Identifying close binary central stars of PN with Kepler

Abstract

Six planetary nebulae (PN) are known in the Kepler space telescope field of view, three newly identified. Of the 5 central stars of PN with useful Kepler data, one, J 193110888+4324577, is a short-period, post common envelope binary exhibiting relativistic beaming effects. A second, the central star of the newly identified PN Pa 5, has a rare O(He) spectral type and a periodic variability consistent with an evolved companion, where the orbital axis is almost aligned with the line of sight. The third PN, NGC 6826 has a fast rotating central star, something that can only be achieved in a merger. Fourth, the central star of the newly identified PN Kn 61, has a PG1159 spectral type and a mysterious semi-periodic light variability which we conjecture to be related to the interplay of binarity with a stellar wind. Finally, the central star of the circular PN A 61 does not appear to have a photometric variability above 2 mmag. With the possible exception of the variability of Kn 61, all other variability behaviour, whether due to binarity or not, would not easily have been detected from the ground. We conclude, based on very low numbers, that there may be many more close binary or close binary products to be discovered with ultra-high precision photometry. With a larger number of high precision photometric observations we will be able to determine how much higher than the currently known 15 per cent, the short period binary fraction for central stars of PN is likely to be.

KIC 4552982: OUTBURSTS AND ASTEROSEISMOLOGY FROM THE LONGEST PSEUDO-CONTINUOUS LIGHT CURVE OF A ZZ Ceti

“…De Marco et al (2015) analyze the Kepler light curve of the central star of planetary nebula Kn 61, which exhibits brightening events every 2-12 days, each lasting 1-2 days with amplitudes of 8%-14%. These events are similar to the outbursts on KIC 4552982, at least in that they are also unlike previously studied behavior.…”

HubbleSpace Telescope ultraviolet spectroscopy of the hottest known helium-rich pre-white dwarf KPD 0005+5106

“…The element abundances are summarized in Table 4 and displayed in Fig. 7, together with results for RCB and EHe stars (from Jeffery et al 2011, and references Currently, ten objects were assigned to the group of O(He) stars (Reindl et al 2014;Werner et al 2014;De Marco et al 2015). They cover a parameter range of T eff = 80 000−195 000 K and log g = 5.0−6.7.…”

Observational Confirmation of a Link Between Common Envelope Binary Interaction and Planetary Nebula Shaping

“…Many of those systems were discovered through photometric variability, and while most are likely to be real binaries, additional confirmation is necessary for some of them (e.g., Kn 61; De Marco et al 2015). Along with studies confirming the binarity of several of these systems (e.g., Shimanskii et al 2008;Hillwig et al 2015Hillwig et al , 2016, discoveries of additional close binary CSPNe are helping us to better understand the nature of these systems.…”