Hot Super-Earth Found around Gliese 740
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A team of astronomers from Spain, Italy and Germany has discovered a short-period super-Earth exoplanet circling the nearby red dwarf Gliese 740.

An artist’s impression of the super-Earth planet Gliese 740b and its parent star. Image credit: Sci-News.com.

Gliese 740 is a bright M1-type star located 36.2 light-years away in the constellation of Serpens.

Otherwise known as GJ 740, HD 176029, LHS 470 and TYC 461-366-1, the star is roughly 60% the size and the mass of the Sun.

“Despite the fact that red dwarfs are the most common stars in the Milky Way, 10% of all known planetary companions have been detected around this type of stars,” said Dr. Borja Toledo-Padrón, an astronomer at the Instituto de Astrofísica de Canarias and the Universidad de La Laguna, and colleagues.

“High occurrence rate, combined with their closer habitable zones due to their lower luminosities, makes such low-mass stars ideal targets for the search of temperate Earth-like planets.”

“However, the complexity of the characteristic stellar activity pattern of these stars requires a careful analysis of the chromospheric activity indicators in order to identify false planetary signals induced by the rotation of the star.”

The astronomers detected the new planet, dubbed Gliese 740b, using data from the HADES (HArps-n red Dwarf Exoplanet Survey) program.

“The HADES RV program monitored Gliese 740 from May 26, 2013 to June 16, 2019, using the HARPS-N spectrograph installed at the 3.6-m Telescopio Nazionale Galileo in the Roque de los Muchachos Observatory, Spain,” they explained.

“We also acquired 32 spectra with the CARMENES spectrograph at the Calar Alto Observatory overlapping the epoch during which the HARPS-N observations were carried out.”

“Additionally, this star has been monitored from the southern hemisphere using the HARPS spectrograph installed at the 3.6-m telescope of La Silla Observatory, Chile.”

Gliese 740b is a super-Earth with a minimum mass of 3 Earth masses and a radius of 1.43 Earth radii.

It orbits its host star once every 2.4 days at a distance of only 0.03 AU (astronomical units) and is located out of the habitable zone of its star.

The researchers estimate the planet’s temperature to be about 556 degrees Celsius (1,033 degrees Fahrenheit).

There are also signs of a second, Saturn-mass planet in the Gliese 740 system.

“We studied the possibility of having a second planet causing the 3,400-day signal in the RV time-series since it is not clear that the origin of the signal is related to the presumed activity cycle of the star due to the differences with respect to the results obtained from the activity indicators,” the scientists said.

Their paper will be published in the journal Astronomy & Astrophysics.

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B. Toledo-Padrón et al. 2021. A super-Earth on a close-in orbit around the M1V star GJ 740. A HADES and CARMENES collaboration. A&A, in press; arXiv: 2102.09441

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