Solar and Stellar Astrophysics
Asteroseismic detection of an internal magnetic field in the B0.5V pulsator HD 192575
Jelle Vandersnickt, Vincent Vanlaer, Mathijs Vanrespaille et al. (+1 more)
Internal
magnetic fields are an elusive component of
stellar structure. However, they can play an important role in
stellar structure and
evolution models through efficient angular momentum transport and their impact on internal mixing. We strive to explain the 9 components of one frequency multiplet, identified as a low-order quadrupole
gravity mode detected in the light curve of the beta Cep pulsator HD 192575 assembled by the Transiting
Exoplanet Survey Satellite (TESS). We update the frequencies of the quadrupole mode under investigation using a standard prewhitening method applied to the 1951.46 d TESS light curve, showing that an internal
magnetic field is required to simultaneously explain all 9 components. We implement theoretical pulsation computations applicable to the low-order modes of a beta Cep pulsator including the Coriolis force, as well as a
magnetic field that is misaligned with respect to the rotation axis. We apply the theoretical description to perform asteroseismic modelling of the amplitudes and frequencies in the multiplet of the quadrupole g-mode of this evolved beta Cep
star. Pulsation predictions based on the measured internal rotation frequency of the
star cannot explain the observed 9-component frequency splittings of the quadrupole low-order
gravity mode. By contrast, we show that the combined effect of the Coriolis force caused by the near-core rotation with a period of about 5.3 d and the Lorentz force due to an internal inclined
magnetic field with a maximum strength of around 24 kG does provide a proper explanation of the 9 multiplet frequencies and their relative amplitudes. Given the
stellar mass of about 12
solar masses, this work presents the detection and magneto-gravito-asteroseismic modelling of a stable internal
magnetic field buried inside an evolved rotating
supernova progenitor.
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All authors Jelle Vandersnickt, Vincent Vanlaer, Mathijs Vanrespaille, Conny Aerts
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
A Comprehensive Study of WIMP Models Explaining the Fermi-LAT Galactic Center Excess
Chuiyang Kong and Mattia Di Mauro
The
Galactic Center excess (GCE) of GeV $\gamma$ rays may hint at dark matter (DM), yet its origin remains debated. Motivated by this, we survey weakly interacting massive particle (WIMP) models that can fit the GCE while satisfying relic-density, direct-detection (DD), and indirect-detection (ID) bounds. We group candidates into hadronic (
Higgs portals; simplified scalar/vector mediators), leptonic ($U(1)_{L_i-L_j}$), and mixed ($U(1)_{B-L}$, $Z$-portal) classes. Across all cases, present DD and
dwarf-spheroidal $\gamma$-ray limits exclude wide regions, leaving mainly narrow resonant funnels with $m_{\rm DM}\!\simeq\! m_{\rm med}/2$ and portal couplings $\ll 1$. In hadronic setups, scalar and vector
Higgs portals survive only in a thin strip near $m_h/2\simeq62.5$ GeV with portal couplings $\sim 10^{-4}$, while the Dirac
Higgs and $Z$ portals are essentially excluded. The UV-complete vector
Higgs portal retains resonant bands whose viable portal strength depends on the mixing angle. Simplified scalars allow small windows for complex-scalar or vector DM; Dirac DM is strongly disfavored, whereas a pseudoscalar with Dirac DM remains viable over a broader parameter range. For a simplified $Z'$ mediator, a pure vector coupling leaves only a marginal region, while pure axial is excluded by DD/ID bounds. In leptonic scenarios, inverse-Compton emission is essential: $L_\mu-L_e$ (and, to a lesser extent, $B\!-\!L$) fits the GCE with near-thermal cross sections, while $L_\mu-L_\tau$ is disfavored. Overall, viable WIMP explanations are constrained to finely tuned resonant regime, with leptophilic vectors and pseudoscalar portals emerging as the most robust options.
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Astrophysics of Galaxies
Effects of Resolution and Local Stability on Galactic Disks: I. Multiple Spiral Mode Formation via Swing Amplification
SungWon Kwak, Ivan Minchev, Christoph Pfrommer et al. (+2 more)
We investigate the formation of multiple spiral modes in Milky Way-like disk-
halo systems without exciting perturbations. We explore how numerical resolution, the level of local disk stability, and the presence of a live
halo influence the initial appearance and the subsequent
evolution of these modes. To characterize spiral structure, we compute
Fourier amplitudes for modes m=1-6. In marginally unstable, lower-resolution disks, faint features appear within the first 0.5 Gyr due to numerical noise, in contrast to high-resolution models where perturbations emerge later. We find that the delay in the spiral and bar formation epoch due to the enhanced resolution is more significant in the more stable models. Across all sufficiently resolved, live-
halo models with $m_{DM}/m_{\star}\le10$, the spirals exhibit a cascading sequence in both mode number and radius: higher-m modes form and decay first, followed by the delayed emergence of lower-m modes, with an inward drift of the activity's epicenter. This behavior reflects a combination of local swing amplification, which explains the initial growth of short-wavelength modes, and interference between coexisting coherent spiral components with different pattern speeds, which accounts for the recurrent short-timescale amplitude modulations. In contrast, models with a fixed
halo potential or coarse
halo resolution show strong early spirals but lack this coherent cascading behavior, owing to excessive shot noise and insufficient
halo responsiveness. The m=3 mode plays a transitional role, marking the onset of angular-momentum transport in the inner disk that precedes bar formation, a process absent in fixed-potential models. Our results show that a live
halo with appropriate mass resolution provides the gravitational response needed to sustain and regenerate multi-mode spiral structure, even though the total angular-momentum exchange remains small.
