Solar and Stellar Astrophysics
Detecting Solar-Like Oscillations in the Highest Mass TESS Giants
Noah J. Downing, Madeline Howell, Marc H. Pinsonneault et al. (+4 more)
Red-
giant asteroseismology yields precise
stellar parameters, making it a powerful tool for studying
stellar structure and
evolution, as demonstrated by the Kepler mission. However, due to Kepler's limited field of view, it primarily sampled the more populous low-mass red
giants found outside of the
Galactic plane, leading to limited detections of red
giants above $\rm 3\ M_{\odot}$. Here we use the all-sky TESS data to isolate 227 intermediate-mass candidates from large catalogs with a pre-selection based on photometric and spectroscopic data. We optimize TESS light curves using a boutique light curve detrending method with custom apertures. Compared to the MIT Quick Look Pipeline, this yields a 12% average increase in the power-to-background ratio within the oscillation envelope, even in the heavily crowded
Galactic plane. We detect
solar-like oscillations in 98 targets, including 43 with $\rm M_* > 3\ M_{\odot}$. Our sample also includes 10
stars having masses greater than $5\ \rm{M}_{\odot}$, among the highest-mass
solar-like oscillators detected to date. From our detections, we find that the APOGEE DR19 spectroscopic $\log g$ is systematically larger by, on average, 0.23 dex compared to the seismic $\log g$. This offset is possibly due to the lack of intermediate-mass
giants observed by Kepler, which was used to calibrate the spectroscopic $\log g$ in the APOGEE pipeline. Extending the same pre-selection criteria to TESS targets with
Gaia XP spectroscopic parameters identifies up to 37,000 candidate intermediate-mass
solar-like oscillators for follow-up and population studies.
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All authors Noah J. Downing, Madeline Howell, Marc H. Pinsonneault, Rafael A. García, Dinil B. Palakkatharappil, Lina Borg, Savita Mathur
Cosmology and Nongalactic Astrophysics
A study of the large-scale formation in the environment of A3266: Infalling groups, filaments, and a premerger cold front
J. Dietl, A. Veronica, T.H. Reiprich et al. (+7 more)
Abell 3266 (A3266) is a dynamically active
galaxy cluster embedded in a dense environment of
galaxy groups and clusters at similar
redshift. Data from the Spektrum Roentgen Gamma (SRG)/eROSITA all-sky survey enable the study of faint X-ray emission in cluster outskirts. We investigate the previously unexplored outskirts of A3266 out to $3R_{100}$, characterize its nearest neighboring
galaxy group, and search for connecting filaments using X-ray emission and
galaxy number density. We performed X-ray imaging, surface brightness, and spectral analyses in selected regions and sectors. These were complemented by the distribution of member
galaxies from the NASA/IPAC Extragalactic Database NED and by comparison with the cosmological simulation Simulating the LOcal Web (SLOW). We detect an X-ray filament connecting A3266 to its nearest northwestern group over a 3D length of $L_{R_{200}\text{--}R_{200}} = {1.1}_{-0.1}^{+0.5},\mathrm{Mpc}$ with a significance of $3.6,\sigma$. The group exhibits cool-core properties and is embedded within the filament. The filament has a temperature of $T={1.2}_{-0.2}^{+0.3},\mathrm{keV}$,
metallicity $Z={0.07}_{-0.05}^{+0.09},Z{\odot}$, and, assuming a simple geometry, an electron number density of $n_{\rm e}={8}_{-2}^{+1}\times 10^{-5},\mathrm{cm}^{-3}$. Our findings reveal a coherent network of
galaxy groups around A3266, tracing its ongoing assembly along the large-scale structure. The filament is hotter and denser than expected for pristine warm-hot intergalactic medium, consistent with gas processed in the cluster environment and influenced by the infall of the northwestern group. Comparison with SLOW shows that the observed group distribution and filamentary connections are qualitatively consistent with an actively accreting cluster embedded in the
cosmic web.
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All authors J. Dietl, A. Veronica, T.H. Reiprich, F. Pacaud, Y. Zhao, J.S. Sanders, B. Seidel, M.C.H. Yeung, K. Dolag, E. Gatuzz
High Energy Astrophysical Phenomena
The First Measurement of Jet Collimation Profiles in an X-ray Binary: the Case of SS 433
Xi Yan, Lang Cui, Zsolt Paragi et al. (+1 more)
While significant progress has been achieved in active
galactic nuclei (AGN), jet collimation profiles in X-ray binaries (XRBs) have not been directly measured. Here we report the first measurement of jet collimation profiles in an XRB using very long baseline interferometry data from SS 433. The approaching jet exhibits a well-constrained quasi-
parabolic profile in the 1995 and 1998 data, whereas the prominent local oscillations present in the 2000 jet-width measurements preclude a robust characterization of the jet collimation profile. Nevertheless, the 2000 data suggest that the intrinsic jet opening angle decreases gradually from $\sim 20^\circ$ at 8$\times 10^{14}$ cm to $\sim 3^\circ$ at $9\times 10^{15}$ cm (deprojected), providing evidence for progressive jet collimation. The width and opening angle of the receding jet are also presented, although their interpretation is limited by the free–free absorption effect. In addition, we measure the frequency-dependent core positions at four bands and derive a core-shift relation. These results establish SS 433 as the first XRB in which jet collimation, opening-angle
evolution, and core-shift relation are constrained.
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All authors Xi Yan, Lang Cui, Zsolt Paragi, Sándor Frey
Earth and Planetary Astrophysics
Characterizing the oxidation state of rocky exoplanets with the Large Interferometer for Exoplanets (LIFE)
Lorenzo Cesario, Tim Lichtenberg, Michiel Min et al. (+5 more)
The oxidation state of rocky
exoplanets is expected to play a fundamental role in shaping the chemical composition of their secondary atmospheres by influencing the chemical composition of volcanically released gasses. Distinguishing planetary redox states through direct atmospheric characterization would offer insight into the formation and
evolution of secondary atmospheres on
exoplanets and inform the background chemistry of putative biosignatures. The Large Interferometer For
Exoplanets (LIFE) mission concept aims to employ a space-based mid-infrared nulling interferometer to characterize exoplanetary atmospheres. In this work, we assess LIFE's performance in distinguishing the redox states of rocky
exoplanets by direct spectroscopic measurements. We focus on the observability and spectral features of redox-sensitive molecules in secondary atmospheres of Earth-sized
exoplanets. We develop and apply a
retrieval framework based on the ARtful modeling Code for
exoplanet Science (ARCiS) and the LIFE mission simulator (LIFEsim) to simulate observations of Earth-sized
planets with atmospheres from a range of plausible mantle redox conditions. Our simulations show that LIFE in its baseline configuration can successfully constrain dominant atmospheric species (e.g. CO2, CH4 and NH3) with sufficient accuracy to distinguish redox states for
planets orbiting a Sun-like
star at 10 pc. Retrieved redox-sensitive molecules show clear trends across oxidation states, with CO2 dominating in oxidizing (with oxygen fugacity fO2 $\sim$ IW+2 to IW+6, where IW is the iron-w$\"u$stite buffer) environments and NH3 in reducing (fO2 $\sim$ IW-2 to IW-6) environments, and CH4 serving as a strong tracer among intermediate (fO2 $\sim$ IW+4 to IW-4) oxidation states.
