19 citations · 31 across the 9 of their papers we have counts for
9 papers
Earth-Projected Clustering of Historical Optical Transients in the Palomar Observatory Sky Survey-I (POSS-I)
Stephen Bruehl, Beatriz Villarroel, Hichem Guergouri +2
Palomar Observatory Sky Survey-I (POSS-I) images obtained before the launch of Sputnik contain star-like point sources consistent with sub-second flashes that are absent from all s…
Modelling Palomar Transients: Constraints from Reflection Geometry and Orbital Altitude
Beatriz Villarroel, Alina Streblyanska, Hichem Guergouri +3
Recent searches of digitised photographic plates from the Palomar Observatory have uncovered tens of thousands of short-lived transients, each visible in only a single exposure. Th…
Machine Learning Supports Existence of Previously Unrecognized Transient Astronomical Phenomena in Historical Observatory Images
Stephen Bruehl, Brian Doherty, Alina Streblyanska +1
Transient, star-like point sources that appear and vanish over short timescales are described in astronomical images prior to launch of Sputnik. We have reported that transient num…
A Response to paper Critical Evaluation of Studies Alleging Evidence for Technosignatures in the POSS1-E Photographic Plates by Watters et al. (2026)
Beatriz Villarroel, Alina Streblyanska, Stephen Bruehl +1
We respond to the critique by Watters et al. (2026) of the statistical analyses in Villarroel et al. (2025) and Bruehl & Villarroel (2025). We argue that the critique conflates obj…
A Cost-Effective Search for Extraterrestrial Probes in the Solar System
Beatriz Villarroel, Wesley A. Watters, Alina Streblyanska +3
For centuries, astronomers have discussed the possibility of inhabited worlds - from Herschel's 18th-century observations suggesting Mars may host life, to the systematic search fo…
A bright triple transient that vanished within 50 minutes
Enrique Solano, Geoffrey W. Marcy, Beatriz Villarroel +5
We report on three optically bright, ~15th mag, point-sources within 10 arcsec of each other that vanished within 1 hour, based on two consecutive exposures at Palomar Observatory…
The Accretion Mode in Sub-Eddington Supermassive Black Holes: Getting into the Central Parsecs of Andromeda
C. Alig, A. Prieto, M. Blaña +5
The inner kiloparsec regions surrounding sub-Eddington (luminosity less than 10 in Eddington units, L) supermassive black holes (BHs) often show a characteristic net…
Is there a background population of high-albedo objects in geosynchronous orbits around Earth?
Beatriz Villarroel, Enrique Solano, Hichem Guergouri +11
Old, digitized astronomical images taken before the human spacefaring age offer a unique view of the sky devoid of known artificial satellites. In this paper, we have carried out t…
Exploring nine simultaneously occurring transients on April 12th 1950
Beatriz Villarroel, Geoffrey W. Marcy, Stefan Geier +6
Nine point sources appeared within half an hour on a region within 10 arcmin of a red-sensitive photographic plate taken in April 1950 as part of the historic Palomar Sky Su…