The historical 1900 and 1913 outbursts of the binary blazar candidate OJ287^⋆

¹ Astronomical Institute, Academy of Sciences of the Czech Republic, Fričova 298, 251 65 Ondřejov, Czech Republic
e-mail: rene.hudec@asu.cas.cz
² Czech Technical University, Faculty of Electrical Engineering, Technicka 2, 160 00 Praha 6, Czech Republic
³ Faculty of Informatics and Statistics, University of Economics, 130 67 Prague, Czech Republic
⁴ Department of Physics and Astronomy, University of Turku, 21500 Piikkio, Finland
⁵ Finnish Centre for Astronomy with ESO, University of Turku, 21500 Piikkio, Finland

Received: 31 March 2012
Accepted: 14 February 2013

Abstract

We report on historical optical outbursts in the OJ287 system in 1900 and 1913, detected on archival astronomical plates of the Harvard College Observatory. The 1900 outburst is reported for the first time. The first recorded outburst of the periodically active quasar OJ287 described before was observed in 1913. Up to now the information on this event was based on three points from plate archives. We used the Harvard plate collection, and added another seven observations to the light curve. The light curve is now well covered and allows one to determine the beginning of the outburst quite accurately. The outburst was longer and more energetic than the standard 1983 outburst. Should the system be strictly periodic, the period determined from these two outbursts would be 11.665 yr. However, this does not match the 1900 outburst or other prominent outbursts in the record. On the other hand, the precessing binary black hole model of Lehto and Valtonen (1996) can explain these and other known outbursts in OJ287. Finally, we discuss the upper limits for the expected 1906 outburst and the 1910 outburst, which was observed.