Astrophysics of Galaxies
Measurements of the HI intensity mapping power spectrum at low redshifts with MIGHTEE data: comparison with detected HI galaxies
Junaid Townsend, Mario G. Santos, Suman Chatterjee et al. (+6 more)
Line intensity mapping provides a statistical approach to tracing the large-scale distribution of matter in the Universe. We apply the HI intensity mapping technique to interferometric data from the MeerKAT International GHz-Tiered Extragalactic Explorations (MIGHTEE) Survey, analysing 17.5 hours of a single pointing in the COSMOS field, using a 60 MHz sub-band in the frequency range 1332 - 1392 MHz ($0.02 \lesssim z \lesssim 0.07$). Using a delay-spectrum-based
estimator, we measure the HI power spectrum on sub-megaparsec scales and compare it directly to the power spectrum inferred from a catalogue of individually detected HI
galaxies in the same field. After mitigating low-level broadband contamination through conservative outlier flagging in the three-dimensional power spectrum, cross-correlation of time-split visibilities yields a statistically significant detection on scales $3 \lesssim k \lesssim 20 \, \mathrm{Mpc}^{-1}$ with a total signal-to-noise ratio of $\sim 13$. Over this range, the power spectra obtained from visibilities and detected
galaxies are consistent within uncertainties and have comparable amplitudes of order $10^{-2}$ - $10^{-1}$ $\mathrm{mK}^2 \mathrm{Mpc}^3$. End-to-end validation is performed by propagating detected
galaxies through the power spectrum
estimator via both direct intensity-field construction and simulated visibilities, demonstrating agreement up to $k \sim 20 \ \mathrm{Mpc}^{-1}$, beyond which measurements become noise-dominated. A statistically significant correlation is also observed between the data and the simulated visibilities from the detected HI
galaxies, which should be free of systematics. These results provide a self-consistent validation of interferometric HI intensity mapping at low
redshift and demonstrate agreement with
galaxy-based measurements within the same cosmological volume.
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All authors Junaid Townsend, Mario G. Santos, Suman Chatterjee, Zhaoting Chen, Sourabh Paul, Aishrila Mazumder, Laura Wolz, Matt J. Jarvis, Bradley S. Frank
Cosmology and Nongalactic Astrophysics
The LOFAR sub-arcsecond view of the high-redshift radio relic in PSZ2G091.83+26.11
G. Di Gennaro, R. Timmerman, M. Hoeft et al. (+14 more)
Enhanced inverse Compton (IC) losses at high
redshift steepen diffuse
radio spectra in
galaxy clusters, making low-frequency (~100 MHz) observations favorable. However, low-frequency studies often lack the resolution needed to locate particle acceleration sites or separate diffuse emission from
radio galaxies. In this paper, we unveil the properties of the
radio relic in the distant cluster PSZ2G091.83+26.11 (z=0.822) by resolving the acceleration site and inspecting the downstream region. Using the European LOFAR (ILT) at 145 MHz, we study a
radio relic at (sub-)arcsecond resolution for the first time below 1 GHz, complemented by arcsecond-resolution VLA data at higher frequencies. We confirm the diffuse emission is not a
radio galaxy. A spectral index gradient toward the cluster center matches previous 5” maps. High-resolution 0.4” and 1.9” images reveal emission ahead of the shock, connecting the relic to a
radio galaxy. 1.9” profiles across the downstream at 145 MHz and 3.0 GHz follow a log-normal
magnetic field distribution. The 145 MHz shock surface shows a sharp discontinuity at the same location of a change in electron density, Rotation Measure, and fractional polarization, likely tied to
magnetic field changes. Finally, we find hints of
redshift evolution of the
radio power versus cluster mass correlation. The impressive angular resolution achievable by the LOFAR long baselines is opening an unprecedented view of the low energetic
plasma in
galaxy clusters. This is extremely significant in the case of high-
redshift clusters, where
radio emission at low frequencies is less affected by energy losses but its detection is strongly limited by poor resolution.
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All authors G. Di Gennaro, R. Timmerman, M. Hoeft, F. de Gasperin, R. J. van Weeren, A. Botteon, M. Brüggen, J. M. G. H. J. de Jong, T. W. Shimwell, F. Sweijen, G. Brunetti, R. Cassano, E. De Rubeis, W. Forman, H. J. A. Röttgering, A. Simionescu, H. Ye
Cosmology and Nongalactic Astrophysics
Correlated residuals in Tully-Fisher and Fundamental Plane relations and their impact on peculiar velocity measurements
Tyann Dumerchat, Raul E. Angulo, Julian Bautista et al. (+3 more)
The Tully-Fisher (TF) and Fundamental Plane (FP) relations are widely used to infer extragalactic distances and peculiar velocities, enabling measurements of large-scale velocity statistics and cosmological parameters. Using the Millennium-TNG hydrodynamical simulation, we assess the accuracy of these methods in the presence of realistic
galaxy formation physics. We find that, while the 2-point statistics of velocities are reliably inferred on scales larger than $\sim10\,\hMpc$, significant systematic deviations arise on smaller scales. These deviations originate from spatially correlated residuals in the TF and FP relations, driven by correlations between
galaxy structural properties,
star-formation history, and the local environment. As a result, TF- and FP-inferred velocity fields exhibit spurious correlations with the
galaxy density field that cannot be explained by random scatter alone. We show that extending the TF and FP relations to include additional
galaxy properties – such as
star formation rate, gas mass, and
stellar mass – mitigate these environmental correlations, particularly for late-type
galaxies. Our results demonstrate that
galaxy formation physics induces significant systematics in peculiar velocity measurements on non-linear scales, and that neglecting these effects may bias cosmological analyses.
