Astrophysics of Galaxies
Temperature-programmed desorption of SO2 from water ice surfaces: Adsorption energy distributions
Ferdinand Benoit, Antoine B. Hacquard, Jean-Hugues Fillion et al. (+1 more)
Context. Sulphur-bearing species play a key role in the chemical
evolution of the interstellar medium and icy
Solar System bodies such as the Jovian moons, yet the sulphur budget remains poorly constrained. Sulphur dioxide is considered one of the main sulphur reservoirs in icy environments, making its interaction with water ice surfaces highly relevant for astrochemical models. Aims. This work aims to extract adsorption energy distributions of SO2 on water ice substrates as a relevant model for astrophysical environments to better constrain its thermal behaviour and solid-gas exchange for astrochemical simulations. Methods. We performed a systematic experimental study of temperature-programmed desorption of SO2 deposited on three types of surfaces – polycrystalline gold, compact amorphous solid water (c-ASW), and crystalline water under ultra-high
vacuum conditions – to then extract, using a Polanyi-Wigner model, the adsorption energy distributions of SO2 on each surface. Results. We performed the extraction of the adsorption energy distribution of SO2 deposited on water ice substrates. These exhibit a bimodal structure: a first physisorbed layer and a second, more strongly bound population. Only minor differences are observed between c-ASW and crystalline water ice in the behaviour of the distributions. We also provide mean values, most probable values, and width of the distribution. On average, the binding energy of SO2 on water ice surface is 439 +- 41 meV.
Read the full abstract ▾
All authors Ferdinand Benoit, Antoine B. Hacquard, Jean-Hugues Fillion, Mathieu Bertin
Solar and Stellar Astrophysics
The Gaia GSP-Spec catalogue of interstellar extinctions, and stellar luminosities, radii, and masses
Patrick de Laverny, Alejandra Recio-Blanco, Camila Navarrete et al. (+2 more)
The
Gaia/DR3 GSP-Spec module has published the atmospheric parameters of up to 5.6 million
stars based on the analysis of their Radial Velocity Spectrometer spectra. By combining these spectroscopic parameters with
Gaia parallax and photometric measurements, a large catalogue of interstellar colour excesses and extinctions, complemented with
stellar luminosities, radii, and masses, was constructed without relying on any
stellar evolution or structure models. This catalogue also contains the associated uncertainties estimated from Monte-Carlo realisations for about 4.6 million
stars. We present a system of quality flags based on the GSP-Spec quality parameters, the achieved numerical precision, and the
Gaia astrometric quality. Adopting these flags, we defined a subsample of high-accuracy and precision parameters of more than 1.5 million
stars. The impact of possible GSP-Spec parameter inaccuracies on the derived extinctions, luminosities, radii, and masses was also explored and revealed that the mass is the most affected quantity. The radii and masses were validated by comparison with interferometric and asteroseismic data. This confirmed their high quality, even when the targets were highly extincted by the interstellar medium. We also emphasise that they are fully compatible and homogeneous with the GSP-Spec parameters. This allowed us to avoid systematics and biases that might be hidden when data from different (and potentially) heterogeneous catalogues are combined. Finally, we present some example applications of this catalogue: (i)
exoplanet radii and masses, (ii) present-day mass distribution functions, (iii) identification of
Galactic populations based on their mass distribution, and (iv)
Galactic halo accreted
stellar luminosities and masses that confirm their merger epochs
Read the full abstract ▾
All authors Patrick de Laverny, Alejandra Recio-Blanco, Camila Navarrete, Pedro A. Palicio, Emanuele Spitoni
High Energy Astrophysical Phenomena
Simulation based parameter space for shock in transonic, sub-Keplerian accretion flow onto non-rotating black holes
Aishi Dasadhikary and Sudip K Garain
Non-dissipative, transonic, sub-Keplerian
accretion flow onto black holes is characterized by two conserved parameters: specific energy and specific angular momentum of the flow. For certain range of these parameters, the
accretion flow shows shock formation and the post-shock matter forms a boundary layer which is believed to shape the radiative properties of the
accretion disk. In this work, we identify the parameter space for shock in such
accretion flows using multi-dimensional numerical simulations around non-rotating black holes and demonstrate that the shock formation parameter space is much larger than the analytically calculated one. We also find the boundary layer to be dynamic for a significant part of this parameter space and self-consistently produce
outflow from the
accretion disk.
