Variable Stars - T Crb
Type Recurrent Novae, Rotating Ellipsoidal Click for lightcurve Recurrent novae, which differ from typical novae by the fact that two or more outbursts (instead of a single one) separated by 10-80 years have been observed. Rotating ellipsoidal variables are close binary systems with ellipsoidal components, which change combined brightnesses with periods equal to those of orbital motion because of changes in emitting areas toward an observer, but showing no eclipses. Light amplitudes usually do not exceed 0.1 magnitudes in V. AAVSO Special Notice 415 April 8, 2016 T CrB brighter and bluer - monitoring requested The symbiotic recurrent nova T CrB has entered a super- active state, and it is brighter and bluer than it has been since before its last outburst in 1946. Multicolor and visual ongoing observations are requested. Visual and multicolor observations in the AAVSO International Database show that the average magnitude of T CrB was V ~ 10.2-10.3 until early February 2015. Its average magnitude then brightened to V ~ 10.0 and remained there until early February 2016, when it began brightening again and has currently reached V ~ 9.2. The B-V is roughly half what it was two years ago. T CrB has been observed twice in outburst, in 1866 and 1946. Each time it brightened rapidly to V ~2.0, then declined back to pre-outburst levels. A recent paper by U. Munari, S. Dallaporta, and G. Cherini (http://arxiv.org/pdf/1602.07470.pdf) gives an analysis of the current behavior and the 1947-2016 behavior. Their abstract  begins: "The recurrent nova T CrB has entered in 2015 a phase of unprecedented high activity. To trace something equivalent, it is necessary to go back to 1938, before the last nova eruption in 1946. The 2015 super-active state is characterized by: a large increase in the mean brightness (Delta B =0.72 mag over the uderlying secular trend), vanishing of the orbital modulation from the B-band lightcurve, and appearance of strong and high ionization emission lines, on top of a nebular continuum that overwhelms at optical wavelengths the absoption spectrum of the M giant..." Munari et al. include over 120,000 AAVSO observations in studying the 1947-2016 optical behavior. They point out that the AAVSO data show a few intervals when T CrB was brighter than its average post-outburst magnitude, but nothing approaching its current state. They also point out that, as far as they are aware, the only other time T CrB was in a super-active state was in 1938 (Hachenberg and Wellmann 1939 in Munari et al.), ~70 years after the 1866 outburst, and that the current super-active state is occuring ~70 years after the 1946 outburst. They conclude by wondering if an outburst of T CrB may be on the horizon for 2026 (80 years since the 1946 outburst, the same interval between the 1866 and 1946 outbursts). Following up on Munari et al., R. Zamanov et al. report in ATel#8675 (http://www.astronomerstelegram.org/?read=8675) that their observations of 7 February 2016 show that T CrB is brighter in B and U but that the amplitude of flickering in B and U has decreased. For now, nightly observations are requested, in V and B if possible.
Hills Observatory: 1 January 2013 to 4 November 2018
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