Journal Description
Galaxies
Galaxies
is an international, peer-reviewed, open access journal on astronomy, astrophysics, and cosmology published bimonthly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, ESCI (Web of Science), Astrophysics Data System, INSPIRE, Inspec, and other databases.
- Journal Rank: JCR - Q2 (Astronomy and Astrophysics) / CiteScore - Q2 (Astronomy and Astrophysics)
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 23.4 days after submission; acceptance to publication is undertaken in 4.8 days (median values for papers published in this journal in the first half of 2025).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Impact Factor:
3.8 (2024);
5-Year Impact Factor:
3.1 (2024)
Latest Articles
Testing CCC+TL Cosmology with Galaxy Rotation Curves
Galaxies 2025, 13(5), 108; https://doi.org/10.3390/galaxies13050108 (registering DOI) - 12 Sep 2025
Abstract
This paper aims to explore whether astrophysical observations, primarily galaxy rotation curves, result from covarying coupling constants (CCC) rather than from dark matter. We have shown in earlier papers that cosmological observations, such as supernovae type 1a (Pantheon+), the small size of galaxies
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This paper aims to explore whether astrophysical observations, primarily galaxy rotation curves, result from covarying coupling constants (CCC) rather than from dark matter. We have shown in earlier papers that cosmological observations, such as supernovae type 1a (Pantheon+), the small size of galaxies at cosmic dawn, baryon acoustic oscillations (BAO), the sound horizon in the cosmic microwave background (CMB), and time dilation effect, can be easily accounted for without requiring dark energy and dark matter when coupling constants are permitted to evolve in an expanding Universe, as predicted by Dirac, and the redshift is considered jointly due to the Universe’s expansion and Zwicky’s tired light (TL) effect. Here, we show that the CCC parameter α is responsible for generating the illusion of dark matter and dark energy, which we call α-matter and α-energy, and is influenced by the baryonic matter density distribution. While cosmologically α is a constant determined for the homogenous and isotropic Universe, e.g., by fitting Pantheon+ data, it can vary locally due to the extreme anisotropy of the matter distribution. Thus, in high baryonic density regions, one expects -matter and α-energy densities to be relatively low and vice versa. We present its application to a few galaxy rotation curves from the SPARC database and find the results promising.
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(This article belongs to the Special Issue Alternative Interpretations of Observed Galactic Behaviors)
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Open AccessArticle
The Murchison Widefield Array Enters Adolescence: A Personal Review of the Early Years of Operations
by
Steven J. Tingay
Galaxies 2025, 13(5), 107; https://doi.org/10.3390/galaxies13050107 - 11 Sep 2025
Abstract
The Murchison Widefield Array (MWA) is a low frequency radio interferometer designed and developed by an international consortium, operated on behalf of the consortium by Curtin University. The MWA is a Precursor for the low frequency Square Kilometre Array (SKA) and is located
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The Murchison Widefield Array (MWA) is a low frequency radio interferometer designed and developed by an international consortium, operated on behalf of the consortium by Curtin University. The MWA is a Precursor for the low frequency Square Kilometre Array (SKA) and is located at the SKA site in Western Australia, Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory. Commencing science operations in 2013 after an extended development period, the MWA has performed observations over a wide set of science objectives, has been upgraded multiple times, and has played a fundamental role in the development of the low frequency SKA. As MWA Program Manager from 2008 to 2011, as Director from 2011 until 2015, and then again from 2021 to the present, I describe some personal reflections on the MWA’s activities and successes in these different dimensions, as well as my view of some of the approaches that have enabled these successes. I offer some of the lessons I’ve perceived over the last 17+ years in the project.
