We present a spectroscopic monitoring of the transient nova V4745 Sagittarii ( Nova Sgr 2003 # 1 ) covering ten months after the discovery .
During this period the light curve showed well expressed transient phase in the form of six rebrightenings , and the presented dataset is one of the best spectroscopic coverages of a classical nova during the transition phase .
Low- and medium-resolution spectra revealed that the majority of spectral lines switched back to strong P-Cyg profiles during the mini-outbursts , similar to the spectra just after the major eruption .
We interpret the observed phenomena as evidence for “ echo-outbursts ” resulting in episodes of secondary mass-ejections and propose that the transition phase in classical novae is driven by repetitive instabilities of the hydrogen shell burning on the surface of the white dwarf .
From the available light curve data we estimate the absolute magnitude of the system of about -8 \aas@@fstack { m } 3 \pm 0 \aas@@fstack { m } 5 .
All spectrophotometric pieces of evidence point toward a very low ( E ( B - V ) < 0 \aas@@fstack { m } 1 ) interstellar reddening , leading to a rough distance estimate of V4745 Sgr ( 9 ~ { } { kpc } < d < 19 ~ { } { kpc } ) .