J/ApJ/770/95 g'RcIcJ photometry of the hot Uranus GJ3470b (Fukui+, 2013)
Optical-to-near-infrared simultaneous observations for the hot Uranus GJ3470b:
a hint of a cloud-free atmosphere.
Fukui A., Narita N., Kurosaki K., Ikoma M., Yanagisawa K., Kuroda D.,
Shimizu Y., Takahashi Y.H., Ohnuki H., Onitsuka M., Hirano T., Suenaga T.,
Kawauchi K., Nagayama S., Ohta K., Yoshida M., Kawai N., Izumiura H.
<Astrophys. J., 770, 95 (2013)>
=2013ApJ...770...95F 2013ApJ...770...95F
ADC_Keywords: Planets ; Photometry, VRI ; Photometry, infrared ;
Stars, double and multiple
Keywords: planetary systems; planets and satellites: atmospheres;
planets and satellites: individual: GJ3470b;
stars: individual: GJ3470; techniques: photometric
Abstract:
We present optical (g', Rc, and Ic) to near-infrared (J)
simultaneous photometric observations for a primary transit of
GJ3470b, a Uranus-mass transiting planet around a nearby M dwarf, by
using the 50cm MITSuME telescope and the 188cm telescope, both at the
Okayama Astrophysical Observatory. From these data, we derive the
planetary mass, radius, and density as 14.1 ±1.3M⊕,
4.32-0.10+0.21R⊕, and 0.94±0.12g/cm3, respectively, thus
confirming the low density that was reported by Demory et al.
(2013ApJ...768..154D 2013ApJ...768..154D) based on the Spitzer/IRAC 4.5µm photometry
(0.72-0.12+0.13g/cm3). Although the planetary radius is about 10%
smaller than that reported by Demory et al., this difference does not
alter their conclusion that the planet possesses a hydrogen-rich
envelope whose mass is approximately 10% of the planetary total mass.
On the other hand, we find that the planet-to-star radius ratio
(Rp/Rs) in the J band (0.07577-0.00075+0.00072) is smaller
than that in the Ic(0.0802±0.0013) and 4.5µm
(0.07806-0.00054+0.00052) bands by 5.8%±2.0% and 2.9%±1.1%,
respectively. A plausible explanation for the differences is that the
planetary atmospheric opacity varies with wavelength due to absorption
and/or scattering by atmospheric molecules. Although the significance
of the observed Rp/Rsvariations is low, if confirmed, this fact
would suggest that GJ3470b does not have a thick cloud layer in the
atmosphere. This property would offer a wealth of opportunity for
future transmission-spectroscopic observations of this planet to
search for certain molecular features, such as H2O, CH4, and CO,
without being prevented by clouds.
Description:
We conducted J-band photometric observations for GJ3470 on the
expected transit night of 2012 November 15 by using the near-infrared
imaging and spectroscopic instrument ISLE, which is mounted on the
Cassegrain focus of the 188cm telescope at the Okayama Astrophysical
Observatory in Japan. The observations spanned 4.4hr, covering the
entire transit (1.9hr) as well as 1.8hr prior to and 0.75hr posterior
to the transit.
Simultaneously with the ISLE J-band observations, we also conducted
photometric observations for the transit of GJ3470b in optical
wavelengths by using the 50cm MITSuME telescope at the Okayama
Astrophysical Observatory; in Ic, Rc and g' filters.
Objects:
---------------------------------------------------------------
RA (ICRS) DE Designation(s) (Period)
---------------------------------------------------------------
07 59 05.87 +15 23 29.5 GJ3470 = NLTT 18739
07 59 05.87 +15 23 29.5 GJ3470b = GJ 3470 b (P=3.33665)
---------------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 32 843 The J, Ic, Rc, and g' light curves
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See also:
J/MNRAS/430/2932 : WASP-44 griz light curves (Mancini+, 2013)
J/A+A/559/A33 : Near-IR Spectrophotometry of GJ 3470b (Crossfield+, 2013)
J/A+A/559/A32 : Light curves of GJ3470b (Nascimbeni+, 2013)
J/A+A/556/A150 : SWEETCat I. Stellar param. for host stars (Santos+, 2013)
J/A+A/552/A119 : Planet-star and moon-planet interaction (Saur+, 2013)
J/A+A/546/A27 : Radial velocity and photometry for GJ3470 (Bonfils+, 2012)
J/A+A/546/A14 : Limb-darkening for CoRoT, Kepler, Spitzer (Claret+, 2012)
J/A+A/538/A46 : Transit observations of GJ1214b (de Mooij+, 2012)
J/ApJ/757/112 : Stellar diameters. II. K and M-stars (Boyajian+, 2012)
J/ApJ/747/35 : HST/WFC3 transit observation of GJ1214b (Berta+, 2012)
J/MNRAS/396/1023 : Transiting planetary system WASP-5 (Southworth+, 2009)
J/ApJ/683/1076 : Transits of exoplanet XO-3b (Winn+, 2008)
J/AJ/106/773 : Mass-luminosity relation (Henry+, 1993)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- Filt Filter used in the observation
4- 14 F11.6 d BJD Barycentric Julian Date; BJD-2450000 (1)
16- 23 F8.6 --- Flux [0.979/1.011] Relative flux in Filt (2)
25- 32 F8.6 --- e_Flux [0.001/0.007] Error in Flux
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Note (1): Based on Barycentric Dynamical Time.
Note (2): All fluxes are corrected for baseline trends.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 09-Jan-2015