Full article
(This article belongs to the Special Issue Recent Advances in Radio Astronomy)
Open AccessArticle
Dynamics of Compact Stellar Solutions Admitting Anisotropic Fluid: A Comparative Analysis of GR and Non-Conserved Rastall Gravity
by
Tayyab Naseer, Muhammad Sharif, Fatima Chand, Baiju Dayanandan and Ali Elrashidi
Galaxies 2025, 13(5), 106; https://doi.org/10.3390/galaxies13050106 - 9 Sep 2025
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This study proposes a couple of analytical solutions that characterize the anisotropic dense celestial bodies within the Rastall-Rainbow theoretical framework. The analysis assumes a static spherically symmetric matter distribution and derives the corresponding modified field equations. By utilizing well-established radial metric functions and
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This study proposes a couple of analytical solutions that characterize the anisotropic dense celestial bodies within the Rastall-Rainbow theoretical framework. The analysis assumes a static spherically symmetric matter distribution and derives the corresponding modified field equations. By utilizing well-established radial metric functions and merging them with the two principal pressures, we obtain differential equations related to the time component. Subsequently, we perform the integration of these equations to determine the remaining geometric quantity that encompasses various integration constants. The proposed interior solutions are then matched with the Schwarzschild exterior metric at the boundary of the compact object, facilitating the determination of the constants. Additionally, the incorporation of the non-minimal coupling parameter into these constants is accomplished by enforcing the null radial pressure at the boundary. Afterwards, we rigorously examine the physical characteristics and critical stability conditions of the formulated models under observational data from two pulsars, say 4U 1820-30 and LMC X-4. It is concluded that our models are well-aligned with essential criteria required to ensure the physical viability of stellar structures, subject to specific parametric values.
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Open AccessArticle
Photometric Monitoring of the First Eclipsing Binary Be Star: V658 Car
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Tajan H. de Amorim, Alex C. Carciofi, Alexandre Zanardo, Carlos Colesanti, Cristóvão Jacques, Denis Kulh, João Antonio Mattei, Marcelo Domingues, Marco Rocca, Sérgio Silva, Tasso Napoleão and Jonathan Labadie-Bartz
Galaxies 2025, 13(5), 105; https://doi.org/10.3390/galaxies13050105 - 8 Sep 2025
Abstract
V658 Car is the first known eclipsing binary system involving a classical Be star and an sdOB companion, offering a unique opportunity to study disk physics and binary interactions in unprecedented detail. From TESS data and multi-color observations from the comissão para a
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V658 Car is the first known eclipsing binary system involving a classical Be star and an sdOB companion, offering a unique opportunity to study disk physics and binary interactions in unprecedented detail. From TESS data and multi-color observations from the comissão para a colaboração entre profissionais e amadores collaboration, we analyze the system’s color–magnitude diagram and compare it with radiative transfer models that include the Be star, its circumstellar disk, and the sdOB companion. While the stellar eclipses are well reproduced, two features observed in the multi-color photometry challenge the current modeling paradigm: the discrepancy between the observed reddening and the modeled blueing during the first attenuation phase and the complete lack of modeled attenuation around the second stellar eclipse. These issues highlight the need for more sophisticated modeling approaches to capture the complex interplay between disk opacity and binary dynamics.
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(This article belongs to the Special Issue Circumstellar Matter in Hot Star Systems)
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One-Dimensional Analytical Solutions of the Transport Equations for Incompressible Magnetohydrodynamic (MHD) Turbulence
by
Bingbing Wang, Gary P. Zank, Laxman Adhikari and Swati Sharma
Galaxies 2025, 13(5), 104; https://doi.org/10.3390/galaxies13050104 - 3 Sep 2025
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We derive one-dimensional (1D) analytical solutions for the transport equations of incompressible magnetohydrodynamic (MHD) turbulence, including the Elsässer energies and the correlation lengths. The solutions are suitable for an arbitrary given background convection speed and Alfvén speed profiles but require near equipartition of
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We derive one-dimensional (1D) analytical solutions for the transport equations of incompressible magnetohydrodynamic (MHD) turbulence, including the Elsässer energies and the correlation lengths. The solutions are suitable for an arbitrary given background convection speed and Alfvén speed profiles but require near equipartition of turbulent kinetic energy and magnetic field energy. These analytical solutions provide a simple tool to investigate the evolution of turbulence and resulting energetic particle diffusion coefficients in various space and astrophysical environments that possess simple geometry.
