Star in the constellation Lynx
! style="text-align: center; background-color: #FFFFC0;" colspan="2" | Observation dataEpoch J2000      Equinox J2000
! style="text-align:left" | Constellation
! style="text-align:left" | Right ascension
! style="text-align:left" | Declination
! style="text-align:left" | Apparent magnitude (V)
! style="background-color: #FFFFC0; text-align: center;" colspan="2"| Characteristics
! style="text-align:left" | Spectral type
! style="text-align:left" | Apparent magnitude (B)
! style="text-align:left" | Apparent magnitude (V)
! style="text-align:left" | Apparent magnitude (J)
! style="text-align:left" | Apparent magnitude (H)
! style="text-align:left" | Apparent magnitude (K)
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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. A search for a binary companion star using adaptive optics at MMT Observatory was negative.
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.
Planetary system.
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. It has been named Hämarik, meaning "dusk", and referring to a character from the same Faehlmann story featuring Koit.
! align=center| Companion
! align=center| Mass
! align=center| Semimajor axis
! align=center| Orbital period
! align=center| Eccentricity
! align=center| Inclination
! align=center| Radius 
Notes.
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References.
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External links.
 ;indicator name="01-sky-coordinates" ; ;templatestyles src="Template:Sky/styles.css" / ;Coordinates: &amp;de=58.268056944444446&amp;zoom=&amp;show_grid=1&amp;show_constellation_lines=1&amp;show_constellation_boundaries=1&amp;show_const_names=1&amp;show_galaxies=1&amp;img_source=IMG_all 07h 21m 33.1657s, +58° 16′ 05.005″ ;/indicator ;