Astrophysics of Galaxies
A Phenomenological Study of the Accretion Disk in the Super-Eddington AGN I Zw 1
Farin Drewes, Roberta Vieliute, Juan V. Hernández Santisteban et al. (+11 more)
The structure of the
accretion disk in AGN is still an unsolved question, especially how it may change with Eddington ratio. Here we examine the
accretion disk in the super-Eddington AGN I Zw 1 using reverberation mapping of the optical continuum. We use three years of optical monitoring with Las Cumbres Observatory at sub-day cadence in $uBgVriz_s$. The lag-wavelength spectrum, calculated using the cross correlation method and PyROA, shows a $u$-band excess. PyROA lags are equally well fitted with a thin and slim disk profile. The UV/optical AGN spectral energy distribution is consistent with a thin disk. The disk size at 4495 Å for a thin disk model is $4.23\pm0.24\:\mathrm{ld}$ and for a slim disk model is $1.71\pm0.09\:\mathrm{ld}$, larger by a factor of $2-4$ than the fiducial disk size of $1.07\pm0.15\:\mathrm{ld}$ as determined using the Eddington ratio. We find evidence of different size scales probed with different variability timescales. Lags evaluated at longer variability timescales increase as do frequency-resolved lags at low frequencies, which we interpret as an additional secondary reprocessor at large radii consistent with the broad-line region (BLR) in I Zw 1. The high frequency lags, predicted well with just a disk, are fit with a thin disk profile and a size of $0.61\pm0.37\:\mathrm{ld}$. This indicates that the actual disk size may be on the order of the fiducial size. We also collate the most extensive set of directly measured internal sizes of an AGN, from optical to mid-infrared with reverberation mapping and optical interferometry. Assuming that the disk is indeed the fiducial size, these show little evidence that the
accretion disk extends into the BLR significantly, tentatively disfavouring the failed radiatively accelerated
dust driven
outflow BLR formation model.
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All authors Farin Drewes, Roberta Vieliute, Juan V. Hernández Santisteban, Keith Horne, Aaron J. Barth, Edward M. Cackett, Encarni Romero Colmenero, Michael R. Goad, Shai Kaspi, Hermine Landt, Paulina Lira, Hagai Netzer, Marianne Vestergaard, Hartmut Winkler
High Energy Astrophysical Phenomena
A Minimalist Merger Interpretation of XRISM's Gas Velocity Measurements in the Coma Cluster
Congyao Zhang, Eugene Churazov, Ildar Khabibullin et al. (+3 more)
The recent microcalorimetric X-ray observations of the Coma cluster by XRISM have sparked active discussion regarding the physical origin of its gas velocity features. Here, we demonstrate that an off-axis minor merger in its early phase $-$ when the infalling subhalo is near its primary apocenter and the stripped tail is not yet mixed with the main cluster atmosphere $-$ can drive intracluster gas motions generally consistent with the XRISM results. These include a pronounced velocity gradient and an approximately uniform velocity dispersion of $\simeq100-200\,\rm{km\,s^{-1}}$ in the cluster core. Our merger scenario was originally suggested in Lyskova et al. (2019) to reproduce the major X-ray morphological features of Coma. In addition, we introduce a simple and robust diagnostic of intracluster gas motions based on the ratio of the line-of-sight velocity to the velocity dispersion.
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All authors Congyao Zhang, Eugene Churazov, Ildar Khabibullin, Natalya Lyskova, Norbert Werner, Irina Zhuravleva
Earth and Planetary Astrophysics
Two temperate Earth- and Neptune-sized planets orbiting fully convective M dwarfs
Madison G. Scott, Georgina Dransfield, Mathilde Timmermans et al. (+30 more)
As the diversity of
exoplanets continues to grow, it is important to revisit assumptions about habitability and classical HZ definitions. In this work, we introduce an expanded 'temperate' zone, defined by instellation fluxes between $0.1<S/\mathrm{S}_\oplus<5$, thus encompassing a broader range of potentially habitable worlds. We also introduce the TEMPOS survey, which aims to produce a catalogue of precise radii for temperate
planets orbiting M
dwarfs with $T_\mathrm{eff}\leq3400\,$ K. This work reports the discovery and characterisation of two
planets in this temperate regime orbiting mid-type M
dwarfs: TOI-6716\,b, a $0.98\pm0.07\,\mathrm{R}_\oplus$
planet orbiting its M4 host
star ($R_\star=0.231\,\pm0.015\mathrm{R}_\odot$, $M_\star=0.223\pm0.011\,\mathrm{M}_\odot$, $T_\mathrm{eff}=3110\pm80\,\mathrm{K}$) with a period $P=4.7185898^{+0.0000054}_{-0.0000041}\,\mathrm{d}$, and TOI-7384 b, a $3.56\pm0.21\,\mathrm{R}_\oplus$
planet orbiting an M4 ($R_\star=0.319\,\pm0.018\mathrm{R}_\odot$, $M_\star=0.318\pm0.016\,\mathrm{M}_\odot$, $T_\mathrm{eff}=3185\pm75\,\mathrm{K}$)
star every $P=6.2340258^{+0.0000034}_{-0.0000036}\,\mathrm{d}$. The radii of TOI-6716 b and TOI-7384 b have precisions of $6.8\%$ and $5.9\%$ respectively. We validate these
planets with multi-band ground-based photometric observations, high-resolution imaging and statistical analyses. We find these
planets to have instellation fluxes close to the inner (hotter) edge of the temperate zone, with $4.4\pm1.1\,\mathrm{S}_\oplus$ and $4.9\pm1.1\,\mathrm{S}_\oplus$ for TOI-6716 b and TOI-7384 b respectively. Also, with a predicted TSM similar to the TRAPPIST-1
planets, TOI-6716 b is likely to be a good rocky-world JWST target, should it have retained its atmosphere.
