Solar and Stellar Astrophysics
Local Particle Acceleration in an ICME-in-Sheath Structure Observed by Solar Orbiter
Xiaomin Chen, Chuan Li, Zigong Xu et al. (+5 more)
Local particle acceleration in the shock sheath region formed during the interaction between multiple coronal mass ejections (CMEs) is a complicated process that is still under investigation. On March 23, 2024, the successive eruption of two
magnetic flux ropes (MFRs) from the
solar active region 3614 produced twin CMEs, as identified in coronagraph images. By analyzing in-situ data from
Solar Orbiter and Wind, it is found that the primary ICME-driven shock overtook the preceding ICME, trapping it in the sheath between the shock and the primary ICME, forming the ICME-in-sheath (IIS) structure. Using
Solar Orbiter observations, we show that both electrons and ions are accelerated within the IIS. A clear enhancement of suprathermal electrons was observed at the IIS boundary, where strong flow shear and large
magnetic field variation suggest possible local electron acceleration. Electrons (>38 keV) exhibit a long-lasting enhancement in the IIS with a spectral index of ~2.2, similar to that in the shock sheath and the primary ICME, indicating a similar
solar origin. Inside both the sheath and IIS, spectra of
proton and 4He are generally consistent with the prediction of the diffusive shock acceleration, whereas Fe and O present a double power-law shape. Additionally, the Fe/O ratio in the IIS is higher than that in the sheath, and more close to the abundance of the
flare-related particles, suggesting the remnant particles of
flare confined in the IIS.
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All authors Xiaomin Chen, Chuan Li, Zigong Xu, Georgios Nicolaou, Alexander Kollhoff, George C. Ho, Robert F. Wimmer-Schweingruber, Christopher J. Owen
High Energy Astrophysical Phenomena
Performance of the Prototype Station of the IceCube Surface Array Enhancement
S. Shefali for the IceCube Collaboration
The prototype station of the Surface Array Enhancement at the IceCube
Neutrino Observatory has been taking data in its final design since 2023. This station is part of the planned extension within the footprint of the existing surface array, IceTop. One station consists of 8 scintillator detectors, 3
radio antennas, and a central DAQ. The final upgrade of the scintillation detectors and their firmware at the prototype station has extended the dynamic range and increased the data-taking up-time, thereby expanding the observation window for air showers. This contribution will discuss the performance of the upgraded prototype station after commissioning and its angular resolution capabilities when observing air showers with the scintillation detectors and in coincidence with IceTop. Furthermore, the integration of additional stations during the most recent deployment will be discussed.
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Astrophysics of Galaxies
The multimessenger view of Pulsar Timing Array black holes with the Horizon-AGN simulation
Hippolyte Quelquejay Leclere, Kunyang Li, Marta Volonteri et al. (+5 more)
We use the Horizon-AGN cosmological simulation to study the properties of supermassive black hole binaries (MBHBs) contributing most to the gravitational wave background (GWB) signal expected in the
pulsar timing array (PTA) band. We develop a pipeline to generate realistic populations of MBHBs, allowing us to estimate both the characteristic strain and GWB time series observable by PTA experiments. We identify potential continuous wave (CW) candidates standing above the background noise, using toy PTA sensitivities representing the current EPTA and future SKA. We estimate the probability of detecting at least one CW with signal-to-noise ratio $>3$ to be $4\%$ ($20\%$) for EPTA (SKA)-like sensitivities, assuming a 10-year baseline. We find the GWB to be dominated by hundreds to thousands of binaries at
redshifts in the range $0.05-1$, with chirp masses of $10^{8.5}-10^{9.5}\, M_\odot$, hosted mainly in quiescent massive
galaxies residing in
halos of mass $\sim 10^{13}\, M_\odot$. CW candidates have larger masses, lower
redshifts and are found in even more massive
halos, typical of
galaxy groups and clusters. The majority of these systems would appear as AGN rather than
quasars, because of their low Eddington ratios. Nevertheless, CW candidates with $f_{\rm Edd}>10^{-3}$ can still outshine their hosts, particularly in
radio and X-ray bands, suggesting them as the most promising route for identification. Our findings imply that optical and near-infrared searches based on light curve variability are challenging and biased toward more luminous systems. Finally, we highlight important caveats in the common method used to compare PTA observations with theoretical models. We find that GWB spectral inferences used by PTAs could be biased toward shallower slopes and higher amplitudes at $f=1/\rm yr$, thereby reducing the apparent tension between astrophysical expectations and PTA observations.
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All authors Hippolyte Quelquejay Leclere, Kunyang Li, Marta Volonteri, Stanislav Babak, Ricarda S. Beckmann, Yohan Dubois, Clotilde Laigle, Natalie A. Webb
Solar and Stellar Astrophysics
Eclipsing Stellar Flare on the Demon Star Algol Binary System Observed during the MAXI-NICER Follow-up Campaign in 2018
Kazuya Nakayama, Wataru Buz Iwakiri, Teruaki Enoto et al. (+6 more)
Algol is a well-known eclipsing binary hosting an active and variable
star that exhibits frequent
stellar flares. Here, we report our pre-planned and coordinated rapid X-ray follow-up observations of an eclipsing
flare on Algol. The Monitor of All-sky X-ray Image (MAXI) detected a
flare on Algol at 05:52 UT on 2018 July 4. Subsequently, we carried out a
prompt X-ray monitoring with the
Neutron star Interior Composition Explorer (NICER) starting at 19:45 UT on the same day, and the observation ended at 06:02 UT on 2018 July 6. During the decaying phase of the
flare, we successfully detected a 5.8-hour-long eclipse, corresponding to the secondary eclipse in which Algol A blocks the line of sight to Algol B. During the eclipse, the 2-10 keV X-ray flux is decreased to 20% level from $1.9\times10^{-10}~ \mathrm{erg~cm^{-2}~s^{-1} }$ to $4.5\times10^{-11}~ \mathrm{erg~cm^{-2}~s^{-1} }$. We found a configuration of the
flare size and location to explain the X-ray observations; e.g., the
flare occurred at the latitude 45{\deg}S of the Algol B surface with a
flare height of $1.9\times10^{11}~\mathrm{cm}$, corresponding to 0.8 times the
stellar radius of Algol B, giving 80% obscuration of the
flare loop by Algol A. The apparent absorption increase before the eclipse might originate from coronal mass ejection (CME) in the line of sight ejected during the
flare.
