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Physics Astrophysics

astro-ph Watch Astrophysics

Thursday 7 May

Earth and Planetary Astrophysics

Taxonomy of 14042 asteroids from Gaia DR3 reflectance spectra

Fernando Tinaut-Ruano, Benoit Carry, Marjorie Galinier et al. (+2 more)

Asteroid reflectance spectra provide key constraints on surface composition. Gaia DR3 enables the study of 60,518 asteroids through NUV to visible reflectance spectra. We aim to classify asteroids using Gaia DR3 spectra and provide a homogeneous framework. Owing to systematics affecting Gaia DR3 data, direct comparison with previous taxonomies has to be taken with caution; thus, we developed a classification scheme tailored to Gaia and linked the resulting taxa to established classes. We selected the highest-quality spectra using Gaia DR3 quality flags and applied uncertainty thresholds to mitigate spectral artifacts, retaining over one-third of the original sample at the least noisy wavelength. To improve compositional discrimination, we included albedo, reducing the final sample to about one-fourth of its initial size. We then iteratively applied dimensionality reduction and clustering to identify the spectral taxa. We classified 14,042 asteroids into 13 taxonomic classes: A, B, C, D, E, F, G, K, L, M, P, S, and V, representing an increase of three compared to the number of objects classified in previous spectral classifications. The largest relative increase is found for the K class. The inclusion of NUV wavelengths allows the separation of B and F types within the C-complex and facilitates the identification of G types. The dynamical distribution follows expected trends, with Stypes dominating the inner and middle Main Belt, C-complex asteroids prevalent in the outer Main Belt, and D types beyond. We present a taxonomical classification of 14,042 asteroids based on Gaia DR3 reflectance spectra. NUV coverage is critical for disentangling primitive classes within the C-complex. Although artifacts in Gaia DR3 require caution when comparing median spectra with other datasets, this classification provides a robust reference for future Gaia releases, with larger observed samples.
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All authors Fernando Tinaut-Ruano, Benoit Carry, Marjorie Galinier, Max Mahlke, Alexey Sergeyev

Instrumentation and Methods for Astrophysics

The Hubble Advanced Spectral Product (HASP) Program

John Debes, Ravi Sankrit, Travis Fischer et al. (+39 more)

The Hubble Advanced Spectral Products (HASP) program is designed to robustly coadd Cosmic Origins Spectrograph (COS) and Space Telescope Imaging Spectrograph (STIS) spectra within the Mikulski Archive for Space Telescopes (MAST) in an automated fashion such that coadds are available for new data or archival data with updated calibrations. For each target within a visit or program, HASP employs a meticulous multi-stage filtering process to ensure data quality and creates coadded products for all central wavelengths (CENWAVEs) within specific gratings, as well as combined products using different gratings and instruments. The project also emphasizes making the code accessible to the user community for custom coaddition. As calibrations improve and new data are added to the archive, HASP products are re-created automatically so that they represent the best reduction of a given visit or program. Automated coadditions like those achieved by HASP can significantly enhance the combination of different CENWAVES, increase signal-to-noise ratios, and increase wavelength coverage. These properties make HASP a vital resource for astronomers using archival spectroscopic data from HST.
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All authors John Debes, Ravi Sankrit, Travis Fischer, Elaine Frazer, Alec Hirschauer, Kate Rowlands, Matthew Burger, Robert Swaters, Robert Jedrzejewski, Sierra Gomez, Leonardo Dos Santos, Svea Hernandez, Lauren Miller, Anna Payne, Marc Rafelski, Thomas Wevers, Sara Anderson, Tom Bair, Kathryn Bello, Joleen Carlberg, Brian Charlow, Andrew Cortese, Nadia Dencheva, Tracy Ellis, Ben Falk, Scott Fleming, Peter Forshay, Syed Gilani, Patty Hall, Tim Kimball, Talya Kelley, Richard Kidwell, Jenn Kotler, Aiden Kovacs, Bethan James, Christopher Rahmani, David Rodriguez, Julia Roman-Duval, David Soderblom, Lisa Sherbert, Dan Welty, David Wolfe

Solar and Stellar Astrophysics

The impact of envelope binding energies on the merger rate density of binary compact objects

Cecilia Sgalletta, Guglielmo Costa, Giuliano Iorio et al. (+8 more)

The common envelope (CE) phase plays a key role in the formation of binary compact object systems. Its final outcome strongly depends on the envelope binding energy, but this quantity is often estimated using fitting formulas that are not fully consistent with the underlying stellar evolution models adopted in population-synthesis codes. Here, we investigate envelope binding energies across the most extensive stellar grid considered to date. Our stellar tracks, evolved with PARSEC v2.0, include hydrogen (H) -rich stars with metallicities ranging from $Z = 10^{-11}$ (Population III stars) to $Z = 0.03$, and initial masses between 2 and 2000 M$_\odot$, as well as pure-helium stars with masses from 0.36 to 350 M$_\odot$. We examine the sensitivity of the envelope binding energies to the selected core-envelope boundary definition and to different internal energy source contributions. For H-rich stars, we find that internal energy sources can alter the envelope binding energy by more than an order of magnitude, whereas the core boundary criteria play a secondary role. In contrast, for pure helium stars, the core-boundary criterion becomes the dominant factor. The envelope binding energies derived from different stellar tracks can show deviations of several orders of magnitude, with larger differences for more massive stars and higher metallicities.Finally, by implementing our new envelope binding energy prescriptions into the binary population synthesis code SEVN, we show that the predicted merger rate densities of compact binaries can differ by more than an order of magnitude compared to previous models. Our results highlight the importance of using envelope binding energies that are consistent with the underlying stellar evolution models and caution against extrapolating empirical fits beyond the considered parameter space.
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All authors Cecilia Sgalletta, Guglielmo Costa, Giuliano Iorio, Kendall Shepherd, Francesco Addari, Alessandro A. Trani, Michela Mapelli, Ugo N. di Carlo, Andrea Lapi, Alessandro Bressan, Mario Spera

Solar and Stellar Astrophysics

Radio Continuum and Water Maser Monitoring of the Outburst in HOPS 373: Free-Free Emission Does Not Respond to the Outburst

John Tobin, Doug Johnstone, Greg Herczeg et al. (+5 more)

We present VLA C-band (5~cm) continuum, K-band (1.3~cm) continuum, and water maser (22.235 GHz) monitoring of the protostar HOPS-373. We additionally present the contemporaneous monitoring for 95 sources within the 5~cm field of view for over two years during the peak of the HOPS-373 outburst and an additional epoch in 2026. HOPS-373 is a binary Class 0 protostar located in the Orion star forming region that was found to have a $\sim$4$\times$ luminosity burst from the JCMT Transient Survey and NEOWISE monitoring. We do not find evidence for a change in the free-free emission traced by VLA 5~cm continuum during the peak of its outburst or during the decline. Moreover, the 1.3~cm continuum does not show significant variability between the NE and SW components of the HOPS-373 binary. The water maser emission is highly variable toward HOPS-373, multiple velocity components are detected at different (or the same) times and the maser spots are located close to the 1.3~cm continuum source of HOPS-373-SW. There is tentative evidence for the water maser spots to be propagating away from the source, but there is not a robust connection between the outburst and the observed maser activity. The lack of correlation between outburst and free-free emission from HOPS-373 indicates that the free-free emission may not directly respond to increases in the accretion rate and subsequently the outflow rate. The lack of a link could be due to the outflow mostly being neutral, or there may be offsets in the timescale for the free-free response.
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All authors John Tobin, Doug Johnstone, Greg Herczeg, Jeong-Eun Lee, Ho-Gyu Lee, Carlos Contreras-Pena, Sung-Yong Yoon, Steve Mairs