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All authors Madison G. Scott, Georgina Dransfield, Mathilde Timmermans, Amaury H.M.J. Triaud, Benjamin V. Rackham, Khalid Barkaoui, Adam J. Burgasser, Karen A. Collins, Michaël Gillon, Steve B. Howell, Alan M. Levine, Francisco J. Pozuelos, Keivan G. Stassun, Carl Ziegler, Yilen Gomez Maqueo Chew, Catherine A. Clark, Yasmin Davis, Fatemeh Davoudi, Tansu Daylan, Brice-Olivier Demory, Dax Feliz, Akihiko Fukui, Maximilian N. Günther, Emmanuël Jehin, Florian Lienhard, Andrew W. Mann, Clàudia Janó Muñoz, Norio Narita, Peter P. Pedersen, Richard P. Schwarz, Avi Shporer, Abderahmane Soubkiou, Sebastián Zúñiga-Fernández
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Towards Accurate Gravitational Wave Predictions: Gauge-Invariant Nucleation in the Electroweak Phase Transition
Jie Liu, Renhui Qin and Ligong Bian
The
vacuum decay in the early Universe should be gauge-invariant. In this work, we study the gauge dependence of the
vacuum decay occurring through a first-order phase transition and the associated gravitational wave production. We investigate the gauge dependence of the bubble nucleation and phase transition parameters within the framework of the Standard model effective field theory in three dimension. By considering the power-counting and utilizing the Nielsen identity at finite temperature, we show that, depending on the power-counting scheme favored by the new physics scale, the perturbative computation methodology allow we get the gauge-independent nucleation rates and phase transition, this enables more accurate predictions of gravitational wave signatures.
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High Energy Astrophysical Phenomena
Probing the morphology of the Gum Nebula through pulsar observables and a novel distance estimation method
Ashish Kumar, Avinash A. Deshpande and Pankaj Jain
Various existing models of the Gum Nebula differ significantly in their parameters and suggested origins, which can be independently tested for consistency with data on some key observables of
pulsars in the direction of the nebula. Our analysis of such data on the Vela
pulsar, assuming a dominant scattering region in its foreground, suggests that the fractional distance of the scatterer is $0.89 \pm 0.01$, and for the given distance of the Vela
pulsar, it translates to $254 \pm 16$ pc. Using independent distances of ten
pulsars, we suggest a refined description of the Gum Nebula electron density model with its basic morphology similar to that used in the YMW16 model, which now provides better estimates of
pulsar distances in these directions. In our new Gum Nebula model, as expected, the Vela
pulsar would be behind the frontal edge of the Gum shell, which was intriguingly located in front of the nebula in the YMW16 model. We also present a new technique to better constrain the
pulsar distances using their dispersion measure and temporal broadening simultaneously, and find that it is less affected by the uncertainties in the
Galactic electron density distribution models. Notably, the new approach shows that the expected temporal broadening as a function of trial distance does not follow a monotonic increasing trend, but instead exhibits oscillations at regions of enhanced electron density. This behaviour is expected, as the method employs the integral form of temporal broadening with the appropriate weighting kernel, leading to more reliable estimates.
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Solar and Stellar Astrophysics
A Catalog of 45,206 H{\alpha} Emission-line Stars from LAMOST MRS DR7
Lihuan Yu, Jiangdan Li, Jinliang Wang et al. (+2 more)
Stars that exhibit prominent emission lines in their spectra are referred to as emission-line
stars, encompassing a wide range of
stellar types and indicative of intriguing physical properties. The Large Sky Area Multi-Object fiber Spectroscopic
Telescope (LAMOST) has released millions of spectra from its Medium-Resolution Survey (MRS). A small fraction of these spectra exhibit emission lines, yet they remain undiscovered and unanalyzed due to being buried in the vast
dataset. We have developed a method based on Derivative Spectroscopy (DS), which provides a novel approach for detecting and identifying emission-line
stars by extracting signals from complex backgrounds and estimating spectral line profiles. Applying this method to the $\mathrm{H\alpha}$ spectral line profiles from the LAMOST-MRS Data Release 7 (DR7), we compiled a catalog of emission-line
stars using the second- and third-derivative spectra for automated peak detection. This approach also facilitates the classification of $\mathrm{H\alpha}$ emission-line morphologies through a simplified scheme. The catalog comprises 56\,649 spectra with relatively prominent $\mathrm{H\alpha}$ emission lines from 45\,206 unique
stars, with each emission-line component accompanied by approximate estimates of its wavelength, amplitude, and width. All $\mathrm{H\alpha}$ spectral lines were classified into three morphological classes under a unified classification scheme: single emission peak (83.0 %), double emission peaks (5.6 %), and P Cygni-type profiles (11.5 %), which encompass both P Cygni and inverse P Cygni features. Through cross-referencing with SIMBAD, 39\,497
stars represent new emission-line sources discovered in our research.
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All authors Lihuan Yu, Jiangdan Li, Jinliang Wang, Tongyu He, Zhanwen Han aa
Solar and Stellar Astrophysics
Fading into darkness: A weak mass ejection and low-efficiency fallback accompanying black hole formation in M31-2014-DS1
Kishalay De, Morgan MacLeod, Jacob E. Jencson et al. (+10 more)
Stellar-mass black holes (BHs) can form from the near-complete collapse of massive
stars, causing them to abruptly disappear. The
star M31-2014-DS1 in the Andromeda
galaxy was reported to exhibit such a disappearance between 2014 and 2022, with properties consistent with the failed explosion of a $\approx 12 - 13$ M$_\odot$ yellow supergiant leading to the formation of a $\approx 5$ M$_\odot$ BH. We present mid-infrared (MIR) observations of the remnant obtained with the James Webb Space
Telescope (JWST) and X-ray observations from the Chandra X-ray Observatory in 2024. The JWST MIRI/NIRSpec data reveal an extremely red source, showing strong blueshifted absorption from molecular gas (CO, CO$_2$, H$_2$O, SO$_2$) and deep silicate
dust features. Modeling the
dust continuum confirms continued bolometric fading of the central source to $\log(L/L_\odot)\approx3.88$ ($\approx7-8$% of the progenitor luminosity), surrounded by a
dust shell spanning $\approx40-200$ au. Modeling of the molecular gas indicates $\sim 0.1$ M$_\odot$ of gas expanding at $\approx 100$ km s$^{-1}$ near the inner edge of the
dust shell. No X-ray source is detected down to a luminosity limit of $L_X\lesssim1.5\times10^{35}$ erg s$^{-1}$. We show that the panchromatic observations are explained by (i) a low-energy ($\approx10^{46}$ erg) ejection of the outer H-rich progenitor envelope and (ii) a fading central BH powered by inefficient ($\sim0.1$% in mass)
accretion of loosely bound fallback material. The analysis robustly establishes the bolometric fading of M31-2014-DS1 and provides the first cohesive insights into BH formation via low-energy explosions and long-term fallback.
