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Into the UV: A Precise Transmission Spectrum of HAT-P-41b Using Hubble’s WFC3/UVIS G280 Grism

Wakeford, H. R. and Sing, D. K. and Stevenson, K. B. and Lewis, N. K. and Pirzkal, N. and Wilson, T. J. and Goyal, J. and Kataria, T. and Mikal-Evans, T. and Nikolov, N. and Spake, J. (2020) Into the UV: A Precise Transmission Spectrum of HAT-P-41b Using Hubble’s WFC3/UVIS G280 Grism. Astronomical Journal, 159 (5). Art. No. 204. ISSN 1538-3881.

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The ultraviolet–visible wavelength range holds critical spectral diagnostics for the chemistry and physics at work in planetary atmospheres. To date, time-series studies of exoplanets to characterize their atmospheres have relied on several combinations of modes on the Hubble Space Telescope's STIS/COS instruments to access this wavelength regime. Here for the first time, we apply the Hubble WFC3/UVIS G280 grism mode to obtain exoplanet spectroscopy from 200 to 800 nm in a single observation. We test the G280 grism mode on the hot Jupiter HAT-P-41b over two consecutive transits to determine its viability for the characterization of exoplanet atmospheres. We obtain a broadband transit depth precision of 29–33 ppm and a precision of on average 200 ppm in 10 nm spectroscopic bins. Spectral information from the G280 grism can be extracted from both the positive and negative first-order spectra, resulting in a 60% increase in the measurable flux. Additionally, the first Hubble Space Telescope orbit can be fully utilized in the time-series analysis. We present detailed extraction and reduction methods for use by future investigations with this mode, testing multiple techniques. We find the results to be fully consistent with STIS measurements of HAT-P-41b from 310 to 800 nm, with the G280 results representing a more observationally efficient and precise spectrum. HAT-P-41b's transmission spectrum is best fit with a model with T eq = 2091 K, high metallicity, and significant scattering and cloud opacity. With these first-of-their-kind observations, we demonstrate that WFC3/UVIS G280 is a powerful new tool to obtain UV–optical spectra of exoplanet atmospheres, adding to the UV legacy of Hubble and complementing future observations with the James Webb Space Telescope.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Wakeford, H. R.0000-0003-4328-3867
Sing, D. K.0000-0001-6050-7645
Stevenson, K. B.0000-0002-7352-7941
Lewis, N. K.0000-0002-8507-1304
Pirzkal, N.0000-0003-3382-5941
Wilson, T. J.0000-0001-6352-9735
Goyal, J.0000-0002-8515-7204
Kataria, T.0000-0003-3759-9080
Mikal-Evans, T.0000-0001-5442-1300
Nikolov, N.0000-0002-6500-3574
Additional Information:© 2020 The American Astronomical Society. Received 2020 January 22; revised 2020 February 27; accepted 2020 February 29; published 2020 April 13. We thank D. Deming for use of data from his Spitzer program 13044 that provided the two transits used to obtain accurate system parameters. Thanks to S. Morrell for discussions on the stellar parameters with updates from Gaia. We acknowledge private communication from N. Nikolov and K. Sheppard for the STIS data analysis from the Hubble PanCET program (K. Sheppard 2020, in preparation, private communication). This work is based on observations made with the NASA/ESA Hubble Space Telescope, HST-GO-15288, that were obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. A portion of this work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. H.R. Wakeford acknowledges support from the Giacconi Prize Fellowship at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. Software: POET pipeline (Stevenson et al. 2012; Cubillos et al. 2013), IRAF (Tody 1986, 1993), IDL Astronomy user's library (Landsman 1995), NumPy (Oliphant 2006), SciPy (Virtanen et al. 2019), MatPlotLib (Caswell et al. 2019), AstroPy (Astropy Collaboration et al. 2018), Photutils (Bradley et al. 2019). Author Contributions: H.R. Wakeford led the UVIS data analysis with detailed comparisons provided by D.K. Sing. N. Pirzkal provided the UVIS calibration pipeline and knowledge of the instrument. K.B. Stevenson analyzed the Spitzer data and helped with discussions on the UVIS analysis. N.K. Lewis aided with the interpretation of the results and providing context for the observations. T.J. Wilson aided in the statistical analysis. All authors provided text and comments for the manuscript.
Funding AgencyGrant Number
Space Telescope Science InstituteUNSPECIFIED
Subject Keywords:Exoplanet atmospheres ; Near ultraviolet astronomy ; Hubble Space Telescope
Issue or Number:5
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet atmospheres (487); Near ultraviolet astronomy (1094); Hubble Space Telescope (761)
Record Number:CaltechAUTHORS:20200413-120133661
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Official Citation:H. R. Wakeford et al 2020 AJ 159 204
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102505
Deposited By: Tony Diaz
Deposited On:13 Apr 2020 19:38
Last Modified:13 Apr 2020 19:38

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