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Transits and starspots in the WASP-6 planetary system

Tregloan-Reed, Jeremy; Southworth, John; Burgdorf, M.; Calchi Novati, S.; Dominik, M.; Finet, F.; Jørgensen, U.G.; Maier, G.; Mancini, L.; Prof, S.; Ricci, D.; Snodgrass, C.; Bozza, V.; Browne, P.; Dodds, P.; Gerner, T.; Harpsøe, K.; Hinse, T.C.; Hundertmark, M.; Kains, N.; Kerins, E.; Liebig, C.; Penny, M.T.; Rahvar, S.; Sahu, K.; Scarpetta, G.; Schäfer, S.; Schönebeck, F.; Skottfelt, J.; Surdej, J.

Transits and starspots in the WASP-6 planetary system Thumbnail


Jeremy Tregloan-Reed

M. Burgdorf

S. Calchi Novati

M. Dominik

F. Finet

U.G. Jørgensen

G. Maier

L. Mancini

S. Prof

D. Ricci

C. Snodgrass

V. Bozza

P. Browne

P. Dodds

T. Gerner

K. Harpsøe

T.C. Hinse

M. Hundertmark

N. Kains

E. Kerins

C. Liebig

M.T. Penny

S. Rahvar

K. Sahu

G. Scarpetta

S. Schäfer

F. Schönebeck

J. Skottfelt

J. Surdej


We present updates to PRISM, a photometric transit-starspot model, and GEMC, a hybrid optimization code combining MCMC and a genetic algorithm. We then present high-precision photometry of four transits in the WASP-6 planetary system, two of which contain a starspot anomaly. All four transits were modelled using PRISM and GEMC, and the physical properties of the system calculated. We find the mass and radius of the host star to be 0.836 ± 0.063 M⊙ and 0.864 ± 0.024 R⊙, respectively. For the planet, we find a mass of 0.485 ± 0.027 MJup, a radius of 1.230 ± 0.035 RJup and a density of 0.244 ± 0.014 ρJup. These values are consistent with those found in the literature. In the likely hypothesis that the two spot anomalies are caused by the same starspot or starspot complex, we measure the stars rotation period and velocity to be 23.80 ± 0.15 d and 1.78 ± 0.20 km s−1, respectively, at a colatitude of 75.8°. We find that the sky-projected angle between the stellar spin axis and the planetary orbital axis is λ = 7.2° ± 3.7°, indicating axial alignment. Our results are consistent with and more precise than published spectroscopic measurements of the Rossiter–McLaughlin effect. These results suggest that WASP-6 b formed at a much greater distance from its host star and suffered orbital decay through tidal interactions with the protoplanetary disc.

Journal Article Type Article
Acceptance Date Mar 30, 2015
Online Publication Date Apr 28, 2015
Publication Date Jun 21, 2015
Publicly Available Date May 26, 2023
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 450
Issue 2
Pages 1760 -1769
Keywords stars, fundamental parameters, individual, WASP-19, planetary systems, starspots
Publisher URL