10258 Sárneczky

10258 Sárneczky, provisional designation 1940 AB, is a background asteroid from the outer regions of the asteroid belt, approximately 14 kilometers in diameter. It was discovered on 6 January 1940, by Hungarian astronomer György Kulin at the Konkoly Observatory, near Budapest. The asteroid was named after Hungarian astronomer Krisztián Sárneczky.

Orbit and classification
Sárneczky is non-family asteroid from the main-belt's background population. It orbits the Sun in the outer asteroid belt at a distance of 2.9–3.5 AU once every 5 years and 7 months (2,053 days). Its orbit has an eccentricity of 0.09 and an inclination of 14° with respect to the ecliptic. The body's observation arc begins with its official discovery observation at Konkoly in 1940.

Diameter and albedo
According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Sárneczky measures 14.275 kilometers in diameter and its surface has an albedo of 0.151. The asteroid has an absolute magnitude of 12.1.

Rotation period
As of 2017, no rotational lightcurve of Sárneczky has been obtained from photometric observations. The body's rotation period, shape and poles remain unknown.

Naming
This minor planet was named after Krisztián Sárneczky (born 1974), a Hungarian amateur astronomer and discoverer of minor planets and supernovae. He is a board member of the Hungarian Astronomical Association (HAA). The official naming citation was published by the Minor Planet Center on 5 October 2017 (M.P.C. 106499).