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All authors Kazuya Nakayama, Wataru Buz Iwakiri, Teruaki Enoto, Shun Inoue, Yuta Notsu, Keith Gendreau, Zaven Arzoumanian, Kenji Hamaguchi, Tatehiro Mihara
Solar and Stellar Astrophysics · Cross-listed from physics.plasm-ph
Linear damping of magneto-acoustic waves in two-fluid partially ionized plasmas
David Martínez-Gómez
Magneto-acoustic waves in partially ionized
plasmas are damped due to elastic collisions between charged and neutral particles. Here, we use a linearized two-fluid model to describe the influence of this collisional interaction on the properties of small-amplitude waves propagating in a uniform and static background. Mainly focusing on the case of waves generated by a periodic driver, we perform a detailed study of the dependence of the wavenumbers and damping rates on the ionization degree of the
plasma, the strength of the collisional coupling, and the angle of propagation. We describe how the different wave modes (fast, slow, acoustic) are related to the individual properties of each fluid in a wide range of physical conditions. In addition, we derive analytical approximations for the damping rates due to charge-neutral collisions in the limits of weak and strong coupling and check their range of validity in comparison with the exact numerical results. These approximations can be generally applied to a large variety of astrophysical and laboratory partially ionized
plasmas, but here we also discuss the particular application to
plasmas only composed of hydrogen.
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High Energy Astrophysical Phenomena
Revisiting electron-capture decay for Galactic cosmic-ray data
M. Borchiellini, D. Maurin and M. Vecchi
Electron-capture (EC) unstable species in
Galactic cosmic rays constrain the time elapsed between nucleosynthesis and acceleration. They have also been advocated as tracers of reacceleration or gas inhomogeneities during their transport. The number of EC-unstable species grows with mass, with an expected EC-decay impact more important for larger atomic number and lower energy. We revisit the modelling of EC decay and its detectability in the context of recent unmodulated low-energy (Voyager) and high-precision data for heavy (AMS-02) and very-heavy
nuclei (ACE-CRIS, CALET and Super-TIGER). We solve the transport equation for a multi-level configuration (up to any number of electrons attached) in the
diffusion and leaky-box models. Their decayed fractions are found to be qualitatively similar but with very different absolute fluxes. We check that the standard two-level approximation, wherein the
cosmic-ray
nucleus is fully ionised or with one electron attached, is sufficient for most situations. We find that the impact of EC-decay is negligible in current data, except possibly for fluxes or ratios involving $^{51}$Cr, $^{55}$Fe, and Co. These conclusions are robust against significant uncertainties in the attachment and stripping cross-sections. This first analysis calls for further investigation, as several forthcoming projects (e.g., TIGERISS) are targeting $Z>30$
cosmic rays.
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High Energy Astrophysical Phenomena
The variability of active galaxies: I. Broad-band noise X-ray power spectra from XMM-Newton and Swift
Mehdy Lefkir, Simon Vaughan, Mike Goad et al. (+2 more)
Accreting supermassive black holes at the centres of
galaxies are the engine of active
galactic nuclei (AGN). X-ray light curves of unabsorbed AGN show dramatic random variability on timescales ranging from seconds to years. The power spectrum of the fluctuations is usually well-modelled with a power law that decays as $1/f$ at low frequencies, and which bends to $1/f^{2-3}$ at high frequencies. The timescale associated with the bend correlates well with the mass of the black hole and may also correlate with bolometric luminosity in the `X-ray variability plane'. Because AGN light curves are usually irregularly sampled, the estimation of AGN power spectra is challenging. In a previous paper, we introduced a new method to estimate the parameters of bending power law power spectra from AGN light curves. We apply this method to a sample of 56 variable and unabsorbed AGN, observed with XMM-Newton and Swift in the $0.3-1.5$ keV band over the past two decades. We obtain estimates of the bends in 50 sources, which is the largest sample of X-ray bends in the soft band. We also find that the high-frequency power spectrum is often steeper than 2. We update the X-ray variability plane with new bend timescale measurements spanning from 7 min to 62 days. We report the detections of low-frequency bends in the power spectra of five AGN, three of which are previously unpublished: 1H 1934-063, Mkn 766 and Mkn 279.
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All authors Mehdy Lefkir, Simon Vaughan, Mike Goad, Daniela Huppenkothen, Phil Uttley
Solar and Stellar Astrophysics
The bimodal distribution of donor stars in X-ray binaries
Jia Zhang, Guo-Bao Zhang, Li-Ying Zhu et al. (+3 more)
The classification of X-ray binaries into high- and low-mass types has historically lacked a unified, data-driven quantitative criterion, and large-scale statistical studies of the donor
star population have been limited. In this work, we address this gap by compiling data for 3,964 XRBs and deriving a plentiful set of physical parameters (mass, radius, age, and evolutionary stage) for a sub-sample of 288 donor
stars using
Gaia DR3 spectral data and
stellar evolution models. We find a statistically bimodal distribution in the donor
star parameters, which is characterized by a valley at approximately 3 $M_{\odot}$ or 11,000 K. We uncover the physical mechanism behind this bimodality: a previously unreported “parallel tracks” phenomenon observed in the relationship between the donor's evolutionary stage and its fundamental parameters, such as luminosity and radius. These two tracks represent distinct main-sequence populations, and the valley between them corresponds to the sparsely populated pre- and post-main-sequence evolutionary phases.
