Earth and Planetary Astrophysics
JWST-TST DREAMS: The Nightside Emission and Chemistry of WASP-17b
Jacob Lustig-Yaeger, Kristin S. Sotzen, Kevin B. Stevenson et al. (+24 more)
Theoretical studies have suggested using planetary infrared excess (PIE) to detect and characterize the thermal emission of transiting and non-transiting
exoplanets, however the PIE technique requires empirical validation. Here we apply the PIE technique to a combination of JWST NIRSpec G395H transit and eclipse measurements of WASP-17b, a hot Jupiter orbiting an F-type
star, obtained consecutively (0.5 phase or 1.8 days apart) as part of the JWST-TST program to perform Deep Reconnaissance of
Exoplanet Atmospheres through Multi-instrument Spectroscopy (DREAMS). Using the in-eclipse measured
stellar spectrum to circumvent the need for ultra-precise
stellar models, we extract the first JWST nightside emission spectrum of WASP-17b using only transit and eclipse data thereby performing a controlled test of the PIE technique. From the WASP-17b nightside spectrum, we measure a nightside
equilibrium temperature of $1005 \pm 256$ K and find tentative evidence for nightside SO2 absorption ($\ln B = 1.45$, $2.3\sigma$). In context with the dayside, the temperature of the nightside is consistent with (1) previous eclipse mapping findings that suggest relatively inefficient day-night heat transport, and (2) a non-zero bond albedo of $0.42^{+0.06}_{-0.10}$. SO2 on the nightside, if confirmed, would represent the first direct evidence for transport-induced chemistry, matching previous model predictions, and opening a new door into the 3D nature of
giant exoplanets. Our results suggest that PIE is feasible with JWST/NIRSpec for two epochs separated in time by significantly less than the rotation period of the host
star.
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All authors Jacob Lustig-Yaeger, Kristin S. Sotzen, Kevin B. Stevenson, Shang-Min Tsai, Ryan C. Challener, Jayesh Goyal, Nikole K. Lewis, Dana R. Louie, L. C. Mayorga, Daniel Valentine, Hannah R. Wakeford, Lili Alderson, Natalie H. Allen, Thomas J. Fauchez, Ana Glidden, Amélie Gressier, Sarah M. Hörst, Jingcheng Huang, Zifan Lin, Avi M. Mandell, Elijah Mullens, Sarah Peacock, Edward W. Schwieterman, Jeff A. Valenti, C. Matt Mountain, Marshall Perrin, Roeland P. van der Marel
Astrophysics of Galaxies
PDRs4All XIX. The 6 to 9 $\mu$m region as a probe of PAH charge and size in the Orion Bar
Baria Khan, Samuel A. Daza Rodriguez, Els Peeters et al. (+24 more)
Infrared emission from polycyclic aromatic hydrocarbons (PAHs) play a major role in determining the charge balance of their host environments that include photo-dissociation regions (PDRs) in
galaxies, planetary nebulae, and rims of molecular clouds. We aim to investigate the distribution and sizes of charged PAHs across the key zones of the Orion Bar PDR. We employ JWST MIRI-MRS observations of the Orion Bar from the Early Release Science program ”PDRs4All” and synthetic images in the JWST MIRI filters. We investigate the spatial morphology of the AIBs at 6.2, 7.7, 8.6, and 11.0 $\mu$m that commonly trace PAH cations, and the neutral PAH-tracing 11.2 $\mu$m AIB, their (relative) correlations, and the relationship with existing empirical prescriptions for AIBs. The 6.2. 7.7, 8.6, 11.0, and 11.2 $\mu$m AIBs are similar in spatial morphology, on larger scales. Analyzing three-feature intensity correlations, two distinct groups emerge: the 8.6 and 11.0 $\mu$m vs. the 6.2 and 7.7 $\mu$m AIBs. We attribute these correlations to PAH size. The 6.2 and 7.7 $\mu$m AIBs trace cationic, medium-sized PAHs.
Quantum chemical calculations reveal that the 8.6 $\mu$m AIB is carried by large, compact, cationic PAHs, and the 11.0 $\mu$m AIB's correlation to it implies, so is this band. The 6.2/8.6 and 7.7/8.6 PAH band ratios thus probe PAH size. We conclude that the 6.2/11.2 AIB ratio is the most reliable proxy for charged PAHs, within the cohort. We outline JWST MIRI imaging prescriptions that serve as effective tracers of the PAH ionization fraction as traced. This study showcases the efficacy of the 6-9 $\mu$m AIBs to probe the charge state and size distribution of the emitting PAHs, offering insights into the physical conditions of their host environments. JWST MIRI photometry offers a viable alternative to IFU spectroscopy for characterizing this emission in extended objects.
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All authors Baria Khan, Samuel A. Daza Rodriguez, Els Peeters, Alexander G. G. M. Tielens, Takashi Onaka, Jan Cami, Bethany Schefter, Christiaan Boersma, Felipe Alarcón, Olivier Berné, Amélie Canin, Ryan Chown, Emmanuel Dartois, Javier R. Goicoechea, Emilie Habart, Olga Kannavou, Alexandros Maragkoudakis, Amit Pathak, Alessandra Ricca, Gaël Rouillé, Dinalva A. Sales, Ilane Schroetter, Ameek Sidhu, Boris Trahin, Dries Van De Putte, Yong Zhang, Henning Zettergren
Cosmology and Nongalactic Astrophysics
Nonlinear Evolution of the Matter Trispectrum with Primordial Parity Violation
Sha Azyzy, Drew Jamieson, Eiichiro Komatsu et al. (+1 more)
Parity-odd four-point correlation functions, or trispectra, of
cosmic matter density fields provide a unique probe of fundamental
symmetries in cosmology. Trispectra of
primordial matter density fluctuations produced in the early universe are modified by the subsequent nonlinear structure formation. In this paper, we compute the nonlinear
evolution of the parity-odd matter trispectrum to one-loop order, i.e., to third order in density fluctuations, within the framework of effective field theory of the large-scale structure of the universe. By analyzing the different terms in the perturbation series, we demonstrate the structure of infrared divergence cancellations, as required by the equivalence principle. We also derive the forms of the counterterms required to renormalize the ultraviolet divergences. Adopting a specific model for a
primordial parity-odd trispectrum, we numerically compute the leading-order effects of nonlinear gravitational
evolution and study its impact on baryonic acoustic oscillations within the signal. These calculations are essential for comparing the observed trispectra of nonlinear
cosmic density fields with theoretical expectations.
