Cosmology and Nongalactic Astrophysics
Evading the CMB $\mu$-distortion bound on Supermassive Primordial Black Hole seeds with Non-Gaussian tails
Sanket Dave, Sheng-Feng Yan, Amara Ilyas et al. (+1 more)
Supermassive black holes (SMBHs) powering
quasars at $z \gtrsim 6$ are difficult to grow from
stellar mass remnants, motivating seeds from
primordial black holes (PBHs) with masses $10^5-10^7 M_{\odot}$. This range is constrained by the COBE/FIRAS bound on the CMB $\mu$-distortion, which limits the small-scale
curvature variance to $\sigma_\zeta^2 \lesssim 10^{-4}$. For Gaussian perturbations, the variance fixes the far tail of the one-point probability distribution function (PDF), making the PBH abundance negligible. We call this the Gaussian barrier. The barrier can be evaded only if the variance probed by the distortion is decoupled from the tail probability controlling collapse. We implement this idea in the non-perturbative $\delta N$ formalism and relate asymptotic PDF tails to the global shape of the $\delta N$ map. Four Gaussian-cored families are analyzed: generalized-normal, stretched-exponential, power-law, and log-normal tails. After standardizing each family to unit variance, we impose the FIRAS cap and compute the distortion-limited PBH abundance in the tail-shape parameter space. The ordinary exponential tail produced by standard single-field non-attractor dynamics is still too light to reopen the seed window. Algebraic tails from fractional-potential dynamics, and sufficiently heavy log-normal tails treated as a phenomenological proxy for multiplicative dynamics, can supply seed-relevant abundances while respecting the distortion bound.
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All authors Sanket Dave, Sheng-Feng Yan, Amara Ilyas, Yi-Fu Cai
Earth and Planetary Astrophysics
H.K. Vedantham, A. Strugarek, C.K. Louis et al. (+12 more)
Stars interact with their
exoplanets though
gravity, radiation,
plasma and
magnetic fields.
Stellar plasma and
magnetic fields impose electrodynamic effects on
exoplanet atmospheres and interiors that include heating, aurorae and atmospheric mass loss. The
planets in turn can excite Alfvénic disturbances that are dissipated on the
star leading to chromospheric heating and
flares. This interaction, broadly called
magnetic star-
planet interaction (M-SPI), can also generate
radio signatures both from the
star and the
exoplanet. The
radio emission encodes information on the dynamics/energetics of the interaction, the
magnetic field strength and
topology of the emitter and the orbital/rotational geometry of the system – information that is difficult or in some cases implausible to obtain by other means. Yet we do not have a conclusive detection of M-SPI in the
radio band primarily due to sensitivity limitations and scarce observing time spent monitoring promising targets. Here we describe the scientific motivation to study M-SPI in exoplanetary systems, to get progress in understanding its predicted signal strength and phenomenology. We argue that the SKA
telescopes can make a transformative contribution to
exoplanet science by detecting M-SPI in the
radio band but this will require substantial observing time – similar to that afforded to successful optical-band searches for M-SPI signatures.
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All authors H.K. Vedantham, A. Strugarek, C.K. Louis, J.R. Callingham, L. Peña-Moñino, M. Pérez-Torres, P. Zarka, E. Mauduit, N. Duchêne, P. Amado, S. Bloot, R. D. Kavanagh, A. A. Vidotto, L. Lamy, C. Tasse
Instrumentation and Methods for Astrophysics
Vector Apodizing Phase Plates for the ELT: From prototype to final optics for METIS and MICADO
J.A. van den Born, R. Landman, D.S. Doelman et al. (+12 more)
The first generation of instruments for the upcoming Extremely Large
Telescope (ELT) will allow for the direct imaging of
exoplanets that were previously below the sensitivity or resolution limits of existing facilities through various different High Contrast Imaging capabilities. Both METIS and MICADO will feature one or more Vector Apodizing Phase Plates (vAPP), a type of pupil-plane coronagraph based on
liquid crystal technology that allows for broadband phase modification to create zones of high contrast around an observed point source. The METIS vAPPs will operate at L- and M-band wavelengths between 3.1 and 5.1 $\mu$m, while the MICADO vAPP is optimized for shorter wavelengths in the J, H and Ks bands between 1.15 and 2.32 $\mu$m. In this work, we will provide a brief introduction to this type of coronagraph, followed by a discussion of the commonalities and differences between the METIS and MICADO vAPP designs. In the last year, the final optics have been in production. During preparations for the manufacturing and also during the production phase,various challenges were encountered related to coating inclusions, uniformity of the optically active layers and adhesion between the substrates. Through simulations and empirical findings, we argue that the effects of these imperfections on the on the final optical performance are limited. We will present the expected contrast curves, discuss the current status and reflect on the implications for on-sky observations with METIS and MICADO.