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All authors Jia Zhang, Guo-Bao Zhang, Li-Ying Zhu, Sheng-Bang Qian, Xiao Zhou, Er-Gang Zhao
Solar and Stellar Astrophysics
Influence of kinetic effects in large-scale magnetic reconnection with multi-hierarchy simulation code KAMMUY
Keita Akutagawa, Shinsuke Imada and Munehito Shoda
Magnetic reconnection is a multiscale phenomenon where fluid- and particle-scale processes interact. The particle-in-
cell (PIC) method, capable of resolving kinetic (particle-scale) physics, is extensively used to study the kinetic effects in
magnetic reconnection. Meanwhile, because of the high computational cost, PIC simulations cannot capture the interaction between kinetic and fluid dynamics, which poses a major obstacle to understanding
magnetic reconnection in large-scale phenomena such as
solar flares. A multi-hierarchy simulation that combines Magnetohydrodynamics (MHD) and PIC provides a promising means to overcome these spatial and temporal scale gaps. We developed a multi-hierarchy simulation code KAMMUY (Kinetic And Magnetohydrodynamic MUlti-hierarchY simulation code), in which an ideal MHD simulation for a large domain and a PIC simulation for a smaller domain are solved in parallel with mutual information exchange. To validate the code, we conducted test simulations of MHD wave propagation and the shock tube problem. The results demonstrate that short-wavelength, high-frequency waves generated in the PIC region do not propagate into the MHD region, whereas MHD-scale structures propagate smoothly into the PIC region, highlighting the capability of our code for numerical studies of
magnetic reconnection. By applying the KAMMUY code to
magnetic reconnection while varying the PIC domain size, we find that the reconnection rate remains unchanged, regardless of the extent of the PIC region where the
Hall magnetic field is present. It suggests that the spatial extension of the
Hall magnetic field on the scale of $10 \sim 100 \lambda_i$ does not influence the reconnection rate.
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Solar and Stellar Astrophysics
New Level Resolved Ground and Excited State Pb III, IV, V & VI Photoionization Cross Sections for Heavy Metal Subdwarf Modeling
David J. Dougan, Matti Dorsch, Laura J. A. Scott et al. (+3 more)
High abundances of various lead (Pb) species have been identified in the spectra of many Asymptotic
Giant Branch (AGB)
stars and O- and B-type subdwarfs (sdO/B). Additional atomic data relating to Pb, and in particular photoionization cross sections, are needed to allow a greater understanding of the origin of these observed Pb abundances, and hence discern the evolutionary pathway of these
stars. We have calculated level-resolved photoionization cross sections for Pb III, IV, V and VI. Four new target structures have been developed with the General Relativistic Atomic Structure Package (GRASP0), whose corresponding energy levels, Einstein A-coefficients and oscillator strengths have been found to be in good agreement with previous experimental and theoretical sources. The photoionization cross sections calculated using the Dirac Atomic R-
matrix Codes (DARC) are available in TOPBASE format, and follow the trends expected for an isonuclear series. These new Pb data sets will now allow for the modelling of Pb abundances and line opacities under Non-Local Thermodynamic
Equilibrium (non-LTE) conditions. Using the helium-rich hot subdwarf EC 22536-5304 as a test case, we show that there are noticeable differences in the Pb line profiles across the ultraviolet and optical wavelength regions under LTE and non-LTE conditions. There is both depletion and enrichment of individual Pb species. This highlights the importance of applying non-LTE conditions when modelling EC 22536-5304, as well as other O/B-type
stars.
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All authors David J. Dougan, Matti Dorsch, Laura J. A. Scott, Niall E. McElroy, Catherine A. Ramsbottom, Connor P. Ballance
Instrumentation and Methods for Astrophysics
SETI Post-Detection Protocols: Progress Towards a New Version
Michael A. Garrett, Kathryn Denning, Leslie I. Tennen et al. (+1 more)
The International Academy of Astronautics (IAA) SETI Committee has long provided guiding principles for responding to a potential detection of a SETI signal. The foundational Declaration of Principles Concerning Activities Following the Detection of Extraterrestrial Intelligence, first formulated in 1989, has been widely recognised by the international scientific community. A supplemental set of draft protocols addressing the possibility of a reply to an extraterrestrial signal was prepared in 1995 by the IAA SETI Permanent Committee, with both documents presented in a position paper to the UN Committee on the Peaceful Uses of Outer Space in 2000. In keeping with the evolving landscape of SETI research, the IAA Declaration of Principles was streamlined and updated in 2010. Recognising the need for continued adaptation, the IAA SETI Committee established a Task Group in 2022 to re-examine the protocols in light of recent advances in search methodologies, the expansion of international participation in SETI, and the increasing complexity of the global information environment. The Group recognises the living document nature of the protocols, which will require ongoing refinement to remain relevant and effective in a rapidly changing world. A draft revised Declaration of Principles was presented at the IAC 2024 in Milan, and initial feedback was received from the community, particularly members of the IAA SETI Committee. Since then, we have continued to seek broader community input in a structured process, refining the proposed updates based on further discussions and consultations. A Revised Declaration of Principles, is presented here.
