On the narrow emission line components of the LMC novae 2004 (YY Doradus) and 2009a

¹ INAF Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34134 Trieste, Italy
e-mail: mason@oats.inaf.it
² INAF Osservatorio Astronomico di Padova, 36012 Asiago (VI), Italy

Received: 26 May 2014
Accepted: 13 August 2014

Abstract

We present early decline spectra of the two Large Magellanic Cloud novae: LMC 2004 (YY Dor) and LMC 2009a and discuss their spectral an line profile evolution with special emphasis on the existence and appearance of a sharp component. We show that the narrow component that characterizes the emission lines in the maximum spectra of nova LMC 2004 originates in the ejecta. The He ii 4686 Å  narrow emission which appears at the onset of the nebular phase in both novae is somewhat controversial. Our observations suggest that the corresponding line forming region is physically separated from the rest of the ejecta (the broad line region) and environmentally different. However, the lack of late time observations covering the super-soft source (SSS) phase, the post-SSS phase and the quiescence state does not allow to securely establish any non-ejecta origin/contribution as, instead, in the case of U Sco and KT Eri.