The Vanishing & Appearing Sources during a Century of Observations project: I. USNO objects missing in modern sky surveys and follow-up observations of a "missing star" (1911.05068v2)

Abstract: In this paper we report the current status of a new research program. The primary goal of the "Vanishing & Appearing Sources during a Century of Observations" (VASCO) project is to search for vanishing and appearing sources using existing survey data to find examples of exceptional astrophysical transients. The implications of finding such objects extend from traditional astrophysics fields to the more exotic searches for evidence of technologically advanced civilizations. In this first paper we present new, deeper observations of the tentative candidate discovered by Villarroel et al. (2016). We then perform the first searches for vanishing objects throughout the sky by comparing 600 million objects from the US Naval Observatory Catalogue (USNO) B1.0 down to a limiting magnitude of $\sim 20 - 21$ with the recent Pan-STARRS Data Release-1 (DR1) with a limiting magnitude of $\sim$ 23.4. We find about 150,000 preliminary candidates that do not have any Pan-STARRS counterpart within a 30 arcsec radius. We show that these objects are redder and have larger proper motions than typical USNO objects. We visually examine the images for a subset of about 24,000 candidates, superseding the 2016 study with a sample ten times larger. We find about $\sim$ 100 point sources visible in only one epoch in the red band of the USNO which may be of interest in searches for strong M dwarf flares, high-redshift supernovae or other catagories of unidentified red transients.

• The paper identifies roughly 100 transient point sources from USNO data, suggesting associations with phenomena like M dwarf flares or high-redshift supernovae.
• It employs a systematic cross-match of 600 million catalog entries with a 30-arcsecond filter and visual inspection of 24,000 candidates to pinpoint anomalies.
• The findings highlight potential for enhanced detection algorithms, integration of broader sky surveys, and deeper exploration of rare astrophysical events.

An Overview of "The Vanishing and Appearing Sources during a Century of Observations" Project

The paper by Villarroel et al. explores an intriguing aspect of astrophysics: the potential identification of celestial objects that appear or vanish when comparing mid-20th-century sky surveys with contemporary observations. This paper outlines the first findings of the "Vanishing and Appearing Sources during a Century of Observations" (VASCO) project, focusing on discrepancies between objects cataloged by the United States Naval Observatory (USNO) and the modern Pan-STARRS surveys.

Key Methodologies

The authors conducted a systematic cross-match between approximately 600 million entries from the USNO B1.0 catalog and the Pan-STARRS Data Release 1, with the latter having a deeper limiting magnitude of around 23.4, compared to USNO's 20-21. By examining objects without modern counterparts within a 30 arcsecond radius, approximately 150,000 preliminary candidates were identified. A subset of around 24,000 of these candidates was visually inspected, focusing on those that appeared as point sources only in single epochs, specifically within the red band of the USNO plates.

Significant Findings

The paper found approximately 100 point sources of interest that were detected in only one epoch from the USNO data. These candidates could potentially be linked to exceptional astrophysical phenomena, such as strong M dwarf flares or high-redshift supernovae. The initial search for vanishing stars estimated the likelihood of such events as less than one in 90 million, over the evaluated 70-year span.

Analysis and Interpretation

The project's findings suggest that certain previously cataloged objects show significant proper motion and appear redder than typical objects, indicating their potential as astrophysical transients. Since none of the examined candidates were found to have consistent counterparts in the General Catalogue of Variable Stars within a 30 arcsecond radius, they might represent new classes of high-variability astronomical entities or possibly indications of unknown phenomena.

Implications and Future Directions

The VASCO project presents a cross-disciplinary potential, reaching into both traditional and speculative domains of astrophysics. Notably, the possibility of linking such findings to the search for extraterrestrial intelligence (SETI) is mentioned, as disappearing stars could hypothetically indicate advanced technological activities, such as Dyson spheres or other forms of astroengineering.

From a theoretical perspective, the paper raises compelling questions about the nature and frequency of failed supernovae and their observational signatures. The projected finding probability within the paper's data timeline aligns with theoretical predictions that such events may be quite rare.

The paper opens pathways for several future research directions:

1. Enhancing detection algorithms: To improve precision in future surveys by minimizing false positives while increasing sensitivity to authentic vanishings and emergences.
2. Broader sky survey integrations: Extending the dataset to include data from other sky surveys, facilitating a more comprehensive temporal coverage.
3. Deep learning applications: Utilizing machine learning and artificial intelligence to process large datasets more efficiently, thereby augmenting the project's capacity to deal with massive amounts of visual data.

In conclusion, the findings from Villarroel et al.'s analysis underscore the value of historic astronomical data when reanalyzed with modern tools and methodologies, providing both a window into our astrophysical past and a glimpse of extraordinary celestial phenomena that await further exploration.