Stellar occultations by 2002 MS4 preliminary results

Stellar occultations by 2002 MS4: preliminary results

MSc. Flavia L. Rommelflaviarommel@on.br

(307261) 2002 MS4

Flavia L. Rommel (flaviarommel@on.br)

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● Discovered by the Near-Earth Asteroid (NEAT) program on 18 June 2002;

● Hot classical TNO (Gladman et al. 2008);● Dwarf planet candidate (Vilenius et al.

2012):○ R = 467 ± 23.5 km;○ 𝜌v = 0.051;○ Hv = 4.0 mag;

● Rotation (Thirouin, A. 2013): ○ P = 7.33 h or 10.44 h;○ Amplitude = 0.05 ± 0.01 mag;

Reproduced from Thirouin, A. 2013.

Stellar occultations by 2002 MS4

Flavia L. Rommel (flaviarommel@on.br)

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● 09/07/2019 -------> Double-chord (South America); ● 26/07/2019 -------> Triple-chord (South America);● 26/07/2019 -------> Single-chord (North America);● 19/08/2019 -------> Double-chord (North America);● 26/07/2020 -------> Double-chord (South Africa);● 08/08/2020 -------> Multichord (Europe, North Africa, and Western Asia);● 24/02/2021 -------> Double-chord (South America).

Stellar occultations by 2002 MS4

Flavia L. Rommel (flaviarommel@on.br)

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● 09/07/2019 -------> Double-chord (South America); ● 26/07/2019 -------> Triple-chord (South America);● 26/07/2019 -------> Single-chord (North America);● 19/08/2019 -------> Double-chord (North America);● 26/07/2020 -------> Double-chord (South Africa);● 08/08/2020 -------> Multichord (Europe, North Africa, and Western Asia);● 24/02/2021 -------> Double-chord (South America).

8 August 2020 Prediction and campaign

Flavia L. Rommel (flaviarommel@on.br)

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mag drop = 5.7max. duration = 38 s

8 August 2020 - 116 telescopes

Flavia L. Rommel (flaviarommel@on.br)

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Flavia L. Rommel (flaviarommel@on.br)

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● 61 positives● 40 negatives● 15 bad weather● No secondary events

detected;

Projected chords

Flavia L. Rommel (flaviarommel@on.br)

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● Light curve from Varages - France;

● by Jean Lecacheux● WATEC 910HX;● GPS;● EXP: 0.32 s;● 0.5 m telescope;

Detected topography (~25 km)

Flavia L. Rommel (flaviarommel@on.br)

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Ellipse search

● a’ = 413.7 ± 9.6 km;● 𝜖’ = 0.067 ± 0.033;● Requiv = 399.6 ± 11.7 km;

Diameter about 130 km smaller than the results from thermal data.

Flavia L. Rommel (flaviarommel@on.br)

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Ellipse search

● a’ = 413.7 ± 9.6 km;● 𝜖’ = 0.067 ± 0.033;● Requiv = 399.6 ± 11.7 km;

Diameter about 130 km smaller than the results from thermal data.

Topography

Flavia L. Rommel (flaviarommel@on.br)

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Topography studies from literature

● Pluto system (Moore et al. 2016; Nimmo et al. 2017);

Flavia L. Rommel (flaviarommel@on.br)

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Topography studies from literature

● Pluto system (Moore et al. 2016; Nimmo et al. 2017);

● Arrokoth (Spencer et al. 2020);

Flavia L. Rommel (flaviarommel@on.br)

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Topography studies from literature

● Pluto system (Moore et al. 2016; Nimmo et al. 2017);

● Arrokoth (Spencer et al. 2020);● Uranus’ satellites (Schenk &

Moore, 2020);

Oberon

Flavia L. Rommel (flaviarommel@on.br)

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Topography supported on surface

Assuming:

● Mainly composed by Ice with strength = 0.0303×109 Dyn/cm2;

● ρ = 1.0−2.0 g/cm3;● Procedure from the paper;● Theoretical lower limit is 6-7 km;● Can support 20 km structures;

Flavia L. Rommel (flaviarommel@on.br)

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7 km lower limit

Flavia L. Rommel (flaviarommel@on.br)

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Most successful campaign of a stellar occultation by a TNO.

Topography

Flavia L. Rommel (flaviarommel@on.br)

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Other 6 occultations

Same ellipse parameters:

● Positives (blue) + uncertainties (red);

● Close negative (orange);● Best fit (black ellipse);● 1σ solutions (grey);● Center (black dot).

Flavia L. Rommel (flaviarommel@on.br)

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● Paper is being written with this results;● Future works involve:

○ Photometric observations to derive rotational light curve;○ Imaging differencing analysis;○ Scan stellar occultation light curves to determine upper limits for the presence

of surrounding material or atmosphere.

Final considerations

Flavia L. Rommel (flaviarommel@on.br)

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Thank you for your attention and collaboration!