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Open AccessReview
A Review of Lunar Environment and In-Situ Resource Utilization for Achieving Long-Term Lunar Habitation
by
Chang Wang, Guoqing Zhang, Yaohui Wang and Lei Song
Galaxies 2025, 13(5), 103; https://doi.org/10.3390/galaxies13050103 - 3 Sep 2025
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The Moon’s unique environment, strategic position, and resource abundance make it a key target for deep space exploration. As lunar missions evolve from research to long-term habitation, leveraging local resources is essential to reduce dependence on Earth-based supply chains. Despite significant studies on
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The Moon’s unique environment, strategic position, and resource abundance make it a key target for deep space exploration. As lunar missions evolve from research to long-term habitation, leveraging local resources is essential to reduce dependence on Earth-based supply chains. Despite significant studies on the lunar environment and in-situ resource utilization (ISRU), a unified framework that integrates these findings remains lacking. This article addresses this gap by systematically reviewing and synthesizing current research to support sustainable lunar development. It first explores the use of extreme lunar environmental factors such as thermal gradients, weak magnetic fields, subsurface cavities, and geographic advantages. It then examines lunar water and mineral resource development, highlighting methods for detection, extraction, purification, and storage, alongside strategies for utilizing various minerals. The article further reviews recent progress in in-situ manufacturing, construction technologies, energy regeneration, and closed-loop life-support systems vital for lunar base establishment. These advances are crucial for creating sustainable infrastructure and maintaining life on the Moon. Finally, the paper outlines the challenges and limitations associated with ISRU and offers perspectives on future directions, aiming to inform the design of next-generation lunar missions and facilitate permanent human presence on the Moon.
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Open AccessReview
Jet Feedback on kpc Scales: A Review
by
Dipanjan Mukherjee
Galaxies 2025, 13(5), 102; https://doi.org/10.3390/galaxies13050102 - 2 Sep 2025
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Relativistic jets from AGN are an important driver of feedback in galaxies. They interact with their environments over a wide range of physical scales during their lifetime, and an understanding of these interactions is crucial for unraveling the role of supermassive black holes
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Relativistic jets from AGN are an important driver of feedback in galaxies. They interact with their environments over a wide range of physical scales during their lifetime, and an understanding of these interactions is crucial for unraveling the role of supermassive black holes in shaping galaxy evolution. The impact of such jets has been traditionally considered in the context of heating large-scale environments. However, in the last few decades, there has been additional focus on the immediate impact of jet feedback on the host galaxy itself. In this review, we outline the development of various numerical simulations from the onset of research on jets to the present day, where sophisticated numerical techniques have been employed to study jet feedback, including a range of physical processes. The jets can act as important agents of energy injection into a host’s ISM, as confirmed in both observations of multi-phase gas as well as in simulations. Such interactions have the potential to impact the kinematics of the gas as well as star formation. We summarize recent results from simulations of jet feedback on kpc scales and outline the broader implications for observations and galaxy evolution.
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Open AccessArticle
Determination of Orbital Parameters of Binary Star Systems Using the MCMC Method
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Nadezhda L. Vaidman, Shakhida T. Nurmakhametova, Anatoly S. Miroshnichenko, Serik A. Khokhlov, Aldiyar T. Agishev, Azamat A. Khokhlov, Yeskendyr K. Ashimov and Berik S. Yermekbayev
Galaxies 2025, 13(5), 101; https://doi.org/10.3390/galaxies13050101 - 2 Sep 2025
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We present new spectroscopic orbits for the bright binaries Mizar B, 3 Pup, Gem, 2 Lac, and Aql. Our analysis is based on medium-resolution ( 12,000) échelle spectra obtained with the 0.81-m telescope and fiber-fed eShel spectrograph of the
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We present new spectroscopic orbits for the bright binaries Mizar B, 3 Pup, Gem, 2 Lac, and Aql. Our analysis is based on medium-resolution ( 12,000) échelle spectra obtained with the 0.81-m telescope and fiber-fed eShel spectrograph of the Three College Observatory (Greensboro, NC, USA) between 2015 and 2024. Orbital elements were inferred with an affine-invariant Markov-chain Monte-Carlo sampler; convergence was verified through the integrated autocorrelation time and the Gelman–Rubin statistic. Errors quote the 16th–84th-percentile credible intervals. Compared with previously published orbital solutions for the studied stars, our method improves the root-mean-square residuals by 25–50% and bring the 1 uncertainties on the radial velocity (RV) semi-amplitudes down to 0.02–0.15 km . These gains translate into markedly tighter mass functions and systemic RVs, providing a robust dynamical baseline for future interferometric and photometric studies. A complete Python analysis pipeline is openly available in a GitHub repository, ensuring full reproducibility. The results demonstrate that a Bayesian RV analysis with well-motivated priors and rigorous convergence checks yields orbital parameters that are both more precise and more reproducible than previous determinations, while offering fully transparent uncertainty budgets.
