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Register a new userDay-side z-band emission and eccentricity of Wasp-12b
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Added by
Mercedes Lopez-Morales
Publication date
2009
fields
Physics
and research's language is
English
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We report the detection of the eclipse of the very-hot Jupiter WASP-12b via z-band time-series photometry obtained with the 3.5-meter ARC telescope at Apache Point Observatory. We measure a decrease in flux of 0.082+/-0.015% during the passage of the planet behind the star. That planetary flux is equally well reproduced by atmospheric models with and without extra absorbers, and blackbody models with f > 0.585+/-0.080. It is therefore necessary to measure the planet at other wavelengths to further constrain its atmospheric properties. The eclipse appears centered at phase = 0.5100 (+0.0072,-0.0061), consistent with an orbital eccentricity of |e cos w| = 0.016 (+0.011,-0.009) (see note at end of Section 4). If the orbit of the planet is indeed eccentric, the large radius of WASP-12b can be explained by tidal heating.
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We analyze the high-resolution emission spectrum of WASP-33b taken using the High Dispersion Spectrograph (R,$approx$,165,000) on the 8.2-m Subaru telescope. The data cover $lambda$,$approx$,$6170$-$8817$,AA, divided over 30 spectral orders. The telluric and stellar lines are removed using a de-trending algorithm, {sc SysRem}, before cross-correlating with planetary spectral templates. We calculate the templates assuming a 1-D plane-parallel hydrostatic atmosphere including continuum opacity of bound-free H$^{-}$ and Rayleigh scattering by H$_{2}$ with a range of constant abundances of Fe,{sc i}. Using a likelihood-mapping analysis, we detect an Fe,{sc i} emission signature at 6.4-$sigma$ located at $K_{mathrm{p}}$ of 226.0,$^{+2.1}_{-2.3}$,km,s$^{-1}$and $v_{mathrm{sys}}$ of -3.2,$^{+2.1}_{-1.8}$,km,s$^{-1}$ -- consistent with the planets expected velocity in the literature. We also confirm the existence of a thermal inversion in the day-side of the planet which is very likely to be caused by the presence of Fe,{sc i} and previously-detected TiO in the atmosphere. This makes WASP-33b one of the prime targets to study the relative contributions of both species to the energy budget of an ultra-hot Jupiter.
We report a new detection of the H-band thermal emission of CoRoT-1b and two confirmation detections of the Ks-band thermal emission of WASP-12b at secondary eclipses. The H-band measurement of CoRoT-1b shows an eclipse depth of 0.145%pm0.049% with a 3-{sigma} percentile between 0.033% - 0.235%. This depth is consistent with the previous conclusions that the planet has an isother- mal region with inefficient heat transport from dayside to nightside, and has a dayside thermal inversion layer at high altitude. The two Ks band detections of WASP-12b show a joint eclipse depth of 0.299%pm0.065%. This result agrees with the measurement of Croll & collaborators, providing independent confirmation of their measurement. The repeatability of the WASP-12b measurements also validates our data analysis method. Our measurements, in addition to a number of previous results made with other telescopes, demonstrate that ground-based observations are becoming widely available for characterization of atmospheres of hot Jupiters.
We report high-resolution spectroscopic detection of TiO molecular signature in the day-side spectra of WASP-33 b, the second hottest known hot Jupiter. We used High-Dispersion Spectrograph (HDS; R $sim$ 165,000) in the wavelength range of 0.62 -- 0.88 $mu$m with the Subaru telescope to obtain the day-side spectra of WASP-33 b. We suppress and correct the systematic effects of the instrument, the telluric and stellar lines by using SYSREM algorithm after the selection of good orders based on Barnard star and other M-type stars. We detect a 4.8-$sigma$ signal at an orbital velocity of $K_{p}$= +237.5 $^{+13.0}_{-5.0}$ km s$^{-1}$ and systemic velocity $V_{sys}$= -1.5 $^{+4.0} _{-10.5}$ km s$^{-1}$, which agree with the derived values from the previous analysis of primary transit. Our detection with the temperature inversion model implies the existence of stratosphere in its atmosphere, however, we were unable to constrain the volume-mixing ratio of the detected TiO. We also measure the stellar radial velocity and use it to obtain a more stringent constraint on the orbital velocity, $K_{p} = 239.0^{+2.0}_{-1.0}$ km s$^{-1}$. Our results demonstrate that high-dispersion spectroscopy is a powerful tool to characterize the atmosphere of an exoplanet, even in the optical wavelength range, and show a promising potential in using and developing similar techniques with high-dispersion spectrograph on current 10m-class and future extremely large telescopes.
WASP-12b is a transiting hot Jupiter on a 1.09-day orbit around a late-F star. Since the planets discovery in 2008, the time interval between transits has been decreasing by $29pm 2$ msec year$^{-1}$. This is a possible sign of orbital decay, although the previously available data left open the possibility that the planets orbit is slightly eccentric and is undergoing apsidal precession. Here, we present new transit and occultation observations that provide more decisive evidence for orbital decay, which is favored over apsidal precession by a $Deltamathrm{BIC}$ of 22.3 or Bayes factor of 70,000. We also present new radial-velocity data that rule out the R{o}mer effect as the cause of the period change. This makes WASP-12 the first planetary system for which we can be confident that the orbit is decaying. The decay timescale for the orbit is $P/dot{P} = 3.25pm 0.23$ Myr. Interpreting the decay as the result of tidal dissipation, the modified stellar tidal quality factor is $Q_star = 1.8 times10^{5}$.
WASP-19b is one of the most irradiated hot-Jupiters known. Its secondary eclipse is the deepest of all transiting planets, and has been measured in multiple optical and infrared bands. We obtained a z band eclipse observation, with measured depth of 0.080 +/- 0.029 %, using the 2m Faulkes Telescope South, that is consistent with the results of previous observations. We combine our measurement of the z band eclipse with previous observations to explore atmosphere models of WASP-19b that are consistent with the its broadband spectrum. We use the VSTAR radiative transfer code to examine the effect of varying pressure-temperature profiles and C/O abundance ratios on the emission spectrum of the planet. We find models with super-solar carbon enrichment best match the observations, consistent with previous model retrieval studies. We also include upper atmosphere haze as another dimension in the interpretation of exoplanet emission spectra, and find that particles <0.5 micron in size are unlikely to be present in WASP-19b.
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