Cosmology and Nongalactic Astrophysics

On the origin of the environmental dependence of SN Ia magnitudes: A BayeSN view of the ZTF SN Ia DR2

Madeleine Ginolin, Matthew Grayling, Kaisey S. Mandel et al. (+5 more)

Astrophysical variabilities of Type Ia supernovae (SNe Ia), such as their link with their birth environment, are now one of the leading sources of systematic uncertainties on the measurement of the dark energy equation-of-state parameter $w$. Population studies of SNe Ia, using large samples, give precious insights into these variabilities. We analyse a volume-limited subsample of 932 SNe from the ZTF SN Ia DR2 with BayeSN, a hierarchical Bayesian model for SN Ia SEDs. We investigate the distributions of SN Ia light curve parameters and their link with SN environment. Using a new training of BayeSN released in a companion paper, we find a smaller scatter of Hubble residuals compared to SALT. We then investigate the magnitude step, which accounts for the correlation between SN Ia standardised absolute magnitude and host environments. We find a posteriori steps of $0.103\pm0.010$ mag (a $10.1\sigma$ difference from 0) when using global stellar mass as an environmental proxy, and $0.086\pm0.010$ mag ($8.3\sigma$) when using local colour, in accordance with steps computed using SALT light curve fits. This confirms that the large step seen in the ZTF SN Ia DR2 data was not due to the SALT fit or the associated standardisation process. We then investigate the origin of the step, using a BayeSN model which accounts for both an intrinsic magnitude step and differing dust properties with the SN environment. We find a $0.103\pm0.018$ mag ($5.6\sigma$) step in global mass and a $0.085\pm0.019$ mag ($4.5\sigma$) step in local colour. The means of the $R_V$ distribution are similar between different host environments, with $\Delta\mathbb{E}(R_V)\leq0.2$ across all environment proxies, with significances ranging from $0.6\sigma$ to $1.2\sigma$. This is a strong signal of the existence of an intrinsic dependence of SN Ia absolute magnitude on environment.
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All authors Madeleine Ginolin, Matthew Grayling, Kaisey S. Mandel, Maximilian Autenrieth, Benjamin M. Boyd, Aaron Do, Lisa Kelsey, Matthew O'Callaghan

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Decaying spin-3/2 dark matter from baryon number violation

Francesco Costa and Gabriel M. Salla

We explore an uncharted corner of dark matter phenomenology: non-supersymmetric spin-$3/2$ dark matter with baryon number violating interactions. In an effective field theory description, we identify the leading baryonic portal between the spin-$3/2$ state and Standard Model quarks and show that it can account for the observed dark matter abundance through UV freeze-in and Boltzmann-suppressed freeze-in, while the freeze-out region is completely excluded. The resulting phenomenology is distinctive, with relic production controlled by the competition between baryon-violating single-particle processes and baryon-conserving pair production. We map the viable parameter space against indirect detection, direct detection, and LHC monojet bounds, finding strong complementarity between these probes and especially stringent limits when production and decay are tied to the same operator. We also present a dark QCD-like ultraviolet completion in which the spin-$3/2$ particle arises as a composite baryon, naturally generating the effective interactions and mitigating the main theoretical obstacles of elementary higher-spin states. This framework opens a novel and testable connection between baryonic portals, confining dark sectors, and higher-spin dark matter.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Plasma heating during the chiral plasma instability

Balin Armstrong, Andrew J. Long, Károly Seller et al. (+1 more)

The presence of a chiral asymmetry in a relativistic plasma opens a tachyonic instability toward the growth of a helical magnetic field. We study the transfer of energy from the chiral asymmetry into the magnetic field during the development of this chiral plasma instability. We find that there is more energy stored in the initial chiral asymmetry than goes into growing magnetic field and that the excess energy is transferred to the thermal bath. Consequently, we find that the chiral plasma instability is accompanied by a heating of the plasma, and the temperature increase is parametrically $\delta T \sim \mu_5^2 / T$ if the ratio of chemical potential to temperature is small, i.e. $\mu_5/T \ll 1$. We briefly remark on possible observable implications for early universe cosmology.
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All authors Balin Armstrong, Andrew J. Long, Károly Seller, Günter Sigl

High Energy Astrophysical Phenomena

The study of the circumnuclear environment of accreting supermassive black holes with realistic X-ray spectral models

Georgios Dimopoulos, Claudio Ricci and Stéphane Paltani

X-ray spectral modeling is a powerful tool for studying the immediate environment of accreting objects, including supermassive black holes. Several models, either phenomenological or physically driven, have been developed over the past decade to study X-ray spectra, delivering important insights into the properties of circumnuclear material of active galactic nuclei (AGN). Despite the fact that these models are able to reproduce the data well, they often lack realistic geometries, and most of them consist of simplified configurations such as a slab or a torus. We use the ray-tracing code RefleX to generate new spectral models that cover a wide energy range in the X-ray band, adopting a realistic configuration for the surrounding material. We introduce two new table models that are publicly available: 1) the RXToPo model, which features an X-ray source along with a dusty torus and a polar hollow cone; 2) the RXagn1 model, which includes, besides the torus and polar cone, also the accretion disk and the broad line region. Both models were applied to the X-ray spectrum of NGC 424, demonstrating their potential to study sources whose X-ray emission is dominated by reprocessed radiation.
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Astrophysics of Galaxies

Hidden Monsters with SPHEREx I: A goldmine for heavily reddened quasars at cosmic noon

Matthew Stepney, Manda Banerji, Franz E. Bauer et al. (+2 more)

Heavily reddened quasars (HRQs) are luminous, dust-obscured broad-line quasars thought to represent a short-lived phase of intense black hole growth and feedback. Previous studies have been limited by small sample sizes, restricting robust statistical analysis. We expand the sample of the most luminous HRQs to enable population-level studies, connecting their spectral energy distributions (SEDs) to other quasar populations and placing them within an evolutionary sequence of massive galaxy and black hole formation. We assemble multiwavelength broadband photometry for the brightest HRQ candidates (K$_{AB}$ < 18 mag) and select AGN with red near-infrared colours (J-K)$_{AB}$ > 1.6. Using SPHEREx spectrophotometry, we confirm HRQs and determine redshifts. Detailed SED fitting allows comparison with other luminous quasars, including a control sample of hyper-luminous, unobscured Quaia quasars and luminous Hot Dust-Obscured Galaxies (Hot DOGs). We confirm 77 new HRQs with redshifts 1.5 < z < 3.9, dust-corrected optical continuum luminosities log$_{10}(\lambda L_\lambda (3000A)$ [erg/s])>47.0, and line-of-sight extinctions 0.4 < E(B-V) < 1.6 (A$_V$ mag). This more than doubles the known HRQs at z > 1.5, including the first seven at z > 3. A UV excess consistent with scattered quasar emission is detected in 76% of HRQs. We show that HRQs are hot-dust poor compared to blue quasars of similar luminosity and redshift. Their 6um continuum luminosities are systematically fainter at fixed 3000A continuum luminosity relative to blue Quaia quasars, indicating deficiency in both hot and warm dust. These results support a scenario in which HRQs represent a blow-out phase, where strong feedback begins clearing obscuring material from central regions.
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All authors Matthew Stepney, Manda Banerji, Franz E. Bauer, Roberto J. Assef, Guodong Li

