Hubble Space Telescope time-series photometry of the planetary transit of HD 189733: no moon, no rings, starspots

By F. Pont, R. L. Gilliland, C. Moutou, D. Charbonneau, F. Bouchy, Timothy M. Brown, M. Mayor, D. Queloz, Nuno C. Santos, S. Udry. 2007

196 citations recorded by the source corpus.

We monitored three transits of the giant gas planet around the nearby K dwarf HD 189733 with the ACS camera on the Hubble Space Telescope. The resulting very-high accuracy lightcurve (signal-to-noise ratio near 15 000 on individual measurements, 35 000 on 10-min averages) allows a direct geometric measurement of the orbital inclination, radius ratio and scale of the system: i = 85.68 ± 0.04, Rpl/R∗ = 0.1572 ± 0.0004, a/R∗ = 8.92 ± 0.09. We derive improved values for the stellar and planetary radius, R∗ = 0.755 ± 0.011 R� ,Rpl = 1.154 ± 0.017 RJ, and the transit ephemerides, Ttr = 2453931.12048 ± 0.00002+n·2.218581 ± 0.000002. The HST data also reveal clear evidence of the planet occulting spots on the surface of the star. At least one large spot complex (>80 000 km) is required to explain the observed flux residuals and their colour evolution. This feature is compatible in amplitude and phase with the variability observed simultaneously from the ground. No evidence for satellites or rings around HD 189733b is seen in the HST lightcurve. This allows us to exlude with a high probability the presence of Earth-sized moons and Saturn-type debris rings around this planet. The timing of the three transits sampled is stable to the level of a few seconds, excluding a massive second planet in outer 2:1 resonance.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/409dccae54554357a4639ee3c26d9a9e5cc5d760

