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Register a new userDetection of Fe,{sc i} Emission in the Day-side Spectrum of WASP-33b
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Stevanus Kristianto Nugroho
Publication date
2020
fields
Physics
and research's language is
English
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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.
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Theoretical studies predict the presence of thermal
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.
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.
With a temperature akin to an M-dwarf, WASP-33b is among the hottest Jupiters known, making it an ideal target for high-resolution optical spectroscopy. By analyzing both transmission and emission spectra, we aim to substantiate previous reports of atmospheric TiO and a thermal inversion within the planets atmosphere. We observed two transits and six arcs of the phase curve with ESPaDOns on the Canada-France-Hawaii Telescope and HIRES on the Keck telescope, which provide high spectral resolution and ample wavelength coverage. We employ the Doppler cross-correlation technique to search for the molecular signatures of TiO and H$_2$O in these spectra, using models based on the TiO line list of Plez (2012). Though we cannot exclude line-list-dependent effects, our data do not corroborate previous indications of a thermal inversion. Instead we place a $3sigma$ upper limit of $10^{-9}$ on the volume mixing ratio of TiO for the T-P profile we consider. While we are unable to constrain the volume mixing ratio of water, our strongest constraint on TiO comes from day-side emission spectra. This apparent absence of a stratosphere sits in stark contrast to previous observations of WASP-33b as well as theoretical predictions for the atmospheres of highly irradiated planets. The discrepancy could be due to variances between line lists, and we stress that detection limits are only as good as the line list employed, and are only valid for the specific T-P profile considered due to the strong degeneracy between lapse rate ($dT/dlog P$) and molecular abundance.
We report ground-based observations at 0.91 microns of the occultation of the hot Jupiter WASP-33b by its A5 host star. We measure the planet to be 0.109 +/- 0.030 per cent as bright as its host star at 0.91 microns. This corresponds to a brightness temperature, T_B = 3620 +200 -250 K, significantly higher than the zero-albedo equilibrium temperature for both isotropic re-radiation (2750 +/- 37 K) and uniform day-side only re-radiation (3271 +/- 44 K), but consistent with the zero-redistribution temperature (3515 +/- 47 K). This indicates that the heat redistribution from the day-side of WASP-33b to the night side is inefficient, and further suggest that there is immediate re-radiation, and therefore little or no redistribution, of heat within the day-side. We also detected the stellar pulsations of WASP-33, which we model as the sum of four sinusoids, with periods of between 42 and 77 minutes and amplitudes of 0.5 to 1.5 mmag.
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