746 Marlu

746 Marlu (prov. designation: A913 EJ or 1913 QY) is a dark and large background asteroid from the outer regions of the asteroid belt, approximately 72 kilometers (45 miles) in diameter. It was discovered on 1 March 1913, by German astronomer Franz Kaiser at the Heidelberg Observatory in southwest Germany.[1] The primitive P-type asteroid has a rotation period of 7.8 hours. It was named after the discoverer's daughter, Marie-Louise Kaiser.[2]

746 Marlu
Modelled shape of Marlu from its lightcurve
Discovery [1]
Discovered byF. Kaiser
Discovery siteHeidelberg Obs.
Discovery date1 March 1913
Designations
(746) Marlu
Named after
Marie-Louise Kaiser
(Discoverer's daughter)[2]
A913 EJ · 1926 WA
1975 XN · 1913 QY
Orbital characteristics [3]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 0
Observation arc104.37 yr (38,122 d)
Aphelion3.8461 AU
Perihelion2.3728 AU
3.1094 AU
Eccentricity0.2369
5.48 yr (2,003 d)
60.352°
0° 10m 47.28s / day
Inclination17.480°
1.9385°
306.79°
Physical characteristics
Dimensions72.0 km × 65.0 km[5]
Mean diameter
  • 69.75±4.0 km[6]
  • 71.55±1.41 km[7]
  • 74.274±1.122 km[8]
7.787 h[9][10]
  • (202.0°, −66.0°) (λ1/β1)[5]
  • (64.0°, −27.0°) (λ2/β2)[5]
  • 0.032±0.007[8]
  • 0.036±0.002[7]
  • 0.0363±0.005[6]

    Orbit and classification

    Marlu is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements.[4][5] It orbits the Sun in the outer asteroid belt at a distance of 2.4–3.8 AU once every 5 years and 6 months (2,003 days; semi-major axis of 3.11 AU). Its orbit has an eccentricity of 0.24 and an inclination of 17° with respect to the ecliptic.[3] The body's observation arc begins at Heidelberg on 12 September 1915, more than two years after its official discovery observation.[1]

    Naming

    Franz Kaiser named this minor planet after his daughter, the physician Marie-Louise Kaiser. The discoverer also named another asteroid, 743 Eugenisis, in honor of his daughter. The naming was mentioned in The Names of the Minor Planets by Paul Herget in 1955 (H 75).[2]

    Physical characteristics

    In the Tholen classification, Marlu is a dark and primitive P-type asteroid,[3] while it is an X-type and P-type asteroid, in the Tholen- and SMASS-like taxonomic variant of the Small Solar System Objects Spectroscopic Survey (S3OS2), respectively.[5][11] P-type asteroids are common in the outer asteroid belt and among the Jupiter trojan population. In the Moving Object Catalog (MOC) of the Sloan Digital Sky Survey, however, Marlu is a common carbonaceous C-type asteroid.[12]

    Rotation period and poles

    In September 1981, a rotational lightcurve of Marlu was obtained from photometric observations by American astronomer Alan W. Harris. Lightcurve analysis gave a rotation period of 7.787 hours with a brightness variation of 0.23 magnitude (U=2).[9] In October 2014, Daniel A. Klinglesmith confirmed the exact same period of (7.787±0.001 h) hours with an amplitude of (0.22±0.01) magnitude (U=3).[10]

    In 2016, a modeled lightcurve gave a concurring sidereal period of 7.78887±0.00005 hours using data from a large collaboration of individual observers. The study also determined two spin axes of (202.0°, −66.0°) and (64.0°, −27.0°) in ecliptic coordinates (λ, β).[5][13][14]

    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 Wide-field Infrared Survey Explorer (WISE), Marlu measures (69.75±4.0), (71.55±1.41) and (74.274±1.122) kilometers in diameter and its surface has a low albedo of 0.0363±0.005), (0.036±0.002) and (0.032±0.007), respectively.[6][7][8]

