The Recurrent Nova T CrB Did Not Erupt in 1842

TL;DR

This study investigates historical claims of a 1842 eruption of the recurrent nova T CrB, using archival research to clarify that Herschel's observations did not indicate such an eruption, thus confirming no eruption occurred in 1842.

Contribution

The paper provides definitive archival evidence that refutes the previously ambiguous claim of a 1842 eruption of T CrB, clarifying its eruption history.

Findings

Herschel's 1842 observation was of a background star, not T CrB.

No evidence supports an eruption of T CrB in 1842.

Herschel's observations were limited by his equipment, affecting star visibility.

Abstract

The recurrent nova T CrB was one of the first well observed nova eruptions in 1866, and 80 years later it erupted again in 1946. Just after the 1866 eruption, Sir John Herschel reported to the Monthly Notices that he had seen the same star in his naked-eye charting of the sky on 1842 June 9, implying that there was a prior eruption 24 years earlier. Unfortunately, the chart in the Monthly Notices was ambiguous and misleading, so it has long been unclear whether T CrB did indeed have an eruption in 1842. To resolve this, I have searched the various archives with Herschel material, and have found his original correspondence. In one letter from 1866 to William Huggins, Herschel enclosed his own copy of his original observations, and with this all the ambiguities are resolved. It turns out that Herschel's indicated star was at the same position as a steady background star (BD+25{\deg}3020, V=7.06, G8V) and not that of T CrB, and Herschel regularly was seeing stars as faint as V=7.5 mag because he was using an opera glass. With this, there is no evidence for a T CrB eruption in 1842.