1212 Francette

1212 Francette (provisional designation 1931 XC) is a dark Hildian asteroid from the outermost regions of the asteroid belt, approximately 82 kilometers in diameter. It was discovered on 3 December 1931, by French astronomer Louis Boyer at the Algiers Observatory in Algeria, North Africa, who named it after his wife Francette Boyer.^[2][12]

1212 Francette

Discovery[1]
Discovered by	L. Boyer
Discovery site	Algiers Obs.
Discovery date	3 December 1931
Designations
MPC designation	(1212) Francette
Named after	Francette Boyer[2] (discoverer's wife)
Alternative designations	1931 XC · 1949 HB1 1949 HZ · 1965 JB A918 KA
Minor planet category	main-belt · (outer)[1] Hilda[3][4]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	85.98 yr (31,406 days)
Aphelion	4.7109 AU
Perihelion	3.1972 AU
Semi-major axis	3.9541 AU
Eccentricity	0.1914
Orbital period (sidereal)	7.86 yr (2,872 days)
Mean anomaly	282.89°
Mean motion	0° 7m 31.44s / day
Inclination	7.5898°
Longitude of ascending node	149.58°
Argument of perihelion	348.23°
Jupiter MOID	0.3433 AU
Physical characteristics
Dimensions	76.395±0.155 km[5] 82.13±3.2 km[6] 85.81±2.18 km[7]
Synodic rotation period	16 h (poor)[8] 22.433±0.007 h[9][a]
Geometric albedo	0.037±0.002[7] 0.0400±0.003[6] 0.040±0.007[10] 0.046±0.007[5]
Spectral type	Tholen = P[1] · P[10] SMASS = X[1][3] B–V = 0.693[1] U–B = 0.215[1]
Absolute magnitude (H)	9.54[1][3][6][7] · 9.62±0.23[11]

Orbit and classification

Francette is the second largest member of the small Hilda family (001),^[4] an asteroid family within the dynamical Hilda group,^[3] that stays in an orbital resonance with the gas giant Jupiter. It orbits the Sun in the outermost asteroid belt at a distance of 3.2–4.7 AU once every 7 years and 10 months (2,872 days; semi-major axis of 3.95 AU). Its orbit has an eccentricity of 0.19 and an inclination of 8° with respect to the ecliptic.^[1]

The asteroid was first observed as A918 KA at Simeiz Observatory in May 1918. The body's observation arc begins at Algiers with its official discovery observation.^[12]

Physical characteristics

In the Tholen classification, Francette is a primitive P-type asteroid.^[1] In the SMASS classification it is an X-type asteroid.^[1][3] The Wide-field Infrared Survey Explorer (WISE) also characterizes Francette as a dark P-type,^[10] while the overall spectral type for members of the Hilda family is typically that of a carbonaceous C-type.^[13]: 23

Rotation period

In July 2016, a rotational lightcurve of Francette was obtained from photometric observations by American astronomers Brian Warner, Robert Stephens and Dan Coley at the Center for Solar System Studies (U80–82) in California. Lightcurve analysis gave a rotation period of 22.433 hours with a brightness variation of 0.13 magnitude (U=2/3-), superseding a period of 16 hours, previously measured in the 1970s.^[8][9][a]

Diameter and albedo

According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite and the NEOWISE mission of NASA's WISE telescope, Francette measures between 76.395 and 85.81 kilometers in diameter and its surface has an albedo between 0.037 and 0.046.^{[5][6][7][10]}

The Collaborative Asteroid Lightcurve Link adopts the results obtained by IRAS, that is, an albedo of 0.0400 and a diameter of 82.13 kilometers based on an absolute magnitude of 9.54.^[3][6]

Naming

This minor planet was named by the discoverer after his wife, Francette Boyer. The official naming citation was mentioned in The Names of the Minor Planets by Paul Herget in 1955 (H 112).^[2]

Notes

1. Lightcurve plot of (1212) Francette by Warner, Stephens and Coley at the CS3 from 5 July to 2 August 2016 rotation period 22.433±0.007 hours and an amplitude of 0.13 mag. Quality code of 3-. Summary figures at the LCDB