High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Charged Rotating Black Hole and the First Law
S. D Campos
The thermodynamic properties of black holes have been extensively studied through analogies with classical systems, revealing fundamental connections between gravitation,
entropy, and
quantum mechanics. In this work, we extend the thermodynamic framework of black holes by incorporating charge and analyzing its role in
entropy production. Using an analogy with charged rotating soap bubbles, we demonstrate that charge contributes to the total angular momentum and affects the
entropy-event horizon relationship. By applying the Gouy-Stodola
theorem, we establish a consistent thermodynamic formulation for charged black holes, showing that the first law of thermodynamics remains valid in this context. Furthermore, we explore the behavior of the partition function from the perspective of a distant observer, revealing that charge effects diminish with increasing distance. These findings reinforce the thermodynamic interpretation of black holes and provide insights into the interplay between charge, rotation, and
entropy in gravitational systems.
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Cosmology and Nongalactic Astrophysics
Unbiased Primordial Gravitational Wave Inference from the CMB with SMICA
Alexander Steier, Shamik Ghosh and Jacques Delabrouille
The detection of
primordial gravitational waves in
Cosmic Microwave Background B-mode polarization observations requires accurate and robust subtraction of astrophysical contamination. We show, using a blind Spectral Matching Independent Component Analysis, that it is possible to infer unbiased estimates of the
primordial B-mode signal from ground-based observations of a small patch of sky even for highly complex foreground contamination. This work, originally performed in the context of configuration studies for a future CMB-S4 observatory, is highly relevant for the analysis of observations by the current generation of CMB experiments.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.atom-ph
Wavefront Curvature and Transverse Atomic Motion in Time-Resolved Atom Interferometry: Impact and Mitigation
Noam Mouelle, Jeremiah Mitchell, Valerie Gibson et al. (+1 more)
Time-resolved atom interferometry, as employed in applications such as gravitational wave detection and searches for ultra-light dark matter, requires precise control over systematic effects. In this work, we investigate phase noise arising from shot-to-shot fluctuations in the atoms' transverse motion in the presence of the wavefront
curvature of the interferometer beam, and analyse its dependence on the
laser-beam geometry in long-baseline, large-momentum-transfer atom interferometers. We use a semi-classical framework to derive analytical expressions for the effective phase perturbation in position-averaged measurements and validate them using Monte Carlo simulations. Applied to 100-m and 1-km atom gradiometers representative of next-generation experiments, the model shows that configurations maximizing pulse efficiency also amplify
curvature-induced phase noise, requiring micron-level control of the atom cloud's centre-of-mass position and sub-micron-per-second control of its centre-of-mass velocity to achieve sub-$10^{-5}$ rad phase stability. Alternative beam geometries can suppress this noise by up to two orders of magnitude, but at the cost of reduced pulse efficiency. To address this limitation, we propose a mitigation strategy based on position-resolved phase-shift readout, which empirically learns and corrects the wavefront-induced bias from measurable quantities such as the phase-shift gradient and final cloud position. This approach restores high-sensitivity operation in the maximum-pulse-efficiency configuration without detailed beam characterisation, providing a practical route towards next-generation, time-resolved atom interferometers operating at the $10^{-5}$ rad noise level.
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All authors Noam Mouelle, Jeremiah Mitchell, Valerie Gibson, Ulrich Schneider
Cosmology and Nongalactic Astrophysics
The Weighing Halos Accurately, Locally, and Efficiently with Supernovae (WHALES) Survey Overview and Initial Data Release
Maria Acevedo, Daniel Scolnic, Bastien Carreres et al. (+6 more)
We present an overview of the Weighing
Halos Accurately, Locally, and Efficiently with
Supernovae (WHALES) survey, the first to discover and measure Type Ia
supernovae (SNe Ia) in and around
galaxy superclusters. By building a sample of SNe~Ia around these massive environments, we aim to provide new constraints on bulk-flow models while laying the groundwork for improved estimates of supercluster masses. Here, we present data from the first two seasons targeting the Shapley Supercluster (0.02<z<0.06), which is responsible for a large but unknown fraction of our local group's motion. Until now, no
supernovae had been analyzed in the direction of Shapley. Through the WHALES survey, we have identified 12 likely SNe Ia in this region using SkyMapper, including 8 with spectroscopic confirmation. We present the first light curves of these SNe and combine our observations with data from ATLAS. We demonstrate that the low number of discovered SNe Ia per season is consistent with various rate calculations, highlighting the need for future surveys to monitor superclusters over a multi-year timespan. Finally, we present simulations of SN Ia observations in the environments of massive
galaxy clusters, demonstrating how the inferred peculiar velocities can constrain cluster masses, and highlighting the added complexity within superclusters. We find that a sample of 100 SNe Ia would enable a 25% precision measurement of the total mass of the Shapley Supercluster.
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All authors Maria Acevedo, Daniel Scolnic, Bastien Carreres, Erik R. Peterson, Bruno O. Sanchez, Christopher Lidman, Bailey Martin, Christopher A. Onken, Adam G. Riess
Astrophysics of Galaxies
Active Dwarf Galaxy Database II: Connections between Host Galaxy Properties and Black Hole Accretion Signatures
Erik J. Wasleske, Vivienne F. Baldassare and Christopher M. Carroll
We investigate the connection between
accretion signatures and host
galaxy properties in the context of how active
dwarf galaxies are identified. We use the database constructed in Wasleske & Baldassare (2024) which contains
dwarf galaxies that were selected as active
galaxies by optical spectroscopy, infrared colors, X-ray brightness, and photometric variability. Multi-wavelength archival data was used to consistently apply all of these methods to every
galaxy within this compiled set. The cross application of these methods resulted in a diversity of sub-populations identified as active by some set of these techniques. In this paper, we estimate host
galaxy properties from spectral energy distribution models. We connect the active
galactic nuclei (AGN) signatures to our estimated host
galaxies' properties using statistical dimensionality reduction methods. We find that
dwarf AGN selected by infrared colors are the most distinct population, with the highest
star formation rates and lowest
stellar masses. We also find some other key population differences, such as the broad line AGN having significantly higher AGN luminosities. X-ray and variability selected AGN have higher average
star formation rates than those selected with optical narrow line spectroscopic diagrams. Our connections to the host
galaxy parameters potentially point to the sub-populations representing different epochs of the
evolution of
accretion.
