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TZ Arietis (also known as Gliese 83.1, GJ 9066, or L 1159-16) is a red dwarf in the northern constellation of Aries. With a normal apparent visual magnitude of 12.3, it is too faint to be seen by the naked eye, although it lies relatively close to the Sun at a distance of 14.6 light-years (4.47 parsecs). It is a flare star, which means it can suddenly increase in brightness for short periods of time.
  TZ Arietis Location of TZ Arietis in the constellation Aries | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aries |
| Right ascension | 02h 00m 12.95632s[1] |
| Declination | +13° 03′ 07.0006″[1] |
| Apparent magnitude (V) | 12.298[2] |
| Characteristics | |
| Spectral type | M4.5 V[3] |
| U−B color index | +1.37[4] |
| B−V color index | +1.80[4] |
| R−I color index | 1.39[3] |
| Variable type | Flare star |
| Astrometry | |
| Radial velocity (Rv) | −28.29±0.25[1] km/s |
| Proper motion (μ) | RA: 1096.458 mas/yr[1] Dec.: -1771.526 mas/yr[1] |
| Parallax (π) | 223.7321 ± 0.0699 mas[1] |
| Distance | 14.578 ± 0.005 ly (4.470 ± 0.001 pc) |
| Absolute magnitude (MV) | 14.03[5] |
| Details | |
| Mass | 0.14[6] M☉ |
| Radius | 0.161[7] R☉ |
| Luminosity | 0.00135[8] L☉ |
| Surface gravity (log g) | 5.05[6] cgs |
| Temperature | 3,158[7] K |
| Metallicity [Fe/H] | −0.14[7] dex |
| Rotational velocity (v sin i) | 3.8[8] km/s |
| Age | 4.8[6] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
TZ Arietis is a variable star. It is a flare star, showing brief increases in brightness due to eruptions from its surface. In the ultraviolet, flares of over a magnitude have been observed. In addition it shows longterm variations in brightness which may be due to starspots and rotation, possibly classifying it as a BY Draconis variable.[10] It was given the variable star designation TZ Arietis in 1970.[11]
In a preprint submitted to arXiv in June 2019, three candidate planets were reported in orbit around this star (GJ 83.1) with orbital periods of 2, 240, and 770 days.[12] A paper published in August 2020 reported a confirmation of the 240-day and 770-day planets, designating them "b" and "c", respectively.[13]
In March 2022, astronomers using the Calar Alto Observatory in Spain, as part of the CARMENES survey project, reported an independent confirmation of the 770-day planet, which they designated "b". However, they found no evidence for the 240-day planet, and confidently defined the 2-day candidate as nothing more than a spurious chromatic effect of the star, linked to its rotation.[14] The NASA Exoplanet Archive still refers to the confirmed, 770-day planet as "c".[15]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b[note 1] | ≥0.21±0.02 MJ | 0.88±0.02 | 771.36+1.34 −1.23 |
0.46±0.04 | — | — |
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