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All authors Michael A. Garrett, Kathryn Denning, Leslie I. Tennen, Carol Oliver
Instrumentation and Methods for Astrophysics
High-Precision Photometry with a scientific CMOS Camera: I Lab Testing of the Marana camera
Ioannis Apergis, Daniel Bayliss, Leonidas Asimakoulas et al. (+6 more)
Scientific CMOS cameras are becoming increasingly prevalent in modern observational astronomy. We assess the ability of CMOS image sensors technology to perform high-precision photometry with a detailed laboratory characterization of the Marana 4.2BV-11 CMOS camera. We characterise the camera in the Fastest Frame Rate (FFR) and High Dynamic Range (HDR) modes. Our evaluation includes read noise, dark current, photo response and dark signal non-uniformities,
quantum efficiency and window transmittance. The read noise is found to be 1.577\,e$^-$ for the FFR mode. For the HDR mode the read noise floor is measured to be 1.571\,e$^-$ for signal levels below approximately 1800\,e$^-$. The bias level shows dark signal non-uniformities with values of 0.318\,e$^-$ and 0.232\,e$^-$ for FFR and HDR mode, respectively. Pixel well capacity reached 2366 e$^-$pix$^{-1}$ for the FFR mode and 69026 e$^-$pix$^{-1}$ with a dynamic range of 93\,dB for the HDR mode. The camera demonstrates good linearity, yielding linearity errors of 0.099\,% for FFR mode and 0.122\,% for HDR mode. The uniformity across the image arrays show a photo response non-uniformity of 0.294\,% for the FFR mode and 0.131\,% for the HDR mode. The dark current displays a noticeable glow pattern, resulting in mean dark current levels of $1.674\pm0.011$\, \eps\, for the FFR mode and $1.617\pm0.008$\,\eps\, for the HDR mode at a constant temperature of -25\,$^\circ$C. We measured the
quantum efficiency across the visible spectrum, with a peak of of >95\,% at 560\,nm. Our tests indicate that the Marana CMOS camera is potentially capable of performing precise photometry.
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All authors Ioannis Apergis, Daniel Bayliss, Leonidas Asimakoulas, Paul Chote, James McCormac, Morgan A. Mitchell, Sam Gill, Philip G. Steen, Peter Wheatley
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
ALP couplings to muons and electrons: a comprehensive analysis of supernova bounds
Ricardo Z. Ferreira, M.C. David Marsh and Eike Ravensburg
We provide a comprehensive analysis of the phenomenology of
axion-like particles (ALPs) produced in core-collapse
supernovae (ccSNe) through interactions with electrons and
muons, both of which have a non-negligible abundance in the SN
plasma. We identify and calculate six significant ALP-production channels, two of which are loop-level processes involving
photons. We then examine several observational constraints on the ALP-electron and ALP-
muon parameter spaces. Those include the bounds on anomalous cooling, energy deposition, decay into
photons, diffuse gamma rays, and the 511 keV line. Our results provide updated and robust constraints on ALP couplings to electrons and
muons from an improved treatment of production and absorption processes. Furthermore, we quantify the uncertainties of the results by using three state-of-the-art
supernova models based on two independent simulation codes, finding that constraints vary by factors of O(2-10).
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High Energy Astrophysical Phenomena · Cross-listed from hep-th
The Stochastic Schwinger Effect
Lucas Vicente García-Consuegra and Azadeh Maleknejad
We formulate a
stochastic generalisation of the Schwinger effect, extending pair production to statistically fluctuating gauge-field backgrounds. Our approach captures realistic field configurations that are transient, inhomogeneous, and
stochastic, as commonly encountered in cosmological and high-energy astrophysical settings. Using the effective action formalism, we compute the
vacuum decay rate and number density of charged particles, obtaining closed-form analytical expressions for both scalar and fermionic cases. To isolate the essential physics, the analysis is performed in flat spacetime and at zero temperature, providing a controlled setting in which
curvature and thermal effects can be neglected. As a proof of concept, we present representative phenomenological examples relevant to astrophysical
plasmas and early-Universe-motivated scenarios.
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Cosmology and Nongalactic Astrophysics
Built-in precision: Improving cluster cosmology through the self-calibration of a galaxy cluster sample
Junhao Zhan and Christian L. Reichardt
We examine the potential improvements in constraints on the dark energy equation of state parameter $w$ and matter density $\Omega_M$ from using clustering information along with number counts for future samples of thermal Sunyaev-Zel'dovich selected
galaxy clusters. We quantify the relative improvement from including the clustering power spectrum information for three cluster sample sizes from 33,000 to 140,000 clusters and for three assumed priors on the mass slope and
redshift evolution of the mass-observable relation. As expected, clustering information has the largest impact when (i) there are more clusters and (ii) the mass-observable priors are weaker. For current knowledge of the cluster mass-observable relationship, we find the addition of clustering information reduces the uncertainty on the dark energy equation of state, $\sigma(w)$, by factors of $1.023\pm 0.007$ to $1.0790\pm 0.011$, with larger improvements observed with more clusters. Clustering information is more important for the matter density, with $\sigma(\Omega_M)$ reduced by factors of $1.068 \pm 007$ to $1.145 \pm 0.012$. The improvement in $w$ constraints from adding clustering information largely vanishes after tightening priors on the mass-observable relationship by a factor of two. For weaker priors, we find clustering information improves the determination of the cluster mass slope and
redshift evolution by factors of $1.389 \pm 0.041$ and $1.340 \pm 0.039$ respectively. These findings highlight that, with the anticipated surge in cluster detections from next generation surveys, self-calibration through clustering information will provide an independent cross-check on the mass slope and
redshift evolution of the mass-observable relationship as well as enhancing the precision achievable from cluster cosmology.
