Inversion Model Summary of Asteroidal Occultations Historical Model

Inversion Model Summary of Asteroidal Occultations Historical Model Fits Multi - Model Fits Multi-Year Model Fits Brad Timerson, IOTA Annual Meeting October, 2015

Historical Model Fits Do present modeling techniques fit old events? Multi - Model Fits Does one model fit better than another? Multi-Year Model Fits How do models fit the same asteroid over time?

Introduction to Inversion Models “The knowledge of basic physical characteristics of asteroids – the spin rate, the spin axis orientation, the shape, the size, the mass, the spectral type, etc. – is important for understanding the history and the current state of the asteroid population. Apart from a few asteroids directly imaged by spacecraft, our knowledge about asteroid physical properties is based on remote sensing techniques. And from all these techniques, time-resolved photometry is by far the most important source of information because it is in principle available for all known asteroids. The lightcurve inversion method developed by Kaasalainen & Torppa (2001) and Kaasalainen et al. (2001) is a powerful tool for deriving asteroid shapes and spins from their lightcurves observed over several apparitions. So far, the lightcurve inversion method has led to models of about one hundred asteroids. The models have been published in several papers (Kaasalainen et al. 2002 b, 2004; Torppa et al. 2003; Durech et al. 2009, for example). “ “Most DAMIT models were derived from photometric data by the lightcurve inversion method. Some of them have been further refined or scaled using adaptive optics images, infrared observations, or occultation data. ” (J. Durech, V. Sidorin, and M. Kaasalainen, 2010)

Historical Model Fits Do present modeling techniques fit old events? Inversion Model fits – 1979 to present

11 December 1979 – 3 Juno

29 May 1983 – 2 Pallas

21 January 1991 – 230 Athamantis

10 December 1993 – 85 Io

21 March 1998 – 39 Laetitia

2 July 1999 – 41 Daphne

10 February 2004 – 34 Circe

12 December 2004 – 85 Io

13 August 2005 – 89 Julia

17 May 2005 – 54 Alexandra

10 January 2007 – 44 Nysa

14 January 2007 – 26 Freia

18 February 2007 – 55 Pandora

6 June 2008 – 5 Astraea

4 June 2010 – 80 Sappho

21 August 2010 – 16 Psyche

26 January 2011 – 11 Parthenope

9 March 2011 – 72 Feronia

22 April 2011 – 17 Thetis

Multi - Model Fits For those asteroids having more than one model, does one model fit better than another?

29 October 2004 – 8 Flora – Model 1

29 October 2004 – 8 Flora – Model 2

12 June 2006 – 2 Pallas – Model 1

12 June 2006 – 2 Pallas – Model 2

22 January 2008 – 13 Egeria – Model 1

22 January 2008 – 13 Egeria – Model 2

Multi-Year Model Fits How do models fit the same asteroid over time?

13 April 2007 – 19 Fortuna

18 June 2008 – 19 Fortuna – 1 year later

3 October 2006 – 25 Phocaea

16 April 2012 – 25 Phocaea – 5+ years later

9 March 2008 – 45 Eugenia

13 June 2014 – 45 Eugenia – 6+ years later

7 September 2001 – 9 Metis (5 events)

12 September 2008 – 9 Metis – 7 years later – Model 1

12 September 2008 – 9 Metis – 7 years later – Model 2

29 December 2008 – 9 Metis – 7 years later

7 March 2014 – 9 Metis – 12. 5 years later

7 October 1981 – 88 Thisbe (2 events)

21 February 2007 – 88 Thisbe – 25+ years later

22 November 1982 – 93 Minerva (3 events)

24 December 2010 – 93 Minerva – 28 years later

6 September 2014 – 93 Minerva – 32 years later

References “DAMIT: a database of asteroid models” J. Durech , V. Sidorin, and M. Kaasalainen, 2010 http: //astro. troja. mff. cuni. cz/projects/asteroids 3 D/download/durech_et_at_damit_preprint. pdf Webpage http: //astro. troja. mff. cuni. cz/projects/asteroids 3 D/web. php

Comments? Questions?