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arXiv · 1310.1391

The planets around NN Ser: still there

T. R. Marsh·S. G. Parsons·M. C. P. Bours·S. P. Littlefair·C. M. Copperwheat·V. S. Dhillon·E. Breedt·C. Caceres·M. R. Schreiber
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Abstract

We present 25 new eclipse times of the white dwarf binary NN Ser taken with the high-speed camera ULTRACAM on the WHT and NTT, the RISE camera on the Liverpool Telescope, and HAWK-I on the VLT to test the two-planet model proposed to explain variations in its eclipse times measured over the last 25 years. The planetary model survives the test with flying colours, correctly predicting a progressive lag in eclipse times of 36 seconds that has set in since 2010 compared to the previous 8 years of precise times. Allowing both orbits to be eccentric, we find orbital periods of 7.9 +/- 0.5 yr and 15.3 +/- 0.3 yr, and masses of 2.3 +/- 0.5 Mjup and 7.3 +/- 0.3 Mjup. We also find dynamically long-lived orbits consistent with the data, associated with 2:1 and 5:2 period ratios. The data scatter by 0.07 seconds relative to the best-fit model, by some margin the most precise of any of the proposed eclipsing compact object planet hosts. Despite the high precision, degeneracy in the orbit fits prevents a significant measurement of a period change of the binary and of N-body effects. Finally, we point out a major flaw with a previous dynamical stability analysis of NN Ser, and by extension, with a number of analyses of similar systems.

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T. R. Marsh, S. G. Parsons, M. C. P. Bours, S. P. Littlefair, C. M. Copperwheat, V. S. Dhillon, E. Breedt, C. Caceres, M. R. Schreiber. 2013-10-04. The planets around NN Ser: still there. https://doi.org/10.1093/mnras%2Fstt1903

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