arXiv subjects

Ian Berry

Publications and source records attributed to Ian Berry.

4 recordsLinked to original sources

arXiv2026

The $δ$ Scuti instability strip and period-luminosity relation as seen by TESS and Gaia DR3

We present an asteroseismic survey of 1,526,218 A- and F-type stars in and around the $δ$ Scuti instability strip using TESS 10-minute cadence data, which resolve the full $δ$ Scuti pulsation spectra across nearly the entire sky. We derive homogeneous stellar parameters from Gaia DR3 parallaxes and archival photometry, with temperatures that agree with interferometry to within ~300 K. A Positive--Unlabelled classifier identifies 156,706 $δ$ Scuti pulsators, which on average rotate significantly faster than non-variable A-type stars. Within the instability strip in the $T_{eff}$--$\log L$ plane, the pulsator fraction peaks at 30% over the full sample and rises to 80% in the brightest magnitude bins. Detection sensitivity therefore accounts for much, but not all, of the apparent impurity of the strip. Our period--luminosity relation agrees with previous determinations, and we recast it as a scale-invariant period--density relation that connects directly to the pulsation constant. We find that the secondary ridge in these relations is probably a combination of several overtone modes. The $δ$ Scuti stars closest to the fundamental ridge have systematically lower rotational velocities and occupy a distinct region of the instability strip. Finally, a cross-match with a Gaia catalog of open clusters reveals a correlation between the mean pulsation frequency of $δ$ Scuti stars and cluster age, suggesting a new ensemble asteroseismic age indicator for young stellar populations.

astro-ph.SR↗

arXiv2026

Equivariant generative diffusion learns and generalizes the structural ensemble of amorphous oxides

Amorphous materials are statistical ensembles rather than definitive structures, and conventional density-functional (DFT) and machine-learned-potential simulations sample only a small part of that ensemble. We present an $SE(3)$-equivariant denoising-diffusion model that learns the configurational distribution of amorphous oxides, so the model itself is the structure database. The learning is data efficient. A model trained on $1{,}781$ DFT configurations suffices to reproduce partial radial distribution functions, coordination statistics and bond-angle distributions, and to generate models of over $3\times10^{5}$ atoms at a cost comparable to that of the cheapest classical pair potentials. The trained model can propose amorphous atomic structures for first-principles relaxation to explore the configuration space. For example, it locates an amorphous Zr-Ta-O structure $36$ meV/atom below the previously known minimum. Generation can also extend beyond trained conditions to non-stoichiometric compositions, other mass densities, interfaces, and doping. First-principles verification confirms that generation can be steered to a requested energy, and shows that the denoising training loss does not rank generative quality, because the two measure different things.

cond-mat.mtrl-sci↗

arXiv2026

The $δ$ Scuti pulsator occurrence as a function of age, $T_{\rm eff}$, rotation, and metallicity

Many A- and F- type stars do not display $δ$ Scuti pulsations, despite being located within the instability strip. We use photometry from the TESS Mission to discover and study $δ$ Scuti pulsators in open clusters within 500 pc and with ages between ~20 and 900 Myr, which provide a unique opportunity to study $δ$ Scuti pulsators in coeval populations with uniform chemical composition. We measure pulsator occurrence, which corrects the pulsator fraction for incompleteness, across all clusters. We find that clusters younger than 200 Myr tend to exhibit higher occurrence rates, with an average occurrence of 88$\pm$3\%. The occurrence rates in clusters older than 200 Myr tend to resemble the pulsator fraction of field-star samples, with an average occurrence of 62$\pm$3\%. In addition, we find that pulsators tend to rotate more rapidly in older clusters than their younger counterparts and that hotter pulsators may stop pulsating earlier than their cooler counterparts. These results show that pulsator occurrence decreases with age and that rapid rotation is critical in maintaining $δ$ Scuti pulsations over time.

astro-ph.SR↗

arXiv2025

Discovery of 79 $δ$ Scuti Stars in NGC 3532 Suggests a Decrease of Pulsator Occurrence with Age

Many A-F type stars do not display $δ$ Scuti pulsations, despite being located within the instability strip. Open clusters provide a unique opportunity to study $δ$ Scuti pulsations among coeval populations with uniform chemical composition. Here we use data from the TESS Mission to discover 79 $δ$ Scuti pulsators in the 300 Myr old open cluster NGC 3532, the largest number found within a single open cluster to-date. We report a $50\pm5\%$ pulsator fraction in NGC 3532, considerably lower than in younger stellar populations, such the Pleiades (110 Myr), NGC 2516 (100 Myr), and the Cep-Her Complex ($\leq\,$80 Myr), and similar to the pulsator fraction found among field star samples. We introduce the concept of pulsator occurrence, which corrects for incompleteness, and find it to be $63\pm6\%$. For the stars that do pulsate, we find that the hotter stars occupy a distinct branch in the color-magnitude diagram (CMD) due to faster rotation ($>\,$150 km/s) than their non-pulsating counterparts. These results suggest that pulsator occurrence decreases with age and that rapid rotation is important in maintaining $δ$ Scuti pulsations over time. We also investigate the Period-Luminosity (P-L) relation and the $ν_{\rm max}$--$T_{\rm eff}$ relation of $δ$ Scuti stars in NGC 3532. We find much scatter in the P-L relation of the dominant mode and two distinct branches in the $ν_{\rm max}$--$T_{\rm eff}$ relation, similar to the Cep-Her Complex.

astro-ph.SR↗