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Hubble Space Telescope Near-IR Transmission Spectroscopy of the Super-Earth HD 97658b

Knutson, Heather A. and Dragomir, Diana and Kreidberg, Laura and Kempton, Eliza M.-R. and McCullough, P. R. and Fortney, Jonathan J. and Bean, Jacob L. and Gillon, Michaël and Homeier, Derek and Howard, Andrew W. (2014) Hubble Space Telescope Near-IR Transmission Spectroscopy of the Super-Earth HD 97658b. Astrophysical Journal, 794 (2). Art. No. 155. ISSN 0004-637X. doi:10.1088/0004-637X/794/2/155.

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Recent results from the Kepler mission indicate that super-Earths (planets with masses between 1–10 times that of the Earth) are the most common kind of planet around nearby Sun-like stars. These planets have no direct solar system analogue, and are currently one of the least well-understood classes of extrasolar planets. Many super-Earths have average densities that are consistent with a broad range of bulk compositions, including both water-dominated worlds and rocky planets covered by a thick hydrogen and helium atmosphere. Measurements of the transmission spectra of these planets offer the opportunity to resolve this degeneracy by directly constraining the scale heights and corresponding mean molecular weights of their atmospheres. We present Hubble Space Telescope near-infrared spectroscopy of two transits of the newly discovered transiting super-Earth HD 97658b. We use the Wide Field Camera 3's (WFC3) scanning mode to measure the wavelength-dependent transit depth in 30 individual bandpasses. Our averaged differential transmission spectrum has a median 1σ uncertainty of 23 ppm in individual bins, making this the most precise observation of an exoplanetary transmission spectrum obtained with WFC3 to date. Our data are inconsistent with a cloud-free solar metallicity atmosphere at the 10σ level. They are consistent at the 0.4σ level with a flat line model, as well as effectively flat models corresponding to a metal-rich atmosphere or a solar metallicity atmosphere with a cloud or haze layer located at pressures of 10 mbar or higher.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Knutson, Heather A.0000-0002-0822-3095
Dragomir, Diana0000-0003-2313-467X
Kreidberg, Laura0000-0003-0514-1147
Kempton, Eliza M.-R.0000-0002-1337-9051
McCullough, P. R.0000-0001-9165-9799
Fortney, Jonathan J.0000-0002-9843-4354
Bean, Jacob L.0000-0003-4733-6532
Gillon, Michaël0000-0003-1462-7739
Howard, Andrew W.0000-0001-8638-0320
Additional Information:© 2014. The American Astronomical Society. Received 17 March 2014, accepted for publication 27 August 2014. Published 2 October 2014
Issue or Number:2
Record Number:CaltechAUTHORS:20141010-120207993
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:50338
Deposited By: George Porter
Deposited On:10 Oct 2014 20:09
Last Modified:10 Nov 2021 18:54

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