Solar and Stellar Astrophysics
Multi-band Photometric and spectroscopic analysis of the dwarf novae IU Leo
Y. H. Chen, C. M. Duan and H. Shu
IU Leo was first identified as a cataclysmic variable
star in 2006. Based on an image data and a distance value, we derived that the circumbinary envelope of IU Leo was $\sim$3,745\,AU on the optical band. According the multi-band photometric data, we calculated a $T_{eff}$ of a few hundred Kelvin for the circumbinary envelope of IU Leo. We reviewed the physical parameters of IU Leo and simulated the
evolution process using a
stellar evolution code MESA with $M_{1}$=0.982\,$M_{\bigodot}$, $M_{2}$=0.835\,$M_{\bigodot}$, and an orbital period of 0.376308\,days. The evolved other parameters are basically consistent with the parameters in the literatures. Based on the quiescence Kepler Mission 2.0 light curve, the quiescence Transiting
Exoplanet Survey Satellite light curve, and 89 Large Sky Area Multi-Object Fiber Spectroscopic
Telescope medium resolution spectra, we derived an orbital period of 0.376307 $\pm$ 0.000004\,days, 0.3762 $\pm$ 0.0001\,days, and 0.3763\,days for IU Leo respectively. These orbital periods are basically consistent with the results of previous studies. According to light curve of IU Leo from American Association of Variable
Star Observers, we reported three new outburst spectra from the Large Sky Area Multi-Object Fiber Spectroscopic
Telescope low resolution catalogue with part Balmer emission lines overlap on their absorption lines. Many H, He, C, N, O, Na, Mg, Si, and Ca neutral and ionized lines are identified, which are produced by different mechanisms. In the future, we will conduct more comprehensive and in-depth research on CVs based on multi-band photometric and spectroscopic data.
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Solar and Stellar Astrophysics
Unveiling the nature of HE 0107-5240
E. Caffau, M. Steffen, P. Molaro et al. (+27 more)
The vast majority of the most iron-poor
stars in the
Galaxy exhibit a strong carbon enhancement, with C/H ratios only about two orders of magnitude below
solar. This unusual chemical composition likely reflects the properties of the gas cloud from which these
stars formed, having been enriched by one, or at most a few,
supernovae. A remarkable member of this
stellar class, HE 0107-5240 with [Fe/H]=-5.56, has been identified as part of a binary system. To constrain its orbital parameters, radial velocity monitoring has been carried out using the ESPRESSO spectrograph. Radial velocities were derived using cross-correlation with a template, taking advantage of the strong G-band feature. Combining all observations yielded a high signal-to-noise spectrum, which has been used to refine our understanding of the
stellar chemical composition. Additionally, a co-added UVES spectrum in the blue was used to complement the wavelength coverage of ESPRESSO. Observations of HE 0107-5240 over a span of more than four years have yielded a revised orbital period of about 29 years. Updated elemental abundances have been determined for Sc, Cr, Co, and, tentatively, Al, along with a new upper limit for Be. The iron abundance has been derived from ionised Fe lines. Significant upper limits have been established for Li, Si, and Sr. The
star is confirmed to be a long-period binary. Iron abundances derived from neutral and ionised lines are consistent with local thermodynamical
equilibrium (LTE) assumption, casting doubt on published deviation from LTE corrections for Fe for this
star. The heavy elements Sr and Ba remain undetected, confirming the classification of HE 0107-5240 as a carbon enhanced metal-poor and non enhanced in heavy elements (CEMP-no)
star and supporting the absence of an n-capture element plateau at the lowest
metallicities.
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All authors E. Caffau, M. Steffen, P. Molaro, P. Bonifacio, N. Christlieb, D. S. Aguado, J. I. González Hernández, M. R. Zapatero Osorio, L. Monaco, M. Limongi, A. Chieffi, A. Falla, L. Roberti, A. J. Gallagher, M. Spite, P. François, H.-G. Ludwig, L. Sbordone, R. Lallement, C. Allende, R. Rebolo, S. Cristiani, G. Cupani, V. D'Odorico, C. J. A. P. Martins, D. Milaković, M. T. Murphy, N. J. Nunes, N. C. Santos, T. M. Schmidt
Solar and Stellar Astrophysics
On the influence of component orbital motion on the photometric variability of DF Tau
M.A. Burlak, K.N. Grankin, A.V. Dodin et al. (+6 more)
Based on the analysis of the long-term light curve of the young binary DF Tau spanning approximately 125 years, we infer that its brightness variations are associated with changes in the
accretion rate from the circumstellar protoplanetary disk onto the primary. We have also substantially improved the orbital parameters of DF Tau, which enables us to align its secular light curve with the
evolution of the binary's component separation. The relationship between the long-term brightness variations and the orbital motion of DF Tau, if present, appears to be inconsistent with theoretical predictions. Notably, similar discrepancies between theory and observations are also seen in other young binary systems. Furthermore, the source of the polarized radiation in the optical range is found to be located at a distance of $\lesssim 0.5^{\prime\prime}$ from the
star, with the polarization variability showing no dependence on the orbital phase.