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Astrophysics of Galaxies
Accounting for the absence of anomalous microwave emission in the M 31 halo
Francesco De Paolis, Faryal Naseem and Noraiz Tahir
The discovery of a temperature asymmetry in the
cosmic microwave background (CMB) data towards various
galaxies has opened a window for a deeper comprehension of
galactic halos. A crucial step forward is that of estimating the fraction of missing
baryons in the
halos, but it relies on understanding the real cause of the observed CMB temperature asymmetry since many effects might give a non-negligible contribution. Here, we analyzed the contribution played by the anomalous microwave emission (AME) from
halo dust grains in the
halo of the M 31
galaxy. Assuming either amorphous carbon and silicates
dust grains with size ranging from $0.01~\mu$m to about $0.3~\mu$m and mass in the range $10^{-14} - 10^{-13}$ g, we estimated the total mass, distribution, and diffuse emission in the $100\,\mu$m band of the Infrared Astronomical Satellite (IRAS). Then, we estimated the temperature asymmetry induced by the rotation of the M 31
halo and compared the obtained values with the Planck's SMICA-processed data. We find that the AME cannot account for the measured CMB temperature asymmetry, with its contribution constrained to $\lesssim 7\%$, thereby indicating that additional physical mechanisms must be responsible for the observed signal.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
A unified model of dark energy and inflation from the Markov-Mukhanov action
Hrishikesh Chakrabarty and Daniele Malafarina
We propose a unified model of dark energy and inflation through the Markov-Mukhanov modification of the Einstein-
Hilbert action, where the matter sector is coupled to
gravity via a scalar coupling function depending only on the energy density of the matter content. We assume that the coupling function encodes the UV corrections to the standard model of cosmology and we determine the form of the coupling that allows for the dark energy component to be dynamical and act as the inflaton field in the early universe. Interestingly we show that our model, in order to account for inflation, prefers a dark energy equation of state with $w$ close but not equal to $-1$ in agreement with the latest DESI data.
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Earth and Planetary Astrophysics · Cross-listed from math.OC
Recursive Target Body Approach for Low-Thrust Multiple Gravity-Assist Sequence Optimization
Sean Cowan and Ron Noomen
This work aims to automate the design of Multiple
Gravity-Assist (MGA) transfers between
planets using low-thrust propulsion. In particular, during the preliminary design phase of space missions, the combinatorial complexity of MGA sequencing is very large, and current optimization approaches require extensive experience and can take many days to simulate. Therefore, a novel optimization approach is developed here – called the Recursive Target Body Approach (RTBA) – that uses the hodographic-shaping low-thrust trajectory representation together with a unique combination of tree-search methods to automate the optimization of MGA sequences. The approach gradually constructs the optimal MGA sequence by recursively evaluating the optimality of subsequent
gravity-assist targets. Another significant contribution to the novelty of this work is the use of parallelization in an original way involving the Generalized Island Model (GIM) that enables the use of new figures of merit to further increase the robustness and accelerate the convergence. An Earth-Jupiter transfer with a maximum of three
gravity assists is considered as a reference problem. The RTBA takes 21.5 hours to find an EMJ transfer with 15.4 km/s $\Delta V$ to be the optimum. Extensive tuning improved the quality of the MGA trajectories substantially, and as a result a robust low-thrust trajectory optimization could be ensured. A distinct group of highly fit MGA sequences is consistently found that can be passed on to a higher-fidelity method. In conclusion, the RTBA can automatically and reliably be used for the preliminary optimization of low-thrust MGA trajectories.
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Cosmology and Nongalactic Astrophysics
Evidence for the dynamical dark energy with evolving Hubble constant
Yi-Ying Wang, Yin-Jie Li and Yi-Zhong Fan
Hubble constant tension, together with the recent indications of dynamical dark energy proposed from the Dark Energy Spectroscopic Instrument (DESI)
baryon acoustic oscillation (BAO) measurements, poses significant challenges to the standard cosmological model. We investigate the possible
redshift evolution of dark energy and the Hubble constant through a data-driven approach, and assess whether such
evolution can alleviate the Hubble constant tension. We perform a model-independent reconstruction of the dark-energy equation of state $w(z)$, jointly with an evolving Hubble constant $H_0(z)$. The analysis combines the DESI DR2 BAO
dataset with multiple Type Ia
supernova samples and evaluates the statistical preference for the reconstructed model using
Bayesian evidence. The reconstructed $w(z)$ varies with
redshift and exhibits two potential phantom crossings at $z\sim0.5$ and $z\sim1.5$. Meanwhile, $H_0$ decreases continually from local to high
redshift, alleviating the Hubble constant tension effectively. The joint $w(z)$-$H_0(z)$ model is favored over the $w$CDM ($\Lambda$CDM) framework, with a logarithmic Bayes factor $\ln \boldsymbol{\mathcal B}= 5.04~(8.53)$. The results remain stable under different prior choices and
dataset combinations. Our data-driven reconstructions suggest
redshift evolution in both $w(z)$ and $H_0(z)$, offering a potential route to mitigate the Hubble constant tension. Future BAO measurements from Euclid and next-generation CMB experiments will provide critical tests of these results and bring deeper insights into the nature of dark energy and the
evolution of
cosmic expansion.
