An HST optical-to-near-IR transmission spectrum of the hot Jupiter WASP-19b: Detection of atmospheric water and likely absence of TiO

C. M. Huitson, D. K. Sing, F. Pont, J. J. Fortney, A. S. Burrows, P. A. Wilson, G. E. Ballester, N. Nikolov, N. P. Gibson, D. Deming, S. Aigrain, T. M. Evans, G. W. Henry, A. Lecavelier des Etangs, Adam Showman, A. Vidal-Madjar, K. Zahnle

Research output: Contribution to journalArticle

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Abstract

We measure the transmission spectrum ofWASP-19b from three transits using low-resolution optical spectroscopy from the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS). The STIS spectra cover a wavelength range of 0.29-1.03 μm, with resolving power R = 500. The optical data are combined with archival near-infrared data from the HST Wide Field Camera 3 (WFC3) G141 grism, covering the wavelength range from 1.087 to 1.687 μm, with resolving power R = 130. We reach signal-to-noise levels between 3000 and 11 000 in 0.1 μm bins when measuring the transmission spectra from 0.53-1.687 μm. WASP-19 is known to be a very active star, with the optical stellar flux varying by a few per cent over time. We correct the transit light curves for the effects of stellar activity using ground-based activity monitoring with the Cerro Tololo Inter-American Observatory. While we were not able to construct a transmission spectrum using the blue optical data because of the presence of large occulted starspots, we were able to use the spot crossings to help constrain the mean stellar spot temperature. To search for predicted features in the hot-Jupiter atmosphere, in addition to the transmission spectrum we also define spectral indices for differential radius (δRP/R*) measurements to specifically search for the presence of TiO and alkali line features. Our measurements rule out TiO features predicted for a planet of WASP-19b's equilibrium temperature (2050 K) in the transmission spectrum at the 2.7-2.9σ confidence level, depending on atmospheric model formalism. The WFC3 transmission spectrum shows strong absorption features due to the presence of H2O, which is detected at the 4σ confidence level between 1.1 and 1.4 μm. The transmission spectra results indicate that WASP-19b is a planet with no or low levels of TiO and without a high C/O ratio. The lack of observable TiO features are possibly due to rainout, breakdown from stellar activity or the presence of other absorbers in the optical.

Original languageEnglish (US)
Pages (from-to)3252-3274
Number of pages23
JournalMonthly Notices of the Royal Astronomical Society
Volume434
Issue number4
DOIs
StatePublished - Oct 2013

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Jupiter (planet)
Hubble Space Telescope
Jupiter
water
stellar activity
transit
spectrographs
planets
confidence
planet
cameras
Jupiter atmosphere
telescopes
starspots
wavelength
atmospheric models
detection
wavelengths
light curve
alkalies

Keywords

  • Planetary systems
  • Planets and satellites: atmospheres
  • Planets and satellites: individual: WASP-19b
  • Stars: individual: WASP-19
  • Techniques: spectroscopic

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

An HST optical-to-near-IR transmission spectrum of the hot Jupiter WASP-19b : Detection of atmospheric water and likely absence of TiO. / Huitson, C. M.; Sing, D. K.; Pont, F.; Fortney, J. J.; Burrows, A. S.; Wilson, P. A.; Ballester, G. E.; Nikolov, N.; Gibson, N. P.; Deming, D.; Aigrain, S.; Evans, T. M.; Henry, G. W.; des Etangs, A. Lecavelier; Showman, Adam; Vidal-Madjar, A.; Zahnle, K.

In: Monthly Notices of the Royal Astronomical Society, Vol. 434, No. 4, 10.2013, p. 3252-3274.

Research output: Contribution to journalArticle

Huitson, CM, Sing, DK, Pont, F, Fortney, JJ, Burrows, AS, Wilson, PA, Ballester, GE, Nikolov, N, Gibson, NP, Deming, D, Aigrain, S, Evans, TM, Henry, GW, des Etangs, AL, Showman, A, Vidal-Madjar, A & Zahnle, K 2013, 'An HST optical-to-near-IR transmission spectrum of the hot Jupiter WASP-19b: Detection of atmospheric water and likely absence of TiO', Monthly Notices of the Royal Astronomical Society, vol. 434, no. 4, pp. 3252-3274. https://doi.org/10.1093/mnras/stt1243
Huitson, C. M. ; Sing, D. K. ; Pont, F. ; Fortney, J. J. ; Burrows, A. S. ; Wilson, P. A. ; Ballester, G. E. ; Nikolov, N. ; Gibson, N. P. ; Deming, D. ; Aigrain, S. ; Evans, T. M. ; Henry, G. W. ; des Etangs, A. Lecavelier ; Showman, Adam ; Vidal-Madjar, A. ; Zahnle, K. / An HST optical-to-near-IR transmission spectrum of the hot Jupiter WASP-19b : Detection of atmospheric water and likely absence of TiO. In: Monthly Notices of the Royal Astronomical Society. 2013 ; Vol. 434, No. 4. pp. 3252-3274.
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T2 - Detection of atmospheric water and likely absence of TiO

AU - Huitson, C. M.

