Finding radio transients with anomaly detection and active learning based on volunteer classifications
(2024)
The Radio Counterpart to the Fast X-ray Transient EP240414a
(2024)
A Radio Flare in the Long-lived Afterglow of the Distant Short GRB 210726A: Energy Injection or a Reverse Shock from Shell Collisions?
The Astrophysical Journal American Astronomical Society 970:2 (2024) 139
Abstract:
We present the discovery of the radio afterglow of the short gamma-ray burst (GRB) 210726A, localized to a galaxy at a photometric redshift of z 鈭 2.4. While radio observations commenced 鈮1 day after the burst, no radio emission was detected until 鈭11 days. The radio afterglow subsequently brightened by a factor of 鈭3 in the span of a week, followed by a rapid decay (a 鈥渞adio flare鈥). We find that a forward shock afterglow model cannot self-consistently describe the multiwavelength X-ray and radio data, and underpredicts the flux of the radio flare by a factor of 鈮5. We find that the addition of substantial energy injection, which increases the isotropic kinetic energy of the burst by a factor of 鈮4, or a reverse shock from a shell collision are viable solutions to match the broadband behavior. At z 鈭 2.4, GRB 210726A is among the highest-redshift short GRBs discovered to date, as well as the most luminous in radio and X-rays. Combining and comparing all previous radio afterglow observations of short GRBs, we find that the majority of published radio searches conclude by 鈮10 days after the burst, potentially missing these late-rising, luminous radio afterglows.Discovery of the Optical and Radio Counterpart to the Fast X-Ray Transient EP 240315a
The Astrophysical Journal Letters American Astronomical Society 969:1 (2024) L14
Abstract:
Fast X-ray Transients (FXTs) are extragalactic bursts of soft X-rays first identified 鈮10 yr ago. Since then, nearly 40 events have been discovered, although almost all of these have been recovered from archival Chandra and XMM-Newton data. To date, optical sky surveys and follow-up searches have not revealed any multiwavelength counterparts. The Einstein Probe, launched in 2024 January, has started surveying the sky in the soft X-ray regime (0.5鈥4 keV) and will rapidly increase the sample of FXTs discovered in real time. Here we report the first discovery of both an optical and radio counterpart to a distant FXT, the fourth source publicly released by the Einstein Probe. We discovered a fast-fading optical transient within the 3鈥 localization radius of EP 240315a with the all-sky optical survey ATLAS, and our follow-up Gemini spectrum provides a redshift, z = 4.859 卤 0.002. Furthermore, we uncovered a radio counterpart in the S band (3.0 GHz) with the MeerKAT radio interferometer. The optical (rest-frame UV) and radio luminosities indicate that the FXT most likely originates from either a long gamma-ray burst or a relativistic tidal disruption event. This may be a fortuitous early mission detection by the Einstein Probe or may signpost a mode of discovery for high-redshift, high-energy transients through soft X-ray surveys, combined with locating multiwavelength counterparts.
Magnetomyography: A novel modality for non-invasive muscle sensing
bioRxiv preprint 2024.04:15.588623 (2024)
Abstract:
The measurement of magnetic fields generated by skeletal muscle activity, called magnetomyography (MMG), has seen renewed interest from the academic community in recent years. Although studies have demonstrated complex models of MMG and experiments classifying between different movements using MMG, there has yet to be time frequency analysis of MMG as well as concurrent recordings of MMG and its electrical counterpart, surface electromyography (sEMG). Here, we aim to better understand MMG in the context of sEMG by simultaneously recording both modalities during various muscle contraction tasks. We found that, similar to sEMG, MMG shows highly linearly correlated power to the degree of muscle contraction, has a unimodal distribution in spectral power, and can detect changes in muscle fatigue via changes in the spectral distribution. One main difference we found was that MMG typically has more high frequency content compared to sEMG, even when accounting for the filtering induced by the size of the sEMG electrodes. We additionally demonstrate empirically the decrease in MMG power due to distance from the arm and show MMG decreases slower than the inverse square law and can be measured up to 50 mm from the surface of the skin. Finally, we were able to capture MMG with non-OPM sensors showing that sensor technology has made great strides towards enabling MMG applications.