The problem of the high mass of the hot component in the recurrent nova T Coronae Borealis solved after 38 years

Abstract. In this paper, we present long-term spectroscopicobservationsoftherecurrentnova(RN)TCrBobtainedbetweenthe years 1985 and 1996 using 1.02 m and 2.34 m telescopesof the Vainu Bappu Observatory in India and the long-termphotoelectric photometry of the object obtained mainly at theSkalnat´e Pleso Observatory and at the Hlohovec Observatoryin Slovakia. On the basis of our results, we have returned to there-analysis of the old radial-velocity measurements publishedby Kraft (1958). The results obtained solve unambiguously theproblem of the apparently too high mass of the hot componentof T CrB, unacceptable if it has to be a white dwarf (WD), asseveral independent lines of evidence suggest.Key words: stars: individual: T CrB – novae, cataclysmic vari-ables – white dwarfs1. IntroductionThe recurrent nova T CrB has become the first cataclysmic vari-able (CV) studied spectroscopically when it reached the bright-nessof2ndmagnitudeduringitsoutburstinMay1866.Huggins(1866) then observed the hydrogen emissions superimposed ona weak absorbtion-line spectrum through a visual spectroscope.The object was studied intensively immediately after its secondoutburst in February 1946 when T CrB became the brightestrecurrent nova in history. The photometric observations werepublished by Pettit (1946) who compared the development ofthe light curves of both large outbursts of this nova that havebeen recorded up to now, i.e., in 1866 and 1946.Sanford (1949) detected for the first time the radial veloc-ity variations resulting from the orbital motion with a period of230.5 days. The most precise analysis of the radial velocitiesof both components was presented by Kraft (1958) who deter-mined the orbital elements of the binary system as well as themasses of both components. The radial velocity curve adoptedfrom his paper is displayed in Fig. 1. Kraft’s work has playedthe crucial role in further development of opinions related toT CrB, this involving especially the mass of the hot component