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All authors Kishalay De, Morgan MacLeod, Jacob E. Jencson, Ryan M. Lau, Andrea Antoni, María José Colmenares, Jane Huang, Megan Masterson, Viraj R. Karambelkar, Mansi M. Kasliwal, Abraham Loeb, Christos Panagiotou, Eliot Quataert
Solar and Stellar Astrophysics
Probing the CME Core–Prominence Relation Using Inner Coronal Observations
Sunit Sundar Pradhan, Jayant Joshi and Tanmoy Samanta
Coronal mass ejections (CMEs) often exhibit a three-part structure consisting of a bright inner core, an outer leading edge, and an intervening dark cavity. While the core has traditionally been attributed to prominence material, an alternative interpretation suggests it may arise from the projection effects of a twisted flux rope. We focused on limb CME events to reassess the connection between CME cores and their associated prominences in the inner corona. The CME cores were analyzed using white-light observations from the Mauna Loa
Solar Observatory (MLSO) K-Coronagraph (K-Cor), while the corresponding prominence eruptions were examined using H$\alpha$ data from the Global Oscillation Network Group (GONG) and 304 Å images from the Atmospheric Imaging Assembly (AIA). Our results show a strong spatial correspondence between H$\alpha$ prominences and CME cores in white light, with an average image correlation of $\sim$0.7, while correlations between white light and AIA 304 Å are comparatively weaker ($\sim$0.5). Several events could be continuously traced into the Large Angle and Spectrometric Coronagraph Experiment (LASCO/C2) field of view, confirming the persistence of prominence material into the outer corona. We find back-extrapolating LASCO/C2 CME cores under constant-velocity, linear-trajectory assumptions can introduce large errors – up to 40$^\circ$ in inferred position angle and $\sim$140 minutes in eruption time relative to their true values – underscoring the importance of inner-coronal observations for accurately constraining CME dynamics. Overall, our findings suggest that in prominence-associated CMEs, the bright cores are predominantly composed of prominence material.
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Astrophysics of Galaxies · Cross-listed from nlin.CD
Exploring Chaotic Motion of a Particle in the Centre of a Galaxy with a Prolate Halo
Uditi Nag, Yeasin Ali and Suparna Roychowdhury
The majority of
galaxies are known to have supermassive black holes (SMBHs) at their core, which have a tremendous gravitational pull on the objects around them. When embedded within extended matter distributions such as prolate, shell-like
halos, they give rise to complex gravitational fields that often drive nearby particles into chaotic orbits. The inherently nonlinear nature of such motion, shaped by general relativity, makes direct analysis highly challenging. To overcome this, pseudo-Newtonian potentials are used to approximate relativistic effects within a Newtonian framework. In this study, we model the central SMBH using the Artemova-Bjornsson-Novikov (1996) potential to mimic the rotational effects of a Kerr-like black hole. The surrounding prolate
halo is treated as an axisymmetric, shell-like mass distribution, represented through a multipole expansion including dipole and quadrupole components. Poincare sections and the Maximum Lyapunov Exponent (MLE) reveal how the SMBH-
halo system drives both order and chaos, with the SMBH
spin modulating the dynamics by enhancing or suppressing chaos depending on its direction and magnitude.
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Astrophysics of Galaxies
Methanol Formation via the Radical-radical Reaction of OH and CH3 Radicals Undergoing Transient Diffusion on Ice at 10 to 60 K
Arisa Iguchi, Hiroshi Hidaka, Atsuki Ishibashi et al. (+3 more)
Methanol (CH3OH) is thought to form on interstellar ice
dust via successive hydrogenation reactions. The reaction between CH3 and OH radicals could also conceivably generate methanol at temperatures above approximately 20 K, at which temperature hydrogen atoms will not adhere to the ice surface. However, this process has not been verified by well-controlled experiments. Using a newly-developed Cs+ ion pickup technique, the authors investigated the reaction between CH3 and OH radicals on the surface of amorphous solid water, an ice
dust analogue, at temperatures from 10 to 60 K. In the present experiments, OH radicals were generated by UV photolysis of water molecules, following which methane (CH4) gas was deposited on the ice substrate. The results show that CH3OH was formed on the ice surface through the sequential reactions CH4 + OH -> CH3 + H2O and CH3 + OH -> CH3OH even at 10 K. Considering the very low surface coverage of reactants in the experimental condition, the second reaction was found to occur as a result of transient
diffusion of CH3 due to the heat of the first reaction.
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All authors Arisa Iguchi, Hiroshi Hidaka, Atsuki Ishibashi, Masashi Tsuge, Yasuhiro Oba, Naoki Watanabe
Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Gravitational waves and small-field astrometry
Robin Geyer, Sven Zschocke, Michael Soffel et al. (+3 more)
Astrometric observations can, in principle, be used to detect gravitational waves. In this paper we give a practical overview of the gravitational wave effects which can be expected specifically in small-field astrometric data. Particular emphasis is placed on the differential effect between pairs of sources within a finite field of view. We also present several general findings that are not restricted to the small-field case. A detailed theoretical derivation of the general astrometric effect of a plane gravitational wave is provided. Numerical simulations, which underline our theoretical findings, are presented. We find that small-field missions suffer from significant detrimental properties, largely because their relatively small fields only allow the measurement of small differential effects which can be expected to be almost totally absorbed by standard plate calibrations.
