arXiv subjects

Charlotte Wood

Publications and source records attributed to Charlotte Wood.

3 recordsLinked to original sources

arXiv2026

The Highly Variable Wind from WD J005311, the Stellar Remnant of the Peculiar Galactic Supernova of 1181

WD J005311 is the peculiar stellar remnant of the Galactic supernova from 1181, and appears to have been the merger of two white dwarfs. We present time-resolved spectroscopy of WD J005311 showing emission line variability on a wide range of time-scales. The strong O VI emission feature displays line profile variations (LPVs) on two distinct velocity scales. Broad variations with amplitudes of $\pm$10% of the line flux are seen over the entire O VI line. These broad LPVs likely arise from instabilities in the line-driven wind produced in many Wolf-Rayet stars. There is a hint of coherent structure in the broad LPVs that is consistent with rotation over roughly two hours, although the features survive for less than a full cycle. Low-amplitude, narrow LPVs are also detected within the central $\pm$5000 km/s of the O VI line. We associate these features with an unstable disk formed from the rigidly rotating magnetosphere (RRM) of the remnant white dwarf. We also analyze archival near-ultraviolet photometry of WD J005311 and find a pseudo-periodic oscillation with an hour-long time-scale that maybe associated with the breakout instability of the RRM disk.

astro-ph.SR↗

arXiv2022

The Pantheon+ Analysis: The Full Dataset and Light-Curve Release

Here we present 1701 light curves of 1550 spectroscopically confirmed Type Ia supernovae (SNe Ia) that will be used to infer cosmological parameters as part of the Pantheon+ SN analysis and the SH0ES (Supernovae and H0 for the Equation of State of dark energy) distance-ladder analysis. This effort is one part of a series of works that perform an extensive review of redshifts, peculiar velocities, photometric calibration, and intrinsic-scatter models of SNe Ia. The total number of light curves, which are compiled across 18 different surveys, is a significant increase from the first Pantheon analysis (1048 SNe), particularly at low redshift ($z$). Furthermore, unlike in the Pantheon analysis, we include light curves for SNe with $z<0.01$ such that SN systematic covariance can be included in a joint measurement of the Hubble constant (H$_0$) and the dark energy equation-of-state parameter ($w$). We use the large sample to compare properties of 151 SNe Ia observed by multiple surveys and 12 pairs/triplets of "SN siblings" - SNe found in the same host galaxy. Distance measurements, application of bias corrections, and inference of cosmological parameters are discussed in the companion paper by Brout et al. (2022b), and the determination of H$_0$ is discussed by Riess et al. (2022). These analyses will measure w with $\sim3\%$ precision and H$_0$ with 1 km/s/Mpc precision.

astro-ph.CO↗

arXiv2018

High-Time-Resolution Photometry of AR Scorpii: Confirmation of the White Dwarf's Spin-Down

The unique binary AR Scorpii consists of an asynchronously rotating, magnetized white dwarf (WD) that interacts with its red-dwarf companion to produce a large-amplitude, highly coherent pulsation every 1.97 minutes. Over the course of two years, we obtained thirty-nine hours of time-resolved, optical photometry of AR Sco at a typical cadence of 5 seconds to study this pulsation. We find that it undergoes significant changes across the binary orbital period and that its amplitude, phase, and waveform all vary as a function of orbital phase. We show that these variations can be explained by constructive and destructive interference between two periodic, double-peaked signals: the spin-orbit beat pulse, and a weaker WD spin pulse. Modelling of the light curve indicates that in the optical, the amplitude of the primary spin pulse is 50% of the primary beat amplitude, while the secondary maxima of the beat and spin pulses have similar amplitudes. Finally, we use our timings of the beat pulses to confirm the presence of the disputed spin-down of the WD. We measure a beat-frequency derivative of -5.14(32) x 10^-17 Hz/s and show that this is attributable to the spin-down of the WD. This value is approximately twice as large as the estimate from Marsh et al. (2016) but is nevertheless consistent with the constraints established in Potter & Buckley (2018). Our precise measurement of the spin-down rate confirms that the decaying rotational energy of the magnetized white dwarf is sufficient to power the excess electromagnetic radiation emitted by the binary.

astro-ph.SR↗