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Open AccessArticle
Energy of Photons in Expanding Spacetime: Comparing FLRW and Conformal Cosmology Metrics
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Václav Vavryčuk
Galaxies 2025, 13(5), 100; https://doi.org/10.3390/galaxies13050100 - 2 Sep 2025
Abstract
We investigate the behaviour of photons in Riemann spacetime, focusing on how their velocity and energy are affected by cosmic expansion. Specifically, we examine the differences in energy conservation depending on the cosmological model. Our findings indicate that photons exhibit fundamentally different behaviour
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We investigate the behaviour of photons in Riemann spacetime, focusing on how their velocity and energy are affected by cosmic expansion. Specifically, we examine the differences in energy conservation depending on the cosmological model. Our findings indicate that photons exhibit fundamentally different behaviour based on the chosen metric. In the standard CDM model, which relies on the Friedmann–Lemaître–Robertson–Walker (FLRW) metric, the energy conservation law for redshifted photons is violated. However, in a cosmological model based on the conformal cosmology (CC) metric, this law remains valid. The CC metric offers additional advantages, as it accurately reproduces the cosmological redshift, cosmic time dilation observed in Type Ia supernova light curves, and flat galaxy rotation curves without requiring the introduction of dark matter. These findings underscore the potential significance of the CC metric in cosmological applications.
Full article
Open AccessReview
The Astronomical Hub: A Unified Ecosystem for Modern Astronomical Research
by
Yerlan Aimuratov, Vitaliy Kim, Aleksander Serebryanskiy, Denis Yurin, Maxim Krugov, Chingiz Akniyazov, Saule Shomshekova, Maxim Makukov, Gaukhar Aimanova, Rashit Valiullin, Raushan Kokumbaeva, Alan Kazkenov and Chingis Omarov
Galaxies 2025, 13(5), 99; https://doi.org/10.3390/galaxies13050099 - 1 Sep 2025
Abstract
We present the conceptual framework of the Astronomical Hub (AstroHub), a unified platform combining various optical instruments at a single observatory. Its major approach lies in arranging conditions for research groups to install telescopes and equipment and participate in joint projects. AstroHub is
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We present the conceptual framework of the Astronomical Hub (AstroHub), a unified platform combining various optical instruments at a single observatory. Its major approach lies in arranging conditions for research groups to install telescopes and equipment and participate in joint projects. AstroHub is planned to integrate Virtual Observatory (VO) tools, FAIR data principles, and a telescope network to create a powerful and attractive ecosystem for both robust near-Earth object (NEO) monitoring and diverse deep space research. We provide an overview of the AstroHub development directions in the case study of the Assy-Turgen Observatory.