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All authors SungWon Kwak, Ivan Minchev, Christoph Pfrommer, Matthias Steinmetz, Sukyoung K. Yi
Astrophysics of Galaxies
Globules and pillars in Cygnus X IV. Velocity-resolved [OI] 63 mu map of a peculiar proplyd-like object
N. Schneider, S. Dannhauer, E. Keilmann et al. (+14 more)
We investigated an isolated, globule-shaped object (0.37x0.11 pc), located near the centre of the Cygnus OB2 cluster and named proplyd #7 in optical observations. The source can be a massive
star (with or without disc) with a HII region or a G-type T Tauri
star with a photo-evaporating disc, embedded in a molecular envelope. We obtained a map of the OI line at 63 micron with 6" angular resolution and employed archival data of the CII 158 micron line (14" resolution), using the upGREAT heterodyne receiver aboard SOFIA. We also collected IRAM 30m CO data at 1mm (11" resolution). All the lines were detected across the whole object. The peak integrated OI emission of ~5 K km/s is located ~10" west of an embedded YSO. The OI and CII data near the source show bulk emission at ~11 km/s and a line wing at ~13 km/s, while the 12CO 2-1 data reveal additional blue-shifted high-velocity emission. The KOSMA-tau PDR model can explain the emissions in the tail with a low external UV field (<350 Go, mostly consistent with our UV field estimates), but not at the location of the YSO. There, the high line intensities and increased line widths for all lines and a possible bipolar CO
outflow suggest the presence of a protostellar disc. However, the existence of a thermal HII region, revealed by combining existing and new
radio continuum data, points towards a massive
star - and not a T Tauri-type one. We derived molecular and atomic gas masses of ~20 Msun and a few Msun, respectively. The photo-evaporation (only considering external illumination) lifetime of 1.6x10^5 yrs is shorter than the free-fall lifetime of 5.2x10^5 yrs; thus, we find that proplyd #7 might not have had the time to produce many more
stars.
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All authors N. Schneider, S. Dannhauer, E. Keilmann, S. Kabanovic, T. Topkaras, V. Ossenkopf-Okada, R. Higgins, A. Brunthaler, Won-Ju Kim, F. Comeron, M. Roellig, T. Csengeri, R. Simon, Y. Okada, M. Justen, S.A. Dzib, G. N. Ortiz-León
Cosmology and Nongalactic Astrophysics
Cosmological Constraints on 4D Einstein-Gauss-Bonnet Gravity and Kaniadakis Holographic Dark Energy: Implications for Black Hole Shadows
Xiang-Qian Li, Hao-Peng Yan and Xiao-Jun Yue
The direct imaging of black holes by the Event Horizon
Telescope (EHT) enables strong-field tests of
gravity. We study the cosmological
evolution and the black-hole shadow radius in 4D Einstein-Gauss-Bonnet (EGB)
gravity coupled to Kaniadakis
holographic dark energy (KHDE), adopting the future event horizon as the infrared cutoff. Using
Cosmic Chronometers, Pantheon+ Type Ia
supernovae, and DESI BAO data, we constrain the model with a Markov Chain Monte Carlo analysis. The best-fit values favor a phantom-like equation of state driven by Kaniadakis
entropy ($c\simeq 1.18$, $\beta\simeq 2.26$), but $\beta$ remains weakly constrained ($\beta=2.26^{+0.11}_{-2.20}$), consistent with the standard
holographic limit $\beta\to0$ at $1\sigma$. The EGB coupling is constrained to $\alpha\simeq -0.004$, also consistent with General Relativity ($\alpha=0$) at $1\sigma$. Guided by the posterior, we define five representative scenarios to probe the dynamical phase space. We find that the
accretion history is highly sensitive to the thermodynamic sector: standard
holographic cases yield monotonic
evolution, whereas phantom-divide crossing leads to non-monotonic behavior in both the black hole mass and the
vacuum shadow radius. Including a dispersive
plasma medium, refraction dominates over intrinsic mass growth and induces an overall shrinkage of the observable shadow at high
redshift; nevertheless, a residual intrinsic deviation of $\sim6\%$ (for our conservative
accretion setup) persists at $z\simeq2$ relative to the $\Lambda$CDM prediction. These results indicate that, despite environmental dominance, precision population analyses of black hole shadows may help disentangle subtle dynamical dark-energy imprints from the standard cosmological paradigm.
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Solar and Stellar Astrophysics
Axion Constraints from White Dwarf Cooling in 47 Tucanae
Leesa Fleury, Alysa Obertas, Harvey Richer et al. (+1 more)
We analyse the cooling of white
dwarfs in the globular cluster 47 Tucanae to look for evidence of
axion emission affecting the rate of white
dwarf cooling. If
axions exist and couple to electrons, then
axions could be produced at an appreciable rate in the electron-degenerate core of a white
dwarf through
axion bremsstrahlung from electrons. The emission of these
axions would provide an additional cooling mechanism for white
dwarfs that would affect the cooling rate, and hints of
axions have been suggested based on observations of anomalous cooling reported for white
dwarfs in the
Galactic disc and
halo. We performed
stellar evolution simulations of white
dwarf cooling that accounted for the additional energy loss due to
axion bremsstrahlung from electrons, producing a suite of white
dwarf cooling models for different values of the
axion-electron coupling constant, as well as the white
dwarf mass and envelope thickness. These cooling models are compared to observations of white
dwarfs in 47 Tucanae from the Hubble Space
Telescope through an unbinned likelihood analysis. The optimal model found by this analysis corresponds to the case of no
axion emission with a thick white
dwarf envelope, and we find a new bound on the
axion-electron coupling of $g_{aee} \leq 0.81 \times 10^{-13}$ at 95% confidence level, conditional on the adopted white
dwarf cooling models and priors. This bound improves upon the previous white
dwarf cooling bound for this coupling and excludes the range of values favoured by the
axion hints from the anomalous cooling of
Galactic white
dwarfs.
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All authors Leesa Fleury, Alysa Obertas, Harvey Richer, Jeremy Heyl
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Cosmological Probes of Lepton Parity Freeze-in Dark Matter: $\Delta N_{\rm eff}$ & Gravitational Waves
Ernest Ma, Partha Kumar Paul and Narendra Sahu
In the canonical type-I seesaw mechanism for
neutrino masses, a residual
symmetry known as
lepton parity: $(-1)^L$, remains preserved. Introducing a Majorana
fermion $S$ with even
lepton parity renders it naturally stable, making it a viable dark matter (DM) candidate. The addition of a
lepton parity odd singlet scalar $\sigma$ allows for the coupling $N S \sigma$, where $N$ is the right-handed
neutrino. If $S$ is not thermalized, then DM relic can be produced in two distinct ways: (i) for reheating temperature, $T_{\rm rh}>m_{N}$, dominantly through the decay of $N$ ($N\rightarrow S\sigma$), and (ii) for $T_{\rm EW}<T_{\rm rh}\ll m_{N}$, via standard model
Higgs ($h$) decay ($h\rightarrow SS$ at one loop). If the $\sigma-h$ quartic coupling is large, then it can lead to a strong first-order electroweak phase transition even if $\langle\sigma\rangle=0$. Alternatively, if $\sigma-h$ coupling is small, then $\sigma$ can freeze out with a larger abundance, and hence its decay ($\sigma\rightarrow S\nu$) at late epochs can give rise to additional relativistic degrees of freedom ($\Delta{N}_{\rm eff}$). Thus, the framework gives a viable DM with mass range varying from MeV to TeV and leaves observable imprints, via gravitational waves and $\Delta{N}_{\rm eff}$, which offer complementary probes, potentially detectable in future gravitational wave and CMB experiments.
