A multiwavelength light curve analysis of the classical nova KT Eri: Optical contribution from a large irradiated accretion disk

Abstract

KT Eri is a classical nova which went into outburst in 2009. Recent photometric analysis in quiescence indicates a relatively longer orbital period of 2.6 days, so that KT Eri could host a very bright accretion disk during the outburst like in the recurrent nova U Sco, the orbital period of which is 1.23 days. We reproduced the optical $V$ light curve as well as the supersoft X-ray light curve of KT Eri in outburst, assuming a large irradiated disk during a nova wind phase of the outburst while a normal size disk after the nova winds stop. This result is consistent with the temporal variation of wide-band $V$ brightness that varies almost with the intermediate-band Str\"omgren $y$ brightness, because the $V$ flux is dominated by continuum radiation, the origin of which is a photospheric emission from the very bright disk. We obtained the white dwarf mass to be $M_{\rm WD}= 1.3\pm0.02 ~M_\odot$, the hydrogen-burning turnoff epoch to be $\sim 240$ days after the outburst, the distance modulus in the $V$ band to be $(m-M)_V=13.4\pm 0.2$, and the distance to KT Eri to be $d=4.2\pm0.4$ kpc for the reddening of $E(B-V)= 0.08$. The peak absolute $V$ brightness is about $M_{V, \rm max}= -8.0$ and the corresponding recurrence time is $\sim 3,000$ yr from its ignition mass together with the mean mass-accretion rate of $\dot{M}_{\rm acc}\sim 1\times 10^{-9} ~M_\odot$ yr$^{-1}$ in quiescence. Thus, we suggest that KT Eri is not a recurrent nova.