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All authors Lorenzo Cesario, Tim Lichtenberg, Michiel Min, Lena Noack, Caroline Brachmann, Eleonora Alei, Sascha P. Quanz, LIFE Collaboration
High Energy Astrophysical Phenomena
Impact of Kaon Condensation on the Thermal Evolution of the CCO in HESS J1731–347 Supernova Remnant
D.G. Nanopoulos, P.S. Koliogiannis, V. Petousis et al. (+2 more)
Recent analyses of the central compact object in the HESS J1731–347
supernova remnant suggest an unusual combination of a low mass and small radius, while its thermal emission indicates a relatively high surface temperature at its estimated age. Reconciling these structural and thermal properties within a unified theoretical framework may provide important constraints on the equation of state and composition of dense matter. In this work, we investigate the thermal consequences of negatively charged kaon condensation, an exotic phase that softens the equation of state and facilitate the reproduction of the inferred bulk properties of HESS J1731–347. We find that the onset of kaon condensation strongly accelerates the thermal
evolution, leading to surface temperature substantially below the observationally inferred range. Within the adopted cooling framework, kaon condensation therefore cannot simultaneously account for the structural and thermal properties of HESS J1731–347.
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All authors D.G. Nanopoulos, P.S. Koliogiannis, V. Petousis, M. Veselsky, Ch.C. Moustakidis
Solar and Stellar Astrophysics
Magnetic Field Stratification in Active-Region Plage from Ca II K and Ca II 8542 Å Spectropolarimetry
Iñigo Juanikorena Berasategi, Ernest Alsina Ballester, Javier Trujillo Bueno et al. (+31 more)
We investigate the height variation of the line-of-sight (LOS)
magnetic field in
solar active-region (AR) plage from the upper photosphere to the upper chromosphere using co-spatial ultraviolet (UV) and infrared (IR) spectropolarimetric observations from the Sunrise III stratospheric balloon flight. The Ca II K and Ca II 8542 Å lines provide complementary chromospheric diagnostics, while nearby Fe I lines sample photospheric layers. The LOS
magnetic field is inferred from the intensity and circular polarization profiles, applying the weak field approximation for the Ca II lines and the center-of-
gravity method for the Fe I lines. The photospheric Fe I lines reveal strong, finely structured
magnetic fields of the order of a kG. In contrast, the chromospheric Ca II diagnostics yield systematically weaker fields, typically in the $\sim$ 100-400 G range, with a more diffuse spatial distribution.
Magnetic field maps inferred from the Ca II K line, formed higher in the chromosphere, are smoother and more extended than those derived from the Ca II 8542 Å line, which samples lower heights. We find that the magnetized area increases by a factor of $\sim$ 2 from the photosphere to the chromosphere. These results provide direct quantitative evidence that
magnetic fields in AR plage weaken and expand with height, evolving from compact kG photospheric concentrations into weaker and more spatially extended structures in the upper chromosphere.
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All authors Iñigo Juanikorena Berasategi, Ernest Alsina Ballester, Javier Trujillo Bueno, Francisco A. Iglesias, Yusuke Kawabata, Juan Sebastián Castellanos Durán, Masahito Kubo, Alex Feller, Yukio Katsukawa, Sami K. Solanki, Jose Carlos del Toro Iniesta, Andreas Lagg, Achim Gandorfer, Pietro Bernasconni, Thomas Kerkefeld, Tino L. Riethmüller, Yoshihiro Naito, Alberto Álvarez-Herrero, H. N. Smitha, David Orozco Suárez, Bianca Grauf, Michael Carpenter, Alexander Bell, Valentín Martínez Pillet, Francisco Javier Bailén, Julian Blanco Rodríguez, Edvarda Harnes, Johannes Hölken, Ryohtaroh T. Ishikawa, Takuma Matsumoto, Takayoshi Oba, Azaymi L. Siu-Tapia, Hanna Strecker, Dušan Vukadinović
Instrumentation and Methods for Astrophysics
Focal-Plane Diagnostics of Atmospheric and Dome-Induced Turbulence: Exploring techniques and applications
Begoña García-Lorenzo, Seifeldin Abouelella, Kabir Baig et al. (+8 more)
Atmospheric
turbulence remains the dominant source of image degradation in ground-based astronomy. Its impact depends not only on the integrated
turbulence strength but also on the wavefront spatial-coherence outer scale (\LO) and on
turbulence generated within the
telescope enclosure (dome seeing). While seeing, coherence time, and related parameters are routinely monitored at major observatories, measurements of \LO\ and dome-induced
turbulence remain sparse, limiting our ability to predict image quality and to construct accurate point-spread function (PSF) models. Building on methodology recently developed for seeing-limited integral-field spectroscopic (IFS) data, we present a series of complementary studies showing how spatial information encoded in standard observations can be used to diagnose both atmospheric and dome
turbulence. We investigate the feasibility of extending these techniques beyond IFS observations to other seeing-limited instruments through the analysis of wavelength-dependent spatial profiles. We also present the development of data-driven three-dimensional PSF models based on atmospheric statistics for the reconstruction of seeing-limited IFS observations. These results show that widely available seeing-limited scientific observations, both from archival data and routine observatory operations, can provide meaningful and operationally useful constraints on key
turbulence parameters and on the spectral behavior of dome seeing, complementing dedicated site-testing instrumentation. The resulting
turbulence diagnostics have direct applications to PSF modelling, image reconstruction, image-quality prediction, and the optimization of future ELT operations.
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All authors Begoña García-Lorenzo, Seifeldin Abouelella, Kabir Baig, Zenaida García Rodríguez, Kshitij Ghimire, Moisés Pulido Torres, Alejandro Trujillo Ramos, Jose A. Acosta-Pulido, Julio A. Castro-Almazán, Donaji Esparza-Arredondo, Antonio Eff-Darwich
Solar and Stellar Astrophysics
Back Reaction of the Untwisting Solar Corona Scars Sunspots
Chen Xing, Xin Cheng, Guillaume Aulanier et al. (+1 more)
The
evolution of
magnetic fields in the tenuous
solar corona is predominantly governed by the motions of the underlying dense photosphere. Despite, coronal
magnetic restructuring driven by
magnetic reconnection between interacting coronal fields can sometimes react backwards to change photospheric
magnetic fields. However, the mechanism of reactions remains undetermined. Here, we report the discovery of a back-reaction phenomenon: the untwisting of coronal loops that become twisted during reconnection in an eruption results in enhanced currents at the boundary of their footpoint away from the eruption, manifesting as the growth of a sunspot scar. It is revealed to arise from the Alfvenic reverse transfer of
magnetic twist from the corona to the lower atmosphere, thanks to joint space observations and a magnetohydrodynamics simulation. These findings provide a viable and quantitative interpretation for the majority of puzzling photospheric changes associated with coronal mass ejections and/or
flares and warn for unexpected
magnetic field evolutions in sunspots and starspots.
