Earth and Planetary Astrophysics
NEO and imminent impactor discoveries from Hungary: recent results and lessons learnt
Norton O. Szabo, Krisztian Sarneczky, Laszlo L. Kiss et al. (+15 more)
2022 EB5, 2023 CX1 and 2024 BX1: these are the three recent imminent impactor discoveries from the Piszkéstető Mountain Station of the Konkoly Observatory. They make up about one percent of all NEO discoveries from our observatory and here we provide a detailed description of our approach and methodology that led to this noticeable observational sensitivity to these meter-sized impactors. After outlining the historical background of astronomical discoveries from Hungary, we introduce our recently upgraded survey instrumentation and outline the observational strategy and its implementation. We highlight the importance of strong feedback between analysis and ongoing data collection, maximizing the value of immediate follow-up. Finally, we discuss plans for moving forward to increase the sensitivity and the temporal coverage of our survey.
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All authors Norton O. Szabo, Krisztian Sarneczky, Laszlo L. Kiss, Szabolcs Velkei, Attila Bodi, Zsofia Bora, Balazs Csak, Borbala Cseh, Agoston Horti-David, Andras Joo, Csilla Kalup, Zoltan Kuli, Laszlo Meszaros, Andras Pal, Balint Seli, Adam Sodor, Robert Szakats, Nora Takacs
Cosmology and Nongalactic Astrophysics
Probing Cosmic Magnetism with Rotation Measure-Squared-Galaxy Cross-Correlations
Zekai Zhang and Adam Lidz
We present a new approach for extracting information about
cosmic magnetic fields using cross-correlations between extragalactic Faraday rotation measure (RM) catalogs and
galaxy surveys. Specifically, we propose measuring the two-point cross-correlation between RM squared, ${\rm RM}^2$, towards background sources and the projected density field of foreground
galaxies, $\langle {\rm RM}^2 \times {\rm g} \rangle$, as a function of transverse separation. This statistic is analogous to the ”projected fields”
estimator used for the kinetic Sunyaev-Zel'dovich (kSZ) effect, $\langle {\rm kSZ}^2 \times {\rm g} \rangle$. Our
estimator avoids contamination, and is also free from the noise bias that arises when correlating the absolute value of the RMs with
galaxies. Moreover, by binning in foreground
galaxy redshifts, $\langle {\rm RM}^2 \times {\rm g} \rangle$ enables a tomographic reconstruction of the
redshift evolution of large-scale
cosmic magnetic fields. We model this statistic using the Illustris-TNG cosmological magnetohydrodynamic simulations and compare with approximate analytic predictions. We show that $\langle {\rm RM}^2 \times {\rm g} \rangle$ can be related to a bispectrum involving two copies of the electron-density–weighted
magnetic field strength and one of the
galaxy overdensity. In Illustris-TNG, the effective field strength is primarily set by the
magnetic field amplitudes within the inner regions of
galaxy-hosting dark matter
halos. It increases towards low
redshift, driven by dynamo amplification and magnetized
outflows. Our forecasts suggest that $\langle {\rm RM}^2 \times {\rm g} \rangle$ is detectable at high significance with current
galaxy surveys and future RM catalogs from the SKA, offering a tomographic probe of large-scale
magnetic fields across
cosmic time.
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Astrophysics of Galaxies
Rotational Spectra and Search for Aromatic Imines: 9-Iminofluorene and Benzophenone imine
Huanyu Ren, D. Archie Stewart, Gabi Wenzel et al. (+4 more)
Interstellar detections of several cyano derivatives of large polycyclic aromatic hydrocarbons (PAHs) have now been achieved, enabled by accurate laboratory measurements of their microwave rotational spectra. These results highlight the continued promise of other N-containing unsaturated PAHs, such as aromatic imines, as candidates for future laboratory studies and astronomical searches. In this work, we present broadband spectroscopic measurements of 9-iminofluorene and benzophenone imine in the 6-18\,GHz band. These measurements yield accurate rotational, centrifugal distortion, and $^{14}$N quadrupole coupling constants for both molecules. Using these experimentally-derived constants, we attempted a search for both molecules in the cold molecular cloud TMC-1 using observations from the Green Bank
Telescope (GBT). Neither of these two ketimines was detected above the current noise level, establishing upper limits for their column densities of $5.1\times10^{12}\,\text{cm}^{-2}$ for 9-iminofluorene and $1.3\times10^{13}\,\text{cm}^{-2}$ for benzophenone imine. We also attempted a search for phenylmethanimine (both E/Z isomers) as the simplest aromatic aldimine, but neither was detected in TMC-1. To provide insight into these non-detections, we propose and evaluate different formation pathways using respective potential energy surfaces as determined by high-precision
quantum chemical calculations. The result suggests the presence of an entrance barrier to forming the intermediate species, potentially explaining the low abundance.