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Cosmology and Nongalactic Astrophysics
Flinch: A Differentiable Framework for Field-Level Inference of Cosmological parameters from curved sky data
Andrea Crespi, Marco Bonici, Arthur Loureiro et al. (+6 more)
We present Flinch, a fully differentiable and high-performance framework for field-level inference on angular maps, developed to improve the flexibility and scalability of current methodologies. Flinch is integrated with differentiable cosmology tools, allowing gradients to propagate from individual map pixels directly to the underlying cosmological parameters. This architecture allows cosmological inference to be carried out directly from the map itself, bypassing the need to specify a likelihood for intermediate summary statistics. Using simulated, masked CMB temperature maps, we validate our pipeline by reconstructing both maps and angular power spectra, and we perform cosmological parameter inference with competitive precision. In comparison with the standard pseudo-$C_\ell$ approach, Flinch delivers substantially tighter constraints, with error bars reduced by up to 40%. Among the gradient-based samplers routinely employed in field-level analyses, we further show that MicroCanonical Langevin Monte Carlo provides orders-of-magnitude improvements in sampling efficiency over currently employed
Hamiltonian Monte Carlo samplers, greatly reducing computational expense.
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All authors Andrea Crespi, Marco Bonici, Arthur Loureiro, Jaime Ruiz-Zapatero, Ivan Sladoljev, Zack Li, Adrian Bayer, Marius Millea, Uroš Seljak
Instrumentation and Methods for Astrophysics
Stellar Spectroscopy Using Diffraction Grating, CMOS Monochrome Sensor and Reflecting Telescopes
Abhinav Roy and Niti Singh
We present the design and testing of a compact
stellar spectrometer developed for undergraduate and outreach applications. The spectrometer module, comprising an inexpensive 600 lines/mm diffraction grating, a CMOS monochrome sensor, and a 3D-printed mount, can be constructed at modest cost and integrated with reflecting
telescopes commonly available at educational institutions. Calibration was performed using a helium emission source in the laboratory and Vega as a spectrophotometric standard, supported by a custom Python-based data-reduction pipeline for wavelength calibration and spectral stacking. The spectrometer successfully recorded usable spectra of bright
stars including Vega, Sirius, Procyon, Capella, and Betelgeuse, covering spectral types A through M. The results demonstrate that meaningful
stellar spectroscopy can be achieved by institutions with existing
telescope infrastructure, providing a practical framework for student-led astronomical instrumentation projects.
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Solar and Stellar Astrophysics
The ODYSSEUS Survey. Spatial correlation of magnetospheric inclinations points to parsec-scale star-cloud connection
Caeley V. Pittman, Catherine C. Espaillat, Thanawuth Thanathibodee et al. (+3 more)
The properties of
stars and
planets are shaped by the initial conditions of their natal clouds. However, the spatial scales over which the initial conditions can exert a significant influence are not well constrained. We report the first evidence for parsec-scale spatial correlations of
stellar magnetospheric inclinations ($i_{\rm mag}$), observed in the Lupus low-mass
star forming region. Applying consensus clustering with a hierarchical density-based clustering
algorithm, we demonstrate that the detected spatial dependencies are stable against perturbations by measurement uncertainties. The $i_{\rm mag}$ correlation scales are on the order of ~3 pc, which aligns with the typical scales of the Lupus molecular cloud filaments. Our results reveal a connection between large-scale forces – in the form of expanding shells from the Upper Scorpius and Upper-Centaurus-Lupus regions – and sub-au scale system configurations. We find that Lupus has a non-uniform $i_{\rm mag}$ distribution and suggest that this results from the preferential elongation of protostellar cores along filamentary axes. Non-uniformity would have significant implications for
exoplanet occurrence rate calculations, so future work should explore the longevity of these biases driven by the
star-cloud connection.
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All authors Caeley V. Pittman, Catherine C. Espaillat, Thanawuth Thanathibodee, Nuria Calvet, Lee W. Hartmann, Sylvie Cabrit
Solar and Stellar Astrophysics
An extremely fast fading population II dwarf nova candidate: caught spectroscopically on the rise
Natasha Van Bemmel, Jielai Zhang, Jeff Cooke et al. (+14 more)
We present AT2022kak, a rapidly evolving optical transient discovered by the KiloNova and Transients Program (KNTraP). This interesting burst exhibited extremely fast
evolution, with a large amplitude blue outburst of m > 3.3 in a single night, and a rapid fade back to quiescence in the following two nights. We deployed a multi-wavelength follow-up campaign, monitoring the object for the next two months, but saw no recurrent burst. Three years later, while observing to get spectroscopy of the object in quiescence, there was a new outburst, enabling the collection of time-resolved spectra of the rise and fade of the outburst. The light curve properties of the first burst and spectra of the second burst are consistent with a
dwarf nova. Its fast evolving behaviour makes it one of the fastest and faintest
dwarf novae observed. The estimated distance of AT2022kak from the
Galactic centre is ~6.6 kpc, with a scale height of ~2 kpc. This scale height places it in the
Galactic thick disk, where only very few
dwarf novae have been found, and is therefore a potential Population II
dwarf novae system.
