Astrophysics of Galaxies
Inventories of Rich Carbon-Chain Chemistry in Prestellar and Starless Cores in the Perseus Molecular Cloud
Anissa Pokorny-Yadav, Samantha Scibelli, Judit Ferrer Asensio et al. (+3 more)
Carbon-chain molecules serve as an important reservoir of reactive organic matter that will eventually be incorporated into protoplanetary disks,
planets, and cometary material. Prestellar and starless cores are composed of cold (~ 10 K) and dense (~ 10$^5$ cm$^{-3}$) clumps of gas and
dust within molecular clouds, and are nurseries for low-mass
stars and planetary systems. Surveys of starless cores have focused on the study of complex organic molecules, COMs, whereas observations of carbon-chains in starless cores are limited. We analyze the carbon-chain inventories of 15 prestellar and starless cores in the Perseus Molecular Cloud. Using Yebes 40m single-dish observations, we detect CS, CCS, CCCS, HC$_3$N, DC$_3$N, and HC$_5$N in at least 10/15 cores and HC$_7$N in 4/15 cores. Our study also finds related isotopologues, where $^{13}$CS, C$^{34}$S, C$^{13}$CS, CC$^{34}$S, H$^{13}$CCCN, HC$^{13}$CCN, HCC$^{13}$CN, HC$^{13}$CCCCN, HCC$^{13}$CCCN, HCCC$^{13}$CCN, HCCCCC$^{15}$N, and DCCCCCN are detected. We report detection statistics, compare column density ratios with Taurus, Serpens, and protostar sources, examine DC$_3$N/HC$_3$N deuterium fractionation, and investigate the relative abundances and correlations between cyanopolyyne (HC$_n$N) and sulfur-bearing (C$_n$S) carbon-chains. The diverse suite of species detected reveals the richness of carbon-chain chemistry in Perseus and illustrates how local environmental conditions, such as density, temperature, and proximity to protostellar activity, shape each core's molecular inventory and relative evolutionary phase. Our findings provide a glimpse into the carbon-chain reservoir of starless and prestellar cores in Perseus, which may ultimately be inherited by emerging protoplanetary disks and later integrated into planetary systems and biologically relevant material.
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All authors Anissa Pokorny-Yadav, Samantha Scibelli, Judit Ferrer Asensio, Yancy Shirley, Andrés Megías, Izaskun Jiménez-Serra
Instrumentation and Methods for Astrophysics
Equivalence of mapping gravitational wave background anisotropy across bases at equal information content
Deepali Agarwal
Mapping anisotropies in the gravitational-wave background (GWB) requires choosing a basis to represent the sky intensity, such as pixel and spherical harmonic bases. Each introduces a truncation—e.g., a number of pixels or a maximum multipole l_max—often set by a naive counting argument that relate the number of measurable modes to the number of independent cross-correlations, N_pair, in a
pulsar timing array (PTA). However, such truncations can lead to reconstruction artefacts, as they do not reflect the true information content of the PTA response. Increasing the value of truncation parameters spans the observable space better but reveals poorly constrained modes, making the inverse problem ill-conditioned and requiring regularization. A natural approach is to restrict the reconstruction to a well-measured subspace via principal maps, defined by the dominant eigenmodes of the detector response (or Fisher)
matrix. However, these maps are not a fundamental parameterization of the sky, but rather, are derived from an underlying representation—such as a pixelization or a spherical harmonic expansion. While their explicit form depends on basis choice, they can span the same subspace when the underlying representation is sufficiently complete. Here, we show that reconstructed anisotropy maps via different bases are equivalent, provided they retain the same information content, i.e., span the same principal subspace. As illustrative cases, we consider a toy model for PTA configuration and several GWB anisotropy shapes: point source, an extended source with deterministic anisotropy, and a statistical isotropic background, along with its summary statistic—the angular power spectrum. Although the reconstructions are equivalent, their computational costs can differ. We conclude with brief comments on the construction of principal maps for ground-based interferometers.
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Instrumentation and Methods for Astrophysics
A waveguide spectrometer for high-resolution millimeter-wave imaging
Annie Tan, Patrick Ashworth, Peter S. Barry et al. (+6 more)
We present the design and development of a novel, compact integrated on-chip spectrometer operating at millimeter (mm) and submillimeter (sub-mm) wavelengths. The Superconducting Waveguide Integrated Submillimeter Spectrometer (SWISS) promises significant improvements in spectral resolution, optical efficiency, and frequency coverage over current mm-wave spectrometers by using a free-space rectangular waveguide architecture. Light is coupled in through the
antenna front end, which separates the two polarizations and passes them to the waveguide spectrometer through a contactless metamaterial transition. Each waveguide spectrometer consists of a feedline coupled to a series of filters based on single-pole cavity resonators with varying resonant frequencies. To maximize packing density, the filter banks are oriented out of the focal plane, and an E-plane bend in the output from the cavity filters enables a planar and scalable construction. The output of each filter is coupled to a kinetic inductance detector (KID) to enable high multiplexing factors. The spectrometer is fabricated using stacks of silicon wafers etched with a deep reactive-ion etch (DRIE) and metallized. In these proceedings, we discuss current development on a SWISS prototype including measurements on a prototype
antenna front end contactless transition and fabrication a prototype waveguide spectrometer.
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All authors Annie Tan, Patrick Ashworth, Peter S. Barry, Chris S. Benson, Karia Dibert, Harry Gordon-Moys, Peter Hunyor, Kirit S. Karkare, Izaak Morris
Instrumentation and Methods for Astrophysics
CCAT: Design and Characterization of the 350 GHz Instrument Module
Ben Keller, Jordan Wheeler, Cody J. Duell et al. (+23 more)
The CCAT Collaboration's
Prime-Cam instrument will soon be deployed to the Fred Young Submillimeter
Telescope (FYST) in Chile's Atacama Desert. Featuring prominently in
Prime-Cam's calibration and early science observations will be the 350 GHz instrument module, a broadband camera that will field more than 10,000 microwave kinetic inductance detectors (KIDs) across three detector arrays. Forecasts show this module will be capable of making the most sensitive to-date measurements of polarized
dust emission over a large fraction of the sky at this frequency, enabling new
galactic polarization science and improved understanding of cosmological foregrounds. In this work we discuss the design of the 350 GHz instrument module, covering aspects of the optics, readout, and detector arrays. We then report on the results of in-lab testing of the fully-integrated module, achieving stable cryogenic performance with a 100 mK focal plane, high detector yield, and a passband comparable to designed specifications. Upon completion of these tests, this module was shipped to the
telescope site in Chile for integration in
Prime-Cam.