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All authors Robin Geyer, Sven Zschocke, Michael Soffel, Sergei Klioner, Lennart Lindegren, Uwe Lammers
Astrophysics of Galaxies
Milliarcsecond-resolution Radio-imaging Survey of Blazar Candidates at 4 < z < 5.4
Máté Krezinger, Alessandro Caccianiga, Daniele Dallacasa et al. (+9 more)
We present a milliarcsecond-resolution
radio survey of 17 high-
redshift (4 < z < 5.4) blazar candidates observed with the European Very Long Baseline Interferometry (VLBI) Network at 5 GHz. The primary objective of this study was to investigate the nature of these distant active
galactic nuclei (AGN) and to confirm their blazar nature. Utilizing the technique of VLBI, we obtained high-resolution
radio images of compact core and core-jet structures. To confirm the classification of these sources, we collected multi-band archival data, including total
radio flux densities from single-dish and low-resolution interferometric surveys, optical astrometric positions from
Gaia, and X-ray data. These diagnostics collectively help distinguish between blazars and misaligned jetted AGN. We were able to measure the core brightness temperatures and found that 11 objects show the Doppler-boosted emission expected from blazars. For five additional sources, we do not see evidence of Doppler boosting even if X-ray data suggest that the source is a blazar. These could be either borderline objects or variability may have affected the classifications, considering that VLBI and X-ray data are not simultaneous. Finally, for the two remaining objects the data suggest a non-blazar classification. Our findings confirm that a significant fraction of these high-
redshift radio-loud
quasars are blazars and mainly characterized by compact core structures. Overall, the VLBI classifcations are consistent with the X-ray classes. This study further increases the sample of VLBI-imaged
radio quasars at z > 4 by ~10%, offering valuable on the population of AGN in the early Universe.
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All authors Máté Krezinger, Alessandro Caccianiga, Daniele Dallacasa, Luca Ighina, Sándor Frey, Alberto Moretti, Sonia Anton, Silvia Belladitta, Claudia Cicone, Krisztina É. Gabányi, M. J. M. Marcha, Krisztina Perger
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
A nonlinear voice from GW250114 ringdown
Yi-Fan Wang, Sizheng Ma, Neev Khera et al. (+2 more)
Gravitational-wave astronomy, by detecting ripples in spacetime, has opened a new window to observe compact objects and probe theories of
gravity in the nonlinear strong-field regime. The ringdown signal of a binary black hole merger contains a superposition of damped sinusoids known as quasi-normal modes (Ref.[1]), whose frequencies are completely determined by the mass and
spin of the remnant black hole and form the basis of black hole spectroscopy (Refs.[2-4]). A crucial prediction yet to be observationally confirmed is the existence of quadratic quasi-normal modes, which represent fundamental properties associated with wave-wave coupling in general relativity, and the leading mode is predicted to be detectable with next-generation ground-based detectors (Refs.[5-7]) using traditional methods. Here we show the first observational evidence for a set of quadratic quasi-normal modes in the ringdown of the binary black hole merger GW250114, the loudest gravitational-wave event detected to date, enabled by a novel analysis. These nonlinear modes result from the quadratic coupling of the linear $(2,2,n)$ modes with $n\leq3$. Starting the analysis at a time corresponding to four times the remnant mass ($M_\mathrm{f}$) after the merger, the evidence for their presence reaches a Bayes factor of 62. A phenomenological test allowing these modes to deviate from the theoretical prediction rejects the zero-amplitude hypothesis at a significance of 3.4 $\sigma$, while the inferred amplitude and complex frequency are consistent with the prediction of general relativity. This finding provides the first observational evidence of gravitational wave-wave interaction and extends black hole spectroscopy from the linear to the nonlinear regime. It also establishes a new direction for testing the fundamental nonlinear structure of general relativity with the most extreme
gravity.
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All authors Yi-Fan Wang, Sizheng Ma, Neev Khera, Junquan Su, Huan Yang
Solar and Stellar Astrophysics
The NuGrid AGB Evolution and Nucleosynthesis Data Set
Umberto Battino, Marco Pignatari, Ashley Tattersall et al. (+2 more)
Asymptotic
Giant Branch (AGB)
stars play a key role in the chemical
evolution of
galaxies. These
stars are the fundamental
stellar site for the production of light elements such as C, N and F, and half of the elements heavier than Fe via the slow
neutron capture process (s-process). Hence, detailed computational models of AGB
stars'
evolution and nucleosynthesis are essential for
galactic chemical
evolution. In this work, we discuss the progress in updating the NuGrid data set of AGB
stellar models and abundance yields. All
stellar models have been computed using the MESA
stellar evolution code, coupled with the post-processing mppnp code to calculate the full nucleosynthesis. The final data set will include the initial masses Mini/Msun = 1, 1.65, 2, 3, 4, 5, 6 and 7 for initial
metallicities Z = 0.0001, 0.001, 0.006, 0.01, 0.02 and 0.03. Observed s-process abundances on the surfaces of evolved
stars as well as the typical light elements in the composition of H-deficient post-AGB
stars are reproduced. A key short-term goal is to complete and expand the AGB
stars data set for the full
metallicity range. Chemical yield tables are provided for the available models.