Read the full abstract ▾
Astrophysics of Galaxies
The UV Side of Little Red Dots: Red, Compact, and Iron-Enhanced Rest-UV Emission with a Strong Downturn around Ly$\alpha$
Makoto Ando, Yuichi Harikane, Harley Katz et al. (+2 more)
Little Red Dots (LRDs) are candidates for growing supermassive black holes newly discovered by the James Webb Space
Telescope (JWST), characterized by compact rest-optical morphology, V-shaped spectra, and broad Hydrogen Balmer lines. While recently proposed BH-
star/envelope models have made progress in explaining their optical features, their rest-UV emission, which is considered to originate from host
galaxies, remains poorly investigated. In this paper, we present a comprehensive analysis of the UV emission, including continuum shapes, emission line strengths, and morphology, using $\sim100$ LRDs selected from the JWST spectral archive. Compared to
star-forming
galaxies at the same
redshifts and UV magnitudes, LRDs show systematically redder UV slopes and more compact UV sizes, indicating that their UV emission cannot be explained solely by normal
star-forming
galaxies and requires a significant contribution from central red and compact emission. From stacked spectra, we find that the Balmer break strength, UV slope, downturn depth around Ly$\alpha$, and $\mathrm{Fe\, II}$ equivalent width are positively correlated, while the UV size is anticorrelated with the Balmer break strength, suggesting that diversity in the UV continuum shape reflects the varying dominance of the central emission relative to its host. We also measure $\mathrm{Fe\, II//Mg\, II}\sim8-10$, higher than in
quasars at similar
redshifts, further supporting a substantial contribution from the central component. Spectral modeling suggests that the observed red UV continuum cannot be reproduced by host
galaxy emission alone, but requires an additional very red continuum source ($\beta_\mathrm{UV}\sim0$), possibly nebular continuum emission leaking from dense ionized gas through a clumpy or porous neutral gas envelope.
Read the full abstract ▾
All authors Makoto Ando, Yuichi Harikane, Harley Katz, Kohei Inayoshi, Takumi S. Tanaka
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Probing Inelastic Dark Matter via Cosmic-Ray Upscattering in NGC 1068
Eung Jin Chun, Sanjoy Mandal and Abhishek Roy
We study constraints on sub-GeV inelastic dark matter (iDM) from
cosmic-ray (CR) cooling in the active
galactic nucleus (AGN) NGC 1068. In dense dark matter (DM) spikes surrounding supermassive black holes, high-energy CR
protons can efficiently lose energy through scatterings with dark matter particles. We consider a minimal vector-portal iDM framework and consistently include both elastic and deep inelastic scattering (DIS) contributions to the CR energy-loss rate. We find that DIS processes dominate at high momentum transfer and substantially enhance the DM-induced cooling effect. By requiring the resulting cooling timescale to remain compatible with the observed Standard Model cooling in NGC 1068, we derive constraints on the iDM parameter space. Our results demonstrate that AGN
cosmic-ray cooling probes previously unexplored regions of sub-GeV iDM parameter space inaccessible to current direct-detection experiments.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Signatures of Ultralight Dark Matter in Space-Based Laser Interferometers
Tingyuan Jiang and Yong Tang
Ultralight dark matter (ULDM) coupled to the Standard Model may effectively induce coherent oscillations of fundamental constants and thereby generate narrow-band signals in precision interferometric experiments. Here we present a systematic study of how these oscillations leave distinctive imprints on space-based
laser interferometers, including LISA and Taiji. Starting from the one-way inter-spacecraft link observables, we analyze several instrument-level effects induced by ULDM, including composition-dependent acceleration of test masses,
laser-frequency variations associated with cavity-length modulation, refractive-index effects, and clock-related contributions. We then propagate these signals through the standard data processing chain, including time-delay interferometry and clock-noise elimination. We show that the observability of an ULDM-induced effect is determined by the structure of its single-link response. In particular, the ULDM-driven variation in
laser frequency appears in the raw link observable with the same form as
laser phase noise. As a consequence, it is strongly suppressed in the final interferometry channels. In contrast, signals that possess an explicit directional pattern are not eliminated by this procedure, such as the ULDM-induced oscillations of the test masses. We further construct a local observable that isolates the differential motion between the test mass and the optical bench, and derive its sensitivity to both the dilaton–
gluon coupling $d_g$ and the dilaton–electron coupling $d_e$ for LISA, Taiji, and BBO. We find that the local observable yields sensitivities comparable to the standard Michelson interferometer for $d_g$, but better than Michelson channel by three orders of magnitude for $d_e$.