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All authors Chen Xing, Xin Cheng, Guillaume Aulanier, Mingde Ding
Earth and Planetary Astrophysics
Statistical Constraints on Albedo Structure in Asteroid Families from NEOWISE Measurements
Murat Kaplan
Interpreting asteroid family albedo distributions as compositional signatures requires distinguishing intrinsic structure from measurement artifacts, rarely quantified. We analyze 102 families using NEOWISE data with AKARI cross-validation and SDSS-based photometric checks, establishing detection limits for bimodality and quantifying selection bias in size-albedo correlations. We work primarily in logarithmic albedo space (log10 pV), which more accurately resolves the asymmetric dark/bright mixtures characteristic of compositionally mixed families. NEOWISE albedos are error-dominated: measurement uncertainties rival observed spreads (median sig_obs/sig_err ~ 0.99 in log space). AKARI cross-validation on 1,498 matched asteroids confirms NEOWISE measurements broadly (slope = 1.03, R^2 = 0.76, median |dpV| = 0.015), with a known spectral-type-dependent offset of +11%. Genuine bimodality meeting conservative criteria is found in 6 of 102 families (5.9%); the two most secure detections (Nysa-Polana, Juno) are recovered in both linear and logarithmic albedo, the other four only in log. Monte Carlo simulations show that a dark/bright bimodality at the characteristic separation (dmu ~ 0.64 dex) is recovered with high probability for the intrinsic scatter present in the families, so the low rate reflects genuine compositional homogeneity rather than limited sensitivity. Size-albedo correlations largely reflect magnitude-limited selection bias: only 2 of 63 families survive diameter-limited controls. These results indicate that many apparent compositional trends in family-level NEOWISE analyses are statistically indistinguishable from measurement scatter and selection effects within current uncertainties. Our detection limits and bias tests provide quantitative criteria for deciding when compositional inferences from NEOWISE family albedos are statistically defensible.
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Solar and Stellar Astrophysics
Cataclysmic variables from SRG/eROSITA: new systems from eRASS1
A.D. Schwope, J. Brink, D.A.H. Buckley et al. (+12 more)
(abridged) Aims. We aim to generate large samples of CVs selected from the SRG/eROSITA surveys to address fundamental questions about binary
evolution, the role of
magnetic fields in CV
evolution and their contribution to the
Galactic Ridge X-ray Emission (GRXE). Methods. We have trained a Random Forest (RF) classifier based on combined X-ray and optical properties to select CV candidates from the first eROSITA X-ray all-sky survey (eRASS1). Follow-up spectroscopy to securly identify the objects was performed on a subset of the selected candidates using
telescopes at the Northern and the Southern hemisphere. Newly identified CVs were further analyzed to determine their likely subtype with the help of dedicated follow-up photometry, spectroscopy and archival resources. Results. We have identified 156 CVs of almost all subtypes covering a wide range of distances (between 170 pc and several kpc), absolute magnitudes (G= 4.5-12) and X-ray luminosities (log LX (0.2-2.3 keV)= 29.6-33.3 erg/s). For most objects, the nature as a CV is reported here for the first time. For 40 objects periods were determined, which were regarded as their likely orbital periods. These range from 79.2 min, at the CV minimum period, to almost 22 hours. Seven objects were found to be eclipsing, a lower limit to the actual number due to the current lack of dedicated follow-up observations. A further five objects show cyclotron or Zeeman features, that allowed to determine their field strengths. A soft component was found in 14 CVs, all were regarded being
magnetic. The sample comprises X-ray luminous objects, excellent candidates for being new Intermediate Polars, that are thought to be main contributors to the GRXE. The new method of selecting CVs from eRASS1 was found to be superior to other methods described in the literature ...
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All authors A.D. Schwope, J. Brink, D.A.H. Buckley, V. A. Cúneo, S. Friedrich, S. Hernández-Díaz, K. Knauff, J. Kurpas, G. Lamer, S.B. Potter, K.G. Pradeep, M.R. Schreiber, B. Stelzer, J. R. Thorstensen, D. Tubin-Arenas
Astrophysics of Galaxies
Angular Momentum Evolution from Core to Disk Scales in the Early Phase of Star Formation: Constraints from HH 212, HH 211, and B335
Chin-Fei Lee
I investigate the angular momentum
evolution from core to disk scales in the early phase of
star formation using three protostellar systems: HH 212, HH 211, and B335. Observations show that the specific angular momentum follows a power-law dependence at core scales and transitions to an approximately constant value at smaller radii, indicating dynamical collapse in the inner envelope. I model this behavior using the inside-out collapse solution of Shu (1977) and its rotating extension, the Terebey-Shu-Cassen model, including modest
magnetic effects through a flattened, magnetized core. I find that the observed angular momentum profiles in all three sources are broadly consistent with an inside-out collapse scenario with approximate conservation of specific angular momentum in the collapsing region. The inferred collapse ages and mass infall rates yield total masses accreted onto the center that are broadly consistent with the central masses derived from kinematics, allowing for a fraction of the material to be ejected by jets and winds. The predicted midplane densities at typical radii, including the effect of
magnetic flattening, are also consistent with observational estimates. The three systems exhibit a similar pattern of angular momentum
evolution despite large differences in the magnitude of their specific angular momentum. In particular, the small disk in B335 can be naturally explained by its lower initial specific angular momentum, although alternative explanations, such as
magnetic braking or different initial conditions, cannot be excluded. These results suggest that inside-out collapse, with modest
magnetic modification, provides a plausible first-order description of angular momentum
evolution from core to disk scales in the early phase of
star formation.
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Solar and Stellar Astrophysics
The physical origin of the maximum stellar size
Gautham N. Sabhahit and Jorick S. Vink
One might expect the most massive
stars to also be the largest by size, yet they are not, and this has puzzled astronomers for decades. The Eddington limit sets an upper bound to
stellar mass through the balance between radiation pressure and
gravity, but a second empirical boundary on
stellar radius has equally far-reaching consequences for modern Astrophysics: it affects the black-hole masses and merger rates inferred by LIGO and Virgo, determines whether a
star remains a hot, compact ionising source or inflates into a cool supergiant, and thereby shapes how spectra of distant, unresolved
stellar populations are interpreted. Half a century ago, this radius limit was shown to trace a characteristic kinked shape in the Hertzsprung-Russell diagram known as the Humphreys-Davidson limit, yet a predictive, first-principle physical explanation has remained elusive. Here we show that this kink is the evolutionary manifestation of a transition from classical
stellar outflows to an Eddington-enhanced mass-loss regime implemented self consistently in evolutionary models. With our models accurately reproducing the empirical constraints on the radii of the most massive
stars, we now have a framework that can be incorporated into binary population synthesis, black-hole mass predictions, gravitational-wave event rates, and the interpretation of high-
redshift James Webb spectra.
