Access: A featureless optical transmission spectrum for WASP-19b from Magellan/IMACS

Néstor Espinoza, Benjamin V. Rackham, Andrés Jordán, Dániel Apai, Mercedes López-Morales, David J. Osip, Simon L. Grimm, Jens Hoeijmakers, Paul A. Wilson, Alex Bixel, Chima McGruder, Florian Rodler, Ian Weaver, Nikole K. Lewis, Jonathan J. Fortney, Jonathan Fraine

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

The short-period (0.94-d) transiting exoplanet WASP-19b is an exceptional target for transmission spectroscopy studies, due to its relatively large atmospheric scale height (∼500 km) and equilibrium temperature (∼2100 K). Here, we report on six precise spectroscopic Magellan/IMACS observations, five of which target the full optical window from 0.45 to 0.9 μm and one targeting the 0.4-0.55 μm blue-optical range. Five of these data sets are consistent with a transmission spectrum without any significant spectral features, while one shows a significant slope as a function of wavelength, which we interpret as arising from photospheric heterogeneities in the star. Coupled with HST/WFC3 infrared observations, our optical/near-infrared measurements point to the presence of high altitude clouds in WASP-19b's atmosphere in agreement with previous studies. Using a semi-analytical retrieval approach, considering both planetary and stellar spectral features, we find a water abundance consistent with solar for WASP-19b and strong evidence for sub-solar abundances for optical absorbers such as TiO and Na; no strong optical slope is detected, which suggests that if hazes are present, they are much weaker than previously suggested. In addition, two spot-crossing events are observed in our data sets and analysed, including one of the first unambiguously detected bright-spot-crossing events on an exoplanet host star.

Original languageEnglish (US)
Pages (from-to)2065-2087
Number of pages23
JournalMonthly Notices of the Royal Astronomical Society
Volume482
Issue number2
DOIs
StatePublished - Jan 11 2019

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extrasolar planets
slopes
stars
haze
scale height
high altitude
targeting
retrieval
absorbers
near infrared
spectroscopy
wavelength
atmospheres
atmosphere
wavelengths
water
temperature

Keywords

  • Planets and satellites: atmospheres
  • Planets and satellites: individual: WASP-19b
  • Stars: activit
  • Stars: individual: WASP-19
  • Starspots
  • Techniques: spectroscopic

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Espinoza, N., Rackham, B. V., Jordán, A., Apai, D., López-Morales, M., Osip, D. J., ... Fraine, J. (2019). Access: A featureless optical transmission spectrum for WASP-19b from Magellan/IMACS. Monthly Notices of the Royal Astronomical Society, 482(2), 2065-2087. https://doi.org/10.1093/mnras/sty2691

Access : A featureless optical transmission spectrum for WASP-19b from Magellan/IMACS. / Espinoza, Néstor; Rackham, Benjamin V.; Jordán, Andrés; Apai, Dániel; López-Morales, Mercedes; Osip, David J.; Grimm, Simon L.; Hoeijmakers, Jens; Wilson, Paul A.; Bixel, Alex; McGruder, Chima; Rodler, Florian; Weaver, Ian; Lewis, Nikole K.; Fortney, Jonathan J.; Fraine, Jonathan.

In: Monthly Notices of the Royal Astronomical Society, Vol. 482, No. 2, 11.01.2019, p. 2065-2087.

Research output: Contribution to journalArticle

Espinoza, N, Rackham, BV, Jordán, A, Apai, D, López-Morales, M, Osip, DJ, Grimm, SL, Hoeijmakers, J, Wilson, PA, Bixel, A, McGruder, C, Rodler, F, Weaver, I, Lewis, NK, Fortney, JJ & Fraine, J 2019, 'Access: A featureless optical transmission spectrum for WASP-19b from Magellan/IMACS', Monthly Notices of the Royal Astronomical Society, vol. 482, no. 2, pp. 2065-2087. https://doi.org/10.1093/mnras/sty2691
Espinoza, Néstor ; Rackham, Benjamin V. ; Jordán, Andrés ; Apai, Dániel ; López-Morales, Mercedes ; Osip, David J. ; Grimm, Simon L. ; Hoeijmakers, Jens ; Wilson, Paul A. ; Bixel, Alex ; McGruder, Chima ; Rodler, Florian ; Weaver, Ian ; Lewis, Nikole K. ; Fortney, Jonathan J. ; Fraine, Jonathan. / Access : A featureless optical transmission spectrum for WASP-19b from Magellan/IMACS. In: Monthly Notices of the Royal Astronomical Society. 2019 ; Vol. 482, No. 2. pp. 2065-2087.
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AU - Espinoza, Néstor

AU - Rackham, Benjamin V.

AU - Jordán, Andrés

AU - Apai, Dániel

AU - López-Morales, Mercedes

AU - Osip, David J.

AU - Grimm, Simon L.

AU - Hoeijmakers, Jens

AU - Wilson, Paul A.

AU - Bixel, Alex

AU - McGruder, Chima

AU - Rodler, Florian

AU - Weaver, Ian

AU - Lewis, Nikole K.

AU - Fortney, Jonathan J.

AU - Fraine, Jonathan

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N2 - The short-period (0.94-d) transiting exoplanet WASP-19b is an exceptional target for transmission spectroscopy studies, due to its relatively large atmospheric scale height (∼500 km) and equilibrium temperature (∼2100 K). Here, we report on six precise spectroscopic Magellan/IMACS observations, five of which target the full optical window from 0.45 to 0.9 μm and one targeting the 0.4-0.55 μm blue-optical range. Five of these data sets are consistent with a transmission spectrum without any significant spectral features, while one shows a significant slope as a function of wavelength, which we interpret as arising from photospheric heterogeneities in the star. Coupled with HST/WFC3 infrared observations, our optical/near-infrared measurements point to the presence of high altitude clouds in WASP-19b's atmosphere in agreement with previous studies. Using a semi-analytical retrieval approach, considering both planetary and stellar spectral features, we find a water abundance consistent with solar for WASP-19b and strong evidence for sub-solar abundances for optical absorbers such as TiO and Na; no strong optical slope is detected, which suggests that if hazes are present, they are much weaker than previously suggested. In addition, two spot-crossing events are observed in our data sets and analysed, including one of the first unambiguously detected bright-spot-crossing events on an exoplanet host star.

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