The seminar will be held in a mixed mode

1) Speaker: R. Manick (SAAO, Cape Town, South Africa)

Title: “Discovery of a long orbital period binary in the nucleus of the bipolar proto-planetary nebula: IRAS 08005-2356”

Abstract: Current models predict that a binary nucleus is an essential ingredient in producing bipolar structures seen among pre-planetary nebulae (PPNe). Despite years of attempts to detect binaries in them, there has been a paucity of known binaries amongst PPNe.

In this talk, I will present our recent results on the discovery of a binary central star in the bipolar pre-planetary nebula: IRAS 08005-2356 (V510 Pup). We have used nearly 27 years of spectroscopic time series observations from SALT HRS, CTIO CHIRON and archival data to constrain an orbital period of 2608±121 d. Currently, this is the longest period binary in a PPN and arguably only the third known binary in a PPN after the Red Rectangle and HD101584.
The spectroscopic orbit is fit with an eccentricity of 0.36 ± 0.04 and is consistent with other long period post-AGB binaries and binary central stars of planetary nebulae (CSPNe). I will also present nearly 24 years of near-IR SAAO photometric time series, collected by Patricia Whitelock and colleagues, which varies with a period of ∼ 2727 ± 26 d and is within the limits of the orbital period derived from the radial velocities. Time resolved H-alpha profiles reveal high-velocity outflows (jets) with de-projected velocities up to 231 km/s seen at phases when the luminous primary is behind the jet-launching companion. The outflow is likely ejected due to accretion onto a main sequence companion of 0.63 ± 0.13 solar masses. Our results indicate that although PPNe are intrinsically rare objects, binarity might not be as rare in these systems and that their binary nature can be constrained using long term RV monitoring on larger telescopes.

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