Forming Binary Near-Earth Asteroids From Tidal Disruptions

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4.2.3 Influence of MBA shape/spin propertiesThe two different shape/spin distributions used produced similar results. Using the distributionsderived for SMBA shape and spin from lightcurve data, as in the Nominal case(see section 4.2.1), the steady-state binary fraction for tidal disruption formed binarieswas 1.2% (Table 4.2). This fraction increased slightly when the shape/spin distributionfor NEAs was used, increasing to 1.4%. The faster spinning NEAs generally are more effectiveat producing binaries via tidal disruption, but within this steady-state model wheredisruption by planetary encounters dominated, the overall affect is minimal.4.2.4 Influence of tidal evolution<strong>Tidal</strong> evolution during the simulation strongly change the eccentricity and semi-majoraxes of the binaries (Fig. 4.9). The lifetimes against disruption due to close encountersare greater for closer binaries, and for these binaries the eccentricity damping time-scalesare relatively short. The effects of eccentricity damping is quite noticeable with a strongpeak of nearly half the binaries at 0–0.1 eccentricity with small numbers spread out athigher values. This is vastly different than a simulation with no tidal effects where thebulk of the eccentricity values are greater than 0.1.Similarly the semi-major axis distribution is noticeably increased for the simulationwith tidal effects compared to the one without (Fig. 4.9). The peaks of the distribution arepushed from 3–5 R pri towards 5–8 R pri . This does move some bodies out beyond 10 R pri ,though time scales to move any beyond that are very long, and the lifetime of the binaryagainst disruption will decrease rapidly with increasing a.The overall binary fraction increases slightly from 1.2% to 1.7% (Table 4.2), thoughthe size ratio between the two components is essentially unchanged (Fig. 4.9). Though thetidal effects noticeably affect a and e they are not strong enough to increase a so rapidly101
Figure 4.9: Effects of tidal evolution on the binaries during the nominal steady-statesimulation comparing their properties with tidal evolution (outline, TE on) and with notidal evolution (shaded histogram, TE off): (a) eccentricity; (b) number of binaries; (c)the semi-major axis; and (d) the size ratios.that the lifetimes of binaries decrease dramatically, instead they only slightly lower thebinary fraction. Therefore it is essentially a shift in the basic properties only.102
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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
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etween ω pri and L bin ), with clo
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prolate-like), the oblate-like bodi
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Figure 2.9: Plots comparing T-PROS
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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
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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 and 106: which means it should have a critic
Page 107 and 108: Figure 4.4: The total number of bin
Page 109 and 110: the original eccentricity distribut
Page 111 and 112: Figure 4.6: Properties of the binar
Page 113: Figure 4.8: Binary percentage for m
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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