Tolga Dinçer | Searcharxiv

arXiv2026

Boundary Density Likelihood for Direct Event-Time Supervision

Event detection turns long recordings into a sparse set of ranked timestamps. Yet many sequence models are trained for samplewise segmentation and only convert predicted states into events after training. We ask whether training directly for the evaluated output improves detection. Boundary Density Likelihood (BDL) assigns one unit of target mass to each annotated event, preserves that mass through smoothing and temporal downsampling, and uses a Poisson objective to estimate expected event mass in each output bin; local peaks become ranked detections. In a prespecified five-fold nested sleep study, BDL-Hard raises pooled out-of-fold mAP from 0.586 to 0.705 over interval segmentation (+11.9 percentage points; 95% interval [10.8, 13.0]) and strict one-minute AP from 0.071 to 0.286 (4.0x; +21.5 points), improving on every outer fold. A separate held-out rerun reproduces the direction of the effect. A matched boundary-BCE detector reaches 0.702 mAP, showing that direct boundary supervision and event decoding account for most of the gain, with a smaller contribution from the Poisson objective. The same trend appears with an offline convolutional model; causal, Transformer, and patient-grouped seizure experiments leave broader generalization unresolved. Our results support training on event times when timestamps define the evaluated output.

cs.AI↗

arXiv2019

ALMA observations of A0620-00: fresh clues on the nature of quiescent black hole X-ray binary jets

We report on ALMA continuum observations of the black hole X-ray binary A0620-00, at an X-ray luminosity nine orders of magnitude sub-Eddington. The system was significantly detected at 98 GHz (at $44 \pm 7~μ{\rm Jy}$) and only marginally at 233 GHz ($20 \pm 8~μ{\rm Jy}$), about 40 days later. These results suggest either an optically thin sub-mm synchrotron spectrum, or highly variable sub-mm jet emission on month timescales. Although the latter appears more likely, we note that, at the time of the ALMA observations, A0620-00 was in a somewhat less active optical-IR state than during all published multi-wavelength campaigns when a flat-spectrum, partially self-absorbed jet has been suggested to extend from the radio to the mid-IR regime. Either interpretation is viable in the context of an internal shock model, where the jet's spectral shape and variability are set by the power density spectrum of the shells' Lorentz factor fluctuations. While strictly simultaneous radio-mm-IR observations are necessary to draw definitive conclusions for A0620-00, the data presented here, in combination with recent radio and sub-mm results from higher luminosity systems, demonstrate that jets from black hole X-ray binaries exhibit a high level of variability - either in flux density or intrinsic spectral shape, or both - across a wide spectrum of Eddington ratios. This is not in contrast with expectations from an internal shock model, where lower jet power systems can be expected to exhibit larger fractional variability owing to an overall decrease in synchrotron absorption.

astro-ph.HE↗