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Astrophysics of Galaxies
Dust extinction map of the Galactic plane based on the UKIDSS survey data
Miaomiao Zhang, Jouni Kainulainen, He Zhao et al. (+5 more)
Dust plays a critical role in the study of the interstellar medium (ISM). Extinction maps derived from optical surveys often fail to capture regions with high column density due to the limited photometric depth in optical wavelengths. To address these limitations, we developed the XPNICER method based on near-infrared (NIR) photometric survey data. This method combines the previously established PNICER and Xpercentile techniques, enabling effective mitigation of foreground contamination and improved handling of complex
dust structures in the
Galactic plane, which thus can provide more accurate extinction estimates, particularly in highly obscured regions. By applying XPNICER to the
Galactic Plane Survey from the UKIRT Infrared Deep Sky Survey, we have generated a series of two-dimensional (2D)
dust extinction maps that span roughly 1800 deg2 of the
Galactic plane (0< l < 110deg and 140< l < 232deg, |b| < 5deg). These maps, with spatial resolutions between 30arcsec and 300arcsec, can trace extinction up to Av ~ 30-40 mag. This new approach offers higher spatial resolution and better detection of high-extinction regions compared to previous large-scale
dust-based maps of the
Galactic plane, providing an independent and complementary measure of
dust column densities.
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All authors Miaomiao Zhang, Jouni Kainulainen, He Zhao, Yang Su, Min Fang, Yuehui Ma, Zhiwei Chen, Zhibo Jiang
High Energy Astrophysical Phenomena
Is GW231123 a hierarchical merger?
Lachlan Passenger, Sharan Banagiri, Eric Thrane et al. (+4 more)
The binary black hole merger GW231123 is both the most massive gravitational-wave event observed and has the highest component
spins measured to date. The dimensionless
spins of the more massive (primary) and less massive (secondary) black holes are measured to be $\chi_1 = 0.90^{+0.10}_{-0.19}$ and $\chi_2 = 0.80^{+0.20}_{-0.51}$ ($90\%$ credible intervals), respectively. Its large mass and extremal
spins are challenging to explain through standard binary
stellar physics, though a flurry of hypothetical scenarios have been proposed. Hierarchical assembly - i.e., mergers of black holes that are themselves formed from previous generations of mergers - is generally a promising way to explain massive and rapidly spinning black holes. Here, we investigate the possibility that GW231123 was assembled hierarchically in a dense
star cluster as the merger of two second-generation black holes. Taking the inferred
spin values at face value, we find that it is possible ($p\approx 5\%$) that a compact binary with component
spins like GW231123 could form in a cluster from hierarchical assembly.
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All authors Lachlan Passenger, Sharan Banagiri, Eric Thrane, Paul D. Lasky, Angela Borchers, Maya Fishbach, Claire S. Ye
Solar and Stellar Astrophysics
Combining spectral analysis and narrow band pass filtering to predict solar cycle parameters in the next solar grand minimum
Ian Edmonds and Peter Killen
We introduce a new method for predicting sunspot number (SSN) that, based on successful back projections, can predict features of the SSN several
solar cycles in advance. The method applies
Fourier analysis to the annual SILSO SSN record, from 1700.5 to 2023.5, to identify in the spectrum, four strong components in the decadal, 10 to 11 year period, range and four weaker components in the octal, 8 to 9 year period, range. The time variation of each component is isolated by a new method of narrow band pass filtering. The components are fitted with sinusoids at the beginning/end of the SSN record for back/forward projection. Back projection successfully replicated the long term features of the Maunder Minimum. Forward projection predicts a Maunder-like grand minimum from 2030 to 2110, encompassing
solar cycles 26 to 35. Details of short term features of SSN within the grand minimum are less certain. The octal contribution to SSN is shown to occasionally exceed the decadal contribution both in the projection and also within the observational record. Predicted SSN amplitudes for cycles 26 and 28 are about 50, about half the amplitude of cycles 24 and 25. The amplitude of cycle 27 is difficult to forecast as it may emerge as a double peak of cycle 26 rather than as two separate cycles 26 and 27. Amplitudes forecast for cycles 29 to 33 are, on average, about half the amplitude of cycles 26 and 27 with the lowest cycle of the grand minimum, cycle 30, occurring around 2070. Interference between the octal and decadal components evident in the SSN spectrum are shown to result in micro changes in SSN such as the Waldmeier Effect. Inter group results in the occurrence of grand
solar minima and maxima. Intra component group interference results in long term variation grand maxima/minima patterns that may relate to the occurrence of long term
climate variability.
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Solar and Stellar Astrophysics
Water Snowline in Young Stellar Objects with Various Density Structures Using Radiative Transfer Models
Young-Jun Kim, Jeong-Eun Lee, Giseon Baek et al. (+1 more)
Tracing the water snowline in low-mass young
stellar objects (YSOs) is important because
dust grain growth is promoted and the chemical composition varies at the water snowline, which influences
planet formation and its properties. In protostellar envelopes, the water snowline can be estimated as a function of luminosity using a relation derived from radiative transfer models, and these predictions are consistent with observations. However, accurately estimating the water snowline in protoplanetary disks requires new relations that account for the disk structure. We present the relations between luminosity and water snowline using the
dust continuum radiative transfer models with various density structures. We adopt two-dimensional density structures for an envelope-only model (Model E), an envelope+disk+cavity model (Model E+D), and a protoplanetary disk model (Model PPD). The relations between the water snowline, where T_
dust = 100 K, and the total luminosity, ranging 0.1-1,000
solar luminosity, are well fitted by a power-law relation, R_snow=a * (L/L_
solar)^p au. The factor a decreases with increasing disk density, while the power index p has values around 0.5 in all models. As the disk becomes denser, the water snowline forms at smaller radii even at the same luminosity, since dense
dust hinders
photon propagation. We also explore the effect of viscous heating on the water snowline. In Model PPD with viscous heating, the water snowline shifts outward by a few au up to 15 au, increasing the factor a and decreasing the power index p. In Model E+D with lower disk mass, the effect of viscous heating is negligible, indicating that the disk mass controls the effect. The discrepancy between our models and direct observations provides insights into the recent outburst event and the presence of a disk structure in low-mass YSOs.
