748 Simeïsa (prov. designation:A913 ELor1913 RD) is a very large Hilda asteroid from the outermost regions of the asteroid belt, approximately 104 kilometers (65 miles) in diameter. It was discovered on 14 March 1913, by Russian astronomer Grigory Neujmin at the Simeiz Observatory on the Crimean peninsula.[1] The dark P-type asteroid has a rotation period of 11.9 hours and a shape that is reminiscent of a tetrahedron. It was the first asteroid discovery made in Russia and named after the discovering observatory and its nearby Crimean town, Simeiz.[2]
In October 2011, a rotational lightcurveofSimeïsa was obtained from photometric observations by French amateur astronomer René Roy. Lightcurve analysis gave a rotation period of (11.919±0.002) hours with a brightness variation of (0.36±0.03) magnitude (U=2).[9] In the 1990s, Mats Dahlgren already determined a period of 11.88 hours with an amplitude of 0.22 magnitude (U=2).[13]
According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), and the Japanese Akari satellite, Simeïsa measures (102.97±2.2), (103.725±1.034) and (111.75±2.31) kilometers in diameter and its surface has a low albedo of (0.0415±0.002), (0.041±0.007) and (0.035±0.002), respectively.[5][6][7][8]
The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.0376 and derives a diameter of 102.79 kilometers based on an absolute magnitude of 9.12.[4] Alternative mean diameter measurements published by the WISE team include (103.714±1.128 km) and (109.069±38.907 km) with corresponding albedos of (0.041±0.007) and (0.045±0.027).[4][12]
Two asteroid occultations on 4 March 1999 and 7 January 2006, gave a best-fit ellipse dimension of (106.0 km × 106.0 km) and (109.7 km × 93.2 km), respectively, each with a quality rating of 2.[12] These timed observations are taken when the asteroid passes in front of a distant star.[12]
^ abcdUsui, Fumihiko; Kuroda, Daisuke; Müller, Thomas G.; Hasegawa, Sunao; Ishiguro, Masateru; Ootsubo, Takafumi; et al. (October 2011). "Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey". Publications of the Astronomical Society of Japan. 63 (5): 1117–1138. Bibcode:2011PASJ...63.1117U. doi:10.1093/pasj/63.5.1117. (online, AcuA catalog p. 153)
^Dahlgren, M.; Lahulla, J. F.; Lagerkvist, C. -I.; Lagerros, J.; Mottola, S.; Erikson, A.; et al. (June 1998). "A Study of Hilda Asteroids. V. Lightcurves of 47 Hilda Asteroids". Icarus. 133 (2): 247–285. Bibcode:1998Icar..133..247D. doi:10.1006/icar.1998.5919. ISSN0019-1035.