Read the full abstract ▾
Earth and Planetary Astrophysics
A comprehensive Rossiter-Mclaughlin Modelling Framework in TLCM: Application to HD 2685 $=$ TOI-135 system
Szilárd Csizmadia, Alexis M. S. Smith, J. V. Harre et al. (+1 more)
We present an updated Rossiter-McLaughlin modelling framework in the
exoplanet analysis code TLCM. We describe our model in detail. The model and the code were validated by nine systems where we use TESS photometric measurements and archive radial velocity data (WASP-15, HAT-P-1, HAT-P-3, HAT-P-6, HAT-P-7, HAT-P-11, HAT-P-14, HAT-P-20, HAT-P-32). In addition, new observations were obtained from HD 2685 = TOI-135 which is an evolved, hot ($T_\mathrm{eff}=6801$ K), single
star hosting a $\sim 1.15$ Jupiter-mass transiting hot Jupiter in a $\sim 4.1$ days orbit. We obtained new HARPS radial velocity measurements in-transit and out-of-transit. Also, there are new photometric observations from six additional, yet not-analyzed TESS-sectors since the time of the discovery of its transits. This allowed us to refine the planetary, orbital and system parameters and to detect Rossiter-Mclaughlin effect in it. We find an intermediate sky-projected obliquity, $\lambda = \ang{55.6}^{+\ang{10.9}}_{-\ang{11.9}}$, for our fiducial spectroscopic \(V\sin I_\star\) prior. Tests with broader \(V\sin I_\star\) priors show that the central value of \(\lambda\) remains stable, although the uncertainty increases.
Read the full abstract ▾
All authors Szilárd Csizmadia, Alexis M. S. Smith, J. V. Harre, Gábor G. Balázs
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Gravitino Freeze-In Dark Matter with an Additional Scalar Field
Georgios Georgilas and Vassilis C. Spanos
The gravitino is a prominent example of a freeze-in dark matter candidate. Its relic abundance depends on the reheating temperature and on supersymmetry-breaking parameters, that is the universal gaugino mass, $M_{1/2}$, and the gravitino mass, $m_{3/2}$. As a consequence, the reheating temperature consistent with the observed dark matter abundance exhibits a maximum value, $T_{\rm reh}^{\rm reak}$, which decreases as $M_{1/2}$ increases. This behavior gives rise to a tension between prospective lower bounds on the gluino mass from future
collider searches and the high reheating temperatures required for successful thermal leptogenesis. In this work, we investigate a nonstandard cosmological scenario in which the thermal bath is supplemented by an additional scalar field. We show that, for a matter-like equation of state, this component can induce a substantial dilution of the gravitino abundance, thereby allowing significantly larger values of the reheating temperature. In contrast, for a kination-like equation of state, the gravitino abundance is enhanced rather than diluted, leading to a reduction of the maximum allowed reheating temperature.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Hidden-sector accretion and warped black-string seeds for high-redshift supermassive black holes
Chunshan Lin
The earliest massive black holes are often discussed in terms of heavy baryonic seeds,
primordial black holes, or super-Eddington
accretion. We develop a different possibility: a compact object on a hidden donor brane forms a common five-dimensional horizon whose intersection with our brane is observed as a black-hole seed. Donor-side matter accretes onto the common five-dimensional horizon, increases the horizon radius, and consequently enlarges its intersection with our brane. As a result, the gravitational mass inferred by an observer living on our brane grows. We slice the five-dimensional geometry onto each brane and show that the induced exterior on our brane has the usual Schwarzschild/Vaidya monopole form at leading order, with subleading Weyl/Kaluza-Klein corrections in the localized-feeding branch. We construct a perturbative gradient-expansion solution satisfying the regular bulk equations and brane junction conditions. The matter sector satisfies the null energy condition for positive mass growth. The linear perturbation stability is investigated, and for supermassive seeds with horizon radius far larger than the interbrane scale, the dangerous long-wavelength mode is absent. The primary observational consequences are overmassive high-
redshift black holes in underdeveloped hosts, hidden mass growth relative to the luminous
accretion budget, LISA-band heavy-seed mergers, and the absence of
primordial fossils required by
primordial-black-hole explanations.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Self-interacting neutrinos in cosmological perturbation theory – integrating the collision kernel
Jakob K. Mogensen, Steen Hannestad and Thomas Tram
Cosmological constraints on self-interacting
neutrinos require a Boltzmann hierarchy in which the collision term is projected onto momentum-averaged multipoles. We revisit the collision kernel for
neutrino-
neutrino scattering mediated by a light scalar and derive an exact analytic expression for the multipole integral that determines the coefficients $\alpha_\ell$. The key idea is to express the integration kernel as angular derivatives of the Yukawa-potential $\frac{\mathrm{e}^{-P/2}}{P}$, move the derivatives onto Legendre
polynomials, and reduce the remaining momentum integrals to a single base family obeying a first-order recurrence. This gives an exact rational-plus-$\pi^2$ representation for every multipole, together with a compact implementation based on exact rational arithmetic. We provide the recurrence relations, a closed form for the base integral, and an asymptotically constrained approximation suitable for Boltzmann codes such as CLASS. Our numerical implementation is publicly available in the Jupyter notebook IntegralComputation.ipynb.
