J/AJ/164/239 IR light curve of VHS1256-1257b in 2018 & 2020 epochs (Zhou+, 2022)
Roaring Storms in the Planetary-mass Companion VHS 1256-1257 b: Hubble Space
Telescope Multiepoch Monitoring Reveals Vigorous Evolution in an Ultracool
Atmosphere.
Zhou Y., Bowler B.P., Apai D., Kataria T., Morley C.V., Bryan M.L.,
Skemer A.J.,Benneke B.
<Astron. J., 164, 239 (2022)>
=2022AJ....164..239Z 2022AJ....164..239Z
ADC_Keywords: Exoplanets; Stars, brown dwarf; Spectra, infrared
Keywords: Brown dwarfs ; L dwarfs ; Atmospheric variability ; Planetary
atmospheres ; Spectroscopy ; Time series analysis ; Atmospheric
circulation ; Atmospheric clouds
Abstract:
The photometric and spectral variability of brown dwarfs probes
heterogeneous temperature and cloud distributions and traces the
atmospheric circulation patterns. We present a new 42hr Hubble Space
Telescope (HST) Wide Field Camera 3 G141 spectral time series of
VHS1256-1257b, a late L-type planetary-mass companion that has been
shown to have one of the highest variability amplitudes among
substellar objects. The light curve is rapidly evolving and best fit
by a combination of three sine waves with different periods and a
linear trend. The amplitudes of the sine waves and the linear slope
vary with the wavelength, and the corresponding spectral variability
patterns match the predictions by models invoking either heterogeneous
clouds or thermal profile anomalies. Combining these observations with
previous HST monitoring data, we find that the peak-to-valley flux
difference is 33%±2% with an even higher amplitude reaching 38% in
the J band, the highest amplitude ever observed in a substellar
object. The observed light curve can be explained by maps that are
composed of zonal waves, spots, or a mixture of the two.
Distinguishing the origin of rapid light curve evolution requires
additional long-term monitoring. Our findings underscore the essential
role of atmospheric dynamics in shaping brown-dwarf atmospheres and
highlight VHS1256-1257b as one of the most favorable targets for
studying the atmospheres, clouds, and atmospheric circulation of
planets and brown dwarfs.
Description:
We conducted spectroscopic monitoring of VHS1256b using the Hubble
Space Telescope Wild Field Camera 3 (HST/WFC3) IR Channel for 15
orbits from UT 2020 May 26 09:27:17 to 2020 May 28 03:29:24 (Program
ID: GO-16036, PI: Zhou; hereafter, we refer to this program as "Epoch
2020"). Prior to this program, our target was observed with the same
instrument for six continuous orbits from UT 2018 March 5 16:02:30 to
2018 March 6 00:42:47 (Program ID: GO-15197, PI: Bowler, results are
published in Bowler et al. 2020; hereafter, we refer to this program
as "Epoch 2018").
The spectrograph has a spectral resolution of R∼130 at 1.4µm and a
wavelength range spanning from 1.12 to 1.65µm.
Objects:
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RA (2000) DE Designation(s)
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12 50 60.192 -12 57 23.9 VHS 1256-1257 b = VHS J125060.192-125723.9 b
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
fig8.dat 95 231 *Combined light curves of VHS 1256 b in the 2018
and 2020 epochs
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Note on fig8.dat: Filter information as follows:
F127M = centered at 1.27µm, sampling the continuum on the blue side of
the water band
F139M = centered at 1.39µum, sampling the water band
F153M = centered at 1.53µm, sampling the continuum on the red side of the
water band.
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See also:
J/ApJ/814/65 : Jupiter HST light curves (Karalidi+, 2015)
J/ApJS/225/10 : Kinematic analysis of M7-L8 dwarfs (Faherty+, 2016)
J/ApJ/818/176 : HST/WFC3 NIR photometry of 2M1207b (Zhou+, 2016)
J/A+A/629/A145 : L9-T3.5 brown dwarfs light curves (Eriksson+, 2019)
J/AJ/160/63 : IR spectra of 5 brown dwarfs Gemini North IRS (Miles+, 2020)
J/AJ/160/38 : Spitzer variability detections of 79 brown dwarfs (Vos+, 2020)
J/AJ/161/42 : Volume-limited sample cool dwarfs I L0-T8 dwarfs (Best+, 2021)
J/AJ/164/143 : Spectroscopy HR8799 planets with SCExAO/CHARIS (Wang+, 2022)
Byte-by-byte Description of file: fig8.dat
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Bytes Format Units Label Explanations
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1- 18 F18.10 d JD [2458183/2458998] Julian date of observation
20- 23 I4 yr Epoch [2018/2020] Epoch, 2018 or 2022
25- 33 E9.8 10+3W/m3 G141 [3e-13/5e-13] HST/WFC3 G141 grism broadband
flux density
35- 41 E7.6 10+3W/m3 e_G141 [5e-16/8e-16] Uncertainty in G141
43- 51 E9.8 10+3W/m3 F127M [3e-13/5e-13] HST/WFC3 F127M filter flux density
53- 59 E7.6 10+3W/m3 e_F127M [1e-15/3e-15] Uncertainty in F127M
61- 69 E9.8 10+3W/m3 F139M [1e-13/3e-13] HST/WFC3 F139M filter flux density
71- 77 E7.6 10+3W/m3 e_F139M [1e-15/2e-15] Uncertainty in F139M
79- 87 E9.8 10+3W/m3 F153M [3e-13/5e-13] HST/WFC3 F153M filter flux density
89- 95 E7.6 10+3W/m3 e_F153M [1e-15/2e-15] Uncertainty in F153M
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History:
From electronic version of the journal
:wq
(End) Prepared by [AAS], Coralie Fix [CDS], 27-Jan-2023