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All authors M.A. Burlak, K.N. Grankin, A.V. Dodin, N.V. Emelyanov, N.P. Ikonnikova, Ya.A. Lazovik, S.A. Lamzin, B.S. Safonov, I.A. Strakhov
Earth and Planetary Astrophysics · Cross-listed from math.OC
Designing trajectories in the Earth–Moon system: a Levenberg–Marquardt approach
António Nunes, Sérgio Brás, Pedro Batista et al. (+1 more)
Trajectory design in cislunar space under a high-fidelity ephemeris model (HFEM) is pursued through a nonlinear optimization perspective anchored on the transition of solutions from lower fidelity models, namely the Circular Restricted Three-Body Problem (CR3BP). The optimization problem is posed in the likeness of a multiple-shooting approach, aiming for segment-to-segment continuity while tracking proximity to the original CR3BP structures. The analysis of various formulations leads to the selection of an unconstrained least-squares problem for further investigation. The nonlinear optimization problem is convexified and the use of the Levenberg–Marquardt
algorithm, as an alternative to the minimum-norm update equation found in most literature, is investigated for its control over the update step and inherent robustness. Additional techniques, such as adaptive weighting, are employed to further consolidate the behavior of the proposed
algorithm in challenging scenarios. Numerical trials evaluate the adequacy of the methodology presented and compare it to the minimum-norm baseline over various application cases, including the generation of quasi-periodic trajectories and orbital transfers between them. The proposed technique is found to be a suitable alternative to the minimum-norm scheme, generally retaining better proximity to the original CR3BP trajectories and providing benefits in numerical robustness and stability. Moreover, the ease of including proximity objectives in a relaxed manner is shown to facilitate control over the shape of the final converged solution.
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All authors António Nunes, Sérgio Brás, Pedro Batista, João Xavier
Astrophysics of Galaxies
Discovery of Repeating Transitions in 16 Changing-look Active Galactic Nuclei
Qian Dong, Zhi-Xiang Zhang, Wei-Min Gu et al. (+5 more)
The repeating changing-look active
galactic nuclei (RCL AGNs) exhibit multiple appearances and disappearances of broad emission lines (BELs), whose underlying mechanism remains a puzzle. Expanding the sample of RCL AGNs is valuable for constraining the transition timescale and probing the
accretion physics driving CL behaviors. This study aims to identify RCL AGNs using the multi-epoch spectroscopic data of confirmed CL AGNs from the Sloan Digital Sky Survey, Large Sky Area Multi-Object Fiber Spectroscopic
Telescope, and Dark Energy Spectroscopic Instrument, supplemented with mid-infrared (MIR) light curves. Through selection criteria and visual inspection, we identify 22 RCL AGNs among 299 CL AGNs, corresponding to an occurrence rate of about 7%, indicating that repeated transitions are not extremely rare in CL AGNs. Among the 22 RCL AGNs, 16 are newly identified, which significantly expands the known RCL AGN sample. Based on the spectra and densely sampled MIR light curves, we derive MIR variability timescales for 18 RCL AGNs, and find no significant correlation between the timescale and the black hole mass.
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All authors Qian Dong, Zhi-Xiang Zhang, Wei-Min Gu, Mouyuan Sun, Wei-Jian Guo, Zhen-Yi Cai, Jun-Xian Wang, Yong-Gang Zheng
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Causality as a guiding principle for physics beyond General Relativity
Gerardo García-Moreno
This thesis is situated within the context of
quantum gravity, broadly understood as any effort to explore the interplay between gravitation and the
quantum realm, without necessarily requiring the quantization of the gravitational field itself. We focus on emergent theories, particularly those in which the causal structure and
geometric concepts underlying the gravitational field in General Relativity are not fundamental but instead arise from more basic underlying degrees of freedom. Our
attention is directed toward emergent approaches inspired by condensed matter physics. Rather than developing a full-fledged emergent theory and analyzing its detailed consequences, this work offers a concise roadmap of analyses and reflections relevant to emergent frameworks, without committing to any specific model. The thesis is divided into two parts, reflecting the distinct tools and analyses employed in each. The first addresses fundamental and conceptual aspects of emergent theories, focusing on the role of background structures, both regarding their implications for the theory and their constructive relevance. The second assumes the absence of singularities and horizons, a feature often expected in emergent frameworks, though the analyses remain agnostic and independent of specific theoretical commitments.
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Astrophysics of Galaxies
Head-tail molecular clouds falling onto the Milky Way disk
Mikito Kohno, Yasuo Fukui, Takahiro Hayakawa et al. (+13 more)
We report discovery of two CO clouds which are likely falling down to the
Galactic plane at more than $35$ km s$^{-1}$. The clouds show head-tail distributions elongated perpendicular to the
Galactic plane at $l=331.6^{\circ}$ and $b=0^{\circ}$ as revealed by an analysis of the Mopra CO $J=$1-0 survey data. We derived the distance of the clouds to be $2.46 \pm 0.18$ kpc based on the
Gaia Data Release 3. The CO clouds have molecular masses of $4.8\times 10^3\ M_{\odot}$ and $3.5\times 10^3\ M_{\odot}$, respectively, and show kinetic temperature of 30-50 K as derived from the line intensities of the $^{13}$CO $J$=2-1, $^{12}$CO $J$=1-0, and $^{13}$CO $J$=1-0 emission. The temperature in the heads of the clouds is significantly higher than 10 K of the typical molecular clouds, although no radiative heat source is found inside or close to the clouds. Based on the results, we interpret that the present clouds are falling onto the Milky Way disk and are significantly heated up by the strong shock interaction with the disk HI gas. We suggest that the clouds represent part of the HI intermediate velocity clouds falling to the
Galactic plane which were converted into molecular clouds by shock compression. This is the first case of falling CO clouds having direct observed signatures of the falling motion including clear directivity and shock heating. Possible implications of the CO clouds in the
evolution of the
Galactic interstellar medium are discussed.