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(This article belongs to the Special Issue Circumstellar Matter in Hot Star Systems)
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RAD@home Citizen Science Discovery of Two Spiral Galaxies Where the 30–220 kpc Radio Lobes Are Possibly Shaped by Ram Pressure Stripping
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Prakash Apoorva, Ananda Hota, Pratik Dabhade, P. K. Navaneeth, Dhruv Nayak and Arundhati Purohit
Galaxies 2025, 13(5), 98; https://doi.org/10.3390/galaxies13050098 - 22 Aug 2025
Abstract
We report the RAD@home citizen science discovery of two rare spiral-host radio galaxies (NGC 3898 and WISEA J221656.57-132042434.1 or RAD-“Thumbs up” galaxy), both exhibiting asymmetric radio lobes extending over 30 to 220 kiloparsec scales. We present a multi-wavelength image analysis of these two
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We report the RAD@home citizen science discovery of two rare spiral-host radio galaxies (NGC 3898 and WISEA J221656.57-132042434.1 or RAD-“Thumbs up” galaxy), both exhibiting asymmetric radio lobes extending over 30 to 220 kiloparsec scales. We present a multi-wavelength image analysis of these two sources using radio, optical, and ultraviolet data. Both host galaxies are young, star-forming systems with asymmetric or distorted stellar disks. These disks show similarities to those in galaxies undergoing ram pressure stripping, and the radio morphologies resemble those of asymmetric or bent FR-II and wide-angle-tailed radio galaxies. We suggest that non-uniform gas density in the environment surrounding the ram pressure-stripped disks may contribute to the observed asymmetry in the size, shape, and brightness of bipolar radio lobes. Such environmental effects, when properly accounted for, could help explain many of the non-standard radio morphologies observed in Seyfert galaxies and in recently identified populations of galaxies with galaxy-scale radio jets, which are now being revealed through deep and sensitive radio surveys with uGMRT, MeerKAT, LOFAR, and, in the future, SKAO. These findings also underscore the potential of citizen science to complement professional research and data-driven approaches involving machine learning and artificial intelligence in the analysis of complex radio sources.
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(This article belongs to the Special Issue Recent Advances in Radio Astronomy)
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Open AccessArticle
Light Variability from UV to Near-Infrared in the Ap Star CU Vir Induced by Chemical Spots
by
Yury Pakhomov, Ilya Potravnov and Tatiana Ryabchikova
Galaxies 2025, 13(4), 97; https://doi.org/10.3390/galaxies13040097 - 21 Aug 2025
Cited by 1
Abstract
Multiwavelength modelling of the light variations in the chemically peculiar star CU Vir is presented. The modelling is based on the recent Doppler Imaging of CU Vir, which provides maps of the surface distribution of Si, Fe, He, and Cr. Intensity maps in
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Multiwavelength modelling of the light variations in the chemically peculiar star CU Vir is presented. The modelling is based on the recent Doppler Imaging of CU Vir, which provides maps of the surface distribution of Si, Fe, He, and Cr. Intensity maps in both individual photometric filters and in the wide wavelength range from UV to NIR were calculated, taking into account the individual chemical abundances on the stellar surface. Comparison with observations revealed good agreement of both the light curves and their amplitude along the spectrum. Additionally, we analysed changes in the photometric period of the CU Vir from 1955 to 2022, including TESS measurements. The data of the last decades clearly indicate a gradual decrease in this period. Measurements of the CU Vir period over the next two decades will be crucial for verifying or refuting the periodic nature of its variations.
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(This article belongs to the Special Issue Stellar Spectroscopy, Molecular Astronomy and Atomic Astronomy)
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Open AccessArticle
Distant Resolved Spectroscopic Binaries: Orbital Parallaxes Contradict Trigonometric Parallaxes
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Oleg Y. Malkov and Arseniy M. Sachkov
Galaxies 2025, 13(4), 96; https://doi.org/10.3390/galaxies13040096 - 21 Aug 2025
Abstract
Resolved spectroscopic binaries (RSB) are the only way (besides trigonometric parallax) to determine the dynamical, hypothesis-free distances to the stars of the galaxy. Analyzing the most comprehensive up-to-date data on RSB, we found that trigonometric parallaxes of all distant (
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Resolved spectroscopic binaries (RSB) are the only way (besides trigonometric parallax) to determine the dynamical, hypothesis-free distances to the stars of the galaxy. Analyzing the most comprehensive up-to-date data on RSB, we found that trigonometric parallaxes of all distant ( 0.5 kpc) binaries overestimate the distance by 10–50%. Such objects appear as single stars in Gaia and Hipparcos data, but their binarity can be detected/suspected by comparing trigonometric parallaxes in different data releases from these space missions.
