This is a good article. Click here for more information.

WASP-44

From Wikipedia, the free encyclopedia
Jump to: navigation, search
WASP-44
Observation data
Epoch J2000      Equinox J2000
Constellation Cetus
Right ascension 00h 15m 36.769s[1]
Declination –11° 56′ 17.30″[1]
Apparent magnitude (V) 12.9[2]
Characteristics
Spectral type G8V[2]
Astrometry
Proper motion (μ) RA: 16.2 ± 1.1[1] mas/yr
Dec.: 32.1 ± 1.4[1] mas/yr
Details
Mass 0.917 ± 0.077[3] M
Radius 0.865 ± 0.025[3] R
Surface gravity (log g) 4.481 ± 0.034[4] cgs
Temperature 5410 ± 150[2] K
Metallicity 0.06 ± 0.1[2]
Age 0.9 +1
−0.6
[2] Gyr
Other designations
2MASS J00153675-1156172[2]

WASP-44 is a G-type star in constellation Cetus that has the Jupiter-size planet WASP-44b in orbit. 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 in search of planets, starting in 2009; manual follow-up observations used 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.[4]

Observational history[edit]

WASP-44 was observed between July and November 2009 by the 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.[4] 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.[4]

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.[4]

The Leonhard Euler Telescope at La Silla Observatory in Chile was used to follow up on the discovery circling WASP-44, searching for a point at which the planet transited, or crossed in front of, its host star. One transit was detected.[4]

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.[4] The paper was submitted to the Monthly Notices of the Royal Astronomical Society on May 16, 2011.[4]

Characteristics[edit]

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.[2] WASP-44's chromosphere (outermost layer) is not active. The star also does not rotate at a high velocity.[4]

The star has an apparent magnitude of 12.9. It cannot be seen from Earth with the naked eye.[2]

Planetary system[edit]

Main article: WASP-44b

There is one known planet in the orbit of WASP-44: WASP-44b. The planet is a Hot Jupiter[4] with a mass of 0.889 Jupiters. Its radius is 1.14 times that of Jupiter. WASP-44b orbits its host star every 2.4238039 days at a distance 0.03473 AU, approximately 3.47% the mean distance between the Earth and Sun.[2] 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.[2] WASPA-44b's orbital eccentricity is fit to 0.036, indicating a mostly circular orbit.[4]

The WASP-44 planetary system[2]
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
Eccentricity Inclination Radius
b 0.889 MJ 0.03473 2.4238039 0.036[4]

References[edit]

  1. ^ a b c d Zacharias, N. et al. (2013). "The Fourth US Naval Observatory CCD Astrograph Catalog (UCAC4)". The Astronomical Journal 145 (2). 44. arXiv:1212.6182. Bibcode:2013AJ....145...44Z. doi:10.1088/0004-6256/145/2/44. Vizier catalog entry
  2. ^ a b c d e f g h i j k Schneider, J. (2011). "Notes for star WASP-44". Extrasolar Planets Encyclopaedia. Retrieved 2011-05-30. 
  3. ^ a b Mancini, D. R. et al. (2013). "Physical properties of the WASP-44 planetary system from simultaneous multi-colour photometry". Monthly Notices of the Royal Astronomical Society 430 (4): 2932–2942. arXiv:1301.3005. Bibcode:2013MNRAS.430.2932M. doi:10.1093/mnras/stt095. 
  4. ^ a b c d e f g h i j k l Anderson, D. R. et al. (2012). "WASP-44b, WASP-45b and WASP-46b: three short-period, transiting extrasolar planets". Monthly Notices of the Royal Astronomical Society 422 (3): 1988–1998. arXiv:1105.3179. Bibcode:2012MNRAS.422.1988A. doi:10.1111/j.1365-2966.2012.20635.x. 

Coordinates: Sky map 00h 15m 37s, −11° 56′ 17″