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All authors Ben Keller, Jordan Wheeler, Cody J. Duell, Darshan A. Patel, Jason Austermann, Baird D. Bankovic, James Burgoyne, Scott Chapman, Steve K. Choi, Rodrigo Freundt, Min Gao, Eliza Gazda, Anthony I. Huber, Johannes Hubmayr, Lawrence T. Lin, Quintin Meyers, Paul Malachuk, Alicia Middleton, Michael D. Niemack, Tilak M. Patel, Anna Vaskuri, Eve Vavagiakis, Michael R. Vissers, Samantha Walker, Yuhan Wang, Ruixuan Xie
High Energy Astrophysical Phenomena
Constraining Lorentz invariance violation from the depth of air-shower maximum
Nickolay S. Martynenko, Grigory I. Rubtsov, Petr S. Satunin et al. (+2 more)
Hypothetical Lorentz invariance violation (LIV) remains strongly constrained but has not been excluded as a possible manifestation of new high-energy physics. In subluminal
photon-sector LIV, suppressed Bethe$\unicode{x2013}$Heitler pair production modifies the electromagnetic component of extensive air showers. We present a simulation-based toy analysis of this effect using published Pierre Auger fluorescence-detector distributions of the reconstructed depth of air-shower maximum. The modified distributions of the depth of the shower maximum are folded with the Auger detector-response parametrizations and compared with the data using free composition fractions in each reconstructed-energy bin. Within this approach, the comparison gives a sensitivity to LIV compatible with that expected from ultra-high-energy
photon-induced showers. We obtain $M_{\rm LIV}>1.5\times 10^{21}\,\text{GeV}$ ($95\%$ confidence level). This result should not be interpreted as a detector-level experimental limit because the detector response and reconstruction are simplified, and the result remains composition dependent. However, the approach presented here opens the way for constraining LIV in hadronic air showers with more detailed analyses.
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All authors Nickolay S. Martynenko, Grigory I. Rubtsov, Petr S. Satunin, Andrey K. Sharofeev, Sergey V. Troitsky
High Energy Astrophysical Phenomena
Dissecting the Nuclear Structure of NGC 5548 with XRISM. I. Physical Properties of the Highly Ionized Outflows
Missagh Mehdipour, Jon M. Miller, Jelle S. Kaastra et al. (+21 more)
We present a detailed spectral analysis of an X-Ray Imaging and Spectroscopy Mission (XRISM) observation of the prototypical Seyfert 1
galaxy NGC 5548. XRISM's Resolve microcalorimeter reveals, for the first time, highly ionized
outflows in this active
galactic nucleus (AGN) through the detection of Fe XXV and Fe XXVI absorption lines in the Fe K band. Modeling the XRISM/Resolve spectrum alongside XMM-Newton Reflection Grating Spectrometer (RGS) data allows us to probe the ionization and kinematic structure of the
outflows in this AGN. We identify four distinct ionization components, with ionization parameters log $\xi$ ranging from 0.9 to 3.4. Three of these components are further resolved into two velocity sub-components, demonstrating the multiphase structure of the
outflows. The measured
outflow velocities span 240 to 2730 km/s. We find a trend of increasing column density with ionization parameter ($\xi$), along with a general pattern of increasing
outflow velocity with $\xi$. The XRISM/Resolve spectrum provides a far more detailed absorption measure distribution (AMD) than was previously possible, revealing two distinct slopes above and below $\log\xi \sim 2.6$. A comparison of the Fe XXV absorption line profile with UV absorption lines (C IV and Ly$\alpha$) observed with the Hubble Space
Telescope reveals both overlaps and deviations. The XRISM/Resolve results suggest a multiphase, clumpy
outflow in NGC 5548, consistent with a "hybrid wind" scenario in which the observed parameter trends arise from multiple origins and driving mechanisms.
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All authors Missagh Mehdipour, Jon M. Miller, Jelle S. Kaastra, Gerard A. Kriss, Keigo Fukumura, Liyi Gu, Doyee Byun, Xin Xiang, Ehud Behar, Laura W. Brenneman, Elisa Costantini, Maryam Dehghanian, Jacobo Ebrero, Massimo Gaspari, Anna Juráňová, Erin Kara, Chen Li, Junjie Mao, Hirofumi Noda, Anna Ogorzalek, Ioanna Psaradaki, Daniele Rogantini, Sascha T. Zeegers, Keqin Zhao
Solar and Stellar Astrophysics
Spherically Polarized Alfvén Waves and the Gosling Boost
Yuliang Ding, Marco Velli, Zesen Huang et al. (+6 more)
Alfvén waves are thought to play critical roles in
solar wind acceleration and
plasma heating in the
solar corona and inner heliosphere. Parker
Solar Probe (PSP) has highlighted the role of large amplitude Spherically Polarized Alfvén Waves (SPAWs), where the locally constant
magnetic field magnitude $|\mathbf{B}|$ together with outward propagation explains the observed one sided radial velocity enhancement - the Gosling boost. Starting from the MHD equations, we derive the modified wave pressure and Poynting flux under the SPAW condition, and demonstrate both are governed solely by the transverse
magnetic fluctuations. Using PSP data from Encounters 6–25, we define an unperturbed velocity baseline from the lower 10th-percentile running average and statistically characterize the radial
evolution of Alfvénic fluctuations. The background
solar wind velocity shows clear radial acceleration, while the velocity perturbation amplitude $\delta v$ decreases with heliocentric distance. This decay is anisotropic between the radial and perpendicular directions, which is a direct consequence of the growing
magnetic deflection angle related to the spherical polarization. Our results demonstrate that radial velocity enhancements in the young
solar wind arise naturally from SPAWs rather than from localized velocity jets, and provide direct observational evidence for the anisotropic radial
evolution of SPAWs in the inner heliosphere.