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Astrophysics of Galaxies
New Signs Pointing Toward a Correlation Between Astrophysical Neutrinos and Radio Flares
Yjan A. Gordon, Peter S. Ferguson, Eric J. Hooper et al. (+1 more)
We use data from the first two epochs of the Very Large Array Sky Survey (VLASS) and the IceCube
Neutrino Observatory to search for evidence of a correlation between
radio variability and the detection of astrophysical
neutrinos. Our work probes the
radio population down to $S_{3\,\text{GHz}}\gtrsim$ a few mJy, more than an order of magnitude fainter than previous analyses that aim to cross correlate
radio variability with
neutrino detections. We find an excess number of associations between flaring
radio sources and
neutrinos that were detected between the first and second VLASS observations at $>2\sigma$ confidence. This excess is consistent with
radio flares contributing $\sim13\,\%$ of the astrophysical
neutrinos observed by IceCube. Notably, $\sim90\,\%$ of the
radio flares associated with
neutrinos are not detected at either $\gamma$-ray or X-ray wavelengths, highlighting the importance of deep
radio observations for identifying potential electromagnetic counterparts to astrophysical
neutrinos. No excess in the number of associations between the wider
radio-variable population and the IceCube
neutrinos is seen when no time constraint is placed on the
neutrino detection. We predict that data from future VLASS epochs will see an excess number of associations between
radio flares and
neutrinos at the $>3\sigma$ level, and expected improvements to the positional constraints on the
neutrinos may increase that confidence to $>5\sigma$, should our results be representative.
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All authors Yjan A. Gordon, Peter S. Ferguson, Eric J. Hooper, Michael N. Martinez
Astrophysics of Galaxies
A Super-Eddington, Lensing-Magnified Quasar at $z=5.07$ observed with JWST
Katherine Panebianco, Minghao Yue, Anna-Christina Eilers et al. (+4 more)
We present JWST/NIRCam F070W and F480M imaging for a
quasar at $z = 5.07$, J0025-0145, which is magnified by a foreground
lensing galaxy. Existing Hubble Space
Telescope (HST) imaging does not have sufficient spatial resolution to determine whether the background
quasar is multiply imaged. Exploiting the sharp PSF of the F070W band, we confirm that the background
quasar can be well-described by a single point spread function (PSF), essentially ruling out the existence of multiple lensed images. We do not detect the
quasar host
galaxy in either the F070W or the F480M band. Using the HST and JWST photometry, we fit the Spectral Energy Distribution (SED) of the foreground
galaxy. The estimated mass ($\log(M_{*} / M_{\odot}) = 11.15 \pm 0.16$) and
redshift ($z_{\text{phot}} = 3.62_{-0.04}^{+0.06}$) of the foreground
galaxy are consistent with a single-image
lensing model. We estimate the maximum possible magnification of the
quasar to be $\mu_{\text{max}} = 3.2$, which implies that the intrinsic Eddington ratio of the
quasar is at least $\lambda_{\text{Edd}}^{\text{intrinsic}} > 4.9$. Therefore, J0025-0145 has one of the highest Eddington ratios among $z>5$ supermassive black holes known so far, suggesting the viability of super-Eddington growth for supermassive black holes in the early universe.
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All authors Katherine Panebianco, Minghao Yue, Anna-Christina Eilers, Xiaohui Fan, Feige Wang, Jinyi Yang, Robert A. Simcoe
Earth and Planetary Astrophysics
Transit Timing of the White Dwarf-cold Jupiter System WD 1856+534
Eli A. Gendreau-Distler, Kate B. Bostow, Kishore C. Patra et al. (+17 more)
We present new transit-timing measurements for the white
dwarf-cold Jupiter system WD 1856+534, extending the baseline of observations from 311 epochs to 1498 epochs. The
planet is unlikely to have survived the host
star's red-
giant phase at its present location and is likely too small for common envelope
evolution to take place. As such, a plausible explanation for the short semimajor axis is that the
exoplanet started out on a much larger orbit and then spiraled inward through high-eccentricity
tidal migration (HETM). A past study found tentative evidence for orbital growth, which could have been interpreted as a residual effect of HETM, but we find the data are consistent with a constant-period model after adding 18 new transit measurements. We use the estimated period derivative $\dot{P} = 0.04\pm0.43$ ms yr$^{-1}$ to place a lower limit on the planetary
tidal quality factor of $Q_p' \gtrsim 3.1 \times 10^6$, if the
planet has not already achieved
spin-orbit synchronization. We also test for the presence of companion
planets in the system, which could have excited WD 1856 b onto an eccentric orbit via the Kozai-Lidov process, and ultimately rule out the presence of an additional
planet with mass greater than 4.0 $M_J$ and period shorter than 1500 days. We find no evidence for nonzero eccentricity, with an upper limit of $e \lesssim 10^{-2}$. If the
planet reached its current orbit through HETM, the low present-day eccentricity indicates that the migration process has now ceased, and any further orbital
evolution, if any, will likely be governed by weak planetary tides.