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All authors J.A. van den Born, R. Landman, D.S. Doelman, F. Snik, Y. Nishie, Y. Watanabe, M. Shoda, F.C.M. Bettonvil, E. Aranzana, J.H.H. Rietjens, T.P.G. Wijnen, P. Baudoz, O. Absil, G. Orban de Xivry, D. Dolkens
Instrumentation and Methods for Astrophysics
White Paper on Phototrophic Biosignatures: Research Priorities for the Search for Life on Other Worlds
Nancy Y. Kiang, Christopher Gisriel, Robert E. Blankenship et al. (+32 more)
Photosynthesis is of
prime interest in the telescopic search for life beyond the
Solar System, because, on Earth, oxygenic photosynthesis produces two strong "biosignatures," global scale signs of life that can be seen from space: atmospheric oxygen and the Vegetation Red Edge (VRE). The VRE is the spectral reflectance signature of plant leaves, characterized by a step-like increase in reflectance from the red to the near-infrared. The absorption in the red is due to chlorophyll $\textit{a}$ (Chl $\textit{a}$). While Chl $\textit{a}$ dominates our
planet, the Earth harbors diverse phototrophic organisms in niche environments possessing other pigments that produce edge-like spectral features across the UV-VIS-NIR, naturally suggesting diverse signatures that could be found on other
planets where phototrophic life is adapted to other
stars. However, the astrobiology community is very much at an early stage in its ability to constrain the probability that an observation of another
planet has detected a sign of photosynthetic life. This white paper identifies critical research questions to advance to a predictive capability the search for phototrophic biosignatures. These questions pertain to the origins, key features, diversity, and potential for alternative adaptations in fundamental aspects of light harvesting; the electron transfer pathway in photosynthesis; rhodopsin-based
proton-pumping; and carbon fixation. We discuss the need to constrain how
evolution and ecology affect the scaling up of these molecular mechanisms to be potentially detectable by a direct imaging mission. The research questions and recommendations presented here are cross-linked to those posed by the NASA Astrobiology Strategy 2015, and to the Focus Areas of the upcoming NASA Decadal Astrobiology Exploration Strategy (DARES).
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All authors Nancy Y. Kiang, Christopher Gisriel, Robert E. Blankenship, Mary N. Parenteau, Hazel A. Barton, Oded Béjà, Anthony J. Burnetti, Ligia F. Coelho, Saleheh Ebadirad, Nathan M. Ennist, Yuka Fujii, Colin Gates, R.J. Graham, Keiichi Inoue, Betül Kaçar, Yu Komatsu, Émilie A. Laflèche, Nicoletta La Rocca, Elisabetta Liistro, Jonathan Lindsey, Timothy Lyons, Carolina A. Martinez-Gutierrez, Taro Matsuo, Victoria Meadows, Gary F. Moore, Massimo Olivucci, Kevin E. Redding, Edward W. Schwieterman, Tejinder Singh, Kenji Takizawa, Anna Grace Ulses, Junko Yano, Felisa Wolfe-Simon, Michael L. Wong, Anastasia G. Yanchilina
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
George, I and the curvaton
Konstantinos Dimopoulos
George Lazarides was a pivotal collaborator and friend to me. We worked together on several projects, developing and exploiting the curvaton hypothesis, which was new at the time. This is a brief overview of our joint research.
High Energy Astrophysical Phenomena
A Square Kilometre Array Pulsar Census
E. F. Keane, V. Graber, L. Levin et al. (+7 more)
Most of the
pulsar science case with the Square Kilometre Array (SKA) depends on long-term precision timing of a large number of
pulsars, as well as their astrometric measurements using very long baseline interferometry (VLBI). However, before we can time them, or VLBI them, we must first find them. Here, we describe the considerations and strategies needed when planning an all-sky blind
pulsar survey using the SKA. Based on our understanding of the
pulsar population, the performance of the now-under-construction SKA elements, and practical constraints such as evading
radio frequency interference, we project
pulsar survey yields; this is done using two complementary methods for a number of illustrative survey designs, combining SKA-Low and SKA-Mid Bands 1 and 2 in a variety of ways. A composite survey using both SKA-Mid and SKA-Low is optimal, with Mid Band 2 focused in the plane. We find that, given its much higher effective area and survey speed, the best strategy is to use SKA-Low to cover as much sky as possible, ideally also overlapping with the areas covered by Mid. We find that an all-sky blind survey with Phase 1 of the SKA with the AA* array assembly will detect $\sim10,000$ slow
pulsars and $\sim 800$ millisecond
pulsars (MSPs) if SKA-Mid covers the region within $5\deg$ of the plane, while higher latitudes will be covered with SKA-Low. For the same survey region the yield with AA4 is $\sim 20\%$ higher, but this increases considerably by broadening the range covered by SKA-Mid Bands 1 and 2. In particular one could expect a yield of $\sim 1300$ MSPs with AA4. The
pulsar census will enable us to set new constraints on the uncertain physical properties of the entire
neutron star population. This will be crucial for addressing major SKA science questions including the dense-matter equation of state, strong-field
gravity tests, and gravitational wave astronomy.
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All authors E. F. Keane, V. Graber, L. Levin, C. M. Tan, O. A. Johnson, C. Ng, C. Pardo-Araujo, M. Ronchi, D. Vohl, M. Xue
High Energy Astrophysical Phenomena
Understanding the Neutron Star Population with the SKAO Telescopes
L. Levin, M. Bagchi, M. Burgay et al. (+12 more)
The known population of non-accreting
neutron stars is ever growing and currently consists of more than 3500 sources.
Pulsar surveys with the SKAO
telescopes will greatly increase the known population, adding
radio pulsars to every subgroup in the
radio-loud
neutron star family. These discoveries will not only add to the current understanding of
neutron star physics by increasing the known sample, but will undoubtedly also uncover new types of sources that will challenge our theories of a wide range of physical phenomena. A broad variety of scientific studies will be made possible by a significantly increased population of
neutron stars, unravelling questions such as: How do isolated
pulsars evolve with time; What is the connection between magnetars, high B-field
pulsars, and the newly discovered long-period
pulsars; How is a
pulsar's
spin-down related to its
radio emission; What is the
nuclear equation of state? Increasing the numbers of
pulsars in binary systems enables both larger numbers and higher precision tests of gravitational theories and general relativity, as well as probing the
neutron star mass distribution. The excellent sensitivity of the SKAO
telescopes combined with the wide field of view, large numbers of simultaneous tied-array beams that will be searched in real time, wide range of observing frequencies, and the ability to form multiple sub-arrays will make the SKAO an excellent facility for
neutron star research. This chapter presents an overview of different types of
neutron stars and discusses how the SKAO will aid in our understanding of the
neutron star population.