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All authors Sha Azyzy, Drew Jamieson, Eiichiro Komatsu, Toshiki Kurita
Earth and Planetary Astrophysics
On the Possibility of Melting Water Ice during the Recent Past of Mars: Application to the Formation of Gullies
Lucas Lange and Francois Forget
The formation of gullies on Mars has often been attributed to the melting of (sub)surface water ice. However, melting-based hypotheses generally overlook key processes: (1) sublimation cooling by latent heat absorption, (2) the non-stability of ice where melting conditions can be reached, and (3) the particular microclimates of gullied slopes. Using state-of-the-art
climate simulations, we reassess ice melting scenarios over the past four million years (obliquity <= 35{\deg}), beyond the estimated period of gully formation. We find that the melting of opaque water snow or ice at the surface of Mars is unlikely anywhere due to sublimation cooling, while (quasi-) stable subsurface ice is typically too deep to reach melting temperatures. We propose an alternative mechanism in which seasonal CO2 frost sublimation destabilizes the regolith and brings the underlying water ice close to the surface, allowing rapid heating. Even under these optimal conditions, melting requires unrealistic assumptions. Ice containing a small amount of
dust could melt via a solid-state greenhouse effect, but both its possibility and frequency in Mars' recent past remain uncertain.
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Astrophysics of Galaxies
Resolving Star Cluster Formation in Galaxy Simulations with Cosmic Ray Feedback
Brandon Sike, Mateusz Ruszkowski, Oleg Y. Gnedin et al. (+4 more)
Star clusters host the massive
stars responsible for feedback in
star-forming
galaxies.
Stellar feedback shapes the interstellar medium (ISM), affecting the formation of future
star clusters. To self-consistently capture the interplay between feedback and
star formation, a model must resolve the parsec-scale
star formation sites and the multiphase ISM. Additionally, the dynamical impact of
cosmic rays (CRs) on
star formation rates (SFRs) must also be considered. We present the first simulations of the formation of an ensemble of
star clusters with dynamically-coupled CRs, near-individual
star particles, and a feedback-regulated ISM. We analyze tallbox simulations performed using the CRISP model in the moving-mesh code AREPO. We apply varied implementations of CR transport under the theory of self-confinement. We find that CRs simultaneously reduce the SFR, the power law slope of the cluster mass function, and the cluster formation efficiency. Each simulation is compatible with observations, and CR feedback tends to move results along observed
star cluster relations. We see only modest changes in cluster radius and velocity dispersions, but significant differences in the virial parameters. Ultimately, the primary impact of CRs is to reduce SFRs. Lower SFRs imply fewer
supernovae, and consequently a lower turbulent energy budget for gas.
Star clusters formed in a CR-regulated ISM have lower velocity dispersions, and are therefore more bound under self-
gravity. The effective clustering of
supernovae is unchanged by CRs. Despite the idealized setup, the CRISP feedback model recovers many key aspects of
star cluster formation.
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All authors Brandon Sike, Mateusz Ruszkowski, Oleg Y. Gnedin, Yingtian Chen, Matthias Weber, Timon Thomas, Christoph Pfrommer
Cosmology and Nongalactic Astrophysics
Multiprobe constraints on early and late time dark energy
Alexander Reeves, Simone Ferraro, Andrina Nicola et al. (+1 more)
We perform a multiprobe analysis combining
cosmic microwave background (CMB) data from Planck and the Atacama Cosmology
Telescope (ACT), ACT CMB
lensing, and large-scale structure (LSS) measurements from the Dark Energy Spectroscopic Instrument (DESI), including DESI Legacy Imaging Survey (LS)
galaxies and
baryon acoustic oscillations (BAOs). We present the first $5\times2$pt analysis of ACT DR6
lensing, DESI LS, and Planck ISW. Within $\Lambda$CDM, this yields $S_8 = \sigma_8(\Omega_m/0.3)^{0.5} = 0.819 \pm 0.016$, in good agreement with primary CMB inferences and provides a sound-horizon-free Hubble constant constraint of $H_0 = 70.0 \pm 4.4$ km s$^{-1}$ Mpc$^{-1}$. Then, combining with CMB primary and BAO, we reconfirm a CMB-BAO discrepancy in the $\Omega_m$-$\frac{D_v}{r_d}$ plane, which is heightened when combining BAO with the $5\times2$pt data vector. We explore two dark-energy extensions that may reconcile this: an early-time modification, early dark energy (EDE), and late-time dynamical dark energy (DDE) parameterized by $w_0w_a$. For CMB primary+BAO+$5\times2$pt, we find a $3.3\sigma$ preference for DDE over $\Lambda$CDM, while EDE is modestly favoured at $2.3\sigma$. The models address different shortcomings of $\Lambda$CDM: DDE relaxes the
neutrino mass bound ($M_\nu<0.17$eV vs. $<0.050$eV under $\Lambda$CDM), making it compatible with
neutrino oscillation measurements, while EDE raises the Hubble constant to $H_0=70.5\pm1.2\,\mathrm{km\,s^{-1}\,Mpc^{-1}}$, easing the discrepancy with SH0ES. However, neither model resolves both issues simultaneously. Our analysis indicates that both DDE and EDE remain viable extensions of $\Lambda$CDM within current uncertainties and demonstrates the capacity of combined probes to place increasingly stringent constraints on cosmological parameters.