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All authors Natasha Van Bemmel, Jielai Zhang, Jeff Cooke, Anais Möller, Igor Andreoni, Katie Auchettl, David Buckley, Jonathan Carney, Dougal Dobie, James Freeburn, Bruce Gendre, Vanshika Kansal, Itumeleng Monageng, Arne Rau, Nikita Rawat, Mark Suhr, Edward N. Taylor
Solar and Stellar Astrophysics
Investigating episodic mass loss in evolved massive stars IV. Comprehensive analysis of dusty red supergiants in NGC 6822, IC 10, and WLM
E. Christodoulou, S. de Wit, A.Z. Bonanos et al. (+6 more)
Mass loss shapes the fate of massive
stars; however, the physical mechanism causing it remains uncertain. We present a comprehensive analysis of seven red supergiants, for which we searched evidence of episodic mass loss, in three low-
metallicity galaxies: NGC~6822, IC~10, and WLM. Initially, the spectral classification of their optical spectra was refined and compared to previous reported classifications, finding four sources that display spectral variability. We derived the physical properties of five of them using the marcs atmospheric models corrected for nonlocal thermal
equilibrium effects to measure
stellar properties from our new near-infrared spectra, such as the effective temperature, surface
gravity,
metallicity, and microturbulent velocity. Additional empirical and theoretical methods were employed to calculate effective temperatures, finding consistent results. We constructed optical and infrared light curves, discovering two targets in NGC~6822 with photometric variability between 1 and 2.5 mag in amplitude in r and ~ 0.5 mag in the mid-infrared. Furthermore, we discovered a candidate-dimming event in one of these sources. Periods for three red supergiants were determined using epoch photometry, which were consistent with the empirical estimations from literature period-luminosity relations. Our comprehensive analysis of all the available data for each target provides evidence for episodic mass loss in four red supergiants.
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All authors E. Christodoulou, S. de Wit, A.Z. Bonanos, G. Muñoz-Sanchez, G. Maravelias, A. Ruiz, K. Antoniadis, D. García-Álvarez, M.M. Rubio Díez
High Energy Astrophysical Phenomena
The 2024 July 16 Solar Event: A Challenge To The Coronal Mass Ejection Origin Of Long-Duration Gamma-Ray Flares
Alessandro Bruno, Melissa Pesce-Rollins, Silvia Dalla et al. (+3 more)
We present a multi-spacecraft analysis of the 2024 July 16 Long-Duration Gamma-Ray
Flare (LDGRF) detected by the Large Area
Telescope on the
Fermi satellite. The measured >100 MeV $\gamma$-ray emission persisted for over seven hours after the
flare impulsive phase, and was characterized by
photon energies exceeding 1 GeV and a remarkably-hard parent-
proton spectrum. In contrast, the phenomena related to the coronal mass ejection (CME)-driven shock linked to this eruption were modest, suggesting an inefficient
proton acceleration unlikely to achieve the energies well-above the 300 MeV pion-production threshold to account for the observed $\gamma$-ray emission. Specifically, the CME was relatively slow (~600 km/s) and the accompanying interplanetary type-II/III
radio bursts were faint and short-duration, unlike those typically detected during large events. In particular, the type-II emission did not extend to kHz frequencies and disappeared ~5.5 hours prior to the LDGRF end time. Furthermore, the associated
solar energetic particle (SEP) event was very weak, short-duration, and limited to a few tens of MeV, even at magnetically well-connected spacecraft. These findings demonstrate that a very-fast CME resulting in a high-energy SEP event is not a necessary condition for the occurrence of LDGRFs, challenging the idea that the high-energy $\gamma$-ray emission is produced by the back-precipitation of shock-accelerated ions into the
solar surface. The alternative origin scenario based on local particle trapping and acceleration in large-scale coronal loops is instead favored by the observation of
giant arch-like structures of hot
plasma over the source region persisting for the entire duration of this LDGRF.
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All authors Alessandro Bruno, Melissa Pesce-Rollins, Silvia Dalla, Nicola Omodei, Ian G. Richardson, James M. Ryan
High Energy Astrophysical Phenomena
Tidal disruption events with SPH-EXA: resolving the return of the stream
Noah Kubli, Alessia Franchini, Eric R. Coughlin et al. (+4 more)
In a
tidal disruption event (TDE), a
star is disrupted by the
tidal field of a massive black hole, creating a debris stream that returns to the black hole, forms an
accretion flow, and powers a luminous
flare. Over the last few decades, several numerical studies have concluded that shock-induced dissipation occurs as the stream returns to pericentre (i.e., pre-self-intersection), resulting in efficient circularisation of the debris. However, the efficacy of these shocks is the subject of intense debate. We present high-resolution simulations (up to 10^10 particles) of the disruption of a
solar-like
star by a 10^6M_sun black hole with the new, GPU-based, smoothed-particle hydrodynamics code SPH-EXA, including the relativistic apsidal precession of the
stellar debris orbits; our simulations run from initial disruption to the moment of stream self-intersection. With 10^8 particles - corresponding to the highest-resolution SPH simulations of TDEs in the pre-existing literature - we find significant, in-plane spreading of the debris as the stream returns through pericenter, in line with previous works that suggested this is a significant source of dissipation and luminous emission. However, with increasing resolution this effect is dramatically diminished, and with 10^10 particles there is effectively no change between the incoming and the outgoing stream widths. Our results demonstrate that the paradigm of significant dissipation of kinetic energy during pericentre passage is incorrect, and instead it is likely that debris circularisation is mediated by the originally proposed, stream-stream collision scenario.
