J/AJ/158/244 HAT-P-11b spectroscopic light curve fit results (Chachan+, 2019)
A Hubble PanCET study of HAT-P-11b: a cloudy Neptune with a low atmospheric
metallicity.
Chachan Y., Knutson H.A., Gao P., Kataria T., Wong I., Henry G.W.,
Benneke B., Zhang M., Barstow J., Bean J.L., Mikal-Evans T., Lewis N.K.,
Mansfield M., Lopez-Morales M., Nikolov N., Sing D.K., Wakeford H.
<Astron. J., 158, 244 (2019)>
=2019AJ....158..244C 2019AJ....158..244C (SIMBAD/NED BibCode)
ADC_Keywords: Exoplanets ; Spectroscopy ; Stars, diameters ;
Stars, double and multiple
Keywords: Exoplanet atmospheres - Exoplanet atmospheric composition
Abstract:
We present the first comprehensive look at the 0.35-5 µm transmission
spectrum of the warm (∼800 K) Neptune HAT-P-11b derived from 13 individual
transits observed using the Hubble and Spitzer Space Telescopes. Along
with the previously published molecular absorption feature in the
1.1-1.7 µm bandpass, we detect a distinct absorption feature at
1.15 µm and a weak feature at 0.95 µm, indicating the presence of
water and/or methane with a combined significance of 4.4σ. We find
that this planet's nearly flat optical transmission spectrum and attenuated
near-infrared molecular absorption features are best matched by models
incorporating a high-altitude cloud layer. Atmospheric retrievals using
the combined 0.35-1.7 µm Hubble Space Telescope (HST) transmission
spectrum yield strong constraints on atmospheric cloud-top pressure and
metallicity, but we are unable to match the relatively shallow Spitzer
transit depths without underpredicting the strength of the near-infrared
molecular absorption bands. HAT-P-11b's HST transmission spectrum is well
matched by predictions from our microphysical cloud models. Both forward
models and retrievals indicate that HAT-P-11b most likely has a relatively
low atmospheric metallicity (<4.6 Z☉ and <86 Z☉ at the 2σ
and 3σ levels respectively), in contrast to the expected trend based
on the solar system planets. Our work also demonstrates that the wide
wavelength coverage provided by the addition of the HST STIS data is
critical for making these inferences.
Description:
We observed three transits of HAT-P-11b with the Space Telescope Imaging
Spectrograph (STIS) on the HST (PI Sing & Lopez-Morales, GO 14767).
Two observations were conducted using the G430L grism (0.29-0.57 µm)
on UT 2017 February 22 and UT 2017 May 26, while a third visit on UT 2017
April 12 used the G750L grism (0.524-1.027 µm). All of our observations
were obtained using the 52"x2" slit. HAT-P-11b was observed with HST's
Wide Field Camera 3 (WFC3) instrument in 2012 (PI Deming, GO 12449) using
the G141 grism in the 256x256 subarray mode, which provides a low
resolution spectrum in the 1.1-1.7 µm wavelength range. Finally, five
transits of HAT-P-11b were also observed using the WFC3 G102 grism
(0.8-1.15 µm) in the 256x256 subarray mode (PI Bean, GO 14793) on
UT 2016 September 14, 2016 October 13, 2016 November 7, 2016 November 26,
and 2016 December 26. This grism is complementary to the G141 observations,
as both grisms together span a series of adjacent and overlapping water
and methane bands.
Objects:
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RA (ICRS) DE Designation(s)
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19 50 50.25 +48 04 51.1 HAT-P-11b = KOI-3.01
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 39 47 Spectroscopic light curve fit results
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See also:
J/ApJ/710/1724 : Follow-up photometry for HAT-P-11 (Bakos+, 2010)
J/ApJ/723/L223 : Radial velocities of HAT-P-11 (Winn+, 2010)
J/A+A/622/A172 : GTC transit light curves of HAT-P-11b (Murgas+, 2019)
Byte-by-byte Description of file:table3.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Inst Instrument (STIS or WFC3)
6- 10 A5 --- Band Bandpass identifier
12- 16 F5.3 um b_Wave [0.346/1.66] Lower wavelength edge of bandpass
18- 22 F5.3 um B_Wave [0.401/1.69] Upper wavelength edge of bandpass
23 A1 --- f_Band [*] Flag on the bandpass (1)
25- 31 F7.5 --- Rp/R* [0.05587/0.06244] Ratio of the planet's and
star's radii
33- 39 F7.5 --- e_Rp/R* [0.00011/0.00361] The 1σ uncertainty
in Rp/R*
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Note (1): Flag as follows:
* = These bandpasses and depths correspond to the Na and K lines.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 30-Jan-2020