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All authors Alexander Reeves, Simone Ferraro, Andrina Nicola, Alexandre Refregier
Astrophysics of Galaxies
Mass loading of outflows from evolving Young Massive Clusters
C. J. K. Larkin, C. Hawcroft, J. Mackey et al. (+3 more)
Feedback from Young Massive Clusters (YMCs) is an important driver of
galaxy evolution. In the first few Myr, mechanical feedback is dominated by collective effects of the massive
stellar winds in the YMC. The mass-loss rates and terminal wind velocities of these
stars change by orders of magnitude over pre-SN timescales as the massive
stars evolve, and mass-loss rates of Cool Supergiant (CSG)
stars in particular are uncertain by a factor $\sim~20$ or more. In this work we perform a first study of the time
evolution of average cluster wind velocity $\bar{V}_{\mathrm{cl}}$ as a function of
stellar metallicity $Z$, assuming single
star evolution. We also check the validity of assuming Wolf-Rayet
stars dominate the feedback effects of a YMC, as often done when interpreting X-ray and $\gamma$-ray observations, and test how sensitive $\bar{V}_{\mathrm{cl}}$ is to current uncertainties in mass-loss rates. We use pySTARBURST99 to calculate integrated properties of YMCs for $Z$ in the range of $0.0004-0.02$, representing a range of environments from IZw18 to the
Galactic Centre. We find that $\bar{V}_{\mathrm{cl}}$ drops off rapidly for sub-LMC $Z$, and we recommend a value of $500-1000\,~\textrm{km~s}^{-1}$ be used in this regime. We show accounting only for WR
stars can overestimate $\bar{V}_{\mathrm{cl}}$ by $500-2000\,~\textrm{km~s}^{-1}$ at $Z \geq Z_\text{LMC}$. We also find that different RSG mass-loss assumptions can change the inferred $\bar{V}_{\mathrm{cl}}$ by $\sim1000\,~\textrm{km~s}^{-1}$, highlighting the need for improved observational constraints for RSGs in YMCs.
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All authors C. J. K. Larkin, C. Hawcroft, J. Mackey, R. R. Lefever, L. Härer, A. A. C. Sander
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Limits on the axion-photon coupling from Chandrayaan-2 observations
Tanmoy Kumar, N. P. S. Mithun, Subhendra Mohanty et al. (+3 more)
Axions and
axion-like particles (ALPs) have gained immense
attention in searches for beyond Standard Model (BSM) physics. Experiments searching for
axions leverage their predicted couplings to Standard Model (SM) particles to look for observable signals. Though weak, these couplings allow
axions to be produced abundantly in the interiors of
stars such as the Sun. Once created,
axions can escape the Sun and while passing through the
solar atmosphere, oscillate into
photons in the
magnetic field producing x-rays. For the first time, we used data from the observation of soft x-rays from the quiet Sun during the 2019-20
solar minimum by the
solar x-ray monitor (XSM), onboard India's Chandrayaan-2 lunar exploration mission, to constrain the coupling of
axions to
photons ($g_{a \gamma \gamma}$). Using the latest models of the
solar atmosphere to calculate the
magnetic field and
plasma frequency, we constrain $g_{a \gamma \gamma} \lesssim (0.50 - 2.26) \times 10^{-10}$ GeV$^{-1}$ at $95\%$ confidence level for
axion masses $m_a \lesssim 5 \times 10^{-4}$eV.
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All authors Tanmoy Kumar, N. P. S. Mithun, Subhendra Mohanty, Sourov Roy, B. S. Bharath Saiguhan, Santosh Vadawale
High Energy Astrophysical Phenomena
The gamma-ray emission from Radio Galaxies and their contribution to the Isotropic Gamma-Ray Background
A. Circiello, A. McDaniel, M. Di Mauro et al. (+6 more)
We evaluate the contribution to the Isotropic Gamma-Ray Background (IGRB) coming from
Radio Galaxies (RGs), the subclass of
radio-loud Active
Galactic Nuclei (AGN) with the highest misalignment from the line of sight (l.o.s.). Since only a small number of RGs are detected in gamma rays compared to the largest known
radio population, the correlation between
radio and gamma-ray emission serves as a crucial tool to characterize the gamma-ray properties of these sources. We analyse the population of RGs using two samples. The first sample contains 26 sources individually detected by the Large Area
Telescope (LAT) on board the
Fermi Gamma-ray Space
Telescope at gamma rays. The second sample contains 210 RGs for which the gamma-ray emission is not significantly detected by the LAT. We use a stacking analysis to characterize the average properties of the gamma-ray emission of the two samples, separately at first and then combined. We then evaluate the correlation between their gamma-ray emission and the emission from their
radio core at 5 GHz, and we use it to determine their contribution to the IGRB. Due to the limited number of RGs detected at the gamma-rays, information on the gamma-ray luminosity function is limited. The correlation between the gamma-ray emission and the emission of the
radio core allows us to characterize it starting from the luminosity function of the
radio cores, which is modeled with greater accuracy due to the larger number of sources detected at these frequencies. We find that the diffuse emission as extrapolated from the properties of the subthreshold RGs is lower than the one inferred from detected RGs, showing that the contribution of the population of RGs to the IGRB is lower than the previous estimates and it is around the 30% level of the IGRB intensity.
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All authors A. Circiello, A. McDaniel, M. Di Mauro, C. Karwin, N. Khatiya, M. Ajello, F. Donato, D. Hartmann, A. Strong
Earth and Planetary Astrophysics
The Influence of Central Body Tides on Catastrophic Disruptions of Close-in Planetary Satellites
Harrison Agrusa and Patrick Michel
We model the outcomes of catastrophic disruptions on small,
gravity-dominated natural satellites, accounting for the
tidal potential of the central body, which is neglected in classical disruption scaling laws. We introduce the concept of $Q^\star_\text{TD}$, the specific energy required to disperse half of the total mass involved in a collision, accounting for the
tidal potential of a central body. We derive a simple scaling relation for $Q^\star_\text{TD}$ and demonstrate that for close-in planetary or asteroidal satellites, the tides from the central body can significantly reduce their catastrophic disruption threshold. We show that many satellites in the
Solar System are in such a regime, where their disruption threshold should be much lower than that predicted by classical scaling laws which neglect
tidal effects. Some notable examples include Mars' Phobos, Jupiter's Metis and Adrastea, Saturn's ring moons, Uranus' Ophelia, and Neptune's Naiad and Thalassa, among others. We argue that traditional impact scaling laws should be modified to account for tides when modeling the formation and
evolution of these close-in satellites. Our derivation for $Q^\star_\text{TD}$ can easily be used in existing $N$-body and collisional
evolution codes.
