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James Dawson

Publications and source records attributed to James Dawson.

4 recordsLinked to original sources

Twin Impact Lunar Telescope network: Lunar Impact Flash observations of the 2025 Geminids

Meteoroid impacts on the Moon, observed from Earth as flashes typically lasting a few tens of milliseconds, have been monitored for three decades for determining meteoroids' size and mass frequency distribution in the cm to dm range. Studies link these observed impact events to fresh craters advancing our understanding of energy partitioning during an impact. Currently we are transitioning to a new era where lunar impact flashes (LIFs) can be used to supplement upcoming lunar seismology to study the internal lunar structure. Here we present results from the first station of a telescope network under development for continuous LIF monitoring. Observations were carried out during the Geminids 2025 campaign, initiated by the LUMIO Science Team in the framework of their public engagement activities. We detected 53 potential impact flashes and confirmed 11 of them through multiframe observations, and independent detections by other observers. We present evidence suggesting that some of the yet unconfirmed events may be real. Our confirmed events range between magnitude +7.5 and +10.4, primarily in the V and R band. We obtained a high rate of observations per hour, highlighting the importance of high ZHR meteoroid streams for observing LIFs. We also discuss the scientific value of potential LIFs that remain unconfirmed in optical data alone. Even without multi station confirmation, these events can correlate to seismic signals in future lunar seismic networks, thereby providing useful physical constraints on impact processes. This approach would also allow stations equipped with a single telescope/camera to meaningfully contribute to the network.

astro-ph.EP

Mining the time axis with TRON. II. MeerKAT detects a stellar radio flare from a distant RS CVn candidate

Medium-timescale (minutes to hours) radio transients are a relatively unexplored population. The wide field-of-view and high instantaneous sensitivity of instruments such as MeerKAT provides an opportunity to probe this class of sources, using image-plane detection techniques. The previous letter in this series describes our project and associated TRON pipeline designed to mine archival MeerKAT data for transient and variable sources. In this letter, we report on a new transient, a radio flare, associated with Gaia DR3 6865945581361480448, a G type star, whose parallax places it at a distance of 1334 pc. Its duration and high degree of circular polarization suggests electron cyclotron maser instability as the mechanism, consistent with an RS CVn variable.

astro-ph.IM

Mining the time axis with TRON. I. Millisecond pulsars in Omega Centauri, Terzan 5 and 47 Tucanae detected through MeerKAT interferometric imaging

Medium-timescale (minutes to hours) radio transients are a relatively unexplored population. The wide field-of-view and high instantaneous sensitivity of instruments such as MeerKAT provides an opportunity to probe this class of sources, using image-plane detection techniques. We aim to systematically mine archival synthesis imaging data in order to search for medium-timescale transients and variables that are not detected by conventional long-track image synthesis techniques. We deploy a prototype blind transient and variable search pipeline named TRON. This processes calibrated visibility data, constructs high-time cadence images, performs a search for variability on multiple timescales, and extracts lightcurves for detected sources. As proof of concept, we apply it to three MeerKAT observations of globular clusters, known to host transient or variable sources. We detect a previously known eclipsing MSP suspected to be a `black widow' system, in the globular cluster Omega Centauri, with a light curve confirming the eclipsing nature of the emission. We detect a previously known `red back' eclipsing MSP in the globular cluster Terzan 5. Using observations of the globular cluster 47 Tucanae, we detect two known millisecond pulsars (MSPs), and one previously reported MSP candidate, with hints of eclipsing behaviour.

astro-ph.IM

Implicit media frames: Automated analysis of public debate on artificial sweeteners

The framing of issues in the mass media plays a crucial role in the public understanding of science and technology. This article contributes to research concerned with diachronic analysis of media frames by making an analytical distinction between implicit and explicit media frames, and by introducing an automated method for analysing diachronic changes of implicit frames. In particular, we apply a semantic maps method to a case study on the newspaper debate about artificial sweeteners, published in The New York Times (NYT) between 1980 and 2006. Our results show that the analysis of semantic changes enables us to filter out the dynamics of implicit frames, and to detect emerging metaphors in public debates. Theoretically, we discuss the relation between implicit frames in public debates and codification of information in scientific discourses, and suggest further avenues for research interested in the automated analysis of frame changes and trends in public debates.

cs.IR