    The Collaborative Asteroid Lightcurve Link adopts an albedo of 0.0431 and derives a diameter of 69.87 kilometers based on an absolute magnitude of 9.81.[13] The WISE-team also published two alternative mean-diameters of (70.00±19.03 km) and (78.34±21.54 km) with a corresponding albedo of (0.04±0.01) and (0.04±0.05).[5][13] An asteroid occultation on 1 May 1985, gave a best-fit ellipse dimension of (72.0 km × 65.0 km) with an intermediate quality rating of 2.[5] These timed observations are taken when the asteroid passes in front of a distant star.[5]

    References
    1. "746 Marlu (A913 EJ)". Minor Planet Center. Retrieved 8 June 2020.
    2. Schmadel, Lutz D. (2007). "(746) Marlu". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 71. doi:10.1007/978-3-540-29925-7_747. ISBN 978-3-540-00238-3.
    3. "JPL Small-Body Database Browser: 746 Marlu (A913 EJ)" (2020-01-26 last obs.). Jet Propulsion Laboratory. Retrieved 8 June 2020.
    4. "Asteroid 746 Marlu – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 8 June 2020.
    5. "Asteroid 746 Marlu – Nesvorny HCM Asteroid Families V3.0". Small Bodies Data Ferret. Retrieved 8 June 2020.
    6. Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System. 12: IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 8 June 2020.
    7. Usui, 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. Retrieved 8 June 2020. (online, AcuA catalog p. 153)
    8. Mainzer, A. K.; Bauer, J. M.; Cutri, R. M.; Grav, T.; Kramer, E. A.; Masiero, J. R.; et al. (June 2016). "NEOWISE Diameters and Albedos V1.0". NASA Planetary Data System. Bibcode:2016PDSS..247.....M. Retrieved 8 June 2020.
    9. Harris, A. W.; Young, J. W.; Dockweiler, Thor; Gibson, J.; Poutanen, M.; Bowell, E. (January 1992). "Asteroid lightcurve observations from 1981". Icarus. 95 (1): 115–147. Bibcode:1992Icar...95..115H. doi:10.1016/0019-1035(92)90195-D. ISSN 0019-1035.
    10. Klinglesmith, Daniel A.; DeHart, Austin; Hanowell, Jesse; Hendrickx, Sebastian (April 2015). "Asteroids at Etscorn Campus Observatory: 2014 September - December" (PDF). Minor Planet Bulletin. 42 (2): 101–104. Bibcode:2015MPBu...42..101K. ISSN 1052-8091.
    11. Lazzaro, D.; Angeli, C. A.; Carvano, J. M.; Mothé-Diniz, T.; Duffard, R.; Florczak, M. (November 2004). "S3OS2: the visible spectroscopic survey of 820 asteroids" (PDF). Icarus. 172 (1): 179–220. Bibcode:2004Icar..172..179L. doi:10.1016/j.icarus.2004.06.006. Retrieved 8 June 2020.
    12. Carvano, J. M.; Hasselmann, P. H.; Lazzaro, D.; Mothé-Diniz, T. (February 2010). "SDSS-based taxonomic classification and orbital distribution of main belt asteroids". Astronomy and Astrophysics. 510: 12. Bibcode:2010A&A...510A..43C. doi:10.1051/0004-6361/200913322. Retrieved 8 June 2020. (PDS data set)
    13. "LCDB Data for (746) Marlu". Asteroid Lightcurve Database (LCDB). Retrieved 8 June 2020.
    14. Hanus, J.; Durech, J.; Oszkiewicz, D. A.; Behrend, R.; Carry, B.; Delbo, M.; et al. (February 2016). "New and updated convex shape models of asteroids based on optical data from a large collaboration network" (PDF). Astronomy and Astrophysics. 586: 24. arXiv:1510.07422. Bibcode:2016A&A...586A.108H. doi:10.1051/0004-6361/201527441. Retrieved 8 June 2020.
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