Multiwavelength observations of nova LMC 1990 number 2: The first extragalactic recurrent nova¹

We present IUE and optical observations of Nova LMC 1990 Number 2, the first recurrent nova to be observed outside the Milky Way. The earlier optical outburst of the nova was observed in 1968, when it reached a maximum of about V = 10.9. IUE spectra were obtained between 1990 February 16 and March 26, with 8 hr resolution during the first day of observations. The ultraviolet observations reported here caught the nova at UV maximum; no P Cygni profiles developed on the resonance lines, suggesting that very little mass was ejected and the outburst was not spherical. The integrated UV luminosity at UV maximum was 2.9 × 10³⁸ ergs s^-1. Thus the luminosity exceeded the Eddington limit for a one solar mass white dwarf [assuming E(B - V) = 0.15 and a distance of 55 kpc to the LMC]. This is the first time that the luminosity of a recurrent nova has been directly obtained.