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All authors Huanyu Ren, D. Archie Stewart, Gabi Wenzel, Thomas H. Speak, Martin S. Holdren, Reace H. J. Willis, Brett A. McGuire
Cosmology and Nongalactic Astrophysics
Angular BAO Forecasts for the IBIS Medium-Band Survey
Richard M. Feder and Martin White
Ongoing and near-future spectroscopic surveys, such as DESI, DESI-II and Spec-S5, rely on imaging-based selections to construct uniform, three-dimensional tracers of large-scale structure. While spectroscopic data from these surveys constrain the baryonic acoustic oscillation (BAO) feature with high precision, the imaging surveys used for target selection can provide useful information on the angular diameter distance $D_A(z)$. In this work we explore the feasibility of angular BAO measurements for the Intermediate-Band Imaging Survey (IBIS) using recent constraints on clustering from a pilot survey spanning $2.2<z<3.5$. Through Fisher forecasts, we find that a 5000 deg$^2$ survey of LAEs with realistic bias, a tracer density of $2\times 10^{-4}$ (h/Mpc)$^3$ and interloper fraction $f_{\rm int}=10\%$ can constrain the BAO dilation parameter $\alpha$ at $z_{\rm eff}=2.8$ with a precision of 2.6%, with dependence on the sample properties that is consistent with shot noise-dominated measurements. We then explore medium-band survey specifications for the planned Stage-V Spectroscopic Instrument (Spec-S5) and beyond, demonstrating the potential for precise high-
redshift BAO measurements. Our forecasts motivate early measurements of BAO from these imaging surveys, which may inform later spectroscopic analyses.
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Earth and Planetary Astrophysics
Exoplanets synchronization in the habitable zone: Learning from Venus' retrograde rotation
Sylvio Ferraz-Mello
The rotation of a
planet located in the habitable zone of a
solar-type
star can be reversed by a smooth process associated with the formation of its atmosphere and the increase of stronger torques, opposite to normal
tidal torques. Our understanding of the rotational dynamics of Venus is revisited to analyze what might happen to
exoplanets in the habitable zone of a
solar-type
star. The creep tide theory is used to calculate the gravitational
tidal torque. Mathematical analysis is used to study the differential equation resulting from the combined effects of
tidal torque and atmospheric torque. It shows that no collision with other bodies or critical planetary perturbations is necessary to convert the rotation of an Earth or super-Earth with a significant atmosphere formed during its
evolution into a retrograde rotation. The reversal of a
planet's rotation is not an exceptional event and may have occurred many times among known
exoplanets in the habitable zone. It is sufficient for the
planet to be at a sufficiently short distance from its host
star to allow
tidal torques to nearly synchronize the
planet's rotation before most of its atmosphere forms (but not so close that
stellar radiation destroys the formed atmosphere). When atmospheric torques become more important than
tidal torques, a pitchfork bifurcation occurs: the synchronous attractor bifurcates into two asynchronous attractors, and the system evolves toward one of the asynchronous attractors. If it evolves toward the subsynchronous branch, the rotation may subsequently become retrograde. Venus's rotation is an example. None of these processes is catastrophic. Planetary atmosphere formation is a continuous and smooth process, which may be more or less efficient, but it is not a low-probability event.
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Astrophysics of Galaxies
Actions of highly eccentric orbits
Thomas J Wright and James Binney
The challenge presented by computing actions for eccentric orbits in axisymmetric potentials is discussed. In the limit of vanishing angular momentum about the potential's
symmetry axis, there is a clean distinction between box and loop orbits. We show that this distinction persists into the regime of non-zero angular momentum. In the case of a Staeckel potential, there is a critical value I_{3crit}(E) of the third integral I_3 below which I_3 does not contribute to the centrifugal barrier. An orbit is of box or loop type according as its value of I_3 is smaller or greater than I_{3crit}. We give
algorithms for determining I_{3crit}(E) and the critical action Jzcrit below which orbits in any given potential are boxes. It is hard to compute the actions and especially the frequencies of orbits that have Jz ~ Jzcrit using the Staeckel Fudge. A modification of the Fudge that alleviates the problem is described.
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Astrophysics of Galaxies
A New Torus Generator for AGAMA
James Binney, Thomas J Wright and Eugene Vasiliev
Code is presented that computes and exploits orbital
tori for any axisymmetric gravitational potential. The code is a development of the AGAMA software package for action-based
galaxy modelling and can be downloaded as the AGAMAb code library. Although coded in C++, most of its functions can be accessed from Python. We add to the package functions that facilitate confronting models with data, which involve sky coordinates, lines of sight, distances, extinction, etc. The new
torus generator can produce
tori for both highly eccentric and nearly circular orbits that lie beyond the range of the earlier
torus-mapping code.