Instrumentation and Methods for Astrophysics

Machine Learning Techniques for Astrophysics and Cosmology: Photometric Redshifts

Luca Tortorelli and Daniel Grün

The cosmological redshift of a galaxy's light is inferable from its observable properties in images. Because imaging is much easier to acquire than spectroscopic observations that would allow the identification of distinct line features, this motivates the technique of photometric redshift estimation (photo-$z$). Photo-$z$ has been an early and sustained driver for the utilization of artificial intelligence (AI) in astrophysics, and conversely AI methods are underlying most of the recent advances in photo-$z$. Here we review the diversity of AI methods applied to the photo-$z$ problem over the years in a discriminative way, that is, to regress redshift from photometric observables. We argue that, besides optimization suiting specific applications, this approach has effectively converged. It is limited not by the AI methodology but by the size and substantial systematic uncertainties and selection effects in spectroscopic training samples. In order to progress, either an unobtainable quantity and quality of training data or a more principled approach in using it is required. We thus outline ongoing research of integrating AI in a Bayesian modeling of galaxy data. This comes in the form of generative models for representing the distribution of intrinsic properties and outcomes of telescope observations of the galaxy population.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

The structure of multi-axion solutions to the strong CP problem

Mario Fernández Navarro, Marta F. Zamoro, Marko Pesut et al. (+1 more)

A broad experimental program is targeting the QCD axion band predicted by single-axion solutions to the strong CP problem. Multi-axion theories provide a well-motivated departure from this canonical picture, since additional states generically modify the mass-photon-coupling relation. We investigate the general structure of multi-axion solutions to the strong CP problem and study the different qualitative mass-coupling patterns that arise, including axions to the right of the QCD band, axions in the experimentally accessible region to its left, and scenarios in which the QCD axion band itself is displaced. This general treatment reveals a broad set of phenomenological possibilities that are not captured by more restrictive assumptions. In particular, we identify the structure of Peccei-Quinn symmetry breaking and the relative alignment between the QCD and electromagnetic anomalies as key ingredients determining the location of the axions in parameter space. Combining these ingredients, we derive a general sum rule for $N$-axion systems that incorporates both general PQ breaking and non-universal anomaly coefficients. We apply the framework to the two-axion system and to general multi-axion setups, identifying UV-complete theories in which the different phenomenological regimes arise naturally. Our results motivate an extended axion search program and have implications for our understanding of fundamental physics and the ultraviolet completion of the Standard Model.
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All authors Mario Fernández Navarro, Marta F. Zamoro, Marko Pesut, Xavier Ponce Díaz

Cosmology and Nongalactic Astrophysics

Dark siren cross-correlations and the sensitivity of $H_0$ to methodological choices

Madeline L. Cross-Parkin, Cullan Howlett, Leonardo Giani et al. (+2 more)

Gravitational wave sources act as absolute distance indicators, making them powerful probes of the present-day expansion rate of the Universe, $H_0$. The cross-correlation method combines gravitational wave events with galaxy catalogues to constrain cosmological parameters through their shared large-scale structure. In this work, we investigate how key methodological choices – including covariance treatment, bias parametrisation for galaxies and gravitational wave events, and distance and redshift binning width – affect the inferred value of $H_0$. We also study catalogue incompleteness, showing that selection effects can be incorporated directly into the theoretical prediction, without the need to model the missing population explicitly, a key advantage over the standard galaxy catalogue approach. Our results indicate that, with appropriate modelling choices and a sufficiently large sample of precise gravitational wave events, the systematic biases considered here can be effectively mitigated, highlighting the potential of the cross-correlation method for future dark siren precision cosmology.
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All authors Madeline L. Cross-Parkin, Cullan Howlett, Leonardo Giani, Chris Blake, Tamara M. Davis

Astrophysics of Galaxies

The galaxy ultraviolet luminosity function from $z=7$ to $20$ in the COLIBRE simulations

Shengdong Lu, Carlos S. Frenk, Cedric G. Lacey et al. (+17 more)

JWST has enabled the detection of galaxies in the earliest stages of cosmic history. We compare the ultraviolet luminosity functions (UVLFs) at redshifts $z=7-20$ predicted by a set of new cosmological hydrodynamical simulations, COLIBRE, with observations, including those from JWST. The UV luminosities of COLIBRE galaxies are derived using the radiative transfer code SKIRT, which tracks stellar emission and its processing through the multi-phase interstellar medium and dust distribution predicted by COLIBRE. We find that although COLIBRE is consistent with the observed evolution of the stellar mass function up to $z=12$, its dust-attenuated UVLFs fall systematically below the observations at the bright end: at the number density of $10^{-6}\,\mathrm{Mpc^{-3}\,mag^{-1}}$, the brightest galaxies are underluminous by $\approx 1\,\rm mag$ at $z=7$, increasing to $\approx 2.5\,\rm mag$ at $z=15$. Accounting for observational uncertainties brings the COLIBRE UVLFs closer to the observational data, but does not fully resolve the discrepancy. Ignoring dust attenuation allows COLIBRE to produce sufficiently bright galaxies at $7\lesssim z \lesssim 12$, but at $z=15$, COLIBRE still underpredicts the luminosities of the brightest galaxies, indicating the need for additional physical mechanisms to boost the UV luminosities at the earliest cosmic epochs, such as a ”top-heavy” stellar initial mass function. We fit the COLIBRE UVLFs with Schechter functions and calculate the evolution of the best-fit parameters. We find that the galaxy number density decreases, the characteristic luminosity becomes fainter and the faint-end slope becomes steeper towards higher redshifts. The UV luminosity density decreases by a factor of several hundred from $z = 7$ to $z = 15$.
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All authors Shengdong Lu, Carlos S. Frenk, Cedric G. Lacey, Andrea Gebek, Joop Schaye, Shaun Cole, Sownak Bose, Anna Durrant, Nick Andreadis, Maarten Baes, Alejandro Benítez-Llambay, Evgenii Chaikin, Camila Correa, Robert A. Crain, Filip Huško, Robert J. McGibbon, Sylvia Ploeckinger, Alexander J. Richings, Matthieu Schaller, James W. Trayford

Astrophysics of Galaxies

Radial redistribution of stellar orbits in FIRE simulations of Milky-Way-mass galaxies

Matthew A. Bellardini, Fiona McCluskey, Andrew Wetzel et al. (+3 more)

