A New Clue to the Secondary Maxima of Novae


Classical novae show a wide variety of timescales and shapes in the optical light curves. Among various shapes of nova light curves, V1493 Aql (Nova Aquilae 1999 No.1) shows an impressive secondary maximum about 50 days after the outburst, although the physical mechanism of the secondary maximum is not understood yet. Recent two novae, V2362 Cyg (Nova Cygni 2006) and V2491 Cyg (Nova Cygni 2008 No.2), also show a similar type of single secondary maximum, at about 250 and 15 days after the outburst, respectively. These three novae form a wide variety set of timescales, i.e., about 15, 50, and 250 days at the secondary maximum and of secondary peak heights, i.e., 1.1, 2.8, and 3.6 mag, respectively, which provide us a new clue to the mechanism of the secondary maxima.

Here we propose a strong magnetic activity as the mechanism of the secondary maxima observed in V2491 Cyg, V1493 Aql, and V2362 Cyg, using the white dwarf parameters obtained from light curve fittings based on an optically thick wind model of nova outbursts. The timescales of the secondary maxima in V2491 Cyg, V1493 Aql, and V2362 Cyg are very different but are explained by our mechanism.

1. Optical Light Curves of V1493 Aql

An impressive secondary peak at about 50 days after the outburst.

2. Optical Light Curves of V2362 Cyg

The secondary peak at 250 days after the outburst.

3. Optical and Supersoft X-ray Light Curves of V2491 Cyg

black: y-magnitude of the current outburst,
orange: visual magnitude, VSOLJ (traiangle)、square (IAUC) red dots(AAVSO)
yellow dot :previous outburst (1985)(AAVSO)
yellow line: the mean light curve composed from 5 revious outbursts (by Rosino)

4. Magnetic Energy Density in Nova Envelope

5. Timescales of the Secondary Maxima

taken from "Optical and Supersoft X-ray Light Curve Models of Classical Nova V2491 Cygni: A New Clue to the Secondary Maximum" by Izumi Hachisu and Mariko Kato, ApJL,694, L103-L106 (2009) or astro-ph/arXiv:0902.2424 :

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Copyright M. Kato 2009