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MULTIWAVELENGTH CONSTRAINTS ON THE DAY–NIGHT CIRCULATION PATTERNS OF HD 189733b (2008, background): “Rather than using the previously published ephemeris from Winn et al. (2007a), which does not include these recent observations, we derive a new ephemeris from a fit to all 27 previously published transits (Bakos et al. 2006b; Winn et al. 2007a; Knutson et al. 2007; Pont et al. 2007).”
Homogeneous studies of transiting extrasolar planets – I. Light-curve analyses (2008, methodology): “This is attributed by Pont et al. (2007c) to systematic errors arising from the use of image subtraction by Holman et al. (2007a).”
Evaporation of the planet HD 189733b observed in H I Lyman-α (2010, background): “HD 189733b orbits a bright main-sequence star and shows a transit occultation depth of ≈2.4% at optical wavelengths (Pont et al. 2007).”
Magnetic activity in the photosphere of CoRoT-Exo-2a. Active longitudes and short-term spot cycle in (2008, methodology): “…to map the spots located on the band of the star occulted by the planet during its transits, by means of eclipse mapping techniques (e.g, Silva 2003; Pont et al. 2007), will be the subject of another investigation that will benefit from the present study to put its results in a broader context.”
SOAP 2.0: A TOOL TO ESTIMATE THE PHOTOMETRIC AND RADIAL VELOCITY VARIATIONS INDUCED BY STELLAR SPOTS AND PLAGES (2014, result): “…degrees, are compatible with previous measurements of the spin-orbit angle close to zero degree10 (Collier Cameron et al. 2010; Triaud et al. 2009; Winn et al. 2006), and HST observation of the transiting planet HD189733b occulting stellar spots at ∼ 30 degrees in latitude (Pont et al. 2007).”
Homogeneous studies of transiting extrasolar planets - III. Additional planets and stellar models (2010, background): “HD 189733 is an active star (Bouchy et al. 2005b) with starspots (Pont et al. 2007),a short rotation period of 12 d (Winn et al. 2007b), RV jitter (Boisseet al. 2009), and Ca H & K emission modulated on its rotation period (Moutou et al. 2007).”
Transit spectrophotometry of the exoplanet HD189733b. I. Searching for water but finding haze with HST NICMOS (2009, methodology): “This dataset also covers the HD189733 stellar activity during the epochs of the HST transmission spectra from Pont et al. (2007) and Swain et al. (2008) as well as the Spitzer transit photometry of Désert et al. (2009a), Désert et al. (2009b), and Knutson et al. (2009) making it an invaluable…”
THE FLAT TRANSMISSION SPECTRUM OF THE SUPER-EARTH GJ1214b FROM WIDE FIELD CAMERA 3 ON THE HUBBLE SPACE TELESCOPE (2011, background): “This effect of this orbital phase term could be equally well-achieved, for instance, by including a linear function of the 0th order x and y positions (see Burke et al. 2010; Pont et al. 2007; Swain et al. 2008).”
Temperature–pressure profile of the hot Jupiter HD 189733b from HST sodium observations: detection of upper atmospheric heating (2012, background): “Occulted spot features are therefore more severe at blue wavelengths than at red (e.g. Pont et al. 2007).”
3.6 AND 4.5 μm PHASE CURVES AND EVIDENCE FOR NON-EQUILIBRIUM CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HD 189733b (2012, methodology): “We calculate an updated ephemeris for the system using the transit times given in Table 1 and previously published values from Spitzer (Knutson et al. 2009a; Désert et al. 2009, 2011a; Agol et al. 2010) and Hubble (Pont et al. 2007).”
Hubble Space Telescope transmission spectroscopy of the exoplanet HD 189733b: high‐altitude atmospheric haze in the optical and near‐ultraviolet with STIS (2011, methodology): “…Instrument Science Report ACS 2008-03 This dataset also covers the HD189733 stellar activity during the epochs of the HST transmission spectra from Pont et al. (2007), Swain, Vasisht & Tinetti (2008) and Sing et al. (2009), and as well as the Spitzer transit photometry of Désert et al. (2009),…”
The prevalence of dust on the exoplanet HD 189733b from Hubble and Spitzer observations (2012, background): “The results were published in Pont et al. (2007) for the time series and Pont et al. (2008) for the transmission spectrum.”
THE CLIMATE OF HD 189733b FROM FOURTEEN TRANSITS AND ECLIPSES MEASURED BY SPITZER (2010, background): “Our ephemeris has a precision that is > 10 times better for the period than that reported in in Pont et al. (2007), and agrees with their reported period within ∼2.8σ: their period is longer by 0.46±0.17 sec.”
SEARCH FOR CARBON MONOXIDE IN THE ATMOSPHERE OF THE TRANSITING EXOPLANET HD 189733b (2009, background): “Several observations of transits of HD 189733b have been published recently with improved 5 ephemeris (Bakos et al. 2006b; Winn et al. 2007a; Knutson et al. 2007; Pont et al. 2007; Knutson et al. 2009).”
Stellar activity of planetary host star HD 189 733 (2008, methodology): “We fixed the orbital period and the time of periastron, well constrained by previous studies, using transit timing (Pont et al. 2007; Croll et al. 2007; Winn et al. 2007).”
ROTATION AND WINDS OF EXOPLANET HD 189733 b MEASURED WITH HIGH-DISPERSION TRANSMISSION SPECTROSCOPY (2015, background): “However, we know from past transit observations (Pont et al. 2007, 2008) that HD 189733 b usually crosses some spots during transit.”
Transiting exoplanets from the CoRoT space mission - II. CoRoT-Exo-2b: a transiting planet around an active G star (2008, methodology): “This larger dispersion inside the folded transit is due to the presence of inhomogeneti s (spots) on the star surface, as has been noted for other transiting planets around active stars (Charbonneau et al. 2007 for TrES1, Pont et al. 2007 for HD189733).”
WATER VAPOR IN THE SPECTRUM OF THE EXTRASOLAR PLANET HD 189733b. I. THE TRANSIT (2014, background): “STAR SPOTS HD189733 is an active star (Boisse et al. 2009), and transit observations exhibit ubiquitous star spot crossings (Pont et al. 2007).”
A Gaussian process framework for modelling instrumental systematics: application to transmission spectroscopy (2011, unknown): “E P] 2 8 Se p e.g. Brown et al. 2001; Gilliland & Arribas 2003; Pont et al. 2007).”