A central question in galactic dynamics and galactic archeology is: how much do the orbits of stars redistribute (migrate) after birth? We use the FIRE-2 cosmological zoom-in simulations of 11 Milky Way-mass galaxies to quantify the change in the orbital specific angular momentum, j_phi, orbital radius, R_orbit, and azimuthal velocity, v_phi, of stars from birth to today. We examine the dependences on stellar age, present-day R_orbit, and birth R_orbit, characterizing both the median (net) change, Delta R_orbit, and its scatter, sigma(Delta R_orbit). We comprehensively compare five ways of measuring orbital radius; we find generally consistent trends, but only when measuring radius today and radial redistribution self-consistently. Stars selected by their birth R_orbit typically decreased in R_orbit, j_phi, and v_phi since birth. The trend for stars at a given R_orbit today depends on age: those younger than ~5 Gyr generally decreased in R_orbit, j_phi, and v_phi since birth, while those older generally increased in R_orbit, j_phi, and v_phi since birth. sigma(Delta R_orbit), a standard metric of radial redistribution, increases with stellar age only up to ~ 3 Gyr; it saturates at sigma(Delta R_orbit) ~2 kpc for older stars. This saturation contradicts a common expectation of a monotonic increase with age. Our results broadly agree with recent observational inferences of Delta R_orbit and sigma(Delta R_orbit) in the Milky Way. Across our FIRE-2 sample, the timing of disk formation does not correlate with sigma(Delta R_orbit), but it correlates with (net) Delta R_orbit.
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All authors Matthew A. Bellardini, Fiona McCluskey, Andrew Wetzel, Cecilia Steel, Sarah R. Loebman, Jorge Moreno

Astrophysics of Galaxies

An HST Wide Field Survey of the Galactic Bulge: Overview, Strategy, and First Results

Sean K. Terry, Jay Anderson, Charles A. Beichman et al. (+13 more)

We present an HST imaging survey of a 1.1 sq. degree sky area toward the Milky Way Galactic Bulge. This field significantly overlaps with the upcoming Nancy Grace Roman Galactic Bulge Time Domain Survey (GBTDS). High angular resolution imaging of this area with HST before the start of the Roman Galactic Exoplanet Survey (RGES) will greatly strengthen Roman's ability to characterize detected exoplanet systems, as well as provide a rich and wide-field archive for use as a legacy dataset toward the Galactic Bulge for the broader community. We conduct coordinated-parallel imaging with both wide-field cameras on HST, Wide-field Camera 3 (WFC3) and Advanced Camera for Surveys (ACS), utilizing the F606W and F814W passbands. Approximately 70% of the survey was conducted during HST Cycle 32, with the remaining 30% conducted during Cycle 33. In this paper, the first in a series, we give a general overview of the program and the observing strategy, and present early results. This campaign secures HST's lasting impact on the high-precision study of stellar populations, dynamics, exoplanet systems, interstellar extinction, metallicities, cluster associations, and more toward the center of our Galaxy.
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All authors Sean K. Terry, Jay Anderson, Charles A. Beichman, David P. Bennett, Aparna Bhattacharya, Jean-Philippe Beaulieu, B. Scott Gaudi, Joel Green, Macy J. Huston, Jessica R. Lu, Ray A. Lucas, David M. Nataf, Matthew T. Penny, Natalia E. Rektsini, Carolina Rodriguez Sanchez-Vahamonde, Aikaterini Vandorou

High Energy Astrophysical Phenomena · Cross-listed from hep-ph

Neutrino-Antineutrino Conversion from Ultralight Vector Dark Matter

Asher Berlin, Rodolfo Capdevilla, Ting Cheng et al. (+2 more)

We show that Majorana neutrinos convert into antineutrinos in a background of ultralight vector dark matter coupled to lepton number, such as the gauge boson of $\text{U}(1)_{B-L}$ or $\text{U}(1)_{L_i - L_j}$ with $i, j = e , \mu, \tau$. This effect is suppressed by the small neutrino mass, but the enhancement by long astrophysical baselines can enable future searches for solar and supernova neutrinos to explore uncharted parameter space. For instance, for $\text{U}(1)_{B-L}$ dark matter, the observation of a supernova neutrino burst at DUNE, Hyper-Kamiokande, and JUNO could probe gauge couplings as small as $e^\prime \sim 10^{-32} - 10^{-25}$ for dark matter masses of $m_{A^\prime} \sim 10^{-22} \ \text{eV} - 10^{-14} \ \text{eV}$, beyond the capability of other future probes.
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All authors Asher Berlin, Rodolfo Capdevilla, Ting Cheng, Matheus Hostert, Pedro A. N. Machado

Astrophysics of Galaxies

A Glimpse of the Low-Mass End of the Direct Mass-Metallicity Relation at $z\sim6-8$

Tiger Yu-Yang Hsiao, John Chisholm, Danielle A. Berg et al. (+22 more)

The competition between metal synthesis and feedback from massive stars establishes the mass-metallicity relation (MZR) at low-redshifts. Examining this relation at higher redshifts, particularly at the low-mass end $\lesssim10^{8}\,{\rm M_\odot}$, is essential for understanding chemical enrichment and stellar feedback. In this study, we utilize the deep ($\sim30\,$hrs) JWST/NIRSpec G395M GLIMPSE-D survey of the lensed field Abell S1063, to explore the low-mass end of the MZR at high redshift ($z\sim6-8$). We identify eight [OIII]$\lambda$4364 emitters, enabling the most reliable "direct" metallicity measurements in galaxies down to stellar masses of $\sim10^{6-8}\,{\rm M_\odot}$. By combining our sample and galaxies with [OIII]$\lambda$4364 detections from the literature, we calculate direct metallicities for 21 galaxies. We compare our direct metallicities to those derived from strong-line diagnostics, and find them to be consistent with previous calibrations. We fit the MZR at $10^{6.7-9}\,M_{\odot}$ with $\sim0.3-0.5$ dex lower metallicity than local galaxies at similar stellar mass. We find the slope to be $0.25\pm0.10$, comparable to the local MZR; and the MZR exhibits a scatter of $\sim0.2\,$dex, which is larger than the local MZR, The lower metallicities may reflect denser, more gas-rich early environments, with continuous inflow of metal-poor gas diluting the ISM metallicity. In addition, we show that in extremely high electron densities ($n_e \gtrsim 10^5\,{\rm cm^{-3}}$), metallicities can be significantly underestimated ($\sim0.5$ dex), if lower $n_e$ are assumed for galaxies with high $n_e$. In a nutshell, these observations provide the first glimpse of the low-mass MZR at $z\sim6-8$ using direct metallicity measurements. More deep spectroscopic observations in lensed fields will be critical to robustly characterize the MZR and chemical evolution in the early universe.
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All authors Tiger Yu-Yang Hsiao, John Chisholm, Danielle A. Berg, Steven L. Finkelstein, Vasily Kokorev, Hakim Atek, Rohan P. Naidu, Seiji Fujimoto, Lukas J. Furtak, Angela Adamo, Archana Aravindan, Yoshihisa Asada, Arghyadeep Basu, Jeremy Blaizot, Nicholas Choustikov, Miroslava Dessauges-Zavadsky, Qinyue Fei, Harley Katz, Damien Korber, Kristen. B. W. McQuinn, Marcie Mun, Julian B. Munoz, Priyamvada Natarajan, Mabel G. Stephenson, Daniel Schaerer

Astrophysics of Galaxies

Origins of Extreme Emission-Line Ratios in z > 3 Galaxies: Insights from the Lumen Model

Lucie Scharré, Michaela Hirschmann, Adèle Plat et al. (+10 more)