Read the full abstract ▾
Astrophysics of Galaxies
Little Red Dot progenitors from Compact Starbursts: A Natural Path to Early AGN Formation
Matías Liempi, Muhammad A. Latif and Dominik R.G. Schleicher
The recent discovery of Little Red Dots (LRDs) by the James Webb Space
Telescope has challenged traditional models of early
galaxy and black hole co-
evolution. The nature of these highly compact objects remains heavily debated, with explanations divided between
dust-reddened active
galactic nuclei (AGN) and extremely dense
stellar populations. We perform high-resolution cosmological simulations to model the formation of LRD precursors. Motivated by recent high-
redshift observations and theoretical results, we specifically explore environments characterized by high
star formation efficiencies (30% and 100%) and confined feedback. Our simulations naturally produce highly compact
galaxies with
stellar masses of $10^7-6 \times 10^8 $\,M$_\odot$, with most of the mass concentrated within $200-300$ pc. We find that, in these dense environments, gas inflows, gravitational torques, and
stellar dynamical friction operate on highly efficient timescales. Over a 10 Myr timescale, gas inflows can accumulate $\rm \sim 10^7 M_\odot$ at the
galactic center, while gravitational torques and dynamical friction can contribute an additional $10^5-10^9$\,M$_\odot$ and $10^3-10^4$\, M$_\odot$ through the inward migration of massive
stars. Assuming a conservative 10% efficiency to account for feedback, this rapid mass accumulation can lead to the formation of a $\sim 10^6$\,M$_\odot$ central black hole, naturally giving rise to an AGN in these dense systems. Therefore,
stellar and AGN interpretations of LRDs may not be mutually exclusive; rather, dense
stellar systems are likely precursors to AGN.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Model-Independent Search Discards Faint Lensed-Pairs of Gravitational Wave Events in the Sub-Threshold Candidates of GWTC-4
Aniruddha Chakraborty and Suvodip Mukherjee
Gravitational
lensing of gravitational waves (GWs) can produce multiple images in the
geometric optics limit. These lensed GW images arrive at different times, are amplified by different magnification factors, and are shifted by constant phases. With current understanding, the occurrence of lensed events stands at a few per thousand events, and the number of GW detections is a few hundred with the ground-based detector network. However, with the inclusion of the sub-threshold events, the total number of detections crosses a few thousand. Therefore, a search that includes both types of events yields a higher chance of
lensing detection. In this work, we carry out the first model-independent
lensing search using a cross-correlation-based technique GLANCE over the entire volume of the GWTC-4 strain data, containing $\sim 90$ super-events $\sim 800$ sub-events forming a total of $\sim 11,000$ event pairs with a higher False Alarm Rate (FAR) event rate allowing to search deep in the noise dominated regime. We further conduct their spectrogram checks to inspect data quality, sky-map overlap of the interesting pairs, and a
Bayesian parameter exploration of the sub-event to make a robust
lensing detection. Although the search indicated four pairs of potential events with cross-correlation significance $\geq 2\sigma$, none were above $3\sigma$ at both the LIGO-Hanford and LIGO-Livingston detectors. This makes it possible to strongly rule out the presence of any statistically significant sub-threshold lensed GW event in GWTC-4. The null detection translates to an upper bound on the
lensing detection rate to be $\leq$ 1.5/yr with inclusion of the sub-threshold event candidates. In the future, with more observation time, the detection of lensed GW can be possible from the current generation of GW detectors.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
The caustic method applied to The Three Hundred: prospects for upcoming CATARSIS and other surveys
B. Callejas Córdoba, P. Sánchez Blázquez, A. Gil de Paz et al. (+4 more)
We investigate the expected uncertainties in recovering
galaxy cluster mass profiles from upcoming spectroscopic survey data using The Three Hundred Project. Using the caustic technique, which leverages
galaxy positions and line-of-sight velocities, we assess the systematic errors introduced by assumptions regarding velocity anisotropy and demonstrate how an iterative correction method can minimize these errors. We also assess the impact of survey magnitude limits on cluster mass estimates, highlighting potential biases across different observational strategies. We focus the analysis on our own CATARSIS survey, which aims at obtaining
redshift measurements for all
galaxies with magnitudes mAB,r < 22 within 2xR200c of 16
galaxy clusters with
redshifts 0.14 < z < 0.27 using the future 8 arcmin^2 field-of-view TARSIS integral-field spectrograph of the Calar Alto 3.5-m
telescope. Such data will enable us to mitigate systematic errors in the determination of density profiles. CATARSIS aims at enhancing the precision of mass profile estimates by deepening our understanding of the dynamical states and physical characteristics of
galaxy clusters.