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Solar and Stellar Astrophysics
Hydrodynamical mass-loss rates for Very Massive Stars II. New theoretical mass-loss predictions at solar metallicity (Z = 0.02)
Gautham N. Sabhahit, Jorick S. Vink and Andreas A. C. Sander
The evolutionary pathways and ultimate fates of very massive
stars are governed primarily by mass loss through radiatively driven winds. We present a new theoretical mass-loss prescription for (very) massive
stars, capturing the complex dependence on the Eddington parameter $\Gamma_e$, luminosity, temperature, and hydrogen abundance. We calculated an extensive grid of 178 hydrodynamically self-consistent wind-atmosphere models in non-local thermodynamic
equilibrium using the PoWR-HD code, predicting wind properties such as the mass-loss rate and terminal velocity self-consistently. The grid spans masses $M_*$ = 16-500 Msun, luminosities $\log(L_*/L_\odot) = 5.5-6.8$, inner boundary temperatures $T_* = 12-50$ kK, and hydrogen mass fractions X = 0.01-0.9, at a fixed
metallicity Z=0.02. We confirm the presence of a mass-loss kink in the $\dot{M}-\Gamma_e$ relation across the explored parameter space. The kink marks the transition from a shallow scaling ($\sim 2$) at low $\Gamma_\mathrm{e}$ for optically thin O-
star winds to a steeper scaling ($\sim 10$) for optically thick winds at high $\Gamma_e$. We derive comprehensive fitting relations capturing both the kink behaviour and two bistability jumps arising from iron ionisation changes, and provide auxiliary relations for implementation into
stellar evolutionary calculations. Our prescription correctly reproduces the model-independent transition mass-loss rate in the Arches Cluster, confirming the accuracy of our predicted rates at the O-to-WNh transition. Application of our recipe to the zero-age main sequence provides excellent agreement with recent empirical $\dot{M}-\Gamma_e$ relations obtained for a wide range of temperatures and Eddington parameters. We provide a physically motivated, continuous, and empirically anchored mass-loss recipe for (very) massive
stars, suitable for
stellar evolution calculations in the 20-500 Msun range.
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Solar and Stellar Astrophysics · Cross-listed from physics.plasm-ph
The Second Quadratic Invariant of Astrophysical Gyrokinetics
Benjamin D. G. Chandran, Alfred Mallet and Romain Meyrand
We show that gyrokinetics in a spatially uniform
equilibrium (or `astrophysical gyrokinetics') possesses a previously unknown quadratic invariant, which we call the gyrokinetic helicity. We derive the limiting forms of the gyrokinetic helicity in five subsidiary expansions of astrophysical gyrokinetics: the isothermal electron fluid (ITEF) approximation, kinetic reduced magnetohydrodynamics (KRMHD), electron reduced magnetohydrodynamics (ERMHD), finite-Larmor-radius magnetohydrodynamics (FLR-MHD), and the kinetic reduced electron heating model~(KREHM). We subdivide the real part of the gyrokinetic helicity into `magnetofluid' and `phase-space' components, which are separately conserved in KRMHD, ERMHD, and FLR-MHD (in which there is no phase-space helicity). The magnetofluid helicity is equivalent to the Alfvénic part of the cross helicity in KRMHD, the
magnetic helicity in~ERMHD, and the generalized helicity in FLR-MHD and~KREHM. We derive an analytic expression for the rate at which magnetofluid helicity is converted into phase-space helicity at length scales comparable to the
proton gyroradius in the ITEF approximation. We also explain how this conversion circumvents the helicity barrier and enhances turbulent heating in coronal holes and the near-Sun
solar wind.
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High Energy Astrophysical Phenomena
Comparative Periodogram Analysis of 22 Years of Super-Kamiokande Solar $^{8}\mathrm{B}$ Neutrino Data: Classical, Phase-Based, and Information Theoretic Methods
Liangliang Ren, Ze-Lin Zhang, Bing Xu et al. (+4 more)
Solar $^8\mathrm{B}$
neutrinos offer a unique probe of
solar interior dynamics and
neutrino electromagnetic properties. We present a systematic, multi-method periodogram analysis of the 22-year Super-Kamiokande
solar neutrino dataset (1996–2018), comparing nine
algorithms. Through hierarchical temporal
segmentation, we disentangle astrophysical signals from detector systematics. The Generalized Lomb-Scargle (GLS) method provides the most statistically robust detections by correctly handling heteroscedastic uncertainties, whereas classical Lomb-Scargle systematically underestimates significance. The Lafler–Kinman method generally fails, whereas independent
algorithms like MHAOV and PDM1 recover consistent periodicities, providing vital cross-validation. In pre-2001 and SK-I data, seven
algorithms provide weak evidence ($\ln B > 0$) for a $\sim 38.8$ d periodicity. However, this signal is entirely absent in the highest-statistics SK-IV modified flux data, where the Bayes factor decisively favors the null model ($\ln B \ll -5$), indicating it is a transient feature of the early low-statistics era. Conversely, a $\sim 24.3$ d signal in post-2001 raw flux is decisively rejected by the
Bayesian framework and vanishes in modified flux, confirming its seasonal systematic origin. Furthermore, no evidence is found for an $\sim 11$-year
solar cycle modulation, yielding a stringent amplitude upper limit of $<0.2\%$ of the mean flux. By highlighting the stark contrast between frequentist significance and
Bayesian model selection ($\ln B$) in low signal-to-noise regimes, we establish a rigorous, multi-metric best-practice framework for periodicity searches. This work provides a direct methodological blueprint for next-generation observatories like Hyper-Kamiokande and JUNO.
