Royal Society University Research Fellow.
High-precision photometry by telescope defocusing – IV. Confirmation of the huge radius of WASP-17 b†
Article first published online: 1 OCT 2012
© 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS
Monthly Notices of the Royal Astronomical Society
Volume 426, Issue 2, pages 1338–1348, 21 October 2012
How to Cite
Southworth, J., Hinse, T. C., Dominik, M., Fang, X.-S., Harpsøe, K., Jørgensen, U. G., Kerins, E., Liebig, C., Mancini, L., Skottfelt, J., Anderson, D. R., Smalley, B., Tregloan-Reed, J., Wertz, O., Alsubai, K. A., Bozza, V., Calchi Novati, S., Dreizler, S., Gu, S.-H., Hundertmark, M., Jessen-Hansen, J., Kains, N., Kjeldsen, H., Lund, M. N., Lundkvist, M., Mathiasen, M., Penny, M. T., Rahvar, S., Ricci, D., Scarpetta, G., Snodgrass, C. and Surdej, J. (2012), High-precision photometry by telescope defocusing – IV. Confirmation of the huge radius of WASP-17 b. Monthly Notices of the Royal Astronomical Society, 426: 1338–1348. doi: 10.1111/j.1365-2966.2012.21781.x
Based on data collected by MiNDSTEp with the Danish 1.54-m telescope at the ESO La Silla Observatory.
- Issue published online: 24 SEP 2012
- Article first published online: 1 OCT 2012
- Manuscript Accepted: 23 JUL 2012
- Manuscript Received: 18 JUL 2012
- Danish Natural Science Research Council
- European Community's Seventh Framework. Grant Numbers: 229517, 268421
- European Research Council. Grant Number: 267864
- Danish National Research Foundation
- Qatar National Research Fund (QNRF). Grant Number: NPRP 09-476-1-078
- NSFC. Grant Number: 10873031
- Communauté française de Belgique
- stars: fundamental parameters;
- stars: individual: WASP-17;
- planetary systems
We present photometric observations of four transits in the WASP-17 planetary system, obtained using telescope defocusing techniques and with scatters reaching 0.5 mmag per point. Our revised orbital period is 4.0 ± 0.6 s longer than previous measurements, a difference of 6.6σ, and does not support the published detections of orbital eccentricity in this system. We model the light curves using the jktebop code and calculate the physical properties of the system by recourse to five sets of theoretical stellar model predictions. The resulting planetary radius, Rb = 1.932 ± 0.052 ± 0.010 RJup (statistical and systematic errors, respectively), provides confirmation that WASP-17 b is the largest planet currently known. All 14 planets with radii measured to be greater than 1.6 RJup are found around comparatively hot (Teff > 5900 K) and massive (MA > 1.15 M⊙) stars. Chromospheric activity indicators are available for eight of these stars, and all imply a low activity level. The planets have small or zero orbital eccentricities, so tidal effects struggle to explain their large radii. The observed dearth of large planets around small stars may be natural but could also be due to observational biases against deep transits, if these are mistakenly labelled as false positives and so not followed up.