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All authors Eli A. Gendreau-Distler, Kate B. Bostow, Kishore C. Patra, Efrain Alvarado III, Andreas Betz, Victoria M. Brendel, Vidhi Chander, Asia A. DeGraw, Cooper Jacobus, Connor F. Jennings, Ann Mina, Ansel Parke, Riley Patlak, Neil R. Pichay, Sophia Risin, Edgar P. Vidal, William Wu, Thomas G. Brink, WeiKang Zheng, Alexei V. Filippenko
Solar and Stellar Astrophysics
Formation and nature of "Huntsman" binary pulsars
O. G. Benvenuto, M. A. De Vito, M. Echeveste et al. (+4 more)
Spider systems are a class of close binaries in which a
neutron star first accretes from a normal companion, and later ablates it in some cases. New observations have expanded this category, with the addition of a Huntsman group, tentatively linked to a short donor phase along the red bump in the secondary evolutionary track. We present explicit evolutionary tracks that support the Huntsman nature recently suggested, and discuss how the whole class of spiders emerges from the full consideration of irradiation and ablating winds. We address the irradiation feedback (IFB) effects and the hydrogen-shell burning detachment (HSBD) simultaneously, and show that they act independently and do not interfere with each other, supporting a physical picture of the Huntsman group. We employ our binary
evolution code to compute a suite of binary systems formed by a donor
star and a
neutron star for different initial orbital periods, assuming
solar composition and Z=0.01. Although many models do not consider IFB, we also present the
evolution with IFB for one system as an example. We found that the recently suggested association of Huntsman
pulsar with the evolutionary stage where (as a consequence of the dynamics of HSBD) the system remains detached for a few million years is plausible. However, this feature alone is unable to account for the occurrence of Redback spider
pulsars. Meanwhile, models including IFB, with pulsed mass transfer, display detachment episodes that can be naturally associated with the Redback stage. Irradiation feedback does not preclude or modify HSBD and in fact, Huntsman systems were already present as an implicit prediction in our earlier calculations. We conclude that Huntsman is an expected stage of the spider systems under quite general conditions. This is another step towards a unified picture of spider
pulsars as a group.
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All authors O. G. Benvenuto, M. A. De Vito, M. Echeveste, M. L. Novarino, N. D. Pires, L. M. de Sá, J. E. Horvath
Cosmology and Nongalactic Astrophysics
Large-Scale Galaxy Correlations from the DESI First Data Release
Francesco Sylos Labini and Tibor Antal
We quantify
galaxy correlations using two distinct three-dimensional samples from the first data release of the Dark Energy Spectroscopic Instrument (DESI): the Bright
Galaxy Sample (BGS) and the Luminous Red
Galaxy Sample (LRGS). Specifically, we measure the conditional average density, defined as the average density of
galaxies observed around a typical
galaxy in the sample. To minimize boundary effects, we adopt a conservative criterion: only
galaxies for which a spherical volume of radius $r$, centered on them, is fully contained within the survey footprint are included in the computation. For the BGS, we construct four volume-limited subsamples in order to eliminate biases arising from luminosity-dependent selection effects. By contrast, the LRGS is approximately volume-limited by design. The resulting samples span different depths, providing an opportunity to test the stability of statistical measurements across survey volumes of increasing size. Our results show that the conditional average density follows a power-law decay, $\langle n(r) \rangle \propto r^{-0.8}$, without exhibiting any transition to homogeneity within the survey volume. The large statistics of the DESI samples also allow us to demonstrate that finite-size effects become significant as $r$ approaches the boundaries of the sample volumes. Consistently, we find that the distribution of density fluctuations follows a Gumbel distribution - characteristic of extreme-value statistics - rather than a Gaussian distribution, which would be expected for a spatially homogeneous field. These findings confirm and extend the trends previously observed in smaller
redshift surveys, supporting the conclusion that the
galaxy distribution does not undergo a transition to spatial homogeneity within the probed scales, up to $r \sim 400$~\text{Mpc}/$h$.
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High Energy Astrophysical Phenomena
Enhanced antineutrino emission from $\beta$ decay in core-collapse supernovae with self-consistent weak decay rates
T. Dasher, A. Ravlić, S. Lalit et al. (+2 more)
Nuclear weak-interaction rates are known to exert a prominent effect in the late-stages of
stellar collapse. Despite their importance, most studies to date on core-collapse
supernovae (CCSNe) have focused primarily on the effects of electron captures, neglecting $\beta$~decay contributions. In this work, we present the first CCSNe simulation incorporating global $\beta$~decay rates from a microscopic theory. These are enabled by a large-scale evaluation of both electron capture and $\beta$~decay rates, obtained self-consistently utilizing the relativistic energy density functional theory and finite-temperature quasiparticle random-phase approximation. Including $\beta$ decay leads to a dramatic enhancement of the pre-bounce antineutrino signal as the antineutrino emissivity increases by more than two orders of magnitude and the luminosity by a factor of 50 relative to thermal emission alone, while the average antineutrino energy increases by over 1 MeV. It is expected that these new rates could help us constrain the model uncertainties related to weak-interaction processes, improving the prediction of antineutrino signal during the final stages of
stellar death.
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All authors T. Dasher, A. Ravlić, S. Lalit, E. O'Connor, K. Godbey
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Cosmological Implications of the Extended Uncertainty Principle: Energy Conditions, Stability, and Late Time Acceleration
Maryam Roushan and Narges Rashidi
We study the cosmological consequences of the Extended Uncertainty Principle (EUP) by deriving modified Friedmann equations through thermodynamic arguments. The
evolution of the effective equation of state induced by EUP corrections is analyzed and characterized using the Chevallier-Polarski-Linder (CPL) parametrization. We then examine the fulfillment of classical energy conditions, including the null, weak, strong, and dominant conditions. The dynamical and thermodynamic stability of the model is investigated, showing that the EUP cosmology admits a late-time de Sitter attractor. Finally, we evaluate the effective speed of sound associated with the model and discuss implications for perturbative stability. Our findings indicate that EUP-induced corrections can produce a consistent late-time acceleration without requiring a cosmological constant.