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All authors L. Levin, M. Bagchi, M. Burgay, A. T. Deller, V. Graber, A. Igoshev, M. Kramer, D. Lorimer, B. Posselt, T. Prabu, K. Rajwade, N. Rea, B. Stappers, T. M. Tauris, P. Weltevrede
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Flipped rotating axion: Baryogenesis and Dark Matter
Konstantinos Dimopoulos
It is shown that the co-genesis of
baryon asymmetry and dark matter can be achieved through the rotation of a spectator
axion-like particle, because of a flip in the
vacuum manifold's orientation at the end of inflation. This can occur if the
axion has a periodic non-minimal coupling to
gravity (while preserving the discrete shift
symmetry) in non-oscillating inflation models, where the inflaton field is characterised by a runaway potential. Our rotating
axion can generate the
baryon asymmetry of the Universe through spontaneous baryogenesis, while at a later epoch it can oscillate as dark matter. We show that in order to avoid fragmentation of the
axion condensate during the rotation, we require the non-minimal coupling $\xi\sim(f/m_P)^2$, where $f$ is the
axion decay constant.
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Astrophysics of Galaxies
Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde VI. The photodissociation region M17SW
X. Zhao, X. D. Tang, C. Henkel et al. (+20 more)
The kinetic temperature structure of the photodissociation region M17SW was mapped using the IRAM 30 m
telescope. This mapping employed the para-H2CO triplet (J(KaKc) = 303-202, 322-221, and 321-220) near 218 GHz on a scale of ~0.2 pc. The kinetic temperatures were derived by modeling the average H2CO line ratios (322-221/303-202 + 321-220/303-202) with the RADEX non-local thermodynamic
equilibrium approach. These temperatures range from 28 to 181 K with an average of 54.2 +/- 0.3 K at a spatial density of 5.5x10^5 cm^-3. Comparing with the temperature measurements obtained from multiple transitions of NH3 (1,1)-(6,6) and the far infrared (FIR)
dust continuum, the H2CO lines show temperatures similar to those measured by NH3 but slightly higher than values derived from FIR observations. The high kinetic temperatures observed from H2CO are associated with the ultracompact H II region UC1, dense clumps, as well as H2O and CH3OH masers, showing a similar distribution as NH3. This indicates that dense gas in the M17SW region is heated by
star formation activity. The presence of a significant gas temperature gradient across the M17SW region, as measured by H2CO and NH3, provides direct evidence for gas heated predominantly by radiation emitted from the OB
star cluster NGC 6618. On a smaller scale, the dense gas surrounding the dense clumps experiences significant heating from internal protostars and/or young
stellar objects. Higher temperatures traced by H2CO are linked to
turbulence on a scale of ~0.2 pc. The complex temperature structure of the M17SW region is revealed by H2CO and NH3, which may be attributed to both large-scale external radiative heating and small-scale internal radiative and turbulent heating.
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All authors X. Zhao, X. D. Tang, C. Henkel, K. M. Menten, Y. Gong, Y. Sun, Y. P. Ao, T. Liu, X. Lu, D. Li, Y. X. He, K. Wang, X. P. Chen, J. W. Wu, J. Esimbek, J. J. Zhou, X. W. Zheng, J. J. Qiu, J. S. Li, C. S. Luo, Q. Zhao, L. D. Liu, C. Y. Wang
High Energy Astrophysical Phenomena
F. Abbate, A. Carleo, S. Chatterjee et al. (+18 more)
The detection of a
pulsar closely orbiting our
Galaxy's supermassive black hole - Sagittarius~A* - is one of the ultimate prizes in
pulsar astrophysics. The relativistic effects expected in such a system could far exceed those currently observable in compact binaries such as double
neutron stars and
pulsar white
dwarfs. In addition,
pulsars offer the opportunity to study the magneto-ionic properties of Earth's nearest
galactic nucleus in unprecedented detail. For these reasons, and more, a multitude of
pulsar searches of the
Galactic Centre have been undertaken, with the outcome of just seven
pulsar detections within a projected distance of 100\,pc from Sagittarius~A*. It is currently understood that a larger underlying population likely exists, but it is not until observations with the SKA have started that this population can be revealed. In this chapter, we look at important updates since the publication of the last SKAO science book and offer a focused view of observing strategies and likely outcomes with the updated SKAO design.
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All authors F. Abbate, A. Carleo, S. Chatterjee, J. Cordes, P. B. Demorest, G. Desvignes, R.P. Eatough, E. Hackmann, Z. Hu, M. Kramer, J. Lazio, K.J. Lee, K. Liu, I. Rammala-Zitha, S.M. Ransom, G.Saowanit, L. Shao, P. Torne, R. Wharton, J. Wongphechauxsorn, W. Zhu
Astrophysics of Galaxies
Jet–ISM Interactions in Gaseous Disks: Simulating Kinetic Feedback in the Radio Galaxy 3C 326 N
Mayur B. Shende, Dipanjan Mukherjee, N. P. H. Nesvadba et al. (+4 more)
Several
radio galaxies, such as 3C\,326\,N, show signatures of jet–ISM coupling, but a complete theoretical framework for explaining them is still lacking. Interpreting these observations requires a detailed understanding of the gas distribution, geometry, and
outflow energetics. In this paper, we use three-dimensional relativistic hydrodynamic simulations to investigate jet–ISM coupling in inhomogeneous gaseous disks, exploring a parameter space spanning different cloud configurations, jet powers, and central disk densities. Our simulations incorporate a numerical
turbulence injection scheme that maintains vertical support in the disk, preventing the unphysical collapse encountered in previous studies. We find that jet–ISM coupling is strongly governed by the underlying cloud configuration, leading to distinct
outflow morphologies, velocity dispersions, and kinetic energies. Simulations with small-scale ($l_{\rm c,max}=50$~pc) clouds produce the highest velocity dispersions and kinetic energies, whereas large-scale cloud configurations ($l_{\rm c,max}=250$~pc) yield the lowest values, with mixed cloud distributions exhibiting intermediate behavior. In addition, mixed cloud configurations give rise to asymmetric jet propagation, naturally producing unequal lobe lengths similar to those observed in
radio galaxies. We compare our fiducial simulation (a $10^{45}\,\rm erg\,s^{-1}$ jet interacting with a mixed cloud configuration) with observations of 3C\,326\,N, focusing on the morphology of the jet-driven bubble, synthetic emission and the gas kinematics. Our results successfully reproduce the observed properties, providing strong evidence that jet–ISM interactions can account for the wide bubble and the complex gas kinematics observed in this system.