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Solar and Stellar Astrophysics
The influence of rotation and metallicity on the explodability of massive stars
Renyu Luo, Chunhua Zhu, Guoliang Lü et al. (+4 more)
During the late stages of massive
stellar evolution, failed
supernovae (FSN) may form through core-collapse processes. The traditional evaluation criterion $\xi_{2.5}$ $=$ 0.45, primarily established using non-rotating progenitor models, suffers from significant inaccuracies when applied to rotating pre-
supernova systems. The effects of
metallicity and rotation on the explodability landscapes of massive
stars lack robust quantification. We aim to investigate how rotation and
metallicity influence the explodability of massive
stars. We investigate how rotation and
metallicity affect
stellar explodability using MESA simulations with initial rotational velocities of $0$, $300$, and $600~\mathrm{km,s^{-1}}$ at three
metallicities ($Z_{\odot}$, $1/10,Z_{\odot}$, $1/50,Z_{\odot}$). Core-collapse phases are simulated with GR1D to determine critical heating efficiencies. Our results yield revised $\xi_{2.5}$ criteria: 0.45 for non-rotating models; 0.48 for $300~\mathrm{km,s^{-1}}$; 0.47 for $600~\mathrm{km,s^{-1}}$ at
solar metallicity; and 0.59 for low-
metallicity models. Chemically homogeneous
evolution in rapidly rotating low-
metallicity stars significantly raises the compactness limit for successful explosions and narrows the zero-age main sequence mass range for failed
supernovae. Rotation substantially affects the explodability of low-
metallicity massive
stars, underscoring the importance of incorporating rotational effects in models of core-collapse
supernova progenitors.
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All authors Renyu Luo, Chunhua Zhu, Guoliang Lü, Helei Liu, Sufen Guo, Lei Li, Zhuowen Li
High Energy Astrophysical Phenomena
Hunting Very High-Energy ($>$100 GeV) Emitting High-Synchrotron Peaked Blazars
Sushmita Agarwal and Vaidehi S. Paliya
Very-high energy (VHE; $>$100 GeV) $\gamma$-ray emission originates via some of the most extreme particle acceleration processes in the universe. Considering beamed active
galactic nuclei, i.e., blazars, only a small fraction, mainly high synchrotron peak BL Lacs, have been detected in the VHE band with the ground-based Cherenkov
telescopes. We utilized $\sim$16 years of
Fermi-Large Area
Telescope (LAT) observations in the 0.1$-$2 TeV energy range to systematically search for potential VHE emitters in a sample of high synchrotron peaked ($\nu^{\rm peak}_{\rm syn}>10^{15}$ Hz) BL Lac sources. We identified, for the first time, 92 VHE emitting blazars at $\geq 5\sigma$ confidence level. A significant VHE emission was also detected from 52 sources previously reported as VHE blazars. Comparing with the general blazar population, these VHE emitting blazars are found to be located at low
redshifts (mean $z=0.2 \pm 0.1$) and exhibit bright synchrotron emission ($\log F^{\rm peak}_{\rm syn}=-11.2 \pm 0.4$, in erg cm$^{-2}$ s$^{-1}$). We also investigated the coincidence of VHE
photon arrivals with the source activity states and found that
Fermi-LAT has detected VHE
photons during both quiescent and elevated activity epochs. These VHE emitting blazars represent promising targets for current and next-generation ground-based Cherenkov
telescopes, and provide powerful laboratories for probing particle acceleration in relativistic jets, testing multi-messenger connections, and constraining extragalactic background light models.
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Solar and Stellar Astrophysics
The inertial dip as a window on the convective core dynamics
Lucas Barrault, Lisa Bugnet, Stéphane Mathis et al. (+1 more)
Gamma Dor
stars are ideal targets for studies of the innermost dynamical properties of
stars, due to their rich frequency spectrum of gravito-inertial modes propagating in the radiative envelope. Recent studies found that these modes could couple at the core-to-envelope interface with pure inertial modes in their sub-inertial regime, forming the so-called inertial dip in the period-spacing pattern of these
stars. The inertial dip, as formed by core modes, stands out as a unique probe of core properties. We aim in this work to explore the effect of core magnetism on its structure, property of key relevance in modern
stellar physics. We describe the outlines of our model and the geometry of the considered field. We give the coupling equation and the variation of the dip shape and location with increasing
magnetic contrast between the core and the envelope. We compare our findings to the ones obtained in a hydrodynamical, differentially-rotating case. We show hints at potentially lifting the degeneracy between the signatures of core-to-envelope differential rotation and core
magnetic fields. Together, these two cases can be considered as an exploration of different
magnetic regimes potentially reached in the core of gamma Dor
stars.
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All authors Lucas Barrault, Lisa Bugnet, Stéphane Mathis, Joey S.G. Mombarg
Solar and Stellar Astrophysics
Dormant black hole candidates from Gaia DR3 summary diagnostics
Johanna Müller-Horn, Hans-Walter Rix, Kareem El-Badry et al. (+4 more)
We present a rigorous identification of candidates for dormant black holes (BHs) and
neutron stars (NSs) in binaries using summary statistics from
Gaia DR3, rather than full orbital solutions. Although
Gaia astrometric orbits have already revealed a small sample of compact object binaries, many systems remain undetected due to stringent quality cuts imposed on the published orbits. Using a forward-modelling framework that simulates
Gaia observables, in particular the re-normalised unit weight error (ruwe) and radial velocity (RV) scatter, we infer posterior distributions for companion mass and orbital period via MCMC sampling, marginalising over nuisance orbital parameters. We validate our approach by comparing the predicted masses and periods against full orbit solutions from DR3, and by successfully recovering known compact object binaries as promising candidates. The method is best suited for systems with red
giant primaries, which have more reliable
Gaia RV scatter and a light centroid more likely dominated by one component, compared to main-sequence
stars, and they are less likely to be triples with short-period inner binaries, which produce confounding signatures. We applied the method to three million
giants and identify 389 systems with best-fit companion masses $\gtrsim 3\,M_\odot$. Recovery simulations suggest our selection method is substantially more sensitive than the DR3 non-single-
star catalogue, particularly for binaries with periods below 1 year and above $\sim 6$ years. These candidates represent promising targets for spectroscopic follow-up and
Gaia DR4 analysis to confirm the presence of compact objects. Candidate main-sequence
stars with massive companions face a larger set of confounding effects. Therefore, we present an analogous catalogue of 279 additional main-sequence candidates only as an appendix.
