J/AJ/160/188 Spectroscopic transit depths of LHS 3844b (Diamond-Lowe+, 2020)
Optical transmission spectroscopy of the terrestrial exoplanet LHS 3844b from 13
ground-based transit observations.
Diamond-Lowe H., Charbonneau D., Malik M., Kempton E.M.-R., Beletsky Y.
<Astron. J., 160, 188 (2020)>
=2020AJ....160..188D 2020AJ....160..188D
ADC_Keywords: Exoplanets; Stars, brown dwarf; Spectra, optical;
Spectra, infrared
Keywords: Exoplanet astronomy ; Exoplanet atmospheres ; Ground-based astronomy
Abstract:
Atmospheric studies of spectroscopically accessible terrestrial
exoplanets lay the groundwork for comparative planetology between
these worlds and the solar system terrestrial planets. LHS3844b is a
highly irradiated terrestrial exoplanet (R=1.303±0.022R⊕)
orbiting a mid-M dwarf 15parsecs away. Work based on near-infrared
Spitzer phase curves ruled out atmospheres with surface pressures
≳10bars on this planet. We present 13 transit observations of
LHS3844b taken with the Magellan Clay telescope and the LDSS3C
multi-object spectrograph covering 620-1020nm. We analyze each of the
13 data sets individually using a Gaussian process regression, and
present both white and spectroscopic light curves. In the combined
white light curve we achieve an rms precision of 65ppm when binning to
10minutes. The mean white light-curve value of (Rp/Rs)2 is
0.4170±0.0046%. To construct the transmission spectrum, we split
the white light curves into 20 spectrophotometric bands, each spanning
20nm, and compute the mean values of (Rp/Rs)2 in each band. We
compare the transmission spectrum to two sets of atmospheric models.
We disfavor a clear, solar composition atmosphere (µ=2.34) with
surface pressures ≳0.1bar to 5.2σ confidence. We disfavor a
clear, H2O steam atmosphere (µ=18) with surface pressures ≳0.1bar
to low confidence (2.9σ). Our observed transmission spectrum
favors a flat line. For solar composition atmospheres with surface
pressures ≳1bar we rule out clouds with cloud-top pressures of 0.1bar
(5.3σ), but we cannot address high-altitude clouds at lower
pressures. Our results add further evidence that LHS3844b is devoid of
an atmosphere.
Description:
Between June and October of 2019, the Center for Astrophysics mid
Harvard & Smithsonian awarded us 18 opportunities to observe transits
of LHS3844b with the Magellan II (Clay) telescope and the Low
Dispersion Survey Spectrograph (LDSS3C User Manual4 ) at the Las
Campanas Observatory in Chile (PI: Diamond-Lowe). Each observation
opportunity comprised 2.5hr to observe the LHS3844b transit, along
with baseline on either side with which to remove systematic noise and
measure the transit depth. We use the VPH-Red grism to observe over
the nominal wavelength range of 620-1020nm.