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All authors Mayur B. Shende, Dipanjan Mukherjee, N. P. H. Nesvadba, Geoffrey Bicknell, James Leftley, Moun Meenakshi, Raghav Gogia
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Majoron Dark Energy via Freezing Induced by Quantum Coherence
Keunsu Cheon, Sin Kyu Kang and Jungjai Lee
We propose a nonequilibrium mechanism for Majoron dark energy in which the late-time freezing of a physical Majoron is induced by
quantum coherence in a hidden pseudo-Dirac sterile
fermion reservoir. The evolving Majoron background derivatively couples to the hidden pseudo-Dirac number current and drives a lagged reservoir response with a finite
memory time. In the short-
memory regime, the causal response kernel reduces to \(\dot X+\Gamma_{\rm PD}X=\beta\ddot\phi\). The leading linear-response matching \(Q=\alpha X\) then yields an effective scalar equation containing the exchange structure \(q_{\rm exch}\ddot\phi/\dot\phi\). We show that this term can dynamically suppress the Majoron velocity and sustain a response-dominated freezing branch even when the intrinsic Majoron mass is larger than the present Hubble scale. The microscopic origin of the lag variable is identified with the phase-lagged off-diagonal coherence of the hidden pseudo-Dirac ensemble, while the response strength is controlled by a response-weighted hidden density rather than by an independent gravitating component. The resulting state is a metastable nonequilibrium frozen phase with \(w_\phi\simeq -1\), rather than an exactly static cosmological constant.
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High Energy Astrophysical Phenomena
Numerical Simulations of Restarted Jets – I. Dynamics
Prathamesh Ratnaparkhi, Dipanjan Mukherjee, Gianluigi Bodo et al. (+3 more)
We performed high-resolution three-dimensional relativistic magnetohydrodynamic (RMHD) simulations of restarted jets evolving within the cavity of a previous jet episode, using the PLUTO code. The simulations cover a spatial domain of $50\;\mbox{kpc}$ with a resolution of $40\;\mbox{pc}$. Three suites of simulations were performed to understand the impact of jet power,
magnetic fields and quiescence time on the
evolution of restarted jets. The restarted jets undergo a complex, multi-stage
evolution, with the remnant cocoon relaxing from an initially conical structure to a mushroom-shaped morphology via an intermediate cylindrical phase. As the cocoon of the initial jet expands, dense material entrained by fluid instabilities such as Kelvin-Helmholtz and Rayleigh-Taylor significantly alter the conditions within it. As a result, the interaction of the restarted jet with the cocoon is markedly different from that of the initial jet with the ambient medium. In particular, we find that the restarted jet propagates ballistically through the rarefied remnant cocoon, without creating prominent backflows. Deceleration of the jet and associated backflows are observed only when it encounters dense structures. The structure and strength of the shocks in restarted jets are affected by jet power,
magnetic field strength, and quiescence time. Finally, we discuss the implications of the dynamics for observed properties of
radio galaxies.
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All authors Prathamesh Ratnaparkhi, Dipanjan Mukherjee, Gianluigi Bodo, Paola Rossi, Marisa Brienza, Raffaella Morganti
Instrumentation and Methods for Astrophysics
The SKAO Pulsar Timing Array
Ryan M. Shannon, N. D. Ramesh Bhat, Aurélien Chalumeau et al. (+22 more)
Pulsar timing arrays (PTAs) are ensembles of millisecond
pulsars observed for years to decades. The primary goal of PTAs is to study gravitational-wave astronomy at nanohertz frequencies, with secondary goals of undertaking other fundamental tests of physics and astronomy. Recently, compelling evidence has emerged in established PTA experiments for the presence of a gravitational-wave background. To accelerate a confident detection of such a signal and then study gravitational-wave emitting sources, it is necessary to observe a larger number of millisecond
pulsars to greater timing precision. The SKAO
telescopes, which will be a factor of three to four greater in sensitivity compared to any other southern hemisphere facility, are poised to make such an impact. In this chapter, we motivate an SKAO
pulsar timing array (SKAO PTA) experiment. We discuss the classes of gravitational waves present in PTA observations and how an SKAO PTA can detect and study them. We then describe the sources that can produce these signals. We discuss the astrophysical noise sources that must be mitigated to undertake the most sensitive searches. We then describe a realistic PTA experiment implemented with the SKA and place it in context alongside other PTA experiments likely ongoing in the 2030s. We describe the techniques necessary to search for gravitational waves in the SKAO PTA and motivate how very long baseline interferometry can improve the sensitivity of an SKAO PTA. The SKAO PTA will provide a view of the Universe complementary to those of the other large facilities of the 2030s.