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All authors Tyann Dumerchat, Raul E. Angulo, Julian Bautista, Cesar Aguayo, Sownak Bose, Lars Hernquist
Instrumentation and Methods for Astrophysics
Phase-Induced Amplitude Apodization Complex Mask Coronagraph (PIAACMC) on-sky demonstration with MagAO-X
Elena Tonucci, Sebastiaan Haffert, Warren Foster et al. (+18 more)
Advancing the technological development of small inner working angle (IWA) coronagraphs is essential to enabling high-contrast imaging of temperate
exoplanets with future extremely large
telescopes. The PIAACMC has been shown to closely approach the theoretical limit for coronagraphic throughput but its performance has not been fully characterised on-sky. This study serves as the first on-sky characterisation of contrast and IWA performance of the PIAACMC and its first technological demonstration at sub-micron wavelengths. We designed and manufactured phase-shifting focal plane masks optimised for two cases, a narrowband 875 filter (875nm, 3% band) and a broadband z' filter (908nm, 14% band). We tested the coronagraphs both with an internal source and on-sky using MagAOX, the extreme adaptive optics instrument for the Magellan Clay 6.5 m
telescope at Las Campanas Observatory. We show good recovery of the off-axis light's PSF shape within 92% and 97% depending on the separation when aligning the inverse set of PIAA lenses. We demonstrate sub-lambda/D IWAs of about 0.74 lambda/D in 875 and 0.76 lambda/D in z'. We reach average raw contrasts within 1 and 5 lambda/D with the internal source of about 1.6e-3 in 875 and 1.3e-3 in z'. These are mainly limited by the focal plane mask manufacturing errors, jitter, and residual quasi-static speckles in MagAO-X. We also show on-sky average raw contrasts within 1 and 5 lambda/D of about 1.4e-2 in 875 and 7.8e-3 in z'. These are likely limited by wavefront control, low-order aberrations, and poor observing conditions. Future work will improve the design and manufacturing processes of the focal plane masks to improve robustness and reach deeper contrast, as well as integrate focal plane wavefront control for non-common path aberrations correction.
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All authors Elena Tonucci, Sebastiaan Haffert, Warren Foster, Jared Males, Olivier Guyon, Laird M. Close, Kyle van Gorkom, Alexander Hedglen, Parker Johnson, Maggie Kautz, Jay Kueny, Jialin Li, Joshua Liberman, Joseph Long, Jennifer Lumbres, Matthijs Mars, Eden McEwen, Avalon McLeod, Logan Pearce, Lauren Schatz, Katie Twitchell
Solar and Stellar Astrophysics
Characterising the magnetospheric accretion process of DF Tauri's primary
K. Pouilly and M. Audard
The
accretion process in young
stellar objects (YSOs) is fundamental to the formation of
stellar systems. This process governs the
star's mass assembly, the transfer of angular momentum, and the shaping of the protoplanetary disc, thereby influencing
planet formation. For classical T Tauri
stars (cTTSs), which are low-mass YSOs,
accretion is a well-understood process. Their strong, dipolar
magnetic field truncates the disc at a few
stellar radii. Material is then channelled along these
magnetic field lines, creating
accretion funnel flows that fall onto the
star's surface. However, this paradigm, known as magnetospheric
accretion, is limited to isolated
stars. The
accretion process in multiple systems has not yet been fully understood. This work is part of a series of studies designed to build a framework to understand the
accretion process in multiple
star systems. The specific goal here is to determine how the magnetospheric
accretion model can be used to describe DF Tau, a binary system where only the primary
star is accreting material. To investigate how
accretion occurs in a system where a single
star is orbited by a non-accreting
stellar companion, we used a time series of high-resolution spectropolarimetric observations from the ESPaDOnS instrument. This allowed us to study the
accretion-related emission line variability, the veiling, and the
magnetic field
topology of the primary
star in the system. Our research concludes that the primary
star of the DF Tau system undergoes typical magnetospheric
accretion. This process is driven by a strong dipolar
magnetic field, which funnels accreting material onto the
stellar surface, creating an
accretion shock. We also identified a significant difference in the
magnetic topology of the two
stars querying the influence of
accretion of the
evolution of the
magnetic field, or capture of the secondary
star.
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Earth and Planetary Astrophysics
Warm Debris Disk Candidates around Nearby FGK Stars from LAMOST DR12
Xing Luo and Qiong Liu
Warm debris disks around main-sequence
stars trace late-stage terrestrial
planet formation. Motivated by the need for systematic searches of such systems, we identify debris disk candidates around FGK
stars within 150 pc by combining a spectroscopically selected sample from LAMOST DR12 with
Gaia astrometry and multi-band infrared photometry. Infrared excesses are identified through SED fitting and validated using conservative, source-by-source checks. This approach yields a final sample of 12 debris disk candidates including ten new detections.
Stellar age research indicate that most of the host
stars are several billion years old. NEOWISE monitoring reveals no significant W1/W2 variability, consistent with a circumstellar origin of the infrared excess. while a search for co-moving companions using
Gaia DR3 reveals possible companions for only two candidates at very large projected separations ($\gtrsim 10^4$~au). Three candidates exhibit excess emission in both the W3 and W4 bands, allowing estimates of characteristic
dust properties. This work establishes a small yet reliable sample of debris disk candidates anchored in homogeneous LAMOST spectroscopy, providing a foundation for future studies of debris disk
evolution and
stellar activity.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-lat
Confinement transition to gravitational waves in the one-flavor $SU(4)$ Hyper Stealth Dark Matter theory
V. Ayyar, R. C. Brower, G. T. Fleming et al. (+11 more)
The thermodynamics of the $SU(4)$ gauge theory with a single
flavor of fundamental
quarks is analyzed on the
lattice with dynamical
fermion simulations, which is the low-energy sector of a realistic, strongly-interacting dark matter model – the Hyper Stealth Dark Matter. The gravitational wave spectrum from the first-order confinement transition in the early universe is further calculated, where the effect of the dark sea
quarks, which decrease the interface tension in the effective potential of the Polyakov loop, is shown numerically to lower the gravitational wave amplitude.
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All authors V. Ayyar, R. C. Brower, G. T. Fleming, J. Ingoldby, X. Y. Jin, N. Matsumoto, A. S. Meyer, E. T. Neil, J. C. Osborn, S. Park, C. T. Peterson, D. Schaich, P. Vranas, O. Witzel
High Energy Astrophysical Phenomena
Tight bounds on the Maxwell-Carroll-Field-Jackiw parameters using Fast Radio Bursts
Filipe S. Ribeiro, Pedro D. S. Silva, Rodolfo Casana et al. (+1 more)
We investigate the arrival time and the Faraday rotation of extragalactic electromagnetic signals from fast
radio bursts (FRBs) propagating through
chiral cosmic media within the framework of Maxwell-Carroll-Field-Jackiw (MCFJ) electrodynamics. By treating the interstellar medium as a cold, ionized
chiral plasma, we derive the time delay between two traveling signals, expressing it in terms of modified dispersion measures (DMs) containing
chiral contributions. The Faraday rotation angle is then written in terms of modified rotation measures (RMs). By combining the DMs and
redshift data from a set of FRBs, we obtain constraints on the
chiral parameter magnitude at the order of $10^{-26}$–$10^{-24}$ GeV. Using the Faraday rotation formulae and RM measurements, upper bounds as stringent as $10^{-43}$ GeV on the MCFJ parameters are also obtained.
