High Energy Astrophysical Phenomena · Cross-listed from hep-th
Exact black holes and black branes with bumpy horizons supported by superfluid pions
Fabrizio Canfora, Andrés Gomberoff, Carla Henríquez-Baez et al. (+1 more)
We present exact solutions of the Einstein $SU(2)$ non-linear sigma model in $3+1$ spacetime dimensions, describing bumpy black holes and black branes. Using an Ansatz for superfluid pion multi-
vortices, the matter sector reduces to a first-order BPS system, while the Einstein equations reduce to a Liouville equation with a smooth source governing the horizon deformation. These solutions describe horizons of different constant
curvatures, with nontrivial bumpy geometries protected by an integer topological invariant, namely the vorticity, which also controls the number of bumps and the black hole thermodynamics. Remarkably, such horizons arise in a minimal and physically motivated matter model, without invoking exotic fields or modified
gravity. The physical implications of these results in holography and astrophysics are briefly described.
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All authors Fabrizio Canfora, Andrés Gomberoff, Carla Henríquez-Baez, Aldo Vera
Cosmology and Nongalactic Astrophysics
The Bondi universe: Can negative mass drive the cosmological expansion?
Giovanni Manfredi, Jean-Louis Rouet and Bruce Miller
We identify a new cosmological coincidence that parallels the well-known matter/dark-energy coincidence: the present-epoch transition of the universe from a weakly coupled (collisionless) to a strongly coupled (collisional) gravitational regime. Within a cosmological model containing equal amounts of positive and negative Bondi masses – consistent with the weak equivalence principle and momentum conservation – we show that this coupling transition naturally coincides with the shift from a coasting to an accelerating expansion. A linear response analysis of the corresponding Vlasov-Poisson system reveals that mixed positive-negative mass configurations are always unstable, with growth rates that increase at shorter wavelengths, thereby driving the system toward strong coupling. Using long-time, exact one-dimensional N-body simulations, we demonstrate that the universe undergoes three successive expansion phases: an initial ballistic regime, an intermediate random-walk acceleration driven by sporadic Bondi encounters, and finally a uniformly accelerating phase triggered by the formation of stable positive/negative mass pairs. The onset of this last phase occurs precisely when the coupling parameter crosses unity, linking the two cosmological coincidences through a single dynamical mechanism. These results suggest that
cosmic acceleration may arise from the nonlinear dynamics of a gravitationally neutral mixed-mass universe, without invoking dark energy or a cosmological constant.
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Astrophysics of Galaxies
QSOFEED: Investigating warm molecular, low- and high-ionization atomic gas in six type-2 quasars with GTC/EMIR
P.H. Cezar, M. Coloma Puga, C. Ramos Almeida et al. (+6 more)
We present long-slit near-infrared spectroscopic observations of six nearby (z$\sim$0.1)
radio-quiet type-2
quasars (QSO2s) from the
Quasar Feedback (QSOFEED) sample. They have bolometric luminosities of $10^{45-46}~erg~s^{-1}$ and
stellar masses of $ 10^{10.6-11.3}~M_{\odot}$. The observations were obtained with the instrument Espectrógrafo Multiobjeto Infra-Rojo (EMIR) on the 10.4 m Gran Telescopio Canarias. The
nuclear K-band spectra (central $\sim$1-3 kpc of the QSO2s) reveal signatures of high-velocity
outflows in either the Pa$\alpha$ or Br$\gamma$ lines, depending on the
redshift, and in the [Si VI] lines. The broadest kinematic components have full width at half maximum (FWHM) of $\sim$1200-2500 km $s^{-1}$. From the near-infrared hydrogen recombination lines we derived ionized
outflow masses of $M_{Hion} \sim0.08-20\times 10^{6}~M_{\odot}$, mass
outflow rates of $\dot{M}_{Hion}\sim0.03-6~M_{\odot}~yr^{-1}$, and kinetic powers of $\dot{E}_{Hion}\sim 10^{37.8-40.8}~erg~s^{-1}$. These ionized gas
outflow masses and mass
outflow rates have median values that are 5.9 and 5.8 times larger, respectively, than those derived from the [Si VI] line. Our study provides evidence, at least for these six QSO2s, that the near-infrared recombination lines and [Si VI] are tracing the same
outflow (i.e., they have similar kinematics and radii), but they carry different amounts of mass. We detected warm molecular lines in the six QSO2s, from which we measured total (
nuclear) gas masses from 1.1 (0.7) to 32 (13) $\times~10^3~M_{\odot}$, similar to other QSO2s with warm $H_2$ measurements reported in the literature, but we did not find any molecular
outflow associated with them. Comparing with other five QSO2s with $H_2$ measurements reported in the literature, we find that the four QSO2s with detected $H_2$
outflows have total (
nuclear) $H_2$ masses 2.2 (2.7) times larger, on average.
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All authors P.H. Cezar, M. Coloma Puga, C. Ramos Almeida, J.A. Acosta-Pulido, G. Speranza, L.R. Holden, C.N. Tadhunter, M.V. Zanchettin, A. Audibert
High Energy Astrophysical Phenomena
Equatorially Asymmetric Magnetic Fields and Their Impact on Black Hole Accretion Dynamics
Ishika Palit, Indu Kalpa Dihingia, Yosuke Mizuno et al. (+1 more)
We investigate the impact of equatorial asymmetry in the
magnetic field geometry on
accretion dynamics around a spinning black hole using axisymmetric general relativistic magnetohydrodynamic simulations. We consider a Fishbone–Moncrief
torus orbiting a Kerr black hole with
spin parameter $a = 0.9375$, threaded by large-scale
magnetic fields that are asymmetric about the equatorial plane. The degree of equatorial asymmetry in the
magnetic field is parametrized by an angle, with values of $30^\circ$, $45^\circ$, and $60^\circ$. We examine how this equatorially asymmetric initial
magnetic field configuration influences the
magnetic field structure,
accretion flow morphology, and angular momentum transport across a range of initial
plasma beta values ($\beta = 0.007, 0.005, 0.001$). We find that such deformation in the
magnetic field leads to noticeable changes in the inner disk structure, asymmetric
outflow patterns in the poloidal plane, and time-dependent variations in
accretion rates. These effects are generally more pronounced at lower beta values, where
magnetic pressure dominates; in particular, the $30^\circ$ case at $\beta = 0.001$ exhibits strong and persistent asymmetric inflows and
outflows. Our results demonstrate that equatorially asymmetric
magnetic field configurations can significantly influence the structure and variability of relativistic
accretion flows. These findings motivate future extensions to full three-dimensional studies, where black hole magnetosphere can be explored in a more general setting.