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All authors Mikito Kohno, Yasuo Fukui, Takahiro Hayakawa, Yasuo Doi, Rin I. Yamada, Fumika Demachi, Kazuki Tokuda, Hidetoshi Sano, Shinji Fujita, Rei Enokiya, Asao Habe, Kisetsu Tsuge, Atsushi Nishimura, Masato I.N. Kobayashi, Hiroaki Yamamoto, Kengo Tachihara
Astrophysics of Galaxies
A Census of Double-Peaked Lyman-alpha Emitters in MAGPI: Classification, Global Characteristics, and Spatially Resolved Properties
Tamal Mukherjee, Tayyaba Zafar, Themiya Nanayakkara et al. (+17 more)
Double-peaked Ly$\alpha$ profiles provide critical insights into gas kinematics and the distribution of neutral hydrogen (HI) from the interstellar to the intergalactic medium (ISM to IGM), and serve as valuable diagnostics of ionising Lyman continuum (LyC)
photon escape. We present a study of the global and spatially resolved properties of double-peaked Ly$\alpha$ emitters (LAEs) based on VLT/MUSE data from the MAGPI survey. From a parent sample of 417 LAEs at z = 2.9 - 6.6 in the first 35 fields, we identify 108 double-peaked LAEs using an automated peak classification technique. We measure a double-peak fraction of $\sim37\%$ at $z < 4$, decreasing to $\sim14\%$ at $z > 4$, likely due to enhanced IGM attenuation. Approximately $17\%$ of the double-peaked LAEs are blue-dominated, possibly tracing gas inflows, though backscattering remains a viable alternative for sources without systemic
redshift. The blue-to-total flux ratio exhibits a luminosity dependence: fainter lines generally show higher blue flux. We find a narrowing of the red peak at $z > 4$, despite the presence of the blue peak, indicating intrinsic
galaxy evolution rather than IGM attenuation. Several LAEs exhibit residual flux in the absorption trough, with normalised trough flux anticorrelating with peak separation, reflecting variations in HI column density. We further investigate spatially resolved properties of ten red-dominated LAEs with extended Ly$\alpha$
halos. Despite azimuthal variations, both the blue-to-total flux ratio and normalised trough flux density increase with radius, while peak separation decreases. The red peak asymmetry shows only minor radial changes. These trends are consistent with variations in shell
outflow velocity and HI column density across the
halos. Based on peak separation, red peak asymmetry, and residual trough flux, we identify five LAEs as strong LyC-leaker candidates.
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All authors Tamal Mukherjee, Tayyaba Zafar, Themiya Nanayakkara, Siddhartha Gurung-Lopez, Anshu Gupta, Scott M. Croom, Andrew Battisti, Karl Glazebrook, Polychronis Papaderos, Melissa Riggs, Emily Wisnioski, Caroline Foster, Katherine E. Harborne, Claudia D. P. Lagos, Trevor Mendel, Jahang Prathap, Stefania Barsanti, Sarah M. Sweet, Lucas M. Valenzuela, Anilkumar Mailvaganam
Earth and Planetary Astrophysics · Cross-listed from physics.flu-dyn
Non-linear evolution of the horizontal shear instability in stratified rotating fluids under the complete Coriolis acceleration
Camille Moisset, Paul Billant, Junho Park et al. (+1 more)
This paper investigates the non-linear dynamics of horizontal shear instability in an incompressible, stratified and rotating fluid in the non-traditional $f$-plane, i.e. with the full Coriolis acceleration, using direct numerical simulations. The study is restricted to two-dimensional horizontal perturbations. It is therefore independent of the vertical (traditional) Coriolis parameter. However, the flow has three velocity components due to the horizontal (non-traditional) Coriolis parameter. Three different scenarios of non-linear
evolution of the shear instability are identified, depending on the non-dimensional Brunt-Väisälä frequency $N$ and the non-dimensional non-traditional Coriolis parameter $\tilde{f}$ (non-dimensionalized by the maximum shear), in the range $\tilde{f}<N$ for fixed Reynolds and Schmidt numbers $Re=2000$, $Sc=1$. When the stratification is strong $N\gg 1$, the shear instability generates stable Kelvin-Helmholtz billows like in the traditional limit $\tilde{f}=0$. Furthermore, when $N\gg1$, the governing equations for any $\tilde{f}$ can be transformed into those for $\tilde{f}=0$. This enables us to directly predict the characteristics of the flow depending on $\tilde{f}$ and $N$. When $N$ is around unity and $\tilde{f}$ is above a threshold, the primary Kelvin-Helmholtz
vortex is destabilised by secondary instabilities but it remains coherent. For weaker stratification, $N\leqslant0.5$ and $\tilde{f}$ large enough, secondary instabilities develop vigorously and destroy the primary
vortex into small-scales
turbulence. Concomitantly, the enstrophy rises to high values by stretching/tilting as in fully three-dimensional flows. A local analysis of the flow prior to the onset of secondary instabilities reveals that the Fjortoft necessary condition for instability is satisfied, suggesting that they correspond to shear instabilities.
