An international team of astronomers reports the detection of a new planetary system by observing a nearby star known as HD 18599 (or TOI-179). This star appears to orbit a Neptune-mass exoplanet and a massive substellar object. The discovery was detailed in an article published on October 14 on the arXiv preprint server.
TESS is surveying around 200,000 of the brightest stars near the sun in an effort to search for transiting exoplanets. So far, it has identified nearly 6,000 candidate exoplanets (TESS Objects of Interest, or TOI), of which 266 have been confirmed so far.
Now, a group of astronomers led by Silvano Desidera of the Padova Astronomical Observatory, has recently confirmed another TOI monitored by TESS. They report that a transit signal has been identified in the light curve of a bright K dwarf star – TOI-179 (other designations HD 18599 and HIP 13754). The planetary nature of this signal was confirmed by follow-up observations using the HARPS (High Accuracy Radial Velocity Planet Searcher) and SPHERE (Spectro-Polarimetric High-contrast Exoplanet REsearch) instruments.
“As part of ongoing efforts to validate and characterize young transiting exoplanets identified by TESS, we present in this paper our analysis for the system observed around the star HD 18599 = HIP 13754, a bright K (V=8 .99 mag) and dwarf active, also known as the TESS Object of Interest (TOI)-179,” the researchers wrote in the paper.
The new alien world, designated TOI-179 b, is about 2.62 times larger than Earth and 24 times more massive than our planet, resulting in a relatively high average density of about 7.4 g/cm3. The exoplanet orbits its host every 4.14 days, at a distance of 0.048 AU from it, in a substantially eccentric orbit.
Additionally, SPHERE observations have identified another object in the TOI-179 system with an estimated mass of around 83 Jupiter masses, thus on the border between brown dwarfs and very low mass stars. The object received the designation HD 18599 B has a relatively small projected separation from the parent star – about 3.3 AU.
The host star TOI-179 is of spectral type K2V, has a radius of about 0.76 solar radii, while its mass has been measured at 0.83 solar masses. The star is estimated to be around 400 million years old and its effective temperature is at a level of 5,145 K.
Summarizing the findings, the study authors emphasized the uniqueness of the TOI-179 system given the properties of its components.
“The TOI-179 system represents an invaluable laboratory for our understanding of the physical evolution of planets and other low-mass objects and how planet properties are influenced by dynamical effects and interactions with the parent star,” the researchers concluded.
TESS discovers an ancient hot Jupiter-like exoplanet
S. Desidera et al, TOI-179: a young system with a transiting compact planet of mass Neptune and a low-mass companion in outer orbit. arXiv:2210.07933v1 [astro-ph.EP]arxiv.org/abs/2210.07933
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