Measurement of the Spin-Orbit Angle of Exoplanet HAT-P-1b

The Astrophysical Journal (Impact Factor: 6.28). 12/2008; 686(1):649. DOI: 10.1086/591078
Source: arXiv

ABSTRACT We present new spectroscopic and photometric observations of the HAT-P-1 planetary system. Spectra obtained during three transits exhibit the Rossiter-McLaughlin effect, allowing us to measure the angle between the sky projections of the stellar spin axis and orbit normal, λ = 3.7°± 2.1°. The small value of λ for this and other systems suggests that the dominant planet migration mechanism preserves spin-orbit alignment. Using two new transit light curves, we refine the transit ephemeris and reduce the uncertainty in the orbital period by an order of magnitude. We find a upper limit on the orbital eccentricity of 0.067, with 99% confidence, by combining our new radial velocity measurements with those obtained previously.

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    The Astrophysical Journal 02/2014; 786(2). DOI:10.1088/0004-637X/786/2/102 · 6.28 Impact Factor
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    ABSTRACT: Using a sample of 68 planet-hosting stars I carry out a comparison of isochrone fitting and gyrochronology to investigate whether tidal interactions between the stars and their planets are leading to underestimated ages using the latter method. I find a slight tendency for isochrones to produce older age estimates but find no correlation with tidal time-scale, although for some individual systems the effect of tides might be leading to more rapid rotation than expected from the stars' isochronal age, and therefore an underestimated gyrochronology age. By comparing to planetary systems in stellar clusters, I also find that in some cases isochrone fitting can overestimate the age of the star. The evidence for any bias on a sample-wide level is inconclusive. I also consider the subset of my sample for which the sky-projected alignment angle between the stellar rotation axis and the planet's orbital axis has been measured, finding similar patterns to those identified in the full sample. However, small sample sizes for both the misaligned and aligned systems prevent strong conclusions from being drawn.
    Monthly Notices of the Royal Astronomical Society 06/2014; 442(2). DOI:10.1093/mnras/stu950 · 5.23 Impact Factor
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    ABSTRACT: We present Hubble Space Telescope near-infrared transmission spectroscopy of the transiting hot-Jupiter HAT-P-1b. We observed one transit with Wide Field Camera 3 using the G141 low-resolution grism to cover the wavelength range 1.087-1.678 μm. These time series observations were taken with the newly available spatial-scan mode that increases the duty cycle by nearly a factor of 2, thus improving the resulting photometric precision of the data. We measure a planet-to-star radius ratio of Rp/R* = 0.117 09 ± 0.000 38 in the white light curve with the centre of transit occurring at 245 6114.345 ± 0.000 133 (JD). We achieve S/N levels per exposure of 1840 (0.061 per cent) at a resolution of Δλ = 19.2 nm (R ˜ 70) in the 1.1173-1.6549 μm spectral region, providing the precision necessary to probe the transmission spectrum of the planet at close to the resolution limit of the instrument. We compute the transmission spectrum using both single target and differential photometry with similar results. The resultant transmission spectrum shows a significant absorption above the 5σ level matching the 1.4 μm water absorption band. In solar composition models, the water absorption is sensitive to the ˜1 m bar pressure levels at the terminator. The detected absorption agrees with that predicted by a 1000 K isothermal model, as well as with that predicted by a planetary-averaged temperature model.
    Monthly Notices of the Royal Astronomical Society 11/2013; 435(4):3481-3493. DOI:10.1093/mnras/stt1536 · 5.23 Impact Factor


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