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All authors Umberto Battino, Marco Pignatari, Ashley Tattersall, Pavel Denissenkov, Falk Herwig
Solar and Stellar Astrophysics
Energy Bounds from Relative Magnetic Helicity in Spherical Shells
Anthony R. Yeates and Gunnar Hornig
Relative
magnetic helicity is commonly used in
solar physics to avoid the well known gauge ambiguity of standard
magnetic helicity in magnetically open domains. But its physical interpretation is difficult owing to the invocation of a reference field. For the specific case of spherical shell domains (with potential reference field), relative helicity may be written intrinsically in terms of the
magnetic field alone, without the need to calculate the reference field or its vector potential. We use this intrinsic expression to prove that non-zero relative helicity implies lower bounds for both
magnetic energy and free
magnetic energy, generalizing the important Arnol'd inequality known for closed-field
magnetic helicity. Further, we derive a stronger energy bound by spatially decomposing the relative helicity over a
magnetic partition of the domain to obtain a new ideal invariant which we call unsigned helicity. The bounds are illustrated with analytical linear force-free fields (that maximize relative helicity for given boundary conditions) as well as a non-potential data-driven model of the
solar corona. These bounds confirm that both relative helicity and the unsigned helicity can influence the dynamics in the
solar corona.
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Solar and Stellar Astrophysics
Impact of newly measured 26Al(n, p)26Mg and 26Al(n, {\alpha})23Na reaction rates on the nucleosynthesis of 26Al in stars
Umberto Battino, Claudia Lederer-Woods, Marco Pignatari et al. (+6 more)
The
cosmic production of the short-lived radioactive nuclide 26Al is crucial for our understanding of the
evolution of
stars and
galaxies. However, simulations of the
stellar sites producing 26Al are still weakened by significant
nuclear uncertainties. We re-evaluate the 26Al(n, p)26Mg, and 26Al(n, {\alpha})23Na ground state reactivities from 0.01 GK to 10 GK, based on the recent n TOF measurement combined with theoretical predictions and a previous measurement at higher energies, and test their impact on
stellar nucleosynthesis. We computed the nucleosynthesis of low- and high-mass
stars using the Monash nucleosynthesis code, the NuGrid mppnp code, and the FUNS
stellar evolutionary code. Our low-mass
stellar models cover the 2-3 Msun mass range with
metallicities between Z = 0.01 and 0.02, their predicted 26Al/27Al ratios are compared to 62 meteoritic SiC grains. For high-mass
stars, we test our reactivities on two 15 Msun models with Z = 0.006 and 0.02. The new reactivities allow low-mass AGB
stars to reproduce the full range of 26Al/27Al ratios measured in SiC grains. The final 26Al abundance in high-mass
stars, at the point of highest production, varies by a factor of 2.4 when adopting the upper, or lower limit of our rates. However,
stellar uncertainties still play an important role in both mass regimes. The new reactivities visibly impact both low- and high-mass
stars nucleosynthesis and allow a general improvement in the comparison between stardust SiC grains and low-mass
star models. Concerning explosive nucleosynthesis, an improvement of the current uncertainties between T9~0.3 and 2.5 is needed for future studies.
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All authors Umberto Battino, Claudia Lederer-Woods, Marco Pignatari, Benjamin Soos, Maria Lugaro, Diego Vescovi, Sergio Cristallo, Philip J Woods, Amanda Karakas
Solar and Stellar Astrophysics
Impact of Newly Measured Nuclear Reaction Rates on $^{26}$Al Ejected Yields from Massive Stars
Umberto Battino, Lorenzo Roberti, Thomas V. Lawson et al. (+2 more)
Over the last three years, the rates of all the main
nuclear reactions involving the destruction and production of $^{26}$Al in
stars ($^{26}$Al(n, p)$^{26}$Mg, $^{26}$Al(n, $\alpha$)$^{23}$Na, $^{26}$Al(p, $\gamma$)$^{27}$Si and $^{25}$Mg(p, $\gamma$)$^{26}$Al) have been re-evaluated thanks to new high-precision experimental measurements of their cross sections at energies of astrophysical interest, considerably reducing the uncertainties in the
nuclear physics affecting their nucleosynthesis. We computed the nucleosynthetic yields ejected by the explosion of a high-mass
star (20 Msun, Z = 0.0134) using the FRANEC
stellar code, considering two explosion energies, 1.2 10$^{51}$ erg and 3 10$^{51}$ erg. We quantify the change in the ejected amount of $^{26}$Al and other key species that is predicted when the new rate selection is adopted instead of the reaction rates from the STARLIB
nuclear library. Additionally, the ratio of our ejected yields of 26Al to those of 14 other short-lived radionuclides (36Cl, 41Ca, 53Mn, 60Fe, 92Nb, 97Tc, 98Tc, 107Pd, 126Sn, 129I, 36Cs, 146Sm, 182Hf, 205Pb) are compared to early
solar system isotopic ratios, inferred from meteorite measurements. The total ejected 26Al yields vary by a factor of ~3 when adopting the new rates or the STARLIB rates. Additionally, the new
nuclear reaction rates also impact the predicted abundances of short-lived radionuclides in the early
solar system relative to $^{26}$Al. However, it is not possible to reproduce all the short-lived radionuclide isotopic ratios with our massive
star model alone, unless a second
stellar source could be invoked, which must have been active in polluting the pristine
solar nebula at a similar time of a core-collapse
supernova.