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All authors Ryan M. Shannon, N. D. Ramesh Bhat, Aurélien Chalumeau, Siyuan Chen, H. Thankful Cromartie, A. Gopakumar, Kathrin Grunthal, Jeffrey S. Hazboun, Francesco Iraci, Bhal Chandra Joshi, Ryo Kato, Michael J. Keith, Kejia Lee, Kuo Liu, Hannah Middleton, Matthew T. Miles, Chiara M. F. Mingarelli, Aditya Parthasarathy, Daniel J. Reardon, Golam M. Shaifullah, Keitaro Takahashi, Caterina Tiburzi, Riccardo J. Truant, Xiao Xue, Andrew Zic
High Energy Astrophysical Phenomena
FAST Pulsar Database III. Snapshots of nulling, mode-changing and subpulse modulation of 374 pulsars
Yi Yan, J. L. Han, J. Xu et al. (+8 more)
Based on sensitive L-band (1.0 to 1.5 GHz) observations of
pulsars using the Five-hundred-meter Aperture Spherical
radio Telescope (FAST), we analyzed single-pulse sequences from FAST-detected
pulsars and identified nulling, mode changing, or subpulse modulation phenomena in 374 sources. Among these, nulling has been detected in 160
pulsars, with 127 cases reported for the first time. Emission mode changes have been observed in 52
pulsars, including 51 first-time detections. Subpulse modulation has been identified in 272
pulsars, 180 of which are newly revealed, with the majority displaying subpulse drifting behavior. Subpulse drifting in some
pulsars exhibits distinct modes with varying drift properties, leading to mode changes and divergent mean profiles. Statistics on
pulsar parameters show that
pulsars exhibiting nulling and/or subpulse modulation tend to be older, with longer periods and lower
spin-down energy-loss rates. The modulation period P3 is predominantly correlated with
pulsar rotation periods,
magnetic field strengths, and
spin-down energy loss.
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All authors Yi Yan, J. L. Han, J. Xu, N. N. Cai, W. Q. Su, P. F. Wang, C. Wang, T. Wang, D. J. Zhou, W. C. Jing, Z. L. Yang
Instrumentation and Methods for Astrophysics
nmma: An extended Bayesian framework for Nuclear Multimessenger Astronomy in the Era of Next-Generation Detectors
Henrik Rose, Hauke Koehn, Thibeau Wouters et al. (+4 more)
Context. The joint analysis of different (astro-)physical messengers, in particular gravitational-wave data and electromagnetic follow-up observations, allows us to establish, explore and deepen links between different physical fields. As new survey capacities and improved detection methods will lead to a significant increase in the number of multimessenger detections in the upcoming decades, efficient and versatile software frameworks are essential to maximise the scientific outcome of such multimessenger studies. Aims. We present a major upgrade to the
Nuclear Multimessenger Astronomy (nmma) framework, incorporating various recent developments in theoretical modelling and machine learning in a modularised and easily extendable
Bayesian framework. For the first time, this allows direct sampling on
nuclear parameters alongside gravitational-wave, kilonova and afterglow parameters. Methods. We combine fast surrogate models for electromagnetic transients with speed-ups from emulators that map
nuclear parameters to macroscopic
neutron-
star properties. Additional acceleration methods for the evaluation of state-of-the-art waveform approximants enable full
Bayesian analyses of multimessenger events at the speed required in the era of next-generation detectors. Results. We demonstrate the capabilities of the upgraded nmma framework through a series of representative applications. Reanalysing the 2017 multi-messenger detection of a
neutron-
star merger, we achieve 20- to 60-fold speed-ups while using more detailed physical models compared to previous studies. Moreover, we demonstrate for a hypothetical future detection how we can simultaneously constrain
nuclear parameters and the Hubble parameter with robustly quantified uncertainties.
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All authors Henrik Rose, Hauke Koehn, Thibeau Wouters, Peter T. H. Pang, Mattia Bulla, Michael W. Coughlin, Tim Dietrich
Instrumentation and Methods for Astrophysics
Rapid Response Triggering for Radio Transients with the SKA Observatory
G. E. Anderson, S. I. Chastain, A. P. Curtin et al. (+10 more)
Rapid-response triggering is when a
telescope is able to automatically respond to an external or internal astronomical transient alert, causing it to rapidly repoint at that position in the sky to catch its earliest
radio emission. Both SKA-Low and SKA-Mid will have the ability to perform rapid-response triggering observations on externally detected transients as well as those detected within the data streams. We first give a brief overview of those
radio instruments with active rapid-response observing modes. We then describe the different science cases motivating the need for this observing capability on SKAO and how the additional sensitivity afforded by the SKAO will enable us to answer fundamental questions relating to particle acceleration, transient central engines, coherent emission models and
outflow physics in astrophysical systems spanning the range from the Sun to the high
redshift Universe. Several suggestions relating to existing technologies and necessary SKAO system requirements are described. Through this chapter, we aim to ensure this is an existing, common and useful capability for the SKA Observatory.
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All authors G. E. Anderson, S. I. Chastain, A. P. Curtin, K. Gourdji, N. Hurley-Walker, C. W. James, R. F. Mandow, B. Marcote, D. Oberoi, K. M. Rajwade, K. Rose, A. Rowlinson, F. Schüssler
Astrophysics of Galaxies
Hayley Bignall and Rajan Chhetri
Time domain studies of active
galactic nuclei (AGN) at
radio wavelengths probe physical processes near the central engine via intrinsic variability, in particular within the relativistic jets, as well as small-scale structures in the local
Galactic interstellar medium (ISM) via scintillation and scattering effects. Recent discoveries reinforce the expectation that the high sensitivity, large field-of-view, and broadband frequency coverage of the SKA
telescopes will help to revolutionise our understanding of AGN populations and the
evolution of jets, and allow detailed modelling of the structure and dynamics of scattering
plasma in the local ISM over a large fraction of the sky.