Optical emission-line ratios in star-forming galaxies at $z \sim 3$-8, such as [OIII]/H$\beta$ and [OIII]/[OII], are strongly offset from those at $z \sim 0$-2, pointing to more extreme ionization and ISM conditions in the early Universe. To constrain the physical origin of these offsets, we developed Lumen, a framework for modelling nebular emission from spatially distributed HII regions in cosmological simulations. We apply Lumen to IllustrisTNG50, validate its predictions at low redshift, and test a suite of proposed mechanisms for producing extreme line ratios at $z = 3$-8. We focus on the [NII]/H$\alpha$ versus [OIII]/H$\beta$ (N2-BPT) diagram, the [SII]/H$\alpha$ versus [OIII]/H$\beta$ (S2-VO87) diagram, and the [OIII]/[OII] versus ([OII]+[OIII])/H$\beta$ (O32-R23) diagram. We find that $\alpha$-enhancement alone cannot explain the bulk of observations. Moderate offsets emerge from the combined effects of $\alpha$-enhancement, a higher IMF upper-mass cutoff, and AGN contributions. The most extreme [OIII]/H$\beta$ and [OIII]/[OII] values require high ionization parameters powered by massive star clusters of $\gtrsim 10^5$-$10^6\,\mathrm{M}_\odot$, consistent with recent JWST observations. Reproducing the highest [NII]/H$\alpha$ ratios additionally requires enhanced nitrogen abundances. Although gas densities of $n \sim 10^4\,\mathrm{cm}^{-3}$ can boost several diagnostic ratios, they suppress [SII]/H$\alpha$ and are therefore in tension with current observations. Overall, models combining harder ionizing spectra, elevated ionization parameters from massive star clusters, and enhanced nitrogen abundances reproduce the observed high-$z$ galaxy population across the N2-BPT, S2-VO87, and O32-R23 diagrams. This successful model also motivates new demarcation lines for star-forming galaxies in the N2-BPT and S2-VO87 diagrams.
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All authors Lucie Scharré, Michaela Hirschmann, Adèle Plat, Stephane Charlot, Rachel S. Somerville, Emma Curtis-Lake, Gabriella De Lucia, Miroslava Dessauges-Zavadsky, Anna Feltre, Marion Farcy, Natalia Lahén, Aswin P. Vijayan, Stephen M. Wilkins

Astrophysics of Galaxies

Complex organic molecules and cosmic ray ionisation rate towards the massive protostar Cepheus A HW2

Emma W. Nielsen, Anna Punanova, Eva Wirström et al. (+5 more)

Cosmic rays (CRs) are important drivers for molecular chemistry in star-forming regions, and laboratory experiments have shown that CRs can stimulate the release of complex organic molecules (COMs) such as methanol. Observationally, this has primarily been tested in cold, low-mass cores, so studying how CRs affect COM formation in a high-mass star-forming environment is of great interest. We performed a high-sensitivity wide-band spectral line survey with the Onsala 20 m telescope towards the high-mass protostar Cepheus A HW2, which is known to host an ionised jet. Consistent with previous studies, two primary velocity components ($-11$ km s$^{-1}$ and $-5$ km s$^{-1}$) were identified. Column densities and relative abundances of the detected ions and COMs were estimated from rotational diagrams, single transitions and RADEX grid searches (CH$_3$OH: $1.6\times10^{-9}$, CH$_3$CN: $5.9\times10^{-11}$, t-HCOOH: $7.9\times10^{-11}$, H$_2$CCO: $1.7\times10^{-11}$, CH$_3$CHO: $1.9\times10^{-11}$, CH$_3$OCHO: $7.6\times10^{-10}$ at $-11$ km s$^{-1}$). Deuterium fractions were also estimated (in range $0.002-0.3$ at $-11$ km s$^{-1}$), and the volume density of molecular hydrogen ($2.6\times10^5$ cm$^{-3}$ at $-11$ km s$^{-1}$) was constrained from the RADEX grid searches. Electron fractions and CR ionisation rates (CRIR, $6.8\times10^{-17}$ s$^{-1}$ at $-11$ km s$^{-1}$, $\leq9.2\times10^{-19}$ s$^{-1}$ at $-5$ km s$^{-1}$) were estimated through analytic chemistry using different ions as probes. The gas-grain chemical code Nautilus reproduced the observed abundances of CH$_3$OH, CH$_3$CN, HCO$^+$, N$_2$H$^+$ at the observed density, temperature and CRIR within the uncertainty of the model. The results indicate that the CR ionisation rate of the kinematic component associated with most of the COMs' emission in the region is locally enhanced.
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All authors Emma W. Nielsen, Anna Punanova, Eva Wirström, Brandt Gaches, A. O. Henrik Olofsson, Paola Caselli, Prasanta Gorai, Jonathan C. Tan

Instrumentation and Methods for Astrophysics

A PINK update: Improvements to the CELEBI fast radio burst data reduction and analysis pipeline

M. Glowacki, T. Dial, A. Bera et al. (+9 more)

Fast radio bursts (FRBs) which are well localised ($<$1") to their host galaxy are tools for studying cosmology and the intergalactic medium. Furthermore, high-time resolution datasets of their polarisation properties can enable testing of the numerous models on their potential progenitors. To that end, the CELEBI (CRAFT Effortless Localisation and Enhanced Burst Inspection) pipeline was conceived to enable data reduction from raw antenna voltages to detect fast radio transient events, localise them to sub-arcsecond precision, and produce polarimetric data at time resolutions as fine as 3 ns. Here we present a slew of updates to the CELEBI pipeline. Improvements to the astrometry correction for FRB localisations have aided our ability to determine what part of a galaxy more nearby FRBs have occurred in, which can have its own implication on the progenitor. We also have implemented time and frequency gating on detected fast transients to enable a boost to signal-to-noise, particularly useful for high dispersion measure or faint fast radio transients. We give examples of our improvements to the localisation, including for the currently 'hostless' FRB 20251019A. The polarisation calibration process has been overhauled, resulting in much more accurate measurements of derived polarisation fraction and rotation measures. Furthermore, we now have incorporated tools for structure-maximisation of the dispersion measure of fast radio transients, a software container which enables the installation of CELEBI on other machines, and improved the pipeline efficiency. Together these updates (named 'Polarisation and astrometry Improvements for New Knowledge', or PINK) greatly improve our ability to keep up with the expected detection rate from the CRAFT COherent (CRACO) upgrade to the real-time fast transient detection system of the Australian SKA Pathfinder.
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All authors M. Glowacki, T. Dial, A. Bera, A. T. Deller, K. Gourdji, A. Jaini, D. Scott, Y. Wang, K. Desnos, A. C. Gordon, R. L. Davies, R. M. Shannon

Astrophysics of Galaxies

The Pulsar Radial Acceleration Relation

Tariq Yasin and Harry Desmond

The radial acceleration relation (RAR) links observed and baryonic accelerations, and is best established in rotation curves of late-type galaxies. Pulsar timing, which measures line-of-sight (LOS) differential accelerations between the Sun and pulsars, provides a novel probe of this relation, including along directions outside the Galactic disc. By combining these pulsar differential accelerations with the acceleration at the Sun, we test whether current pulsar timing data carry information on a vector generalisation of the RAR, ${g}_{\rm obs}=\nu(|{g}_{\rm bar}|){g}_{\rm bar}$. Comparing the measured SPARC RAR (generalised to 3D) to 26 binary-system pulsars with literature accelerations, we find a reduced $\chi^2$ of 3.58, compared with 10.86 for Newtonian baryonic gravity alone. However, setting all accelerations to that of the Sun gives a reduced $\chi^2$ of 3.75, showing that this vector RAR test is dominated by the Solar acceleration with current data.
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Instrumentation and Methods for Astrophysics