Read the full abstract ▾
All authors B. Callejas Córdoba, P. Sánchez Blázquez, A. Gil de Paz, A. Knebe, W. Cui, C. Catalán Torrecilla, R. Dave
Cosmology and Nongalactic Astrophysics
Possible explanation of primordial $^7$Li deficit
E.V. Arbuzova and A.D. Dolgov
A reduction mechanism of the theoretically predicted excessive abundance of $^7$Li via
baryons evaporated by
primordial black holes is suggested. It is shown that the fraction of $^7$Li with respect to the number density of
baryons can be diminished down to the observed value via the process of $^7$Li transformation by
neutron capture. The created in this process $^8$Li or $^8$Be quickly decay into a pair of $^4$He
nuclei.
Read the full abstract ▾
Astrophysics of Galaxies
Detection of a four-carbon sugar in interstellar space
Izaskun Jimenez-Serra, Juan Garcia de la Concepcion, Herma M. Cuppen et al. (+19 more)
Sugars are essential biomolecules, serving as metabolic fuels, nucleic acid backbone components, and structural or energy-storage
polymers. A central question in origin-of-life research is how monosaccharides formed on the primitive Earth, as laboratory experiments under prebiotic conditions yield insufficient concentrations. The detection of ribose, glucose and other monosaccharides in asteroids and meteorites suggests an exogenous origin, possibly in the interstellar medium (ISM) prior to meteoritic parent-body formation. However, no sugar has been observed in the ISM so far. We report the discovery of erythrulose, a
chiral four-carbon ketose, in the ISM. The detection has been achieved thanks to ultrasensitive, broadband spectral surveys toward the
Galactic Center molecular cloud G+0.693-0.027 obtained using the Yebes 40m and IRAM 30m
telescopes. Erythrulose appears to be at least eight times more abundant than analogous three-carbon sugars, which remain undetected in our ultrasensitive observations.
Quantum chemical and astrochemical models indicate that erythrulose forms efficiently on interstellar
dust grains from simpler two-carbon aldehydes and alcohols. As ketoses readily isomerize into aldoses in aqueous conditions, interstellar erythrulose could have contributed to the sugar inventory available for early metabolic and replication processes.
Read the full abstract ▾
All authors Izaskun Jimenez-Serra, Juan Garcia de la Concepcion, Herma M. Cuppen, Marta Rey-Montejo, Miguel Sanz-Novo, Victor M. Rivilla, Jesus Martin-Pintado, Andres Megias, Carlos Briones, David San Andres, Laura Colzi, Shaoshan Zeng, Sergio Martin, Joseph Salaris, Antonio Martinez-Henares, Alvaro Lopez-Gallifa, Miguel Requena-Torres, Belen Tercero, Pablo de Vicente, Aran Insausti, Elena R. Alonso, Emilio J. Cocinero
Astrophysics of Galaxies
A nine-member protostellar system forming via filament fragmentation in the high mass protocluster NGC 6334-43
D. J. Taylor, C. J. Cyganowski, C. L. Brogan et al. (+3 more)
We present the serendipitous discovery of a nine-member system comprised of protostellar and candidate prestellar sources in $\sim$350 au-resolution images from Complex Chemistry in hot Cores with ALMA (CoCCoA). The system is bound in a stability analysis, has a mean separation between pairs of 7930 au, and appears to have formed via the fragmentation of a single large-scale filamentary structure traced by 1.20\,mm continuum and H$^{13}$CO$^+$ J = 3-2 emission. Two multiples within the nine-member system, a triple and a binary, have properties consistent with formation by core fragmentation on $\sim$1500-1700 au scales. The hot core NGC 6334-43 is resolved into two components (ALMA2a/ALMA2b) separated by 618 au and driving a bipolar
outflow traced by $^{12}$CO J = 2-1 and SiO J = 5-4 in $\sim$1250 au-resolution archival Atacama Large Millimeter/submillimeter Array (ALMA) data. Only one other source in the nine-member system is clearly protostellar: ALMA6a, which drives an
outflow traced by $^{12}$CO. The
outflow properties of ALMA2a/ALMA2b and ALMA6a are consistent with high-mass and low-mass Class 0 sources respectively. By fitting the CH$_{3}$CN J = 13-12 emission towards ALMA2a, ALMA2b and ALMA6a, we derive M$_{\rm vir}$ = 4.5, 5.4 and 2.6 M$_{\odot}$ respectively. The other six sources in the nine-member multiple have M$_{\rm gas}$ = 0.50-1.87 M$_{\odot}$ and appear young, as indicated by their sparse mm-wavelength line emission and non-detection in published cm continuum observations. Our results highlight the potential of serendipitous discoveries in ALMA surveys to add to the small observational sample of young high-mass protomultiple systems.