Tori can be created by interpolation between
tori at very low cost.
Tori are fundamentally devices for computing ordinary phase-space coordinates from angle-action coordinates, but AGAMAb includes an action finder that returns angle-action coordinates from any given phase-space location. This action finder yields the
torus through the given point, so it includes the functionality of an orbit integrator. The action finder is more accurate and reliable but computationally more costly than the widely used Staeckel Fudge. We show how AGAMAb can be used to generate sophisticated but cheap models of
tidal streams and use it to analyse data for the GD1 stream. With the most recently published distances to the stream, energy and angular momentum imply that the end that must be leading is trailing, but extremely small changes to the distances rectify the problem.
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Astrophysics of Galaxies
The impact of surface acetylene cyclotrimerization on the abundance of aromatic hydrocarbons in carbon-rich asymptotic giant branch stars
M. S. Murga, I. V. Loginov, D. S. Wiebe et al. (+3 more)
This work investigates the catalytic role of
dust grains in forming aromatic hydrocarbons via acetylene cyclotrimerization on their surfaces within the circumstellar envelopes of carbon-rich asymptotic
giant branch (AGB)
stars. We present a comprehensive computational astrochemical model coupling the gas-phase, gas-surface, and surface (cyclotrimerization) reactions, and the physical
evolution of the
dust grains (coagulation). The model expands upon the basic chemical network from previous models, enhancing them with updated reactions involving hydrocarbons up to pyrene. We applied this model to simulate the chemical
evolution of the envelope of the prototypical AGB
star IRC+10216, utilizing physical conditions derived from a hydrodynamical model available in literature. To quantify the impact of surface chemistry, we compared scenarios with and without the cyclotrimerization reaction, further testing the sensitivity of our results by varying the key parameter of hydrocarbon desorption energy. We find that surface-catalyzed cyclotrimerization is a viable pathway for aromatic formation in circumstellar environments, capable of enhancing the total abundance of aromatic species by up to an order of magnitude. Crucially, we show that gas-phase chemistry and
dust surface processes are intrinsically linked; their synergistic
evolution should be modeled self-consistently to accurately predict chemical abundances. This work underscores that constraining uncertain parameters, particularly desorption energies of hydrocarbons, is essential for future realistic modeling of astrochemical processes in evolved
stellar systems.
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All authors M. S. Murga, I. V. Loginov, D. S. Wiebe, D. R. Fedotova, V. S. Krasnoukhov, I. O. Antonov
Earth and Planetary Astrophysics
Venus as an exoplanet analog: extended UV transit signatures and coronal occultations
Tisyagupta Pyne, Belur Ravindra and Ravinder K. Banyal
Stellar activity manifests differently across wavelengths, causing flux variability that can obscure planetary transits. While transit observations are typically performed in the visible and infrared bands, where
stellar flux is relatively stable, short-wavelength regimes exhibit high variability, complicating reliable detections. Here, we analyze the 2012 transit of Venus as an
exoplanet analog using multiwavelength observations taken by the
Solar Dynamics Observatory (SDO) in five channels: 6173~Å\ (continuum), 1700~Å\ (broadband), and three extreme-UV (EUV) narrowbands at 304~Å, 171~Å, and 94~Å. We find that the disk-integrated transit signal is clearly detectable in the 6173~Å\ band, whereas strong
solar activity-induced fluctuations obscure the transit in the EUV channels. Notably, the 1700~Å\ UV transit is noisier but significantly longer ($\approx 9.2$~hrs) than the visible-band transit ($\approx 6.7$~hrs), because Venus began occulting the extended coronal features before ingress onto the visible disk. This observation highlights the potential of UV transits to probe the spatial extent of
stellar coronae in exoplanetary systems. Numerical simulations further suggest that limb-brightened
stars in quiescence phase may exhibit distinctive UV/EUV transit signatures, opening new possibilities for
exoplanet detection and characterization in these spectral regimes.
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High Energy Astrophysical Phenomena
Optical Study of TRAPUM Pulsars and Modelling of the Redbacks: PSR J1036$-$4353 and PSR J1803$-$6707
A. Phosrisom, R. P. Breton, C. J. Clark et al. (+12 more)
The Transients and
Pulsars with MeerKAT (TRAPUM) project discovered eight binary millisecond
pulsars in its first shallow L-band survey of unidentified
Fermi $\gamma$-ray sources using the MeerKAT
radio telescope. We conducted follow-up observations using ULTRACAM on the New Technology
Telescope at the La Silla Observatory to search for the optical counterpart to the
pulsar companions. We found two redback companions, in PSRs J1803$-$6707 and J1036$-$4353, and provided upper limits for the other
pulsar binaries. We used the Icarus code to fit the redback's light curves using various irradiation models. The asymmetric double-peak light curves of PSR~J1036$-$4353 are best fit with
diffusion and convection models. Comparing the two prescriptions of irradiation and
gravity darkening, models with post-irradiation
gravity darkening provide superior fits (particularly for lower
gravity-darkening exponents), suggesting that the irradiation energy is deposited deep in the
stellar photosphere. PSR~J1803$-$6707, on the other hand, displayed variability in the amplitude of its irradiation-dominated light curves over a time scale of a few months. This effect can be modelled only if the companion's filling, irradiation temperature, and convection coefficients are allowed to vary over time. Had the
star been closer to filling its Roche lobe, like in the cases of the known transitional millisecond
pulsars J1023+0038 and J1227$-$4853, this 4.1 per~cent variation in the volume-averaged filling of the
star would have caused it to experience a state change to form an active
accretion disc.