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All authors Noah Kubli, Alessia Franchini, Eric R. Coughlin, C. J. Nixon, Sebastian Keller, Pedro R. Capelo, Lucio Mayer
Astrophysics of Galaxies
The chemical DNA of the Magellanic Clouds IV. Unveiling extreme element production: the Eu abundance in the Small Magellanic Cloud
Samuele Anoardo, Alessio Mucciarelli, Marco Palla et al. (+3 more)
In this study we investigate the chemical enrichment of the rapid
neutron-capture process in the Small Magellanic Cloud (SMC). We measure [Eu/Fe] abundance ratios in 209
giant stars that are confirmed members of the SMC, providing the first extensive
dataset of Eu abundances in this
galaxy across its full
metallicity range, spanning more than 1.5 dex. We compare Eu abundances with those of Mg and Ba to evaluate the efficiency of the r-process relative to $\alpha$-capture and s-process nucleosynthesis. The SMC shows enhanced [Eu/Fe] values at all
metallicities (comparable with the values measured in the Milky Way), with a clear decline as [Fe/H] increases (from $\sim$ -1.75 dex to $\sim$ -0.5 dex), consistent with the onset of Type Ia
supernovae. In contrast, [Eu/Mg] is enhanced by about +0.5 dex at all [Fe/H], significantly above the values observed in Milky Way
stars, where [Eu/Mg] remains close to
solar, reflecting comparable production of r-process and $\alpha$-capture elements. Moreover, [Ba/Eu] increases with
metallicity, beginning at [Fe/H] $\approx$ -1.5 dex, namely at a lower
metallicity with respect to the Milky Way, where [Ba/Eu] starts to increase around [Fe/H] $\approx$ -1 dex. Our findings suggest the SMC has a higher production of Eu (with respect to the $\alpha$-elements) than the Milky Way but in line with what observed in other
dwarf systems within the Local Group. We confirm that
galaxies with
star formation efficiencies lower than the Milky Way have high [Eu/$\alpha$], probably indicating a stronger efficiency of the delayed sources of r-process at low
metallicities.
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All authors Samuele Anoardo, Alessio Mucciarelli, Marco Palla, Lorenzo Santarelli, Carmela Lardo, Donatella Romano
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Study of neutrino spin oscillations in a gravitational field with a differential equations method
Mridupawan Deka and Maxim Dvornikov
In this work, we employ Ordinary Differential Equation solution method to study
neutrino spin oscillations in the case when they are gravitationally scattered off a rotating Kerr black hole. Previously, this problem involved the integral solution of the Hamilton-Jacobi equation. We analyze the consistency of these two methods.
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High Energy Astrophysical Phenomena
Effects of Coronal Mass Ejection on PSR J1022+1001 and Possible Mode Change of PSR J2145-0750 in the InPTA DR2
Shaswata Chowdhury, M. A. Krishnakumar, Manjari Bagchi et al. (+27 more)
The Indian
Pulsar Timing Array (InPTA) has recently published its second data release (DR2), comprising the timing analysis of seven years of data on 27 millisecond
pulsars (MSPs), observed simultaneously in the 300-500 MHz (band 3) and 1260-1460 MHz (band 5), using the upgraded
Giant Metrewave
Radio Telescope (uGMRT). The low-frequency data, particularly in band 3, is highly sensitive to propagation effects such as dispersion measure (DM) fluctuations, which can be imprints of some astrophysical phenomena (scientific outliers). Here, we analyze the two outliers of possible astrophysical origin coming from the band 3 DM time series of two
pulsars: PSR J1022+1001, with an ecliptic latitude of -0.06 degree, and PSR J2145-0750, one of the brightest MSPs, with multi-component profile morphology. Our study reveals compelling evidence for a coronal mass ejection (CME) event traced in the data of PSR J1022+1001, and reports evidence for a potential mode-changing event in PSR J2145-0750. By contrasting these two cases, we show that DM fluctuations due to CME interacions and intrinsic mode-changing events produce distinct observational signatures, enabling a physically informed classification of scientific outliers in PTA
datasets. Extending the analyses presented here to the full sample of InPTA-DR2
pulsars is expected to reveal additional CME events, and possible mode-changing events. Such detections will not only improve our understanding of
solar and
pulsar magnetospheric
plasma interactions but will also enable more accurate modelling of DM variations, leading to improved
pulsar timing solutions, which are crucial for high-precision
Pulsar Timing Array (PTA) science.
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All authors Shaswata Chowdhury, M. A. Krishnakumar, Manjari Bagchi, Bhal Chandra Joshi, Nobleson K., Jibin Jose, Shantanu Desai, Manpreet Singh, Vaishnavi Vyasraj, Kuldeep Meena, Amarnath, Manoneeta Chakraborty, Shubham Kala, Debabrata Deb, Zenia Zuraiq, Arul Pandian B, Neelam Dhanda Batra, Churchil Dwivedi, Sushovan Mondal, Avinash Kumar Paladi, Kaustubh Rai, Abhimanyu Susobhanan, Adya Shukla, Aman Srivastava, Mayuresh Surnis, Hemanga Tahbildar, Keitaro Takahashi, Pratik Tarafdar, Prabu Thiagaraj, Kunjal Vara
Cosmology and Nongalactic Astrophysics
Hybrid Physical-Neural Simulator for Fast Cosmological Hydrodynamics
Arne Thomsen, Tilman Tröster and François Lanusse
Cosmological field-level inference requires differentiable forward models that solve the challenging dynamics of gas and dark matter under hydrodynamics and
gravity. We propose a hybrid approach where gravitational forces are computed using a differentiable particle-mesh solver, while the hydrodynamics are parametrized by a neural network that maps local quantities to an effective pressure field. We demonstrate that our method improves upon alternative approaches, such as an Enthalpy Gradient Descent baseline, both at the field and summary-statistic level. The approach is furthermore highly data efficient, with a single reference simulation of cosmological structure formation being sufficient to constrain the neural pressure model. This opens the door for future applications where the model is fit directly to observational data, rather than a training set of simulations.