Read the full abstract ▾
All authors D. J. Taylor, C. J. Cyganowski, C. L. Brogan, T. R. Hunter, B. A. McGuire, G. M. Williams
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Lorentz-violating signatures in quasi-periodic oscillations from a magnetised Kalb-Ramond black hole
Luiz F. G. Rodrigues, Francisco S. N. Lobo and Manuel E. Rodrigues
We investigate the dynamics of charged particles around a Schwarzschild-like black hole sourced by a Kalb-Ramond field and immersed in a uniform external
magnetic field. The Kalb-Ramond field introduces a Lorentz violation parameter $l$ that modifies the spacetime geometry, while the
magnetic field profoundly influences the trajectories through the Lorentz force, leading to a rich variety of orbital behaviours including curled (epicyclic) motion and dramatic transitions between distinct energy boundary configurations. We derive the full equations of motion, the effective potential, and the fundamental frequencies of quasi-periodic oscillations, and perform a comprehensive Monte Carlo Markov Chain (MCMC) analysis using observational data from the microquasars GRO 1655-40, XTE 1550-564, and GRS 1915+105. The pure Schwarzschild model is statistically ruled out for all three sources. For GRO 1655-40 and XTE 1550-564, only the combined effect of the
magnetic field and Lorentz violation yields statistically robust models, with best-fit values $\mathcal{B}\sim 0.03$-$0.04$ and $l\sim 0.08$–$0.10$. Remarkably, for GRS 1915+105, the most massive object in our sample, the Lorentz violation parameter alone is sufficient to model the QPO frequencies, yielding an optimal fit with $\Delta AIC = \Delta BIC = 0$. Across all three objects, a clear trend emerges: the required value of $l$ decreases as the mass of the astrophysical object increases, suggesting a mass-dependent scaling of the Kalb-Ramond parameter. These findings establish the combined KR and
magnetic field framework as a viable and statistically robust scenario for modeling QPOs in microquasars, and indicate that Lorentz-violating modifications to
gravity may leave observable imprints in the strong-field regime, offering new avenues for testing
quantum-
gravity phenomenology with current and next-generation X-ray missions.
Read the full abstract ▾
Astrophysics of Galaxies
COSMOS2025: Machine Learning Classification of Early- and Late-type Galaxies at 0 < z < 3
Vahid Asadi and Najmeh Sheikhi
We present a fast, interpretable machine learning framework to classify early- and late-type
galaxies in the COSMOS2025 catalog at $0 < z < 3$, without relying on image-based training labels or computationally expensive structural fitting. Using the Santa Cruz Semi-Analytic Model, we generate a training set with secure morphological labels defined by bulge-to-total mass ratio and specific
star formation rate. We bridge the simulation-to-observation domain gap by injecting realistic photometric noise derived from COSMOS2025. A CatBoostClassifier trained on 66 broadband colors achieves excellent performance in the simulated domain, recovering late-types with 98% precision/recall and early-types with 91% precision and 88% recall. Applied to 44,132 COSMOS2025
galaxies, the model reveals a striking bimodality: only about 6% of
galaxies receive intermediate probabilities ($0.3 < P(\text{Early type}) < 0.7$) – nearly identical to the fraction observed in the simulation. This demonstrates that broadband colors are a decisive morphological discriminant, with the remaining 94% classified at high confidence. Validation against independent bulge+disk decompositions yields 70% overall accuracy, with late-types identified at 78% purity and 74% completeness. The most important color feature, F277W-F444W, reflects the expected optical/NIR contrast between old and young
stellar populations. The full pipeline completes in under 30 minutes on standard hardware, demonstrating that simulation-trained color-based classifiers offer a scalable, physically interpretable route to approximate morphology for large next-generation surveys.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Fifty years of primordial helium abundances: A statistical reanalysis
Nabil Husain, Richard de Grijs and Giuseppe Bono
The
primordial helium mass fraction, $Y_\mathrm{p}$, is a key observational pillar of Big Bang nucleosynthesis and a sensitive probe of early-Universe physics. Over the past several decades, numerous observational $Y_\mathrm{p}$ determinations have been published using a wide range of astrophysical tracers and cosmological techniques. Although recent measurements exhibit striking convergence and increasingly small uncertainties, the statistical and historical context of this consensus has not been examined systematically. Here, we compile and analyse a comprehensive
