TESS Special Bulletin: May 15th

News article posted on by Rebekah Hounsell

Welcome TESS followers to this special news bulletin high-lighting an extra extraordinary object that may be observed by TESS in the coming months, T CrB!

T Coronae Borealis (T CrB for short) is a recurrent novae (RNe) located 3,000 light years away in the constellation of Corona Borealis. It is one of only a few known RNe in our galaxy and has a recurrence period of 80 years, with its last eruption observed in 1946.

Like all novae, T CrB is a binary system consisting of a White Dwarf (WD, ~1.2 - 1.37 MSun) pulling hydrogen rich material from the surface of a secondary star via an accretion disc. The secondary star in this case is red giant which dominates the optical and infrared light of the system. The nova outburst observed is caused by a thermonuclear runaway in the collected material on the surface of the WD, and in the case of T CrB the outburst is spectacular!

In previous outburst events the T CrB was seen to increase from a quiescence magnitude of ~10 mags in V, to a shocking naked eye brightness of 2 mags - this is comparable to Polaris!

T CrB is also interesting in that it has a pre-outburst tell, alerting the community that it will soon go nova. This tell comes in the form of a dip in the light curve about a year before eruption. This dip was observed by Louisiana State scientists in March/April of last year, meaning that T CrB should go nova any day now.

If the event happens between April 23rd and May 21st it will also be observed serendipitously by TESS in Sector 78. TESS has already observed the system in quiescence during Sectors 24, 25, and 51 (see Fig 1), but if the nova has an outburst in S78, TESS will obtain a wonderful light curve of its rise and decline.


Fig. 1: Plot of TCr B data taken by TESS and the All-Sky Automated Survey for Supernovae (ASAS-SN).