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All authors Yuliang Ding, Marco Velli, Zesen Huang, Chen Shi, Lorenzo Matteini, Nikos Sioulas, Stuart D. Bale, Anna Tenerani, Mingzhe Liu
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Post-Inflationary Constraints on Nonminimally Coupled Quintessential Inflation
Min Gi Park, Seong Chan Park, Tomo Takahashi et al. (+1 more)
We investigate quintessential inflation in a nonminimally coupled scalar-tensor theory, parameterizing the post-inflationary radiation abundance independently of the reheating mechanism. The nonadiabatic inflation-kination transition generates a
stochastic gravitational-wave background whose contribution to $\Delta N_{\textrm{eff}}$ imposes a lower limit on the reheating temperature. Because this temperature dictates the duration of kination and the available scalar-field excursion, it directly constrains the present-day dark-energy equation of state. While a single-exponential coupling achieves the required post-inflationary potential drop, the same constant slope does not provide viable late-time acceleration. A double-exponential deformation resolves this tension by decoupling the average slope governing the total potential drop from the asymptotic slope driving
cosmic acceleration. Full numerical solutions confirm this picture, yielding a thawing quintessence regime with $w_{\varphi,0}\simeq (-0.90, -0.95)$ for our
benchmarks. Our results demonstrate that future dark-energy measurements can directly probe the post-inflationary reheating history of the Universe.
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All authors Min Gi Park, Seong Chan Park, Tomo Takahashi, José Jaime Terente Díaz
Instrumentation and Methods for Astrophysics
CCAT: Characterization of the first science-grade MKID array for the Prime-Cam 850 GHz module
Anthony I. Huber, Jordan Wheeler, James Burgoyne et al. (+15 more)
The Fred Young Submillimeter
Telescope (FYST) is a 6-meter crossed-Dragone
telescope developed by the CCAT collaboration. Sited at 5600 m on Cerro Chajnantor in the Atacama Plateau of Chile, FYST aims to provide superior atmospheric transmission and a wide field of view for submillimeter observations.
Prime-Cam is a first-generation instrument for FYST designed to house up to seven separate instrument modules. Among these, the 850 GHz module represents the highest-frequency band and is optimized for ultra-sensitive broadband polarimetry and imaging. This module is designed to deploy ~38,000 polarization-sensitive lumped-element titanium-nitride (TiN) microwave kinetic inductance detectors (MKIDs) across three arrays. Thus the 850 GHz module will have the most submillimeter MKIDs in a single instrument module to date. These detectors have adopted a novel two-octave design to maximize the multiplexing achieved using a RFSoC readout system. We review the design parameters and fabrication process for the first 850 GHz science-grade array. The preliminary measurements of the array show a fabrication yield of 99%, highlighting the successful application of the design and fabrication process. We further present the cryogenic characterization of the first full MKID array developed for the
Prime-Cam 850 GHz module. Multiple tests were performed on the devices including resonator frequency mapping, quality factor measurements, optical load sweeps and noise performance. From these measurements, we discuss the measured optical efficiency, sensitivity, and uniformity across the array and the expected on-sky performance of the module. The 850 GHz module will be deployed for observing in 2027.
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All authors Anthony I. Huber, Jordan Wheeler, James Burgoyne, Scott Chapman, Jason Austermann, James Beall, Steve K. Choi, Doug Henke, Johannes Hubmayr, Ben Keller, Matthew Koc, Jeff van Lanen, Tilak Patel, Adrian Sinclair, Anna Vaskuri, Eve M. Vavagiakis, Michael Vissers, Ruixuan Xie
Earth and Planetary Astrophysics
MarsCast: Transfer Learning of AI Weather Foundation Models to Planetary Atmospheres
M.L. Carroll, J. Li, S.D. Guzewich et al. (+3 more)
We investigate the transferability of Earth weather foundation models to planetary atmospheres by adapting the GraphCast graph neural weather
forecasting model to Mars. While GraphCast achieves state-of-the-art performance for terrestrial
forecasting, its applicability to non-Earth environments remains unexplored. Using the Mars
Climate Database (MCD), which provides global atmospheric fields across vertical altitude levels (similar to Earth pressure levels), we evaluate zero-shot and fine-tuned GraphCast predictions of Martian temperature and wind fields. Zero-shot forecasts produce a surprisingly accurate depiction of current conditions but fail to reproduce diurnal variability and rapidly decay toward climatological mean states. To address this limitation, we fine-tune GraphCast using MCD variables and top-of-atmosphere
solar radiation forcing while holding humidity constant. Fine-tuning enables rapid learning of Martian thermal variability. Within as few as 10 training epochs, the model begins to capture the diurnal cycle and forecasts up to 10 days reproduce seasonal and vertical temperature structure. Prediction quality improves with training sample size and exhibits sensitivity to seasonal initialization. These results demonstrate that Earth-trained AI weather models can be adapted to simulate Martian atmospheric dynamics, providing a pathway toward rapid planetary weather prediction to support mission operations,
dust storm risk mitigation, and future human exploration.