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(This article belongs to the Special Issue Stellar Spectroscopy, Molecular Astronomy and Atomic Astronomy)
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Open AccessReview
Multi-TeV Gamma Rays from GRB 221009A: Challenges for Emission Mechanisms, EBL Opacity, and Fundamental Physics
by
Hassan Abdalla
Galaxies 2025, 13(4), 95; https://doi.org/10.3390/galaxies13040095 - 19 Aug 2025
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The detection of gamma-ray burst GRB 221009A has attracted significant attention due to its record brightness and first-ever detection of multi-TeV -rays from a GRB. Located at redshift , this event is relatively nearby by GRB standards yet remains
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The detection of gamma-ray burst GRB 221009A has attracted significant attention due to its record brightness and first-ever detection of multi-TeV -rays from a GRB. Located at redshift , this event is relatively nearby by GRB standards yet remains cosmologically distant, making the survival of multi-TeV photons surprising. The Large High Altitude Air Shower Observatory detected photons with energies up to ∼13 TeV during the early afterglow phase, challenging standard EBL models. We investigate whether several theoretical frameworks can explain this anomalous emission: reduced EBL opacity due to cosmic voids along the line of sight, novel emission mechanisms within the GRB environment, secondary -ray production through cosmic-ray cascades, and new physics scenarios involving Lorentz invariance violation or axion-like particles. Our analysis reveals areas of consensus regarding the exceptional nature of this event, while highlighting ongoing theoretical tensions about the dominant physical processes. We discuss the limitations of current models and identify specific observational signatures that future multi-wavelength and multi-messenger observations could provide to discriminate between competing explanations. The continued study of similar events with next-generation facilities will be crucial for resolving these theoretical challenges and advancing our understanding of extreme particle acceleration processes in astrophysical environments.
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Open AccessArticle
An Array of Bulk Acoustic Wave Sensors as a High-Frequency Antenna for Gravitational Waves
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Giorgia Albani, Matteo Borghesi, Lucia Canonica, Rodolfo Carobene, Federico De Guio, Marco Faverzani, Elena Ferri, Raffaele Gerosa, Alessio Ghezzi, Andrea Giachero, Claudio Gotti, Danilo Labranca, Leonardo Mariani, Angelo Nucciotti, Gianluigi Pessina, Davide Rozza and Tommaso Tabarelli de Fatis
Galaxies 2025, 13(4), 94; https://doi.org/10.3390/galaxies13040094 - 15 Aug 2025
Abstract
In their simplest form, bulk acoustic wave (BAW) devices consist of a piezoelectric crystal between two electrodes that transduce the material’s vibrations into electrical signals. They are adopted in frequency control and metrology, with well-established standards at frequencies of 5 MHz and above.
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In their simplest form, bulk acoustic wave (BAW) devices consist of a piezoelectric crystal between two electrodes that transduce the material’s vibrations into electrical signals. They are adopted in frequency control and metrology, with well-established standards at frequencies of 5 MHz and above. Their use as a resonant-mass strain antenna for high-frequency gravitational waves has been recently proposed (Goryachev and Tobar, 2014). The estimated power spectral density sensitivity at the resonant frequencies is of the order of . In this paper, after introducing the science opportunity and potential of gravitational wave detection with BAWs, we describe the two-stage BAUSCIA project plan to build a multimode antenna based on commercial BAWs, followed by an optimized array of custom BAWs. We show that commercially available BAWs already provide sensitivity comparable to current experiments around 10 MHz. Finally, we outline options for optimization of custom devices to improve sensitivity in an unexplored region, probe multiple frequencies between 0.1 and 10 MHz, and target specific signals, such as post-merger emission from neutron stars or emission from various dark matter candidates.
