J/ApJ/733/127 Four transits of WASP-4b (Sanchis-Ojeda+, 2011)
Starspots and spin-orbit alignment in the WASP-4 exoplanetary system.
Sanchis-Ojeda R., Winn J.N., Holman M.J., Carter J.A., Osip D.J.,
Fuentes C.I.
<Astrophys. J., 733, 127 (2011)>
=2011ApJ...733..127S 2011ApJ...733..127S
ADC_Keywords: Photometry ; Planets ; Stars, double and multiple
Keywords: planetary systems - stars: rotation -
stars: individual (WASP-4=USNO-B1.0 0479-0948995)
Abstract:
We present photometry of four transits of the exoplanet WASP-4b, each
with a precision of approximately 500ppm and a time sampling of
40-60s. We have used the data to refine the estimates of the system
parameters and ephemerides. During two of the transits we observed a
short-lived, low-amplitude anomaly that we interpret as the
occultation of a starspot by the planet. We also found evidence for a
pair of similar anomalies in previously published photometry. The
recurrence of these anomalies suggests that the stellar rotation axis
is nearly aligned with the orbital axis, or else the starspot would
not have remained on the transit chord. By analyzing the timings of
the anomalies we find the sky-projected stellar obliquity to be
λ=-1+14-12degrees. This result is consistent with (and more
constraining than) a recent observation of the Rossiter-McLaughlin
effect. It suggests that the planet migration mechanism preserved the
initially low obliquity, or else that tidal evolution has realigned
the system. Future applications of this method using data from the
CoRoT and Kepler missions will allow spin-orbit alignment to be probed
for many other exoplanets.
Description:
We observed the transits of UT 2009 August 2, 6, and 10, and also 2009
September 26, with the Magellan (Baade) 6.5m telescope at Las Campanas
Observatory in Chile.
Objects:
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RA (2000) DE Designation(s) (Period)
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23 34 15.06 -42 03 41.1 WASP-4 = 2MASS J23341508-4203411 (P=1.338231)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 36 2121 Photometry of WASP-4
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See also:
J/MNRAS/422/2024 : X-ray-age relation & exoplanet evaporation (Jackson+, 2012)
J/A+A/539/A159 : WASP-4b transit griz light curves (Nikolov+, 2012)
J/A+A/530/A5 : WASP-4b Ks detection of thermal emission (Caceres+, 2011)
J/MNRAS/414/1278 : Eccentricities of transiting planets (Pont+, 2011)
J/MNRAS/411/L46 : Exoplanet magnetic fields (Vidotto+, 2011)
J/A+A/524/A25 : Radial Velocities on 6 exoplanet host stars (Triaud+, 2010)
J/ApJ/716/1336 : Stability analysis of single-planet (Kopparapu+, 2010)
J/MNRAS/399/287 : Transiting planetary system WASP-4 (Southworth+, 2009)
J/AJ/137/3826 : Two transits of the giant planet WASP-4b (Winn+, 2009)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 14 F14.6 d BJD Barycentric Julian Date (1)
16- 22 F7.5 --- RFlux Relative flux
24- 30 F7.5 --- e_RFlux Uncertainty in RFlux
32- 36 F5.3 --- Air Airmass
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Note (1): The time-stamp represents the Barycentric Julian Date at
midexposure, calculated based on the Julian Date with the code
of Eastman et al. (2010PASP..122..935E 2010PASP..122..935E).
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 16-Nov-2012