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High Energy Astrophysical Phenomena
Simulations of high-energy neutrino emissions from blazars with the LeHa-Paris code
Francesco Carenini and Matteo Cerruti
The identification of astrophysical sources responsible for high-energy
cosmic neutrinos has long been a challenge. A significant milestone was achieved with the blazar TXS 0506+056, which was found to be in a flaring state of high gamma-ray emission and associated at the 3$\sigma$ level with a 290 TeV
neutrino detected by IceCube in September 2017. This discovery motivated deeper exploration of the theoretical link between
photon and
neutrino emissions. In this context, simulations of
proton-
photon interactions in blazars and radiative processes are conducted using advanced numerical codes to predict
neutrino spectra. The LeHa-Paris code, previously applied to TXS 0506+056, enables the computation of both leptonic and hadronic components of blazar spectral energy distributions, facilitating exploration of a broad parameter space. In this work, starting from the case of PKS 2155-304, one of the brightest and most studied High-frequency-peaked BL Lacs (HBLs), known for its extreme variability and subject of multi-wavelength observational campaigns, a methodology has been developed to extend
neutrino flux templates, optimized via LeHa-Paris, to the full class of HBLs. Afterwards,
neutrino emission models for a subset of HBLs from the 3HSP catalogue are derived.
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Astrophysics of Galaxies
Galaxy evolution in the post-merger regime. IV – The long-term effect of mergers on galactic stellar mass growth and distribution
Sara L. Ellison and Leonardo Ferreira
Galaxy mergers are known to trigger bursts of central
star formation, which should therefore lead to
stellar mass growth in their inner regions. However, observational measurements of this `burst mass fraction' are scant. Here, we assemble a large sample of ~14,000 post-coalescence
galaxies that have recently completed their merger-induced
star formation, and compare various measurements of central
stellar mass with a matched control sample. Specifically, we quantify (at fixed
redshift,
star formation rate and total
stellar mass) the
stellar mass enhancement within a fixed angular aperture (Delta M_{
star,fibre}) and in the
galactic bulge (Delta M_{
star,bulge}), finding burst mass fractions of 10 – 20%. 61
galaxies in our sample are at z<0.05 and have integral field unit data from the Mapping
Galaxies at Apache Point (MaNGA) survey, allowing further kpc-scale assessment of excess
stellar mass and radial gradients. When assessed within apertures defined in units of kpc we again find a ~ 15 – 20% excess of
stellar mass in the central regions of the post-mergers compared with matched controls. However, within apertures defined in units of effective radius this
stellar mass enhancement increases to 40%, suggesting that the relative structure/size of the
galaxy is important for regulating the location of the merger induced
star formation. Moreover, we find that these
stellar mass enhancements are spatially extended, out to ~7 kpc or around 1 R/R_e, although the small sample size of the MaNGA overlap limits our radial sampling. Our work represents the first direct measurement of merger-induced
stellar mass growth that is independent of
stellar population modelling, or fitting light profiles, demonstrating significant and extended mass build-up in late stage post-mergers.
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Solar and Stellar Astrophysics
Variability of H$\alpha$ chromospheric activity of solar-like stars revealed by the time-domain data of LAMOST Medium-Resolution Spectroscopic Survey
Han He, Ali Luo, Haotong Zhang et al. (+1 more)
The variability of H$\alpha$ chromospheric activity of
solar-like
stars is investigated by using the time-domain data of LAMOST Medium-Resolution Spectroscopic Survey (MRS). We use $R_\mathrm{H\alpha}$ index (ratio of H$\alpha$ luminosity to bolometric luminosity) to measure the H$\alpha$ activity intensity of a spectrum, and utilize the median of the $R_\mathrm{H\alpha}$ values of multiple observations ($R_\mathrm{H\alpha}^\mathrm{median}$) as the representative activity intensity of a
stellar source. The H$\alpha$ variability of a
stellar source is indicated by the extent of $R_\mathrm{H\alpha}$ fluctuation ($R_\mathrm{H\alpha}^\mathrm{EXT}$) of multiple observations. Our sample shows that $R_\mathrm{H\alpha}^\mathrm{EXT}$ of
solar-like
stars is about one order of magnitude smaller than $R_\mathrm{H\alpha}^\mathrm{median}$. The distribution of $\log R_\mathrm{H\alpha}^\mathrm{EXT}$ versus $\log R_\mathrm{H\alpha}^\mathrm{median}$ reveals the distinct behaviors between the
stellar source categories with lower ($\log R_\mathrm{H\alpha}^\mathrm{median} < -4.85$) and higher ($\log R_\mathrm{H\alpha}^\mathrm{median} > -4.85$) activity intensity. For the former
stellar source category, the top envelope of the distribution first increases and then decreases with $\log R_\mathrm{H\alpha}^\mathrm{median}$; while for the latter category, the top envelope of the distribution is largely along a positive correlation line. In addition, for the
stellar sources with lower activity intensity, the large-$\log R_\mathrm{H\alpha}^\mathrm{EXT}$ objects near the top envelope of the $\log R_\mathrm{H\alpha}^\mathrm{EXT}$ versus $\log R_\mathrm{H\alpha}^\mathrm{median}$ distribution tend to have long-term and regular variations of H$\alpha$ activity; while for the
stellar sources with higher activity intensity, the H$\alpha$ variations are more likely to be random fluctuations.
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All authors Han He, Ali Luo, Haotong Zhang, Song Wang
High Energy Astrophysical Phenomena
The Feasibility of Using Fe XXIII Metastable Transitions as a Density Diagnostic for LMXB Disk Winds
D. L. Moutard, L. R. Corrales, R. Tomaru et al. (+6 more)
Low mass X-ray binaries (LMXBs) occasionally show signs of outflowing material from the
accretion disk. Studying these
outflows can inform the understanding of the geometry of the systems, as well as the dynamics and energetics of
accretion. One key variable for determining the location of these disk winds is the density of the outflowing material. In this paper we explore a density diagnostic based upon the absorption of ionizing
photons by density-sensitive metastable states of Fe XXIII. This can yield a blue shifted complex of absorption features in the region of $6.61-6.64$ keV. We use the photoionization code pion to test how varying the ionizing spectrum affects the detectability and interpretation of these features. We base these ionizing spectral energy distributions on GX~13$+$1 to represent a bright thermally dominated spectrum; 4U 1735$-$44 representing a harder, fainter LMXB spectrum; and MAXI J1820$+$070 representing a black hole LMXB spectrum completely dominated by Comptonized emission. For each of these, we find that the regime where Fe XXIII can be used as a density diagnostic is with an ionization parameter $\log{(\xi/{\rm erg~cm~s^{-1}})}\sim2-3$ and an
outflow density $\log{(n_H/{\rm cm^{-3})}}\gtrsim14$. The typical range of ionization parameters for LMXBs indicates that this technique is more feasibly achieved with BH LMXBs than their NS counterparts.
