| Issue |
A&A
Volume 530, June 2011
|
|
|---|---|---|
| Article Number | A5 | |
| Number of page(s) | 5 | |
| Section | Planets and planetary systems | |
| DOI | https://doi.org/10.1051/0004-6361/201016231 | |
| Published online | 27 April 2011 | |
A ground-based KS-band detection of the thermal emission from the transiting exoplanet WASP-4b⋆,⋆⋆
1
Department of Astronomy and AstrophysicsP. Universidad Católica de Chile.
Av. Vicuña Mackenna 4860,
7820436 Macul,
Santiago,
Chile
e-mail: cccacere@astro.puc.cl
2
European Southern Observatory, Av. Alonso de Córdova 3107, Casilla 19,
Santiago 19001,
Chile
3
Department of Astrophysical Sciences, Princeton
University, Princeton, NJ
08544,
USA
4
Observatoire de Genève, Université de Genève,
51 Ch. des
Maillettes, 1290
Sauverny,
Switzerland
5
ESA-STScI, 3700 San Martin Drive, Batlimore, MD
21218,
USA
6
Department of Astronomy, Universidad de Concepción,
Casilla 160-C, Concepción, Chile
7
Obserwatorium Astronomiczne Uniwersytetu Warszawskiego, Aleje
Ujazdowskie 4, 00-478
Warszawa,
Poland
Received:
29
November
2010
Accepted:
30
March
2011
Context. Secondary eclipses are a powerful tool to measure directly the thermal emission from extrasolar planets, and to constrain their type and physical parameters.
Aims. We started a project to obtain reliable broad-band measurements of the thermal emission of transiting exoplanets.
Methods. Ground-based high-cadence near-infrared relative photometry was used to obtain a sub-millimagnitude precision light curve of a secondary eclipse of WASP-4b – a 1.12 MJ hot Jupiter on a 1.34 day orbit around G7V star.
Results. The data show a clear ≥10σ detection of the
planet’s thermal emission at 2.2 μm. The calculated thermal emission
corresponds to a fractional eclipse depth of 
%,
with a related brightness temperature in KS of
TB = 1995 ± 40 K, centered at
HJD.
We could set a limit on the eccentricity of
ecosω = 0.0027 ± 0.0018, compatible with a near-circular
orbit.
Conclusions. The calculated brightness temperature and the specific models suggest a highly inefficient redistribution of heat from the day-side to the night-side of the planet, and a consequent emission mainly from the day-side. The high-cadence ground-based technique is capable of detecting the faint signal of the secondary eclipse of extrasolar planets, which makes it a valuable complement to space-based mid-IR observations.
Key words: planetary systems / eclipses / stars: individual: WASP-4b / techniques: photometric
Based on observations collected at the European Southern Observatory, Chile. Programme 083.C-0528.
Full Table 1 is only available at CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/530/A5
© ESO, 2011
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