A preliminary exploration of the effects of baseline length for the LIFE space mission

Jonah T. Hansen, Thomas Birbacher, Felix A. Dannert et al. (+7 more)

By aiming to find and characterise dozens of habitable exoplanets through the technique of nulling interferometry, the LIFE space mission will produce transformational science. One of the key parameters for such an interferometric mission is the nulling baseline length - the distance between nulled apertures, which past studies have assumed to be 10-100m. Advances in planet occurrence statistics and simulation tools allow us now to revisit this key assumption with significantly more detail, particularly with the intention to reduce the range of baselines considered due to mission implementation concerns. We utilise the LIFEsim mission simulator along with revised mathematical tools to identify whether the range of baselines could be reduced without significantly affecting planet yield and fringe tracking performance. Along the way, we also determine a new astrophysically motivated technique for choosing which baselines are optimal for a given science target. We find that indeed, LIFE could utilise a considerably shorter range of baselines, such as 25-80m, or even discrete baselines without much (<10%) loss of performance. Nevertheless, careful trade-offs between performance and implementation simplification must be made, especially considering any spectral weighting that may be required by the scientific goals, and the potential loss of target-specific baseline optimisation.
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All authors Jonah T. Hansen, Thomas Birbacher, Felix A. Dannert, Philipp Huber, Andrea Fortier, Adrian M. Glauser, Jens Kammerer, Romain Laugier, Lia Sartori, Sascha P. Quanz

Instrumentation and Methods for Astrophysics

What You Don't Know Won't Hurt You: Self-Consistent Hierarchical Inference with Unknown Follow-up Selection Strategies

Reed Essick and Amanda M. Farah

Many astronomical surveys prompt follow-up observations, but the decision process through which candidates are selected for follow-up can be difficult to model. This poses a challenge when inferring properties of the intrinsic population of astrophysical sources, rather than those of the set of objects detected by the survey and often-incomplete follow-up observations. We alleviate this problem by demonstrating that explicitly modeling of the follow-up selection process is not required for self-consistent inference of the intrinsic population. Using the framework of hierarchical Bayesian inference, we show that the intrinsic population can be accurately inferred even when the decision to follow up candidates strongly correlates with latent parameters of interest. We provide several worked examples, showing that the precision of posterior constraints can depend on the follow-up process and that one may have to model a population of contaminants if the initial selection is imperfect. Our result could dramatically simplify population inference that incorporates uncoordinated follow-up from multiple observers triggered by the deluge of candidates from surveys like LSST, Gaia, and next-generation gravitational-wave interferometers.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ex

Sensitivity Projections for Low-Mass Dark Matter Annihilation with the IceCube Upgrade

R. Abbasi, M. Ackermann, J. Adams et al. (+412 more)

The IceCube Upgrade, an extension designed to enhance the IceCube Neutrino Observatory's detection of neutrinos with energies between 1 GeV and 500 GeV, will markedly improve IceCube's sensitivity to low-mass dark matter scenarios. In this study, we present sensitivity projections for the IceCube Upgrade to neutrino fluxes arising from dark matter annihilation. In particular, we consider dark matter with masses between 3 GeV to 500 GeV from both the core of the Sun and the Galactic Center. These projections indicate that the IceCube Upgrade will enable stringent limits on dark matter in this parameter space, achieving leading sensitivities to some dark matter models with only three years of data taking.
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All authors R. Abbasi, M. Ackermann, J. Adams, J. A. Aguilar, M. Ahlers, J.M. Alameddine, S. Ali, N. M. Amin, K. Andeen, C. Argüelles, Y. Ashida, S. Athanasiadou, S. N. Axani, R. Babu, X. Bai, A. Balagopal V., S. W. Barwick, V. Basu, R. Bay, J. J. Beatty, J. Becker Tjus, P. Behrens, J. Beise, C. Bellenghi, S. Benkel, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, E. Blaufuss, L. Bloom, S. Blot, F. Bontempo, J. Y. Book Motzkin, C. Boscolo Meneguolo, S. Böser, O. Botner, J. Böttcher, J. Braun, B. Brinson, Z. Brisson-Tsavoussis, R. T. Burley, D. Butterfield, K. Carloni, J. Carpio, N. Chau, Y. C. Chen, Z. Chen, D. Chirkin, S. Choi, A. Chubarov, B. A. Clark, G. H. Collin, D. A. Coloma Borja, A. Connolly, J. M. Conrad, D. F. Cowen, C. De Clercq, J. J. DeLaunay, D. Delgado, T. Delmeulle, S. Deng, P. Desiati, K. D. de Vries, G. de Wasseige, T. DeYoung, J. C. Díaz-Vélez, S. DiKerby, T. Ding, M. Dittmer, A. Domi, L. Draper, L. Dueser, D. Durnford, K. Dutta, M. A. DuVernois, T. Ehrhardt, L. Eidenschink, A. Eimer, C. Eldridge, P. Eller, E. Ellinger, D. Elsässer, R. Engel, H. Erpenbeck, W. Esmail, S. Eulig, J. Evans, P. A. Evenson, K. L. Fan, K. Fang, K. Farrag, A. R. Fazely, A. Fedynitch, N. Feigl, C. Finley, D. Fox, A. Franckowiak, S. Fukami, P. Fürst, J. Gallagher, E. Ganster, A. Garcia, M. Garcia, E. Genton, L. Gerhardt, A. Ghadimi, C. Glaser, T. Glüsenkamp, J. G. Gonzalez, S. Goswami, A. Granados, D. Grant, S. J. Gray, S. Griffin, K. M. Groth, D. Guevel, C. Günther, P. Gutjahr, C. Ha, A. Hallgren, L. Halve, F. Halzen, L. Hamacher, M. Handt, K. Hanson, J. Hardin, A. A. Harnisch, P. Hatch, A. Haungs, J. Häußler, K. Helbing, J. Hellrung, B. Henke, L. Hennig, F. Henningsen, L. Heuermann, R. Hewett, N. Heyer, S. Hickford, A. Hidvegi, C. Hill, G. C. Hill, R. Hmaid, K. D. Hoffman, A. Hollnagel, D. Hooper, S. Hori, K. Hoshina, M. Hostert, W. Hou, M. Hrywniak, T. Huber, K. Hultqvist, K. Hymon, A. Ishihara, W. Iwakiri, M. Jacquart, S. Jain, O. Janik, M. Jansson, M. Jin, N. Kamp, D. Kang, W. Kang, A. Kappes, L. Kardum, T. Karg, A. Karle, A. Katil, M. Kauer, J. L. Kelley, M. Khanal, A. Khatee Zathul, A. Kheirandish, T. Kim, H. Kimku, F. Kirchner, J. Kiryluk, C. Klein, S. R. Klein, Y. Kobayashi, S. Koch, A. Kochocki, R. Koirala, H. Kolanoski, T. Kontrimas, L. Köpke, C. Kopper, D. J. Koskinen, P. Koundal, M. Kowalski, T. Kozynets, A. Kravka, N. Krieger, T. Krishnan, K. Kruiswijk, E. Krupczak, A. Kumar, E. Kun, N. Kurahashi, C. Lagunas Gualda, L. Lallement Arnaud, M. J. Larson, F. Lauber, J. P. Lazar, K. Leonard DeHolton, A. Leszczyńska, C. Li, J. Liao, C. Lin, Q. R. Liu, Y. T. Liu, M. Liubarska, C. Love, L. Lu, F. Lucarelli, W. Luszczak, Y. Lyu, M. Macdonald, E. Magnus, Y. Makino, E. Manao, S. Mancina, A. Mand, I. C. Mariş, S. Marka, Z. Marka, L. Marten, I. Martinez-Soler, R. Maruyama, J. Mauro, F. Mayhew, F. McNally, K. Meagher, A. Medina, M. Meier, Y. Merckx, L. Merten, J. Mitchell, L. Molchany, S. Mondal, T. Montaruli, R. W. Moore, Y. Morii, A. Mosbrugger, D. Mousadi, E. Moyaux, T. Mukherjee, M. Nakos, U. Naumann, L. Neste, M. Neumann, H. Niederhausen, M. U. Nisa, K. Noda, A. Noell, A. Novikov, A. Obertacke, V. O'Dell, A. Olivas, R. Orsoe, J. Osborn, E. O'Sullivan, B. Owens, V. Palusova, H. Pandya, A. Parenti, N. Park, V. Parrish, E. N. Paudel, L. Paul, C. Pérez de los Heros, T. Pernice, T. C. Petersen, J. Peterson, S. Pick, M. Plum, A. Pontén, V. Poojyam, B. Pries, R. Procter-Murphy, G. T. Przybylski, L. Pyras, C. Raab, J. Rack-Helleis, N. Rad, M. Ravn, K. Rawlins, Z. Rechav, A. Rehman, I. Reistroffer, E. Resconi, C. D. Rho, W. Rhode, L. Ricca, B. Riedel, A. Rifaie, E. J. Roberts, S. Rodan, M. Rongen, A. Rosted, C. Rott, T. Ruhe, L. Ruohan, D. Ryckbosch, J. Saffer, D. Salazar-Gallegos, P. Sampathkumar, A. Sandrock, G. Sanger-Johnson, M. Santander, S. Sarkar, M. Scarnera, M. Schaufel, H. Schieler, S. Schindler, L. Schlickmann, B. Schlüter, F. Schlüter, N. Schmeisser, T. Schmidt, A. Scholz, F. G. Schröder, S. Schwirn, S. Sclafani, D. Seckel, L. Seen, M. Seikh, S. Seunarine, P. A. Sevle Myhr, R. Shah, S. Shah, S. Shefali, N. Shimizu, B. Skrzypek, R. Snihur, J. Soedingrekso, D. Soldin, P. Soldin, G. Sommani, D. Song, C. Spannfellner, G. M. Spiczak, C. Spiering, J. Stachurska, M. Stamatikos, T. Stanev, T. Stezelberger, T. Stürwald, T. Stuttard, G. W. Sullivan, I. Taboada, S. Ter-Antonyan, A. Terliuk, A. Thakuri, M. Thiesmeyer, W. G. Thompson, J. Thwaites, S. Tilav, K. Tollefson, J. A. Torres, S. Toscano, D. Tosi, K. Upshaw, A. Vaidyanathan, N. Valtonen-Mattila, J. Valverde, J. Vandenbroucke, T. Van Eeden, N. van Eijndhoven, L. Van Rootselaar, J. van Santen, J. Vara, F. Varsi, M. Venugopal, M. Vereecken, S. Vergara Carrasco, S. Verpoest, D. Veske, A. Vijai, J. Villarreal, C. Walck, A. Wang, E. H. S. Warrick, C. Weaver, P. Weigel, A. Weindl, J. Weldert, A. Y. Wen, C. Wendt, J. Werthebach, M. Weyrauch, N. Whitehorn, C. H. Wiebusch, D. R. Williams, L. Witthaus, G. Wrede, X. W. Xu, J. P. Yanez, Y. Yao, E. Yildizci, S. Yoshida, R. Young, F. Yu, S. Yu, T. Yuan, S. Yun-Cárcamo, A. Zander Jurowitzki, A. Zegarelli, S. Zhang, Z. Zhang, P. Zhelnin, P. Zilberman, C. Zilleruelo Cañas

