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Starspots and spin-orbit alignment in the WASP-4 exoplanetary system

Published online by Cambridge University Press:  10 November 2011

Roberto Sanchis-Ojeda ,
Joshua N. Winn ,
Matthew J. Holman ,
Joshua A. Carter ,
David J. Osip  and
Cesar I. Fuentes
Roberto Sanchis-Ojeda
Affiliation:
Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA e-mail: rsanchis@MIT.EDU
Joshua N. Winn
Affiliation:
Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA e-mail: rsanchis@MIT.EDU
Matthew J. Holman
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
Joshua A. Carter
Affiliation:
Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA e-mail: rsanchis@MIT.EDU Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
David J. Osip
Affiliation:
Las Campanas Observatory, Carnegie Observatories, Casilla 601, La Serena, Chile
Cesar I. Fuentes
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA Department of Physics and Astronomy, Northern Arizona University, PO Box 6010, Flagstaff, AZ 86011
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Abstract

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We present the photometric analysis of 4 transits of the exoplanet WASP-4b, obtained with the Baade 6.5m telescope, one of the two Magellan telescopes at Las Campanas. The light curves have a photometric precision of 0.5 mmag and a time sampling of 30s. This high precision has allowed us to detect several “spot anomalies”: temporary brightenings due to the occultation of a starspot on the transit chord. By analyzing these anomalies we find the sky-projected stellar obliquity to be λ = 1°+12°−14°. The small value suggests that the planet migration mechanism preserved the initially low obliquity, or that tidal evolution has realigned the system.

Keywords

stars: spotsplanetary systemstechniques: photometric

References

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