AU - Sing, D. K.

AU - Pont, F.

AU - Fortney, J. J.

AU - Burrows, A. S.

AU - Wilson, P. A.

AU - Ballester, G. E.

AU - Nikolov, N.

AU - Gibson, N. P.

AU - Deming, D.

AU - Aigrain, S.

AU - Evans, T. M.

AU - Henry, G. W.

AU - des Etangs, A. Lecavelier

AU - Showman, Adam

AU - Vidal-Madjar, A.

AU - Zahnle, K.

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N2 - We measure the transmission spectrum ofWASP-19b from three transits using low-resolution optical spectroscopy from the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS). The STIS spectra cover a wavelength range of 0.29-1.03 μm, with resolving power R = 500. The optical data are combined with archival near-infrared data from the HST Wide Field Camera 3 (WFC3) G141 grism, covering the wavelength range from 1.087 to 1.687 μm, with resolving power R = 130. We reach signal-to-noise levels between 3000 and 11 000 in 0.1 μm bins when measuring the transmission spectra from 0.53-1.687 μm. WASP-19 is known to be a very active star, with the optical stellar flux varying by a few per cent over time. We correct the transit light curves for the effects of stellar activity using ground-based activity monitoring with the Cerro Tololo Inter-American Observatory. While we were not able to construct a transmission spectrum using the blue optical data because of the presence of large occulted starspots, we were able to use the spot crossings to help constrain the mean stellar spot temperature. To search for predicted features in the hot-Jupiter atmosphere, in addition to the transmission spectrum we also define spectral indices for differential radius (δRP/R*) measurements to specifically search for the presence of TiO and alkali line features. Our measurements rule out TiO features predicted for a planet of WASP-19b's equilibrium temperature (2050 K) in the transmission spectrum at the 2.7-2.9σ confidence level, depending on atmospheric model formalism. The WFC3 transmission spectrum shows strong absorption features due to the presence of H2O, which is detected at the 4σ confidence level between 1.1 and 1.4 μm. The transmission spectra results indicate that WASP-19b is a planet with no or low levels of TiO and without a high C/O ratio. The lack of observable TiO features are possibly due to rainout, breakdown from stellar activity or the presence of other absorbers in the optical.

AB - We measure the transmission spectrum ofWASP-19b from three transits using low-resolution optical spectroscopy from the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS). The STIS spectra cover a wavelength range of 0.29-1.03 μm, with resolving power R = 500. The optical data are combined with archival near-infrared data from the HST Wide Field Camera 3 (WFC3) G141 grism, covering the wavelength range from 1.087 to 1.687 μm, with resolving power R = 130. We reach signal-to-noise levels between 3000 and 11 000 in 0.1 μm bins when measuring the transmission spectra from 0.53-1.687 μm. WASP-19 is known to be a very active star, with the optical stellar flux varying by a few per cent over time. We correct the transit light curves for the effects of stellar activity using ground-based activity monitoring with the Cerro Tololo Inter-American Observatory. While we were not able to construct a transmission spectrum using the blue optical data because of the presence of large occulted starspots, we were able to use the spot crossings to help constrain the mean stellar spot temperature. To search for predicted features in the hot-Jupiter atmosphere, in addition to the transmission spectrum we also define spectral indices for differential radius (δRP/R*) measurements to specifically search for the presence of TiO and alkali line features. Our measurements rule out TiO features predicted for a planet of WASP-19b's equilibrium temperature (2050 K) in the transmission spectrum at the 2.7-2.9σ confidence level, depending on atmospheric model formalism. The WFC3 transmission spectrum shows strong absorption features due to the presence of H2O, which is detected at the 4σ confidence level between 1.1 and 1.4 μm. The transmission spectra results indicate that WASP-19b is a planet with no or low levels of TiO and without a high C/O ratio. The lack of observable TiO features are possibly due to rainout, breakdown from stellar activity or the presence of other absorbers in the optical.

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