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All authors Camille Moisset, Paul Billant, Junho Park, Stéphane Mathis
Earth and Planetary Astrophysics
Acceleration of planetary migration: Resonance crossing and planetesimal ring
Hailiang Li, Li-Yong Zhou and Xiaoping Zhang
Planetary migration is a crucial stage in the early
solar system, explaining many observational phenomena and providing constraints on details related to the
solar system's origins. This paper aims to investigate the acceleration during planetary migration in detail using numerical simulations, delving deeper into the early
solar system's preserved information. We confirm that planetary migration is a positive feedback process: the faster the migration, the more efficient the consumption of planetesimals; once the migration slows down, Neptune clears the surrounding space, making further migration more difficult to sustain. Quantitatively, a tenfold increase in migration rate corresponds to an approximately 30% reduction in the mass of planetesimals consumed to increase per unit angular momentum of Neptune. We also find that Neptune's final position is correlated with the initial surface density of planetesimals at that location, suggesting that the disk density at 30au was approximately 0.009$M_{\oplus}/au^2$ in the early
solar system. Two mechanisms that can accelerate planetary migration are identified: the first is MMR between Uranus and Neptune. Migration acceleration will be triggered whenever these two
giant planets cross their major MMR. The second mechanism is the ring structure within the planetesimal disk, as the higher planetesimal density in this region can provide the material support necessary for migration acceleration. Our research indicates that Neptune in the current
solar system occupies a relatively delicate position. In case Neptune crossed the 1:2 MMR with Uranus, it could have migrated to a much more distant location. Therefore, under the influence of the positive feedback mechanism, the
evolution of the
solar system to its current configuration might be a
stochastic outcome rather than an inevitable consequence.
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Astrophysics of Galaxies
The selection function of the Gaia DR3 open cluster census
Emily L. Hunt, Tristan Cantat-Gaudin, Friedrich Anders et al. (+4 more)
Open clusters are among the most useful and widespread tracers of
Galactic structure. The completeness of the
Galactic open cluster census, however, remains poorly understood. For the first time ever, we establish the selection function of an entire open cluster census, publishing our results as an open-source Python package for use by the community. Our work is valid for the Hunt & Reffert catalogue of clusters in
Gaia DR3. We developed and open-sourced our cluster simulator from our first work. Then, we performed 80,590 injection and
retrievals of simulated open clusters to test the Hunt & Reffert catalogue's sensitivity. We fit a logistic model of cluster detectability that depends only on a cluster's number of
stars, median parallax error,
Gaia data density, and a user-specified significance threshold. We find that our simple model accurately predicts cluster detectability, with a 94.53% accuracy on our training data that is comparable to a machine-learning based model with orders of magnitude more parameters. Our model itself offers numerous insights on why certain clusters are detected. We briefly use our model to show that cluster detectability depends on non-intuitive parameters, such as a cluster's proper motion, and we show that even a modest 25 km/s boost to a cluster's orbital speed can result in an almost 3$\times$ higher detection probability, depending on its position. In addition, we publish our raw cluster injection and
retrievals and cluster memberships, which could be used for a number of other science cases – such as estimating cluster membership incompleteness. Using our results, selection effect-corrected studies are now possible with the open cluster census. Our work will enable a number of brand new types of study, such as detailed comparisons between the Milky Way's cluster census and recent extragalactic cluster samples.
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All authors Emily L. Hunt, Tristan Cantat-Gaudin, Friedrich Anders, Sagar Malhotra, Lorenzo Spina, Alfred Castro-Ginard, Lorenzo Cavallo
Cosmology and Nongalactic Astrophysics
The implications of inflation for the last ACT
Zhi-Chong Qiu, Ye-Huang Pang and Qing-Guo Huang
We explored a parameterized slow-roll inflationary model within the $\Lambda$CDM framework, utilizing a combination of data from Planck 2018, ACT DR6, DESI DR2, and BICEP/Keck 2018 (P-ACT-LB-BK18). Additionally, we incorporated the SH0ES prior on $H_0$ (P-ACT-LB-BK18-$H_0$) to analyze the model within the early dark energy (EDE) framework. While the model with a potential $V(\phi)\propto \phi^\alpha$ for small values of $\alpha$ still fits the data, the Starobinsky $R^2$ inflation falls outside the $2\sigma$ region. On the other hand, in a self-consistent
quantum theory of
gravity, higher-order corrections to $R$ are typically anticipated. In response, we proposed a non-perturbative exponential $f(R)$ inflation model, wherein the subleading corrections beyond $R^2$ including terms like $R^3$ or $R^4$. Using numerical calculations and Markov Chain Monte Carlo (MCMC) analysis with the P-ACT-LB-BK18 data set, we demonstrate that this model can align well with the ACT-preferred value of the scalar spectral index. Additionally, within the early dark energy (EDE) framework, it accommodates greater deviations from the original Starobinsky $R^2$ inflation model when incorporating the SH0ES prior on $H_0$.
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High Energy Astrophysical Phenomena
Comparative Statistical Analysis of Prompt and Afterglow X-Ray Flares in Gamma-Ray Bursts: Insights into Extended Central Engine Activity
Yinuo Ma and He Gao
Gamma-ray bursts (GRBs) are the most energetic phenomena in the Universe, characterized by
prompt gamma-ray emission followed by multiwavelength afterglows. X-ray
flares, observed during the afterglow phase, are generally believed to originate from the prolonged activity of the central engine, though direct evidence has been scarce. In this study, we present a comprehensive statistical analysis of X-ray
flares from 315 GRBs observed by the Swift/X-ray
Telescope over nearly two decades. We categorize
flares into
prompt flares (occurring during the
prompt emission phase) and afterglow
flares and compare their temporal and luminosity properties. Our analysis reveals that both types of
flares exhibit similar morphological characteristics, with
prompt flares being brighter and occurring earlier than afterglow
flares. We find strong correlations between
flare parameters, such as peak time, duration, and luminosity, which follow consistent patterns across both
flare types. These findings suggest that X-ray
flares, regardless of their timing, share a common origin in the central engine's activity. Our results imply that the central engine's activity duration extends beyond the
prompt gamma-ray emission phase, highlighting the importance of considering X-ray
flares when studying GRB progenitors and central engine properties. This work provides robust statistical evidence supporting the central engine origin of X-ray
flares and underscores the need for future observations with missions like the Space-based multi-band astronomical Variable Objects Monitor and Einstein Probe to further elucidate the nature of GRB central engines.
