On the Image Profiles of Transients in the Palomar Sky Survey

TL;DR

This paper investigates short-lived transient objects in the Palomar Sky Survey, suggesting their sharp, round profiles are consistent with unresolved optical flashes rather than artifacts, supporting their transient nature.

Contribution

It provides an analysis linking the observed profiles of transients to optical physics, challenging previous attributions to emulsion flaws and supporting their classification as genuine short-lived phenomena.

Findings

Profiles are consistent with unresolved optical flashes.

Optical physics explains the sharp, round appearance of transients.

Findings support the transient interpretation over emulsion flaw explanations.

Abstract

The VASCO project has discovered groups of short-lived transients on historical photographic plates that lack conventional explanation. Hambly & Blair (2024) examined nine such transients reported by Villarroel (2021) and found that they exhibit narrower, rounder profiles, attributing this to emulsion flaws. However, well-established optical principles and atmospheric physics imply that unresolved flashes lasting less than a second naturally appear sharper and more circular than stellar images, particularly on long-exposure plates where stars are significantly blurred by seeing and tracking errors. Such profiles are an expected consequence of sub-second optical flashes, making their findings consistent with the transient interpretation.