Physical properties and radius variations in the HAT-P-5 planetary system from simultaneous four-colour photometry

Abstract

The radii of giant planets, as measured from transit observations, may vary with wavelength due to Rayleigh scattering or variations in opacity. Such an effect is predicted to be large enough to detect using ground‐based observations at multiple wavelengths. We present the defocused photometry of a transit in the HAT‐P‐5 system, obtained simultaneously through Strömgren u, Gunn g and r, and Johnson I filters. Two more transit events were observed through a Gunn r filter. We detect a substantially larger planetary radius in u, but the effect is greater than predicted using theoretical model atmospheres of gaseous planets. This phenomenon is most likely to be due to systematic errors present in the u‐band photometry, stemming from variations in the transparency of Earth’s atmosphere at these short wavelengths. We use our data to calculate an improved orbital ephemeris and to refine the measured physical properties of the system. The planet HAT‐P‐5 b has a mass of and a radius of (statistical and systematic errors, respectively), making it slightly larger than expected according to standard models of coreless gas‐giant planets. Its equilibrium temperature of 1517 ± 29 K is within 60 K of that of the extensively studied planet HD 209458 b.

Ground-based near-UV observations of 15 transiting exoplanets: constraints on their atmospheres and no evidence for asymmetrical transits

“…The large scaleheight variations are similar with the 13H variation found for WASP-103b (Southworth et al 2015). These results are consistent with other exoplanets not having flat spectrum (HD 209458b, Sing et al 2008; HAT-P-5b, Southworth et al 2012b;GJ 3470b, Nascimbeni et al 2013;Qatar-2, Mancini et al 2014).…”

“…There have been extensive photometric and spectroscopic studies of WASP-12b (López-Morales et al 2010;Campo et al 2011;Chan et al 2011;Croll et al 2011;Husnoo et al 2011;Maciejewski et al 2011Maciejewski et al , 2013Madhusudhan et al 2011;Cowan et al 2012;Crossfield, Hansen & Barman 2012;Haswell et al 2012;Sada et al 2012;Sokov et al 2012;Southworth et al 2012b;Zhao et al 2012;Copperwheat et al 2013;Crossfield et al 2013;Föhring et al 2013;Fossati et al 2013;Mandell et al 2013;Sing et al 2013;Swain et al 2013;Bechter et al 2014 Table 14. Physical properties of WASP-12b, WASP-33b, WASP-36b, WASP-44b, WASP-48b, and WASP-77Ab derived from the light-curve modelling.…”

“…For the symmetric transits, nine hot Jupiters (HAT-P-1b, HAT-P-12b, WASP43b, are observed to have a constant planetary radii from near-UV to optical wavelengths Turner et al 2013;Bento et al 2014;Nikolov et al 2014;Pearson, Turner & Sagan 2014;Mallonn et al 2015;Ricci et al 2015;Sing et al 2016). Additionally, 11 exoplanets with symmetric light curves (GJ 3470b, HD 189733b, HD 209458b, HAT-P-5b, HATP12b, WASP-6b, WASP-12b, WASP-17b, WASP-31b, WASP-39b, XO-2b) are observed to have a larger near-UV radii than optical wavelengths Sing et al 2008Sing et al , 2011Sing et al , 2013Sing et al , 2015Sing et al , 2016Southworth et al 2012b;Nascimbeni et al 2013;Zellem et al 2015). There seems to be a wavelength distinction between asymmetric and symmetric lights where asymmetric transits are only observed below 300 nm.…”

Erratum: Physical properties, star-spot activity, orbital obliquity and transmission spectrum of the Qatar-2 planetary system from multicolour photometry

“…Simultaneous multiband observations of planetary transits have been obtained for several TEP systems using the instruments BUSCA (Southworth et al 2012b;Mancini et al 2013c), GROND (de Mooij et al 2012;Bayliss et al 2013;Mancini et al 2013a,b;Mohler-Fischer et al 2013;Nikolov et al 2013;Penev et al 2013;Southworth et al 2013), ULTRACAM (Bento et al 2013;Copperwheat et al 2013) and SIRIUS (Narita et al 2013). Table 1.…”

Effects of refraction on transmission spectra of gas giants: decrease of the Rayleigh scattering slope and breaking of retrieval degeneracies

“…Either way, this slope provides an important constraint on the properties of exoplanetary atmospheres, and has been detected in a few exoplanets, e.g. HD 209458b (Knutson et al 2007;Sing et al 2008), HD 189733b ), HAT-P-5b (Southworth et al 2012), WASP-12b , GJ 3470b (Nascimbeni et al 2013), WASP-6b (Jordán et al 2013;Nikolov et al 2015), Qatar-2b (Mancini et al 2014), WASP-31b , and WASP-103b (Southworth et al 2015).…”