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All authors Young-Jun Kim, Jeong-Eun Lee, Giseon Baek, Seokho Lee
Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Glitch noise classification in KAGRA O3GK observing data using unsupervised machine learning
Shoichi Oshino, Yusuke Sakai, Marco Meyer-Conde et al. (+5 more)
Gravitational wave interferometers are disrupted by various types of nonstationary noise, referred to as glitch noise, that affect data analysis and interferometer sensitivity. The accurate identification and classification of glitch noise are essential for improving the reliability of gravitational wave observations. In this study, we demonstrated the effectiveness of unsupervised machine learning for classifying images with nonstationary noise in the KAGRA O3GK data. Using a variational autoencoder (VAE) combined with spectral clustering, we identified eight distinct glitch noise categories. The latent variables obtained from VAE were dimensionally compressed, visualized in three-dimensional space, and classified using spectral clustering to better understand the glitch noise characteristics of KAGRA during the O3GK period. Our results highlight the potential of unsupervised learning for efficient glitch noise classification, which may in turn potentially facilitate interferometer upgrades and the development of future third-generation gravitational wave observatories.
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All authors Shoichi Oshino, Yusuke Sakai, Marco Meyer-Conde, Takashi Uchiyama, Yousuke Itoh, Yutaka Shikano, Yoshikazu Terada, Hirotaka Takahashi
Solar and Stellar Astrophysics
Estimation of gravitational wave from solar emerging magnetic flux tube
Siqi Guan, Shangbin Yang and Xiao Guo
This study investigates the gravitational waves (GWs) generated by the emergence of
magnetic flux tubes in the
solar convection zone. We focus on the upward buoyancy of
magnetic flux tubes, which leads to significant
magnetic activity and the formation of active region sunspots. This study adopts parameters representative of a moderate-sized
solar active region to estimate the GWs generated by the emergence of
magnetic flux tubes. Our results indicate that the GW strain amplitude, achievable through signal superposition and detection at close proximity (e.g., approximately one
solar radius from the
solar surface), may reach $\sim$10$^{-29}$. The characteristic GW frequency is estimated at $\sim$10$^{-5}$ Hz, placing it at the high-frequency end of the sensitivity band of
Pulsar Timing Array (PTA) methods. However, the estimated strain amplitudes remain orders of magnitude below the sensitivity thresholds of current and foreseeable gravitational wave detectors. Notably, reducing the cadence $\Delta t$ of
Pulsar Timing Array (PTA) observations to approximately 2 hours ($\Delta t = 2\text{hours}$) would raise the maximum detectable frequency to about $5.8 \times 10^{-5} \text{Hz}$, thereby encompassing the dominant spectral component of
solar activity-related GWs predicted in this study, offering a potential pathway for future detection. Successful detection in the future may help to predict the super
solar active region emergence in space weather
forecasting.
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Earth and Planetary Astrophysics
Demonstrating Exoplanet Transit Photometry from Space with a 15-mm Aperture Optical Navigation Camera on Hayabusa2
Koki Yumoto, Toru Kouyama, Manabu Yamada et al. (+14 more)
Observations of
exoplanet transits by small satellites have gained increasing
attention for reducing detection biases. However, no unambiguous detection of an
exoplanet has yet been demonstrated using optics with apertures smaller than 60 mm. Here, we investigated the detectability of
exoplanet transits using the telescopic Optical
Navigation Camera (ONC-T) onboard the Hayabusa2 spacecraft, which has an effective aperture of only 15 mm. We conducted transit observations of the hot Jupiters WASP-189 b and MASCARA-1 b, collecting data for ten and four events, respectively. The transit signal was detected with a signal-to-noise ratio (SNR) of 13 for WASP-189 b and 8 for MASCARA-1 b for each event. Stacking all events improved the SNR to 40 and 16, respectively. The transit mid-times of each event were measured with a precision of 6 minutes and were consistent with Transiting
Exoplanet Survey Satellite (TESS) data to within 2 minutes. The
planet-to-
star radius ratio was determined with an absolute precision of 0.004 (6% relative) and agreed with TESS results to within 0.002 (3% relative). The recent ONC-T and TESS data enabled an update to the planetary ephemerides. We report a 4 sigma discrepancy between the updated orbital period of MASCARA-1 b and previously reported values. ONC-T sets a new record for the smallest-aperture instrument to detect an
exoplanet transit from space, advancing the frontier of
exoplanet science with miniature instrumentation. Our results suggest that optics as small as ONC-T may be capable of detecting transiting long-period Jupiters: a population that remains underrepresented in current surveys.
