arXiv subjects

Mary Ogborn

Publications and source records attributed to Mary Ogborn.

4 recordsLinked to original sources

arXiv2026

Spectroscopic Variability of the Broad H$\beta$ Emission Line in Sloan Digital Sky Survey Quasars

We present a catalog of broad H$\beta$ variability properties for all spectra of quasars with $z<0.8$ and at least two observations included in the Sloan Digital Sky Survey (SDSS) Data Release 16 quasar catalog. For each spectrum, we perform a spectral decomposition to isolate the broad H$\beta$ emission. We measure the luminosity, FWHM, equivalent width, centroid, and Pearson skewness coefficient of broad H$\beta$ and provide derived physical properties such as the single-epoch black hole mass and the bolometric luminosity. For each pair of spectra in the sample, we calculate the change in radial velocity of the centroid of broad H$\beta$ emission ($\Delta v_{rad}$) as well as other derived properties related to broad H$\beta$ shape variability. We use forward-modeling methods to estimate the uncertainty in our measurements and discuss an improved method for estimating the uncertainty in $\Delta v_{rad}$ in the case where a spectral decomposition is used to isolate the broad H$\beta$ emission. We find that $\Delta v_{rad}$ is not normally distributed and that the shape of the distribution depends on the interval between observations. We discuss the effect of the predominance of the Reverberation Mapping subsample in the sample of pairs of spectra in SDSS.

astro-ph.HE↗

arXiv2025

Simulating Disky Broad Line Region Reverberation

Variability studies of the broad emission lines of Active Galactic Nuclei (AGNs) and quasars show stochastic radial velocity variations (i.e., fluctuations in the centroid of the line), 'jitter', on timescales of weeks to months. This jitter may be intrinsic as the broad-line emitting region (BLR) reverberates from the AGN continuum. There are also coordinated variations in the width of the broad emission lines and the luminosity of the central source ('breathing' or 'anti-breathing') which remain unexplained. These can be used as a tool for testing models of the BLR. We have constructed a pipeline to simulate a disk-like BLR geometry that reverberates in response to various chosen continuum light curves and produce synthetic emission line profiles. These profiles can then be characterized by measured shape parameters (centroid velocity shift, velocity dispersion, and Pearson skewness coefficient) and compared to observed time series of those same parameters. We have found that through our pipeline, we can recreate the velocity jitter at similar variations found in observations. The computational tools presented in this paper will also be applicable to case studies of quasars observed under the Sloan Digital Sky Survey V (SDSS-V) Black Hole Mapper reverberation mapping program. This paper is the first in a series of papers -- in this paper, we present the model and pipeline, and in future papers, we will present applications.

astro-ph.GA↗

arXiv2025

Can a time evolving, asymmetric broad line region mimic a massive black hole binary?

Gas within the influence sphere of accreting massive black holes is responsible for the emission of the broad lines observed in optical-UV spectra of unobscured active galactic nuclei. Since the region contributing the most to the broad emission lines (i.e. the broad line region) depends on the active galactic nucleus luminosity, the study of broad line reverberation to a varying continuum can map the morphology and kinematics of gas at sub-pc scales. In this study, we modify a preexisting model for disc-like broad line regions, including non-axisymmetric structures, by adopting an emissivity profile that mimics the observed luminosity-radius relation. This makes our implementation particularly well suited for the analysis of multi-epoch spectroscopic campaigns. After validating the model, we use it to check if strongly non-axisymmetric, single broad line regions could mimic the short time-scale evolution expected from massive black hole binaries. We explore different orientations and anisotropy degrees of the broad line region, as well as different light curve patterns of the continuum to which the broad line region responds. Our analysis confirms that recently proposed algorithms designed to search for massive black hole binaries in large multi-epoch spectroscopic data are not contaminated by false positives ascribed to anisotropic broad line regions around single MBHs.

astro-ph.GA↗

arXiv2025

Million Points of Light (MPoL): a PyTorch library for radio interferometric imaging and inference

Astronomical radio interferometers achieve exquisite angular resolution by cross-correlating signal from a cosmic source simultaneously observed by distant pairs of radio telescopes to produce a Fourier-type measurement called a visibility. Million Points of Light (MPoL) is a Python library supporting feed-forward modeling of interferometric visibility datasets for synthesis imaging and parametric Bayesian inference, built using the autodifferentiable machine learning framework PyTorch. Neural network components provide a rich set of modular and composable building blocks that can be used to express the physical relationships between latent model parameters and observed data following the radio interferometric measurement equation. Industry-grade optimizers make it straightforward to simultaneously solve for the synthesized image and calibration parameters using stochastic gradient descent.

astro-ph.IM↗