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All authors A. Phosrisom, R. P. Breton, C. J. Clark, M. Burgay, J. Strader, L. Chomiuk, K. V. Sokolovsky, I. Molina, R. Urquhart, M. R. Kennedy, S. J. Wagner, V. S. Dhillon, O. G. Dodge, B. W. Stappers, T. Thongmeearkom
Earth and Planetary Astrophysics
Deciphering transmission spectra by exploring the solar paradigm
Nina-Elisabeth Nèmec, Òscar Porqueras- Léon, Ignasi Ribas et al. (+1 more)
Transmission spectroscopy probes
exoplanet atmospheres via the wavelength dependence of transit depths, but
stellar contamination from
magnetic activity can significantly bias these measurements. Activity-induced changes in the chromatic apparent
stellar radius represent a major challenge for atmospheric characterisation. As surface distributions of
magnetic features are generally unknown for
stars other than the Sun, we adopt the Sun as a
benchmark to study how the chromatic effect depends on the distribution of spots and faculae. Using spot and facular masks derived from SDO/HMI magnetograms and intensitygrams, combined with the SATIRE model, we compute the chromatic dependence of the Sun's apparent radius. We test different methods of convolving surface coverage with spectra the identify physical drivers of the effect. We find that simplified approaches, which neglect the CLV, underestimate the apparent radius, particularly for faculae, whose surface coverage dominates at near-
solar activity levels. Proper treatment of facular CLV is therefore essential. The activity-induced variation between
solar minimum and maximum reaches around 40 ppm for a Jupiter-like transit, exceeding JWST's expected 10 ppm noise floor, while remaining at around 0.4 ppm for an Earth-like transit.
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All authors Nina-Elisabeth Nèmec, Òscar Porqueras- Léon, Ignasi Ribas, Alexander I. Shapiro
Astrophysics of Galaxies
Unified models revisited I: modelling the effect of source geometry on radio galaxy/quasar unification
Siddhant Pinjarkar, Martin J. Hardcastle, Jonathon C.S. Pierce et al. (+1 more)
The orientation-based unification model proposes that
radio-loud
quasars and
radio galaxies are the same objects observed at different angles. A key prediction of this model is that the
quasars are seen at smaller angles to the line of sight and so should be more affected by projection, and hence apparently physically smaller, than corresponding
radio galaxies, but this has not always been found in earlier studies. We argue that the interpretation of observations requires a less simplistic model for the effects of projection, which takes into account
radio sources' finite width and their intrinsic axial ratio distribution. Using this cylindrical configuration as a basis for the simulation of
radio galaxies and
quasars, we simulate the distribution of the linear size ratio of
quasars to
radio galaxies for different sample sizes and critical angles. Our simulations that predict the ratio of observed lengths in the presence of a distribution of intrinsic physical sizes and axial ratios that we derive from observation. We conclude that to test the unified scheme, samples should be completely optically identified, sizes should be measurable for all targets, and the sample size should be greater than $\sim 800$ sources. Such large samples with uniform optical identification and accurate size measurements have not been available in previous work, but should become available from wide-area sky surveys in the near future.
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All authors Siddhant Pinjarkar, Martin J. Hardcastle, Jonathon C.S. Pierce, Frits Sweijen
Cosmology and Nongalactic Astrophysics
Testing the Distance Duality Relation with Cosmological Observations at high Redshift using Artificial Neural Network
Yukang Xie, Yang Liu, Puxun Wu et al. (+2 more)
The
cosmic Distance Duality Relation (DDR) is a fundamental prediction of metric
gravity under
photon number conservation. In this work, we perform a model-independent test of the DDR using Pantheon+ type Ia
supernovae (SN Ia),
Fermi gamma-ray bursts (GRBs) with the FULL and GOLD samples, the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2)
baryon acoustic oscillation (BAO) measurements, and the
galaxy-scale strong gravitational
lensing (SGL) system samples at high
redshift $0.01 < z \lesssim 8$ using an artificial neural network (ANN) approach. Our results show that the standard DDR is consistent with cosmological observations at high
redshift within the $\sim 2 \sigma$ confidence level.
