Two planets orbiting the post-common envelope binary NN Serpentis Evidence for planets orbiting the post-common envelope binary NN Serpentis Stefan Dreizler Institut für Astrophysik Göttingen Based on Two planets orbiting the recently formed post-common envelope binary NN Serpentis A&A submitted K. Beuermann 1, F. V. Hessman 1, S. Dreizler 1, T. R. Marsh 2, S.G. Parsons 2, D.E. Winget 3, G. F. Miller 3, M. R. Schreiber 4, W. Kley 5, V. S. Dhillon 6, S. P. Littlefair 6, C.M. Copperwheat 2, J. J. Hermes 3 1) Göttingen, 2) Warwick, 3) Austin, 4) Valparaiso, 5) Tübingen, 6) Sheffield

Two planets orbiting the post-common envelope binary NN Serpentis Exoplanets ≤ 500 exoplantes Various methods Growing number of planets around evolved stars ≈ 10% in binaries Recently: circum- binary planets

Two planets orbiting the post-common envelope binary NN Serpentis A school project …

Two planets orbiting the post-common envelope binary NN Serpentis NN Serpentis PG (Wilson et al. 1986) P orb = 3.12 hr (Haefner et al. 1989; MCCP) VLT imaging, spectroscopy (Haefner et al. 2004) Haefner et al. 1989

Two planets orbiting the post-common envelope binary NN Serpentis Orbital Parameters Parsons et al. 2010a a = R  T WD = 57,000 K M WD = M  D = 512 pc M sec = M  Age of WD ~ 10 6 yr i = 89.6°

Two planets orbiting the post-common envelope binary NN Serpentis Eclipse Timing Residuals Qian et al MCCP VLT Lijiang U ltra C am Bialkow P = 7.6 years, a < 3.3 A.U., M = 11 M Jupiter

Two planets orbiting the post-common envelope binary NN Serpentis Eclipse Timing Residuals Parsons et al. 2010b Planetary solution rejected No satisfactory fit with linear ephemeris VLT point suspicious MCCP VLT U ltra C am Bialkow Lijiang

Two planets orbiting the post-common envelope binary NN Serpentis Revisiting the VLT Observations Trailed FORS images (Haefner et al. 2004) secs (±0.2 secs !)

Two planets orbiting the post-common envelope binary NN Serpentis MONET/North Observations

Two planets orbiting the post-common envelope binary NN Serpentis Timing Residuals MCCP VLT Lijiang U ltra C am MONET Bialkow

Two planets orbiting the post-common envelope binary NN Serpentis What the timing variations are not Not due to complicated eclipse profile Not due to stellar activity Not due to Applegate’s mechanism –Spin-orbit coupling due to magnetic cycles and radius changes within the secondary –Time scale on decades or longer –Needs too much energy (Chen 2009) Not due to apsidal motion –Precession of periastron due to tides –Amplitude  t = P bin e bin = 3577 s e bin OK with e bin ~0.01 –Variation of the FWHM not seen –Period would be ~0.4 years

Two planets orbiting the post-common envelope binary NN Serpentis McDonald Observations

Two planets orbiting the post-common envelope binary NN Serpentis UltraCam Observations

Two planets orbiting the post-common envelope binary NN Serpentis Model #1 : 3rd Body P = 22.6 years, e > 0.65 a = 6.9 A.U., M = 8.4 M Jupiter

Two planets orbiting the post-common envelope binary NN Serpentis Model #2 : 2 Bodies

Two planets orbiting the post-common envelope binary NN Serpentis The 2+2-Body Solutions Binary –Pdot < (GR angular momentum loss OK) Two stable 2+2 solutions (grid search) –P b :P c ≈ 2:1 ≈ 5:2 (±15%) –Reduced  NN Ser b –e b  0  0 –P b [years]15.50± ±0.26 –a b [A.U.]5.38± ±0.06 –M b sin i [M Jupiter ]6.89± ±0.40 NN Ser c –e c 0.20± ±0.02 –P c [years] 7.75± ±0.40 –a c [A.U.] 3.39± ±0.13 –M c sin i [M Jupiter ] 2.24± ±0.27

Two planets orbiting the post-common envelope binary NN Serpentis 0.7 A.U.0.9 A.U. Orbital Histories of NN Ser A,B Red Giant Envelope Common Envelope Ejection

Two planets orbiting the post-common envelope binary NN Serpentis Orbital History of NN Ser b,c Binary Star System –~2.1 M sun A star + M dwarf at ~1 A.U. (  CE =0.25) –RGB expansion causes CE ejection ~1 million years ago –Planets around NN Ser A absorbed 1st Generation (circumbinary): –NN Ser b,c at > ~3 A.U. –Drift outwards/near escape due to loss of 1.5 M  from NN Ser A –Differential drift inwards due to frictional drag (gravitational), tidal forces –Dynamical evolution stops at radii ~3 & 5-6 A.U. with resonance condition between b & c

Two planets orbiting the post-common envelope binary NN Serpentis A Primitive Evolution Simulation

Two planets orbiting the post-common envelope binary NN Serpentis Orbital History of NN Ser b,c 2nd Generation (circumbinary) : –Original planets at a < ~1 A.U. lost in RGB –Formation of planets in the metal rich and massive CE with 1.5 M  –NN Ser b,c come into resonance as very young planets Mixed : –Original planets at a < ~1 A.U. lost in RGB –Less massive planets at a ~ 2-6 A.U. survive CE and accretes from CE –1 st genaration plate might trigger planet formation in CE –NN Ser b,c come into resonance as rejuvinated/young planets

Two planets orbiting the post-common envelope binary NN Serpentis Conclusions The task of observing the variations and constraining the origin of the timing variations is very difficult It helps to have lots of access to 1m and occational access to 2-3m telescopes The eclipse time variations in NN Ser A/B are most simply explained as the timing effect due to two massive, circumbinary planets The planets could either be 1st or 2nd generation (or both), depending upon the details of their interaction with the CE and the CE’s long-term evolution Potentially many more circum-binary, post-common envelope planets to come

Two planets orbiting the post-common envelope binary NN Serpentis Common Envelope