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All authors Umberto Battino, Lorenzo Roberti, Thomas V. Lawson, Alison M. Laird, Lewis Todd
Cosmology and Nongalactic Astrophysics
A microphysically inspired approach to dark matter-dark energy interactions: first bounds on dark-sector scattering cross sections
A.A. Escobal, F.B. Abdalla, J.F. Jesus et al. (+4 more)
The observational tension regarding the value of the Hubble constant ($H_0$) has motivated the exploration of alternative cosmological scenarios, including Interacting Dark Energy models. However, the majority of IDE models studied in the literature rely on phenomenological interaction terms proportional to the Hubble parameter (e.g., $Q\propto H\rho$), which lack a clear microphysical justification and often suffer from large-scale instabilities. In this work, we propose and investigate a "bottom-up" IDE model where the interaction is formulated directly from particle physics collision processes, taking the form $Q\propto\rho^2$. This interaction represents a reversible annihilation/creation process between Dark Matter and Dark Energy, motivated by the Boltzmann equation. We test this model against a combination of background cosmological data, Pantheon Plus,
Cosmic Chronometers, DESI DR2, and CMB distance priors from Planck18. We find that the model is consistent with the data, yielding a Hubble constant of $H_0=67.71\pm0.65$ km s$^{-1}$ Mpc$^{-1}$ for the combined analysis. The dimensionless interaction rate coefficients are constrained to be small, with upper limits of $A < 7.586\times10^{-25}$ (for Dark Matter self annihilation) and $B < 0.048$ (for Dark Energy self annihilation) at 95% confidence level. Since the interaction model is parameterized by the expansion rate, these bounds on $H_0$, $A$, and $B$ directly translate into a strict limit on the thermally-averaged annihilation cross-section per unit of mass. The constraints on the coupling $A$ imply that, if such a collisional interaction exists, the effective dark-matter annihilation cross section per unit mass is highly suppressed relative to the cosmological expansion rate. In contrast, the corresponding dark-energy contribution, governed by $B$, is only constrained at the level of a few percent in dimensionless units.
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All authors A.A. Escobal, F.B. Abdalla, J.F. Jesus, E. Abdalla, C. Feng, J. A. S. Lima, O. P. F. Piedra
High Energy Astrophysical Phenomena
Dust-obscured radio-emitting tidal disruption event coincident with a high-energy neutrino event
Tianyao Zhou, Xinwen Shu, Guobin Mou et al. (+14 more)
Despite the growing number of high-energy
neutrinos (TeV-PeV) detected by IceCube, their astrophysical origins remain largely unidentified. Recent observations have linked a few
tidal disruption events (TDEs) to the production of high-energy
neutrino emission, all of which display
dust-reprocessed infrared
flares, indicating a
dust- and gas-rich environment. By cross-matching the
neutrino events and a sample of mid-infrared outbursts in nearby
galaxies with transient
radio flares, we uncover an optically obscured TDE candidate, SDSS J151345.75 $+$ 311125.2, which shows both spatial and temporal coincidence with the sub-PeV
neutrino event IC170514B. Using a standard equipartition analysis of the synchrotron spectral
evolution spanning 605 days post mid-infrared discovery, we find a little
evolution in the
radio-emitting region, with a kinetic energy up to $10^{51}$ erg, depending on the
outflow geometry and shock acceleration efficiency assumed. High-resolution European VLBI Network imaging reveals a compact
radio emission that is unresolved at a scale of $<$ 2.1 pc, with a brightness temperature of $T_b>5\times10^6$ K, suggesting that the observed late-time
radio emission might originate from the interaction between a decelerating
outflow and a dense circumnuclear medium. If the association is genuine, the
neutrino production is possibly related to the acceleration of
protons through pp collisions during the
outflow expanding process, implying that the
outflow-cloud interaction could provide a physical site with a high-density environment for producing the sub-PeV
neutrinos. Such a scenario can be tested with future identifications of
radio transients coincident with high-energy
neutrinos.
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All authors Tianyao Zhou, Xinwen Shu, Guobin Mou, Lei Yang, Luming Sun, Fangkun Peng, Fabao Zhang, Hucheng Ding, Ning Jiang, Tinggui Wang, Yogesh Chandola, Daizhong Liu, Liming Dou, Yibo Wang, Jianguo Wang, Zhongzu Wu, Chenwei Yang
Instrumentation and Methods for Astrophysics
Data post-processing gain resulting from the patchy nature of speckles
Jean-Baptiste Ruffio and Laurent Pueyo
The data post-processing gain is an important parameter for exposure time calculations used to inform the design of the Habitable Worlds Observatory (HWO). Assuming azimuthally symmetric noise properties is a common simplifying assumption for such simulations, which neglects the patchy nature of the residual diffracted starlight; i.e., speckles. Fortunately, patchiness might prove to be an opportunity that improves the overall sensitivity of observatory assuming
photon-noise limited speckle subtraction. We illustrate this effect in the context of angular differential imaging (ADI), which is one of the possible observing strategies being considered for the detection and characterization of exo-Earth with HWO. We show that combining observations of two observatory roll angles leads to a gain in signal-to-noise greater than $\sqrt{2}$ when the patchy starlight dominates other noise sources. The gain can be closer to x2 when the starlight dominates the noise budget by more than an order of magnitude. In other words, combining good and bad observations is better than combining two average ones. This statement is very general as it is a direct consequence of combining data with a weighted mean. It applies more broadly to any combination of observations with varying noise level.
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Solar and Stellar Astrophysics
Analysis of Solar Flare and Sunspots on 4th Jan 2025 and Their Effects on Space Weather
Akash Vinod Shirke, Sakshi Sheshrao Charde and Balendra Pratap Singh
Solar flares and coronal mass ejections (CMEs) are among the most energetic phenomena in the
solar system, often impacting space weather and terrestrial technologies. In this study, we utilize SunPy, an open-source Python library for
solar physics, to analyze
solar active regions and their correlation with
flare and CME events observed on 4th January 2025. Data from GOES, SDO (AIA and HMI),
Solar Oribter (STIX), e-CALLISTO, Aditya L1 (SUIT), and SOHO are processed to track
flare intensity, active region
evolution, shock wave and CME dynamics. The analyzed
flare is identified as an X1.8-class event, and our study highlights key
magnetic precursors that led to it. This work enhances understanding of
solar eruption precursors and supports future predictive models for space weather
forecasting.