dataset of observational $Y_\mathrm{p}$ determinations published between the late-1960s and 2022. The final sample comprises 143 reported values spanning multiple tracers. We find clear evidence for long-term convergence in published $Y_\mathrm{p}$ values, punctuated by statistically significant change points in the mid-2000s and early 2010s. Careful examination reveals that many extragalactic Hii-region determinations are not fully independent, relying on re-analyses or partial reuse of a limited number of observational
datasets. This reduces the effective number of independent constraints and provides important context for interpreting the precision of recent results. Our findings do not challenge the overall consistency of modern $Y_\mathrm{p}$ determinations with standard cosmology, but they underscore the importance of accounting for data dependence, methodological homogeneity and historical
evolution when synthesising measurements.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Comprehensive Analysis of Optical brightness and Color Variability of Blazars in the ZTF Survey DR22
Qi Yuan, Xin Wang, Meng Zhang et al. (+6 more)
This study conducts a comprehensive analysis of brightness and color variability in blazars, utilizing over six years of quasi-simultaneous g-band and r-band data from 1149 sources in the ZTF Data Release 22 (DR22), including 589 BL Lacs and 560 FSRQs. We quantify the amplitude of variability and the fractional root mean square (rms) variability for each source and statistically assess the overall and short-term color behaviors across different subclasses; examine the distribution of brightness variability characteristics across different blazar types and investigate how the extent of variability correlates with color trends. We found BL Lacs tend to exhibit a BWB (bluer when brighter) trend, while FSRQs display a RWB (redder when brighter) trend; BL Lacs with negligible host-
galaxy contamination exhibit a BWB trend fraction of 14.7% (68/462) compared to 2.3% (11/462) for RWB trend, while FSRQs show 8.8% (49/560) BWB trend versus 14.1% (79/560) RWB trend. By statistically investigating how color behavior depends on brightness state across different timescales, we find that brighter states in both BL Lacs and FSRQs are more likely to exhibit BWB trend. Our results also show that BL Lacs with a BWB trend exhibit higher variability than those with a RWB trend, whereas FSRQs with a RWB trend display significantly greater variability than those with a BWB trend. These results suggest that blazar color variability depends jointly on source type, brightness state, and variability amplitude, highlighting the complexity of color
evolution in blazars.
Read the full abstract ▾
All authors Qi Yuan, Xin Wang, Meng Zhang, Wenwen Zuo, Yan Xu, Chunguo Wu, Ming Zhang, Xiang Liu, Lang Cui
Astrophysics of Galaxies
A $z \sim$ 6.2 Quasar on the Local M$_{\rm BH}$-$\sigma_{\rm \ast}$ Relation Quenching Its Host Galaxy from the Aether Survey
Weizhe Liu, Emanuele Paolo Farina, Xiaohui Fan et al. (+19 more)
We report JWST/NIRSpec integral field unit (IFU) observations of the
quasar J1512$+$4422 at $z \sim 6.2$ from the Aether survey. At $\sim$900 Myr after the Big Bang, this object already lies on the $M_{\rm BH}$-$\sigma_\ast$ relation found in the local universe, with an $M_{\rm BH} \simeq 8.9\times10^8\,M_\odot$ and a
stellar velocity dispersion $\sigma_\ast \simeq 288$ km s$^{-1}$. We detect an
outflow with a velocity of $\sim$478 km s$^{-1}$ in the
nuclear region, which likely extends to $\sim$3.2 kpc in projection and has a median velocity of $\sim$352 km s$^{-1}$. The
outflow dynamical time scale ($\sim$ 9 Myr) is consistent with the time scale of the current quenching process based on the
star formation history as reported previously. The total mass
outflow rate (92.6$^{+92.6}_{-74.1}$ M$_{\odot}$ yr$^{-1}$) is larger than the current
star formation rate (0.9$^{+3.8}_{-0.8}$ or 4.3$^{+5.8}_{-3.7}$ M$_{\odot}$ yr$^{-1}$), and the total kinetic energy
outflow rate (0.6$^{+0.6}_{-0.5}$% of
quasar luminosity) meets the threshold for negative
quasar feedback as suggested by simulations. These results suggest that the
outflow is capable of suppressing/quenching the
star formation activity within the host
galaxy. Furthermore, J1512$+$4422 exhibits $\sigma_\ast$,
stellar mass and size similar to those of $z \gtrsim$ 3 quiescent/post-starburst
galaxies, implying a link between the two. Overall, for objects like J1512$+$4422, the
evolution of their SMBHs and host
galaxies appears to be tightly coupled within the first billion years. The
quasar feedback likely plays a critical role in both placing them on the $M_{\rm BH}$–$\sigma_\ast$ relation and quenching.