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All authors Johanna Müller-Horn, Hans-Walter Rix, Kareem El-Badry, Ben Pennell, Matthew Green, Jiadong Li, Rhys Seeburger
Solar and Stellar Astrophysics
Near-continuous tracking of solar active region NOAA 13664 over three solar rotations
I. Kontogiannis, Y. Zhu, K. Barczynski et al. (+6 more)
Magnetic flux emergence and decay in the Sun span from days to months. However, their tracking is typically limited to about half a
solar rotation when relying on single-vantage-point observations. Combining observations from both the Earth-facing and far side of the Sun, we monitored the
magnetic and coronal
evolution and characterised the non-potentiality of one of the most complex and eruptive regions of the past two decades, over more than three full
solar rotations. We used photospheric magnetograms and EUV filtergrams from the
Solar Orbiter and the
Solar Dynamics Observatory along with
flare detections from the GOES and the STIX instrument on board the
Solar Orbiter. All images were deprojected into a common coordinate system and merged into a unified
dataset. We tracked the
evolution of
magnetic flux and EUV emission and computed
magnetic field parameters from the line-of-sight magnetograms to quantify the region's non-potentiality. We identified the region's initial emergence and followed its
evolution through to its decay. The region developed through successive flux emergence episodes over a period of 20 days, reached its peak complexity one month after the first emergence, and gradually decayed over the subsequent two months. Unlike many complex regions, it consistently maintained high levels of non-potentiality for most of its lifetime, sustaining equally strong flaring activity. The derived time series of non-potentiality parameters, the first of their kind, far exceeded the typical 14-day window imposed by
solar rotation and were remarkably consistent, exhibiting strong correlation with the flaring activity of the region. Multi-vantage-point observations can significantly improve our understanding of how
magnetic flux emerges, evolves, and drives
solar activity, beyond the two-week limit imposed by
solar rotation on observations along the Sun-Earth line.
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All authors I. Kontogiannis, Y. Zhu, K. Barczynski, M. Z. Stiefel, H. Collier, J. McKevitt, J.S. Castellanos Durán, S. Berdyugina, L.K. Harra
Cosmology and Nongalactic Astrophysics
Stochastic Gravitational Waves from Modulated Reheating
Michele Benaco, Dimitrios Karamitros, Sami Nurmi et al. (+1 more)
We investigate scalar-induced
stochastic gravitational waves from adiabatic
curvature perturbations sourced by a spectator field via the modulated reheating mechanism. We consider a spectator scalar with
Higgs-like couplings and inflaton decay via shift symmetric dimension-five operators. The spectator is assumed to be in the Sitter
vacuum and it sources blue-tilted, strongly non-Gaussian
curvature perturbations which can dominate the spectrum on small scales $k \gg \rm{Mpc}^{-1}$. We find that the setup could generate a gravitational wave signal testable by surveys like BBO and DECIGO but only for large coupling values not expected in low-energy particle physics setups that can be perturbatively extrapolated up to the inflationary scale.
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All authors Michele Benaco, Dimitrios Karamitros, Sami Nurmi, Kimmo Tuominen
Earth and Planetary Astrophysics
Flow Regimes in Hot Jupiter Atmospheres: Insights from Anelastic Models
W. Dietrich and J. Wicht
Hot Jupiters are Jupiter-sized
exoplanets with close-in orbits, characterized by extreme day-night temperature contrasts due to synchronous rotation. These
planets offer unique observational opportunities through transit photometry, transmission spectroscopy, and infrared (IR) phase curve analysis, which reveal information about heat redistribution and atmospheric dynamics. Complementary to common generalized circulation models (GCMs), we introduce a more comprehensive approach using the anelastic fluid equations that fully capture the three-dimensional nature of the emerging non-linear flows. We identify various non-linear flow regimes and analyze the heat distribution when irradiation and thermal advection reach
equilibrium. Eastward zonal winds can reach velocities comparable to the planetary rotation (up to several kilometers per second), while slower radial flows, though less prominent, contribute significantly to heat advection and can cause both eastward and westward hotspot shifts. The efficiency of day-to-night heat redistribution and the positioning of brightness maxima are shown to depend strongly on pressure and the interplay of advective and radiative processes. These findings improve our understanding of the diversity observed in the IR phase curves and suggest a non-
magnetic mechanism for retrograde hotspot shifts. By extending the scope of traditional GCM models, our work demonstrates the usefulness of anelastic models in capturing the complex, multidimensional dynamics of irradiated exoplanetary atmospheres.
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Cosmology and Nongalactic Astrophysics
Transverse Velocities in Real-Time Cosmology: Position Drift in Relativistic N-Body Simulations
Alexander Oestreicher, Chris Clarkson, Julian Adamek et al. (+1 more)
The era of real-time cosmology has begun. It is now possible to directly measure the apparent drift of high-
redshift astronomical sources across the sky $\textit{in real time}$. This so-called $\textit{position drift}$ provides a valuable probe of the peculiar velocity field and
cosmic structure formation by giving direct access to the transverse velocity, which is notoriously difficult to measure and is typically inferred statistically from the density field in a model-dependent way. To fully exploit this new window into the Universe, it is essential to understand how cosmological structures affect position drift measurements. Here we present the first position drift study based on the general relativistic N-body simulation code $\texttt{gevolution}$. We calculate the position drift directly from the past light cone for ten different observers and compare the results to predictions from linear perturbation theory. At linear order, the position drift is directly proportional to the transverse velocity on the sky. This linear approximation reproduces our non-linear simulation results to within about 5%. We calculate power spectra for the position drift, splitting the signal into an E- and B-mode and compare the former to linear expectations, finding good agreement. The B-mode is suppressed on linear scales, but has similar amplitude as the E-mode on non-linear scales. We further demonstrate that light-cone inhomogeneities induce biases in the dipole of the drift, introducing
redshift dependence of both the amplitude and direction. Although our analysis is not yet sufficient for a firm conclusion, our results suggest that these effects alone cannot explain the possible
redshift-dependent dipole in
Gaia DR3 data reported in the literature.