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All authors D. L. Moutard, L. R. Corrales, R. Tomaru, C. Done, J. Neilsen, E. Behar, E. Costantini, M. Díaz-Trigo, S. Yamada
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
The relativistic tidal tensor: general solutions for stationary axisymmetric spacetimes and the Hills mass of naked singularities
Wenkang Xin and Andrew Mummery
The
tidal forces experienced on an orbit contain, in principle, information about the underlying spacetime an object is moving through. Astronomical observations often probe the properties of
tidal forces in the relativistic regime, and could thus in principle be leveraged to examine the properties of strong-field
gravity, provided that a general procedure for computing the relativistic
tidal tensor is known. Existing techniques for deriving the
tidal tensor rely on cumbersome, case-by-case methods. This paper introduces a unified analytical approach to deriving the
tidal accelerations experienced by a test particle in any stationary, axisymmetric spacetime. This technique uses standard relativistic frame transformations and is built around the zero angular momentum observer frame. The method's utility is demonstrated in the four traditional black hole metrics: Schwarzschild, Reissner-Nordstrom, Kerr, and Kerr-Newman, as well as a particular wormhole metric. As an example of a possible astronomical application of this work, we discuss the concept of the Hills mass, the maximum mass at which a black hole can disrupt a
star, and extend its definition to various naked singularity metrics.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Bayesian analysis of the complex singlet model with phase transition gravitational waves
Qingyuan Liang, Ligong Bian, Huai-Ke Guo et al. (+1 more)
We explore the prospects of probing the complex singlet extension of the Standard Model (CxSM) with gravitational waves from the electroweak phase transition. The study establishes a connection of the scalar potential parameters, the thermodynamic properties of the phase transition, with the directly measured
stochastic gravitational-wave background in the presence of astrophysical background and foreground. Considering the space-based gravitational-wave detector Taiji, we construct a frequency-domain likelihood that incorporates instrumental and astrophysical noises, and we perform both Fisher-
matrix forecasts and
Bayesian nested sampling analysis. The comparison of these two approaches demonstrates consistent parameter recovery and highlights the sensitivity of Taiji to millihertz gravitational-wave signals. We further propagate the inferred constraints on the gravitational-wave spectrum back to the underlying CxSM parameters, obtaining meaningful limits on the
Higgs self-couplings. The results emphasize the complementarity between gravitational-wave observations and
collider measurements, showing that future missions such as Taiji can serve as a powerful probe of electroweak-scale new physics and the dynamical origin of the
Higgs sector.
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All authors Qingyuan Liang, Ligong Bian, Huai-Ke Guo, Yongcheng Wu
Astrophysics of Galaxies
Scalable and Robust Multiband Modeling of AGN Light Curves in Rubin-LSST
Weixiang Yu, John J. Ruan, Colin J. Burke et al. (+22 more)
The Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) will monitor tens of millions of active
galactic nuclei (AGNs) for a period of 10 years with an average cadence of 3 days in six broad photometric bands. This unprecedented
dataset will enable robust characterizations of AGN UV/optical variability across a wide range of AGN physical properties. However, existing tools for modeling AGN light curves are not yet capable of fully leveraging the volume, cadence, and multiband nature of LSST data. We present EzTaoX, a scalable light curve modeling tool designed to take advantage of LSST's multiband observations to simultaneously characterize AGN UV/optical
stochastic variability and measure interband time delays. EzTaoX achieves a speed increase of $\sim 10^2-10^4 \times$ on CPUs over current tools with similar capabilities, while maintaining equal or better accuracy in recovering simulated variability properties. This performance gain enables continuum time-delay measurements for all AGNs discovered by LSST – both in the Wide Fast Deep survey and the Deep Drilling Fields – thereby opening new opportunities to probe AGN
accretion-flow geometries. In addition, EzTaoX's multiband capability allows robust characterization of AGN
stochastic variability down to hourly timescales, facilitating the identification of accreting low-mass AGNs – such as those residing in
dwarf galaxies – through their distinctive variability signatures.
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All authors Weixiang Yu, John J. Ruan, Colin J. Burke, Roberto J. Assef, Tonima T. Ananna, Franz E. Bauer, Demetra De Cicco, Keith Horne, Lorena Hernández-García, Dragana Ilić, Vivek Kumar Jha, Andjelka B. Kovačević, Marcin Marculewicz, Swayamtrupta Panda, Claudio Ricci, Gordon T. Richards, Rogemar A. Riffel, Donald P. Schneider, Paula Sánchez-Sáez, Sarath Satheesh Sheeba, Francesco Tombesi, Matthew J. Temple, Michael S. Vogeley, Ilsang Yoon, Fan Zou
Cosmology and Nongalactic Astrophysics
Testing modified gravity with 3x2pt analyses in galaxy mocks
Marc Alemany-Gotor, Cristian Viglione, Pablo Fosalba et al. (+1 more)
Stage-IV surveys will enable unprecedented tests of
gravity on cosmological scales. However, assuming General Relativity in the analysis of large-scale structure could introduce systematic biases if
gravity deviates from GR at these scales. Modified
gravity theories, such as the Hu-Sawicki formulation of $f(R)$
gravity, offer an alternative explanation for
cosmic acceleration without invoking a cosmological constant, while remaining consistent with
Solar System tests through screening mechanisms. In this work, we quantify the cosmological parameter biases that arise when using a combination of
galaxy clustering and weak-
lensing data-vectors, the so-called 3x2pt analysis, from an $f(R)$
galaxy mock under the incorrect assumption of GR, using for the first time high-fidelity full-sky
galaxy mock catalogues. We employ a pair of twin simulations: one with GR and one with Hu–Sawicki $f(R)$
gravity with $|f_{R0}| = 10^{-5}$. The mocks are built using an HOD method to populate the dark matter
haloes with
galaxies, calibrated against SDSS observations at low
redshift. Using conservative scale cuts to minimise modelling uncertainties, we perform 3x2pt analyses and infer cosmological parameters through nested sampling, validating our pipeline with the GR mock. Our results show that when analysing the $f(R)$
galaxy mock assuming GR, the recovered cosmological parameters are very significantly biased, even when considering conservative scale cuts: the Figure of Bias reaches $\sim12\sigma$ for both $\{\Omega_{\rm m}, \sigma_8\}$ and $S_8$. These biases persist even when marginalising over the
galaxy bias and baryonic feedback, demonstrating that nuisance parameters cannot absorb the effects of modified
gravity. We conclude that incorrectly assuming GR in a universe governed by $f(R)$
gravity leads to severe and detectable biases in cosmological inference for Stage-IV surveys.