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All authors Liangliang Ren, Ze-Lin Zhang, Bing Xu, Tian-Cheng Huang, Ran Wang, Jia-Xin Dong, Yan-Ping Wang
Astrophysics of Galaxies
A search for HI absorption in distant star-forming galaxies with ASKAP-FLASH - II. Direct observations and stacking of 21 cm line
Sophie L. Eden, Elaine M. Sadler, Kevin A. Pimbblet et al. (+5 more)
We present results of a search for associated and intervening HI 21 cm absorption in
star-forming
galaxies and a control sample of
radio galaxies at 0.4 < $z$ < 1.0, using ASKAP's FLASH HI 21 cm absorption survey. We report the detection of a new HI 21 cm absorption line in
radio galaxy NVSS J214954-004657 at $z_{\mathrm{HI}}$ = 0.863. Additionally, we present results of HI 21 cm stacking for associated and intervening
star-forming and
radio galaxy catalogues. For the first time at these
redshifts, we report tentative detections of stacked HI 21 cm absorption for associated
galaxies when stacked in order of descending
radio source brightness, and show that these tentative detections become buried as optical depth increases as progressively weaker sources are co-added into the stack. No stacked signal is detected when co-adding intervening
galaxy spectra. We speculate that the ability to detect a stacked HI 21 cm detection is dependent on the background source optical depth limits, as well as source covering factors. Covering factor has a greater impact when stacking intervening systems, and can be considered to effectively weaken the observed flux density of a
radio source. We find no significant difference in detection rate for associated HI 21 cm absorption in
star-forming
galaxies versus the general
radio-source population at the same
redshift. Although detection rates are low, from a meta-analysis of HI 21 cm surveys we find that 1 detection is expected given the survey parameters.
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All authors Sophie L. Eden, Elaine M. Sadler, Kevin A. Pimbblet, Stephen J. Curran, Julia Healy, Filippo M. Maccagni, Elizabeth K. Mahony, Hyein Yoon
Astrophysics of Galaxies
Invariant manifolds in barred galaxy simulations. III. Self-regulated weakening of strong spiral arms
T. Soler-Terricabras, S. Roca-Fàbrega and M. Romero-Gómez
We investigated the origin of the weakening of strong spiral arms in barred
galaxies, seeking the physical mechanism responsible for the decline in the fraction of
manifold-trapped particles over time. We reconstructed the gravitational potential of a fully self-consistent N-body simulation of a barred
galaxy using AGAMA, computed the Lagrangian points, and quantified how their spiral-induced angular displacement affects the geometry of the invariant
manifolds and the associated orbital flows. We find that sufficiently strong, self-gravitating spiral arms significantly reshape the gravitational potential of a barred
galaxy, displacing the
equilibrium points up to 20-50{\deg} from the bar major axis, where they are expected to lie in the standard invariant-
manifold framework. This shift alters the configuration of the
manifold branches and disrupts the coherent
stellar flows that sustain the spiral structure. As the spiral weakens, the
equilibrium points gradually return to their standard configuration, restoring the conditions for
manifold-driven spiral arm formation on a timescale of ~200 Gyr. We show for the first time that invariant
manifolds and the spiral structures they generate are coupled through a self-regulating feedback mechanism, allowing the spiral pattern to recur over time. Our results therefore indicate that, although barred
galaxies may sustain spiral activity over long timescales, individual episodes of strong spiral arms are intrinsically transient.
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High Energy Astrophysical Phenomena
High-mass binary black hole mergers from detailed binary evolution models
Max M. Briel, Olcay B{\i}y{\i}kl{\i}, Tassos Fragos et al. (+10 more)
Gravitational-wave observations reveal a population of binary black hole (BBH) mergers with primary masses above ${\sim}40\,\mathrm{M}_\odot$, extending into and potentially beyond the pair-instability mass gap, with a possibly flat mass-ratio and broader \chi_\mathrm{eff} distribution. We investigate whether super-Eddington
accretion during stable mass transfer in isolated binary
evolution can produce BBH mergers consistent with these properties across primary BH mass, mass-ratio, and \chi_\mathrm{eff} distributions. Using POSYDON, we simulate BBH merger populations with primary BH masses above ${\sim}40\,\mathrm{M}_\odot$, under three BH
accretion efficiencies: Eddington-limited, GRRMHD-informed, and fully conservative. We additionally vary the natal kick strength, including strong kicks at high BH masses. We find that super-Eddington
accretion does not suppress BBH mergers in the high-mass regime. Fully-conservative
accretion leads to an increase of BBH mergers in POSYDON with a strong kick-independent peak at $\chi_\mathrm{eff}=0.6$ and a sharp mass-ratio peak at $q\sim0.5$, whereas observations favor $\chi_\mathrm{eff}=0.0$ and a flatter mass-ratio distribution. The GRRMHD-informed and Eddington-limited
accretion are compatible with the observed primary BH mass and mass ratio distribution, but require natal kicks to populate negative \chi_\mathrm{eff}. A joint analysis of the primary BH mass, mass ratio, and \chi_\mathrm{eff} distributions provides strong constraints on binary
evolution physics, and disfavor fully-conservative BH
accretion as the dominant formation mechanism for high-mass BBH mergers. The Eddington-limited and GRRMHD-informed prescriptions with modest kicks can explain part of the high-mass population, but an additional formation channel is still needed to account for the high fraction of negative \chi_\mathrm{eff} systems and high secondary BH
spins.
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All authors Max M. Briel, Olcay B{\i}y{\i}kl{\i}, Tassos Fragos, Anarya Ray, Zepei Xing, Monica Gallegos-Garcia, Abhishek Chattaraj, Jeff J. Andrews, Michael Zevin, Vicky Kalogera, Seth Gossage, Philipp M. Srivastava, Elizabeth Teng
Solar and Stellar Astrophysics
SRG/eROSITA X-ray selected cataclysmic variable candidates observed in SDSS-V DR20
J. Brink, A.D. Schwope, K.G. Pradeep et al. (+35 more)
We report on the spectroscopic observations obtained during SDSS-V DR20 of accreting compact binaries (ACB), specifically the cataclysmic variables (CVs), that were identified as likely compact binary candidates from the SRG (Spectrum Roentgen Gamma) eROSITA eRASS1 and eRASS:3 observations. Our primary aim is to obtain a complete inventory of all CVs that were detected in eRASS1 and eRASS:3, with the goal to help better understand close-binary
evolution, the population density, and demographics of these systems in the
Galaxy. Previous population studies had their respective limitations, with volume-limited samples suffering from low-number statistics, while magnitude-limited observations were biased to only the brighter systems. All CVs are X-ray emitters, eROSITA, therefore, presents a unique opportunity to identify CVs based on their X-ray emission. Given eROSITA's sensitivity, we expect to find most X-ray active CVs within 500 pc, and
magnetic CVs to several kpc. Using X-ray data from the eROSITA together with optical data from
Gaia, three different approaches were explored to identify the
Gaia optical counterpart to the eROSITA X-ray source of the likely ACB. From this, unique candidates were identified and were submitted in three different cartons to SDSS-V for optical spectroscopic observations as part of the Milky Way Mapper survey. From our submitted candidates, we found 538 likely CVs. We also identified CVs that were observed in other eROSITA based cartons, in which we identified an additional 49 systems that are likely CVs and which were not in our selection. We therefore identified 587 systems as CVs from the eROSITA based SDSS-V observations. We also attempted to sub classify the CVs as
dwarf-novae, novalikes, or
magnetic systems based on the eROSITA X-ray data, the emission line properties in the optical SDSS-V spectra, and other data in the public domain, if available.
