TY - JOUR
T1 - Defining the Flora Family
T2 - Orbital properties, reflectance properties and age
AU - Dykhuis, Melissa J.
AU - Molnar, Lawrence
AU - Van Kooten, Samuel J.
AU - Greenberg, Richard
N1 - Funding Information:
The authors acknowledge the use of data from the Sloan Digital Sky Survey, and thank the Sloan team and its sponsors (see http://www.sdss.org ). In addition, this publication makes use of data products from the Wide-field Infrared Survey Explorer and NEOWISE, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration.
Funding Information:
MJD was supported in part by an NSF Graduate Research Fellowship , Award No. DGE-1143953 . SJV was supported by a Michigan Space Grant Consortium undergraduate fellowship and the Calvin College Integrated Science Research Institute.
Publisher Copyright:
© 2014 Elsevier Inc.
PY - 2014/11/5
Y1 - 2014/11/5
N2 - The Flora family resides in the densely populated inner main belt, bounded in semimajor axis by the ν6 secular resonance and the Jupiter 3:1 mean motion resonance. The presence of several large families that overlap dynamically with the Floras (e.g., the Vesta, Baptistina, and Nysa-Polana families), and the removal of a significant fraction of Floras via the nearby ν6 resonance complicates the Flora family's distinction in both proper orbital elements and reflectance properties. Here we use orbital information from the Asteroids Dynamic Site (AstDyS), color information from the Sloan Digital Sky Survey (SDSS), and albedo information from the Wide-field Infrared Survey Explorer (WISE) to obtain the median orbital and reflectance properties of the Floras by sampling the core of the family in multidimensional phase space. We find the median Flora SDSS colors to be a*=0.126±0.007 and i-z=-0.037±0.007; the median Flora albedo is pV=0.291±0.012. These properties allow us to define ranges for the Flora family in orbital and reflectance properties, as required for a detailed dynamical study. We use the young Karin family, for which we have an age determined via direct backward integration of members' orbits, to calibrate the Yarkovsky drift rates for the Flora family without having to estimate the Floras' material properties. The size-dependent dispersion of the Flora members in semimajor axis (the "V" plot) then yields an age for the family of 950-170+200My, with the uncertainty dominated by the uncertainty in the material properties of the family members (e.g., density and surface thermal properties). We discuss the effects on our age estimate of two independent processes that both introduce obliquity variations among the family members on short (My) timescales: (1) the capture of Flora members in spin-orbit resonance, and (2) YORP-driven obliquity variation through YORP cycles. Accounting for these effects does not significantly change this age determination.
AB - The Flora family resides in the densely populated inner main belt, bounded in semimajor axis by the ν6 secular resonance and the Jupiter 3:1 mean motion resonance. The presence of several large families that overlap dynamically with the Floras (e.g., the Vesta, Baptistina, and Nysa-Polana families), and the removal of a significant fraction of Floras via the nearby ν6 resonance complicates the Flora family's distinction in both proper orbital elements and reflectance properties. Here we use orbital information from the Asteroids Dynamic Site (AstDyS), color information from the Sloan Digital Sky Survey (SDSS), and albedo information from the Wide-field Infrared Survey Explorer (WISE) to obtain the median orbital and reflectance properties of the Floras by sampling the core of the family in multidimensional phase space. We find the median Flora SDSS colors to be a*=0.126±0.007 and i-z=-0.037±0.007; the median Flora albedo is pV=0.291±0.012. These properties allow us to define ranges for the Flora family in orbital and reflectance properties, as required for a detailed dynamical study. We use the young Karin family, for which we have an age determined via direct backward integration of members' orbits, to calibrate the Yarkovsky drift rates for the Flora family without having to estimate the Floras' material properties. The size-dependent dispersion of the Flora members in semimajor axis (the "V" plot) then yields an age for the family of 950-170+200My, with the uncertainty dominated by the uncertainty in the material properties of the family members (e.g., density and surface thermal properties). We discuss the effects on our age estimate of two independent processes that both introduce obliquity variations among the family members on short (My) timescales: (1) the capture of Flora members in spin-orbit resonance, and (2) YORP-driven obliquity variation through YORP cycles. Accounting for these effects does not significantly change this age determination.
KW - Asteroids
KW - Asteroids, dynamics
KW - Resonances, Spin-orbit
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UR - http://www.scopus.com/inward/citedby.url?scp=84908431341&partnerID=8YFLogxK
U2 - 10.1016/j.icarus.2014.09.011
DO - 10.1016/j.icarus.2014.09.011
M3 - Article
AN - SCOPUS:84908431341
SN - 0019-1035
VL - 243
SP - 111
EP - 128
JO - Icarus
JF - Icarus
ER -