Astronomers discover a new ‘hot Jupiter’ on an eccentric and misaligned orbit

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TESS SPOC PDC SAP light curves and ground transits of TOI-1859 b. TOI-1859 b transits are labeled blue on the TESS light curves in the two left panels. The median of the fitted transit model is plotted in blue on the two right panels. Two ground transits are shown in the lower right panel. Credit: Dong et al, 2023

Using NASA’s Transiting Exoplanet Survey Satellite (TESS), astronomers have discovered a new “hot Jupiter” exoplanet. The new alien world, designated TOI-1859 b, orbits its parent star in an eccentric, misaligned orbit. The discovery is reported in an article published May 25 in the arXiv prepress server.

The TESS spacecraft is conducting a survey of around 200,000 of the brightest stars near the sun with the aim of looking for transiting exoplanets. So far, it has identified nearly 6,600 exoplanet candidates (TESS Objects of Interest, or TOI), of which 333 have been confirmed so far.

Now, a team of astronomers led by Jiayin Dong of Pennsylvania State University (PSU) reports another confirmed TOI. According to the recently published paper, a transit signal has been identified in the light curve of an end-F dwarf star known as TOI-1859 (other designation TIC-229742722). The planetary nature of this signal was confirmed by subsequent ground-based observations.

“As a Continuous Observing Zone target, TOI-1859 was observed in more than 20 TESS sectors over four years. The TESS Cycle 2 observations from sectors 1420 and 2226 (UT 2019-July 18 to UT 2020- Jul-04) led to the initial detection of planetary transit signals,” the researchers wrote in the paper.

The newly detected planet TOI-1859 b has a radius of about 0.86 Jupiter radii and orbits its host every 63.48 days, at a distance of about 0.33 AU from it. Given that the parent star has an effective temperature of about 6,341 K, TOI-1859 b’s size and distance from the star suggest that it is a “hot Jupiter”.

Observations found that the stellar obliquity projected across the sky for TOI-1859 b is at a level of 38.9 degrees, and the orbital eccentricity is approximately 0.57. Astronomers speculate that such an eccentric and misaligned orbit of TOI-1859 b is likely due to dynamic interactions, such as planet-planet scattering and planet-disc resonance crossings.

The authors of the article propose further investigations of the TOI-1859 system to verify the origin of the planet’s peculiar orbit. They suggest that long-term follow-up radial velocity measurements are needed to detect any other planetary/brown dwarf candidates and constrain their masses and orbit.

Additionally, the researchers noted that more studies of hot Jupiters like TOI-1859 b are needed to see whether or not a star’s effective temperature affects orbital alignment.

“Detecting and characterizing hotter Jupiterian systems like TOI-1859b around hot and cold stars will fill the parameter space and reveal any possible trends between the host star’s effective temperature and stellar obliquity in hot Jupiterian systems,” the scientists concluded. .

When it comes to the properties of the host star, observations show that it is a metal-rich F dwarf about 30% larger and more massive than the sun.

More information:
Jiayin Dong et al, TOI-1859b: 64-day hot Jupiter on an eccentric and misaligned orbit, arXiv (2023). DOI: 10.48550/arxiv.2305.16495

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