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All authors Ishika Palit, Indu Kalpa Dihingia, Yosuke Mizuno, Hsiang-Yi Karen Yang
Astrophysics of Galaxies
Millimeter and submillimeter spectroscopy of methylallene, CH$_3$CHCCH$_2$
Holger S. P. Müller, Frank Lewen, Jean-Claude Guillemin et al. (+1 more)
Small polycyclic aromatic hydrocarbons and somewhat larger cyano derivatives were detected in the cold dark cloud TMC-1 recently. Their formation from smaller hydrocarbons is not well understood, in part because abundances of many species are not known. Methylallene, CH$_3$CHCCH$_2$, may be one of the building blocks, but its rotational spectrum was characterized only to a very limited extent. We recorded rotational transitions in the 36$-$501 GHz region to extend the existing line list of methylallene and thus enable searches for the molecule in space.
Quantum-chemical calculations were carried out to evaluate initial spectroscopic parameters. We obtained transition frequencies with $J \le 61$ and $K_a \le 21$ and resolved the internal rotation splitting of the CH$_3$ group at least partially. As a result, a full set of distortion parameters up to sixth order along with two octic ones were determined, as well as parameters describing the internal rotation of the methyl group. The spectroscopic parameters are accurate enough to identify methylallene up to 720 GHz, sufficient for searches even in the warm interstellar medium.
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All authors Holger S. P. Müller, Frank Lewen, Jean-Claude Guillemin, Stephan Schlemmer
Astrophysics of Galaxies
MAGAZ3NE: Dust Deficiency in Ultramassive Quiescent Galaxies at $3<z<4$ with ALMA Observations
Wenjun Chang, Gillian Wilson, Ben Forrest et al. (+14 more)
A major challenge in identifying massive quiescent
galaxies at $z>3$ is distinguishing truly passive systems from
dust-obscured
star-forming
galaxies, as both populations exhibit similar red ultraviolet (UV)-to-near-infrared (NIR) colors. In this work, we present ALMA Band 7
dust-continuum observations of five ultramassive
galaxies (UMGs; $\log (M_\star / M_\odot) > 11$) spectroscopically confirmed at $z_{\rm spec} > 3$ from the MAGAZ3NE survey. Our results reveal that only one
galaxy shows a faint 870 \um\
dust continuum detection, while the remaining four UMGs are undetected down to the $3\sigma$ depth . By incorporating ALMA constraints into the spectral energy distribution analysis, we confirm that these UV-NIR-selected systems are truly quiescent UMGs, lying more than one dex below the
star-forming main sequence with $\mathrm{\log (sSFR/Gyr^{-1}) < -1}$, thereby ruling out the possibility of obscured
star formation. We then estimate
dust masses using both spectral energy distribution modeling and modified blackbody fitting, with consistent results between the two methods. We find that three UMGs have evolved into extremely
dust-poor quiescent
galaxies, with $M_{\mathrm{dust}}/M_\star \lesssim 10^{-4}$, while the ALMA-detected
galaxy has a comparatively higher
dust reservoir with $M_{\mathrm{dust}}/M_\star \sim 10^{-3}$. Our results present the most massive and extremely
dust-poor spectroscopically confirmed quiescent
galaxies known at $3 < z < 4$, providing valuable observational constraints on rapid
dust removal and quenching processes in the early universe. Future molecular line observations will be essential to directly measure the gas content and verify the efficiency of the depletion process.
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All authors Wenjun Chang, Gillian Wilson, Ben Forrest, Ian McConachie, Allison Noble, Adam Muzzin, Danilo Marchesini, Michael C. Cooper, Tracy Webb, Gabriela Canalizo, Percy L. Gomez, Yongda Zhu, Adit Edward, Han Lei, Aurélien Henry, Stephanie M. Urbano Stawinski, Marie E. Wisz
High Energy Astrophysical Phenomena
X-ray Spectroscopy of Disk Winds in Black Hole X-ray Binaries
Megumi Shidatsu and Maxime Parra
Powerful
outflows along the
accretion disk, known as disk winds, are sometimes launched in black hole X-ray binaries. These winds often manifest themselves in X-ray spectra as blueshifted, highly ionized absorption lines. Previous observations suggest that the mass loss rate from the disk due to disk winds can be comparable to or even more than the mass
accretion rate onto the black hole, indicating that disk winds likely play crucial roles in shaping the
accretion disk structure and affecting the surrounding environment. However, the mechanisms driving these winds, as well as how their structure changes in response to variations in the mass
accretion rate, remain poorly understood. The X-ray Imaging and Spectroscopy Mission (XRISM), launched in September 2023, is equipped with Resolve, a cutting-edge X-ray micro-calorimeter that delivers unprecedented spectral resolution. Resolve is expected to significantly advance our understanding of wind launching mechanisms and their impact on
accretion processes and environments. In this article, we review the progress made in the pre-XRISM era, highlight key results obtained from XRISM observations to date, and outline future prospects.
