Sonneberg plate photometry for Boyajian's Star in two passbands

TL;DR

This study analyzes historic Sonneberg Observatory plates to investigate long-term brightness changes of Boyajian's Star, finding no significant dimming over the past century, thus challenging previous claims of a 20% decline.

Contribution

Provides an independent analysis of historic photographic plates, offering new constraints on the star's long-term brightness variations and refuting earlier claims of significant dimming.

Findings

Star's brightness constant within 0.03 mag per century

No evidence of 20% long-term dimming

Possible dimming event observed in 1978

Abstract

The F3 main sequence star KIC 8462852 (Boyajian's Star) showed deep (up to 20%) day-long brightness dips of unknown cause during the 4 years of the Kepler mission. A 0.164 mag (16%) dimming between 1890 and 1990 was claimed, based on the analysis of photographic plates from the Harvard Observatory. We have gathered an independent set of historic plates from Sonneberg Observatory, Germany, covering the years 1934-1995. With 861 magnitudes in B, and 397 magnitudes in V, we find the star to be of constant brightness within 0.03 mag per century (3%). Consistent outcomes are found using by-eye estimates of the best 119 plates. Results are supported by data from Sternberg Observatory, Moscow, which show the star as constant between 1895 and 1995. The previously claimed century-long dimming is inconsistent with our results at the 5-sigma level, however the recently reported modest dimming of 3% in the Kepler data is not inconsistent with our data. We find no periodicities or shorter trends within our limits of 5% per 5-year bin, but note a possible dimming event on 24 Oct 1978.