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All authors Alexander Oestreicher, Chris Clarkson, Julian Adamek, Sofie Marie Koksbang
Solar and Stellar Astrophysics
Kinetic collisionless model of the solar transition region and corona with spatially intermittent heating
Luca Barbieri and Pascal Démoulin
We develop a three-dimensional kinetic model of the
solar transition region and corona in which the
plasma above the chromosphere is collisionless and embedded in a uniform
magnetic field. Heating occurs intermittently at discrete locations on the chromospheric surface, modeled through a surface coarse-graining procedure that produces non-thermal boundary conditions for the Vlasov equation. The resulting stationary distribution functions generate suprathermal particle populations and naturally lead to a temperature inversion via gravitational filtering, without any local coronal heating. The model reproduces realistic temperature and density profiles with a thin transition region and a hot corona, consistent with
solar observations. These results demonstrate that the spatial intermittency of heating at the chromospheric interface is sufficient to account for the formation of the transition region and the high-temperature corona.
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Astrophysics of Galaxies
Magnetic Fields in the Bones of the Milky Way
Ian W. Stephens, Simon Coude, Philip C. Myers et al. (+20 more)
Stars primarily form in
galactic spiral arms within dense, filamentary molecular clouds. The largest and most elongated of these molecular clouds are referred to as “bones," which are massive, velocity-coherent filaments (lengths ~20 to >100 pc, widths ~1-2 pc) that run approximately parallel and in close proximity to the
Galactic plane. While these bones have been generally well characterized, the importance and structure of their
magnetic fields (B-fields) remain largely unconstrained. Through the SOFIA Legacy program FIELDMAPS, we mapped the B-fields of 10 bones in the Milky Way. We found that their B-fields are varied, with no single preferred
alignment along the entire spine of the bones. At higher column densities, the spines of the bones are more likely to align perpendicularly to the B-fields, although this is not ubiquitous, and the
alignment shows no strong correlation with the locations of identified young
stellar objects. We estimated the B-field strengths across the bones and found them to be ~30-150 $\mu$G at pc scales. Despite the generally low virial parameters, the B-fields are strong compared to the local
gravity, suggesting that B-fields play a significant role in resisting global collapse. Moreover, the B-fields may slow and guide gas flow during dissipation. Recent
star formation within the bones may be due to high-density pockets at smaller scales, which could have formed before or simultaneously with the bones.
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All authors Ian W. Stephens, Simon Coude, Philip C. Myers, Catherine Zucker, James M. Jackson, B-G Andersson, Rowan Smith, Archana Soam, Patricio Sanhueza, Taylor Hogge, Howard A. Smith, Giles Novak, Sarah Sadavoy, Thushara Pillai, Zhi-Yun Li, Leslie W. Looney, Koji Sugitani, Andres E. Guzman, Alyssa Goodman, Takayoshi Kusune, Miaomiao Zhang, Nicole Karnath, Jessy Marin
Solar and Stellar Astrophysics · Cross-listed from physics.ins-det
Low-energy Cross Section Measurements of ${}^{\mathsf{12}}\mathsf{C}(\mathsf{p},\gamma)$ Deep Underground at LUNA
Jakub Skowronski and Axel Boeltzig
The ${}^{\mathsf{12}}\mathsf{C}(\mathsf{p},\gamma)$ reaction cross section is currently under investigation in the low-background environment of the Laboratory for Underground
Nuclear Astrophysics (LUNA). It is being studied using different types of solid targets, and employing two complementary detection techniques: HPGe spectroscopy and activation counting. To reduce systematic uncertainties, targets have been accurately characterized and their degradation under the intense beam of the LUNA-400 accelerator monitored. We present the experimental techniques and the corresponding analyses used to extract the reaction cross section.
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Solar and Stellar Astrophysics
Three-dimensional Reconstruction and Propagation of an Asymmetric Flux-rope Coronal Mass Ejection
Philippe Lamy, Yannick Boursier, Jean Loirat et al. (+1 more)
We report on the characterization of a coronal mass ejection (CME) observed on 22 October 2003 by the LASCO-C2 and C3 coronagraphs over a time interval of 6 hours. This CME clearly appears as an asymmetric flux-rope in self-similar expansion and in spite of having a single vantage point, this relatively simple morphology and the geometry of the observations allow us to reconstruct its shape and its trajectory. The images are first processed in order to remove most of the background or foreground coronal structures (essentially streamers) which are superimposed on the CME. The analysis is based on forward modeling of an asymmetric structure where the
plasma is homogeneously distributed in a thin shell and synthetic images are calculated from Thomson scattering by the electrons. They are best fitted to the images to determine the exact shape of the flux rope, and to track its
evolution characterized by a radial propagation in self-similar expansion. The analysis supports the forward propagation (over the backward one) characterized by constant accelerations of 76 and 46 m/sec^2 for the front and rear parts of the CME, respectively. The respective velocities at 20 Rsun reach 2000 and 1100 km/s, and its mass unbiased by projection effects is estimated at 1.7x10^16 g. Altogether, these are quite exceptionally large values among CMEs and imply a very energetic event. No erupting event could be identified at or near the calculated initial location of the CME. It lies 25{\deg} west of the active region NOAA 10484, the site of contemporary, violent, and recurrent
solar eruptions (the “Halloween event”) and a putative connection would require a strong deflection over a very short path. Therefore, the origin of this CME remains unclear.
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All authors Philippe Lamy, Yannick Boursier, Jean Loirat, Andrei Zhukov
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Pulsar timing array analysis in a Legendre polynomial basis
Bruce Allen, Arian L. von Blanckenburg and Ken D. Olum
We use Legendre
polynomials, previously employed in this context by Lee et al., van Haasteren and Levin, and Pitrou and Cusin, to model signals in
pulsar timing arrays. These replace the (
Fourier mode) basis of trigonometric functions normally used for data analysis. The Legendre basis makes it simpler to incorporate
pulsar modeling effects, which remove constant-, linear-, and quadratic-in-time terms from
pulsar timing residuals. In the Legendre basis, this zeroes the amplitudes of the the first three Legendre
polynomials. We use this basis to construct an optimal quadratic cross-correlation
estimator $\widehat{\mu}$ of the Hellings and Downs (HD) correlation and compute its variance $\sigma^2_{\widehat{\mu}}$ in the way described by Allen and Romano. Remarkably, if the gravitational-wave background (GWB) and
pulsar noise power spectra are (sums of) power laws in frequency, then in this basis one obtains analytic closed forms for many quantities of interest.