Objects:
------------------------------------------------------------
RA (2000) DE Designation(s) (Period)
------------------------------------------------------------
22 41 58.12 -69 10 08.3 LHS 3844 = LHS 3844 (P=0.4629279)
------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table5.dat 194 20 Spectroscopic transit depths
--------------------------------------------------------------------------------
See also:
J/A+A/537/L2 : Transmission spectrum of Venus (Ehrenreich+, 2012)
J/A+A/563/A41 : WASP-43 OSIRIS transmission spectroscopy (Murgas+, 2014)
J/ApJ/800/135 : HARPS-N radial velocities of KOI-69 (Dressing+, 2015)
J/A+A/590/A100 : Transmission spectroscopy of HAT-P-32b (Mallonn+, 2016)
J/A+A/596/A47 : FORS2 transmission spectroscopy of WASP-17b (Sedaghati+, 2016)
J/A+A/605/L9 : NIR spectrum of exoplanet HIP 65426b (Chauvin+, 2017)
J/AJ/154/109 : California-Kepler Survey III. Planet radii (Fulton+, 2017)
J/AJ/156/18 : APOGEE DR14: companions of evolved stars (Price-Whelan+,2018)
J/AJ/156/217 : Stellar properties for M dwarfs MEarth-South (Newton+, 2018)
J/A+A/624/A49 : Spectra Earth-like planets around M-dwarfs (Wunderlich+, 2019)
J/A+A/632/A69 : CaII transmission spectrum of WASP-33b & KELT-9b (Yan+, 2019)
J/MNRAS/486/5867 : Simulated Transit depths of 12 Hot Jupiters (Singh+, 2019)
J/A+A/633/A110 : K band spectrum of beta Pictoris b (GRAVITY+, 2020)
J/A+A/634/A29 : Kepler-278 and Kepler-391 spectra (Jofre+, 2020)
J/AJ/159/239 : Transmission Spectroscopy Metric of exoplanets (Guo+, 2020)
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 nm LoWave [620/1000] Lower wavelength range
6- 9 I4 nm HiWave [640/1020] Upper wavelength range
11- 14 I4 nm MiWave [630/1010] Middle of wavelength range
16- 20 F5.3 % TD1 [0.217/0.478] Transit depth of 1st observation
22- 26 F5.3 % e_TD1 [0.036/0.181] Uncertainty in TD1
28- 32 F5.3 % TD2 [0.147/0.528] Transit depth of 2nd observation
34- 38 F5.3 % e_TD2 [0.024/0.101] Uncertainty in TD2
40- 44 F5.3 % TD3 [0.28/0.504] Transit depth of 3rd observation
46- 50 F5.3 % e_TD3 [0.022/0.076] Uncertainty in TD3
52- 56 F5.3 % TD4 [0.362/0.431] Transit depth of 4th observation
58- 62 F5.3 % e_TD4 [0.014/0.046] Uncertainty in TD4
64- 68 F5.3 % TD5 [0.347/0.438] Transit depth of 5th observation
70- 74 F5.3 % e_TD5 [0.017/0.064] Uncertainty in TD5
76- 80 F5.3 % TD6 [0.359/0.454] Transit depth of 6th observation
82- 86 F5.3 % e_TD6 [0.016/0.099] Uncertainty in TD6
88- 92 F5.3 % TD7 [0.218/0.515] Transit depth of 7th observation
94- 98 F5.3 % e_TD7 [0.019/0.11] Uncertainty in TD7
100-104 F5.3 % TD8 [0.375/0.466] Transit depth of 8th observation
106-110 F5.3 % e_TD8 [0.013/0.057] Uncertainty in TD8
112-116 F5.3 % TD9 [0.351/0.457] Transit depth of 9th observation
118-122 F5.3 % e_TD9 [0.012/0.043] Uncertainty in TD9
124-128 F5.3 % TD10 [0.383/0.478] Transit depth of 10th observation
130-134 F5.3 % e_TD10 [0.014/0.045] Uncertainty in TD10
136-140 F5.3 % TD11 [0.373/0.487] Transit depth of 11th observation
142-146 F5.3 % e_TD11 [0.015/0.05] Uncertainty in TD11
148-152 F5.3 % TD12 [0.325/0.566] Transit depth of 12th observation
154-158 F5.3 % e_TD12 [0.028/0.14] Uncertainty in TD12
160-164 F5.3 % TD13 [0.346/0.454] Transit depth of 13th observation
166-170 F5.3 % e_TD13 [0.02/0.061] Uncertainty in TD13
172-177 F6.4 % TDMean [0.3901/0.4254] Inverse-variance weighted mean
transit depth
179-184 F6.4 % e_TDMean [0.005/0.0174] Uncertainty in Mean
186-189 I4 ppm RMS [1099/5377] Root Mean Square of all 13
observations
191-194 F4.2 --- Noise [1.5/1.79] Expected noise (1)
--------------------------------------------------------------------------------
Note (1): Describes how close, on average, we get to the calculated
photon noise in each band.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 08-Dec-2020