Life after eruption - VII. A search for stunted outbursts in 13 post-novae

The results of a photometric campaign during three observing seasons 2013-2016 at the Cerro Tololo International Observatory (1.3-meter SMARTS telescope) are presented. The aim was to detect 'stunted' outbursts in a total of 13 post-novae more than 38 yr after maximum brightness registered in their nova eruption light curve. In six of the targets (V728 Sco 1862, V1059 Sgr 1898, V849 Oph 1919, V363 Sgr 1927, HS Pup 1963, and V2572 Sgr 1969), we detected such dwarf nova-like mini-outbursts, with mean amplitudes between 0.2(m) and 2.2(m) and typical full width at half maximum of 4-11 d, repeating every 9-32 d. The most regular outburst behaviour is present in the eclipsing post-nova V728 Sco. In our sample, there is no significant correlation between the occurrences of stunted outbursts and the time passed since the nova eruption maximum. However, considering all 15 post-novae that have been reported to show stunted outbursts, we found a possible tendency for increasing outburst amplitudes at the rate 0.52 +/- 0.23 mag century(-1) during 30-250 yr after nova eruption. This tendency is still doubtful due to the low number of cases available. If the stunted outburst activity is related to the mass transfer rate (M) over dot, we conclude that the secular decrease of (M) over dot predicted by the hibernation scenario must be at much longer time scales than similar to 200 yr actually covered with post-nova observations.