Cosmology and Nongalactic Astrophysics

Constraining Galaxy Cluster Triaxiality via Weak Lensing — I. Preparation for the Rubin Data Beyond Leading Order

Shenming Fu, Radhakrishnan Srinivasan, Tae-hyeon Shin et al. (+13 more)

The 3D mass distributions of galaxy clusters are generally triaxial, a geometry that is difficult to constrain from projected observations. In this work, we measure the projected halo shapes of clusters from weak lensing signatures using the Cluster Lensing Mass Modeling software, a tool developed by the Dark Energy Science Collaboration to analyze data from NSF-DOE Rubin Observatory's Legacy Survey of Space and Time (LSST). We measure ensemble halo ellipticity on the plane of the sky via axis-aligned stacking and multipole expansion of weak lensing signatures. We study a precursor dataset — the redMaPPer cluster catalog, the metacalibration shape catalog, and the Directional Neighborhood Fitting photometric redshift catalog from the Dark Energy Survey Year 3 public data release. We select clusters that have a high centering probability (>90%) of the identified central galaxy, and use the satellite galaxy distribution to determine the major-axis orientation for stacking. We extend the analysis to the second order of ellipticity in monopole and quadrupole measurements. The projected ellipticity of the cluster sample is found to be $0.307^{+0.013}_{-0.014}$ (axis ratio $0.530^{+0.016}_{-0.015}$) with extra percent-level systematics introduced mainly by miscentering. The projected cluster ellipticity shows no statistically significant dependence on redshift or richness (mass proxy). We further verify the accuracy of the cluster shape measurement using mock catalogs. This analysis is applicable to datasets from wide-area cosmic surveys such as LSST, Euclid, and the Roman Space Telescope, where larger sample sizes will lead to tighter constraints on cluster shapes.
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All authors Shenming Fu, Radhakrishnan Srinivasan, Tae-hyeon Shin, Rance Solomon, Deric Jones, Camille Avestruz, Yuanyuan Zhang, Michel Aguena, Céline Combet, Anthony Englert, Benjamin Levine, Alex I. Malz, Constantin Payerne, Marina Ricci, Anja von der Linden, the LSST Dark Energy Science Collaboration

Astrophysics of Galaxies

The 2MIG isolated AGNs. 3. Optical–IR variability and dust reverberation in the NLSy1 galaxies Mrk~42 and Mrk~493

I.O. Izviekova, I.B. Vavilova, O.V. Kompaniiets et al. (+2 more)