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All authors M.L. Carroll, J. Li, S.D. Guzewich, G.Villanueva, J.A. Caraballo-Vega, M.J. Frost
Cosmology and Nongalactic Astrophysics
Coupled quintessence from an axion dark sector
Rayff de Souza, Edmund J. Copeland and Jailson Alcaniz
Recent observational data arising from the DESI collaboration has hinted at a possible departure from the standard $\Lambda$CDM cosmological model, preferring instead the presence of a dynamical dark energy component. Specifically, the associated equation of state of the dark energy features a crossing into the so-called phantom regime, which is challenging to accommodate in canonical single scalar-field scenarios. However, this behavior can be effectively described by an interacting dark sector, where the specific dark energy equation of state remains above the phantom divide whilst the dark matter component deviates from the standard cold dark matter
evolution. In this work, we explore this possibility in the context of an
axion dark sector, where both the dark energy and dark matter are represented by two interacting
axion-like fields. We show that given the required mass hierarchy for these fields to play such roles, their dynamics can be effectively placed in the coupled quintessence framework, where their motion follows from a sourced continuity equation in the fluid description. In this regime, we perform a statistical analysis of this scenario with current data, finding that a sub-Planckian dark energy
axion decay constant stays well within the observational bounds without the need to fine-tune the associated field's initial conditions. We also perform a comparison with $\Lambda$CDM, where we find that the model provides a better fit to the data while staying competitive from a
Bayesian perspective.
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Solar and Stellar Astrophysics
Augmentation of the Gauribidanur radioheliograph for observations of circularly polarized emission from the solar corona at low radio frequencies
Sayuf Shaik, Kathiravan C, Gireesh G.V.S et al. (+4 more)
The
magnetic field strengths (B) in the
solar photosphere are routinely measured using the Zeeman effect. However, such measurements are not available in the
solar chromosphere and corona. The Gauribidanur RAdioheliograPH (GRAPH), near Bangalore in India, has been successfully carrying out total intensity (Stokes I) observations of the
solar corona at low frequencies ($\lesssim$ 100 MHz) for several years now.
Radio emission from the Sun in the above frequency range originates typically in the heliocentric distance r $\gtrsim$ 1.2 $R_\odot$ . We recently augmented GRAPH with the aim to observe circularly polarized
radio emission (Stokes V) from
solar corona, in particular, from the 'quiet' corona. Combining the low frequency Stokes I & V
radio images, and modeling techniques, it is possible to calculate the
magnetic field strengths in the
solar corona on regular basis. This work details the procedures undertaken to augment the GRAPH for simultaneous observations of both Stokes I & V
radio emission from the
solar corona, and the calibration procedure. Preliminary results indicate that the augmented GRAPH can effectively detect Stokes V emission associated with thermal emission from the 'quiet' Sun at frequencies $\lesssim$ 100 MHz, in addition to Stokes V emission associated with the non-thermal
radio bursts from the 'active' Sun.
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All authors Sayuf Shaik, Kathiravan C, Gireesh G.V.S, Indrajit V. Barve, Rajesh M, Shanmukha B, Ramesh R
Solar and Stellar Astrophysics
Binary evolution at the extremes of mass-transfer efficiency: Contact, mergers, and population signatures
Jan Henneco, Utkarsh R. Basu and Fabian R. N. Schneider
Binary
star evolution remains inherently uncertain, and several physical processes are not well understood. These open questions in binary physics come in addition to major uncertainties in single-
star evolution, such as angular momentum transport and interior mixing. For example, the efficiency of mass transfer (MT) – which is the fraction of transferred mass that is actually accreted – is one of the main uncertainties in binary
evolution. We present a grid of 1D binary
evolution models with identical initial conditions to an earlier grid in which MT was limited by the
spin-up of the accretors. Now we employ fully conservative MT, allowing for a one-to-one comparison between the two grids, and covering the full range from highly non-conservative to fully conservative MT. We explore how these two maximally different MT efficiencies change the occurrence and incidence of contact phases,
stellar mergers and common envelope phases, and how they affect the present-day population of (post-)mass-transferring binaries. We find that fully conservative MT increases the incidence of contact systems by roughly a factor of 6 (from 11% to 62%), and the
stellar merger incidence by more than a factor of 2 (from 16% to 38%). We also find the emergence of double-core CE phases, which are absent for lower MT efficiencies. Comparing two synthetic binary populations built using the two grids with observed Algol and stripped-
star binaries reveals that even though conservative MT is favoured to reproduce the observed stripped-
star binaries, the observed population of Algol binaries cannot be explained by a single MT efficiency. We conclude that the MT efficiency depends on the configuration of binary systems and cannot be described by a single value. Our work highlights the need for a better understanding of binary MT and indicates that current binary-
star models are incomplete.
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Astrophysics of Galaxies
The Roche-Lobe Radius in Newtonian and Non-Newtonian Gravity
A. M. Velasquez-Toribio
In this paper, we extend the standard calculation of the Roche lobe from the Newtonian potential to non-Newtonian models, specifically Yukawa-type and power-law potentials. These models are significant because they arise from unification theories, such as those involving extra dimensions or scalar-tensor
gravity. Furthermore, we develop fitting formulas for the equivalent volume radius R_L under these potentials, analogous to $Eggleton s$ formula for the Newtonian case. We calibrate the fitting formulas of the non-Newtonian potentials with their corresponding numerical solutions.
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Solar and Stellar Astrophysics
Tracing expansion-driven star formation in the Perseus molecular cloud using young stellar objects
Chen-Rui Gu, Zhi-Kai Zhu, Zu-Jia Lu et al. (+3 more)
$Context$. Recent studies have linked
star formation in the
solar neighbourhood to the expansion of the Local Bubble. The Per-Tau Shell (PTS), a vast 3D
dust structure hosting the Perseus and Taurus clouds on its surface, is a candidate for such triggered formation. $Aims$. We aim to reconstruct the
star formation history of the Perseus molecular cloud and investigate its potential link to the historical expansion of the PTS. $Methods$. We performed a 6D phase-space analysis of 406 young
stellar objects (YSOs) of Perseus. Our approach integrates
Gaia DR3 kinematics with
Bayesian age inference and a heteroscedastic likelihood framework to resolve radial gradients in YSO ages and intrinsic tangential velocity dispersions relative to the PTS centre. We constructed a unified catalogue by integrating existing infrared-based classifications to examine the projected spatial segregation of different evolutionary stages and compared
stellar 3D kinematics with $^{12}$CO and $^{13}$CO gas velocity fields to assess kinematic coherence. $Results$. The YSOs exhibit coherent outward motions relative to the centre of the PTS, a negative age-distance gradient with younger populations at larger radii, and a radial decline in tangential velocity dispersions. Younger YSO classes also show a stronger directional concentration towards the PTS centre. Both the coherent proper motions and the line-of-sight velocity gradients of these YSOs align with the gas velocity field, indicating large-scale kinematic coherence. $Conclusions$. The Perseus YSOs exhibit concordant kinematic and temporal signatures consistent with an expansion-driven origin. These results provide robust evidence for a layered, inside-out pattern of
star formation, suggesting that the historical expansion of the PTS triggered a sequential progression of
star birth and effectively shaped the
star formation history of the Perseus complex.