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Astrophysics of Galaxies
Star Formation in the NE-Circinus Molecular Cloud Complex
Daniel Rose
This paper presents the first dedicated characterization of the NE-Circinus Complex (TGU H1984, DCld 320.7-03.6), a previously unstudied
star-forming dark cloud complex serendipitously identified in archival Herschel SPIRE observations targeting the foreground Bok globules BHR 99 and BHR 100. Using Herschel SPIRE photometry, Planck
Galactic Cold Clumps data, near-infrared 2MASS colour excess mapping, AllWISE photometry,
Gaia DR3 photometry, and a 3D
dust extinction map, the complex, and its embedded YSO population are characterized for the first time. Two independent photometric methods place the complex at 750 +/- 50 pc. Three morphologically distinct components are identified: a dense main cloud body, a diffuse eastern component, and a northern filamentary extension. The main cloud body has a SPIRE-derived
dust temperature of 14.5 +/- 0.5 K. Near-infrared H-K colour excess mapping yields a core gas mass of ~277 Msun and a total gas mass of ~439 Msun, consistent with the Planck PGCC column density. An AllWISE YSO census identifies 39 candidates across all three components, confirming active
star formation throughout the complex. Multi-epoch NEOWISE-R photometry reveals three significantly variable sources, including one aperiodic dipper - a previously uncatalogued YSO exhibiting dimming consistent with inner-disc occultation. Two previously uncatalogued compact Bok globules are identified on the western edge of the northern extension, both detected in SPIRE continuum emission. That this complex went uncharacterized despite Herschel data being publicly available since 2013 underscores the scientific value of archival examination and the incomplete state of southern sky molecular cloud inventories.
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Astrophysics of Galaxies
The Epoch of the GSE Merger: Insights from the Splash and Thick Disk Age Distributions
Sihan Lu, Yang Huang, Qikang Feng et al. (+1 more)
The epoch of the
Gaia-Sausage-Enceladus (GSE) merger, the last major merger experienced by the Milky Way, is crucial for reconstructing the
Galaxy's evolutionary history. This event dynamically heated the disk, scattering some
stars into the
halo and producing the so-called Splash. Yet the observed age distribution of the Splash is systematically older than that of the thick disk from which it is thought to originate, posing a puzzling inconsistency. In this work, we show that this apparent discrepancy can be naturally explained once
stellar age uncertainties are taken into account. The GSE truncated the intrinsic age distribution of the Splash at the merger epoch, while measurement errors introduce an Eddington-like bias that systematically shifts the truncated distribution toward older ages. Importantly, the magnitude of this shift depends on both the thick-disk
star formation history and the merger epoch, thereby offering a new way to constrain the timing of the merger. By combining the observed Splash age distribution with the peak of thick-disk
star formation, we infer a GSE merger epoch of $10.1^{+0.2}_{-0.2}$ Gyr ago, providing one of the tightest constraints to date. This result offers new insight into the Milky Way's
accretion history and opens a path toward more robust reconstructions of its early
evolution.
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All authors Sihan Lu, Yang Huang, Qikang Feng, Huawei Zhang
High Energy Astrophysical Phenomena
No Strong Evidence for Plasma Lensing in FRB 20240114A
Jiarui Niu, Nan Xu, Xiaohui Liu et al. (+32 more)
FRB 20240114A is an extremely active repeating fast
radio burst for which
plasma lensing has been proposed to explain its burst-rate variations, spectral
evolution, and apparently “carbon-copy” burst pairs. Using FAST data and publicly available Parkes observations, we test this interpretation with the predictions of a one-dimensional Gaussian
plasma-lens model. Although the burst-rate enhancements may be fitted separately for Parkes and FAST, the corresponding magnification peaks and demagnification troughs between the two
datasets are offset from each other, inconsistent with
plasma lensing predictions. The enhancement peaks also do not show consistent periodicity, disfavoring a binary
plasma lensing origin. The burst bandwidths are not systematically narrower during the proposed
lensing interval than in other episodes. Most importantly, the burst energy distribution, which shows an intrinsic turnover peak at low energies, shows no significant shift of the turnover during the magnification interval, providing a model-independent test to the
plasma-
lensing interpretation. All these suggest that there is no strong evidence in favor of a
plasma lensing interpretation to the source. Rather, all the burst property variations are consistent with being caused by the intrinsic variations of the FRB central engine.
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All authors Jiarui Niu, Nan Xu, Xiaohui Liu, Songyu Shen, Junshuo Zhang, Tiancong Wang, Pawan Kumar, Yuanhong Qu, Dejiang Zhou, Weiwei Zhu, Bing Zhang, He Gao, Dongzi Li, Jinlin Han, Di Li, Xuelei Chen, Kejia Lee, Ye Li, Weiyang Wang, Qiuyang Fu, Jiawei Jin, Yanqing Cai, Caisong Liu, Shuo Cao, Ziwei Wu, Dengke Zhou, Longxuan Zhang, Wanjin Lu, Yi Feng, Chenhui Niu, Jiawei Luo, Rui Luo, Chunfeng Zhang, Shiqian Zhao, Chengwei Liang
Astrophysics of Galaxies
Revisiting the Radial Velocities of Nearby Open Clusters using Gaia DR3
Tong Tang, Yu Zhang, Jing Zhong et al. (+4 more)
Open clusters (OCs) are essential laboratories for probing
stellar dynamics and tracing the structure and
evolution of the Milky Way. Accurate measurements of their average radial velocities (RVs) and RV dispersions are crucial for estimating dynamical masses, orbital
evolution, and overall kinematic states.