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All authors Filipe S. Ribeiro, Pedro D. S. Silva, Rodolfo Casana, Manoel M. Ferreira Jr
Cosmology and Nongalactic Astrophysics
Cosmic voids as a probe of the nature of dark matter: simulations and galaxy survey forecasts
Alexander Spencer London, Keir K. Rogers, Alex Laguë et al. (+2 more)
Voids are parts of the
cosmic web least affected by non-linearities and baryonic feedback. We thus calculate the sensitivity of voids to the nature of dark matter (DM), using ultra-light
axions as a concrete model and the ongoing Dark Energy Spectroscopic Instrument (DESI) and Euclid
galaxy surveys as observational settings. We simulate
axion effects on voids using mass-peak patch simulations and find that: (i)
axions suppress the formation of lower-mass
halos leading to the merging of smaller (radius $< 25\,\mathrm{Mpc}/h$) voids into fewer larger (radius $> 25\,\mathrm{Mpc}/h$) voids; and (ii) voids in the presence of
axions are emptier of
halos, thereby suppressing the void-
halo correlation function. These effects strengthen as
axion particle mass $m_\mathrm{a}$ decreases. We forecast improvements in
axion constraints from the void size function (VSF; the void number density as function of their radius). A Euclid-like survey (effective volume of $73\,\mathrm{Gpc}^3$ with a prior on the other $\Lambda$CDM cosmological parameters from the Simons Observatory
cosmic microwave background experiment) can limit the
axion energy density (for $m_\mathrm{a} = 10^{-25}\,\mathrm{eV}$) to $< 4.6\%$ of the DM (at $95\%$ credibility), about two times stronger than current limits. Conversely, we show that a Universe with a dark sector consisting of
axions at the $10\%$ level, as motivated by the string axiverse, can be recovered with $\sim 2 \sigma$ preference. A DESI-like survey achieves comparable results.
Axion and $\Lambda$CDM parameters have different degeneracies given VSF and
galaxy power spectrum data, indicating future combined analyses will be most powerful in disentangling the DM nature. We anticipate our results will extend to other (e.g., warm or interacting) DM models.
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All authors Alexander Spencer London, Keir K. Rogers, Alex Laguë, Renée Hložek, Zara Zaman
High Energy Astrophysical Phenomena
Energy Deposition by Galactic Cosmic Rays and Implications for Ozone Chemistry
Luiz Augusto Stuani Pereira and Rita C. Anjos
We present a Monte Carlo study of
galactic cosmic-ray (GCR) energy deposition and its implications for stratospheric chemistry, performed with the Geant4 toolkit. Primary
nuclei (
protons, $\alpha$, CNO, and Si) were propagated through an atmosphere modeled from 0 to 120~g~cm$^{-2}$, considering both Polar ($R_{\mathrm{c}}=0.1$~GV) and Equatorial ($R_{\mathrm{c}}=15$~GV) geomagnetic cutoff conditions. The simulations resolve the variation of energy deposition with altitude for primary and secondary particles, revealing that $\sim$~96% of the stratospheric energy budget arises from cascade secondaries within the 15–35~km domain. By converting layer-resolved energy deposition into ion pair production rates, we quantify the resulting formation of odd nitrogen (NO$_{\rm x}$) and odd hydrogen (HO$_{\rm x}$) radicals, which catalyze the destruction of ozone. The modeled production rates peak between 18 and 22~km altitude, leading to an estimated fractional ozone decrease of order $10^{-3}$–$10^{-2}$ under average GCR fluxes, consistent with observed background modulation over the
solar cycle. These results establish a physically consistent link between
cosmic-ray induced energy deposition and ozone chemistry, providing a
benchmark framework for coupling high-energy particle transport to atmospheric photochemical models.
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Earth and Planetary Astrophysics · Cross-listed from physics.space-ph
Investigating potential benefits of future sub-L1 missions with STEREO-A
Eva Weiler, Emma E. Davies, Christian Möstl et al. (+4 more)
We present the first statistical study of geomagnetic storm
forecasting using in situ data from the STEREO-A spacecraft as a sub-L1 monitor. Between November 2022 and June 2024, STEREO-A crossed the Sun-Earth line, covering longitudinal and radial separations of +/-15{\deg} from the Sun-Earth line and 0.01-0.06 au from Earth. This passage provides a unique opportunity to assess future sub-L1 mission concepts by ESA, such as HENON and SHIELD. We identify 32 coronal mass ejections (CMEs) observed by both STEREO-A and L1 spacecraft. Eight of these 32 CME events are first detected at L1, indicating that radial spacecraft separations of up to ~0.05 au do not always yield lead time advantages. Furthermore, we find greater (smaller) gains in lead time when STEREO-A is east (west) of the Sun-Earth line. We develop a baseline methodology for the use of future sub-L1 in situ data to enable time-shifting and real-time modeling of the geomagnetic SYM-H index. This is run continuously over the entire time period, therefore modeling the geomagnetic response of all
solar wind structures. Our methodology is empirically motivated and should be considered a first approach in addressing the use of sub-L1 data. Following this methodology, 26 of 47 observed geomagnetic storms are correctly identified from STEREO-A data. Intense events (82%, SYM-H<-100 nT) are well detected, most of which are also associated with an identified CME event. Most SYM-H minima are predicted later (72%) and stronger (58%) than those observed due to biases introduced by our methodology.