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All authors Chen-Rui Gu, Zhi-Kai Zhu, Zu-Jia Lu, Min Fang, Longhui Yang, Cheng-Yang He
High Energy Astrophysical Phenomena
Bayesian Inference of fine-features of dense matter EOS from future high-precision data of neutron star radii
Bao-An Li, Xavier Grundler, Wen-Jie Xie et al. (+1 more)
Future high-precision X-ray and gravitational wave observatories are expected to measure the radii of
neutron stars (NSs) with an accuracy better than about 0.1 km. However, it remains unclear what particular aspects of the Equation of State (EOS) and to what precision they will be better constrained. Within a
Bayesian framework using a meta-model EOS and mock high-precision NS data, the posterior probability distribution functions (PDFs) of NS matter EOS parameters for both hadronic and
quark phases and the transition between them were recently studied. We report here a few highlights of these studies.
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All authors Bao-An Li, Xavier Grundler, Wen-Jie Xie, Nai-Bo Zhang
High Energy Astrophysical Phenomena
X-ray Reflection as Diagnostic of Supermassive Black Hole Binary Properties
Julie Malewicz, Tamara Bogdanović, David R. Ballantyne et al. (+2 more)
We investigate correlations between prominent features in the relativistic X-ray reflection spectrum emitted by an accreting supermassive black hole (SMBH) binary with the underlying properties of the binary system. Model-independent measurements of the relativistic Fe K$\alpha$ line ($\sim$6.4 keV) and the Compton reflection hump ($\sim$20-30 keV) are shown to be useful in constraining binary parameters. We compute 24,570 X-ray reflection spectra from two mini-disks attached to SMBHs at a fixed separation of 100 $GM/c^2$ on circular orbits, by varying its mass ratio,
spin parameters, inclination, orbital phase and total mass
accretion rate. We find that the location of the blue peak in the relativistic Fe K$\alpha$ is a relatively robust diagnostic of the binary inclination, which could be obtained from a single-epoch X-ray spectrum. Given a few epochs of spectra, one may be able to determine the orbital phase of the binary and place constraints on its mass ratio by monitoring the Fe K$\alpha$ centroid. Of all parameters, SMBH
spin efects are most subtle and prone to measurement degeneracies. Some markers of high SMBH
spin may nevertheless surface in the composite spectrum due to increased radiative efficiency. The approach developed here can be used to place preliminary constraints on binary parameters before a full parametrized X-ray spectral fitting method is available. It complements gravitational wave measurements by the
Pulsar Timing Arrays (PTAs) and the
Laser Interferometer Space
Antenna by providing independent constraints on binary parameters that may be prone to degeneracy (inclination), or otherwise inaccessible (
spin for PTAs).
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All authors Julie Malewicz, Tamara Bogdanović, David R. Ballantyne, Laura Brenneman, Thomas Dauser
Solar and Stellar Astrophysics
3D simulations of a complete convective silicon shell burning phase
V. Varma, R. Hirschi, F. Rizzuti et al. (+7 more)
We present 3D hydrodynamic simulations of a complete silicon shell burning phase until fuel exhaustion at the end of the
evolution of a 14$M_\odot$ core-collapse
supernova progenitor, using a reduced 25-isotope
nuclear network. We investigate how realistic turbulent convection affects this burning phase, which has a more complicated set of
nuclear reactions than previous burning phases. We find broad similarities between the 3D simulation and the 1D MESA model. However, due to more realistic feedback from the very stiff convective boundaries in the hydrodynamic simulations, the 3D simulation experiences lower convective boundary mixing (CMB) compared to 1D, and hence entrains less fresh fuel into the silicon shell. This leads to the silicon shell in the 3D model burning for roughly 800\,s shorter. We find that the
nuclear burning timescales for the dominant reactions are faster than the mixing timescale, making this entire process a convective-reactive event. The angular-averaged energy generation profile shows a double-peaked structure, where the region between the positive peaks are close to zero, or are negative. We find that throughout the base of this silicon shell, many $(\alpha, p)$ and their inverse reactions are important. The forward and reverse rates are very similar, so slight fluctuations in the temperature cause regions to be either exoergic or endoergic, leading to a complicated energy generation
evolution. This study presents an exploration using a single reduced
nuclear network, however, due to the sensitivity of this burning phase future studies should investigate the impact of more complete
nuclear networks.
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All authors V. Varma, R. Hirschi, F. Rizzuti, T. Rauscher, A. St.J. Murphy, M. Mocák, C. Meakin, K. Goodman, C. Georgy, W.D. Arnett
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Evolution of matter perturbations in the context of cosmic slowing down
D. Koh Cuende and G. Panotopoulos
We investigate dynamical, time-evolving dark-energy models exhibiting phantom behaviour within Einstein
gravity by analysing the
evolution of matter perturbations. In particular, we consider five dark-energy parameterisations that predict a slowing down of the current
cosmic acceleration. We examine the
evolution of the growth index and its first derivative, as well as the combination parameter and the statefinder diagnostics, and compare their behaviour with that of the concordance $\Lambda$CDM model. For the parameter choices considered, the present-day values of the growth index and its first derivative are found to be compatible with ranges reported in previous phenomenological studies. The combination parameter is also found to differ from its $\Lambda$CDM value, while the statefinder parameters provide additional means of distinguishing the considered dynamical dark-energy scenarios from the concordance model. Our results illustrate the phenomenological signatures associated with these models and identify observables that may be useful for future observational tests. We stress, however, that the present analysis does not constitute a statistical model comparison or establish an observational preference for any of the considered dynamical dark-energy models over $\Lambda$CDM.