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Astrophysics of Galaxies
Accretion, Jets, and Recoil in a Merging Supermassive Black Hole Binary: A Prompt Electromagnetic Postmerger Counterpart for LISA
Maria Chiara de Simone, Manuela Campanelli, Lorenzo Ennoggi et al. (+2 more)
We report the first three-dimensional general relativistic magnetohydrodynamic simulation to follow, self-consistently in a dynamical spacetime, the magnetized gas around a misaligned-
spin supermassive binary black hole, from late inspiral through merger to the gravitational-wave
recoil of the remnant. The equal-mass binary, in a $\textit{hang-up kick}$ configuration, is embedded in an equilibrated circumbinary disk (CBD), relaxed for 165 binary orbits before we evolve the final $\sim\!40$ orbits. During the inspiral, each black hole hosts a strongly warped minidisk whose jet follows the local
spin axis near the horizon before aligning with the binary's angular momentum farther out. The merger imparts a
recoil of $\simeq\!1032$ $km\,s$$^{-1}$ to the remnant, which nonetheless retains its gravitationally bound CBD, and the relaunched jet preserves its pre-merger orientation. The bolometric luminosity brightens by a factor $\sim\!2.2$, powered by merger-driven shocks concentrated within $r \lesssim 15\,M$, and the enhancement persists through the
recoil. We identify a distinctive postmerger electromagnetic signature: magnetized structures, generated at coalescence, drive correlated quasi-periodic modulations of the horizon
magnetic flux, the Poynting flux, and the thermal output, decoupled from the
accretion rate. The postmerger radiative efficiency $L_{\rm EM}/\dot{M}c^2$ rises by a factor $\simeq 2.6$ at nearly constant
accretion rate, showing that this emission is powered by the merger rather than
accretion. The transient turns on within minutes and lasts at least several hours for a $10^6 \ M_{\odot}$ LISA source, establishing recoiling remnants as
prompt postmerger counterparts to massive black hole mergers and a first-principles framework for interpreting candidates such as 3C186.
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All authors Maria Chiara de Simone, Manuela Campanelli, Lorenzo Ennoggi, Carlos O. Lousto, Yosef Zlochower
Solar and Stellar Astrophysics
Exploring Complexity Measures for Analysis of Solar Wind Structures and Streams
Venla Koikkalainen, Emilia Kilpua, Simon Good et al. (+1 more)
In this paper we use statistical complexity and information theory metrics to study structure within
solar wind time series. We explore this using
entropy-complexity and information planes, where the measure for
entropy is formed using either permutation
entropy or the degree distribution of a horizontal visibility graph (HVG). The
entropy is then compared to the Jensen complexity (Jensen-Shannon complexity plane) and Fisher information measure (Fisher-Shannon information plane), formed both from permutations and the HVG approach. Additionally we characterise the
solar wind time series by studying the properties of the HVG degree distribution. Four types of
solar wind intervals have been analysed, namely fast streams, slow streams,
magnetic clouds and sheath regions, all of which have distinct origins and interplanetary characteristics. Our results show that, overall, different metrics give similar results but Fisher-Shannon, which gives a more local measure of complexity, leads to a larger spread of values in the
entropy-complexity plane.
Magnetic cloud intervals stood out in all approaches, in particular when analysing the
magnetic field magnitude. Differences between
solar wind types (except for
magnetic clouds) were typically more distinct for larger time lags, suggesting universality in fluctuations for small scales. The fluctuations within the
solar wind time series were generally found to be
stochastic, in agreement with previous studies. The use of information theory tools in the analysis of
solar wind time series can help to identify structures and provide insight into their origin and formation.
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All authors Venla Koikkalainen, Emilia Kilpua, Simon Good, Adnane Osmane
Solar and Stellar Astrophysics
An in-depth study of brown dwarfs with TESS
F. Marcadon and A. Prša
The existence of a deficit of brown
dwarfs (BDs) in close orbit around main-sequence
stars is one of the most intriguing questions in
stellar physics. This so-called BD desert may result from the transition between two different dominant formation processes occurring for different mass regimes. While the BD mass derived from radial-velocity measurements helps confirm the nature of the analyzed objects, the BD radius obtained from transits is important to better constrain the BD age, as BDs are believed to contract with age. Such objects with well-constrained parameters, although in small number, are of
prime interest for deeper investigations of BD structure and chemical composition. The present document aims at presenting the first results of a search for BD transits among a sample of approximately 3300 host
star candidates observed by the Transiting
Exoplanet Survey Satellite during Cycle 6.
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Astrophysics of Galaxies
The effect of extended radio emission on SMBH accretion rate estimates
Stergios Amarantidis, Duncan Farrah, Nick Seymour et al. (+5 more)
Accretion rates in
radio galaxies are typically estimated from optical and total
radio flux measurements, incorporating emission from the core, jets, and lobes. These estimates can be used to investigate the link between observed Active
Galactic Nuclei (AGN) emission properties and the underlying
accretion physics of their Super-Massive Black Holes (SMBHs). However, while optical and core
radio emission trace the ongoing
accretion episode, extended jet and lobe structures may result from past AGN activity. Therefore,
accretion rates inferred from spatially unresolved
radio observations may be systematically overestimated, a bias whose prevalence and extent have yet to be thoroughly explored. In this study, using a sample of 121 local
radio-loud
galaxies with spatially resolved
radio components, we assess this effect by estimating their Eddington-scaled
accretion rates ($\lambda$) using both the common methodology which considers total
radio fluxes and a simple but novel approach that treats core and extended emission as signatures of distinct
accretion phases. Our results show that the former method systematically overestimates the $\lambda$ by a factor of $\sim 3$, affecting the
accretion mode classification in approximately $11\%$ of sources. This discrepancy appears to correlate with
radio size, with the most extended
galaxies indicating a transition in
accretion disk mode. Such a bias could affect AGN classification in unresolved high-
redshift radio surveys. Our results motivate re-examining
accretion rate calculations from AGN
radio surveys and align with the AGN unification model for
radio galaxies, revealing a clearer link between
accretion disk physics and optical spectral properties.
