Forming Binary Near-Earth Asteroids From Tidal Disruptions

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et al. 2004). The binaries with primaries having D < 5 km were used, however a largeportion of these were EEBs 1 with a mass ratio of unity, where the bound particles wereat the resolution limit of the simulation. Durda et al. (2004) presented results with theseunit-mass-ratio systems removed, considering them more a function of the numerical resolutionrather than actual dynamics. The distribution used in this work also excludesunit-mass-ratio systems, when both components are at the resolution limit.Another difficulty with the MBA binary population is the potential for a very largerange in binary ages, and hence a wide range of tidal evolution end states. Therefore justusing the raw binaries from a collision simulation may represent newly formed binaryMBAs that will not account for any post-collision evolutionary effects. Thus a secondpopulation of binary MBAs is also considered, those with the basic selection effects applied(pericenter distance q > 2.0 a/R pri and semi-major axis a < R Hill , where R Hill isthe Hill sphere), and 100 Myr of tidal evolution while the binaries are migrating into theNEA population (see Fig. 4.4, and Section 4.1.3 for full description of the tidal evolutionformalisms used).Observations are just starting to constrain the binary fraction among the SMBA population,with current work estimating a fraction close to the NEA fraction of ∼ 15%, andproperties similar to the binary NEAs (Harris & Pravec 2006). The survivability duringtransport from a Main Belt orbit to an <strong>Earth</strong>-crossing orbit is unknown as these binariespossibly have to survive multiple perturbations.1 Escaping Ejecta Binaries are binaries formed during a catastrophic collision. As some material isejected from the system entirely, two or more escaping pieces may remain bound to each other. The EEBsdiffer from the binaries formed around the target body as they can be loosely bound small fragments of thecollision, with small sizes that are similarly sized.93
Figure 4.4: The total number of binary MBAs for the (shaded) original distribution and(outline) the distribution with 100 Myr of tidal evolution and single particle pairs removed.The original distribution is from Durda et al. (2004) simulations of a 34 kmdiameter impactor striking a 100 km diameter target at 3 km s −1 at an impact angle of30 ◦ . Shown are the: (a) eccentricity of the binaries; (b) semi-major axis of the binariesin units of the primary radii; (c) inclination; and (d) size ratio.94
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AbstractTitle of Dissertation:Formi
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Forming Binary Near-Earth Asteroids
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PrefaceMuch of the work in this dis
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AcknowledgementsI would not have ma
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2.3 Results and Discussion . . . .
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List of Tables1.1 Binary NEA proper
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4.8 Percentage of migrated binaries
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of the system mass M by way of Kepl
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the largest lightcurve amplitudes o
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1.1.3 Binary Main-Belt asteroidsRec
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Lightcurve discoveriesA lightcurve
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Figure 1.1: (Top) The primary rotat
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1.2.1 CaptureIn this scenario two a
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ever, understanding the mechanism i
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off the equator or off one end of a
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3 Denotes a secure result with no a
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nostic.Recent results have demonstr
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another intermediate source of NEAs
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1.5.2 Rubble pilesThe evidence for
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Chapter 2Formation of Binary Astero
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∼ 60%, making a bulk density of
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shedding mass and distorting prior
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Figure 2.3: Snapshots of a tidal di
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Figure 2.4: Normalized probability
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Figure 2.5: Normalized probability
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Figure 2.6: (a) Satellite eccentric
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various complications of measuring
Page 55 and 56: etween ω pri and L bin ), with clo
Page 57 and 58: prolate-like), the oblate-like bodi
Page 59 and 60: Figure 2.9: Plots comparing T-PROS
Page 61 and 62: Figure 2.10: Comparison of S-class
Page 63 and 64: 2.3.5 Triples and hierarchical syst
Page 65 and 66: a/R pri based on a simple conversio
Page 67 and 68: Figure 2.13: The eccentricity dampi
Page 69 and 70: Main Belt. Work by Chauvineau & Far
Page 71 and 72: (1992), with a target range of slig
Page 73 and 74: The observations were made from the
Page 75 and 76: peaked period, with a lower signifi
Page 77 and 78: and suggests that it is possibly a
Page 79 and 80: fit for the period of the lightcurv
Page 81 and 82: Table 3.2.Orbital, physical and lig
Page 83 and 84: Figure 3.2: Asteroid lightcurves.70
Page 85 and 86: Figure 3.4: Asteroid lightcurves.72
Page 87 and 88: 3.4.4 Spin and shape properties amo
Page 89 and 90: Figure 3.7: The lightcurve amplitud
Page 91 and 92: Typically observations of eclipse o
Page 93 and 94: Chapter 4Steady-State Model of the
Page 95 and 96: values between 0.2-0.6. There is on
Page 97 and 98: asteroids in the Main Belt is suffi
Page 99 and 100: Figure 4.2: Percent of surviving NE
Page 101 and 102: 4.1.3 Binary evolutionBasic stabili
Page 103 and 104: Table 4.1.Lifetimes for binary NEAs
Page 105: which means it should have a critic
Page 109 and 110: the original eccentricity distribut
Page 111 and 112: Figure 4.6: Properties of the binar
Page 113 and 114: Figure 4.8: Binary percentage for m
Page 115 and 116: Figure 4.9: Effects of tidal evolut
Page 117 and 118: quickly altered, or involved in bin
Page 119 and 120: tidal disruption. However, the impl
Page 121 and 122: Chapter 5ConclusionsA general concl
Page 123 and 124: small additions to the angular mome
Page 125 and 126: cently this large pool of observers
Page 127 and 128: differences in results when a lower
Page 129 and 130: Table A.1.Number of binaries produc
Page 131 and 132: Thus the reaccumulated bodies in th
Page 133 and 134: of 2.2 h observed is significantly
Page 135 and 136: Benner, L. A. M., Nolan, M. C., Ost
Page 137 and 138: V7.0:LCREF TAB, 35, 4Harris, A. W.,
Page 139 and 140: Storrs, A. D., Close, L. M., & Mena
Page 141 and 142: 122Pravec, P., Kušnirá, P., Hicks
Page 143 and 144: Shepard, M. K., Schlieder, J., Nola
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Forming Binary Near-Earth Asteroids From Tidal Disruptions

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