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Astrophysics of Galaxies
The magnetic fields of the dusty nuclei and molecular outflows of Arp 220
Enrique Lopez-Rodriguez, Josep M. Girart, Miguel Pérez-Torres et al. (+5 more)
Galaxy mergers trigger starburst activity and
galactic outflows that enrich the circumgalactic medium, profoundly impacting
galaxy evolution. These phenomena are intrinsically linked to the physical conditions of the medium, which is permeated by
magnetic (B) fields affecting its transport and dynamics. Here, we spatially resolve, $0.24$" (96 pc), the B-fields in the dusty and molecular
outflows of Arp 220, the closest ($78$ Mpc) Ultra-Luminous Infrared
Galaxy hosting two interacting
nuclei, denoted as East and West. We perform ALMA $870~\mu$m
dust continuum polarization and CO(3-2) emission line polarization, and report the first detection of CO(3-2) emission line polarization through the Goldreich-Kylafis effect in an
outflow.
Dust polarization shows that Arp 220 E has a spiral-like B-field on the disk with a linear polarization fraction of $0.4\pm0.1$% that may produce the detected circular polarization passing through foreground aligned
dust grains. Arp 220 W reveals a B-field parallel to the red- and blueshifted
outflows in both the
dust and emission line polarization maps. The
outflows show a
dust polarization of $0.2$%, while the CO(3-2) emission line polarization is $1-2$% at $4-6\sigma$ significance across independent velocity channels. A highly polarized ($3-5$%) dusty bridge has a B-field orientation of $\sim110^{\circ}$ connecting both
nuclei. Mean B-field strengths of $1.6$ mG and $8$ mG for the blue- and redshifted
outflows, respectively, are estimated. These strong B-fields are attributed to amplification by compression in
nuclear clouds and
supernova remnants. This amplified B-field is likely sustained by the turbulent kinetic energy in the
outflow and may be critical in directing the transport of metals and
cosmic rays into the circumgalactic medium.
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All authors Enrique Lopez-Rodriguez, Josep M. Girart, Miguel Pérez-Torres, Mar Mezcua, Gemma Busquet, Rubén Herrero-Illana, Antxon Alberdi, José M. Torrelles
High Energy Astrophysical Phenomena
A Star's Death by a Thousand Cuts: The Runaway Periodic Eruptions of AT2023uqm
Yibo Wang, Tingui Wang, Shifeng Huang et al. (+37 more)
Stars on bound orbits around a supermassive black hole may undergo repeated partial
tidal disruption events (rpTDEs), producing periodic
flares. While several candidates have been suggested, definitive confirmation of these events remains elusive. We report the discovery of AT2023uqm, a
nuclear transient that has exhibited at least five periodic optical
flares, making it only the second confirmed case of periodicity after ASASSN-14ko. Uniquely, the
flares from AT2023uqm show a nearly exponential increase in energy–a "runaway" phenomenon signaling the
star's progressive destruction. This behavior is consistent with rpTDEs of low-mass, main-sequence
stars or evolved
giant stars. Multiwavelength observations and spectroscopic analysis of the two most recent
flares reinforce its interpretation as an rpTDE. Intriguingly, each
flare displays a similar double-peaked structure, potentially originating from a double-peaked mass fallback rate or two discrete collisions per orbit. The extreme ratio of peak separation to orbital period draws
attention to the possibility of a
giant star being disrupted, which could be distinguished from a low-mass main-sequence
star by its future mass-loss
evolution. Our analysis demonstrates the power of rpTDEs to probe the properties of disrupted
stars and the physical processes of
tidal disruption, though it is currently limited by our knowledge of these events. AT2023uqm emerges as the most compelling rpTDE thus far, serving as a crucial framework for modeling and understanding these phenomena.
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All authors Yibo Wang, Tingui Wang, Shifeng Huang, Jiazheng Zhu, Ning Jiang, Wenbin Lu, Rongfeng Shen, Shiyan Zhong, Dong Lai, Yi Yang, Xinwen Shu, Tianyu Xia, Di Luo, Jianwei Lyu, Thomas Brink, Alex Filippenko, Weikang Zheng, Minxuan Cai, Zelin Xu, Mingxin Wu, Xiaer Zhang, Weiyu Wu, Lulu Fan, Ji-an Jiang, Xu Kong, Bin Li, Feng Lin, Ming Liang, Wentao Luo, Jinlong Tang, Zhen Wan, Hairen Wang, Jian Wang, Yongquan Xue, Dazhi Yao, Hongfei Zhang, Wen Zhao, Xianzhong Zheng, Qingfeng Zhu, Yingxi Zuo
High Energy Astrophysical Phenomena
The $N_H$ Distribution of Hard X-ray Selected AGN in the NEP Field
Samantha Creech, Francesca Civano, Daniel R. Wik et al. (+9 more)
X-ray surveys are one of the most unbiased methods for detecting Compton Thick (CT; $N_{{\mathrm{H}}} \geq 10^{24}$ cm$^{-2}$) AGN, which are thought to comprise up to $60\%$ of AGN within $z \lesssim 1.0$. These CT AGN are often difficult to detect with current instruments, but the X-ray data within the JWST-North Ecliptic Pole (NEP) Time Domain Field (TDF) present a unique opportunity to study faint and obscured AGN. The NEP contains the deepest NuSTAR survey to date, and Zhao et al. (2024) detected 60 hard X-ray sources from the combined exposure of NuSTAR's Cycle 5 and 6 observations. In this work, we utilize the NuSTAR Cycle 5+6+8+9 data and simultaneous XMM-Newton observations in order to perform the first spectroscopic analysis of the 60-source catalog. We present this analysis and measure the $N_{{\mathrm{H}}}$ distribution of the sample. We measure an observed CT fraction of $0.13_{-0.04}^{+0.15}$ down to an observed $8-24$ keV flux of $6.0 \times 10^{-14}$ erg/s/cm$^{2}$, and we correct our analysis for absorption bias to estimate an underlying CT fraction of $0.32_{-0.08}^{+0.23}$. The derived obscuration distribution and CT fraction are consistent with population synthesis models and previous surveys.