Full article
(This article belongs to the Special Issue Challenges for Third-Generation Gravitational Wave Detectors and Beyond)
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Open AccessArticle
Unveiling the Variability and Chemical Composition of AL Col
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Surath C. Ghosh, Santosh Joshi, Samrat Ghosh, Athul Dileep, Otto Trust, Mrinmoy Sarkar, Jaime Andrés Rosales Guzmán, Nicolás Esteban Castro-Toledo, Oleg Malkov, Harinder P. Singh, Kefeng Tan and Sarabjeet S. Bedi
Galaxies 2025, 13(4), 93; https://doi.org/10.3390/galaxies13040093 - 14 Aug 2025
Abstract
In this study, we present analysis of TESS photometry, spectral energy distribution (SED), high-resolution spectroscopy, and spot modeling of the CVn-type star AL Col (HD 46462). The primary objective is to determine its fundamental physical parameters and investigate its surface activity
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In this study, we present analysis of TESS photometry, spectral energy distribution (SED), high-resolution spectroscopy, and spot modeling of the CVn-type star AL Col (HD 46462). The primary objective is to determine its fundamental physical parameters and investigate its surface activity characteristics. Using TESS short-cadence (120 s) SAP flux, we identified a rotational frequency of 0.09655 ( d). Wavelet analysis reveals that while the amplitudes of the harmonic components vary over time, the strength of the primary rotational frequency remains stable. A SED analysis of multi-band photometric data yields an effective temperature ( ) of 11,750 K. High-resolution spectroscopic observations covering wavelengthrange 4500–7000 Å provide refined estimates of = 13,814 ± 400 K, = 4.09 ± 0.08 dex, and = 16 ± 1 km s−1. Abundance analysis shows solar-like composition of O ii, Mg ii, S ii, and Ca ii, while helium is under-abundant by 0.62 dex. Rare earth elements (REEs) exhibit over-abundances of up to 5.2 dex, classifying the star as an Ap/Bp-type star. AL Col has a radius of , with its H–R diagram position estimating a mass of and an age of Gyr, indicating that the star has slightly evolved from the main sequence. The TESS light curves were modeled using a three-evolving-spot configuration, suggesting the presence of differential rotation. This star is a promising candidate for future investigations of magnetic field diagnostics and the vertical stratification of chemical elements in its atmosphere.
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(This article belongs to the Special Issue Stellar Spectroscopy, Molecular Astronomy and Atomic Astronomy)
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Open AccessArticle
A List of the Most Prospective Eclipsing Cataclysmic Variables According to the TESS
by
Gulnur Subebekova, Makhabbat Adil, Serik Khokhlov, Aldiyar Agishev and Almansur Agishev
Galaxies 2025, 13(4), 92; https://doi.org/10.3390/galaxies13040092 - 14 Aug 2025
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Eclipsing cataclysmic variables (CVs) are key targets for determining binary system parameters through photometric modeling, yet many of them remain poorly characterized. In this work, we present a list (catalog) of 37 confirmed eclipsing CVs selected based on high-quality and publicly available TESS
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Eclipsing cataclysmic variables (CVs) are key targets for determining binary system parameters through photometric modeling, yet many of them remain poorly characterized. In this work, we present a list (catalog) of 37 confirmed eclipsing CVs selected based on high-quality and publicly available TESS photometric data. The sample includes both long-period systems (with orbital periods exceeding 4 h), such as Z Cam, U Gem, and nova-like variables, as well as a significant number of SW Sextantis stars. Selection criteria required the presence of clearly defined eclipses and sufficient signal-to-noise ratios for reliable analysis. The catalog provides a foundation for phase-folded light curve studies and future modeling efforts aimed at deriving key physical parameters such as component masses, radii, inclinations, and accretion geometries. Notably, several systems, such as V482 Cam, OZ Dra, ASASSN-14ix, and others, have no previously published physical parameters. Our list is accessible via a dedicated website, where each system will have a separate page, including data from TESS, AAVSO, and ZTF. This resource is intended to support detailed follow-up studies. It may encourage other research groups with observational and modeling expertise to contribute to the investigation of these promising but understudied systems.