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All authors Yukang Xie, Yang Liu, Puxun Wu, Xiangyun Fu, Nan Liang
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Constraining meV Axion Dark Matter with ALMA Observations of the Galactic Center Magnetar SGR 1745-2900
Javier De Miguel, Evanthia Hatziminaoglou, Frédéric Poidevin et al. (+4 more)
We report a mm-wave search for
axion dark matter from SGR 1745-2900, based on 4.8 h of ALMA observations. No candidate features are found between 133.99-135.78, 135.91-137.70, 145.99-147.78, and 147.99-149.78~GHz, corresponding to 0.55-0.62 meV. Interpreting this null result within a state-of-the-art
stellar framework, we derive sensitivity to the
axion-
photon coupling at the level of $g_{\gamma}\gtrsim 2\times10^{-11}$ GeV$^{-1}$ under a standard Navarro-Frenk-White profile; down to $g_{\gamma}\gtrsim 2\times10^{-13}$ GeV$^{-1}$ upon accounting for a dense dark-matter spike around Sagittarius A*, probing the
quantum chromodynamics
axion parameter space.
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All authors Javier De Miguel, Evanthia Hatziminaoglou, Frédéric Poidevin, Nanda Rea, Daniel L. Walker, Davide De Grandis, Jaime Prieto-Polo
Earth and Planetary Astrophysics
Water vapor emission at the warm cavity wall of the HD 100546 disk as revealed by ALMA
Luna Rampinelli, Stefano Facchini, Margot Leemker et al. (+5 more)
We present spatially resolved ALMA observations of the water line at 183 GHz in the disk around the Herbig
star HD 100546. The water vapor emission peaks at the inner edge of the warm
dust cavity, located ~15 au from the central
star. We attribute this to thermal desorption at the water snowline, shifted outward at the
dust cavity wall directly heated by the intense radiation. This represents the first spatially resolved image of the water snowline using ALMA observations of the main water isotopologue in a protoplanetary disk. The water emission morphology peaking inside the first
dust ring is consistent with previous ALMA detections of oxygen-bearing complex organic molecules in the disk, including thermally desorbed methanol. These findings signal that warm cavities of transition disks provide ideal targets to directly reconstruct the spatial distribution of water vapor and the snowline location with ALMA, and directly connect water vapor emission to ice desorption of complex organic species.
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All authors Luna Rampinelli, Stefano Facchini, Margot Leemker, Andrea Isella, Pietro Curone, Myriam Benisty, Elizabeth M. Humphreys, Leonardo Testi
Earth and Planetary Astrophysics
Modelling dust coagulation, dynamical drag and turbulent mixing during star and disc formation
Matthew R. Bate, Mark A. Hutchison and Daniel Elsender
Planet formation in the discs around young
stars involves the coagulation of sub-micron sized
dust grains into much larger grains that may be mixed by
turbulence and migrate through the disc. In this paper, we describe how we have combined a method for modelling the coagulation of a population of
dust grains with the MULTIGRAIN
algorithm for modelling the dynamical
evolution of a population of
dust grains that are subject to strong gas drag. We solve the dynamical
evolution of the
dust grains due to gas drag using a recently-developed implicit integration method, and we introduce a new implicit method to model the
diffusion of the
dust due to unresolved hydrodynamic
turbulence. The resulting smoothed particle hydrodynamics (SPH) code allows us, for the first time, to model the growth, mixing and migration of
dust grain populations during the early stages of
star formation and the formation, growth and
evolution of a young protoplanetary disc using three-dimensional hydrodynamical simulations. In doing so, we find that including turbulent
dust diffusion within the disc provides a substantial enhancement of the rate of
dust grain growth due to the fact that the turbulent
diffusion provides a source of small and intermediate
dust grains to the regions in which the largest
dust grains are growing.
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High Energy Astrophysical Phenomena
Rebrightenings of gamma-ray burst afterglows from an increasing magnetic inclination angle of a nascent magnetar
M. Xu, J. Li, C. F. Xiao et al. (+1 more)
A nascent magnetar, accompanying a gamma-ray burst (GRB) explosion, releases enormous rotational energy via
magnetic dipole radiation. The energy loss rate of the magnetar is determined by the strength of the
magnetic field at the pole. We investigated the effect of the
magnetic inclination angle on the energy loss rate. The released energy is injected into the GRB jet and shapes the light curves of GRB afterglow. Different evolutionary approaches lead to different curves shapes.A shallow decay phase in GRB X-ray afterglow may result from energy injection from a magnetar with a fixed inclination angle. A two-plateau phase may result from a decreasing inclination angle scenario. In this study, we considered an increasing inclination angle scenario. The energy loss rate of the magnetar increases as the
magnetic inclination angle grows. Our analysis reveals that as the lost rotational energy injected into the GRB jet increases, rebrightening phases occur in the GRB afterglows. The rebrightening features are slight and short-lived. The observed afterglow rebrightening of GRB 170822A and GRB 230414B can be well explained within our framework. Some GRB X-ray afterglows that exhibit slight and early rebrightenings may result from an increasing
magnetic inclination angle of a nascent magnetar.
