Forming Binary Near-Earth Asteroids From Tidal Disruptions

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Chapter 3Lightcurve Observations of Small MainBelt <strong>Asteroids</strong>3.1 OverviewWe report the results of an observing campaign to measure the lightcurves of small (D < 5km) Main-Belt asteroids. Shape and spin information from lightcurve data is valuable forinvestigating the processes in the Main-Belt and near-<strong>Earth</strong> regions that affect these propertiesof asteroids. The targets of these observations all had H > 16.5, and were observedfrom the Kitt Peak National Observatory (KPNO) 2.1 m telescope. We have observeda total of 28 objects, constraining amplitudes for all, and periods for 15. We presentthe results of these observations, and compare them to previously known distributions oflightcurve amplitudes and periods for MBAs, small MBAs and NEAs. Previously therewere only 60 published light curves for small MBAs. Overall no significant divergenceis present between the distributions for small MBAs and all MBAs, with small MBAs notappearing to have the abundance of rapidly rotating bodies present among the NEAs.The work presented here is essentially a continuation of the survey by Binzel et al.57
(1992), with a target range of slightly smaller bodies. It is aimed at increasing the numberof bodies with well-known lightcurves, allowing comparison between NEAs, SMBAs,and the population of larger MBAs. In section 3.2 we discuss the details of our observingcampaign. The data reduction techniques are covered in section 3.3 and the results of theobservations along with discussion are in section 3.4.3.2 ObservationsAll observations were made at the KPNO 2.1m on the following dates,1. December 7–9, 20042. March 4–13, 20053. December 27, 2005 – January 3, 20064. February 28, 2006 – March 4, 2006Observations were made in R and V filters, with V used rarely for color measurements(though a surprisingly low number of photometric nights diminished the numberof nights it was used). On non-photometric nights observations were typically only madein the R filter. Exposure time was typically adjusted to achieve a Signal-to-Noise ratioof 50, with most exposures between 30–120 seconds. Coverage time for each object wasadjusted depending on target brightness and airmass throughout the night of observations.Many nights included observations of more than one target, and coverage for each wasdistributed according to initial estimates of any lightcurve period determined from realtimedata reduction. During the course of one exposure the motion of the asteroid, around0.5 arcsec per minute usually, was less than the size of the typical point spread function(PSF). Therefore the asteroids were not tracked during the exposure, instead tracking wasat the sidereal rate.58
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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
Page 19 and 20: 1.1.3 Binary Main-Belt asteroidsRec
Page 21 and 22: Lightcurve discoveriesA lightcurve
Page 23 and 24: Figure 1.1: (Top) The primary rotat
Page 25 and 26: 1.2.1 CaptureIn this scenario two a
Page 27 and 28: ever, understanding the mechanism i
Page 29 and 30: off the equator or off one end of a
Page 31 and 32: 3 Denotes a secure result with no a
Page 33 and 34: nostic.Recent results have demonstr
Page 35 and 36: another intermediate source of NEAs
Page 37 and 38: 1.5.2 Rubble pilesThe evidence for
Page 39 and 40: Chapter 2Formation of Binary Astero
Page 41 and 42: ∼ 60%, making a bulk density of
Page 43 and 44: shedding mass and distorting prior
Page 45 and 46: Figure 2.3: Snapshots of a tidal di
Page 47 and 48: Figure 2.4: Normalized probability
Page 49 and 50: Figure 2.5: Normalized probability
Page 51 and 52: Figure 2.6: (a) Satellite eccentric
Page 53 and 54: 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: Main Belt. Work by Chauvineau & Far
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 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 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
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Chapter 5ConclusionsA general concl
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small additions to the angular mome
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cently this large pool of observers
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differences in results when a lower
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Table A.1.Number of binaries produc
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Thus the reaccumulated bodies in th
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of 2.2 h observed is significantly
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Benner, L. A. M., Nolan, M. C., Ost
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V7.0:LCREF TAB, 35, 4Harris, A. W.,
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Storrs, A. D., Close, L. M., & Mena
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122Pravec, P., Kušnirá, P., Hicks
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Shepard, M. K., Schlieder, J., Nola
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Forming Binary Near-Earth Asteroids From Tidal Disruptions

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