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All authors Koki Yumoto, Toru Kouyama, Manabu Yamada, Yuya Mimasu, Tomokatsu Morota, Yuichiro Cho, Yasuhiro Yokota, Masahiko Hayakawa, Anthony Arfaux, Eri Tatsumi, Moe Matsuoka, Naoya Sakatani, Sumito Shimomura, Shingo Kameda, Satoshi Tanaka, Keigo Enya, Seiji Sugita
Instrumentation and Methods for Astrophysics
An On-Sky Atmospheric Calibration of SPT-SLIM
K. R. Dibert, M. Adamic, A. J. Anderson et al. (+26 more)
We present the methodology and results of the on-sky responsivity calibration of the South Pole
Telescope Shirokoff Line Intensity Mapper (SPT-SLIM). SPT-SLIM is a pathfinder line intensity mapping experiment utilizing the on-chip spectrometer technology, and was first deployed during the 2024-2025 Austral Summer season on the South Pole
Telescope. During the two-week on-sky operation of SPT-SLIM, we performed periodic measurements of the detector response as a function of the
telescope elevation angle. Combining these data with atmospheric opacity measurements from an on-site atmospheric tipping radiometer, simulated South Pole atmospheric spectra, and measured detector spectral responses, we construct estimates for the responsivity of SPT-SLIM detectors to sky loading. We then use this model to calibrate observations of the moon taken by SPT-SLIM, cross-checking the result against the known brightness temperature of the Moon as a function of its phase.
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All authors K. R. Dibert, M. Adamic, A. J. Anderson, P. S. Barry, B. A. Benson, C. S. Benson, E. Brooks, J. E. Carlstrom, T. Cecil, C. L. Chang, M. Dobbs, K. Fichman, K. S. Karkare, G. K. Keating, A. M. Lapuente, M. Lisovenko, D. P. Marrone, J. Montgomery, T. Natoli, Z. Pan, A. Rahlin, G. Robson, M. Rouble, G. Smecher, V. Yefremenko, M. R. Young, C. Yu, J. A. Zebrowski, C. Zhang
Instrumentation and Methods for Astrophysics
Design and Performance of the SPT-SLIM Receiver Cryostat
M. R. Young, M. Adamic, A. J. Anderson et al. (+28 more)
The South Pole
Telescope Shirokoff Line Intensity Mapper (SPT-SLIM) is a millimeter-wavelength line-intensity mapping experiment, which was deployed on the South Pole
Telescope (SPT) during the 2024-2025 Austral summer season. This pathfinder experiment serves to demonstrate the on-sky operation of multi-pixel on-chip spectrometer technology. We report on the cryogenic performance of the SPT-SLIM receiver for the first year of commissioning observations. The SPT-SLIM receiver utilizes an Adiabatic Demagnetization Refrigerator (ADR) for cooling the focal plane of superconducting filterbank spectrometers to a temperature of 150 mK. We demonstrate stable thermal performance of the focal plane module during observations consistent with thermal modeling, enabling a cryogenic operating efficiency above 80%. We also report on the receiver control system design utilizing the Observatory Control System (OCS) platform for automated cryogenic operation on the SPT.
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All authors M. R. Young, M. Adamic, A. J. Anderson, P. S. Barry, B. A. Benson, C. S. Benson, E. Brooks, J. E. Carlstrom, T. Cecil, C. L. Chang, K. R. Dibert, M. Dobbs, K. Fichman, M. Hollister, K. S. Karkare, G. K. Keating, A. M. Lapuente, M. Lisovenko, D. P. Marrone, D. Mitchell, J. Montgomery, T. Natoli, Z. Pan, A. Rahlin, G. Robson, M. Rouble, G. Smecher, V. Yefremenko, C. Yu, J. A. Zebrowski, C. Zhang
Instrumentation and Methods for Astrophysics
Hierarchical Simulation-Based Inference of Supernova Power Sources and their Physical Properties
Edgar P. Vidal, Alexander T. Gagliano and Carolina Cuesta-Lazaro
Time domain surveys such as the Vera C. Rubin Observatory are projected to annually discover millions of astronomical transients. This and complementary programs demand fast, automated methods to constrain the physical properties of the most interesting objects for spectroscopic follow up. Traditional approaches to likelihood-based inference are computationally expensive and ignore the multi-component energy sources powering astrophysical phenomena. In this work, we present a hierarchical simulation-based inference model for multi-band light curves that 1) identifies the energy sources powering an event of interest, 2) infers the physical properties of each subclass, and 3) separates physical anomalies in the learned
embedding space. Our architecture consists of a
transformer-based light curve summarizer coupled to a flow-matching regression module and a categorical classifier for the physical components. We train and test our model on $\sim$150k synthetic light curves generated with $\texttt{MOSFiT}$. Our network achieves a 90% classification accuracy at identifying energy sources, yields well-calibrated posteriors for all active components, and detects rare anomalies such as
tidal disruption events (TDEs) through the learned latent space. This work demonstrates a scalable joint framework for population studies of known transients and the discovery of novel populations in the era of Rubin.
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Astrophysics of Galaxies
Molecular gas content of gravitational-lensed quasars at cosmic noon
Zhiyuan Zheng, Yong Shi, Qiusheng Gu et al. (+4 more)
Star-forming activity in the host
galaxies of high-
redshift quasars is crucial to understanding the connection between supermassive black hole (SMBH) activity and
galaxy evolution. While most existing studies are biased toward luminous
quasars, we conduct carbon monoxide (CO) observations of 17 gravitationally lensed
quasars that have four images using the IRAM 30m
telescope to investigate the molecular gas content of moderate- to low-luminosity
quasars. CO emissions are detected in five out of 17
quasars, corresponding to a detection rate of about 30%. Analysis of their
star formation activity reveals that these
quasars live in gas-rich environments but exhibit weaker starbursts and lower
star formation efficiencies compared to other luminous high-
redshift quasars. In addition, the CO spectral line energy distributions of the two
quasars (SDSS J0924+0219, SDSS J1330+1810) are also consistent with mild
star formation instead of extreme starbursts. These results suggest that these lensed
quasars reside in weaker starburst environments.
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All authors Zhiyuan Zheng, Yong Shi, Qiusheng Gu, Zhi-Yu Zhang, Junzhi Wang, Yanmei Chen, Fuyan Bian