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Astrophysics of Galaxies
Rotational Spectroscopy as a Tool to Study Vibration-Rotation Interaction: Investigations of $^{13}$CH$_3$CN and CH$_3$$^{13}$CN up to $v_8 = 2$ and a Search for $v_8 = 2$ Transitions toward Sagittarius B2(N)
Holger S. P. Müller, Arnaud Belloche, Frank Lewen et al. (+1 more)
Methyl cyanide, CH$_3$CN, is present in diverse regions in space, in particular in the warm parts of
star-forming regions where it is a common molecule. Rotational transitions of $^{13}$CH$_3$CN and CH$_3$$^{13}$CN in their $v_8 = 1$ lowest excited vibrational states ($E_{\rm vib} \approx 520$ K) are quite prominent in Sagittarius B2(N). In order to be able to search for transitions of the next higher vibrational state $v_8 = 2$, we recorded spectra of samples enriched in $^{13}$CH$_3$CN and CH$_3$$^{13}$CN up to $v_8 = 2$ in the 35 to 1091~GHz region and reinvestigated existing spectra of CH$_3$CN in its natural isotopic composition between 1085 and 1200 GHz. Perturbations caused by near-degeneracies in $K = 4$ of $v_8 = 2^0$ and $K = 2$ of $v_8 = 2^{-2}$ yielded accurate information on the energy spacing of 22.93 and 21.79 cm$^{-1}$ between the $l$-components of $^{13}$CH$_3$CN and CH$_3$$^{13}$CN, respectively.
Fermi-type interaction between $K = 13$ and 14 of $v_8 = 1^{-1}$ and $v_8 = 2^{+2}$ probe the energy differences between the two states of both isotopomers. In addition, a $\Delta K \pm2$, $\Delta l \mp1$ interaction between the ground vibrational state of $^{13}$CH$_3$CN and $v_8 = 1^{+1}$ provides information on their energy spacing. Furthermore, we obtained improved or extended ground state rotational transition frequencies of $^{13}$CH$_3$$^{13}$CN and extensive data for $^{13}$CH$_3$C$^{15}$N and CH$_3$$^{13}$C$^{15}$N. Finally, we report the results of our search for transitions of $^{13}$CH$_3$CN and CH$_3$$^{13}$CN in their $v_8 = 2$ states toward Sagittarius B2(N).
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All authors Holger S. P. Müller, Arnaud Belloche, Frank Lewen, Stephan Schlemmer
Earth and Planetary Astrophysics
The SPIRou Legacy Survey: Detection of a nearby world orbiting in the habitable zone of Gl725B achieved by correcting strong telluric contamination in near-infrared radial velocities with WAPITI
M. Ould-Elhkim, C. Moutou, J.-F. Donati et al. (+15 more)
M
dwarfs are
prime targets in the search for
exoplanets because of their prevalence and because low-mass
planets can be better detected with radial velocity (RV) methods. In particular, the near-infrared (NIR) spectral domain offers an increased RV sensitivity and potentially reduced
stellar activity signals. Howevern precise NIR RV measurements can be strongly affected by telluric absorption lines from the Earth's atmosphere. We searched for
planets orbiting Gl 725 B, a nearby late-M
dwarf at $3.5$ pc, using high-precision SPIRou RV observations. We assessed the impact of telluric contamination and evaluated the performance of the weighted principal component analysis reconstruction method (WAPITI), designed to mitigate these systematics and improve
planet detectability. Using synthetic and observational SPIRou data, we simulated telluric effects on RVs under varying barycentric Earth radial velocity (BERV) conditions and applied WAPITI to correct line-by-line RVs. The method was tested through injection-recovery experiments and applied to real SPIRou observations of Gl 725 B. WAPITI efficiently corrects telluric contamination in simulated and real
datasets, enhancing the detectability and accuracy of planetary signals. We identify a two-
planet system around Gl 725 B composed of a candidate inner
planet (Gl 725 Bb) with a period of $4.765 \pm 0.004$ days and semi-amplitude $1.4 \pm 0.3$ m.s$^{-1}$, and a confirmed outer
planet (Gl 725 Bc) with a period of $37.90 \pm 0.17$ days and semi-amplitude $1.7 \pm 0.3$ m.s$^{-1}$. Their minimum masses are $1.5 \pm 0.4$ and $3.5 \pm 0.7$ M$_\oplus$, respectively, and the outer
planet lies in the habitable zone. Using a multi-dimensional Gaussian process framework to model
stellar activity, we also recover a
stellar rotation period of $105.1 \pm 3.3$ days.
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All authors M. Ould-Elhkim, C. Moutou, J.-F. Donati, P. Cortés-Zuleta, X. Delfosse, É. Artigau, C. Cadieux, P. Charpentier, A. Carmona, I. Boisse, C. Reylé, E. Gaidos, R. Cloutier, G. Hébrard, L. Arnold, J.-D. do Nascimento Jr., N. J. Cook, R. Doyon
Solar and Stellar Astrophysics
Xuebao Li, Yongshang Lv, Jinfang Wei et al. (+14 more)
This study focuses on
forecasting major (>=M-class)
solar flares that can severely impact the near-Earth environment. We construct two types of
datasets using the Space Weather HMI Active Region Patches (SHARP), and develop a
flare prediction network based on large
language model (LLMFlareNet). We apply SHapley Additive exPlanations (SHAP) to explain the model predictions. We develop an operational
forecasting system based on the LLMFlareNet model. We adopt a daily mode for performance comparison across various operational
forecasting systems under identical active region (AR) number and prediction date, using daily operational observational data. The main results are as follows. (1) Through ablation experiments and comparison with baseline models, LLMFlareNet achieves the best TSS scores of 0.720 +/- 0.040 on the ten cross-validation (CV)
dataset with mixed ARs. (2) By both global and local SHAP analyses, we identify that R_VALUE is the most influential physical feature for the prediction of LLMFlareNet, aligning with
flare magnetic reconnection theory. (3) In daily mode, LLMFlareNet achieves TSS scores of 0.680/0.571 (0.689/0.661, respectively) on the
dataset with single/mixed ARs, markedly outperforming NASA/CCMC (SolarFlareNet, respectively). This work introduces the first application of a large
language model as a universal computation engine with explainability method in this domain, and presents the first comparison between operational
flare forecasting systems in daily mode. The proposed LLMFlareNet-based system demonstrates substantial improvements over existing systems.
