J/AJ/165/5 SDSS ugri photometry of HD 189733 (Gardner-Watkins+, 2023)
A Six Year, Low-resolution, Multibroadband Transit Photometry Study of
HD189733b.
Gardner-Watkins C.N., Kobulnicky H.A., Jang-Condell H., Kasper D.H.,
Parker B.A., Bucci T., Cook E.M., Doublestein K.A., Freels C.,
Galloway D.G.T., Helck S., Komlodi C., Lindman M.J., Lyon M.,
Piccone A.N.,Wilkerson S.
<Astron. J., 165, 5 (2023)>
=2023AJ....165....5G 2023AJ....165....5G
ADC_Keywords: Exoplanets; Stars, K-type; Photometry, SDSS; Photometry, UVBGRI
Keywords: Exoplanet detection methods ; Exoplanet atmospheres ; Transit
photometry
Abstract:
Transmission spectroscopy offers an invaluable opportunity to
characterize the atmospheres of exoplanets. We present new
ground-based optical transmission spectra of the hot Jupiter
HD189733b, derived from nine transits observed over a six year time
span (2016-2021) using near-simultaneous u' g' r' i' broadband
observations. We achieve an average (best) precision of 435(280)ppm by
implementing an optical diffuser on the prime focus spectrograph from
the 2.3m Wyoming Infrared Observatory telescope. The data provide new
measurements of the apparent planetary radius with respect to the
stellar radius, the spectral index of atmospheric opacity, and the
time variability of the two quantities. Our results indicate an
enhanced spectral slope in the optical regime ∼2.4 times steeper than
would be expected from canonical Rayleigh scattering and that is
consistent with earlier measurements of a super-Rayleigh slope (SRS).
While the effect of stellar activity on the transmission spectrum
complicates the measurement of the spectral slope, our multiepoch data
set over six years can measure and average over stellar variations,
yielding a mean spectral index of -9.9±4.4. The 1200K equilibrium
temperature of HD189733b places it in a sweet spot for the formation
of SRSs and is consistent with vigorously mixing hazes in the
atmosphere. Additionally, we find variations in the depth of the
lightcurve during two of the transits, explainable as an increase in
occulted star spots during June 2021. Although the star is active, the
mean level of stellar activity does not seem to vary dramatically over
our six years of observations, leading us to conclude that the
variability in stellar activity is modest at most.
Description:
Two full transits and one partial transit were observed using
defocused (FWHM∼100pixels) observations in the SDSS u' g' r' i'
filters during the summer months of 2016 and 2017. Five full transits
and one partial transit were observed using diffused (FWHM∼58pixels)
observations in the four same SDSS filters during the summer months of
2020 and 2021.
Objects:
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RA (2000) DE Designation(s) (Period)
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20 00 43.71 +22 42 39.0 HD 189733 = HD 189733 (P=2.2d)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 110 1113 Extracted photometry from astroImage J
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See also:
J/MNRAS/396/1023 : Transiting planetary system WASP-5 (Southworth+, 2009)
J/other/A+ARV/17.251 : Stars observed with Doppler imaging (Strassmeier, 2009)
J/A+A/529/A75 : Limb-darkening coefficients (Claret+, 2011)
J/ApJ/770/36 : APOSTLE transits of XO-2 system (Kundurthy+, 2013)
J/MNRAS/436/2 : Transits of WASP-19b (Mancini+, 2013)
J/ApJ/791/55 : HD 189733b in transit light curve (McCullough+, 2014)
J/ApJ/819/27 : OAO/MuSCAT light curves of HAT-P-14b (Fukui+, 2016)
J/A+A/587/A67 : WASP-49b FORS2 multi-epoch spectra (Lendl+, 2016)
J/MNRAS/472/1618 : Kepler study of starspot lifetimes (Giles+, 2017)
J/AJ/153/136 : Planets and their host stars with Gaia plxs (Stassun+, 2017)
J/A+A/628/A115 : WASP-12, CoRoT-1 and TrES-3 light curves (von Essen+, 2019)
J/MNRAS/497/5182 : WASP-21b light curves (Alderson+, 2020)
J/A+A/642/A50 : WASP-74 grizs light curves (Luque+, 2020)
J/MNRAS/500/5420 : Transit light curves of WASP-104b (Chen+, 2021)
J/MNRAS/510/4857 : WASP-94A light curves (Ahrer+, 2022)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d JD [2457602/2459440] Julian Date at mid-exposure
16- 28 F13.5 d BJD [2457602/2459440] Barycentric Julian Dates in
Barycentric Dynamical Time
31- 31 A1 --- Filt Filter; u, g, r or I
34- 41 F8.6 --- Flux [0.97/1.1] Normalized flux ratio in Filter
44- 51 F8.6 --- e_Flux [7e-05/0.0006] Normalized flux error
54- 57 F4.2 --- Airmass [1.05/1.98] Airmass of the target coordinates at
mid-exposure
60- 65 F6.1 pix X [805/2662] X-location in FITS coordinates of the
center of aperture
68- 73 F6.1 pix Y [1583/2119] Y-location in FITS coordinates of the
center of aperture
76- 78 I3 s Texp [11/320] Exposure time
80- 90 F11.1 ct Sum Sum of net integrated counts in all comparison
apertures (1)
92-102 F11.1 ct Count Net integrated counts within aperture
104-110 F7.2 --- Sky/Pix [148/5867] Sky Background flux / pixel
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Note (1): gain(e-/ADU)=2.6, read noise(e-)=5.2
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 03-Mar-2023