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All authors J. Brink, A.D. Schwope, K.G. Pradeep, T. Dwelly, S.F. Anderson, C. Andonie, S. Aviram, C. Aydar, W.N. Brandt, J. Buchner, S. Demasi, M. Eracleous, S. Friedrich, B.T. Gänsicke, F. Haberl, P.B. Hall, J.J. Hermes, S. Hernández-Díaz, D. Homan, K. Inight, T. Kupfer, J. Kurpas, C. Maitra, A. Merlon, D. Muñoz-Giraldo, M.K.M. Prescott, A.L. Rankine, A.C. Rodriguez, W. Roster, S. Saeedi, M. Salvato, D.P. Schneider, M.R. Schreiber, B. Stelzer, K. Szekerczes, G. Tovmasian, B. Trakhtenbrot, Q. Wu
Solar and Stellar Astrophysics
The Study of Quasi-Periodic Pulsations in Solar and Stellar Flares with SKA
Valery M. Nakariakov, Atul Mohan, Vishal Upendran et al. (+5 more)
An intensively studied phenomenon which is not described by the standard
flare model are quasi-periodic pulsations (QPP) of the flaring emission. As analysis of the QPP phenomenon intrinsically requires a combination of high time and spatial resolutions, especially in the
radio band, the unprecedented capabilities of SKA offer us a unique opportunity to reach a breakthrough progress in the observational study of QPP. The SKA-Mid-frequency band falls in a unique window where both coherent emissions from particle acceleration sites and incoherent gyrosynchrotron emissions from non-thermal particles in coronal loops can be studied. With an additional polarisation dimension and the capability to perform wideband spectroscopic imaging, the QPPs in gyrosynchrotron emission ($\ge 1$~GHz) and
plasma emission will help understand the local
magnetic field modulation due to active phenomena and the response seen in the particle acceleration observable below ~600~MHz. An incomplete list of specific science questions to be addressed with SKA includes (a) the role of QPP in the energy partition in
flares, (b) seismology of flaring sites by QPP of different classes, (c ) differences and similarities between QPP in
solar and
stellar flares, (d) advancing the standard
flare model, (e) the physics of repetitive
magnetic reconnection: spontaneous vs induced, (f) ML techniques in the detection, classification and analysis of QPP, (g) QPP in weak
flares. The latter topic could be especially advanced with SKA which will allow for high-cadence high fidelity
radio imaging of weak energy release events.
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All authors Valery M. Nakariakov, Atul Mohan, Vishal Upendran, Teresa Monsue, Hamish A.S. Reid, Dmitrii Y. Kolotkov, Sergey A. Belov, Kyung-Suk Cho
Instrumentation and Methods for Astrophysics
DM/WFS mis-registration tracking: Implementation and on-sky validation of SPRINT at LBT
Ben Buky, Cédric Taïssir Héritier, Fabio Rossi et al. (+7 more)
The advent of
telescopes with an integrated deformable mirror (DM) presents new challenges for adaptive optics (AO) systems. The
alignment between the DM and wavefront sensor (WFS) is expected to regularly evolve during operations due to their large separation. Without tracking and correction, these mis-registrations between the DM and WFS lead to loop instability, preventing diffraction limited performance from being realised. SPRINT\cite{heritier2021} provides an approach to track these mis-registrations during observations. Rotation, shift, and magnification mis-registrations can all be recovered. The Large Binocular
Telescope (LBT) currently lacks an operational solution for tracking these mis-registrations, while SPRINT has been selected as the baseline approach for several instruments on the forthcoming Extremely Large
Telescope (ELT). We report on the implementation of SPRINT into the LBT real time computer and present experimental results from both daytime and on-sky testing to validate the method.
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All authors Ben Buky, Cédric Taïssir Héritier, Fabio Rossi, Juan Carlos Guerra, Charlotte Z. Bond, Noah Schwartz, Guido Agapito, Enrico Pinna, Sam Ragland, Jean-François Sauvage
Astrophysics of Galaxies
The eROSITA X-ray luminosity function of active galactic nuclei
W. Roster, J. Buchner, M. Salvato et al. (+23 more)
The X-ray luminosity function (XLF) of active
galactic nuclei (AGN) provides an observational probe of the growth of supermassive black holes (SMBHs) across
cosmic time. With its large survey grasp, Spectrum Roentgen Gamma (SRG)/eROSITA samples the luminosity–
redshift plane with a depth–area balance complementary to pencil-beam surveys, providing the volume needed to detect rare luminous AGN, previously limited by small-number statistics. We measure the soft XLF, leveraging an eROSITA sample spanning approximately eight orders of magnitude in luminosity out to $z\simeq6$. This enables us to study luminosity-dependent
evolution with improved constraints, and to infer both the SMBH
accretion history and optical/UV missed AGN population. We introduce a new
redshift-dependent smoothly broken power-law parameterisation in which all XLF model parameters are allowed to evolve continuously with
redshift. We find lower space densities for moderately and very luminous AGN at low
redshift, while the abundance is higher than previously found at the highest
redshifts. Comparisons to optical/UV
quasar LFs converted to rest-frame $2\!-\!10\,\mathrm{keV}$ show that the UV-missed fraction decreases with luminosity, and, in the most luminous bin, increases with
redshift. Integrating the XLF yields a black-hole
accretion-rate density peaking at $z \simeq 1.5$, with the corresponding cumulative black-hole mass density indicating $\sim80^{+11}_{-23}\%$ obscured growth relative to locally-inferred BH mass estimates derived from scaling relations and missed by the soft X-ray selection of our sample. With this work, we release the eROSITA DR2 AGN catalogue, including counterparts and their
redshift information. We then discuss how these results can inform future spectroscopic, photometric, and X-ray survey strategies aimed at improving AGN demographic constraints.
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All authors W. Roster, J. Buchner, M. Salvato, R. Shirley, A. Merloni, T. Dwelly, J. Aird, A. Georgakakis, P. Boorman, M. Brusa, W. N. Brandt, B. Trakhtenbrot, B. Laloux, P. Baldini, C. Andonie, C. Aydar, C. Ricci, S. F. Anderson, P. Chakraborty, R. J. Assef, D. P. Schneider, E. Kyritsis, M. Kluge, E. Bulbul, K. Nandra, J. Weller
High Energy Astrophysical Phenomena · Cross-listed from hep-th
Non-conformal obstructions to bubble expansion
David Mateos, Mikel Sanchez-Garitaonandia and Pedro Tarancón-Álvarez
We investigate the hydrodynamics of expanding bubbles in first-order phase transitions with non-conformal thermodynamics. We analyze a broad class of equations of state interpolating between bag-model descriptions, commonly used for electroweak transitions, and QCD-like theories. As a concrete
benchmark, we determine the bubble solutions for pure SU(3) Yang-Mills theory. We uncover a new set of hydrodynamic obstructions to bubble expansion. These obstructions arise both at the bubble wall and along the fluid flow, and can partially or completely eliminate otherwise allowed solutions. We also identify a new class of solutions, which we dub "shocked detonations", consisting of ordinary detonations with an additional shock inserted in the rarefaction wave. As a consequence of these obstructions, the space of admissible bubble wall velocities is significantly constrained, with gaps appearing between different expansion regimes. For example, for QCD-like theories, all detonation solutions, including shocked detonations, are excluded. We show that these effects can strongly impact the kinetic energy budget of the fluid and, therefore, the resulting gravitational-wave signal, potentially suppressing the most efficient configurations. Our results highlight the importance of non-conformal dynamics for accurately modeling phase transitions and the resulting gravitational-wave spectrum. The code used to construct the bubble solutions is publicly available. For completeness, we also show how the interpolation between the bag-model and QCD-like limits can be realized holographically by varying the backreaction of matter fields on the geometry.
