High-precision photometry by telescope defocusing - IV. Confirmation of the huge radius of WASP-17b

John Southworth, T. C. Hinse, M. Dominik, X. S. Fang, K. Harpsøe, U. G. Jørgensen, E. Kerins, C. Liebig, L. Mancini, J. Skottfelt, D. R. Anderson, B. Smalley, J. Tregloan-Reed, O. Wertz, Khalid Al-Subai, V. Bozza, S. Calchi Novati, S. Dreizler, S. H. Gu, M. HundertmarkJ. Jessen-Hansen, N. Kains, H. Kjeldsen, M. N. Lund, M. Lundkvist, M. Mathiasen, M. T. Penny, S. Rahvar, D. Ricci, G. Scarpetta, C. Snodgrass, J. Surdej

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

We present photometric observations of four transits in the WASP-17 planetary system, obtained using telescope defocusing techniques and with scatters reaching 0.5mmag per point. Our revised orbital period is 4.0 ± 0.6s 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, R b = 1.932 ± 0.052 ± 0.010R Jup (statistical and systematic errors, respectively), provides confirmation that WASP-17b is the largest planet currently known. All 14 planets with radii measured to be greater than 1.6R Jup are found around comparatively hot (T eff > 5900K) and massive (M A > 1.15M ) 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.

Original languageEnglish
Pages (from-to)1338-1348
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Volume426
Issue number2
DOIs
Publication statusPublished - 21 Oct 2012

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defocusing
photometry
planets
planet
telescopes
radii
transit
eccentricity
stars
orbitals
stellar models
planetary systems
systematic errors
light curve
physical property
physical properties
prediction
predictions

Keywords

  • Planetary systems
  • Stars: fundamental parameters
  • Stars: individual: WASP-17

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Southworth, J., Hinse, T. C., Dominik, M., Fang, X. S., Harpsøe, K., Jørgensen, U. G., ... Surdej, J. (2012). High-precision photometry by telescope defocusing - IV. Confirmation of the huge radius of WASP-17b. Monthly Notices of the Royal Astronomical Society, 426(2), 1338-1348. https://doi.org/10.1111/j.1365-2966.2012.21781.x

High-precision photometry by telescope defocusing - IV. Confirmation of the huge radius of WASP-17b. / Southworth, John; 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.; Al-Subai, Khalid; 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.; Surdej, J.

In: Monthly Notices of the Royal Astronomical Society, Vol. 426, No. 2, 21.10.2012, p. 1338-1348.

Research output: Contribution to journalArticle

Southworth, J, Hinse, TC, Dominik, M, Fang, XS, Harpsøe, K, Jørgensen, UG, Kerins, E, Liebig, C, Mancini, L, Skottfelt, J, Anderson, DR, Smalley, B, Tregloan-Reed, J, Wertz, O, Al-Subai, K, Bozza, V, Calchi Novati, S, Dreizler, S, Gu, SH, Hundertmark, M, Jessen-Hansen, J, Kains, N, Kjeldsen, H, Lund, MN, Lundkvist, M, Mathiasen, M, Penny, MT, Rahvar, S, Ricci, D, Scarpetta, G, Snodgrass, C & Surdej, J 2012, 'High-precision photometry by telescope defocusing - IV. Confirmation of the huge radius of WASP-17b', Monthly Notices of the Royal Astronomical Society, vol. 426, no. 2, pp. 1338-1348. https://doi.org/10.1111/j.1365-2966.2012.21781.x
Southworth, John ; 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. ; Al-Subai, Khalid ; 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. ; Surdej, J. / High-precision photometry by telescope defocusing - IV. Confirmation of the huge radius of WASP-17b. In: Monthly Notices of the Royal Astronomical Society. 2012 ; Vol. 426, No. 2. pp. 1338-1348.
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abstract = "We present photometric observations of four transits in the WASP-17 planetary system, obtained using telescope defocusing techniques and with scatters reaching 0.5mmag per point. Our revised orbital period is 4.0 ± 0.6s 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, R b = 1.932 ± 0.052 ± 0.010R Jup (statistical and systematic errors, respectively), provides confirmation that WASP-17b is the largest planet currently known. All 14 planets with radii measured to be greater than 1.6R Jup are found around comparatively hot (T eff > 5900K) and massive (M A > 1.15M ⊙) 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.",
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T1 - High-precision photometry by telescope defocusing - IV. Confirmation of the huge radius of WASP-17b

AU - Southworth, John

AU - Hinse, T. C.

AU - Dominik, M.

AU - Fang, X. S.

AU - Harpsøe, K.

AU - Jørgensen, U. G.

AU - Kerins, E.

AU - Liebig, C.

AU - Mancini, L.

AU - Skottfelt, J.

AU - Anderson, D. R.

AU - Smalley, B.

AU - Tregloan-Reed, J.

AU - Wertz, O.

AU - Al-Subai, Khalid

AU - Bozza, V.

AU - Calchi Novati, S.

AU - Dreizler, S.

AU - Gu, S. H.

AU - Hundertmark, M.

AU - Jessen-Hansen, J.

AU - Kains, N.

AU - Kjeldsen, H.

AU - Lund, M. N.

AU - Lundkvist, M.

AU - Mathiasen, M.

AU - Penny, M. T.

AU - Rahvar, S.

AU - Ricci, D.

AU - Scarpetta, G.

AU - Snodgrass, C.

AU - Surdej, J.

PY - 2012/10/21

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