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Solar and Stellar Astrophysics
Properties of granular light bridges
Michal Sobotka, Jan Jurcak and Marta Garcia-Rivas
Granular light bridges in sunspots are a manifestation of magnetoconvection in an approximately vertical
magnetic field that is weaker than the field of the umbra. We study the relations between observed properties of granules and
magnetic field in five strong granular light bridges located in a complex sunspot. Thermal parameters,
magnetic field vector, and line-of-sight velocity were obtained from an inversion of the GREGOR spectropolarimetric scan in the lines Si I 1082.71 nm and Ca I 1083.90 nm. Sizes and lifetimes of granules were measured in a simultaneous sequence of images in the TiO band. The light bridges under study are comprised of granules spanning 0.2"-1.4" with approximately 6-minute lifetimes. The largest granular structures (> 1") are spatially correlated with 1 km/s upflows and weak, inclined
magnetic fields (300 G) near the equipartition threshold. Statistical comparisons demonstrate an inverse relationship between
magnetic field strength and continuum intensities, line-of-sight velocity dispersion, and effective granular diameters. These relationships vary among individual light bridges, depending on the large-scale
magnetic field
topology. Large expanding granules similar to the photospheric ones appear in light bridges only when the local
magnetic field strength approaches the equipartition value.
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Solar and Stellar Astrophysics
Asymmetry in the protostellar system HOPS 198: Evidence for the evolution of outflow opening angle driven by density of the surrounding core
Donglin Wu, Héctor Arce and Cheng-Han Hsieh
Protostellar
outflows are thought to be responsible for the low
star formation efficiency of protostellar cores. However, whether
outflows can disperse a significant fraction of the gas in the core depends on the
outflow opening angle. It is established that the
outflow opening angle increases during the early stages of the protostellar
evolution, but the underlying mechanism is poorly understood. Observations of HOPS 198, a Class 0 protostar in the Orion A molecular cloud, provide insights into this question. HOPS 198 exhibits a strong east-west asymmetry in its
outflow and its core. The opening angle of the eastern lobe ($\sim80^{\circ}$) is more than twice wider than that of the western lobe ($\sim30^{\circ}$), while the surface density of the west side of the core is $1.5-2.8$ times higher than the east side. Using an analytical model in which the molecular
outflow morphology is shaped by interactions between the wide-angle protostellar wind ($\gtrsim 80^{\circ}$) and surrounding material in the core, we find that the difference in opening angle for the two lobes can be explained by the difference in core density on the two sides. This result supports the hypothesis that the
evolution of the
outflow opening angle is driven by the
evolution in the density of the protostellar core.
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Cosmology and Nongalactic Astrophysics
Characterising the epoch of reionisation using the cross-correlation of the kSZ effect and CMB lensing
Niall MacCrann, Christopher Cain, Aleksandra Kusiak et al. (+5 more)
We investigate the cross-correlation of the kinematic Sunyaev-Zeldovich (kSZ) effect with
lensing of the
cosmic microwave background (CMB) as a probe of the epoch of reionisation. During reionisation, bubbles of ionised electrons form around overdensities, generating temperature perturbations in the CMB via the kSZ effect, which correlate with the projected matter density field probed by CMB
lensing. We demonstrate using AMBER simulations that this effect can be probed via cross-correlating the squared kSZ field with the CMB
lensing potential, and that the signal is sensitive to the duration and midpoint of reionisation. We forecast that for a Simons Observatory-like experiment with 5$\mu$K-arcmin white noise, covering 40% of the sky, the signal could be marginally detected at $S/N$ = 2 to 3. Meanwhile, a futuristic experiment like CMB-HD could provide a measurement of $S/N \sim 50$, yielding informative constraints on reionisation scenarios. We investigate potential challenges in measuring the signal and explore mitigation for each: contamination from extragalactic foregrounds at low
redshift, contamination of the kSZ-squared
estimator by
lensing, and other
estimator biases.
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All authors Niall MacCrann, Christopher Cain, Aleksandra Kusiak, Fiona McCarthy, Alexander Van Engelen, Darby Kramer, William R. Coulton, Frank J. Qu
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Ambiguity in matter sector for modified gravity involving $\delta^2 \mathcal{L}_{m}/\delta g^{\mu\nu}\delta g^{\alpha\beta}$ and its implications to astrophysics and cosmology
B. N. Jayawiguna and A. Sulaksono
Matter density ($\rho$) and radial pressure ($p$) are often used as the matter Lagrangian density ($\mathcal{L}_{m}$) because both are thermodynamically consistent and produce the same Einstein field equation (EFE) in general relativity (GR). New
gravity models with explicit links between matter and geometry instead involve second-order derivatives of $\mathcal{L}_{m}$ relative to the metric tensor. So, picking either $p$ or $-\rho$ for $\mathcal{L}_{m}$ gives different effective EFEs. This confusion appears because one usually treats the four-velocity ($u_\mu$) and the metric tensor ($g_{\mu \nu}$) as independent. Here, we revisit the basics and offer a consistent framework by relaxing that assumption, thereby making the modified
gravity theory independent of the choice of $\mathcal{L}_{m}$. Finally, we test this approach on
neutron and
quark stars (ultraviolet region) and on cosmological situations with radiation-dominated ($p=\rho/3$) equations of state (infrared region), showing how it clarifies the ambiguity in picking $\mathcal{L}_{m}$ for
gravity models.