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High Energy Astrophysical Phenomena
Thermal Breaking of the I-Love Universality for Hot White Dwarfs
Jinyi Lv, Jing-Yi Wu, Hongji Chen et al. (+3 more)
The universal I-Love-Q relations for compact
stars have significant applications in gravitational-wave astronomy, but thermal effects can break these relations in low-mass white
dwarfs. In this work, we employ the
stellar evolution code MESA to construct realistic models of $0.15 \, M_{\odot}$ helium-core and $0.6 \, M_{\odot}$ carbon-oxygen core white
dwarfs at various temperatures. By utilizing the Clairaut-Radau equation, we quantitatively extract the radial variation of the eccentricity of internal isodensity surfaces. Our numerical results demonstrate that higher central temperatures amplify the eccentricity variation, causing the I-Love relations to deviate from the zero-temperature Chandrasekhar model, whereas subsequent cooling restores them. This confirms that the temperature-induced violation of the universal relations is fundamentally driven by the loss of self-similarity in isodensity surfaces, providing key insights into the applicability conditions of I-Love-Q relations in compact objects.
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All authors Jinyi Lv, Jing-Yi Wu, Hongji Chen, Kexin Jia, Weihan Sun, Kilar Zhang
Earth and Planetary Astrophysics · Cross-listed from physics.space-ph
Ranking the drivers of the Venusian bow shock and ion composition boundary locations
Philippe Garnier, Moa Persson, Sofia Bergman et al. (+1 more)
The Venusian interaction with the
solar wind leads to the formation of an induced magnetosphere structured by
plasma boundaries. Their dynamics is complex, due to the combined influence of external (
solar photons,
solar wind
plasma and interplanetary
magnetic field (IMF)) and internal (ionized atmosphere) drivers. Studying these drivers helps understanding the transfer of energy and momentum throughout the Venusian system, and has thus implications for the erosion of the atmosphere through its coupling with the
solar wind. We here analyze and rank the influence of the main drivers of the Venusian bow shock and ion composition boundary locations. We revisit the results by Signoles et al. (2023) based on Venus Express measurements by combining several methods such as the Akaike Information Criterion, Least Absolute Shrinkage Selection Operator regression, and partial correlations. These methods allow to investigate cross correlations that appear and can bias the interpretation, and allow to rank drivers with robust approaches. The bow shock appears primarily driven by the IMF intensity or Mach number, the IMF $\theta_{bn}$ angle separating quasi-perpendicular vs quasi-parallel shocks, and then the
solar extreme ultraviolet fluxes and
solar wind dynamic pressure (with little influence of the convective electric field induced asymmetries). The Ion Composition Boundary is primarily driven by extreme ultraviolet fluxes, with a more reduced influence of several
solar wind parameters and IMF induced
magnetic pileup asymmetries. We also compare the behaviors of both boundaries and then compare the bow shock driver rankings at Mars and Venus. Finally we propose an analysis of the drivers of the extreme bow shock and ion composition boundary excursions.
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All authors Philippe Garnier, Moa Persson, Sofia Bergman, Yoshifumi Futaana
Astrophysics of Galaxies
Revealing the Physical Driver of the Baldwin Effect: Gas Density in the Broad-Line Region
Wen-Qiang Liang, Zhi-Fu Chen, Rui-Jing Lu et al. (+8 more)
The Baldwin effect — the inverse correlation between the equivalent width of emission lines and the continuum luminosity in active
galactic nuclei (AGNs) — has been known for nearly five decades, yet its physical origin remains poorly understood. Using a sample of 41,159
radio quasars constructed from the Sloan Digital Sky Survey and the Low-Frequency Array Two-metre Sky Survey, we investigate the origin and underlying physics of the Baldwin effect of MgII broad emission lines in both
radio-quiet (RQ) and
radio-loud (RL)
quasars. We find that the slope $\beta$ of the Baldwin effect is positively correlated with the Eddington ratio $\lambda_{\rm Edd}$ in both populations, and RL
quasars exhibit steeper $\beta$ than their RQ
quasars at fixed $\lambda_{\rm Edd}$. Photoionization simulations reveal that the $\beta$ is primarily governed by the gas density in the broad-line region (BLR): lower gas densities yield steeper slopes. This density-driven mechanism naturally connects the Baldwin effect to the broader AGN evolutionary context. Specifically, higher $\lambda_{\rm Edd}$ drive stronger
accretion disk winds, leading to denser BLRs and shallower $\beta$. Our findings indicate that BLR gas density serves as the primary physical driver underlying the "global" Baldwin effect, offering a physically grounded framework for interpreting AGN
accretion states and their coupled
evolution with host
galaxies.
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All authors Wen-Qiang Liang, Zhi-Fu Chen, Rui-Jing Lu, Cheng-Feng Peng, Shao-Hua Zhang, Zhe-Geng Chen, Zhi-Qing Chen, Yi-Qi Chen, Dong-Li Jiang, Xi-Heng Shi, Zhi-Wen Wang
Solar and Stellar Astrophysics
Unveiling the period-bounce population of cataclysmic variables: Spectroscopic and time-domain follow-up of eROSITA-selected candidates
S. Hernández-Díaz, B. Stelzer, A. Schwope et al. (+9 more)
During their secular
evolution, cataclysmic variable
stars (CVs) evolve toward shorter orbital periods ($P_{\rm orb}$) until reaching a minimum near $P_{\rm orb}\sim80$ min, after which they evolve back toward longer periods. CVs that have evolved past this evolutionary turning point are known as period-bouncers (PBs). Despite predictions that 40-80% of all CVs should be PBs, only 3-25% of the observed CV population is composed of PBs, a discrepancy likely due to their intrinsic low luminosities. We aim to investigate the evolutionary status of 213 SRG/eROSITA-selected PB candidates. The sample also includes 19 previously confirmed PBs, which serve as
benchmarks for evaluating the candidates. We confirmed 24 new CVs through the identification of Balmer emission lines in optical spectra from the Sloan Digital Sky Survey V (SDSS-V) and of
dwarf-nova outbursts in archival photometric surveys. By fitting hydrogen-rich atmosphere models to the SDSS-V spectra, we estimated the effective temperature and secular mass
accretion rate of the WDs. We also measured the Balmer decrements, used as diagnostics of the physical conditions of the
accretion disc, to assess whether they are consistent with known PBs. In addition, we analysed archival light curves from the Transiting
Exoplanet Survey Satellite (TESS) to determine $P_{\rm orb}$ for a subset of systems, and compiled multi-wavelength photometry to construct and model spectral energy distributions (SEDs), from which we inferred approximate donor spectral types. Our analysis of the new CVs indicates that they are consistent with being PBs, potentially increasing the population of confirmed PBs by $\sim 50\%$. Our results suggest that a substantial fraction of the PB population may remain hidden in WD catalogues.
