V1298 Tauri is a young (23±4

Myr The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...

) weakly-lined T Tauri star that is part of the Taurus-Auriga association in the Taurus Molecular Cloud. Alternatively it is part of a proposed moving group, called Group 29 that is slightly older. The system has four transiting

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

s, discovered with the

Kepler space telescope The Kepler space telescope is a disused space telescope launched by NASA in 2009 to discover Earth-sized planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched into an Earth-trailing heliocentric orb ...

in the K2 mission. One of the planets was discovered in August 2019 and the other three were discovered in November 2019 by the same team.

Stellar characteristics

V1298 Tauri has a spectral type of K0 - K1.5 and it has a mass of about 1.1 . The star appears in

x-rays An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 Picometre, picometers to 10 Nanometre, nanometers, corresponding to frequency, ...

from ROSAT data and it does show strong

lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid el ...

absorption lines, both signatures of youth and therefore it was a proposed member of Taurus-Auriga. On the other hand it does not show signs of accretion and it lacks infrared excess. Instead it shows H-alpha in absorption. The brightness of V1298 Tauri varies in an unpredictable way between a maximum visual magnitude of 10.31 and a minimum of 10.54. The light curve of the star shows quasi-periodic variability that was interpreted as

stellar rotation Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bulge ...

and starspots. The light curve also showed several

flares A flare, also sometimes called a fusée, fusee, or bengala in some Latin-speaking countries, is a type of pyrotechnic that produces a bright light or intense heat without an explosion. Flares are used for distress signaling, illumination, o ...

. Based on

Gaia DR2 The ''Gaia'' catalogues are star catalogues created using the results obtained by ''Gaia'' space telescope. The catalogues are released in stages that will contain increasing amounts of information; the early releases also miss some stars, especia ...

data this star is part of a co-moving pair, together with HD 284154.

Planetary system

V1298 Tauri has four confirmed planets of which planets c, d and b are near a 1:2:3

resonance Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillatin ...

(with periods of 8.25, 12.40 and 24.14 days). Planet e only shows a single transit in the K2 light curve and has a period larger than 36 days. Planet e might be in a low-order resonance (of 2:3, 3:5, 1:2, or 1:3) with planet b. The system is very young and might be a precursor of a compact multiplanet system. The 2:3 resonance suggests that some close-in planets may either form in resonances or evolve into them on timescales of less than 10 Myr. The planets in the system have a size between Neptune and Saturn. Only planet b has a size similar to Jupiter. Models predict that the planets have a minimum core mass of 5 and are surrounded by a thick envelope that make up 20% of their mass. The total mass of planet c and d was predicted to be 2 - 28 and the total mass of planet d and b was predicted to be 9 - 120 . In a follow-up paper the mass of V1298 Tauri b was constrained to <2.2 . The planet c was suspected to be shedding mass due to intense irradiation by the host star, but hydrogen tail existence was refuted by 2021. Orbits of the planets b and c are nearly coplanar and planet c is not inclined to the equatorial plane of the star, misalignment equals to 2 degrees.

References

{{Stars of Taurus Planetary systems with four confirmed planets Pre-main-sequence stars T Tauri stars K-type stars Taurus (constellation) Irregular variables Tauri, V1298

Stellar characteristics

Planetary system

See also

References