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All authors M. Xu, J. Li, C. F. Xiao, H. H. Qiu
Solar and Stellar Astrophysics
Photometric Analysis of TCP J20171288$+$1156589 – WZ Sge Type Dwarf Nova with Delayed Ordinary Superhumps Emergence
Alexander Tarasenkov, Sergey Shugarov, Natalia Ikonnikova et al. (+3 more)
We present the results of photometric analysis of WZ Sge type
dwarf nova TCP J20171288$+$1156589. This object exhibited an outburst with a large amplitude of $>7.9$ magnitudes and was observed for over a month. The photometric
evolution of the superoutburst was atypical for WZ Sge-type
dwarf novae. Periodogram analisys reveals early superhumps with the most probable period of $0.0611\pm0.0001$ days during the initial decline. After a plateau phase of approximately 11 days, ordinary superhumps (likely stage B) emerged with a period of $0.0616\pm0.0001$ days, corresponding to a superhump excess of $\epsilon=0.008$ correspondingly. This delay in the onset of ordinary superhumps is an unusual feature among WZ Sge
stars. We evaluated the main parameters of the system: mass ratio $q=M_{RD}/M_{WD}=0.06\pm0.005$, yielding component masses of $M_{WD}\sim1.0\pm0.15M_{\odot}$ for the white
dwarf and $M_{RD}=0.06\pm0.01M_{\odot}$ for the donor. The estimated distance to the system is $\sim850$ pc, and the binary separation is $a=0.67\pm0.03R_{\odot}$.
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All authors Alexander Tarasenkov, Sergey Shugarov, Natalia Ikonnikova, Marina Burlak, Sergey Nazarov, Sjoerd Dufoer
Cosmology and Nongalactic Astrophysics
A Fully Photometric Approach to Type Ia Supernova Cosmology in the LSST Era: Host Galaxy Redshifts and Supernova Classification
Ayan Mitra, Richard Kessler, Rebecca C. Chen et al. (+9 more)
The upcoming Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) is expected to discover nearly a million Type Ia
supernovae (SNeIa), offering an unprecedented opportunity to constrain dark energy. The vast majority of these events will lack spectroscopic classification and
redshifts, necessitating a fully photometric approach to maximize cosmology constraining power. We present detailed simulations based on the Extended LSST Astronomical Time Series Classification Challenge (ELAsTiCC), and a cosmological analysis using photometrically classified SNeIa with host
galaxy photometric
redshifts. This
dataset features realistic multi-band light curves, non-SNIa contamination, host mis-associations, and transient-host correlations across the high-
redshift Deep Drilling Fields (DDF) (~ 50 deg^2). We also include a spectroscopically confirmed low-
redshift sample based on the Wide Fast Deep (WFD) fields. We employ a joint SN+host photometric
redshift fit, a neural network based photometric classifier (SCONE), and BEAMS with Bias Corrections (BBC) methodology to construct a bias-corrected Hubble diagram. We produce statistical + systematic covariance
matrices, and perform cosmology fitting with a prior using
Cosmic Microwave Background constraints. We fit and present results for the wCDM dark energy model, and the more general Chevallier-Polarski-Linder (CPL) w0wa model. With a simulated sample of ~6000 events, we achieve a Figure of Merit (FoM) value of about 150, which is significantly larger than the DESVYR FoM of 54. Averaging analysis results over 25 independent samples, we find small but significant biases indicating a need for further analysis testing and development.