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All authors Samantha Creech, Francesca Civano, Daniel R. Wik, Ross Silver, Xiurui Zhao, Rafael Ortiz III, Tonima Ananna, Normal A. Grogin, Rolf Jansen, Anton M. Koekemoer, Christopher N.A. Willmer, Rogier A. Windhorst
Earth and Planetary Astrophysics
Combined Orbital and Thermal Evolution of Oort Cloud Comets
Adam Parhi and Dina Prialnik
We present a fully integrated model of comet
evolution that couples thermal and compositional processes with dynamical processes continuously, from formation to present-day activity. The combined code takes into account changes in orbital parameters that define the heliocentric distance as a function of time, which is fed into the thermal/compositional
evolution code. The latter includes a set of volatile species, gas flow through the porous interior, crystallization of amorphous ice, sublimation and refreezing of volatiles in the pores. We follow the
evolution of three models, with radii of 2, 10 and 50 km for 4.6 Gyr, through different dynamical epochs, starting in the vicinity of Neptune, moving to the Oort Cloud and after a long sojourn there, back inward to the planetary region. The initial composition includes a mixture of CO, CO2 ices, amorphous water ice with trapped CO and CO2, and
dust.We find that the CO ice is completely depleted in the small object, but preserved in the larger ones from a depth of 500 m to the center, while the CO2 and the amorphous ice are entirely preserved. Of crucial importance is the change in CO abundance profiles during the cooling phase, as the objects migrate to the OC. Upon return from the Oort Cloud, the activity is driven by CO sublimation at large heliocentric distances (up to 50 au), by CO2 inward of 13 au and by gas released from crystallizing amorphous ice at about 7 au. We test the effect of radioactive heating by long-lived isotopes and find that it is negligible. Considering sub-
solar temperatures and limited active areas, we show that CO2 production rates can exceed the detection limit as far out as 25 au.
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Cosmology and Nongalactic Astrophysics
A test of invariance of halo surface density for FIRE-2 simulations with cold dark matter and self-interacting dark matter
Sujit K. Dalui and Shantanu Desai
Numerous observations have shown that the dark matter
halo surface density, defined as the product of core radius and
halo central density of cored dark matter
haloes is nearly constant and independent of
galaxy mass over a whole slew of
galaxy types. Here we calculate the surface density in cold dark matter(CDM) and self-interacting dark matter (SIDM) models including
baryons, as well as SIDM without
baryons, for
dwarf galaxies of masses $\approx 10^{10} M_{\odot}$ using mock catalogs obtained from simulations as part of the Feedback In Realistic Environments project. We find that the dark matter surface density and column density are nearly constant for CDM and SIDM for this mass range. The
halo surface density obtained from the Burkert profile fit is consistent with
galactic-scale observations within $1\sigma$. We also computed the empirical scaling relations between the central surface density and maximum velocity using the best-fit dark matter profiles, and found that they agree with observations of Milky Way and M31
dwarfs.
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Astrophysics of Galaxies
CROCODILE-DWARF: Assembly and Kinematics of Field Dwarf Galaxies with GADGET4-OSAKA
Kazuki Tomaru, Yuri Oku, Daisuke Toyouchi et al. (+1 more)
We present results from CROCODILE-
DWARF, a new suite of cosmological zoom-in hydrodynamic simulations of isolated field
dwarf galaxies with
halo masses of $\sim10^{10}\,M_\odot$ at $z=0$, performed with the GADGET4-OSAKA code. The simulations include detailed modeling of
star formation, chemical enrichment, and
supernova feedback using the CELib and Grackle libraries, achieving baryonic resolutions of $\sim2\times10^3\,M_\odot$. Our study focuses on how assembly history governs the structural and kinematic diversity of
dwarf galaxies within the $\Lambda$CDM framework. The simulated
galaxies reproduce the observed
stellar-to-
halo mass, mass–
metallicity, and size–mass relations for nearby
dwarf galaxies, including those of the Local Group, yielding
stellar masses of $\sim10^7\,M_\odot$. The
galaxies display a broad range of rotational support, where gas is generally more rotationally supported than
stars. Differences in morphology and kinematics primarily reflect variations in
halo assembly timescales and merger activity. Early-assembling, high-concentration
halos form
stars efficiently and become gas-poor by $z=0$, while late-assembling, low-concentration
halos remain gas-rich due to delayed
star formation and rejuvenated gas
accretion. We find a trend between rotational support and the cumulative merger mass fraction, providing tentative evidence that dynamical heating induced by mergers plays a role in shaping the kinematic diversity. In some cases, late-time mergers induce the formation of extended gas disks by delivering fresh gas and angular momentum. These results demonstrate that it is assembly history, rather than
halo mass alone, that shapes the present-day kinematic and morphological diversity of
dwarf galaxies.
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All authors Kazuki Tomaru, Yuri Oku, Daisuke Toyouchi, Kentaro Nagamine
Instrumentation and Methods for Astrophysics
A summary of instruments proposed for observing pulsating variables from the Mt. Abu Observatory
Anwesh Kumar Mishra, Deekshya Roy Sarkar, Prachi Prajapati et al. (+3 more)
Pulsating variables play a significant role in shaping modern astronomy. Presently it is an exciting era in observational study of variable
stars owing to surveys like OGLE and TESS. The vast number of sources being discovered by these surveys is also creating opportunities for 1-2m class
telescopes to provide follow-up observations to characterize these. We present some initial observations of type-II cepheids from the Mt. Abu observatory and highlight the need for dedicated observing runs of pulsating variables. We also present optical designs for several suggested instruments for the Mt. Abu observatory that will contribute towards this goal. We present designs that are fairly simple and yet take due benefit of the unique
telescopes and facilities present at the observatory.