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Cosmology and Nongalactic Astrophysics
The $\mathtt{WebSky}$ $\mathrm{[CII]}$ Forecasts and the search for primordial intermittent non-Gaussianity
Nathan J. Carlson, J. Richard Bond, Dongwoo T. Chung et al. (+2 more)
We present the $\mathtt{WebSky}$ $\mathrm{[CII]}$ line-intensity mock maps and forecast the capabilities of upcoming wide-field submillimeter-wave surveys of cosmological $\mathrm{[CII]}$ emission from the epoch of reionization (EoR). Using the $\mathtt{Peak~Patch}$
algorithm to generate light-cone dark matter (DM)
halo catalogues and the $\mathtt{WebSky}$ framework to forward-model the cosmological $\mathrm{[CII]}$ signal, we construct tomographic mock surveys matched to the CCAT Observatory. We investigate both astrophysical models of $\mathrm{[CII]}$ emission from interstellar gas and the potential for the study of
primordial intermittent non-Gaussianity (PING) as a science case for Stage 2 line intensity mapping (LIM) surveys. The $\mathrm{[CII]}$ voxel intensity distribution (VID) is used as a summary statistic in forecasts. Additional constraints on PING are derived from a relative
entropy study of $\mathtt{Peak~Patch}$
halo mass functions. We show that upcoming LIM surveys will provide insights into the way we model cosmological line emission, and next-generation surveys can place competitive bounds on novel inflationary scenarios such as PING. The $\mathtt{WebSky}$ $\mathrm{[CII]}$ mocks and corresponding $\mathtt{Peak~Patch}$
halo catalogues are publicly available at https://uoft.me/webskycii .
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All authors Nathan J. Carlson, J. Richard Bond, Dongwoo T. Chung, Patrick Horlaville, Thomas Morrison
Astrophysics of Galaxies
Variance of dust temperature and spectral index in Planck polarization data using spin-moment expansion
Vincent Guillet, Léo Vacher, Jonathan Aumont et al. (+4 more)
Thermal
dust is the major polarized foreground hindering the detection of
primordial cosmic microwave background (CMB) B-modes. Its signal exhibits complex behavior in frequency space, arising from the combined variation in our
Galaxy of the orientation of
magnetic fields and the spectral properties of
dust grains aligned with
magnetic field lines. In this work, we present a new framework for analyzing the thermal
dust signal using polarized microwave data. We introduce residual maps, represented as complex quantities, which capture deviations of the local polarized spectral energy distribution (SED) from the mean complex SED averaged over the sky mask. We present simple predictions that relate the values of the statistical correlation and covariances between the residual maps to the physical properties of the emitting aligned grains. Testing these predictions provides valuable information about the nature of the
dust signal. We evaluated our predictions using Planck data over a 97% mask excluding the inner
Galactic plane. Despite its simplicity, our model captures a significant part of the statistical properties of the data. For the SRoll2 version of the data, the spectral dependence of the covariances between residual maps is compatible with a
dust model that includes only temperature variations rather than spectral index variations. In contrast, for the PR4 Planck official release, it is incompatible with both models. Our methodology can be used to analyze future high-precision polarization data and to build more accurate
dust models for use by the CMB community.
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All authors Vincent Guillet, Léo Vacher, Jonathan Aumont, François Boulanger, Alessia Ritacco, Jean-Marc Delouis, Andrea Bracco
Solar and Stellar Astrophysics
The Growth of the Central Black Holes in Quasi-stars
Jake Hassan, Rosalba Perna, Matteo Cantiello et al. (+3 more)
Observations by JWST have confirmed the presence of supermassive black holes (BHs) at
redshifts $z\gtrsim10$, lending support to scenarios in which BHs experience rapid growth through intense gas
accretion. Here we investigate the growth of a BH embedded at the center of a quasi-
star, a theoretically predicted object formed via direct collapse. In a quasi-
star, the central BH accretes at a highly super-Eddington rate, while the excess energy is transported outward by convection and radiated at approximately the Eddington luminosity of the entire
star. We employ the open-source
stellar evolution code MESA to construct quasi-
star models and follow the time-dependent growth of the central BH under different prescriptions for the
accretion rate at the inner boundary $R_i$, and further considering the effect of winds. For the case $R_i=NR_{\rm B}$, where $N$ is a constant and $R_{\rm B}$ is the Bondi radius corresponding to the mass of the BH and the gas infalling onto it, our models terminate when the BH mass reaches a critical value $M_{\mathrm{crit}}(N)=c_{s,i}^3/(12\sqrt{N^3G^3\pi\rho_i})$ (where $c_{s,i}$ and $\rho_i$ are the sound speed and density at $R_i$, respectively), a limit we also derive analytically. Models that feature an inner convective region matched to an outer adiabatic envelope exhibit BH growth up to approximately $M_{\mathrm{BH}}/M_\star\simeq 0.33$, largely independent of the
stellar mass $M_\star$ itself. This ratio is approximately preserved even in the presence of mass loss, as several properties of the model are independent of the quasi-
star's total mass.