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All authors Ayan Mitra, Richard Kessler, Rebecca C. Chen, Alex Gagliano, Matthew Grayling, Surhud More, Gautham Narayan, Helen Qu, Srinivasan Raghunathan, Alex I. Malz, Michelle Lochner, The LSST Dark Energy Science Collaboration
High Energy Astrophysical Phenomena
Revealing Hidden Repeaters in the CHIME/FRB Catalog: Semi-Supervised Insights into the Fast Radio Burst Population
N. Mankatwit, P. Thongkonsing, S. Loekkesee et al. (+3 more)
Fast
radio bursts (FRBs) are millisecond-duration extragalactic transients, observationally classified as repeaters or nonrepeaters. This classification may be biased, as some apparently non-repeating sources could simply have undetected subsequent bursts. To address this, we develop a semi-supervised learning framework to identify distinguishing features of repeaters using primary observational parameters from the Blinkverse database, which draws from the CHIME/FRB Catalogs. The framework combines labeled data (known repeaters and confidently classified non-repeaters) with unlabeled sources previously flagged as non-repeaters but exhibiting repeater-like characteristics. We employ uniform
manifold approximation and projection with a nearest-neighbor scheme to select potential candidates, followed by semi-supervised classification using five base
estimators, including random forest, support vector machine, logistic regression, AdaBoost, and Gradient boost. Each model is fine-tuned through cross-validation, and a voting strategy among the five models is employed to enhance robustness. All models achieve consistently high performance, identifying dispersion measure, peak frequency, and fluence as the most discriminative features. Repeaters tend to show lower dispersion measures, higher peak frequencies, and higher fluences than non-repeaters. We also identify a set of candidate repeaters, several of which are consistent with prior independent studies. Our approach can identify 36 additional repeater candidates that conventional methods may have missed. Finally, the results highlight dispersion measure as a key discriminator between repeaters and non-repeaters, revealing a tension between physical and instrumental origins-either environmental effects, if the two populations arise from distinct progenitors, or detection bias, as nearby sources are more easily observed.
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All authors N. Mankatwit, P. Thongkonsing, S. Loekkesee, P. Chainakun, W. Luangtip, S. Sanpa-arsa
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Apparent Phantom Crossing in Gauss-Bonnet Gravity
Shin'ichi Nojiri, Sergei D. Odintsov and V. K Oikonomou
The recent observations of the Dark Energy Spectroscopic Instrument (DESI) indicated the possibility that the dark energy equation of state parameter $w$ might change from $w<-1$ to $w>-1$ when the
redshift $z\sim 0.5$, which is called the inverse phantom crossing. In this paper, we investigate the possibility of the phantom crossing, and we construct realistic models realizing the crossing in the framework of the scalar–Einstein–Gauss-Bonnet
gravity and ghost-free $f(\mathcal{G})$
gravity. We also investigate the scenario of the apparent phantom crossing, where dark matter energy density decreases more slowly than usually expected, which might explain the DESI observations. In the scenarios developed, the energy conditions are not violated by any component of the
cosmic fluid. In the framework of the apparent phantom crossing, we also propose a new scenario, where the particle corresponding to the scalar field in the scalar–Einstein–Gauss-Bonnet
gravity is dark matter. The mass of the particle might increase due to the coupling with the Gauss-Bonnet invariant, which makes the decrease of the dark matter energy density slower. This last scenario may suggest that the inverse phantom crossing might be related to the transition from the decelerating expansion of the Universe to the accelerating expansion.
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Astrophysics of Galaxies
CLASSY XIV: The Nitrogen Exception – Multi-Phase Enrichment and Feedback in High-$z$ Analogs
Bethan L. James, Valentina Abril-Melgarejo, Karla Z. Arellano-Córdova et al. (+13 more)
We present a first-of-its-kind analysis of the metal content across two interstellar medium (ISM) phases in a sample of 31 local
star-forming
galaxies from the COS Legacy Archive Spectroscopic SurveY (CLASSY), selected as analogues of high-$z$ systems. Using co-spatial UV absorption and optical emission-line spectroscopy, we compare abundances of N, O, S, and Fe in the low-ionization (neutral) and high-ionization (ionized) gas, providing a multi-phase view of enrichment shortly after the current starburst and over longer timescales when ejecta from previous episodes have cooled and mixed. We find that O and S, produced predominantly in short-lived massive
stars, are well mixed between the two phases, with scatter reflecting local inhomogeneities. Fe, predominantly produced by Type Ia
supernovae on $\sim$1 Gyr timescales, is higher in the neutral gas, reflecting either delayed mixing of older Fe-enriched material or preferential depletion of Fe from the ionized phase through
dust formation in core-collapse
supernova ejecta. N exhibits the largest phase offset, with N/H$_{ion}$ systematically $\sim$0.7 dex higher than N/H$_{neu}$, and the magnitude of this offset correlates with
stellar mass,
metallicity,
star-formation rate, and most strongly with the ISM
outflow velocity. N/O ratios in the ionized phase rise rapidly within 3-6 Myr relative to the neutral gas, consistent with N enrichment dominated by Wolf-Rayet
stars rather than intermediate-mass AGB
stars on longer timescales. These results demonstrate that localized
stellar feedback,
outflows, and phase-dependent mixing collectively regulate the chemical
evolution of
star-forming
galaxies, providing key insight into the extreme N/O abundances recently observed in
galaxies at
cosmic dawn.
