New ‘hot Jupiter’ with short orbital period discovered

(Top) The TRES RV measurements of KELT-20b with the best
fit model shown in red. The residuals to the fit are shown
below. (Bottom) The RV measurements phase-folded to the global
fit determined ephemeris. The predicted RM effect is shown at
0.25 phase. The residuals are shown below. Credit: Lund et al.,
2017.

(Phys.org)—An international team of astronomers reports the
discovery of a new “hot Jupiter” exoplanet with a short
orbital period of just three and a half days. The newly
detected giant planet, designated KELT-20b, circles a rapidly
rotating star known as HD 185603 (or KELT-20). The finding
was presented in a paper published July 5 on arXiv.org.

The new planet was identified by a group of researchers led by
Michael Lund of the Vanderbilt University in Nashville,
Tennessee. The astronomers observed HD 185603 using the
KELT-North telescope in Arizona to identify the initial transit
signal of a potential planet. The observations were made as
part of the Kilodegree Extremely Little Telescope (KELT)
survey, which is dedicated to searching for transiting
exoplanets around bright .

The observational campaign was carried out from May to November
2014, and allowed the scientists to identify KELT-20b as an
exoplanet candidate. Afterwards, the researchers analyzed
archival data and conducted follow-up observations and
high-resolution imaging of the object, which resulted in
confirming the planetary status of KELT-20b.

“We identified the initial transit signal in KELT-North survey
data. Archival and follow-up photometry, the Gaia parallax,
radial velocities, Doppler tomography, and adaptive optics
imaging were used to confirm the planetary nature of the
companion and characterize the system,” the authors wrote in
the paper.

According to the study, KELT-20b has a radius of about 1.73
Jupiter radii and a maximum mass of 3.5 Jupiter masses. It
orbits its host every 3.47 days at a distance of approximately
0.05 AU. The planet’s equilibrium temperature is about 2,261 K.

The derived parameters of KELT-20b indicate that is belongs to
group of known as “hot Jupiters.” These
exoworlds are similar in characteristics to the solar system’s
biggest planet, with orbital periods of less than 10 days. They
have high surface temperatures, as they orbit their host stars
very closely.

The researchers emphasized that the newly discovered planetary
system is extraordinary in several ways and that the planet
itself is unusual when compared to other “hot Jupiters.”

“The KELT-20 system represents one of the most extreme
transiting hot Jupiter systems, and indeed, one of the most
extreme transiting exoplanet systems yet discovered by several
measures. The host star is both exceptionally bright (V ∼ 7.6),
and exceptionally hot (Teff ~ 8,700 K). It is only the sixth A
star known to host a transiting giant companion. The planet
itself is on a relatively short period orbit of P ~ 3.5 days,
and thus receives an extreme amount of stellar insolation,
resulting in an estimated equilibrium temperature of ∼ 2,250
K,” the team concluded.

They added that KELT-20b is a great example of a “hot Jupiter”
suffering from extreme stellar irradiation, particularly in
ultraviolet wavelengths. Therefore, the planet is an excellent
target for detailed follow-up observations and
characterization.

Explore further:

‘Hot Jupiter’ transiting a rapidly-rotating star discovered

More information: KELT-20b: A giant planet with a period
of P~ 3.5 days transiting the V~ 7.6 early A star HD 185603,
arXiv:1707.01518 [astro-ph.EP] arxiv.org/abs/1707.01518

© 2017 Phys.org

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