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All authors S. Hernández-Díaz, B. Stelzer, A. Schwope, D. Muñoz-Giraldo, M. R. Schreiber, J. Brink, K. G. Pradeep, B. T. Gänsicke, M. Eracleous, K. Szekerczes, S. F. Anderson, J. R. Brownstein
Solar and Stellar Astrophysics
The X-ray catalogue of FGK stars within 10 pc: The coronal temperature-brightness relation explained with the RTV scaling law
M. M. Bennedik, B. Stelzer, M. Caramazza et al. (+3 more)
A comprehensive measurement of
stellar X-ray emission has important implications for our understanding of
stellar dynamos,
exoplanet atmosphere loss, and evaporation of protoplanetary disks. We present a catalogue of X-ray detections of the FGK-type main-sequence
stars within 10 pc, which accounts for
stellar multiplicity and optical loading of the detectors. To build the X-ray catalogue, we analysed all observations from SRG (Spectrum Roentgen Gamma)/eROSITA and XMM-Newton for
stars in the FGK 10pc sample, and we cross-matched the sample with ROSAT catalogues. We fit thermal
plasma models to the X-ray spectra to derive X-ray fluxes and coronal temperatures. We investigate the relation between coronal temperature and X-ray surface flux and find the result to be consistent with the ranges covered by different types of
solar coronal
magnetic structures. The lower end of the temperature-brightness relation is defined by the Maunder minimum
star HD 166620 and three other
stars whose positions identify them as possible Maunder minimum candidates. We identify systematic differences between the temperature-brightness law derived from XMM-Newton and eROSITA data that we attribute to their different instrumental response functions. We study the impact of both short-term flaring and long-term activity cycles on the
evolution of coronal temperature along with X-ray brightness. With the exception of three
stars, a remarkably small scatter is observed in the temperature-brightness relation across the whole sample. A natural explanation of the empirical kT-FX relation is provided by the RTV scaling law defined for
solar magnetic loops. The small spread of the observed relation indicates a universal scaling between the length and the filling factor of coronal loops. The three observed outliers deviate from this invariance of the ratio of loop length to filling factor for an as of yet unknown reason.
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All authors M. M. Bennedik, B. Stelzer, M. Caramazza, S. Orlando, A. Binks, J. Robrade
Solar and Stellar Astrophysics
The Volans-Carina association An X-ray Bridge Between Younger and Older Stellar Populations
Daniela Muñoz-Giraldo, Beate Stelzer, Alex Binks et al. (+3 more)
Nearby young moving groups (NYMGs) provide
benchmarks for studying the
evolution of
magnetic activity and planetary environments at early ages. The Volans-Carina association (VCA), as a pre-main sequence association at a distance of ~90 pc, occupies a sparsely sampled region of parameter space between younger nearby associations and older distant open clusters. We have re-evaluated the membership probabilities of the VCA catalog presented in Gagne et al. (2018a) with BANYAN as well as updated kinematics from
Gaia DR3.
Stellar parameters were derived from multi-wavelength spectral energy distributions, with the obtained bolometric luminosity and effective temperature being used in combination with pre-main sequence evolutionary models to obtain an isochronal age of the association. We joined data from the SRG (Spectrum Roentgen Gamma)/eROSITA and ROSAT all-sky surveys with a dedicated XMM-Newton Large Programme to construct a comprehensive X-ray catalog. Our updated census of the VCA comprises 29 highly probable members, 30 candidate members, and four uncertain objects. Isochronal analysis of the association yields an age of 80+-20 Myr, consistent with previous estimates. We detect X-ray emission from 56 objects, reaching ~90% completeness, one of the most complete X-ray censuses achieved for a NYMG. Low-mass members and candidates (<0.6 Msolar) have X-ray to bolometric luminosity ratios around the canonical saturation limit (Lx/Lbol~10^-3). X-ray luminosity functions show the VCA to be consistent with the similarly aged Pleiades (in the F5 to M3 range) and significantly more active than the older Hyades (in the F5 to K4 range). The combination of an updated membership census and a nearly complete X-ray census establishes the VCA as a particularly robust calibration point for studies of the early
evolution of coronal X-ray activity.
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All authors Daniela Muñoz-Giraldo, Beate Stelzer, Alex Binks, Enza Magaudda, Stefanie Raetz, Christian Schneider
High Energy Astrophysical Phenomena
Tidal Disruption Events with the SKA
T. An, A.J. Goodwin, J.C.A. Miller-Jones et al. (+3 more)
Tidal disruption events (TDEs) and related
nuclear transients probe jet launching, disk formation and circularization, particle acceleration, and the circumnuclear medium (CNM). However, the small fraction of events launching relativistic jets, the weak or delayed
radio emission of many thermal TDEs, and the black-hole demographics of
galactic nuclei remain poorly understood. SKA, with microJy sensitivity, wide bandwidth, long baselines, rapid response, and commensal surveys across 50-350 MHz (SKA-Low) and 0.35-15.4 GHz (SKA-Mid), will transform this field. Its sensitivity, frequency coverage, and very long baseline interferometry (VLBI) capability will extend
radio calorimetry from a few well-studied nearby events to volume-limited samples of non-relativistic
outflows. The SKA will bring off-axis and mildly relativistic jets into routine reach, trace CNM density profiles through the
evolution of the low-frequency synchrotron turnover, and localize faint off-
nuclear transients with sub-arcsecond precision. These data will constrain jet incidence, energetics, geometry, and magnetization, map the CNM through shock interactions, test links to changing-look active
galactic nuclei (AGN) and high-energy
neutrinos, and identify off-
nuclear events associated with recoiling supermassive or intermediate-mass black holes. We discuss the benefits of commensal surveys, rapid triggering, and SKA-VLBI, and provide predictions based on the projected performance of AA* and AA4. SKA will shift TDE
radio studies from detailed case-by-case studies to population-scale inference, advancing studies of jet physics and black-hole demographics.
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All authors T. An, A.J. Goodwin, J.C.A. Miller-Jones, M. Pérez-Torres, L. Rhodes, X. Shu