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All authors Xuebao Li, Yongshang Lv, Jinfang Wei, Yanfang Zheng, Ting Li, Rui Wang, Zixian Wu, Hongwei Ye, Pengchao Yan, Zamri Zainal Abidin, Noraisyah Mohamed Shah, Changtian Xiang, Shunhuang Zhang, Xiaojia Ji, Xusheng Huang, Xiaotian Wang, Honglei Jin
High Energy Astrophysical Phenomena
Approximation of the reception coefficients of cosmic rays neutron component for latitude measurement
Kobelev P.G. and Yanke V.G
When solving scientific and applied problems, such as latitude monitoring, it is important to correctly exclude primary
cosmic ray variations from observation data. Therefore, the purpose of this study was to develop and implement a method for correcting monitoring data, the key point of which was to obtain reception coefficients as a function of latitude. This resulted in an approximation of the
rigidity dependence of the zeroth and first harmonic
cosmic rays anisotropy coefficients, calculated for a ground-based
cosmic ray detectors network. Analysis of the obtained results showed that the approximation was performed with high accuracy, and the results are suitable for use in latitude measurements during marine expeditions.
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Solar and Stellar Astrophysics
Ground Level Enhancement (GLE#77) in the gamma-ray component: First observation from Arctic and Antarctic stations
Pranali Thakur, Geeta Vichare and Selvaraj Chelliah
This article presents the observations of the extreme ground-level enhancement (GLE #77) of
Solar Cycle 25 that occurred on 11 November 2025, using ground-based NaI(Tl) gamma-ray detectors deployed at Arctic and Antarctic stations, together with
neutron monitor data and particle measurements from the GOES-18 satellite. The event was associated with an intense X-class
solar flare and a strong
solar energetic
proton event. This paper reports the first ground-based detection of a GLE using gamma-ray detectors operating simultaneously in both polar regions, which are concurrent with increases in
neutron monitor counts. Thus highlights the capability of polar gamma-ray detectors to complement traditional
neutron monitor observations during extreme
solar proton events. A detailed analysis revealed distinct
prompt and delayed responses during the event
evolution. Interestingly, the signature of the
prompt peak of GLE#77 (at 10:38 UT) was observed up to high-
rigidity neutron monitors (low latitudes). However, the delayed peak (at 13:08 UT) was not seen at the stations with
rigidity > 6 GV. The timing of the
prompt and delayed peaks coincided with the
proton flux peaks observed by the GOES-18 satellite at energies > 150 MeV and 12-99 MeV, respectively. It is observed that the GLE amplitude has a strong dependence on geomagnetic cutoff
rigidity and has a weak
solar zenith angle dependence.
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Astrophysics of Galaxies
Statistical study for binary star evolution in dense embedded clusters
Wenjie Wu, Pavel Kroupa and Vikrant V. Jadhav
Context: The dynamical
evolution of binary populations in embedded
star clusters shapes the statistical properties of binaries observed in the
Galactic field. Accurately modelling this process requires resolving both early cluster dynamics and binary interactions. Aims: We aim to characterize the early dynamical
evolution of
primordial binaries in embedded clusters and identify the key parameters that govern binary survival and disruption. Methods: We perform a set of direct $N$-body simulations starting from 100%
primordial binaries in a time-varying gas potential of a gas-embedded cluster. To describe the
evolution of binary orbital properties, we define empirical dynamical operators for period, binding energy, and mass ratio, and calibrate them across the simulated ensemble. Results:The binding energy and orbital period evolve in a consistent, sigmoidal fashion. Their dynamical operators reveal that hard binaries heat the cluster and suppress wide binary formation, while a small residual population of soft binaries survives. The
evolution of the mass-ratio distribution is less directly linked to dynamical processing and more shaped by internal processes such as
stellar physics process in the pre-main-sequence phase. High-$q$ systems tend to be enhanced, while low-$q$ systems are prone to disruption. Conclusions: The binary
evolution in clusters is primarily governed by binding energy and orbital period. Our model improves over previous parameterizations of the dynamical operator by allowing for the existence of wide binaries and incorporating the embedded cluster phase. For individual clusters, direct $N$-body modelling remains the only reliable approach. On
Galactic scales, population synthesis methods based on the
stellar dynamical operator approach developed here remain essential.
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High Energy Astrophysical Phenomena
Predicting Multiwavelength Emission Associated with X-Ray Flares and Extended Emission of Gamma-Ray Bursts
Riki Matsui, Shigeo S. Kimura, Kohta Murase et al. (+1 more)
Gamma-ray bursts (GRBs) are one of the most extreme transients in the universe, but their explosion and emission mechanism remains unclear. To investigate the nature of GRB jets, here we focus on X-ray
flares (XFs) and extended emissions (EEs), which are X-ray emissions that occur 100 to 1000 seconds after the main burst. They can be observed by recently developed multi-wavelength facilities. In this paper, we calculate emissions across multi-wavelengths associated with XFs and EEs under the hypothesis that XFs and EEs are optically-thin synchrotron emissions from nonthermal electrons in relativistic jets. Considering ranges of the dissipation radius $r_{\rm diss}$ and the Lorentz factor $\Gamma$ of the jet, we determine the parameter space in which a detectable emission can be produced at each wavelength. We found that simultaneous ultraviolet and very-high-energy gamma-ray emission associated with XFs or EEs can be detected by Swift/UVOT, SVOM/VT, and CTAO approximately every three years. The detection and non-detection rates for each detector are key to determining the uncertain yet essential values necessary for understanding the physics of GRB jets.
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All authors Riki Matsui, Shigeo S. Kimura, Kohta Murase, Bing Theodore Zhang
High Energy Astrophysical Phenomena
Ultra-High Energy Cosmic Rays from the Galactic Center
V.N.Zirakashvili and S.I.Rogovaya
It is shown that Eddington-like
accretion event in the
Galactic center several million years ago and particle acceleration at accompanying shocks and jets could explain the observed
cosmic ray spectrum at energies above 1 PeV.