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All authors Jake Hassan, Rosalba Perna, Matteo Cantiello, Philip Armitage, Mitchell Begelman, Taeho Ryu
Solar and Stellar Astrophysics
Sympathetic Eruption of Two Filaments and Associated Solar Coronal Jet
Jiayan Yang, Leping Li, Huadong Chen et al. (+4 more)
Combining the high-quality observations from the
Solar Dynamics Observatory (SDO), the Global Oscillation Network Group (GONG), and the Chinese H$\alpha$
Solar Explorer (CHASE), we report a
solar coronal jet triggered by the sympathetic eruption of two filaments on 2024 January 11. Initially, the western segment of an active region filament erupted. The erupting
plasma propagated eastward, approximately along the filament's axis. This eruption perturbed the
magnetic field of a second filament situated near its eastern footpoint, the second filament then erupted sympathetically about one hour later. The eruption of the second filament is a failed one, with the majority of the filament material falling back after the initial lifting. Although no GOES
flare accompanied these filament eruptions, distinct brightenings were observed following each eruption. The second eruption produced a large coronal jet, which propagated along a bent trajectory with an apparent deflection angle of approximately 90 degrees. No clear evidence of
magnetic reconnection was detected at the deflection site, thus we suspect that the jet may have traveled along an S-shaped trans-equatorial loop and shown a curved trajectory. This event exhibits multiple phenomena: partial filament eruption, failed filament eruption, sympathetic filament eruption, jet initiation by filament eruption, and apparently deflected jet propagation. Collectively, these observations highlight the complexity and diversity of
solar activity.
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All authors Jiayan Yang, Leping Li, Huadong Chen, Yi Bi, Bo Yang, Junchao Hong, Yan Dong
Astrophysics of Galaxies
On the consistency of jet feedback modelling across different astrophysics hydrodynamical codes
N. Maragkakis, M. A. Bourne, C. Power et al. (+3 more)
Active
Galactic Nuclei (AGN) feedback is essential in cosmological simulations of
galaxy formation, yet its implementation has to rely on subgrid models due to limited resolution. We present a novel subgrid jet-launching method for
galaxy formation simulations and implement it in three hydrodynamical codes: the smoothed particle hydrodynamics (SPH) code SWIFT, the moving-mesh code AREPO, and the Eulerian grid code PLUTO. To isolate the impact of hydrodynamical solvers on jet
evolution, we compare idealised jets and their remnants in uniform and stratified media across resolutions and jet parameters. In uniform media, all jets drive bow shocks, inflate hot lobes, exhibit backflows, and evolve self-similarly. For the parameters explored, SWIFT lobes are shorter, wider, and hotter; AREPO lobes are longer, thinner, and cooler; while PLUTO lobes display complex flows with intermediate characteristics. In stratified media, jets deviate from self-similar
evolution, inflating longer and thinner lobes due to lower external ram pressure. After switch-off, SWIFT jets evolve into smooth cylindrical bubbles, AREPO jets produce long filamentary remnants, and PLUTO jets yield intermediate-length remnants with varying degrees of mixing. Despite such differences, all jets and remnants have a similar impact on the ambient medium. We conclude that variations in lobe properties between codes emerge even for identical subgrid prescriptions, since the coupling of jet feedback to resolvable scales and the effective resolution depend on the hydrodynamical method. In structure formation simulations, these solver differences are likely subdominant to uncertainties in subgrid modelling and calibration, while averaging over
galaxy populations may lessen their impact.
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All authors N. Maragkakis, M. A. Bourne, C. Power, F. Huško, A. Ludlow, S. Shabala
High Energy Astrophysical Phenomena · Cross-listed from physics.comp-ph
Special Relativistic Smoothed Particle Hydrodynamics Based on Riemann Solver
Kanta Kitajima, Shu-ichiro Inutsuka and Izumi Seno
This paper proposes a novel numerical method based on Godunov Smoothed Particle Hydrodynamics for special relativistic fluid dynamics. Our method utilizes a Riemann solver to describe shock, enhancing accuracy in strong shock waves. The formulation maintains conservation laws and achieves higher accuracy through convolution integrals that define physical quantities for SPH particles. We also propose the number density calculation method that uses a non-equal
baryon number in each SPH particle and variable smoothing length in a way different from the conventional method. Numerical experiments demonstrate the method's robustness across one- and two-dimensional relativistic shock tube problems, as well as its ability to simulate Kelvin-Helmholtz instabilities accurately, validating SRGSPH as a reliable approach for high-resolution relativistic simulations.