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All authors Eva Weiler, Emma E. Davies, Christian Möstl, Noé Lugaz, Astrid Veronig, Rachel Bailey, Martin Reiss
Solar and Stellar Astrophysics
Eating planets makes you younger: The magnetic dynamo rejuvenation of GJ 504 by planetary engulfment
S. Bellotti, C. Pezzotti, G. Buldgen et al. (+3 more)
With the discovery of a few thousand
exoplanets, questions have been raised regarding
star-
planet interactions and whether the presence of a companion may affect
stellar properties. GJ 504 is an evolved (2 Gyr) Sun-like
star with a short rotation period (3.4 d) and an intense
magnetic activity, which is in stark contrast with what would be expected at such an evolutionary stage. One possible explanation is that a close-in, Jupiter-mass
planet was pushed starwards by the action of
stellar tides, inducing a
stellar spin-up and ultimately a rejuvenation of the
stellar magnetic dynamo. By characterising the large-scale
magnetic field and magnetised wind of GJ 504, we aim to provide additional observational constraints to test such scenario. We analysed spectropolarimetric observations of GJ 504 collected with ESPaDOnS. Using Zeeman-Doppler imaging, we found a large-scale, dipolar, non-axisymmetric
magnetic field with an average strength of 5.3 G, similar to that of evolved early-G type
stars. We fed the
magnetic field information into our 3D MHD simulation of the
stellar wind and space environment of GJ 504, from which we constrained the wind-driven angular momentum loss ($\rm \dot{J}$). We then compared $\rm \dot{J}$ to rotational evolutionary tracks of GJ 504 for two scenarios:
evolution with and without the engulfment of a close-in, Jupiter-mass companion. Between the two scenarios, only the
planet engulfment can explain the observational constraints obtained previously in the literature, such as the
stellar rotation and X-ray luminosity, and the $\rm \dot{J}$ we derived and rescaled to account for underestimated
magnetic field strength. Although there are many other
stars with similar masses and rotation periods whose rotation
evolution does not require
planet engulfment, we also identified HD 75332 as a candidate for
planet engulfment, suggesting that GJ 504 may not be an isolated case.
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All authors S. Bellotti, C. Pezzotti, G. Buldgen, A. A. Vidotto, D. Evensberget, E. Magaudda
Instrumentation and Methods for Astrophysics
Demonstrating Single Photon Counting with Kinetic Inductance Detectors from 3.8 to 25 $\mu$m
Wilbert G. Ras-Vinke, Kevin Kouwenhoven, Jochem J.A. Baselmans et al. (+4 more)
One of the primary objectives of modern astronomy is the atmospheric characterization of Earth-like
exoplanets at visible and infrared wavelengths. Achieving this goal requires extremely sensitive detectors capable of measuring faint signal of the
exoplanet at the single-
photon level while maintaining near-zero dark count rates. In the infrared, however, conventional semiconducting detector technologies struggle to meet these stringent requirements. In this work we demonstrate single-
photon counting with superconducting Microwave Kinetic Inductance Detectors at the wavelengths 3.8, 8.5, 18.5, and 25 $\mu$m and measure resolving powers ($E/\delta E$) of 9.9, 5.9, 3.2, and 3.3, respectively, with corresponding dark count rates of 4, 8, 34, and 48 mHz. Our membrane-based devices reach
phonon-loss limited performance at 3.8 $\mu$m, more than doubling the performance attainable with comparable solid-substrate devices. These results showcase the detector technology in the mid-infrared and the intricate measurement setup required for these sensitive detectors. We discuss how the detector design and measurement setup can be further optimized to increase the detector performance in the mid-infrared.
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All authors Wilbert G. Ras-Vinke, Kevin Kouwenhoven, Jochem J.A. Baselmans, Kenichi Karatsu, David J. Thoen, Vignesh Murugesan, Pieter J. de Visser
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
The Delta-isobar masquerade: intrahadronic phase transitions and their quark-mimicking signatures in neutron stars
Martin O. Canullan-Pascual, Germán Lugones, Ignacio F. Ranea-Sandoval et al. (+1 more)
We investigate the conditions under which $\Delta(1232)$ isobars trigger a first-order phase transition within purely hadronic
neutron-
star matter, using the SW4L relativistic mean-field parametrization. For scalar-vector coupling differences $0.15 \lesssim x_{\sigma\Delta} - x_{\omega\Delta} \lesssim 0.2$ and $x_{\sigma\Delta} \gtrsim 1.3$, the onset of $\Delta^-$ resonances produces a van der Waals-like instability driven by a self-amplifying feedback in the scalar
meson sector, in which the $\Delta^-$ particle fraction acts as the order parameter of a Landau-type transition. A Maxwell construction yields a sharp density discontinuity at
baryon densities $n_b \sim (1.3$-$2)\,n_0$, separating a $\Delta$-free outer core from a $\Delta$-rich inner core. The resulting
neutron-
star sequences satisfy all current multimessenger constraints: maximum masses $M_{\rm max} \approx 2.15$-$2.25\,M_\odot$, radii $R_{1.4} \approx 11$-$12$ km, and
tidal deformabilities $\Lambda_{1.4} \approx 190$-$480$, compatible with NICER observations and GW170817. We compute, for the first time for a $\Delta$-induced interface, the $\ell = 2$ composition $g$-mode eigenfrequencies, obtaining $\nu_g \sim 400$-$1100$ Hz with gravitational-wave damping times $\tau_g \sim 10^3$-$10^9$ s. These frequencies overlap quantitatively with those predicted for
hadron-
quark phase-transition interfaces, demonstrating that the mass-radius “knee”, reduced
tidal deformability, and $g$-mode spectrum conventionally regarded as signatures of
quark deconfinement can be reproduced by a purely intrahadronic mechanism. This extends the masquerade problem from static observables to the domain of gravitational-wave asteroseismology, implying that a future detection of a discontinuity $g$-mode alone would not suffice to identify
quark matter in
neutron-
star cores.
