Dramatic change in the boundary layer in the symbiotic recurrent nova T Coronae Borealis

LUNA, G. J. M.; MUKAI, K.; SOKOLOSKI, J. L.; NELSON, T.; KUIN, P.; SEGRETO, A.; CUSUMANO, G.; JAQUE ARANCIBIA, M.; NUÑEZ, N. E.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2018 vol. 619

0004-6361

A sudden increase in the rate at which material reaches the most internal part of an accretion disk, i.e., the boundary layer, can change its structure dramatically. We have witnessed such a change for the first time in the symbiotic recurrent nova T CrB. Our analysis of XMM-Newton, Swift Burst Alert Telescope (BAT)/X-Ray Telescope (XRT)/UltraViolet Optical Telescope (UVOT), and the American Association of Variable Stars Observers (AAVSO) V- and B-band data indicates that during an optical brightening event that started in early 2014 (∆V ≈ 1.5) the following occurred: (i) the hard X-ray emission as seen with BAT almost vanished; (ii) the XRT X-ray flux decreased significantly, while the optical flux remained high; (iii) the UV flux increased by at least a factor of 40 over the quiescent value; and (iv) the X-ray spectrum became much softer and a bright, new blackbody-like component appeared. We suggest that theoptical brightening event, which could be a similar event to that observed about 8 years before the most recent thermonuclear outburstin 1946, is due to a disk instability.