Cosmic ray particles are confined in extended (several hundred kiloparsec in size)
Galactic halo. It is shown that the
halo magnetic field could be as small as $2\times 10^{-7}$ G for the effective confinement.
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High Energy Astrophysical Phenomena
Detection of an Extremely Luminous Radio Counterpart to the Be/X-ray Binary A0538-66
Justine Crook-Mansour, Rob Fender, Alex Andersson et al. (+14 more)
We present the discovery of
radio emission from the Be/X-ray binary A0538-66 with the Australian Square Kilometre Array Pathfinder (ASKAP), and results from a subsequent weekly monitoring campaign with the MeerKAT
radio telescope. A0538-66, located in the Large Magellanic Cloud, hosts a
neutron star with a short
spin period ($P \approx 69$ ms) in a highly eccentric $\approx16.6$-day orbit. Its rare episodes of super-Eddington
accretion, rapid optical and X-ray
flares, and other peculiar properties make it an interesting system among high-mass X-ray binaries. Our MeerKAT data reveal that it is also one of the most
radio-luminous
neutron star X-ray binaries observed to date, reaching $\approx 3 \times 10^{22}~\text{erg}~\text{s}^{-1} \text{Hz}^{-1}$, with
radio emission that appears to be orbitally modulated. We consider several possible mechanisms for the
radio emission, and place A0538-66 in context by comparing it to similar systems.
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All authors Justine Crook-Mansour, Rob Fender, Alex Andersson, Hao Qiu, Andrew K. Hughes, Jakob van den Eijnden, Fraser J. Cowie, Sara Motta, Itumeleng Monageng, Lorenzo Ducci, Sandro Mereghetti, Andries Mathiba, Dougal Dobie, Tara Murphy, David L. Kaplan, Francesco Carotenuto, Phil Charles
High Energy Astrophysical Phenomena
A unified framework for hot accretion flows with finite angular momentum: from Bondi-like to disc-like regimes
Cheng-Liang Jiao, Liying Zhu, Er-gang Zhao et al. (+1 more)
Observations of X-ray luminous elliptical
galaxies suggest that the
accretion rate onto the central supermassive black hole can reach a substantial fraction of the Bondi rate. However, classical
accretion theory applicable to such hot
accretion flows treats spherically symmetric Bondi
accretion and disc-like advection-dominated
accretion flows (ADAFs) as two distinct limiting cases, lacking a unified framework for flows with finite angular momentum. In this work, we develop such a framework that continuously connects these two regimes. Our model naturally recovers the Bondi solution in the limit of vanishing angular momentum and approaches the properties of classical ADAFs at high angular momentum, while providing a physically well-defined description of the intermediate regime where neither limiting case is strictly applicable. We further demonstrate that the
accretion rate is jointly regulated by the angular momentum of the ambient gas and the gas viscosity. For sufficiently large but physically reasonable viscosity, the
accretion rate can remain at a significant fraction of the Bondi rate even in the presence of substantial gas rotation. These results offer a natural explanation for how such
accretion rates can be sustained despite finite angular momentum in realistic
galactic environments.
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All authors Cheng-Liang Jiao, Liying Zhu, Er-gang Zhao, Xiang-dong Shi
Solar and Stellar Astrophysics
Apsidal motion and TESS light curves of two southern eclipsing binaries with high eccentricity: V1647 Sgr and V2283 Sgr
Marek Wolf, Petr Zasche, Miloslav Zejda et al. (+1 more)
The study of apsidal motion rates in eccentric eclipsing binaries provides an important observational test of theoretical models of
stellar structure and
evolution. Precise physical parameters of the
stellar components together with systematic measurements of the periastron advance are needed. We present new results of our long-term observational project to analyze the apsidal motion in early-type eccentric eclipsing binaries. New ground and space-based photometric data were obtained, and archival spectroscopic measurements were used in this study of two detached southern-hemisphere eclipsing binaries: V1647 Sgr (P=3.28 d, e=0.41), and V2283 Sgr (3.47, 0.49). Their TESS observations in four sectors have also been included and the corresponding light curves were solved using the Phoebe code. The newly completed O-C diagrams were analyzed using all reliable timings found in the literature and calculated using the TESS light curves. New or improved values were obtained for the elements of apsidal motion. Using archival spectroscopy for V1647 Sgr, the precise absolute parameters were improved: M1 = 2.184(0.035) M$_\odot$, M2 = 1.957(0.035) M$_\odot$, and R1 = 1.839(0.015) R$_\odot$, R2 = 1.716(0.015) R$_\odot$. For V2283 Sgr the absolute dimensions were newly estimated: M1 = 2.178(0.10) M$_\odot$, M2 = 1.547(0.10) M$_\odot$, and R1 = 1.796(0.01) R$_\odot$, R2 = 1.544(0.01) R$_\odot$. We improved relatively long periods of apsidal motion of about 580 and 530 years, together with the corresponding internal structure constants, log k2, -2.394, and -2.418, for V1647 Sgr and V2283 Sgr, respectively. The relativistic contribution to apsidal motion is not negligible, making about 12 resp. 14% of the total rate of apsidal motion. No signs of the presence of an additional body were revealed in the light curves or in the O-C diagrams of both eccentric systems.
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All authors Marek Wolf, Petr Zasche, Miloslav Zejda, Martin Mašek
High Energy Astrophysical Phenomena
Dynamics of magnetoviscous warped discs around compact objects
Arthur G. Suvorov and Kostas Glampedakis
Accretion discs that are tilted with respect to their compact hosts can warp out-of-plane through general relativistic frame-dragging. Warp influences disc dynamics in ways that have been studied extensively, especially as regards instabilities that might lead to rapid angular-momentum cancellation between neighboring rings of fluid and mass infall. We provide a review of warped-disc phenomena here, revisiting key hydrodynamical assumptions that impact calculations of the shear viscosity controlling instability thresholds. Relativistic effects at the level of gas-parcel orbits are included, as are external Lorentz forces applied by the compact primary's
magnetic field. Semianalytic analysis reveals that intense
magnetic fields can bring about new branches of warp modes and avoided crossings that significantly reduce the perpendicular viscosity at sub-Eddington
accretion rates. Critical strengths required for misaligned torques to tear a thin disc may thus relax for systems like
neutron star X-ray binaries or
radio-loud active
galactic nuclei.
