J/AJ/159/278 He-filter observations of WASP-69b & WASP-52b (Vissapragada+, 2020)
Constraints on metastable Helium in the atmospheres of WASP-69b and WASP-52b
with ultranarrowband photometry.
Vissapragada S., Knutson H.A., Jovanovic N., Harada C.K., Oklopcic A.,
Eriksen J., Mawet D., Millar-Blanchaer M.A., Tinyanont S., Vasisht G.
<Astron. J., 159, 278 (2020)>
=2020AJ....159..278V 2020AJ....159..278V
ADC_Keywords: Exoplanets; Photometry, infrared
Keywords: Exoplanet astronomy ; Exoplanet atmospheres ; Planetary atmospheres ;
Transmission spectroscopy ; Infrared photometry ;
Narrow band photometry
Abstract:
Infrared observations of metastable 23S helium absorption with ground-
and space-based spectroscopy are rapidly maturing, as this species is
a unique probe of exoplanet atmospheres. Specifically, the transit
depth in the triplet feature (with vacuum wavelengths near 1083.3nm)
can be used to constrain the temperature and mass-loss rate of an
exoplanet's upper atmosphere. Here, we present a new photometric
technique to measure metastable 23S helium absorption using an
ultranarrowband filter (FWHM 0.635nm) coupled to a beam-shaping
diffuser installed in the Wide-field Infrared Camera on the 200inch
Hale Telescope at Palomar Observatory. We use telluric OH lines and a
helium arc lamp to characterize refractive effects through the filter
and to confirm our understanding of the filter transmission profile.
We benchmark our new technique by observing a transit of WASP-69b and
detect an excess absorption of 0.498%±0.045% (11.1σ),
consistent with previous measurements after considering our bandpass.
We then use this method to study the inflated gas giant WASP-52b and
place a 95th percentile upper limit on excess absorption in our helium
bandpass of 0.47%. Using an atmospheric escape model, we constrain the
mass-loss rate for WASP-69b to be 5.25-0.46+0.65x10-4MJ/Gyr
(3.32-0.56+0.67x10-3MJ/Gyr) at 7000K (12000K). Additionally,
we set an upper limit on the mass-loss rate of WASP-52b at these
temperatures of 2.1x10-4MJ/Gyr (2.1x10-3MJ/Gyr). These results
show that ultranarrowband photometry can reliably quantify absorption
in the metastable helium feature.
Description:
We observed WASP-69b through our helium filter and beam-shaping
diffuser on 2019-August-16-(UT), and we observed WASP-52b with the
same setup on 2019-September-17-(UT).
Our experiment is analogous to broadband transit photometry performed
previously (Vissapragada+, 2020AJ....159..108V 2020AJ....159..108V) with Wide-field
Infrared Camera (WIRC) on the Hale 200" telescope at Palomar
Observatory. The sole difference is that we use an ultranarrowband
filter (manufactured by Alluxa) that is centered on the helium
feature.
Specifically, our filter has a center wavelength of 1083.3nm in
vacuum, at 77K, and at an angle of incidence (AOI) of 7°; an FWHM
of 0.635nm; and a maximum transmission of 95.6% (averaged across five
positions on the filter). To cover the full spectral range to which
our 2.5µm cutoff Hawaii-II detector is sensitive, the filter also
has OD4 absolute out-of-band blocking (i.e., a transmission less than
0.01% everywhere outside the passband) from 500-3000nm. We
additionally utilize an engineered diffuser (located in a separate
filter wheel from the helium filter) that molds the stellar
point-spread functions (PSFs) into a top-hat shape with a FWHM of 3".
Objects:
----------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------
21 00 06.20 -05 05 40.0 WASP-69b = WASP-69b
23 13 58.76 +08 45 40.6 WASP-52b = WASP-52b
----------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
fig1.dat 46 30000 Laboratory measurements of the helium filter
transmission profile
fig4a.dat 64 271 Unbinned helium light curve, WASP-69b
fig4b.dat 64 177 Unbinned helium light curve, WASP-52b
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See also:
J/A+A/549/A134 : 4 new WASP transiting close-in giant planets (Hebrard+,2013)
J/MNRAS/445/1114 : WASP-69b, WASP-70Ab and WASP-84b (Anderson+, 2014)
J/A+A/581/A47 : Lines and continuum sky emission in the NIR (Oliva+, 2015)
J/A+A/586/A75 : Simulations of hot gas planets atmospheres (Salz+, 2016)
J/A+A/608/A135 : Na detection in WASP-69b atmosphere (Casasayas-Barris+,2017)
J/ApJ/839/97 : HeI 5876 & 10830Å EWs solar-type stars (Andretta+, 2017)
J/A+A/600/L11 : GTC transit light curves of WASP-52b (Chen+, 2017)
J/AJ/154/109 : California-Kepler Survey. III. Planet radii (Fulton+, 2017)
J/MNRAS/465/843 : Light curves of WASP-52 (Mancini+, 2017)
J/AJ/156/264 : California-Kepler Survey. VII. Planet radius (Fulton+, 2018)
J/AJ/159/211 : Exoplanets parameters from Kepler and K2 (Cloutier+, 2020)
J/A+A/634/L4 : HST/STIS FUV spectra of K2-18 (dos Santos+, 2020)
J/ApJS/247/28 : K2 star param. from Gaia & LAMOST (Hardegree-Ullman+, 2020)
Byte-by-byte Description of file: fig1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- Seq [0/29999] Sequential number
7- 24 F18.13 nm wave [1070/1100] Wavelength
26- 46 F21.19 --- trans [0/0.96] Transmission
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Byte-by-byte Description of file: fig4a.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 F23.20 d Time [-0.14/0.09] Time, days relative to transit center
25- 42 F18.16 --- Flux [0.97/1.01] Relative Flux
44- 64 F21.19 --- e_Flux [0.002/0.003] Flux error
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Byte-by-byte Description of file: fig4b.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 F23.20 d Time [-0.15/0.07] Time, days relative to transit center
25- 42 F18.16 --- Flux [0.95/1.02] Relative Flux
44- 64 F21.19 --- e_Flux [0.005/0.008] Flux error
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History:
From electronic version of the journal
(End) Prepared by [AAS), Coralie Fix [CDS], 31-Aug-2020