WASP-44 is a G-type star about 1,180 light-years (360 parsecs) away in the constellation Cetus that is orbited by the Jupiter-size planet WASP-44b. The star is slightly less massive and slightly smaller than the Sun; it is also slightly cooler, but is more metal-rich. The star was observed by SuperWASP, an organization searching for exoplanets, starting in 2009; manual follow-up observations using WASP-44's spectrum and measurements of its radial velocity led to the discovery of the transiting planet WASP-44b. The planet and its star were presented along with WASP-45b and WASP-46b on May 17, 2011 by a team of scientists testing the idea that hot Jupiters tend to have circular orbits, an assumption that is made when the orbital eccentricity of such planets are not well-constrained.[3]
Observational history
WASP-44 was observed between July and November 2009 by WASP-South, a station of the SuperWASP planet-searching program based at the South African Astronomical Observatory. Observations of the star revealed a periodic decrease in its brightness. WASP-South, along with the SuperWASP-North station at the Roque de los Muchachos Observatory on the Canary Islands, collected 15,755 photometric observations, allowing scientists to produce a more accurate light curve.[3] Another set of observations yielded a 6,000 point photometric data set, but the light curve was prepared late and was not considered in the discovery paper.[3]
The South African Astronomical Observatory, base of the WASP-South station, where WASP-44 was first observed
In 2010, a European science team investigated the star using the CORALIE spectrograph and collected seventeen spectra of WASP-44. From the spectra, radial velocity measurements were extrapolated. Analysis of collected CORALIE data ruled out the possibility that the detected radial velocity was caused by the blended spectrum of a spectroscopic binary star, supporting the possibility that the body orbiting WASP-44 was indeed a planet, designated WASP-44b.[3]
The Leonhard Euler Telescope at La Silla Observatory in Chile was used to follow up on the planet circling WASP-44, searching for a point at which the planet transited, or crossed in front of, its host star. One transit was detected.[3]
WASP-44, its recently discovered planet, the planets orbiting WASP-45 and WASP-46, and a discussion exploring the validity of the common assumption amongst scientists that closely orbiting hot Jupiter planets have highly circular orbits unless proven otherwise, were reported in a single discovery paper that was published on May 17, 2011 by the Royal Astronomical Society.[3] The paper was submitted to the Monthly Notices of the Royal Astronomical Society on May 16, 2011.[3]
Characteristics
WASP-44 is a G-type star (the same class of star as the Sun) that is located in the Cetus constellation. WASP-44 has a mass that is 0.951 times that of the Sun. In terms of size, WASP-44 has a radius that is 0.927 times that of the Sun. WASP-44 has an effective temperature of 5410 K (cooler than the Sun). However, the star is metal-rich with relation to the Sun. Its measured metallicity is [Fe/H] = 0.06, or 1.148 times that the amount of iron found in the Sun.[6] WASP-44's chromosphere (outermost layer) is not active. The star also does not rotate at a high velocity.[3]
There is one known planet in the orbit of WASP-44: WASP-44b. The planet is a hot Jupiter[3] with a mass of 0.889 times that of Jupiter. Its radius is 1.14 times that of Jupiter. WASP-44b orbits its host star every 2.4238039 days at a distance of 0.03473 AU, approximately 3.47% the mean distance between the Earth and Sun.[6] With an orbital inclination of 86.02º, WASP-44b has an orbit that exists almost edge-on to its host star with respect to Earth.[6] WASP-44b's orbital eccentricity is fit to 0.036, indicating a mostly circular orbit.[3] An analysis of transit timing variations to search for additional planets was negative.[7]