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Astrophysics of Galaxies
The ALPINE-CRISTAL-JWST Survey: Stellar and nebular dust attenuation of main-sequence galaxies at z~4-6
Akiyoshi Tsujita, Seiji Fujimoto, Andreas Faisst et al. (+39 more)
Characterizing
dust attenuation is crucial for revealing the intrinsic physical properties of
galaxies. We present an analysis of
dust attenuation in 18 spectroscopically confirmed
star-forming main-sequence
galaxies at $z = 4.4-5.7$ observed with JWST/NIRSpec IFU and NIRCam, selected from the ALPINE and CRISTAL ALMA large programs. We fit the emission line fluxes from NIRSpec and the broad-band photometry from NIRCam with Prospector, using both spatially integrated emission and $\sim0.6$ kpc pixel-by-pixel measurements. We derive the
stellar-to-nebular
dust attenuation ratio ($f=E(B-V)_{\mathrm{star}}/E(B-V)_{\mathrm{neb}}$) from the SED fits and the Balmer decrement with H$\alpha$ and H$\beta$. Although individual
galaxies show large scatter, the best-fit value is $f = 0.51^{+0.04}_{-0.03}$, slightly higher than that measured for local starburst
galaxies. We find weak correlations of $f$ with
galaxy properties, increasing with higher specific
star-formation rates, younger
stellar ages, and more recent
star-formation. For the range of $E(B-V)_{\mathrm{star}} = 0.009-0.15$ mag for in our sample, assuming $f = 1$ (often adopted in high-
redshift studies) instead of $f = 0.51$ underestimate line luminosities and ionizing
photon production efficiency $\xi_\text{ion}$ by $\sim3-36\%$ and $\sim4-46\%$, respectively. We also find that the total
stellar masses estimated from spatially-integrated SED fits with a delayed-$\tau$
star-formation histories are systematically smaller than the sum of pixel-by-pixel SED fits, with a median offset of $\sim 0.26$ dex, likely because the integrated fits are biased toward luminous young
stellar populations.
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All authors Akiyoshi Tsujita, Seiji Fujimoto, Andreas Faisst, Meédéric Boquien, Juno Li, Andrea Ferrara, Andrew J. Battisti, Poulomi Dam, Manuel Aravena, Matthieu Béthermin, Caitlin M. Casey, Olivia R. Cooper, Steven L. Finkelstein, Michele Ginolfi, Diego A. Gómez-Espinoza, Ali Hadi, Rodrigo Herrera-Camus, Edo Ibar, Hanae Inami, Gareth C. Jones, Anton M. Koekemoer, Kotaro Kohno, Brian C. Lemaux, Ilse De Looze, Ikki Mitsuhashi, Juan Molina, Ambra Nanni, Francesca Pozzi, Naveen A. Reddy, Monica Relano, Giulia Rodighiero, Michael Romano, David B. Sanders, Prasad Sawant, Manuel Solimano, Laura Sommovigo, Justin Spilker, Ken-ichi Tadaki, Livia Vallini, Vicente Villanueva, Wuji Wang, Giovanni Zamorani
Cosmology and Nongalactic Astrophysics
SKYSURF-11: A New Zodiacal Light Model Optimized for Optical Wavelengths
Rosalia O'Brien, Richard G. Arendt, Rogier A. Windhorst et al. (+15 more)
We present an improved zodiacal light model, optimized for optical wavelengths, using archival Hubble Space
Telescope (HST) imaging from the SKYSURF program. The Kelsall et al. 1998 model used infrared imaging from the Diffuse Infrared Background Experiment (DIRBE) on board the
Cosmic Background Explorer to create a 3D structure of the interplanetary
dust cloud. However, this model cannot accurately represent zodiacal light emission outside of DIRBE's nominal wavelength bandpasses, the bluest of which is 1.25 micron. We present a revision to this model (called ZodiSURF) that incorporates analytical forms of both the scattering phase function and albedo as a function of wavelength, which are empirically determined across optical wavelengths (0.3-1.6 micron) from over 5,000 HST sky surface brightness (sky-SB) measurements. This refined model results in significantly improved predictions of zodiacal light emission at these wavelengths and for Sun angles greater than 80 deg. Fits to HST data show an uncertainty in the model of ~4.5%. Remarkably, the HST sky-SB measurements show an excess of residual diffuse light (HST Sky - ZodiSURF - Diffuse
Galactic Light) of 0.013 +/- 0.006 MJy/sr. We suggest that a very dim spherical
dust cloud may need to be included in the zodiacal light model, which we present here as a toy model.
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All authors Rosalia O'Brien, Richard G. Arendt, Rogier A. Windhorst, Tejovrash Acharya, Annalisa Calamida, Timothy Carleton, Delondrae Carter, Seth H. Cohen, Eli Dwek, Brenda L. Frye, Rolf A. Jansen, Scott J. Kenyon, Anton M. Koekemoer, John MacKenty, Megan Miller, Rafael Ortiz III, Peter C. B. Smith, Scott A. Tompkins
Astrophysics of Galaxies
Milky Way Mass Through Escape Velocity Curve from LAMOST K Giants
Yin Wu, Haining Li, Yang Huang et al. (+2 more)
Escape velocity has long been used to constrain the mass of the Dark Matter (DM)
halo in the Milky Way (MW). Here we present a study of the escape velocity curve using a sample of high-velocity K
giants with full 6D phase-space information and relatively good quality, selected from LAMOST DR8 and cross-matched with
Gaia DR3. To expand the high-velocity
stars to larger distances, we used radius-dependent criteria of total velocity, that is, $v_{\rm GC}>300\;\rm{km s^{-1}}$ for the
solar neighborhood; $v_{\rm GC}>v_{\rm min}\sim0.6\times v_{\rm esc}(r_{\rm GC})$ for outer region. We also selected
halo stars based on $v_{\phi}-{\rm [Fe/H]}$ information to ensure that the sample is isotropic. We modeled the velocity distribution with traditional power-law models to determine the escape velocity in each radial bin. For the first time, we have directly measured a relatively continuous escape velocity curve that can extend to Galactocentric radii of $\sim 50$ kpc, finding a decline in agreement with previous studies. The escape velocity at the
solar position yielded by our measurements is $523.74^{+12.83}_{-13.47}\;\rm{km s^{-1}}$. Combined with the local circular velocity, we estimated the mass of the MW assuming a Navarro-Frenk-White DM profile, which resulted in a total mass of $M_{200,\;\rm{total}}=0.90_{-0.07}^{+0.06}\times 10^{12}\;M_{\odot}$, with a concentration of $c_{200}=13.47_{-1.70}^{+1.85}$. The small uncertainty implies that including the escape velocities beyond the
solar neighborhood can result in a more precise mass estimate. Our derived MW mass is consistent with some recent studies using the escape velocity as well as other tracers, which may support a lower mass of the DM
halo than in the past.
