The parameterized analysis using the entire signal further shows that microlensing can bias the inferred frequency of the dominant $(2,2,0)$ QNM. These results demonstrate that unmodeled microlensing can produce systematic biases and spurious signatures in ringdown analyses, potentially affecting precision tests of the Kerr hypothesis.
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Solar and Stellar Astrophysics
Revisiting the Optical F-corona from the Artemis II Total Solar Eclipse with RAW Data: How Far Can Consumer JPEG Images Be Trusted for Astronomical Photometry?
Kohji Tsumura and Ko Arimatsu
We reanalyze the total solar eclipse images taken with a consumer camera during the Artemis II lunar flyby, using the RAW data as ground truth for our previous analysis of the released JPEG image. Calibrated with field
stars, the RAW data show that the lens vignetting and the variation of the pixel solid angle reduce the signal of diffuse light by up to $\sim$70% at the edge of the field, and that the signal on the dark side of the Moon is most likely foreground light rather than an instrumental offset. Between 10 degrees and 15 degrees elongation, the radial profiles of the F-corona follow power laws with indices of $-2.0$ to $-2.3$ (east), $-2.5$ (west), and $-2.4$ to $-2.7$ (north and south), consistent with space-based observations, and the surface brightness along the ecliptic is $\sim$26 MJy sr$^{-1}$ ($\pm 7\%$) at 10 degrees. The isophotes have flattening indices of $\sim$0.6-0.7 and superellipse indices of $\sim$1.5-1.6. Comparison with the ZodiSURF zodiacal light model supports a radial dust density index of $\alpha \simeq 1.3$ down to $\sim$0.2 au and suggests that the vertical distribution of the dust broadens toward the Sun. The JPEG image retains nearly the full vignetting, despite its metadata, and its tone response is not a single power law; together with the zero-point treatment, these effects account for the steep and asymmetric profiles reported previously, while the flattened morphology and $\alpha \simeq 1.3$ are confirmed. We identify quantities robust in JPEG images and show that the tone response can be reconstructed from field
stars.
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Cosmology and Nongalactic Astrophysics
Galaxy-to-galaxy stochasticity has a limited impact on reionization and the 21-cm signal at fixed mean emissivity
Shihai Zhu and Yuxiang Qin
Galaxy-to-
galaxy stochasticity may be less important for reionization, IGM heating, and the 21-cm signal than commonly assumed. We find that most of its apparent impact arises because introducing or removing scatter changes the mean emissivity of the
galaxy population, rather than from redistributing radiation at fixed mean emissivity. We use the Meraxes semi-analytic model to separate these effects. For ionising sources, we vary the scatter in the escape fraction and in the SFR-
halo mass relation across three source prescriptions. For the X-ray heating sources, we introduce luminosity scatter and also separately remove SFR scatter. Without recalibration, these modifications shift the mean emissivities, changing the timing of reionization and IGM heating and producing substantial differences in the 21-cm signal. Once the relevant mean emissivities are restored, however, the global ionizing and thermal histories converge and the power-spectrum differences fall below the forecast sensitivity of a deep SKA-Low observation. There are some weak changes in ionisation morphology, depending on which
galaxies dominate the ionising emissivity and on their response to photoheating. Within the models and scales considered here, calibrating the mean radiative emissivities is therefore substantially more important than resolving their
galaxy-to-
galaxy scatter.
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