Accurate Spitzer infrared radius measurement for the hot Neptune GJ 436b
Abstract
We present Spitzer Space Telescope infrared photometry of a primary transit of the hot Neptune GJ 436b. The observations were obtained using the 8 μm band of the InfraRed Array Camera (IRAC). The high accuracy of the transit data and the weak limb-darkening in the 8 μm IRAC band allow us to derive (assuming M = 0.44 ± 0.04 M_⊙ for the primary) a precise value for the planetary radius (4.19+0.21-0.16 R_⊕), the stellar radius (0.463+0.022-0.017 R_⊙), the orbital inclination (85.90°+0.19°-0.18°) and transit timing (2454280.78186+0.00015-0.00008 HJD). Assuming current planet models, an internal structure similar to that of Neptune with a small H/He envelope is necessary to account for the measured radius of GJ 436b.
The photometric data are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/471/L51- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 2007
- DOI:
- 10.1051/0004-6361:20078283
- arXiv:
- arXiv:0707.2261
- Bibcode:
- 2007A&A...471L..51G
- Keywords:
-
- techniques: photometric;
- eclipses;
- stars: individual: GJ 436;
- planetary systems;
- infrared: general;
- Astrophysics
- E-Print:
- Accepted for publication in A&