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All authors Martin O. Canullan-Pascual, Germán Lugones, Ignacio F. Ranea-Sandoval, Milva G. Orsaria
High Energy Astrophysical Phenomena
P.R. Brook, J.B. Gibson, M.A. McLaughlin et al. (+1 more)
Nulling is a phenomenon where the emission from a
pulsar becomes undetectable (or significantly weaker) for a relatively short period of time, followed by a return to a normal emission state. The timescale of nulling ranges from a few pulse periods to many hours or even days. The fraction of time a nulling
pulsar spends in a null state varies across the population of canonical
pulsars, from 0 to 95 per cent. The long-term behaviour of a
pulsar's nulling fraction, however, is currently unknown, as published values have typically been obtained through single observations. Here, we present the first long-term analysis of nulling behaviour in eight
pulsars observed in the Parkes Multibeam
Pulsar Survey over the course of eight to ten years. We also apply a new
Bayesian method for pulse-energy analysis, yielding posterior estimates of the nulling fraction per observation. In several cases, the nulling affects only specific components of the pulse profile, rather than the entirety of the emission. Our analysis reveals that, while most
pulsars show no significant trend in their nulling fraction over time, a subset exhibit some evidence for non-zero gradients in nulling fraction. In particular, PSRs J1048$-$3832, J1745$-$3040, and J1825$-$0935 show statistically significant trends over the span of the data. Studying the behaviour of nulling over years and decades is valuable as it can provide insights into the physical emission processes within
pulsars. Studying how nulling evolves also provides valuable insights into
pulsar evolution and the characterisation of the broader
pulsar population.
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All authors P.R. Brook, J.B. Gibson, M.A. McLaughlin, M.P. Surnis
High Energy Astrophysical Phenomena
Pulse-resolved Classification and Characteristics of Long-duration GRBs with Swift-BAT Data.II. Main Burst versus Extended Emission
Liang Li, Xiao Wang, Zhi-Li Cui et al. (+5 more)
Long gamma-ray bursts (GRBs) frequently exhibit complex
prompt emission structures with multiple temporally distinct episodes, such as a main emission (ME) phase followed by a weak extended emission (EE) tail. Whether these subcomponents from a common physical origin with similar classification properties, or instead represent fundamentally different emission mechanisms within a single event, remains an open question. Here, we present a systematic, pulse-resolved analysis of 22 Swift/BAT long-duration GRBs, each exhibiting a well-separated, bright ME ($G_1$) followed by a fainter EE ($G_2$) after a background-consistent quiescent gap. For each component, we independently measure standard classification diagnostics, including duration ($T_{90}$), spectral hardness ratio (HR), minimum variability timescale (MVT), and spectral lag. We then compare these properties between the ME and EE within individual bursts. We find that the EE is systematically softer (lower HR in 19 of 22 events), smoother (longer MVT in 17 of 22 events), and more diverse in spectral lag than the ME. However, both components still occupy the long-GRB track in the traditional duration-hardness and duration-MVT planes, indicating a common Type~II (collapsar) origin. These results suggest that the EE in long GRBs represents a physically distinct regime of the central engine, characterized by a lower luminosity, longer emission timescales, and evolved spectral properties, rather than a simple continuation of the main burst. This picture is consistent with late-time fallback
accretion onto a black hole or proto-magnetar
spin-down.
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All authors Liang Li, Xiao Wang, Zhi-Li Cui, Cheng-Long Xiao, Wen Li, Yu Wang, Zi-Gao Dai, Rong-Gen Cai
Astrophysics of Galaxies
Group Pre-processing in J1611+4026: Minor Rejuvenation of a Massive ETG fueled by Interaction-driven Gas Transfer
Yaosong Yu, Qihang Chen, Zizhao He et al. (+3 more)
Interactions within
galaxy groups are fundamental drivers of
galactic evolution, and establishing a direct observational link between the dynamical processes of satellite
galaxies and the rejuvenation of massive host
galaxies remains challenging. We present a multi-wavelength work of J1611+4026, a unique triple system characterised by a massive early-type host
galaxy, Component C and two gas-rich companions, Components A and B, which are currently undergoing a major merger in its near environment. Utilising deep optical imaging from DESI-LS and spectroscopic data from DESI and P200, we employ 2D morphological decomposition using GALIGHT alongside joint spectrophotometric synthesis modelling with BAGPIPES and CIGALE to deconstruct the structural properties and
star formation histories of the member
galaxies. Crucially, we identify an asymmetric
tidal tail extending $\sim$15.15 kpc from Component A, confirming the ongoing interaction between the companions. Although Component C appears quiescent in both morphology and spectroscopy, we reveal a subtle robust signal of “minor rejuvenation”, characterised by significant internal
dust extinction of $E(B-V) \sim 0.53$ and a UV excess. The reconstructed
star formation history indicates a recent ($\sim$100 Myr) starburst that contributes a negligible fraction to the total
stellar mass ($f_{\rm burst} < 0.1$ per cent). We propose that this activity is fueled by the
accretion of metal-enriched gas stripped from the interacting companions. These results strongly suggest group pre-processing, where interactions between satellite
galaxies drive low-level
star formation in the massive host through gas transfer, providing a quantitative
benchmark for interaction-driven
evolution in dense environments.
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All authors Yaosong Yu, Qihang Chen, Zizhao He, Limeng Deng, Liang Jing, Jianhui Lian
High Energy Astrophysical Phenomena
The MARTINI Platform (I): Se I-X atomic calculation and expansion opacity for early-stage kilonova spectral analysis
Matteo Bezmalinovich, Mattia Bulla, Gediminas Gaigalas et al. (+3 more)
Kilonovae represent key sites of r-process nucleosynthesis, making opacity estimation and spectral analysis crucial for constraining their composition. Since light r-process elements shape the early ($\sim$0.5-1.5$\mathrm{d}$) ejecta opacity, a detailed study of the selenium element with a focus on atomic data calculation, expansion opacity estimation and spectral analysis is presented. Se atomic data are calculated from Se I to Se X using the GRASP2018 code. A systematic analysis and evaluation of their precision is performed through detailed comparison with the NIST ASD, and other works available in the literature. These atomic data are then used to estimate expansion opacity at different temperatures (e.g., T=5000 K, 10000 K, 20000 K, 100000 K) and densities (e.g., $\rho = 10^{-13}\,\mathrm{g\,cm^{-3}},\,3\times10^{-12}\,\mathrm{g\,cm^{-3}}$). Spectral analysis has been performed with radiative transfer code POSSIS with a pre-computed opacity grid calculated with new densities and temperatures, ranging from -19.5 to -4.5 $\mathrm{g\,cm^{-3}}$ in log-scale and from 1 000 to 51 000 K, respectively. Two scenarios are considered: one in which the opacity contribution comes from 100% Se ejecta, and another in which Se contributes only partially to the total opacity ($\sim$ 10% of the total mass). Se atomic calculations show a good agreement with NIST ASD, with accurate energy levels and transitions determined alongside atomic data for higher ionisation stages not fully covered by NIST. The expansion opacities calculated with these new Se data exhibit differences in comparison to existing literature works. Se spectral features can only be observed in the KN scenario consisting of 100% Se. When Se accounts for about 10% of the total KN mass, these features become undetectable. All Se results are now available in the new open-source MARTINI platform dedicated to element nucleosynthesis.