Gaia Data Release 3 (DR3) provides an unprecedented volume of high-precision RVs. However, when applied to OCs,
Gaia DR3 RVs often yield unusually large and overestimated RV dispersions. This inflation is primarily driven by RV measurement systematics for hot and faint
stars, as well as unresolved binary contamination. To mitigate this, we revisit the average RVs and RV dispersions of OCs within 500 pc of the Sun using
Gaia DR3. We evaluate the reliability of RV measurements and employ a color-based filtering method. By selecting member
stars within an intrinsic color range of $0.2 \le (BP-RP)_{0} \le 1.2$ mag, we exclude hot and cool
stars with less reliable RVs. This filtering significantly reduces the inferred RV dispersions while maintaining average RVs consistent with previous literature. Specifically, the median RV dispersion decreases by 26%, dropping from 3.76 km s$^{-1}$ prior to filtering to 2.79 km s$^{-1}$ afterward. These filtered RV dispersions remain systematically larger than tangential velocity dispersions, likely due to residual biases and undetected binaries. However, RV dispersions measured exclusively from red clump
giants (found in 6 clusters) are remarkably small ($\lesssim 1.6$ km s$^{-1}$) and align closely with tangential dispersions ($\lesssim 1$ km s$^{-1}$). Ultimately, we provide a practical,
Gaia-only strategy to derive more realistic RV dispersions for OCs, identifying red clump
giants as exceptionally high-fidelity kinematic tracers for robust cluster studies.
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All authors Tong Tang, Yu Zhang, Jing Zhong, Guimei Liu, Songmei Qin, Shusong Wang, Li Chen
Astrophysics of Galaxies
Direct Evidence for Outflow Driven by Wolf-Rayet Stars in the Nearby Galaxy PGC44685
Qian Huang, Zhengyi Chen, Min Bao et al. (+3 more)
Wolf–Rayet (WR)
stars are evolved massive
stars which can drive strong
stellar winds, injecting energy and momentum into the interstellar medium (ISM). However, the geometry and kinematics of WR-dominated
outflows, specially in low-
metallicity environments, is still poorly constrained by observations. We present a spatially resolved spectroscopic study of a WR region in a nearby
dwarf galaxy, PGC\,44685, using high-resolution MEGARA IFU data from the Gran Telescopio Canarias (GTC). After decomposing the [O iii]~$\lambda5007$ emission line with narrow and broad components, we verify a WR-driven
outflow with a velocity reaching up to $20\,\mathrm{km\,s^{-1}}$ relative to the systemic velocity. By use of the velocity and flux of the [O iii] broad component, we estimate an
outflow mass of $(8.25 \pm 3.03)\times10^{3}\,M_\odot$ and a mass-loss rate of $(9.47 \pm 3.48)\times10^{-4}\,M_\odot\,\mathrm{yr}^{-1}$. The corresponding kinetic power and momentum injection rate are $(4.77 \pm 1.77)\times10^{41}\,\mathrm{erg\,s^{-1}}$ and $(8.20 \pm 3.02)\times10^{28}\,\mathrm{g\,cm\,s^{-2}}$, respectively. The inferred low energy-loading efficiency ($\sim0.35\%$), together with the low
metallicity of the WR region ($\sim0.1\,Z_\odot$), suggests that the system is observed in an early feedback phase in which
stellar winds have not yet efficiently coupled their energy into the ISM. These results support the ability of WR feedback to shape the ISM on sub-kiloparsec scales, while these winds fail to launch
galactic-scale
outflows.
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All authors Qian Huang, Zhengyi Chen, Min Bao, Qiusheng Gu, Shiying Lu, Yulong Gao
Solar and Stellar Astrophysics
Improving Solar EUV Irradiance Modeling with Differential Emission Measure Informed Spectra
Courtney L. Peck, Shah M. Bahauddin, Daniel B. Seaton et al. (+3 more)
Solar extreme ultraviolet (EUV) irradiance predominantly originates from the chromosphere and corona, and variations in EUV irradiance are a significant driver of space weather at Earth, causing increased satellite drag,
radio communication disruptions, and reduced GPS accuracy. Since
solar EUV irradiance measurements are intermittent and inhomogeneous, models are used to fill spectral and temporal gaps, typically relying on proxy-based methods that utilize linear correlations between emission originating from similar heights or temperatures in the
solar atmosphere. Proxy methods can struggle to capture dynamic irradiance variations of the
solar corona during
flares in part due to the relative infrequency of
flares on which to derive correlations and the steep temporal temperature gradients experienced during
flares. This paper presents a hybrid method for modeling
solar EUV irradiance utilizing forward-modeled physics-informed
solar differential emission measures (DEMs) to capture the optically-thin coronal emission coupled with traditional proxy-based correlation methods to capture the chromospheric and continuum emission. The model is trained and tested using inputs from the
Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) and EUV Variability Experiment (EVE) and compared against a proxy-only method. The results demonstrate that including information from DEMs into a EUV irradiance model improves accuracy for flaring conditions, particularly for high-temperature coronal lines, where the model error is reduced by up to a factor of 3 for M- and X-class
flares compared to a proxy-only model trained on the same data.