This work presents the first dedicated optical–mid-infrared time-domain variability and dust-reverberation analysis of the isolated NLSy1 galaxies Mrk 42 and Mrk 493. We combine ZTF optical light curves, WISE mid-infrared monitoring, archival Swift and SDSS data, and high-cadence IAC80 optical observations. Using colour–magnitude relations, flux–flux analysis, and interpolated cross-correlation functions, we trace variable optical continuum and delayed dust response. Both galaxies show positive optical–MIR lags consistent with dust reverberation. For Mrk 493, we measure an observed-frame g–W1 lag of $\tau_{\rm obs}=79.4\pm2.2$ d, corresponding to $R_{\rm dust}(W1)\simeq0.0648$ pc. For Mrk 42, the corresponding lag is $\tau_{\rm obs}=39.1\pm2.6$ d, giving $R_{\rm dust}(W1)\simeq0.0320$ pc. These lags provide optical–MIR dust-reverberation radii and BLR–dust scale comparisons for both objects; the resulting $R_{\rm dust}/R_{\rm BLR}$ ratios are $\simeq6.8$ for Mrk 493 and $\sim6$–7 for Mrk 42. For Mrk 42, we derive the first host-subtracted AGN continuum luminosity at 5100 Å\ from SDSS spectral decomposition, giving a self-consistent BLR–dust comparison on an AGN-only luminosity basis. Both galaxies have similar radial hierarchies but different colour behaviour: Mrk 493 shows significant optical and MIR bluer-when-brighter trends, whereas Mrk 42 shows strong optical but weak MIR colour variability. We also identify and analyse a major optical flare in Mrk 42 with four internal maxima spaced by 45–47 d. We interpret this signal as quasi-periodic substructure within a broader accretion-driven flare, rather than as a strictly coherent periodic process. These results indicate that, even in dynamically isolated environments, the variability of low-mass, high-accretion-rate AGNs is governed mainly by the intrinsic state of the accretion flow and its coupling to circumnuclear dust.
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All authors I.O. Izviekova, I.B. Vavilova, O.V. Kompaniiets, O. Zamora, R. Clavero

High Energy Astrophysical Phenomena

Fifteen new millisecond pulsars in 47 Tucanae

W. Chen, D. Risbud, P. C. C. Freire et al. (+16 more)

47 Tucanae is one of the largest, brightest, and closest globular clusters to Earth. It hosts an exotic stellar population with stellar dynamics that indicate a complex evolution history. The cluster contains a large number of X-ray binaries and millisecond pulsars. However, given its large distance relative to the known pulsar population, previous surveys have found only the very brightest sources. Therefore, surveys with increased sensitivity should find many additional pulsars. Increasing the number of pulsars is crucial to investigate the dynamics of this globular cluster and could also lead to the discovery of unusual types of system. With a significantly increased sensitivity compared to earlier telescopes, MeerKAT is the natural choice to perform new surveys. We carried out two campaigns with different observational cadences to account for the high scintillation along the line of sight to this cluster. Here we report the discovery of fifteen new pulsars in 47 Tucanae with MeerKAT. These discoveries bring the total number of known pulsars in this globular cluster to 42, and the MeerKAT discoveries in this cluster to 17. We discuss some of their characteristics, which include preliminary localisations and estimates of orbits for most systems. Highlights include the discovery of 47 Tuc af, a 'black widow' pulsar with a short orbital period that was identified optically in 2002 as a candidate binary pulsar, and 47 Tuc ai, an eccentric binary pulsar with a massive companion, a unique system in 47 Tuc to date. Apart from the new systems, we also re-detect and localise 47 Tuc P and V, two elusive, seldom-detected systems that had no precise localisation from a phase-connected timing solution. The localisation of 47 Tuc V places it in a position consistent with a continuum source detected earlier in MeerKAT imaging data.
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All authors W. Chen, D. Risbud, P. C. C. Freire, A. Ridolfi, E. Barr, M. Kramer, B. Stappers, F. Camilo, F. Abbate, A. Possenti, Y. P. Men, P. V. Padmanabh, S. M. Ransom, L. Vleeschower, V. Venkatraman Krishnan, D. J. Champion, Rene Breton, V. Balakrishnan, S. Buchner

Instrumentation and Methods for Astrophysics

Atmospheric turbulence profiling with the Multistar Turbulence Monitor

Weisen Huang, Bin Ma, Tengfei Song et al. (+5 more)

Accurate characterization of atmospheric optical turbulence is essential for evaluating astronomical sites and optimizing adaptive optics systems. The Multistar Turbulence Monitor (MTM) infers the vertical distribution of the refractive-index structure constant Cn2(z) from differential image motion measured between multiple stellar pairs in short-exposure frames. We present a comprehensive investigation of the MTM method, combining theoretical analysis, instrument-performance assessment, numerical simulations, and on-sky observations obtained at the Daocheng Astronomical Site. Simulations based on a standard HV turbulence model demonstrate that the inversion pipeline robustly recovers both the integrated seeing and the vertical turbulence profile under realistic centroiding noise and varying pixel scales. The Markov Chain Monte Carlo (MCMC) inversion achieves stable results with thirteen discrete height nodes and provides reliable uncertainties. Three nights of MTM measurements at the Daocheng Astronomical Site show that MTM-derived seeing closely tracks simultaneous Differential Image Motion Monitor (DIMM) results, accurately reproducing both short-term fluctuations and nightly averages. These results confirm that MTM provides a simple, portable, and versatile solution for atmospheric turbulence profiling and routine seeing monitoring.
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All authors Weisen Huang, Bin Ma, Tengfei Song, Paul Hickson, Zhaohui Shang, Xuefei Zhang, Mingyu Zhao, Qing Zhou

Instrumentation and Methods for Astrophysics

Muon Track Reconstruction Procedures at the Baikal-GVD Neutrino Telescope

Grigory Safronov

The Baikal-GVD neutrino telescope is the largest neutrino detector of its kind in the Northern Hemisphere. Muons produced in neutrino interaction in the vicinity of the detector leave track-like response in the detector allowing to reconstruct the neutrino arrival direction with the precision up to 0.2 degree. The Baikal-GVD collaboration has developed a variety of methods for the track-like event analysis. Methods for track-like event direction and energy reconstruction and neutrino cadidate event selection are discussed in this report. Preliminary results of application of analysis pipeline to the data-taking seasons from 2019 to 2021 are shown.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Nonradial oscillations of realistic anisotropic neutron stars: Axial modes

Jose F. Rodriguez-Ruiz, L. M. Becerra and F. D. Lora-Clavijo

Non-radial oscillation modes of neutron stars serve as diagnostics of their internal composition and relativistic structure. In this work, we investigate the perturbations of static and spherically symmetric neutron stars characterized by an anisotropic pressure. Given the background symmetry, perturbations decouple into polar and axial modes. To date, axial modes have remained less explored, primarily because matter and metric perturbations decouple in the isotropic limit. In this work, we provide a consistent treatment of axial modes and demonstrate that pressure anisotropy induces a direct coupling between matter and metric perturbations. We employ parameterized anisotropy models that ensure consistency with the treatment of matter perturbations. We numerically integrate the linearized Einstein field equations for the axial modes, employing a diverse set of realistic equations of state. Our results indicate that as the stellar mass grows, the frequency of the base $w$-mode generally decreases, while its damping time increases. Softer equation of states typically yield slightly higher oscillation frequencies. Furthermore, larger anisotropy (i. e., when the tangential pressure exceeds the radial pressure) allows for more massive equilibrium configurations, which correspondingly leads to lower oscillation frequencies and prolonged damping times. Finally, we demonstrate that the frequency and damping time, both scaled by the stellar mass, exhibit a nearly universal quadratic dependence on the stellar compactness, remaining largely insensitive to the underlying equation of state, but slightly dependent to the specific anisotropy model.
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