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All authors Marc Alemany-Gotor, Cristian Viglione, Pablo Fosalba, Isaac Tutusaus
High Energy Astrophysical Phenomena
Compton-induced $\gamma$-ray Cascade Emissions in Radio Galaxy NGC 1275
Mfuphi Ntshatsha, Markus Böttcher and Soebur Razzaque
Among active
galactic nuclei (AGNi), blazars are the brightest emitters of high-energy (HE, $E \geq 100$ MeV) to very-high-energy (VHE, $E \geq 100$ GeV) $\gamma$-rays from their jets.
Radio galaxies, being the misaligned parent population of the blazar class, were historically not detected at these frequencies. However, advances in experiments and observatories have led to their detection in the HE–VHE $\gamma$-ray band. In this work, we leverage and refine a Monte-Carlo
photon and electron-positron (e$^\pm$) pair tracking code in the AGN environment of the
radio galaxy NGC 1275. In the code, we consider the isotropic broad-line region (BLR) and anisotropic Shakura-Sunyaev (SS)
accretion disk radiation fields, with mild
magnetic fields in the AGN environment. We find that cascade $\gamma$-rays from inverse-Compton scattering by relativistic e$^\pm$ pairs of these external radiation fields can explain the
Fermi Large Area
Telescope's (LAT) and Major Atmospheric Cherenkov Experiment's observations from the
radio galaxy NGC 1275. We present a set of plausible parameters obtained from the code by fitting the source's spectral energy distribution (SED) during flaring events reported during the period December 2022 to January 2023.
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Earth and Planetary Astrophysics
Quantifying the differences in transmission and emission spectra for hot irradiated gaseous exoplanet atmospheres: A comparison of 1D and 3D modeling using JWST
Rahul Arora and Liton Majumdar
Modeling the atmospheres of
exoplanets is fundamental to understanding their atmospheric physics and chemical processes. While one-dimensional (1D) atmospheric models with 1D radiative transfer (RT) have been widely used, advances in three-dimensional (3D) general circulation models (GCMs) and 3D RT methods now allow quantitative comparisons of these approaches. With the precision and sensitivity of JWST, such differences can be observationally tested. This study investigates the spectral variations produced by 1D and 3D models and estimates the JWST observing time or number of transits needed to distinguish them. Using HD 189733b as a case study, three sets of simulations were performed: 1D atmospheric models with 1D RT and 3D GCM models coupled with both 1D and 3D RT. An inherent limitation of our study is that the temperature-pressure (T-P) profiles derived from the 3D GCM extend only to the high-pressure regions. The simulations incorporated both
equilibrium and disequilibrium chemistry. Significant spectral discrepancies were found, with 3D models generally showing weaker features. Using a JWST noise simulator, the signal-to-noise ratio (SNR) for detecting these differences was calculated. For transmission spectra, the SNR ranged from 2.04-7.68 (
equilibrium) and 1.66-7.04 (disequilibrium), while for emission spectra it ranged from 5.90-34.52 (
equilibrium) and 7.11-36.93 (disequilibrium). To test the limitations of the 3D GCM, we extended the atmosphere to lower pressures using an isothermal T-P profile and found wavelength-dependent variations in both the spectra and the SNR. These results show that JWST can distinguish 1D from 3D model spectra for major molecular features, underscoring the importance of 3D modeling in interpreting exoplanetary atmospheres.
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High Energy Astrophysical Phenomena
Probing the Nature of High-Redshift Long GRB 250114A and Its Magnetar Central Engine
Wen-Yuan Yu, Hou-Jun Lü, Xiao Tian et al. (+2 more)
GRB 250114A is a long-duration gamma-ray burst (GRB) which triggered the Swift/BAT with a spectroscopic high-
redshift at $z = 4.732$. The light curve of the
prompt emission is composed of three distinct emission episodes, which are separated by quiescent gaps ranging from tens to hundreds of seconds. While the X-ray light curve exhibits the canonical X-ray emission which is composed of several power-law segments superposition of a
giant X-ray
flare. More interestingly, there is still significant X-ray emission during the quiescent time in the
prompt emission, suggesting a continuously active central engine whose power fluctuates across the $\gamma$-ray detectability threshold. In this paper, we propose a magnetar as the central engine of GRB 250114A by fitting the X-ray light curve, and infer a
magnetic field strength $B_{\rm p}=13.24^{+1.73}_{-5.84} \, \times10^{15}\ \mathrm{G}$ and an initial
spin period $P_{0}=14.31^{+0.93}_{-3.16} \, \mathrm{ms}$ of magnetar, with a jet correction, fall within a reasonable range. Furthermore, we also compare the
prompt emission, X-ray afterglow, $E_{\mathrm p}$-$E_{\gamma,\mathrm{iso}}$, and $\varepsilon-$distribution of GBR 250114A with those of other high-$z$ sample-GRBs, and find no significant statistical differences between them.