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All authors Courtney L. Peck, Shah M. Bahauddin, Daniel B. Seaton, Janet L. Machol, Ed Thiemann, Mark Cheung
High Energy Astrophysical Phenomena
Evidence for Asymmetric Ejecta and Circumstellar Material in SN 2023ixf Inferred from Extensive Nebular-phase Observations
Brian Hsu, Nathan Smith, K. Azalee Bostroem et al. (+34 more)
We present extensive optical and near-infrared (NIR) observations of the nearby Type II
supernova (SN II) 2023ixf in the nebular phase from +89 days to +749 days after explosion, supplemented with NIR and mid-infrared (MIR) spectroscopy from the James Webb Space
Telescope. The H$\alpha$ emission profile shows complex
evolution, with the emergence of high-velocity components consistent with the outer ejecta interacting with extended, low-density circumstellar material (CSM). We find that the H$\alpha$ profile at an intermediate epoch (around +375 d) can be reconstructed by scaling an earlier decay-powered component and a later-phase shock-powered component, which revealed an additional intermediate-width component. This is consistent with the ejecta crashing into the initially aspherical dense CSM that has been swept-up by the forward shock. In the NIR, we find double-peaked emission from Mg I $1.504\ {\rm \mu m}$, Na I $2.206\ {\rm \mu m}$, and [Ni I] $3.12\ {\rm \mu m}$ between +200 d and +374 d, consistent with an asymmetric distribution of Ni-rich material that heats the ejecta inhomogeneously. We posit a disk-like CSM geometry and an ejecta geometry in which at least two large Ni-rich plumes lead to the observed line-profile diversity.
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All authors Brian Hsu, Nathan Smith, K. Azalee Bostroem, Jeniveve Pearson, David J. Sand, Lindsey A. Kwok, Jennifer E. Andrews, Bhagya M. Subrayan, Griffin Hosseinzadeh, Manisha Shrestha, Conor Ransome, Moira Andrews, Collin T. Christy, Yize Dong, Joseph Farah, Alexei V. Filippenko, Noah Franz, Jared A. Goldberg, Estefania Padilla Gonzalez, Claudia P. Gutiérrez, Emily Hoang, D. Andrew Howell, Saurabh W. Jha, Réka Kőnyves-Tóth, Michael Lundquist, Curtis McCully, Darshana Mehta, Nicolas E. Meza Retamal, Megan Newsome, Aravind P. Ravi, Jeonghee Rho, Giacomo Terreran, Stefano Valenti, Sergiy Vasylyev, X.-F. Wang, Kathryn Wynn, Yi Yang
Earth and Planetary Astrophysics
Revisiting the dynamics of the Prometheus-Pandora system
Demétrio Tadeu Ceccatto, Nelson Callegari Jr. and Gabriel Teixeira Guimarães
This study revisits the dynamics of Prometheus and Pandora. The analysis focuses on their current orbits and considers mutual perturbations and the non-spherical shape of Saturn. Numerical integrations of the full equations of motion were performed in the context of the N-body problem using a dense set of initial conditions. Spectral analysis of these orbits, together with an interpretation of the dynamical maps, revealed several resonance domains of various orders between Prometheus and Pandora, including the 121:118 resonance domain. Resolving the secular equations for eccentricity and inclination revealed the absence of a forced component in both cases. The period associated with the precession rate, $\Delta\varpi$, corresponds to the anti-
alignment period. Chaos was quantified by analysing the
diffusion of independent frequencies, which indicates dynamics governed by weak chaos. Minor perturbations caused by the Janus-Epimetheus pair on the orbits of Prometheus and Pandora were also considered. Finally, we investigated the dynamical history of the Prometheus Pandora system, accounting for Pandora's migration due to
tidal interactions with Saturn. This revealed several past cross-resonances with a low probability of capture, as well as a scenario in which the Prometheus-Pandora pair exhibited a co-orbital configuration.
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Earth and Planetary Astrophysics
Uniform Metallicity Measurements of M Dwarf Planet Hosts Support Metallicity-Dependent Sub-Neptune Formation
Emma V. Turtelboom, Steven Giacalone, Rebecca Gore et al. (+6 more)
M
dwarfs are the most common sites of
planet formation in the Milky Way.
Planet occurrence and composition are closely linked with the availability of metals in protoplanetary disks, which can be probed by measuring
planet host
star metallicities. In this work, we measure the
metallicities ([M/H] and [Fe/H]) of 59 M
dwarfs hosting 76
planets and candidates using medium-resolution near-infrared spectra collected with IRTF/SpeX. We combine these results with literature
metallicity measurements for
planet-hosting cool
dwarfs, and present 86
stars hosting 142 candidate, validated, and confirmed
planets with homogeneously derived
stellar parameters. Using our updated
stellar radii, we calculate
planet radii from TESS transit depths for both the confirmed (N = 51, 0.6 - 12.5 R$_\oplus$, median $R_p$ = 1.8R$_\oplus$) and candidate (N = 25, 0.6 - 7.2 R$_\oplus$, median $R_p$ = 2.1R$_\oplus$)
planets. We compare the
metallicity distributions of super-Earth and sub-Neptune host
stars, finding that M
dwarfs hosting sub-Neptunes are statistically more metal-rich than those hosting super-Earths. This result is robust to the radius valley prescription used, and is likely not due to differences in the
stellar samples considered. This result supports the hypothesized formation pathway whereby sub-Neptunes form beyond the water ice line where they can accrete volatiles before migrating inwards to their observed locations. The enhanced inventories of refractory elements throughout the disk and of volatiles beyond the ice line in metal-rich disks around low-mass
stars may contribute to the preference seen in the observed
planet sample for sub-Neptunes to orbit metal-rich M
dwarfs.
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All authors Emma V. Turtelboom, Steven Giacalone, Rebecca Gore, Courtney D. Dressing, Ryan Cloutier, Karina Kimani-Stewart, Aida Behmard, C.M. Lisse, M.L. Sitko