07h21m33.1657s, +58° 16′ 05.005″| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Lynx[1] |
| Right ascension | 07h21m 33.1602s[2] |
| Declination | +58° 16′ 05.110″[2] |
| Apparent magnitude (V) | 10.674 ± 0.019[3] |
| Characteristics | |
| Spectral type | F5V[3] |
| Apparent magnitude (B) | 11.240 ± 0.029[3] |
| Apparent magnitude (V) | 10.674 ± 0.019[3] |
| Apparent magnitude (J) | 9.667 ± 0.021[4] |
| Apparent magnitude (H) | 9.476 ± 0.022[4] |
| Apparent magnitude (K) | 9.406 ± 0.023[4] |
| Astrometry | |
| Proper motion (μ) | RA: −17.008(12) mas/yr[2] Dec.: 5.463(12) mas/yr[2] |
| Parallax (π) | 3.7812 ± 0.0156 mas[2] |
| Distance | 863 ± 4 ly (264 ± 1 pc) |
| Details | |
| Mass | 1.32 ± 0.02[3] M☉ |
| Radius | 1.56 ± 0.05[3] R☉ |
| Temperature | 6397 ± 70[3] K |
| Metallicity [Fe/H] | -0.04 ± 0.03[3] dex |
| Age | 2.1 ± 0.6[3] Gyr |
| Other designations | |
Koit, TYC 3793-1994-1, GSC 03793-01994, 2MASS J07213317+5816051[5] | |
| Database references | |
| SIMBAD | data |
XO-4 is a star located approximately 863 light-years away from Earth in the Lynx constellation. It has a magnitude of about 11 and cannot be seen with the naked eye but is visible through a small telescope.[3] A search for a binary companion star using adaptive opticsatMMT Observatory was negative.[6]
The star XO-4 is named Koit. The name was selected in the NameExoWorlds campaign by Estonia, during the 100th anniversary of the IAU. Koit is Estonian for dawn, and was named for a character in a folk tale written by Friedrich Robert Faehlmann.[7][8][9]
One known exoplanet, XO-4b, which is classified as a hot jupiter, orbits XO-4. This exoplanet was discovered in 2008 by the XO Telescope project using the transit method.[3] It has been named Hämarik, meaning dusk, and referring to a character from the same Faehlmann story featuring Koit.[10]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b / Hämarik | 1.72 ± 0.20 MJ | 0.0552 ± 0.0003 | 4.1250823 ± 0.0000039 | 0(assumed) [note 1] | — | — |
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