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Instrumentation and Methods for Astrophysics
GBOT: ground based optical tracking of the Gaia satellite
Martin Altmann, Sebastien Bouquillon, Francois Taris et al. (+6 more)
Gaia, the 1 billion
star, high precision, astrometric satellite will revolutionise our understanding in many areas of astronomy ranging from bodies in our
Solar System to the formation and structure of our
Galaxy. To fully achieve the ambitious goals of the mission, and to completely eliminate effects such as aberration, we must know the position and velocity vectors of the spacecraft as it orbits the Lagrange point to an accuracy greater than can be obtained by traditional radar techniques, leading to the decision to conduct astrometric observations of the
Gaia satellite itself from the ground. Therefore the Ground Based Optical Tracking (GBOT) project was formed and a small worldwide network using 1-2 m
telescopes established in order to obtain one measurement per day of a precision/accuracy of 20 mas. We will discuss all aspects of GBOT, setup, feasibility considerations, preliminary tests of observing methods, partner observatories, the pipeline/database
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All authors Martin Altmann, Sebastien Bouquillon, Francois Taris, Iain A. Steele, Ricky L. Smart, Alexandre H. Andrei, Christophe Barache, Teddy Carlucci, Sebastian G. Elsa
Earth and Planetary Astrophysics
Circular polarization as a probe of cloud properties and asymmetries in giant exoplanet atmospheres
M. B. Michaelis and S. Wolf
For
planets in the
Solar System, circular polarization measurements complement linear polarimetry by providing additional information on cloud particle properties. As the disk-integrated circular polarization is 0 for symmetric
planets, observing intrinsic circular polarization of spatially unresolved
exoplanets requires stable spatial asymmetries such as circumplanetary rings. We investigated the potential of circular polarization measurements at optical and near-infrared wavelengths to determine optical properties of cloud particles in the atmospheres of
giant exoplanets and characterize asymmetries. For 20 selected cloud condensates spanning a wide range of refractive indices, we calculated optical properties using Mie scattering theory. The circular polarization of starlight scattered by cloudy
exoplanets was calculated with Monte Carlo radiative transfer simulations. To explain the connection between optical properties and planetary circular polarization, we derived an interpretative model of the first two scattering orders. Planetary hemispheres with atmospheres including cloud particles with a large imaginary part, $k$, of the refractive index show distinct circular polarization phase curves dominated by scattering first by gaseous molecules and then by cloud particles. The intrinsic degree of circular polarization, $P_\mathrm{c}$, is at most $3\cdot 10^{-4}$. When the cloud particles have a low $k$, they instead induce even smaller but more predictable circular polarization dominated by scattering solely by cloud particles. Circular polarization of starlight reflected by
giant exoplanets is sensitive to cloud particle composition and large-scale asymmetries but remains a subtle signal. While promising for characterizing clouds under favorable conditions, practical detection requires technological advances in polarimetry and careful disentanglement from
stellar background signals.
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Instrumentation and Methods for Astrophysics
Characterization of the MUSE NFM PSF as a function of atmospheric conditions: TipTop calibration
Enrico Congiu, Fuyan Bian, Carlo F. Manara et al. (+8 more)
The Multi Unit Spectroscopic Explorer (MUSE) achieves exceptional spatial resolution in narrow-field mode (NFM) thanks to the GALACSI adaptive optics (AO) system. However, limitations in point spread function (PSF) characterization still hinder the full exploitation of its capabilities. In particular, the current exposure time calculator (ETC) lacks an accurate PSF model, preventing users from reliably predicting the signal-to-noise ratio of NFM observations during proposal preparation. To address this limitation, we analyzed a large set of archival standard-
star observations to quantify how NFM PSF properties vary with observing conditions, including airmass, seeing, coherence time, wind speed, and wavelength. We then used this reference
dataset to calibrate TipTop, a fast AO PSF simulation tool that will be integrated into the next release of the MUSE NFM ETC. Our results demonstrate that calibration against real on-sky data is essential for accurate PSF modeling. In particular, we find that reproducing realistic PSFs requires both an additional static aberration term and an airmass-dependent tip-tilt jitter component. The calibration performs well at wavelengths longer than 7000 A, while additional corrections are still required at shorter wavelengths, likely due to unmodeled chromatic aberrations. Once implemented in the ETC, this tool will provide condition-dependent NFM PSF predictions and more reliable signal-to-noise estimates.
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All authors Enrico Congiu, Fuyan Bian, Carlo F. Manara, Arseniy Kuznetsov, Guido Agapito, Johanna Hartke, Timo Kravtsov, Lisa-Marie Mazzolo, Fabio Rossi, Cedric Plantet, Fernando Selman
Earth and Planetary Astrophysics
Spatial distribution of water ice in the protoplanetary silhouette disk d216-0939
J. S. Martin, S. Wolf, A. Potapov et al. (+4 more)
The composition of rocky
planets depends on the
dust in their natal protoplanetary disk (PPD), potentially containing water ice. Crystalline water ice was detected in the PPD d216-0939 in the Orion Nebular Cluster (ONC). We aim at constraining the spatial distribution and crystallization state of water ice in the d216-0939 disk using recent observations of the water ice absorption feature at a wavelength of $\sim 3\mathrm{\mu m}$ collected with JWST. We perform 3D Monte Carlo radiative transfer (MCRT) simulations to constrain the free parameters of an
accretion disk model by fitting the calculated spectrum in the wavelength range from $1.6 \text{ to } 24\mathrm{\mu m}$ to the spectral energy distribution (SED) observed with the JWST instruments NIRSpec and MIRI. Additionally, archival, spatially resolved HST observations were used to constrain the global spatial structure of the disk, as the parameter space is degenerate with respect to the fit to the SED. Successively, we fit the water ice absorption feature using polychromatic MCRT simulations with spectral importance sampling to produce synthetic observations at high spectral resolutions. By probing the upper and outer disk layers, we found that a PPD model with
dust containing 5.4% crystallized water ice beyond the snowline fits the observations well, necessitating outward transport of material, since crystalline ice is unlikely to form in situ in the probed disk layers. In the spectral region of the water ice absorption feature, scattering and thermal
dust emission both contribute significantly to the total flux.