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Open AccessArticle
Wind and Eruptive Mass Loss near the Eddington Limit
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Stan Owocki
Galaxies 2025, 13(4), 91; https://doi.org/10.3390/galaxies13040091 - 13 Aug 2025
Abstract
Luminous, hot, massive stars can lose mass both through quasi-steady winds driven by line-scattering of the star’s continuum luminosity, and through transient eruptions identified as Luminous Blue Variables (LBVs). This paper compares and contrasts the processes involved in steady vs. eruptive mass loss,
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Luminous, hot, massive stars can lose mass both through quasi-steady winds driven by line-scattering of the star’s continuum luminosity, and through transient eruptions identified as Luminous Blue Variables (LBVs). This paper compares and contrasts the processes involved in steady vs. eruptive mass loss, with an emphasis on their dependence on the star’s proximity to the classical Eddington limit. For winds, I examine the role of the iron opacity bump in initiating a quasi-continuum-driven outflow, which can induce atmospheric turbulence in O-stars, an envelope inflation cycle in LBVs, or enhanced wind mass loss in WR stars. In contrast, the giant eruptions of eruptive LBVs like Carinae require a sudden addition of energy to the stellar envelope, like that which can occur from stellar mergers. The positive net energy imparted to a substantial fraction (>10%) of the stellar mass leads to sudden ejection that closely follows an analytic exponential similarity solution. Moreover, the rapid rotation and enhanced luminosity of the post-merger star drive a super-Eddington wind. Due to equatorial gravity darkening, this wind is stronger over the poles, sculpting a bipolar structure in the ejected mass, consistent with observations of Carinae’s Homunculus nebula.
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(This article belongs to the Special Issue Circumstellar Matter in Hot Star Systems)
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Open AccessArticle
Long-Term Stability of Chemical Spots and Reasons for the Period Variations in Ap Star CU Vir
by
Ilya Potravnov, Tatiana Ryabchikova, Leonid Kitchatinov and Yuri Pakhomov
Galaxies 2025, 13(4), 90; https://doi.org/10.3390/galaxies13040090 - 12 Aug 2025
Cited by 1
Abstract
We present the results of Doppler Imaging of the Ap star CU Vir in the silicon lines over the 1985–2011 time span, as well as multi-element imaging in the 2009/2011 epoch. The surface distribution of silicon in CU Vir exhibits stability over the
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We present the results of Doppler Imaging of the Ap star CU Vir in the silicon lines over the 1985–2011 time span, as well as multi-element imaging in the 2009/2011 epoch. The surface distribution of silicon in CU Vir exhibits stability over the approximately 26 years studied: the number, shape, and mutual distribution of the overabundance spots have remained unchanged. The modelling of the light curve based on the surface elemental distribution obtained with DI did not reveal any significant changes in the shape of the light curve that could explain the photometric phase shift observed in CU Vir. Consequently, the phase shifts and changes in the photometric period of CU Vir are caused by the rigid longitudinal drift of the surface-abundance structures. We performed simulations of the Tayler instability of the background magnetic field of CU Vir, and discuss the possibility of explaining the period variations by the drift of surface instability modes.
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(This article belongs to the Special Issue Stellar Spectroscopy, Molecular Astronomy and Atomic Astronomy)
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Open AccessReview
Cosmic Magnification of High-Redshift Submillimeter Galaxies
by
Marcos M. Cueli, Joaquín González-Nuevo, Laura Bonavera and Andrea Lapi
Galaxies 2025, 13(4), 89; https://doi.org/10.3390/galaxies13040089 - 11 Aug 2025
Abstract
Weak lensing magnification probes the correlation between galaxies and the underlying matter field in a similar fashion to galaxy–galaxy lensing shear. Although it has long been sidelined in favor of the latter on the grounds of poorer performance in terms of statistical significance,
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Weak lensing magnification probes the correlation between galaxies and the underlying matter field in a similar fashion to galaxy–galaxy lensing shear. Although it has long been sidelined in favor of the latter on the grounds of poorer performance in terms of statistical significance, the provision of a large sample of high-redshift submillimeter galaxies by the Herschel observatory has transformed the landscape of cosmic magnification due to their optimal physical properties for magnification analyses. This review aims to summarize the core principles and unique advantages of the cosmic magnification of high-redshift submillimeter galaxies and discuss recent results applied to cosmological inference. The outlook and challenges of this observable are also outlined, with a focus on the ample scope for exploration and its potential to emerge as a competitive independent cosmological probe.
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(This article belongs to the Special Issue The Observation and Detection of Dusty Star-Forming Galaxies)
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