Disks as stellar-merger remnatns: the case of V4332 Sgr and V1309 Sco

Red novae are a new class of eruptive variables observed in the Milky Way and Local Group galaxies. Their eruptions are thought to be due to stellar collisions and subsequent mergers. Only recently it has been convincingly shown that one of the red novae, V1309 Sco, was a contact binary prior to its eruption. Thanks to accurate photometry from OGLE going years before the eruption we could trace the shortening of the orbital period in V1309 Sco as it was evolving toward a merger. The OGLE light curve suggests that a disk or disklike feature was formed just before the main outburst of V1309 Sco. A disk is known to be present around another, older red nova V4332 Sgr. Such disks are expected to form during and after a merger as they accumulate angular momentum that has to be lost during the spirallingin process. It has been suggested that from such disks .second generation. of planets can form. This hypothesis was introduced to explain the nature of the somewhat peculiar planets, called inflated hot Jupiters. We propose to perform PACS and SPIRE photometry of the two red novae, V1309 Sco and V4332 Sgr. The farinfrared fluxes will be used to construct full spectral energy distributions of these objects, from optical to radio wavelengths. Detailed radiativetransfer modelling of the disks will determine their main parameters, i.e. mass, sizes, and dust properties. The disk parameters will be used to study the physics of a merger event. Of main interest are the disk mass and the angular momentum deposited in the star and the disk. Knowing the disk mass will allow us to test the planet formation hypothesis. By comparing the old disk of V4332 Sgr with the newly formed one in V1309 Sco, and by analysing multiepoch variability in the disk of V4332 Sgr (the Herschel data will be compared to older Spitzer and AKARI data) we hope to gain insight on the disk formation process. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]