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All authors Matteo Bezmalinovich, Mattia Bulla, Gediminas Gaigalas, Diego Vescovi, Matteo Canzari, Sergio Cristallo
Astrophysics of Galaxies
The Environmental Switch in Black Hole Feeding: Bar-Driven vs. Merger-Driven Growth in IllustrisTNG50
Harsh Uttam and Sandeep Kumar Kataria
The relative roles of secular disc processes and
galaxy interactions in driving the growth of supermassive black hole (SMBH) remain unclear. We present a time-resolved, per
galaxy analysis of SMBH mass assembly that explicitly tracks bar formation, merger events, and the environment along the main progenitor branches using the high resolution IllustrisTNG50 cosmological simulation. We analyze barred and unbarred disc
galaxies in isolated and non-isolated environments using physically motivated boundary definitions. We found that SMBH fueling pathways are regulated by the environment through the timing of bar formation relative to mergers. In isolated barred
galaxies,
stellar bars form early in dynamically cold discs and establish sustained, coherent
accretion phases that regulate late-time SMBH growth. In contrast, in non-isolated
galaxies, SMBH growth is dominated by early merger-driven
accretion episodes, whereas bars form later and contribute weakly to the primary growth phase. Unbarred control samples show that mergers can trigger rapid SMBH growth without bars, but such growth remains episodic, whereas isolated discs without bars lack sustained
accretion. These results demonstrate an environmental bifurcation in SMBH fueling: mergers act as efficient triggers of early growth in dynamically active systems, while bars regulate prolonged
accretion only when they form in quiescent discs. This study provides a unified time-domain framework linking
galaxy environment, disc dynamics, and SMBH growth by resolving the temporal ordering of bars, mergers, and
accretion.
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Astrophysics of Galaxies
A FUV-optical approach for studying hierarchical star formation in nearby galaxies with UVIT
Sanal Ananthu, Gairola Shashank, Smitha Subramanian et al. (+4 more)
Young
star-forming clumps (SFCs) emit strongly in the ultraviolet (UV), making UV imaging ideal for detecting them. The Ultraviolet Imaging
Telescope (UVIT) onboard AstroSat, with 1.5arcsec resolution, has enabled the characterization of recently formed (up to 300 Myr) SFCs on tens of parsec scales in nearby
galaxies. The spatial distribution of SFCs with different ages can provide insights into the hierarchy of
star formation. This study presents a semi-novel approach to characterize SFCs in two nearby spiral
galaxies, NGC 5457 and NGC 1313, by combining UVIT FUV data with g-band data from the Dark Energy Camera Legacy Survey (DECaLS). We tested and optimized our method on NGC 5457 and showed that after proper background subtraction, the FUV-g color of SFCs can serve as an equally reliable age indicator as the widely-used FUV-NUV color. Next, we parametrized the
star formation hierarchy in NGC 5457 using the two-point correlation function (TPCF) and found good agreement between the hierarchy parameters derived using FUV-NUV and FUV-g based ages. Using our FUV-g based SFC ages, we also constrained the global hierarchy parameter of NGC 1313 for the first time. The development of our FUV-g based method is motivated by the fact that the NUV channel of the UVIT is not operational, and there is a wealth of archival UVIT FUV-only observations of nearby
galaxies. This work demonstrates the potential of our method in constraining the SFC ages and investigating hierarchical
star formation in nearby
galaxies using FUV and optical observations.
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All authors Sanal Ananthu, Gairola Shashank, Smitha Subramanian, Rao C. Jayanth, Shyam H. Menon, Chayan Mondal, Sreedevi Muraleedharan
Cosmology and Nongalactic Astrophysics
Redshift evolution of the Hubble constant: Constraints and new insights from an interacting dark energy model
Xinyi Dai, Yupeng Yang, Yicheng Wang et al. (+3 more)
We develop a modified interacting dark energy (IDE) model to study the
redshift evolution of the Hubble constant ($H_0$), in light of the Hubble tension. In this framework, the energy exchange between dark energy and dark matter induces a
redshift dependence of $H_0$. We evaluate the model against a comprehensive suite of observations, including
baryon acoustic oscillations (BAO) from DESI DR2 and SDSS,
cosmic chronometers, type Ia
supernovae from the Pantheon sample, and Planck CMB distance priors. Analysis of late-Universe data yields $\alpha = 0.0107^{+0.0032}_{-0.011}$, with the best-fit value on the order of $10^{-2}$, revealing a decreasing trend of $H_0$ with
redshift. This supports a power-law
evolution beyond $\Lambda$CDM. Incorporating CMB data further tightens the constraint to the order of $10^{-5}$, which we attribute to the suppression of dark-sector interactions at high
redshifts, a consequence of the strong
baryon–
photon coupling. These results indicate that the IDE framework provides a theoretically consistent and observationally viable mechanism for describing the
redshift evolution of $H_0$, offering a promising avenue toward alleviating the Hubble tension.
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All authors Xinyi Dai, Yupeng Yang, Yicheng Wang, Yankun Qu, Shuangxi Yi, Fayin Wang
Solar and Stellar Astrophysics
Detection of circumstellar disks around nearby young brown dwarf candidates
N. Phan-Bao, M.S. Bessell and E.L. Martín
It is important to detect and study circumstellar disks around late-M and brown
dwarfs of nearby young associations to understand how these very low-mass objects form and how rocky
planets form around them. The detection of new very low-mass members of nearby young associations will also significantly improve our current understanding of young associations. We searched for new young very low-mass members with circumstellar disks in a sample of 3928 candidates. We constructed spectral energy distributions of all candidates using observational photometric data from DENIS, 2MASS, and WISE and trigonometric parallaxes from
Gaia to detect infrared excess emission that indicates the presence of circumstellar disks. We then followed up spectroscopic observations of candidates to search for lithium to confirm their youth. The H_alpha emission line was used to detect
accretion. We detected 23 among the 3928 candidates with circumstellar disks: Ten objects are new, and 13 were previously reported in the literature. Our mass estimates also indicate that 21 are brown
dwarf candidates and 2 are very low-mass
stars. DENIS J0534552-104808 has a
Gaia distance of 238 pc and might be the first brown
dwarf candidate member of a foreground population in front of the Orion D cloud. This foreground population is probably associated with the supergiant kappa Ori. Based on our spectroscopic observations, we detected lithium in 11 candidates. We also identified seven accretors and one potential accretor. The intense long-lived
accretion detected in DENIS-P J0500245-333042, a 20 Myr old brown
dwarf candidate may be additional evidence to favor the formation of rocky
planets around very low-mass objects.
