The recurrent nova T CrB had prior eruptions observed near December 1787 and October 1217 AD (2308.13668v2)

Abstract: The famous recurrent nova (RN) T Coronae Borealis (T CrB) has had observed eruptions peaking at a visual magnitude of 2.0 in the years 1866 and 1946, while a third eruption is now expected for the year 2024.4+-0.3. Each RN has very similar light curves of eruptions that come with a fairly even-spacing in time, for which T CrB has a recurrence timescale near 80 years. So it is reasonable to look backwards in time for prior eruptions, around 1786, and so on back. I have investigated two long-lost suggestions that T CrB was seen in eruption in the years 1217 and 1787. (1) In a catalog published in 1789, the Reverend Francis Wollaston reports an astrometric position for a star that is exactly on top of T CrB. From his letters, these observations were made on at least four occassions with both a large and small telescope, within a few days before 1787 December 28. Wollaston's limiting magnitude for his astrometry is near 7.8 mag, so T CrB would have to have been in eruption. With other transients strongly rejected, the only way that Wollaston could get the coordinates was to have measured the coordinates of T CrB itself during an eruption. (2) The 1217 event has an eyewitness report written by Abbott Burchard of Upsberg as a fast-rising stellar point-source ("stella") in Corona Borealis that "shone with great light", lasted for "many days", and was ascribed as being a "wonderful sign". This event cannot be a report of a comet, because Burchard used the term for a star ("stella") and not for a comet, and because Burchard had the omen being very positive, with such being impossible for comets that are universally the worst of omens. The reported event is just as expected for a prior eruption of T CrB, and all other possibilities are strongly rejected, so the case for the 1217 eruption of T CrB is strong.

• The paper validates T CrB's recurrent eruptions in 1217 and 1787 through meticulous analysis of historical astronomical records and calculations.
• It refutes alternative explanations by leveraging precise astrometric coordinates and statistically improbable errors.
• The findings reinforce predictive nova models, enhancing observational preparations for T CrB's anticipated eruption around 2024.

Analysis of Historical Eruptions of Recurrent Nova T Coronae Borealis

This paper by Bradley E. Schaefer meticulously investigates the historical eruptions of T Coronae Borealis (T CrB), a well-known recurrent nova (RN) with previous eruptions recorded in 1866 and 1946, and corroborates its past activities in 1217 AD and December 1787. T CrB's predictable recurrence period of approximately 80 years establishes a reasonable basis for examining these prior events. The research endeavors to substantiate these historical eruptions using various primary sources and calculations.

Reported Eruptions and Supporting Evidence

The two particular temporal points scrutinized are the eruptions dated at 1217 AD and December 1787. The approach integrates evidence from historical astronomical catalogs and firsthand chronological accounts.

1. 1787 Eruption Evidence:
   • English astronomer Francis Wollaston documented observations in 1789 with coordinates aligning with T CrB's position, indicating a star visible only when T CrB would be in eruption.
   • An error in the coordinates that precisely places them on T CrB due to any cataloging mistake is statistically improbable (0.00028 probability), strongly supporting that T CrB's eruption was recorded instead of another celestial body.
2. 1217 Eruption Evidence:
   • Abbott Burchard’s chronicle describes a bright star in Corona Borealis, interpreted as a "wonderful sign." This observation fits recurrent nova characteristics: becoming bright suddenly, persisting for many days, and then disappearing.
   • The account dismisses comet-based explanations, underlined by linguistic distinctions in descriptions and the positive connotations of the event, attributes not typically associated with comets.

Rejection of Alternative Hypotheses

The research rigorously dispels potential alternative hypotheses involving sightings of other astronomical phenomena such as comets or non-eruptive variables due to:

• The specificity of terms used in historical accounts indicating point-source luminescence.
• The calculated improbability of chance occurrences matching T CrB’s position in Wollaston’s astrometry.
• Absence of sufficient evidence supporting the visibility of any such alternate objects during the specified periods.

Theoretical and Practical Implications

The validation of historical eruptions for T CrB enriches understanding of RN systems' temporal behavior and illuminates historical records' astronomical accuracy. Recognizing these eruptions provides reinforcement for the reliability of historical chronicles in capturing significant astronomical occurrences, expanding the modern historical data cache for stellar phenomena.

Moreover, this research exemplifies using historical documentation to provide a retrospective corroboration of astronomical models. T CrB's expected upcoming eruption, suggested for 2024.4±0.3, illustrates the value of quantitative predictions that potentially allow preemptive observational preparations for continuous data collection across recurrence cycles.

Speculation on Future Research

Extending this methodological framework to other potential historical nova records could refine our understanding of nova population statistics, recurrence behaviors, and offer a paradigm for examining astronomical events in the historical context. Such investigations could potentially enhance predictive models of stellar eruptive behavior, significant in the landscape of observational astronomy.

In conclusion, Schaefer’s analysis reinforces that T CrB’s documented 1217 and 1787 eruptions substantiate recurrent timeline predictions and validates historical data as a crucial component of contemporary astrophysical research modalities.