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All authors Bethan L. James, Valentina Abril-Melgarejo, Karla Z. Arellano-Córdova, Adarsh Ranjan, Kaelee S. Parker, Danielle A. Berg, Matilde Mingozzi, Alessandra Aloisi, John Chisholm, Timothy Heckman, Alaina Henry, Svea Hernandez, Kristen B. W. McQuinn, Xinfeng Xu, Chiaki Kobayashi, The CLASSY Collaboration
Instrumentation and Methods for Astrophysics
FIP-TOI: Fast Imaging Pipeline for Pulsar Localisation with a Transient-Oriented Radio Astronomical Imager
X. Li, K. Adamek, O. Bilaniuk et al. (+2 more)
Rapid localisation of
radio transients requires imaging pipelines that combine low latency, high sensitivity, and accurate transient positioning. Fast Imaging Pipeline (FIP) defines a (quasi)-real-time image-based transient detection pipeline for next-generation
radio telescopes such as the Square Kilometre Array (SKA). However, the current FIP within the SKA Science Data Processor (SDP) remains at an early stage, leaving substantial scope to improve its performance. To address this need, we develop FIP-TOI, which combines a novel Transient-Oriented Imager (TOI) with the transient detector FITrig. FIP-TOI is highly parallelised and GPU accelerated. In experiments, TOI improves signal-to-noise ratio (SNR) by at least 15 compared with WSClean and SKA-SDP imagers, while providing higher positional precision than WSClean snapshot imaging. On a 396 GB MeerKAT Measurement Set containing 1500 snapshots, FIP-TOI processes the data in 170-190 s on a single NVIDIA H100, corresponding to approximately 120 ms per snapshot, while using 714 MB of RAM and about two CPU cores. Testing on diverse
datasets — including fields with multiple faint transients, an on-and-off
pulsar, and a
pulsar exhibiting intensity changes — FIP-TOI demonstrates robust performance across all scenarios and achieves lower localisation errors than SKA-SDP-FIP.
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All authors X. Li, K. Adamek, O. Bilaniuk, V. Stolyarov, W. Armour
Astrophysics of Galaxies
A pan-galaxy study of synthetic giant molecular filaments: a turbulence-dominated life cycle
Zipeng Hu, Ke Wang, Mark R. Krumholz et al. (+1 more)
Recent surveys of the
Galactic plane have revealed dozens of
giant molecular filaments (GMFs), with lengths ranging from tens to hundreds of parsecs, yet their origins and life cycles remain debated. In this work, we analyze over 700 GMFs identified from synthetic CO emission maps of a high-resolution magnetohydrodynamic simulation of a Milky Way-like
galaxy, whose lengths range from $\sim 10$ pc to $\sim 300$ pc. We find that turbulent shock from
galactic shear and
stellar feedback are the primary drivers of GMF formation. Magnetized
turbulence dominates their internal dynamics, supporting the filaments against global collapse while simultaneously inducing fragmentation into dense clumps. This fragmentation follows the
turbulence-driven sausage instability model, rather than pure Jeans instability, and triggers efficient
star formation along the filaments. Cloud-cloud collisions are frequent, affecting more than $70\%$ of GMFs, and often disrupt or reshape their morphology. The typical filamentary lifetime is $t_{\text{fil}} \sim 14$ Myr, comparable to the crossing time of
giant molecular clouds (GMCs). The molecular gas half-life is $\sim 7$ Myr, similar to that of GMCs, indicating that GMFs are transient but dynamically important structures.
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All authors Zipeng Hu, Ke Wang, Mark R. Krumholz, Keyun Su
Astrophysics of Galaxies
Effects of helium sedimentation on late star formation in galaxy clusters
J. Racker and N. Padilla
We discuss how helium sedimentation in
galaxy clusters can affect the history of
star formation in the central cluster
galaxy. As helium sediments, the gas density in the inner regions of the cluster increases and there is also a non-trivial, radially dependent redistribution of the atomic
nuclei and electrons. As a result, the cooling rate in the center increases and this can enhance
star formation. On the other hand, there is a slow contraction of the intracluster gas, which may induce gravitational heating and therefore has an opposite effect on
star formation. In this work we present these effects and aim to estimate their relevance. For this we have performed a 1-dimensional numerical simulation of helium sedimentation and applied it to a simple semi-analytical model of
star formation. We find that for clusters with a
halo mass $M_{\rm halo} \lesssim 10^{14} M_{\rm sun}$, helium sedimentation effects on the
star formation rate are negligible, even under idealized conditions. In the intermediate range, $10^{14} M_{\rm sun} \lesssim M_{\rm halo} \lesssim 10^{15} M_{\rm sun}$, the effects are at most mild, below a factor ~ 2 in the isothermal model we consider, even for idealized conditions. For clusters with a
halo mass $M_{\rm halo} \gtrsim 10^{15} M_{\rm sun}$, helium sedimentation effects can potentially be very important and renew
star formation activity in the central
galaxy.
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