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Cosmology and Nongalactic Astrophysics
Distinguishing the nature of dark matter by mapping cosmic filaments from Lyman-alpha emission
Yizhou Liu, Liang Gao, Shihong Liao et al. (+3 more)
The standard $\Lambda$CDM cosmological model predicts that
cosmic filaments are highly clumpy, whereas warm dark matter – invoked to address small-scale challenges in $\Lambda$CDM – produces filaments that are noticeably smoother and less structured. In this work, we investigate the potential of Lyman $\alpha$ (Ly$\alpha$) emission to trace
cosmic filaments at
redshifts $z=2.5$ and $z=4$, and assess their potential for constraining the nature of dark matter. Our analysis shows that Ly$\alpha$ filaments provide a promising observational probe of dark matter: at $z=4$, differences in filament smoothness and surface brightness serve as distinctive signatures between models. Looking ahead, the upcoming generation of 30-meter class
telescopes will be critical for enabling these measurements, offering a compelling opportunity to distinguish the nature of dark matter by mapping the structure of
cosmic filaments.
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All authors Yizhou Liu, Liang Gao, Shihong Liao, Kai Zhu, Yingjie Jing, Huijie Hu
Solar and Stellar Astrophysics
The accretion-ejection connection in the asymmetric Th 28 jet revealed by MUSE-NFM
A. Murphy, E. T. Whelan, F. Bacciotti et al. (+5 more)
Mass loss through
stellar jets is closely tied to the process of
accretion through the disk. Understanding phenomena such as episodic ejections and
outflow asymmetries can thus shed light on the mechanism of jet launching and its connection to both mass
accretion and the
evolution of the protoplanetary disk. We use new VLT/MUSE Narrow Field Mode observations of the Classical T Tauri
Star Th 28 to map the jet structures within 6” of the source at an effective angular resolution of 0.”12, provided by the combination of the AO correction and image deconvolution. The emission line profiles and flux ratios are investigated and diagnostic analysis of the optical forbidden emission lines (FELs) is used to estimate the electron density, ionisation fraction, electron temperature and shock velocities in both jet lobes within 200 au of the
star. The mass
outflow rates in each lobe are obtained using the derived total densities and FEL luminosities and compared with the mass
accretion rate. We identify several new
knots in both jet lobes which have been ejected in the previous 10 years on a timescale of 3-6 years, which is significantly more frequent than previously estimated. In both lobes we find comparable mass
outflow rates close to the jet base. Th 28 has undergone a significant rise in mass
accretion rate between 2014 and 2023, which may be linked to the most recently ejected
knot pair detected in each side of the jet. The red-shifted jet mass
outflow rate shows a similar increase of a factor 2, indicating that the ratio of mass
outflow to
accretion remains constant. A moderately lower mass
outflow rate is found in the faster blue-shifted lobe, supporting the possibility that momentum ejection is conserved on each side of the jet. The frequent
knot ejections indicate that this source is a good target for further monitoring to study the
accretion-ejection connection.
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All authors A. Murphy, E. T. Whelan, F. Bacciotti, A. Kirwan, D. Coffey, M. Birney, J. Eislöffel, H. Takami
Astrophysics of Galaxies
The size-velocity dispersion relationship of Galactic HII regions
Lin Ma, Yunning Zhao, Wei Zhang et al. (+11 more)
The size-velocity dispersion ($\sigma$) relation, while well established for
giant HII regions, remains uncertain for their smaller counterparts (physical radii R < 20 pc). Thanks to the LAMOST MRS-N
dataset's large sky coverage and high spatial/spectral resolution, we examined this relationship using 10 isolated
Galactic HII regions with R < 20 pc. Our results reveal two key findings: (1) these small-size HII regions remarkably follow the same size-$\sigma$ relation as
giant HII regions, suggesting this correlation could serve as a novel distance indicator for
Galactic HII regions; and (2) we find distinct dynamical behaviors between younger and older HII regions. Specifically, in younger (< 0.5 Myr), ionization-bounded HII regions, the velocity dispersion shows no correlation with expansion velocity, indicating that
turbulence is driven primarily by
stellar winds and ionization processes. In contrast, in older (> 0.5 Myr), matter-bounded HII regions, a clear correlation emerges, implying that expansion-driven processes begin to play a significant role in generating
turbulence. We therefore propose an evolutionary transition in the primary
turbulence mechanisms, from being dominated by
stellar winds and radiation to being increasingly influenced by expansion-driven dynamics, during the
evolution of HII regions. Considering the small sample size used in this work, particularly the inclusion of only two young HII regions, which also have large uncertainties in their expansion velocities, further confirmation of this interpretation will require higher-resolution 2D spectroscopy to resolve blended kinematic components along the line of sight for more accurate estimation of expansion velocities, along with an expanded sample that specifically includes more young HII regions.
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All authors Lin Ma, Yunning Zhao, Wei Zhang, Youliang Feng, Shiming Wen, Shichao Han, Chaojian Wu, Juanjuan Ren, Jianjun Chen, Yuzhong Wu, Zhongrui Bai, Yonghui Hou, Yongheng Zhao, Hong Wu
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Nonlocal Corrections to Scalar Field Effective Action in de Sitter spacetime
Will Cerne and Teruaki Suyama
We investigate the one-loop effective action for a test scalar field in a general Friedmann-Lemaître-Robertson-Walker (FLRW) background, specifically focusing on
quantum corrections up to the second order in the interaction strength. By employing the Schwinger-Keldysh formalism, we derive the equation of motion for the field expectation value, which incorporates not only the standard local radiative corrections but also novel nonlocal features: a
memory term and a
stochastic noise term. We identify all ultraviolet divergent structures within these nonlocal terms and provide a consistent renormalization procedure. To analyze the physical impact of these terms, we apply a local approximation under the assumption of slowly-varying fields, by which the
memory term acts as a negative contribution to the drift coefficient. As a concrete application, we consider a massive $\phi^4$ theory and show that these one-loop corrections lead to a suppression of the field variance in the infrared regime compared to the tree-level results.