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All authors Stergios Amarantidis, Duncan Farrah, Nick Seymour, Mark Lacy, Iris Breda, Bodo Ziegler, Olmo Piana, Miguel Sánchez-Portal
Earth and Planetary Astrophysics
Physical Characterization of Asteroid (16583) Oersted Combining Stellar Occultation and Photometric Data
Josef Hanuš, Marco Delbo, Petr Pokorný et al. (+2 more)
We report a successful observation of a
stellar occultation by asteroid (16583) Oersted, enabling a detailed physical characterization of its shape,
spin state, and surface properties. Our goal is to determine the physical parameters of Oersted by combining multi-chord occultation timing, sparse optical photometry, and thermal infrared observations. Such asteroids (size$\sim$20 km) are rarely modeled in this detail due to observational limitations, making Oersted a valuable case study. We applied convex lightcurve inversion to sparse photometric data to derive an initial shape and
spin state. This model was then refined and scaled using non-convex shape modeling with the ADAM
algorithm, incorporating constraints from the occultation chord profile. Thermophysical modeling based on WISE thermal infrared fluxes was used to determine the asteroid's effective diameter,
geometric albedo, and thermal inertia. The non-convex shape model reveals localized surface concavities and provides a size estimate consistent with radiometric measurements. The derived thermal inertia is typical for asteroids of comparable size. This work demonstrates the effectiveness of combining
stellar occultations, photometry, and thermal infrared data for asteroid modeling and highlights the valuable contributions of citizen scientists, who played a key role in capturing the occultation and constraining the asteroid's profile.
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All authors Josef Hanuš, Marco Delbo, Petr Pokorný, Franck Marchis, Thomas M. Esposito
Solar and Stellar Astrophysics
An interferometric mid-infrared study of the eruptive star binary Z CMa with MATISSE/VLTI. I. Imaging the protoplanetary disks during the 2023 outburst
F. Lykou, J. Varga, F. Cruz-Saénz de Miera et al. (+14 more)
The mid-infrared (MIR) emitting regions of the individual protoplanetary disks in the binary system Z CMa are resolved by MATISSE/VLTI. The observations were obtained during a serendipitous large outburst of the HBe
star that lasted more than 100 days, while the FUor companion is presumed to be in quiescence. The size of the MIR-emitting disk region of the more massive HBe
star increases toward longer wavelengths from $<14$ mas at 3.5$\mu m$ to $\ll 50$ mas at 11.5$\mu m$ . The lack of substructures in the HBe disk might suggest that it is a continuous disk; however, this could be due to observational constraints. We also note a radial variation of the silicate absorption feature over the disk, where the optical depth increases inwards of $<$40~au radii. This contradicts the scenario of a carved, dusty cocoon surrounding the HBe
star. In the case of the less massive FUor companion, the MIR-emitting region is much smaller with an angular size $\leq$15 mas (or else a physical radius $<9$ au) in all bands, suggesting a compact disk. Both disks are aligned within uncertainties, and their orientation agrees with that of the known jets. Furthermore, MATISSE data place the binary's separation at $117.88 \pm 0.73$ mas and a position angle of $139.16^o\,\pm\,0.29^o$ east of north. Our estimates for the orbital elements gave an eccentric orbit ($e\sim0.17$) with a moderate inclination ($i\sim 66$\degr). The derived total mass is $M_{\rm total} = 16.4^{+2.1}_{-2.3}$ M$_\odot$, while the period is approximately 950 years. Our MATISSE imaging of the Herbig disk during outburst indicates a temperature gradient for the disk, while imaging of the FUor companion's disk corroborates previous studies showing that FUor disks are rather compact in the MIR. We cannot infer any misalignment between the MATISSE results and earlier ALMA/JVLA data, nor can we infer any influence from the alleged flyby event.
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All authors F. Lykou, J. Varga, F. Cruz-Saénz de Miera, P. Ábrahám, Á. Kóspál, B. Lopez, T. Henning, S. Wolf, G. Weigelt, F. Millour, M. Hogerheijde, L. Chen, T. Ratzka, W. Danchi, P. Boley, J.-C. Augereau, P. Priolet
Solar and Stellar Astrophysics
Accessing the fine temporal scale of EUV brightenings and their quasi-periodic pulsations: 1 second cadence observations by Solar Orbiter/EUI
Daye Lim, Tom Van Doorsselaere, Nancy Narang et al. (+7 more)
Small scale extreme ultraviolet (EUV) transient brightenings are observationally abundant and critically important to investigate. Determining whether they share the same physical mechanisms as larger scale
flares would have significant implications for the coronal heating problem. A recent study has revealed that quasi periodic pulsations (QPPs), a common feature in both
solar and
stellar flares, may also be present in EUV brightenings in the quiet Sun (QS). We aim to characterise the properties of EUV brightenings and their associated QPPs in both QS and active regions (ARs) using unprecedented 1 s cadence observations from
Solar Orbiter/Extreme Ultraviolet Imager (EUI). We applied an automated detection
algorithm to analyse statistical properties of EUV brightenings. QPPs were identified using complementary techniques optimised for both stationary and non stationary signals, including a
Fourier based method, ensemble empirical mode decomposition, and wavelet analysis. Over 500000 and 300000 brightenings were detected in ARs and QS regions, respectively. Brightenings with lifetimes shorter than 3 s were detected, demonstrating the importance of high temporal resolution. QPP periods span from 5 to over 500 s and show similar distributions between AR and QS. We found a consistent power law scaling, with a weak correlation and a large spread, between QPP period and lifetime in EUV brightenings,
solar, and
stellar flares. The results support the interpretation that EUV brightenings may represent a small scale manifestation of the same physical mechanisms driving larger
solar and
stellar flares. Furthermore, the similarity in the statistical properties of EUV brightenings and their associated QPPs between AR and QS regions suggests that the underlying generation mechanisms may not strongly depend on the large scale
magnetic environment.
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All authors Daye Lim, Tom Van Doorsselaere, Nancy Narang, Laura A. Hayes, Emil Kraaikamp, Aadish Joshi, Konstantina Loumou, Cis Verbeeck, David Berghmans, Krzysztof Barczynski