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All authors Wen-Yuan Yu, Hou-Jun Lü, Xiao Tian, Liang-Jun Chen, En-Wei Liang
Cosmology and Nongalactic Astrophysics
Friction in Stochastic Inflation
Baptiste Blachier and Christophe Ringeval
We solve time-reversed
stochastic inflation in the semi-infinite flat potential with a constant drift term and derive an exact expression for the probability distribution of the
curvature fluctuations. It exhibits exponential decaying tails which contrast to the Levy-like power law behaviour encountered without friction. Such a non-vanishing drift acts as a regulator for the conventional “forward”
stochastic $\delta N$-formalism, which is otherwise ill-defined in the unbounded and flat potentials typical of plateau models of inflation. This setup therefore allows us to compare the
curvature distribution derived from both approaches, reverse and forward in time. Up to similar exponential tails, we find quantitative differences. In particular, in the classical-like limit of very large drift, the tails become Gaussian but only in the time-reversed picture. As a toy model of eternal inflation, we finally discuss the case of negative drift in which inflation never ends for many field trajectories. The forward approach becomes pathological whereas the reverse formalism gives back a finite
curvature distribution with always exponential tails. All these differences end up being related to the very definition of the background which is ambiguous when a classical trajectory does not exist.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Weak gravity at micron scales from dark bubble cosmology and its cosmological consequences
Ulf Danielsson and Suvendu Giri
The dark bubble model makes a positive cosmological constant natural in string theory, and predicts several new physical phenomena within reach in the near future. In this paper we study the experimental consequences of the model for the strength of
gravity at scales of order $10^{-5}$m. Contrary to other models of
gravity involving extra dimensions, the dark bubble model predicts
gravity to become weaker rather than stronger at small scales, compared to Newtonian
gravity. In particular, we provide explicit predictions of measurable deviations using table top experiments. We also show how the same effect reduces the effective force of
gravity at high energy densities in cosmology, leading to a period of early inflation without the need for anything beyond radiation. We also discuss the
quantum origin of the universe with a 5D black hole acting as a catalyst for the nucleation of the dark bubble and how it accounts for the present matter content in the universe. This leads to a prediction of $\Omega_c \approx 5\times 10^{-4}$ for a positive
curvature of the universe, suggesting an explanation of the why-now-problem of the cosmological constant. We end by speculating on how to incorporate AdS black shells as black hole mimickers within the dark bubble model.
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Solar and Stellar Astrophysics
Resonance locking and tidal evolution in rotating {\gamma}-Doradus binaries
L. Fellay, M.-A. Dupret and P. A. Kołaczek-Szymański
In binary systems, studying
tidal interactions is key to understanding the
evolution of binary populations. The primary dissipation process occurring in
stars with radiative envelopes is believed to be radiative damping of high-radial-order tidally excited oscillations, which is in agreement with observations of most binary systems. However, recent studies have suggested that outside this dissipation regime, dynamical tides can act in the opposite manner (a phenomenon known as inverse tides), and resonance locking could significantly impact the orbital
evolution of binary systems. We aim to study inverse tides and resonance locking by simultaneously including the effect of all the forcing frequencies and accounting for the effect of the rotation on the forced oscillations. We have developed an orbital
evolution code that is coupled to a
stellar oscillation code to compute on the fly the impact of dynamical tides on the rotational and orbital
evolution of binary systems including multiple simultaneous forcing frequencies. We find that resonance locking can be stable over a long period of time and a source of long-term exchange of angular momentum for rapidly rotating
stars. Long-term locking can increase the total angular momentum of a fast-rotating
star by approximately 70% during the main sequence. For slow-rotating
stars, resonance locking can slow down the rotational
evolution of the system over most of the main-sequence phase, even in the presence of strong
tidal interactions. This mechanism efficiently drives asynchronisation in binary systems where significant discrepancies already exist between the orbital and rotational frequencies.
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Earth and Planetary Astrophysics
Planet Migration in Protoplanetary Disks with Rims
Zhuoya Cao, Ya-Ping Li, Douglas N.C. Lin et al. (+1 more)
Complex structures, including sharp edges, rings and gaps, have been commonly observed in protoplanetary disks with or without planetary candidates. Here we consider the possibility that they are the intrinsic consequences of angular momentum transfer mechanisms, and investigate how they may influence the dynamical
evolution of embedded
planets. With the aid of numerical hydrodynamic simulations, we show that gas
giants have a tendency to migrate away from sharp edges, whereas super-Earths embedded in the annuli tend to be retained. This implies that, observationally, Jupiters are preferentially detected in dark rings (gaps), whereas super-Earths tend to be found in bright rings (density bumps). Moreover,
planets'
tidal torque provide, not necessarily predominant, feedback on the surface density profile. This tendency implies that Jupiter's gap-opening process deepens and widens the density gap associated with the dark ring, while super-Earths can be halted by steep surface density gradient near the disk or ring boundaries. 13Hence, we expect there would be a desert for super-Earths in the surface density gap.
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All authors Zhuoya Cao, Ya-Ping Li, Douglas N.C. Lin, Shude Mao
Earth and Planetary Astrophysics
Concurrent Accretion and Migration of Giant Planets in their Natal Disks with Consistent Accretion Torque (II): Parameter Survey and Condition for Outward Migration
JunPeng Pan, Ya-Ping Li, Yi-Xian Chen et al. (+2 more)
Migration typically occurs during the formation of
planets and is closely linked to the planetary formation process. In classical theories of non-accreting planetary migration, both type I and type II migration typically result in inward migration, which is hard to align with the architecture of the planetary systems.In this work, we conduct systematic, high-resolution 3D/2D numerical hydrodynamic simulations to investigate the migration of an accreting
planet. Under different disk conditions, we compared the dynamical
evolution of
planets with different
planet-to-
star mass ratios. We find that
accretion of
planets can significantly diminish the inward migration tendency of
planets, or even change the migration direction. The migration of low-/high-mass
planets is classified as Type I/II inward migration, respectively, while intermediate-mass
planets, which have the strongest
accretion, show an outward migration trend. We confirm that the outward migration is mainly attributed to the positive torque from the azimuthal asymmetric structures around the accreting
planet, similar to Li et al. (2024). The termination of planetary mass growth is thus synonymous with the transition from outward to inward migration. For the high viscosity $\alpha=0.04$ and disk aspect ratio height $h_0=0.05$ cases, the mass ratio range for planetary outward migration is $1\times10^{-4}\lesssim q\lesssim4\times10^{-3}$. For the low viscosity case with $\alpha=0.001$, and/or the low disk aspect ratio cases $h_0=0.03$, the mass ratio range for the outward migration will shift toward the lower end. Our parameter survey reveals that a simple gap opening parameter determines the outward migration condition; details of the analytical interpretation are presented in Ida et al. (2025).
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All authors JunPeng Pan, Ya-Ping Li, Yi-Xian Chen, Shigeru Ida, Douglas N. C. Lin