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Astrophysics of Galaxies
Probing Star-Forming Properties via ALMA Observations of Massive Protocluster IRAS 15596-5301
Faxian Chang, Mengyao Tang, Tie Liu et al. (+8 more)
To deepen our understanding of
star-forming properties, we studied a massive protocluster IRAS 15596-5301 using ALMA 870 um and 3 mm data. High-resolution 870 um data reveal 34 dense cores, including 3 hot molecular cores, with subsequent line surveys detecting 22 molecular species toward them. Two velocity components (I15596-red/I15596-blue) were found in the averaged H13CO+(1-0) spectrum, and two filaments were identified from velocity-resolved integrated intensity maps. A spatial overlap between the two filaments was observed, and this overlapping region exhibits a distinct bridge-shaped feature in the position-velocity diagram constructed along the entire filamentary structures. Combined with the reduced H13CO+/HCO+ ratio in the overlapping region and the three-dimensional position-position-velocity cube data, we conclude that a non-head-on collision occurs between the edges of the two filamentary structures in IRAS 15596-5301. Cluster analysis demonstrates that clusters located in the collision region host more evolved chemical rich dense cores than their counterparts in other regions. Our results thus indicate that
star formation in I15596 is triggered or accelerated by a mild non-head-on collision between two filaments.
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All authors Faxian Chang, Mengyao Tang, Tie Liu, Luis A. Zapata, Dongting Yang, Yaping Peng, Chao Zhang, Fengwei Xu, Y. H. Chen, Shujie Li, Meng Ruan
Earth and Planetary Astrophysics · Cross-listed from physics.geo-ph
Sculpting of Martian brain terrain reveals the drying of ancient Mars
Shenyi Zhang, Lei Zhang, Yutian Ke et al. (+1 more)
The Martian
brain terrain (MBT), characterized by its unique
brain-like morphology, is a potential geological archive for finding hints of paleoclimatic conditions during its formation period. The morphological similarity of MBT to self-organized patterned ground on Earth suggests a shared formation mechanism. However, the lack of quantitative descriptions and robust physical modeling of self-organized stone transport jointly limits the study of the thermal and aqueous conditions governing MBT's formation. Here we established a specialized quantitative system for extracting the morphological features of MBT, taking a typical region located in the northern Arabia Terra as an example, and then employed a numerical model to investigate its formation mechanisms. Our simulation results accurately replicate the observed morphology of MBT, matching its key
geometric metrics with deviations <15%. Crucially, however, we find that the self-organized transport can solely produce relief <0.5 m, insufficient to explain the formation of MBT with average relief of 3.29 \pm 0.65 m. We attribute this discrepancy to sculpting driven by late-stage sublimation, constraining cumulative subsurface ice loss in this region to ~3 meters over the past ~3 Ma. These findings demonstrate that MBT's formation is a multi-stage process: initial patterning driven by freeze-thaw cycles implying
liquid water followed by vertical sculpting via sublimation requiring a dry environment. This
evolution provides physical evidence for the transition of the ancient Martian
climate from a wetter period to a colder hyper-arid state.
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All authors Shenyi Zhang, Lei Zhang, Yutian Ke, Jinhai Zhang
Astrophysics of Galaxies
The GECKOS Survey: Extraplanar ionised gas in star-forming galaxies from eDIG to galaxy-scale winds
R. Elliott, D. B. Fisher, B. Mazzilli Ciraulo et al. (+19 more)
We map the extraplanar gas, with $\sim$50-200 pc resolution, in nine
star-forming
galaxies using Multi-Unit Spectroscopic Explorer (MUSE) observations from the GECKOS VLT Large Program targeting edge-on
galaxies with similar
stellar mass as the Milky Way. The narrow range in
stellar mass ($\pm0.35$ dex) of the GECKOS sample makes it ideal for studying trends with
star formation rate (SFR). We find strong extraplanar emission reaching $\sim$2-8 kpc from the disk midplane in all targets with $\rm{SFR}\geq$1 M$_{\odot}$ yr$^{-1}$. Targets with SFR$\,\geq\,$5 M$_{\odot}$ yr$^{-1}$ have brighter, more extended H$\alpha$ emission compared to lower SFR targets. In high-SFR systems, the gas velocity dispersion ($\sigma_{\rm H\alpha}$) shows a biconical morphology, consistent with the expectation of
outflows. This agrees with previous works suggesting high velocity dispersion in a biconical shape is a good means to identify
outflows. We find mixed results using line diagnostics ([OIII]$_{5007}$/H$\beta$ - [NII]/H$\alpha$ and $\sigma_{\rm H\alpha}$ - [SII]/H$\alpha$) to spatially resolve ionisation mechanisms across the extraplanar gas. The highest [NII]/H$\alpha$ are the extraplanar gas of the highest SFR systems, yet main-sequence
galaxies have the highest [OIII]/H$\beta$. While the morphology of [NII]/H$\alpha$ may be useful to identify
outflows, the absolute value of the line ratio alone may not distinguish strong
outflows from extraplanar gas of main-sequence
galaxies. The ubiquitous extraplanar emission can be interpreted as the result of feedback, in the form of large-scale winds for starbursts or smaller-scale
galactic fountains for main-sequence
galaxies. Moreover, shock-heating may ionise gas at the interface of the disk and the circumgalactic medium, independent of the source of the gas.