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All authors J. S. Martin, S. Wolf, A. Potapov, H. Linz, Th. Henning, H. Terada, M. B. Michaelis
Astrophysics of Galaxies · Cross-listed from hep-ph
Isochrone fitting of Galactic globular clusters - IX. Tip of the red-giant branch for 27 clusters and constraints on new particle physics
G.A. Gontcharov, A.M. Kudashov, O.S. Ryutina et al. (+1 more)
Red-
giant evolution is sensitive to non-standard channels of energy loss in
stellar cores and therefore provides a probe of new physics. Such losses increase the luminosity of the tip of the red-
giant branch (TRGB), the brightest point reached by a red
giant in the color-magnitude diagram. Previous analyses of TRGB luminosities in globular clusters placed stringent bounds on the
axion-electron coupling g_ae, but were limited by observational and theoretical uncertainties. To obtain a homogeneous and systematically controlled constraint, we use new parameters and TRGB estimates for 27 globular clusters, derived from Stetson, Hubble Space
Telescope, and
Gaia photometry and cluster-specific MESA calculations. Our primary likelihood uses 24 clusters after excluding three hot-flasher systems and adopts the brightest non-variable or well-sampled variable red
giants. Finite sampling of the upper RGB is described by the full conditional distribution, and shared observational and
stellar-physics uncertainties are retained as correlated nuisance parameters. A 95% power-constrained profile-likelihood limit is g_ae<6.4e-14. The median TRGB bolometric absolute magnitude is -3.54+-0.05 mag. We briefly discuss the implications for the
neutrino magnetic dipole moment, millicharged particles, and other new physics.
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All authors G.A. Gontcharov, A.M. Kudashov, O.S. Ryutina, S.V. Troitsky
Astrophysics of Galaxies
Inflow-driven galaxy evolution - I. Revealing the physics of the fundamental metallicity relation
Kai Wang, Carlton Baugh, N. F. Boardman et al. (+11 more)
We present a unified physical framework for the fundamental
metallicity relation (FMR), based on the mass-continuity equations. The FMR is not merely the anti-correlation between
star formation rate (SFR) and gas
metallicity ($Z_{\rm g}$) at fixed
stellar mass ($M_\star$); it is a
redshift-invariant surface in the $(M_\star,{\rm SFR},Z_{\rm g})$ space. We construct a minimal cosmological gas flow model, calibrated to reproduce the mass-
metallicity relation,
star-forming main sequence, and
stellar-to-
halo mass relation at $z=0-3$, and show that the FMR emerges as a prediction of the calibrated physics. Through controlled experiments that progressively simplify the model, we reveal that in a universe where both the
star formation efficiency ($\epsilon$) and mass-loading factor ($\eta$) are constants, the FMR reduces to a universal scaling between $Z_{\rm g}$ and $M_\star/$SFR, whose shape traces the transition from inflow-driven regime to
equilibrium. The specific parameterisation of the observed FMR is not a fundamental
symmetry but a contingent consequence of how $\epsilon$ and $\eta$ depend on
stellar mass and
redshift. We show that the gaseous FMR (gFMR), defined in the $(M_\star,M_{\rm g},Z_{\rm g})$ space, is more fundamental than the standard FMR: in the inflow-driven limit, $Z_{\rm g}$ is proportional to $M_\star/M_{\rm g}$, and the approach to
equilibrium is governed by $M_\star/M_{\rm g}$ and $\eta$ alone. We derive an analytic solution for an idealised version of the model that provides closed-form expressions relating $Z_{\rm g}$, $M_{\rm g}/M_\star$, and $\eta$, and show this framework accurately reproduces the cosmological gas flow model. By establishing the physical origin of the FMR and its connection to the more fundamental gFMR, we provide the theoretical foundation to turn
metallicity scaling relations into precision probes of the
baryon cycle over
cosmic history.
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All authors Kai Wang, Carlton Baugh, N. F. Boardman, Sownak Bose, Zheng Cai, Shaun Cole, Carlos S. Frenk, Cedric Lacey, Peder Norberg, Yingjie Peng, Isabel Santos-Santos, Amélie Saintonge, Tom Theuns, Enci Wang
Solar and Stellar Astrophysics
Cepheid metallicities from low-resolution near-infrared spectra: validation against the optical reference scale
M. A. Urbaneja, R. P. Kudritzki and N. Przybilla
Classical Cepheid
metallicities trace recent chemical enrichment and help assess systematics in Cepheid-based distance measurements. They are derived mainly from high-resolution optical spectroscopy, which provides the
benchmark abundance scale but limits measurements to nearby systems. Extending such studies to more distant Cepheids with extremely large
telescopes requires complementary low-resolution near-infrared methods and careful treatment of model–data residuals. We test whether low-resolution SpeX/IRTF Y+J-band spectra can yield
metallicities compatible with homogenised optical abundances. We analyse 14
Galactic classical Cepheids with periods of approximately 13–69 d, supplemented by two shorter-period
stars from the IRTF Spectral Library. Using
Bayesian full-spectrum fitting based on MARCS/TURBOSPECTRUM spectra and a regularised covariance likelihood, we infer [M/H] and compare it with homogenised optical [Fe/H]. For the primary 14-
star sample, the inferred
metallicities reproduce the optical reference scale with a mean offset of -0.05 dex, a scatter of 0.09 dex, and a robust scatter of 0.12 dex; the median posterior uncertainty is 0.22 dex. Including the two additional
stars changes these values only slightly. Compared with a diagonal likelihood, the covariance-aware treatment reduces the mean offset and improves the stability of the uncertainty calibration. Low-resolution Y+J spectra therefore contain usable
metallicity information for classical Cepheids when short-range correlated residuals and localised modelling imperfections are treated explicitly. The resulting near-infrared
metallicity scale provides a practical foundation for extending Cepheid
metallicity work to larger and more distant samples.
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