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Cosmology and Nongalactic Astrophysics
An intrinsic kinematic relation $\boldsymbol{c=\frac{c_{0}}{H_{0}}\,\dot{a}}\,$ inferred from Type Ia supernovae
Hoang Ky Nguyen
Based on the Hubble diagram of SNeIa, we present empirical evidence for a kinematic relation between the speed of light and the late-time
cosmic expansion rate. To infer this relation, we employ the Dolgov-Barrow cosmology, described by Dolgov's power-law expansion $a=(t/t_0)^\mu$ and Barrow's varying-speed-of-light (VSL) $c=c_0\,a^{-\zeta}$. In this cosmology, light propagating through an expanding
cosmic background undergoes an additional refraction induced by the variation of $c$ along its path, resulting in a modified Lemaître
redshift relation $1+z=a^{-(1+\zeta)}$. The model yields a high-quality fit to the Pantheon SNeIa Hubble diagram and exhibits a remarkably tight posterior degeneracy along the locus $(1+\zeta)\,\mu=1$. In particular, the case ${\mu=2/3,\zeta=1/2}$, referred to as the VSL-Einstein-de Sitter case, is favored over flat $\Lambda$CDM by $\Delta\chi^2=2.8$, i.e. at 68% confidence level, despite having the same number of free parameters. The empirical relation $(1+\zeta)\,\mu=1$ entails that the speed of light is exactly proportional to the
cosmic expansion rate, $c=c_0H_0^{-1}\,\dot a$, during late times, a synchronous behavior absent in the standard $\Lambda$CDM model. Although the empirical relation $(1+\zeta)\,\mu=1$ is inferred using the Dolgov-Barrow parameterization, the resulting expression $c=c_0H_0^{-1}\,\dot a$ is an intrinsic relation because it relates two physical quantities of the same dimension: speed of light and
cosmic expansion rate. It is therefore independent of arbitrary choices of units or parameterization and encodes a purely kinematic correspondence between $c$ and $\dot a$. If confirmed by independent probes, this relation may point toward a more general kinematic principle governing late-time
cosmic evolution. We discuss implications of this relation for late-time cosmology, including an alternative interpretation of
cosmic acceleration.
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Astrophysics of Galaxies
Backlighting young stellar objects in the Central Molecular Zone: an ensemble-averaged abundance structure of methanol ices
Yewon Kang, Deokkeun An, Jiwon Han et al. (+5 more)
The Central Molecular Zone (CMZ) contains a substantial reservoir of dense molecular gas, where numerous young
stellar objects (YSOs) and dense cloud cores have been identified. However, the large distance and severe foreground extinction complicate interpretation of infrared ice absorption features tracing chemical and evolutionary properties of these embedded objects. To better characterise YSOs and dense cores in this region, we combined spectra from multiple YSOs, each likely backlit by a
giant star, allowing us to probe their outer layers and derive an ensemble-averaged ice abundance profile. We obtained L-band spectra of 15 point-like sources with extremely red colours using Gemini/GNIRS, enabling measurements of the CH3OH absorption feature at 3.535 micron. To better constrain the foreground extinction and H$_2$O ice column densities, we combined these data with K-band and mid-infrared spectra using NASA/IRTF and Spitzer/IRS. We found that the CH$_3$OH abundance in the CH$_3$OH-CO$_2$ ice mixture is 2 to 5 percent, confirming that it is systematically lower than those typically observed in the
Galactic disk. Furthermore, by using the local excess of foreground extinction as a proxy for the projected distance between a backlit source and the centre of a YSO, we found that the CH$_3$OH abundance relative to solid CO$_2$ remains near 10 percent in the inner regions of the envelope, but increases sharply to about 30 percent in the outer regions. The relatively low methanol ice abundance may reflect the unique chemical environment of the CMZ. However, our results offer an alternative interpretation: since our sample is biased towards massive and luminous YSOs, intense heating from the central protostar may have caused substantial sublimation of methanol ice in the inner regions of their envelopes, thereby systematically lowering the observed CH$_3$OH/H$_2$O ice ratios.
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All authors Yewon Kang, Deokkeun An, Jiwon Han, Sang-Il Han, Dayoung Pyo, A. C. Adwin Boogert, Kee-Tae Kim, Do-Young Byun
Solar and Stellar Astrophysics · Cross-listed from gr-qc
Condensate Dark Stars beyond the Mean-Field Approximation: The Lee-Huang-Yang correction
Grigoris Panotopoulos
We study structural properties of self-gravitating fluid spheres made of a dilute, homogeneous and ultracold Bose gas assuming repulsive, short-range interactions. For the first time we include the Lee-Huang-Yang correction to the usual polytropic equation-of-state of index $n=1$, which goes beyond the Hartree mean-field approximation taking into account
quantum fluctuations. We find that the correction has a considerable impact on the M-R relationships and other properties of condensate dark
stars, such as factor of compactness and
tidal Love numbers. The impact is more significant for equation-of-states that support larger highest
stellar masses.
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Astrophysics of Galaxies
I can see your halo: Constraining the Milky Way halo DM with FRB population studies
Jordan Hoffmann, Clancy James, Jason Xavier Prochaska et al. (+1 more)
Fast
radio bursts (FRBs) probe the electron column density along the line of sight and hence can be used to probe foreground structures. One such structure is the
Galactic halo. In this work, we use a total of 98 high
Galactic latitude ($|b| > 20^\circ$) FRBs detected by ASKAP, Parkes, DSA and FAST with 32 associated
redshifts to constrain the dispersion measure (DM) contribution from the
Galactic halo. We simultaneously fit unknown FRB population parameters, which show correlations with the
Galactic halo but are not completely degenerate. We primarily use an isotropic model for the
halo, but find no evidence favouring a particular
halo model. We find DM$_{\rm MW,halo}$=$68^{+27}_{-24}$pc/cm$^3$, which is in agreement with other results within the literature. Previous constraints on DM$_{\rm MW,halo}$ with FRBs have used a few, low-DM FRBs. However, this is highly subject to fluctuations between different lines of sight, and hence using a larger number of sightlines as we do is more likely to be representative of the true average contribution. Nevertheless, we show that individual FRBs can still skew the data significantly and hence will be important in the future for more precise results.