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Earth and Planetary Astrophysics
Probing the Atmospheres of Young Long-Period Sub-Neptune Progenitors with ELT/ANDES
Spandan Dash, Dwaipayan Dubey and Liton Majumdar
High-resolution cross-correlation spectroscopy (HRCCS) has become a powerful ground-based technique for detecting and characterizing
exoplanet atmospheres. While highly successful for ultra-hot and hot Jupiters, next-generation facilities such as ELT/ANDES will observe smaller and longer-period
planets, including young sub-Neptunes and their progenitors. We investigate whether HRCCS with ELT/ANDES can robustly recover orbital parameters and atmospheric signals for the long-period sub-Neptunes V1298 Tau b and TOI-451 c. In long-period systems, the slow Doppler drift during a single night limits separation between planetary and telluric signals, increasing the risk of signal loss during detrending. We therefore quantify the impact of including out-of-transit exposures on signal recovery and parameter estimation. We simulate YJH-band transmission observations using the Ratri pipeline and analyze them with the HRCCS detrending and cross-correlation framework Upamana. For V1298 Tau b, injected atmospheric models are consistent with HST, Spitzer, and JWST constraints. For TOI-451 c, we explore sub-
solar to super-
solar C/O ratios to test compositional sensitivity. Incorporating out-of-transit exposures significantly improves detectability, provided detrending effects are consistently propagated to the template spectra prior to cross-correlation. Without this step, orbital parameters can deviate from injected values and detection significance decreases. For V1298 Tau b, $>4\sigma$ detections of H$_2$O, H$_2$S, and CO are achievable at $\lesssim$10 hours (minimum 2 nights, cloud-free scenario). For TOI-451 c, distinguishing sub-
solar and
solar from super-
solar C/O requires $\sim$17 hours (minimum 4 nights). HRCCS with ELT/ANDES will therefore be a key tool for atmospheric characterization of young, long-period sub-Neptunes in the ELT era.
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High Energy Astrophysical Phenomena
Black hole Limits Redefined: Extreme Efficiency in Black Hole Jets
Antonios Nathanail
Relativistic jets from black holes can extract energy not only from
accretion but also directly from the black hole's
spin, as described by the Blandford-Znajek mechanism. A longstanding question is whether
magnetic flux can accumulate near the event horizon to such an extent that it halts
accretion entirely, enabling energy extraction purely from
spin. Previous studies have shown that
accretion persists through instabilities and that jet power only modestly exceeds the
accretion energy budget, yet some observational results suggest much higher efficiencies. Here we present state-of-the-art general relativistic magnetohydrodynamic (GRMHD) simulations that sustain a quasi-steady magnetically arrested disk state for approximately 10,000 dynamical times, during which
accretion is globally suppressed across the full azimuthal extent. In this regime, jet power exceeds the
accretion energy input by more than two orders of magnitude, demonstrating a previously unachieved level of efficiency. These results challenge conventional assumptions about the limits of black hole energy extraction and suggest a new framework for interpreting powerful jet systems. Our findings raise important questions about the long-term stability of such states and the fundamental limits of the Blandford-Znajek process.
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Earth and Planetary Astrophysics
Gaia DR3 supervised classification of asteroid reflectance spectra
Marco Delbo, Thomas Dyer, Ullas Bhat et al. (+3 more)
We present a supervised, probabilistic taxonomic classification of asteroid reflectance spectra from
Gaia Data Release 3 (DR3). Using high-quality
Gaia DR3 spectra and a reference set of spectra from the literature consisting exclusively of asteroids with robust spectroscopic taxonomic types, we construct a principal-component (PC) representation of the
Gaia reflectances. For each major spectral complex (C, S, X) and several end-member classes (B, D, A, L, K, V), we model the distribution of reference objects in PC space using multivariate kernel density estimation (KDE). This yields likelihoods for each spectral class and provides a quantitative measure of classification confidence. Validation against a sample of objects with known spectral classes demonstrates good performance for classes with distinctive reflectance signatures, including the S-complex, D, V, and A types. Spectrally continuous classes (B-C-complex, K-L-S-complex, and X-complex) show the expected degrees of mixing given the limited wavelength range of
Gaia's spectrophotometry. We further explore the compositional structure of six major asteroid collisional families using our
Gaia-derived spectral classes, finding excellent agreement with ground-based spectroscopy and revealing enhanced detections of olivine-rich A type material in the Flora and Eunomia families, as well as new insights into the spectral diversity of the Tirela family. The resulting catalogue constitutes a fully probabilistic taxonomic classification for the full
Gaia DR3 asteroid sample. It offers a resource for studying the compositional structure of the main belt, identifying family interlopers, and linking asteroid populations to meteorite groups, and establishes a methodological framework for future
Gaia releases, in particular for the validation of the
Gaia DR4, expected by the end of 2026.
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All authors Marco Delbo, Thomas Dyer, Ullas Bhat, Chrysa Avdellidou, Laurent Galluccio, Amelia Milton
Solar and Stellar Astrophysics
Statistical Study of Rapid Blue Excursions as Mass Conduits in Solar Atmosphere
Govindswaroop Rahangdale
Rapid Blue Excursions (RBEs) are transient blue-shifted chromospheric absorption features widely interpreted as the on-disk counterparts of Type II
solar spicules. We investigate their dynamic properties using high-cadence spectral observations combined with automated detection and spatio-temporal tracking
algorithms. RBEs were identified through blue-wing Doppler asymmetry criteria and tracked using spatial connectivity and centroid continuity methods to determine lifetimes and kinematic
evolution. The statistical analysis shows that RBEs are short-lived events with lifetimes predominantly between 20 to 60 s and a mean duration of approximately 75 s. The lifetime distribution follows an exponential decay profile, indicative of impulsive driving. Line-of-sight velocities range from 20 to 140 km s-1, with a mean near 26 km s-1. Projected lengths span 1.2-5.5 Mm with sub-arcsecond widths, and recurrence analysis reveals repeated activity at localized
magnetic footpoints. Mass flux estimates suggest that RBEs transport significant
plasma upward, contributing to chromospheric mass supply toward the corona. These findings reinforce the role of RBEs as dynamic conduits of mass transfer and key elements in chromosphere-corona coupling.