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All authors R. Elliott, D. B. Fisher, B. Mazzilli Ciraulo, A. Fraser-McKelvie, M. R. Hayden, M. Martig, J. van de Sande, A. J. Battisti, J. Bland-Hawthorn, A. D. Bolatto, T. H. Brown, B. Catinella, F. Combes, L. Cortese, T. A. Davis, E. Emsellem, D. A. Gadotti, F. Pinna, T. H. Puzia, L. A. Silva-Lima, L. M. Valenzuela, G. van de Ven
Solar and Stellar Astrophysics
SED and Galactic kinematic diagnostics for dormant BH/NS binary candidates
Qian-Yu An and Wei-Min Gu
The third data release of the
Gaia mission (
Gaia DR3) has enabled large-scale searches for dormant black hole and
neutron star binaries with
stellar companions at AU-scale separations. A recent study has proposed thousands of dormant black hole and
neutron star binary candidates using summary statistics from
Gaia DR3 by simulating and fitting
Gaia observables. In this work, we perform broadband spectral energy distribution (SED) fitting from the optical to the infrared for 1,328 candidates, incorporating GALEX ultraviolet photometry to assess the presence of hidden hot companions. We quantify ultraviolet excess by comparing observed near-ultraviolet fluxes with single-
star SED predictions and further test whether excesses can be explained by non-degenerate
stellar companions for sources exhibiting moderate excess. We additionally examine the
Galactic kinematics of the sample to identify systems potentially affected by natal kicks during compact-object formation. By combining the ultraviolet and kinematic diagnostics, we identify 182 sources as the highest-priority candidates for follow-up observations, in which 19 are black hole candidates with fit_companion_mass $\geq$ 3 $M_\odot$.
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High Energy Astrophysical Phenomena
A Formation Crisis of Repeating Partial Tidal Disruption Events
Zhen Pan and Dong Lai
A number of candidate repeating partial
tidal disruption events (rpTDEs) have been reported in recent years. If these events are confirmed, the high fraction of observed rpTDEs among all
tidal disruption events (TDEs) is in tension with prediction of the loss cone channel. We further point out an inequality $M_\bullet \lesssim 4\times 10^6 M_\odot (T_{\rm obt}/10\ {\rm yr})^{4/9}$ that must be satisfied for rpTDEs of
solar type
stars in the loss cone channel, where $M_\bullet$ is the central supermassive black hole (SMBH) mass and $T_{\rm obt}$ is the orbital period of the
star. However the majority of reported rpTDE candidates potentially violate this inequality, indicating an alternative formation channel. In the commonly invoked Hills mechanism, the captured
stars produced by
tidal disruption of near-contact binaries can evade this inequality and may be the dominant source of rpTDEs. If the same process operates in the
Galactic Center, there should exist a population of hypervelocity
stars (HVSs) ejected with velocities as high as $3.6\times 10^3 (M_\bullet/10^6 M_\odot)^{1/6}\ {\rm km\ s}^{-1}$, which however have not been detected. A complete search for HVSs in the Milky Way will be critical for testing this prediction.
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High Energy Astrophysical Phenomena
Constructing a gravitational wave analysis pipeline for extremely large mass ratio inspirals
Tian-Xiao Wang, Yan Wang, Alejandro Torres-Orjuela et al. (+4 more)
Extremely large mass-ratio inspirals (XMRIs), consisting of a brown
dwarf orbiting a supermassive black hole, emit long-lived and nearly monochromatic gravitational waves in the millihertz band and constitute a promising probe of strong-field
gravity and black-hole properties. However, dedicated data-analysis pipelines for XMRI signals have not yet been established. In this work, we develop, for the first time, a hierarchical semi-coherent search pipeline for XMRIs tailored to space-based gravitational-wave detectors, with a particular focus on the TianQin mission. The pipeline combines a semi-coherent multi-harmonic $\mathcal{F}$-statistic with particle swarm optimization, and incorporates a novel eccentricity estimation method based on the relative power distribution among harmonics. We validate the performance of the pipeline using simulated TianQin data for a
Galactic Center XMRI composed of a brown
dwarf and Sgr A*. For a three-month observation, the pipeline successfully recovers the signal and achieves high-precision parameter estimation, including fractional uncertainties of $2.0\times10^{-6}$ in the orbital frequency, $2.9\times10^{-4}$ in the eccentricity, $2.5\times10^{-5}$ in the black-hole mass, and $5.6\times10^{-4}$ in the black-hole
spin. Our framework establishes a practical foundation for future XMRI searches with space-based detectors and highlights the potential of XMRIs as precision probes of
stellar dynamics and strong-field
gravity in the vicinity of supermassive black holes.
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All authors Tian-Xiao Wang, Yan Wang, Alejandro Torres-Orjuela, Yi-Ren Lin, Hui-Min Fan, Verónica Vázquez-Aceves, Yi-Ming Hu
Astrophysics of Galaxies
Older Ages for 23 Pre-Main Sequence Stars in Upper Scorpius Using Dynamical Mass-Constrained Stellar Evolutionary Models
Allison P. M. Towner, Joshua A. Eisner, Patrick D. Sheehan et al. (+2 more)
We present revised
stellar ages for 23 pre-main sequence K- and M-type
stars in the Upper Scorpius
star-forming region, derived by using
stellar dynamical masses to constrain isochronal ages from five pre-main sequence
stellar evolutionary models. We find that mass-constrained
stellar ages for all model sets are more consistent with the older, ~8-11 Myr age for Upper Sco derived using earlier-type
stars. Additionally, applying the independent mass constraint to isochronal ages tends to 1) increase
stellar ages for most model sets, and 2) decrease age scatter for individual sources between model sets. Models that account for global
magnetic fields consistently produce the best match to our observations: they change comparatively little when the mass constraint is applied, and produce 9-10 Myr ages under both unconstrained and mass-constrained conditions. Most standard (nonmagnetic) models produce younger ages (3-5 Myr) when unconstrained, but older ages (6-9 Myr) when constrained by dynamical mass. Our results are consistent with literature findings that suggest median disk lifetimes may be >2x longer than previously thought.
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All authors Allison P. M. Towner, Joshua A. Eisner, Patrick D. Sheehan, Lynne D. Hillenbrand, Ya-Lin Wu