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All authors Jordan Hoffmann, Clancy James, Jason Xavier Prochaska, Marcin Glowacki
Instrumentation and Methods for Astrophysics
A Large and Precise All-Sky Photometric Standard Star Dataset Across More Than 200 Passbands
Kai Xiao, Yang Huang, Haibo Yuan et al. (+12 more)
High-precision photometric standard
stars play a key role in enabling accurate photometric calibration and advancing various fields of astronomy. However, due to limitations in calibration methods and the limited availability and underuse of high-precision reference data, existing photometric standard
stars may suffer from insufficient numbers, systematic errors exceeding 10 milli-magnitude (mmag), limited photometric band coverage, or incomplete sky coverage, among other issues. To overcome these limitations, we have constructed the largest (over 200 million
stars, 1000 times the widely recognized Landolt standards in the same magnitude range), most precise (better than 10 mmag), and most comprehensive (over 200 bands, nearly 40 times the coverage of traditional standards) all-sky standard
stars. Based on standards, we have calibrated multiple survey
datasets to mmag precision, and subsequently developed a complete sky distribution of
stars for the Pan-STARRS system. This database, the BEst
STars Database (BEST), is expected to pave the way for achieving mmag-level - or even higher - photometric precision in large-scale surveys, and to play a central role in shaping a high-precision astronomical measurement framework.
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All authors Kai Xiao, Yang Huang, Haibo Yuan, Bowen Huang, Dongwei Fan, Timothy C. Beers, Zhirui Li, Henggeng Han, Qiqian Zhang, Tao Wang, Mingyang Ma, Yuanchang Wang, Shuai Xu, Lin Yang, Jifeng Liu
Earth and Planetary Astrophysics
Stellar control on atmospheric carbon chemistry, CO runaway, and organic synthesis on lifeless Earth-like planets
Yoshiaki Endo, Yasuto Watanabe and Kazumi Ozaki
The abundances of atmospheric carbon species–carbon dioxide (CO2), carbon monoxide (CO), and methane (CH4)–exert fundamental controls on the
climate, redox state, and prebiotic environment of terrestrial
planets. As
exoplanet atmospheric characterization advances, it is essential to understand how these species are regulated on habitable terrestrial
planets across a wide range of
stellar and planetary conditions. Here, we develop an integrated numerical model that couples atmospheric chemistry,
climate, and the long-term carbon cycle to investigate the atmospheric compositions of lifeless, Earth-like
planets orbiting Sun-like (F-, G-, and K-type)
stars. Our simulations demonstrate that CO2, CO, and CH4 generally increase with orbital distance, and that
planets near the outer edge of the habitable zone may undergo CO runaway–a photochemical instability driven by severe depletion of OH radicals. The threshold for CO runaway depends strongly on
stellar spectral type and is most easily triggered around cooler, lower-mass
stars. In contrast, the atmospheric production of formaldehyde (H2CO)–a key precursor for prebiotic organic chemistry–peaks around
planets orbiting more massive, UV-luminous
stars and is maximized at orbital distances just interior to the CO-runaway threshold. These results establish a quantitative framework linking observable system properties–
stellar type and orbital distance–and the atmospheric carbon chemistry of lifeless Earth-like
planets, providing new context for interpreting future spectroscopic observations and for evaluating the potential of such
planets to sustain prebiotic chemistry.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
Robust Bilinear-Noise-Optimal Control for Gravitational-Wave Detectors: A Mixed LQG/$H_\infty$ Approach
Ian A. O. MacMillan and Lee P. McCuller
At its lowest frequencies, LIGO is limited by noise in its many degrees of freedom of suspended optics, which, in turn, introduce noise in the interferometer through their feedback control systems. Nonlinear interactions are a dominant source of low-frequency noise, mixing noise from multiple degrees of freedom. The lowest-order form is bilinear noise, in which the noise from two feedback-controlled subsystems multiplies to mask gravitational waves. Bilinear couplings require control trade-offs that simultaneously balance high- and low-frequency noise. Currently, there is no known lower limit to bilinear control noise. Here, we develop
benchmark cost functions for bilinear noise and associated figures of merit. Linear-quadratic-Gaussian control then establishes aggressive feedback that saturates the lower bounds on the cost functions. We then develop a mixed LQG and $H_\infty$ approach to directly compute stable, robust, and optimal feedback, using the LIGO's
alignment control system as an example. Direct computations are fast while ensuring a global optimum. By calculating optimal robust control, it is possible to construct the lower bound on controls noise along the Pareto front of practical controllers for LIGO. This method can be used to drastically improve controls noise in existing observatories as well as to set subsystem control noise requirements for next-generation detectors with parameterized design.
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Solar and Stellar Astrophysics
Structural Tilting and Depth-Dependent Behavior of Equatorial Rossby Waves
Oana Vesa, Junwei Zhao and Ruizhu Chen
Over the past decade,
solar equatorial Rossby waves have been unambiguously identified and are considered potential diagnostics of
solar interior dynamics. We investigate their inclined structure and temporal
evolution in the
solar interior across multiple depths using approximately 14.5 yr of ring-diagram (RD) and time-distance (TD) helioseismology data from SDO/HMI. Normalized phase differences and cross power are computed from filtered spherical harmonic coefficients of radial vorticity to probe the structural tilt and power of Rossby waves. We find a systematic and robust depth-dependent phase behavior that shows no clear significant correlation with the
solar cycle, while the depth-dependent cross power exhibits a positive correlation with the
solar cycle for both
datasets. Our results show that deeper depths lead in phase over shallower ones, with increasing negative phases with depth. We infer that Rossby waves exhibit a retrograde tilt relative to the Sun's rotation that is stable throughout the
solar cycle. Analogous small tilts have been noted in planetary atmospheres and in magnetohydrodynamic simulations of the Sun, indicating that this behavior is not uncommon in rotating, stratified bodies and has implications for angular momentum and energy transport in the
solar interior.
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