The Dwarf Nova Outbursts of Nova Her 1960 (=V446 Her)

TL;DR

This study presents a 19-year photometric analysis of V446 Her, revealing long-term decline in brightness, bimodal outburst properties, and changes in outburst patterns potentially linked to post-nova accretion rate decline.

Contribution

It provides the first detailed long-term light curve analysis of V446 Her, confirming bimodal outburst distributions and observing pattern changes related to post-nova evolution.

Findings

Outburst magnitudes decline at ~0.013 mag/yr.

Bimodal distributions of outburst amplitudes and widths are confirmed.

Disappearance of brighter, wider outbursts after 2003 suggests decreasing accretion rate.

Abstract

V446 Her is the best example of an old nova which has developed dwarf nova eruptions in the post-nova state. We report on observed properties of the long-term light curve of V446 Her, using photometry over 19 years. Yearly averages of the outburst magnitudes shows a decline of ~0.013 mag/yr, consistent with the decline of other post-novae that do not have dwarf nova outbursts. Previous suggestions of bimodal distributions of the amplitudes and widths of the outbursts are confirmed. The outbursts occur at a mean spacing of 18 days but the range of spacings is large (13-30 days). From simulations of dwarf nova outbursts it has been predicted that the outburst spacing in V446 Her will increase as M-dot from the red dwarf companion slowly falls following the nova; however the large intrinsic scatter in the spacings serves to hide any evidence of this effect. We do find a systematic change in the outburst pattern in which the brighter, wider type of outbursts disappeared after late 2003, and this phenomenon is suggested to be due to falling M-dot following the nova.