of TCoronae Borealis during the time surrounding its 1946eruption, plotted from
AAVSOdata T CrB normally has a
magnitude of about10, which is near the limit of typical binoculars. Two well-documented outbursts have been observed, reaching magnitude2.0 on May12, 1866 and magnitude3.0 on February9, 1946, but easily visible to the naked eye. T CrB is a
binary system containing a large cool component and a smaller hot component. The cool component is a
red giant that transfers material to the hot component. The hot component, which initially was the most massive and brightest of the two stars, is now a
white dwarf surrounded by an
accretion disc, all hidden inside a dense cloud of material from the red giant. When the system is
quiescent, the red giant dominates the visible light output and the system appears as an
M3giant. The hot component contributes some emission and dominates the
ultraviolet output. During outbursts, the transfer of material to the hot component increases greatly, the hot component expands, and the overall luminosity of the system increases by orders of magnitude. light curve of
recurrent nova TCrB from Jan1, 2008 to Nov17, 2010, showing
rotating ellipsoidal variability. Up is brighter and down is fainter. Day numbers are
Julianday. The two components of the system orbit each other every . The orbit is almost circular and is
inclined at an angle of61.5°. The radius of the orbit of the primary component around
the center of mass is. ==2016–present activity==