DPS – 2012 – Reno/NVDPS – 2012 – Reno/NV

STELLAR OCCULTATIONS BY LARGE TNOS ON 2012: STELLAR OCCULTATIONS BY LARGE TNOS ON 2012: THE FEBRUARY 3THE FEBRUARY 3RDRD BY (208996) BY (208996) 2003 AZ842003 AZ84, AND , AND

THE FEBRUARY 17THE FEBRUARY 17THTH BY (50000) BY (50000) QUAOARQUAOAR. .

Felipe Braga-Ribas1,3, B. Sicardy1, J. L. Ortiz2, R. Duffard2, J. I. B. Camargo3, J. Lecacheux1, F. Colas4, F. Vachier4, P. Tanga5, S. Sposetti6, N. Brosch7, S. Kaspi7, I. Manulis8, T. Baug9, T. Chandrasekhar9, S. Ganesh9, J. Jain9, V. Mohan10, A. Sharma11, R. Garcia-Lozano12, A. Klotz13, E. Frappa14, E. Jehin15, M. Assafin16, R. Vieira-Martins3, R. Behrend17, F. Roques1, T. Widemann1, N. Morales2, A. Thirouin2, P. Mahasena18, Z. Benkhaldoun19, A. Daassou19, C. Rinner20, E. O. Ofek8, A. Gal-Yam's8

1-Observatoire de Paris-Meudon / LESIA, France, 2-Instituto de Astrofísica de Andalucía, CSIC, Spain, 3-Observatório Nacional / MCTI, Brazil, 4-Observatoire de Paris- Meudon / IMCCE, France, 5-Observatoire de la Côte d'Azur, France, 6-Gnosca Observatory, Switzerland, 7-Wise Observatory, Tel Aviv University, Israel, 8-Weizmann Institute of Science, Israel, 9-Physical Research Laboratory, India, 10-IUCAA Girawali Observatory, India, 11-Nikaya Observatory, India, 12-Observatorio de Busot, Spain, 13-Université de Toulouse, UPS-OMP, IRAP, France, 14-EURASTER, 1bis cours Jovin Bouchard, 42000, France, 15-Institut d’Astrophysique de l’Université de Liège, Belgium, 16-Observatório do Valongo / UFRJ, Brazil, 17-Observatoire de Genève, Switzerland, 18-Observatorium Bosscha, Institut Teknologi Bandung, Indonesia, 19-Oukaimeden Observatory, LPHEA, Cadi Ayyad University, Morocco, 20-Moroccan Oukaimeden Sky Survey, Morocco.

THE FEBRUARY 17THE FEBRUARY 17THTH BY (50000) BY (50000) QUAOARQUAOAR

- Prediction from Prediction from Assafin Assafin et al. 2012*et al. 2012*

- A faint star: R mag A faint star: R mag 15.515.5;;

- Positive detection from Positive detection from 4 sites4 sites: :

Côte D’Azur Obs./ FRCôte D’Azur Obs./ FR

TAROT Grasse/ FRTAROT Grasse/ FR

Valensole/ FRValensole/ FR

Gnosca/ SW.Gnosca/ SW.

- French sites over the same Quaoar’s French sites over the same Quaoar’s latitudelatitude

- in practice we have two chords.in practice we have two chords.

* M. Assafin, et al. Candidate stellar occultations by large TNOs up to 2015, A&A, v. 541, p.A142, 2012.

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Diameter > 1560 km

----------------------------From literature:

Brown & Trujillo 2004Deq = 1260 ± 190 km

Fraser & Brown 2010 Deq= 890 ± 70 km

Fornasier et al.DPS2012 Poster#310.14

Deq= 1036 ± 31km

Braga-Ribas et al.EPSC-DPS 2011

Deq= 1045 – 1095 km

Switzerland

Côte D’Azur Obs./ FR

TAROT Grasse/ FR

Valensole/ FR

ASSUMING CIRCULAR SOLUTION:ASSUMING CIRCULAR SOLUTION:

The circular

solution from

February 2012 is

incompatible with

the observations

from May 2011

occultation.

That means:

Quaoar must be elongated

INCOMPATIBLE WITH THE 2011 OBSERVATIONINCOMPATIBLE WITH THE 2011 OBSERVATION

THE MAY 04THE MAY 04TH TH 20112011 (EPSC-DPS 2011)(EPSC-DPS 2011)

Nominal solution:

all pointsIncluded

Crater solution:

very elongated

Mountain solution:

similar to nominal

Time shifted solution:

equilibrium body.

THE 2012 CHORDS ARE CONSISTENT THE 2012 CHORDS ARE CONSISTENT WITH THE 2011 SOLUTIONSWITH THE 2011 SOLUTIONS

Nominal solution:

all pointsIncluded

Crater solution:

very elongated

Mountain solution:

similar to nominal

Time shifted solution:

equilibrium body.

* Volume of an oblate spheroid. Mass = 1.65 ± 0.16 E21 kg from Vachier et al. 2012F. Vachier, et al. Determination of binary asteroid orbits with a genetic-based algorithm, A&A, v.543, p.A68, 2012.

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MACLAURIN HYDROSTATIC MACLAURIN HYDROSTATIC EQUILIBRIUM BODYEQUILIBRIUM BODY

THE FEBRUARY 3THE FEBRUARY 3RDRD BY (208996) BY (208996) 2003 2003 AZ84AZ84

- Prediction from Prediction from Assafin Assafin et al. 2012et al. 2012

- A faint star: R mag A faint star: R mag 15.115.1;;

- Positive detection from Positive detection from 3 sites3 sites::

Mount Abu Observatory/ IndiaMount Abu Observatory/ India

Weizmann Inst. / IsraelWeizmann Inst. / Israel

IUCAA - Girawali Obs./ IndiaIUCAA - Girawali Obs./ India

- Negative from several sites:Negative from several sites:

- the closest two:the closest two:

- Alicante / SpainAlicante / Spain

- Liverpool Obs. / Spain (Canary)Liverpool Obs. / Spain (Canary)

* M. Assafin, et al. Candidate stellar occultations by large TNOs up to 2015, A&A, v. 541, p.A142, 2012.

THE FEBRUARY 3THE FEBRUARY 3RDRD BY (208996) BY (208996) 2003 2003 AZ84AZ84

THE FEBRUARY 3THE FEBRUARY 3RDRD BY (208996) BY (208996) 2003 2003 AZ84AZ84

Equivalente diameter:686 ± 14 km

Oblateness:0.37 ± 0.1

a = 433km, b= 271km

Geometric albedo:pv= 0.147 ± 0.007*

*using Peixinho et al. 2012 (Hv=3.54 ± 0.05)

Literature:

Stansberry et al. 2008686 ± 95km

Muller et al. 2010

910 ± 60km

Mommert et al. 2012

727 ± 66km

ρ = 0.76 - 0.17+ 0.30

*

* From Thirouin et al. 2010.

MACLAURIN HYDROSTATIC MACLAURIN HYDROSTATIC EQUILIBRIUM BODYEQUILIBRIUM BODY

THE FEBRUARY 3THE FEBRUARY 3RDRD BY (208996) BY (208996) 2003 2003 AZ84AZ84

Summary for the 2003 AZ84 results:Summary for the 2003 AZ84 results:

THE THE OCTOBER 15OCTOBER 15TH TH 2012 BY (50000) 2012 BY (50000) QUAOARQUAOAR

Joe Pollock and Kevin Ivarsen, from Cerro Tololo using PROMPT.

THE TNO OCCULTATION CAMPAIGNS THE TNO OCCULTATION CAMPAIGNS

Nature« in press »