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All authors Anwesh Kumar Mishra, Deekshya Roy Sarkar, Prachi Prajapati, Alka Singh, Prashanth K. Kasarla, Shashikiran Ganesh
Earth and Planetary Astrophysics
In space there will be no need to scream – Limits to the presence of giant planets in the $\zeta^2$ Ret system
A. Suárez Mascareño
The search for life beyond our
Solar system has been a long and difficult endeavour. The majority of current efforts are focused on the potential detection of biosignatures. However, their detection and interpretation are extremely challenging. Technosignatures appear as an attractive alternative, given their expected univocal interpretation. In recent years, the number of publications discussing them have skyrocketted, both in their more rigurous and speculative sides. In this article, we explore the 28.8 years of archival radial velocity data of $\zeta^2$ Ret with the aim of detecting the proposed
giant planet Calpamos, suspected source of a signal of technological origin. We performed a global model fitting the radial velocity data along with activity indicators and modelled the
stellar magnetic cycle and rotation. The analysis rules out the presence of the proposed
planet, as well as of any other
planets more massive than 2-20 $\mathrm{M}_\oplus$ $m_{p}$ sin $i$, depending on orbital period. We show that the previously identified long-period RV signal is definitively caused by the
magnetic cycle of the
star.
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Astrophysics of Galaxies
The Spiral Pattern Speed in the Milky Way Galaxy
Vadim V. Bobylev, Anisa T. Bajkova and Anton A. Smirnov
For a sample of masers, the basic kinematic equations were solved by including the
Galactic rotation parameters and the peculiar velocity of the Sun as the unknown variables. Based on spectral analysis, the following estimates were obtained: $|f|_{R,\theta}=(7.0,5.1)\pm(1.2,1.4)$ km s$^{-1}$ and the corresponding wavelengths $\lambda_{R,\theta}=(1.9,1.7)\pm(0.4,0.7)$ kpc, as well as $\chi_\odot=-140^\circ\pm15^\circ$. The presence of periodic perturbations in the vertical velocities of masers with an amplitude of $|f|_W=3.1\pm1.4$ km s$^{-1}$ and a wavelength of $\lambda=1.9\pm0.8$ kpc was confirmed. It is shown that the velocities $f_R$ and $f_\theta$ can have both the same and different signs. Therefore, we obtained a large scatter of estimates. Thus, if $f_R$ and $f_\theta$ have the same signs, then $\Omega_p=25.8\pm2.0$ km s$^{-1}$ kpc$^{-1}$ and $R_{cor}=9.1\pm0.8$ kpc. And when $f_R$ and $f_\theta$ have different signs, then $\Omega_p=35.4\pm2.0$ km s$^{-1}$ kpc$^{-1}$ and $R_{cor}=6.8\pm0.8$ kpc.
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Solar and Stellar Astrophysics
The dance of dust: Investigating young stellar object dipper variability
A. Empey, R. Garcia Lopez, A. Natta et al. (+4 more)
The dipper subclass of YSOs are characterised by frequent dips in their light curves. Irregular dippers do not show periodic signatures and have dips accounting for significant proportions of their photospheric flux. Given the short timescales on which these dips occur, their driving mechanisms are linked to the inner circumstellar disc dynamics. We present the first multi-epoch analysis of 16 irregular dippers observed with X-Shooter. Investigating the properties of their dips, and in particular the analysis of the
dust characteristics, we aim to understand the root of their variability, and get a glimpse of the inner disc behaviour. We employed a novel approach to measure the properties of the dips, by combining class III templates with
Gaia photometry to construct the intrinsic photospheres. We measured several dip properties including the depth of the dips, near-infrared (NIR) excesses, and their optical depths as a function of wavelength. We record 20 significant dips that range in their dip properties and show no relation to one another. In almost all cases, the low optical depths and small NIR excesses are observed. Comparison of their optical depths with grain opacity models show that the dips can be explained by the presence of
dust substructures containing processed grains obscuring their photospheres and/or their discs. These grain distributions can have maximum sizes as large as 20$\mu m$ and in many cases have almost grey-like extinction, while some require a strong scattering component. The findings highlight the extent of the irregularity of dippers, but also link it to the
dust dynamics in the inner regions of circumstellar discs. The
dust substructures causing the variability require processed
dust grains to be lifted above the disc into the line of sight. Possible lifting mechanisms including disc winds, unstable
accretion columns, and disc warps are discussed.
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All authors A. Empey, R. Garcia Lopez, A. Natta, C.F. Manara, M. Benisty, R. Claes, P. McGinnis
Astrophysics of Galaxies
Neon is an inhibitor of CO hydrogenation in pre-stellar core conditions
Basile Husquinet, Julie Vitorino, Olli Sipilä et al. (+2 more)
Neon (Ne) is the fifth most abundant element in the Universe. Because it is chemically inert, it has never been considered in astrochemical models that studied molecular
evolution. In the cold dark environments of pre-
stellar cores, where the temperatures are below 10 K, Ne can condense onto the surface of interstellar grains. We investigated the effect of Ne on the production of formaldehyde (H$_2$CO) and methanol (CH$_3$OH) through carbon monoxide (CO) hydrogenation on different cold surfaces. We highlight its role in conditions corresponding to pre-
stellar cores. In an ultra-high
vacuum system, we conducted two types of experiments. The first experiment involved the co-deposition of CO and H atoms with or without Ne. The second experiment involved depositing a monolayer of CO and separately a monolayer of Ne (or vice versa), followed by bombarding the layers with hydrogen atoms. Additionally, we used a gas-grain chemical code to simulate a pre-
stellar core and determine where Ne can affect the chemistry. The presence of Ne on the surface significantly inhibits CO hydrogenation at temperatures below 12 K. In the co-deposition experiments, we observed a 38% decrease in the H$_2$CO production at 11 K when the quantity of Ne in the mixture was lower than a monolayer. At 10 K and with one monolayer in the mixture, the production decreased to 77%, and it reached 91% for a few monolayers of Ne in the mixture at 9 K. While the decrease in CH$_3$OH formation is still notable, it is less pronounced: 43% at 11 K, 61% at 10 K, and 77% at 9 K. Experiments with stacked layers revealed that the CO layer decay varies slightly when the Ne layer is positioned above or below it. This observation indicates that Ne and CO create a mixture in which Ne can diffuse and stabilize at the surface, which isolates CO molecules from the accreting H atoms.
