3401 Vanphilos, provisional designation 1981 PA, is a stony, eccentric asteroid and sizeable Mars-crosser, approximately 7 kilometers in diameter. It was discovered on 1 August 1981, by and at Harvard's Oak Ridge Observatory (Agassiz Station) in Massachusetts, United States.[3]
Orbit and classification
Vanphilos orbits the Sun in the inner main-belt at a distance of 1.5–3.2 AU once every 3 years and 8 months (1,330 days). Its orbit has an eccentricity of 0.36 and an inclination of 22° with respect to the ecliptic.[1] In 1946, it was first identified as 1946 DA at the Finnish Turku Observatory, extending the body's observation arc by 35 years prior to its official discovery at Harvard.[3]
In February and March 2008, three rotational lightcurves of Vanphilos were obtained from photometric observations by astronomers Petr Pravec, James W. Brinsfield and Robert Stephens. Light-curve analysis gave a well defined rotation period of 4.225 and 4.226 hours, respectively, with a change in brightness between 0.50 and 0.54 magnitude (U=3/3/3).[7][8][a]
In August 2014, astronomer Brian Warner derived a concurring period of 4.227 hours with an amplitude of 0.62 magnitude from his observations taken at the Palmer Divide Station in Colorado (U=3).[9] Light-curve plots were published on-line by the Ondřejov Observatory and the Center for Solar System Studies.[b][c]
Diameter and albedo
According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Vanphilos measures 7.02 and 7.10 kilometers in diameter, and its surface has an albedo of 0.377 and 0.31, respectively.[5][6] The Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 10.30 kilometers, as the lower the body's albedo (reflectivity), the larger its diameter, at a constant absolute magnitude.[4]
Naming
This minor planet was named for Vanessa Hall and Philip Osborne, by astronomer G. V. William to celebrate their marriage on 3 August 1991.[2] The approved naming citation was published by the Minor Planet Center on 25 August 1991 (M.P.C. 18644).[11]