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Cosmology and Nongalactic Astrophysics
(1+1)-Dimensional Schrödinger-Poisson equation with contact interaction
Óscar Rodríguez-Villalba, Ivan Saychenko, Massimo Pietroni et al. (+1 more)
We investigate the role of contact interactions in the dynamics of fuzzy dark matter (FDM) modeled through the Schrödinger-Poisson equation in one spatial dimension. While the $\Lambda$CDM paradigm successfully explains structure formation on large scales, its small-scale predictions remain in tension with observations. FDM offers an alternative framework, where local self-interactions can further influence the formation and
evolution of structures. We explore both attractive and repulsive contact interactions in static and expanding backgrounds. Using numerical simulations, we examine their impact on three key scenarios: the properties of the lowest-energy stationary solution, the relaxation of localized initial states, and the gravitational collapse of nonlocalized states. Our results show that contact interactions modify the density profile of the stationary solution and affect the onset of characteristic stages of gravitational collapse, particularly the shell-crossing event. In the (1+1) model, we confirm that relaxation does not converge to the lowest-energy stationary solution, even when local self-interactions are included. Taken together, local self-interactions play a relevant role in shaping the nonlinear dynamics of FDM and motivate further studies in higher-dimensional and cosmologically realistic settings.
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All authors Óscar Rodríguez-Villalba, Ivan Saychenko, Massimo Pietroni, Sandro Wimberger
High Energy Astrophysical Phenomena
Trial dispersion measure spacing in fast radio burst searches with HEIMDALL
E. F. Keane and D. J. McKenna
Fast
radio bursts (FRBs) are brief flashes of emission detectable to cosmological distances. Cosmology applications rely on an understanding of how the detected sample relates to the underlying population. To this end we examine the dispersion measure `tolerance' parameter employed by the FRB search tool heimdall and provide the relation between this and minimum search depth. Several FRB samples can be `retro-fitted' using this to more properly account for survey completeness.
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Cosmology and Nongalactic Astrophysics
The ASKAP Variables and Slow Transients (VAST) Extragalactic Survey - Data Release 1
Iris de Ruiter, Dougal Dobie, Tara Murphy et al. (+13 more)
The Variables and Slow Transients (VAST) Survey on the Australian SKA Pathfinder (ASKAP) is designed to systematically explore the dynamic
radio sky, detecting sources that vary on timescales from minutes to several years. In this paper, we present Data Release 1 of the VAST Extragalactic Survey, which targets slowly evolving synchrotron transients in the southern sky. The observations were carried out between June 2023 and May 2025, comprising 2945 images of 276 fields spanning $\sim 12300\ \mathrm{deg}^2$, observed at 888 MHz with a typical rms sensitivity of 0.24 mJy $\rm{beam}^{-1}$ and 12-20 arcsec resolution. Each field was revisited approximately every two months, yielding 10 or 11 observations per field. The VAST pipeline extracts the light curves for all the observed sources, and additional filters are implemented to improve the reliability of the resulting light curve database. The light curve database contains 0.5 million sources and 6.4 million individual measurements, publicly available through the CSIRO data access portal. An untargeted variability search yields 117 astrophysical variables, including 27
pulsars, 40
radio stars (10 newly detected at
radio wavelengths), 44 active
galactic nuclei, two optically identified
supernovae, one
supernova candidate, one brown
dwarf, and two sources without multi-wavelength counterparts that are yet to be identified. This data release provides the first large-scale, high-cadence, uniform view of long-term
radio variability in the extragalactic sky and lays the groundwork for future population studies of
radio transients with ASKAP.
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All authors Iris de Ruiter, Dougal Dobie, Tara Murphy, David L. Kaplan, Emil Lenc, Akash Anumarlapudi, Laura N. Driessen, Ashna Gulati, Assaf Horesh, James K. Leung, Joshua Pritchard, Kovi Rose, Elaine M. Sadler, Gregory Sivakoff, Yuanming Wang, Ziteng Wang
Astrophysics of Galaxies
Beyond Colors: Probing Redshifts from Galaxy Morphology in Single-band Images with ViT-MDNz
Zhijian Luo, Yangyang Li, Jianzhen Chen et al. (+5 more)
To address the challenge of estimating
redshifts when only single-band images are available, this study introduces a deep learning model named ViT-MDNz. Leveraging robust statistical priors learned from large-scale data concerning the correlation between
redshift and morphology, the model can directly estimate
redshifts and their associated uncertainties from single-band
galaxy images. It integrates a
Vision Transformer (ViT) to extract deep morphological features and a Mixture Density Network (MDN) to predict the full
redshift probability density function. Trained and evaluated on approximately 300,000 single-band images from the DESI Legacy Imaging Surveys (DESI-LS), the model achieves a normalized median absolute deviation $\sigma_{\rm NMAD} = 0.034$ and an outlier fraction $f_{\rm out} = 2.6\%$ in the $r$-band for
redshifts up to $z \lesssim 1$. Evaluations using probability integral transform (PIT) and continuous ranked probability score (CRPS) confirm that the predicted probability density functions are well calibrated and closely match the true distribution. These results demonstrate that competitive
redshift estimates can be obtained using morphological features alone, and that incorporating color information further enhances the accuracy and robustness of the estimation. Therefore, ViT-MDNz provides a practical approach for
redshift estimation of
galaxy samples with limited photometric band coverage, contributing to improved completeness and usability of
redshift catalogs for future large-scale surveys such as DESI and LSST.
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All authors Zhijian Luo, Yangyang Li, Jianzhen Chen, Qishen Cao, Duo Cao, Shaohua Zhang, Hubing Xiao, Chenggang Shu