Read the full abstract ▾
All authors Weizhe Liu, Emanuele Paolo Farina, Xiaohui Fan, Roberto Decarli, Masafusa Onoue, Haowen Zhang, Eduardo Banãdos, Aaron J. Barth, Fabrizio Arrigoni Battaia, Manuela Bischetti, Sarah E. I. Bosman, Hyunseop Choi, Tiago Costa, Simona Gallerani, Anniek J. Gloudemans, Xiangyu Jin, Federica Loiacono, Yoshiki Matsuoka, Chiara Mazzucchelli, Fabian Walter, Feige Wang, Jinyi Yang
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
The decay rate of metastable cosmic strings beyond the thin-string approximation
Valerie Domcke and Yu Hamada
In the context of grand unified theories, any
cosmic strings present in the post-inflationary universe are likely to be metastable, with a decay rate set by the spontaneous creation of monopole pairs on the string. Determining this decay rate is crucial in understanding the phenomenology of the
cosmic string network, including a potentially observable gravitational wave background. The bounce action governing this rate has so far only been determined using the thin string approximation or specific ansätze for the field profiles in the monopole formation process. Here we solve this problem using classical
lattice simulations, relying only on the inherent
symmetries of the problem. Our results indicate a suppression of the bounce action and hence a faster string decay compared to previous estimates.
Read the full abstract ▾
Earth and Planetary Astrophysics
Dust On, Dust Off: HST Observations of the Newly Dormant Jupiter Co-orbital Comet P/2023 V6 (PANSTARRS)
John Noonan and Theodore Kareta
As the Centaurs of the Outer
Solar System have become better studied, their relationship with the Jupiter Family Comets and their connection to the
primordial protoplanetary disk has come under deeper scrutiny: which properties of the comets observed closer to the Sun are original, and which were modified significantly en route during their Centaur phase? The active Jupiter co-orbital comet P/2019 LD2 (ATLAS) attracted significant
attention after its discovery when it was realized that the object would transition between a Centaur and JFC orbit in 2063, the first time this change can be observed and monitored in real time. In this study, we present new ground-based and Hubble Space
Telescope imaging of the single other Jupiter co-orbital comet, P/2023 V6 (PANSTARRS), throughout late 2024 and early 2025. V6 was not detected in ground-based imaging after early October, and deep imaging with HST taken in early December is consistent with a $m_V = 28.06 \pm 0.03$ point source at its expected location. This both implies that the object ceased activity sometime in late 2024, and is thus in a different thermal state than LD2 despite both having large active fractions, and that V6's diameter is approximately $D\sim340$ meters. This is likely the smallest object directly observed by HST beyond the Main Belt, and certainly the smallest Centaur yet discovered, highlighting the ability to detect active sub-km objects beyond Jupiter with current surveys and potentially probing smaller sizes with LSST.
Read the full abstract ▾
High Energy Astrophysical Phenomena
Sensitivity of the Neutron Star Equation of State Inferences to Mass and Radius Measurements
Dmitry D. Ofengeim, Peter S. Shternin and Tsvi Piran
We examine how inferences of the
neutron-
star equation of state depend on mass and radius observations. We update previous results with recent measurements combined with theoretical input from
chiral effective field theory and perturbative
quantum chromodynamics. The revised constraints are consistent with, but tighter than, those obtained in earlier work. Isolating the effects of different classes of observations we find that the theoretical constraints, together with the requirement that the maximal
neutron-
star mass exceeds $2\,M_\odot$, dominate the equation-of-state inference over most densities. Radius measurements mainly refine the constraints at the low-density regime, $\rho \lesssim 2\rho_0$, whereas measurements of masses well above $2\,M_\odot$ improve the constraints over a wider density range. Finally, we explore the impact of possible future observations. The largest impact would arise from a measurement that refines the value of the maximal
neutron star mass. It can be, e.g., a detection of an extremely massive
neutron star or an improved upper limit. However, even a precise measurement a $2.5-2.6\,M_\odot$ NS will not alter our knowledge of the equation of state qualitatively. Conversely, observations lying well outside the present allowed region, would point to new physics in
neutron-
star cores and require a revision of the current framework.
Read the full abstract ▾