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All authors Yin Wu, Haining Li, Yang Huang, Xiang-Xiang Xue, Gang Zhao
High Energy Astrophysical Phenomena
The Origin of Cross-Energy-Similar FRED Profiles in Gamma-Ray Bursts Pulses
Shu-Xu Yi, Chen-Wei Wang, Shao-Lin Xiong et al. (+5 more)
To understand the physical mechanisms underlying the
prompt emission of gamma-ray bursts (GRB), single FRED (Fast-Rise-Exponential-Decay) profile GRBs serve as an ideal sample, as they origin from single epoch central engine activity. These GRBs have been found to exhibit a peculiar morphology-including the elegant cross-energy-similarity across energy bands and the recently discovered composite nature-challenging nearly all existing radiation mechanisms, sparking widespread curiosity about their origins. Here we propose a physical model which includes radiation locations sequentially triggered by propagating
magnetic perturbations. It naturally explains all observed properties of these GRBs, including the self-similar FRED profile, multi-band aligned subpulses, hard-to-soft spectral
evolution, local intensity tracking, and increasing subpulse durations. Furthermore, our results demonstrate that the duration of these GRBs is not reflecting the activity timescale of the central engine, reconciling recent challenges to the traditional merger-short/collapsar-long dichotomy of GRBs.
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All authors Shu-Xu Yi, Chen-Wei Wang, Shao-Lin Xiong, Shuang-Nan Zhang, Romain Maccary, Rahim Moradi, Shuo Xiao, Hua Feng
Instrumentation and Methods for Astrophysics
Spectroscopic study of the light-polluted night sky in Hong Kong
Chu Wing So, Chun Shing Jason Pun and Shengjie Liu
Spectroscopic study of the night sky has been a common way to assess the impacts of artificial light at night at remote astronomical observatories. However, the spectroscopic properties of the urban night sky remain poorly documented. We addressed this gap by collecting more than 12,000 zenith sky spectra with compact spectrometers at urban and suburban sites from 2021 to 2023. Here, by examining the intensity variations of the spectral features that represent characteristic emissions from common artificial light sources, we show that the skyglow is predominantly shaped by artificial emissions, including compact fluorescent lamps and high-pressure sodium lamps. Contributions from commercially controlled lighting, including those for floodlighting and advertising adopting light-emitting diode and metal halide technologies, were more pronounced in urban areas during the hours leading up to midnight. We also documented direct evidence of the impact of a neon sign located on top of a commercial tower, illustrating how a single light source can significantly influence the surrounding environment. Compared with observations made a decade ago at the same location, our findings indicate a growing popularity of light-emitting diode lighting for external use, consistent with the existing literature. This first comprehensive spectroscopic investigation of light pollution in an urban environment emphasizes the evolving patterns of outdoor lighting and highlights the critical and unique role of spectroscopic measurements. The results provide essential information for the development of effective strategies and policies to mitigate light pollution in urban areas and at sites of astronomical importance.
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High Energy Astrophysical Phenomena
Electron Acceleration via Lower-Hybrid Drift Instability in Astrophysical Plasmas: Dependence on Plasma Beta and Suprathermal Electron Distributions
Ji-Hoon Ha and Elena S. Volnova
Density inhomogeneities are ubiquitous in space and astrophysical
plasmas, particularly at
magnetic reconnection sites, shock fronts, and within compressible
turbulence. The gradients associated with these inhomogeneous
plasma regions serve as free energy sources that can drive
plasma instabilities, including the lower-hybrid drift instability (LHDI). Notably, lower-hybrid waves are frequently observed in magnetized space
plasma environments, such as Earth's magnetotail and magnetopause. Previous studies have primarily focused on modeling particle acceleration via LHDI in these regions using a quasilinear approach. This study expands the investigation of LHDI to a broader range of environments, spanning weakly to strongly magnetized media, including interplanetary, interstellar, intergalactic, and intracluster
plasmas. To explore the applicability of LHDI in various astrophysical settings, we employ two key parameters: (1)
plasma magnetization, characterized by the
plasma beta parameter, and (2) the spectral slope of suprathermal electrons following a power-law distribution. Using a quasilinear model, we determine the critical values of
plasma beta and spectral slope that enable efficient electron acceleration via LHDI by comparing the rate of growth of instability and the damping rate of the resulting fluctuations. We further analyze the time
evolution of the electron distribution function to confirm these critical conditions. Our results indicate that electron acceleration is generally most efficient in low-beta
plasmas ($\beta < 1$). However, the presence of suprathermal electrons significantly enhances electron acceleration via LHDI, even in high-beta
plasmas ($\beta > 1$). Finally, we discuss the astrophysical implications of our findings, highlighting the role of LHDI in electron acceleration across diverse
plasma environments.
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