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All authors Basile Husquinet, Julie Vitorino, Olli Sipilä, Paola Caselli, François Dulieu
Astrophysics of Galaxies
Optimizing Long-term Variability of AGN Light Curves. I. A Case Study with ZTF Observations in the EGS Field
Jiaqi Lin, Zhen-Ya Zheng, Bin Ma et al. (+5 more)
Optical variability is a key observational probe for studying the
accretion dynamics and central engine physics of Active
Galactic Nuclei (AGNs). The quality and completeness of light curves have a direct impact on variability studies, particularly for faint AGNs and high-
redshift AGNs. To improve the quality of long-term light curves for AGNs, we bin and stack multi-epoch images balancing the image depths and temporal resolution. As a case study, we apply this method to Zwicky Transient Facility (ZTF) observations in the Extended Groth Strip (EGS) field, where the overlapping region covers an area of about 370 arcmin$^2$ and includes $g$-band and $r$-band data taken from March 2018 to December 2024. The co-added images are approximately 2.0 to 2.5 magnitudes deeper than the ZTF single-epoch images. With co-added images, we construct light curves for 73 AGNs in the EGS field. Compared to the traditional ZTF light curves, our light curves maintain consistent long-term variability trends but with higher photometric precision. Furthermore, this method can help detect AGNs with weak variability which are missed from the traditional ZTF data due to the noisy light curves or below the detection limit in ZTF's single-epoch exposure. Among the 73 AGNs, the majority exhibit a bluer-when-brighter (BWB) trend on long-term timescales, which is consistent with previous studies. This work offers insights for optimizing AGN light curves in both current and upcoming all-sky time-domain surveys.
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All authors Jiaqi Lin, Zhen-Ya Zheng, Bin Ma, Lin Long, Yangfan Xie, Pu Lin, Ruqiu Lin, Xiang Ji
Astrophysics of Galaxies
Joint Analysis of Optical, Near-Infrared And Mid-Infrared Variability of 4 Quasars at Redshift < 1
Lin Long, Zhen-ya Zheng, Ning Jiang et al. (+8 more)
Amid rapid advances in time-domain astronomy, multi-wavelength (e.g., optical and infrared) time-domain studies of
quasars remain scarce. Here we present a systematic analysis of four
quasars initially selected by their Ks-band variability amplitudes in the VISTA Variables in the Vía Láctea Survey (VVV/VVVX). For these objects, we obtain complementary optical light curves from Pan-STARRS1 (PS1) and the Zwicky Transient Facility (ZTF), and W1-band light curves from the Wide-field Infrared Survey Explorer (WISE). We perform correlation analysis to study the time lags between different bands, which may be directly related to the size of the
dust torus. After correcting for infrared flux contamination from the
accretion disk and accounting for the
redshift effect, we measure the Ks-optical and W1-optical lags for the targets VVV J1834-2925 and VVV J1845-2426. Using typical sublimation temperatures and reverberation time lags, we obtain a graphite-to-silicate grain size ratio of $\frac{a_C}{a_S}\sim$ 0.4. Through SED fitting, we determine the luminosities of these
quasars and find that their
dust torus sizes follow the established $R_{dust}-L_{AGN}$ relation reported in previous studies.
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All authors Lin Long, Zhen-ya Zheng, Ning Jiang, Chun Xu, Jiaqi Lin, Fang-Ting Yuan, Chunyan Jiang, Ruqiu Lin, Hai-Cheng Feng, Hengxiao Guo, Xiang Ji
Astrophysics of Galaxies
XRISM Observations of The Prototypical Cold Front in Abell 3667
Yuki Omiya, Yuto Ichinohe, Kazuhiro Nakazawa et al. (+13 more)
We present high-resolution X-ray spectroscopy of the merging
galaxy cluster Abell 3667 with XRISM/Resolve. Two observations, targeting the cluster X-ray core and the prototypical cold front, were performed with exposures of 105 ks and 276 ks, respectively. We find that the gas in the core is blueshifted by $v_z\sim-200$ km s$^{-1}$ relative to the brightest cluster
galaxy, while the low-
entropy gas inside the cold front is redshifted by $v_z\sim 200$ km s$^{-1}$. As one moves further off-center across the front, the line-of-sight (LoS) velocity changes significantly, by $\Delta v_z=535^{+167}_{-154}$ km s$^{-1}$, back to the value similar to that in the core. There are no significant LoS velocity gradients perpendicular to the cluster
symmetry axis. These features suggest that the gas forming the cold front is flowing in the plane oriented along the LoS, supporting an offset merger scenario in which the main cluster has passed in front of the subcluster and induced rotation of the core gas in the plane perpendicular to the sky. The region just inside the front exhibits the largest LoS velocity dispersion seen across two pointings, $\sigma_z\sim420$ km s$^{-1}$, which can be interpreted as a developing
turbulence or a projection of the LoS velocity shear within the front. The large LoS velocity jump across the cold front, combined with the lack of Kelvin-Helmholtz instability on the surface of the front, suggests some mechanism to suppress it. For example, a
magnetic field with $B>5\,\mu$G is required if the cold front is stabilized by
magnetic draping.
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All authors Yuki Omiya, Yuto Ichinohe, Kazuhiro Nakazawa, Hisamitsu Awaki, Dominique Eckert, Yutaka Fujita, Isamu Hatsukade, Maxim Markevitch, François Mernier, Ikuyuki Mitsuishi, Naomi Ota, Aurora Simionescu, Yuusuke Uchida, Shutaro Ueda, Irina Zhuravleva, John Zuhone