J/ApJ/818/176 HST/WFC3 NIR photometry of 2M1207b (Zhou+, 2016)
Discovery of rotational modulations in the planetary-mass companion 2M1207b:
intermediate rotation period and heterogeneous clouds in a low gravity
atmosphere.
Zhou Y., Apai D., Schneider G.H., Marley M.S., Showman A.P.
<Astrophys. J., 818, 176 (2016)>
=2016ApJ...818..176Z 2016ApJ...818..176Z (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Photometry, infrared ; Planets
Keywords: brown dwarfs; planets and satellites: atmospheres;
planets and satellites: individual: 2M1207b; techniques: photometric
Abstract:
Rotational modulations of brown dwarfs have recently provided powerful
constraints on the properties of ultra-cool atmospheres, including
longitudinal and vertical cloud structures and cloud evolution.
Furthermore, periodic light curves directly probe the rotational
periods of ultra-cool objects. We present here, for the first time,
time-resolved high-precision photometric measurements of a
planetary-mass companion, 2M1207b. We observed the binary system with
Hubble Space Telescope/Wide Field Camera 3 in two bands and with two
spacecraft roll angles. Using point-spread function-based photometry,
we reach a nearly photon-noise limited accuracy for both the primary
and the secondary. While the primary is consistent with a flat light
curve, the secondary shows modulations that are clearly detected in
the combined light curve as well as in different subsets of the data.
The amplitudes are 1.36% in the F125W and 0.78% in the F160W filters,
respectively. By fitting sine waves to the light curves, we find a
consistent period of 10.7-0.6+1.2hr and similar phases in both
bands. The J- and H-band amplitude ratio of 2M1207b is very similar to
a field brown dwarf that has identical spectral type but different J-H
color. Importantly, our study also measures, for the first time, the
rotation period for a directly imaged extra-solar planetary-mass
companion.
Description:
We obtained direct images of the 2M1207A+b system on UT 2014 April 11
from 08:07:47 (JD 2456758.838738) to 16:53:18 (JD 2456759.203681)
using HST and its Wide Field Camera 3 (WFC3, pixel_scale=0.130mas/pixel)
in the frame of the HST Program GO-13418 (PI: D. Apai). We acquired
the observations in filters F125W (λpivot=1245.9nm,
FWHM=301.5nm) and F160W (λpivot=1540.52, FWHM=287.9nm),
roughly corresponding to the J and H bands.
Objects:
---------------------------------------------------------------
RA (ICRS) DE Designation(s)
---------------------------------------------------------------
12 07 33.47 -39 32 54.0 2M1207A = 2MASS J12073346-3932539
12 07 33.50 -39 32 54.4 2M1207b = NAME 2M1207b
---------------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 43 70 HST/WFC3 F125W photometry results
table2.dat 43 64 HST/WFC3 F160W photometry results
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See also:
J/ApJ/814/65 : Jupiter HST light curves (Karalidi+, 2015)
J/MNRAS/444/711 : Photometric distances of exoplanets (Triaud+, 2014)
J/A+A/562/A127 : NIR integral field spectra of 15 M-L dwarfs (Bonnefoy+, 2014)
J/ApJS/208/9 : Intrinsic colors & temperatures of PMS stars (Pecaut+, 2013)
J/ApJ/773/168 : Submm fluxes of very low-mass stars and BDs (Mohanty+, 2013)
J/ApJ/747/35 : HST/WFC3 transit observation of GJ1214b (Berta+, 2012)
J/A+A/517/A76 : Near-IR spectrum of 2M1207b (Patience+, 2010)
J/ApJ/689/1295 : Lithium test implications for BDs (Kirkpatrick+, 2008)
Byte-by-byte Description of file: table[12].dat
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Bytes Format Units Label Explanations
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1 I1 --- Orbit [1/6] Orbit number (1)
3- 5 I3 deg PA [202/227] Position angle
7 I1 --- Dither [1/4] Dither position (2)
9- 13 F5.3 h Time [0/9] Time from start of the observations
15- 22 F8.2 ct/s Flux [62867/78848] Primary flux in electrons/s
24- 29 F6.4 --- NFlux [0.98/1.01] Normalized primary flux
31- 36 F6.2 ct/s CFlux [180/328] Companion flux in electrons/s
38- 43 F6.4 --- NCFlux [0.95/1.05] Normalized companion flux
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Note (1): The observations applied space craft rolls each two orbits to allow
roll-subtraction of the primary. The telescope roll angles for orbit
1, 3, and 5, and those for 2, 4, and 6 differed by 25°. At the
separation of 2M1207b, this angle difference corresponds to a
displacement of 0.34", or 2.75 and 2.30 resolution elements in
F125W and F160W, respectively.
Note (2): To improve sampling and reduce the risk that the core of point-spread
function (PSF) is affected by bad pixels, we applied a 4-point dither
pattern with differential "X/Y" offsets of 1.375" in the detector
frame, providing optimal non-integral (half pixel) step of 10.5 and
8.5 pixels in F125W and F160W, respectively. In total, we obtained
70 and 64 images in F125W and F160W, respectively.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 09-May-2016