J/AJ/162/57 g- and Ks-band flux of K2-22 with LBT (Schlawin+, 2021)
LBT Reveals Large Dust Particles and a High Mass-loss Rate for K2-22 b.
Schlawin E., Su K.Y.L., Herter T., Ridden-Harper A., Apai D.
<Astron. J., 162, 57 (2021)>
=2021AJ....162...57S 2021AJ....162...57S
ADC_Keywords: Exoplanets; Stars, K-type; Photometry, infrared; Optical
Keywords: Exoplanet astronomy ; Transmission spectroscopy ;
Extrasolar rocky planets ; Exoplanet atmospheric composition ;
Exoplanet surface composition ; Multi-color photometry
Abstract:
The disintegrating planet candidate K2-22b shows periodic and
stochastic transits best explained by an escaping debris cloud.
However, the mechanism that creates the debris cloud is unknown. The
grain size of the debris as well as its sublimation rate can be
helpful in understanding the environment that disintegrates the
planet. Here, we present simultaneous photometry with the g band at
0.48µm and KS band at 2.1µm using the Large Binocular Telescope.
During an event with very low dust activity, we put a new upper limit
on the size of the planet of 0.71R⊕ or 4500km. We also detected
a medium depth transit that can be used to constrain the dust particle
sizes. We find that the median particle size must be larger than about
0.5-1.0µm, depending on the composition of the debris. This leads
to a high mass-loss rate of about 3x108kg/s, which is consistent with
hydrodynamic escape models. If they are produced by some alternate
mechanism such as explosive volcanism, it would require extraordinary
geological activity. Combining our upper limits on the planet size
with the high mass-loss rate, we find a lifetime of the planet of less
than 370Myr. This drops to just 21Myr when adopting the 0.02M⊕
mass predicted from hydrodynamical models.
Description:
We observed the K2-22 system with the Large Binocular Telescope on 3
partial nights. We used the heterogenous binocular mode that allows
the observatory to simultaneously point to the same target using the
large binocular camera (LBC) on the SX (left) 8.4m mirror and the LBT
Utility Camera in the Infrared 2 (LUCI2) instrument on the DX (right)
8.4m mirror.
The Hereford Arizona Observatory (HAO), with its 16inch
Ritchey-Chretien telescope, was also used to monitor light curves of
K2-22 simultaneously during two of the LBT campaigns. Given the
faintness of the target, HAO photometry was obtained with an
unfiltered CCD, thus integrating light from 0.4-0.85µm, making it
similar to Kepler/K2's bandpass but with wider wings. HAO is located
at 1400m altitude, so telluric absorption is also imprinted on the
intrinsic instrument bandpass.
Objects:
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RA (2000) DE Designation(s)
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11 17 55.88 +02 37 08.6 K2-22 = K2-22
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig1.dat 41 520 Ground based photometry from UT 2020-01-25 and
UT 2020-02-20
fig2.dat 36 785 Ground based photometry from UT 2020-01-28
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See also:
J/A+A/559/A32 : Light curves of GJ3470b (Nascimbeni+, 2013)
J/A+A/579/A19 : K2 Variable Catalogue (Armstrong+, 2015)
J/A+A/579/A113 : BR light curves of GJ1214b (Nascimbeni+, 2015)
J/ApJ/818/L7 : High-speed photometry obs. WD1145+017 syst. (Gansicke+, 2016)
J/ApJS/222/14 : Planetary candidates 1st yr K2 mission (Vanderburg+, 2016)
J/ApJ/866/99 : Radii of KIC stars & planets using Gaia DR2 (Berger+,2018)
J/AJ/156/227 : Photometric observations of the K2-22 system (Colon+, 2018)
Byte-by-byte Description of file: fig1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 "month" Obs.M [Jan/Feb] Observation date in 2020, month
5- 6 I2 d Obs.D Observation date in 2020, day
8- 9 A2 --- Filt Filter used; Ks or g
11- 23 F13.5 d JD [2458873/2458900] Barycentric Julian Date
25- 32 F8.6 --- NFlux [0.98/1.02] Normalized flux in Filter
34- 41 F8.6 --- e_NFlux [0.0006/0.003] Uncertainty in NFlux
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Byte-by-byte Description of file: fig2.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Filt Filter used; Ks, g or open
6- 18 F13.5 d JD [2458876/2458878] Barycentric Julian Date
20- 27 F8.6 --- NFlux [0.96/1.02] Normalized flux in Filter
29- 36 F8.6 --- e_NFlux [0.0005/0.007] Uncertainty in NFlux
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 18-Nov-2021