Issue |
A&A
Volume 643, November 2020
|
|
---|---|---|
Article Number | A125 | |
Number of page(s) | 15 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202038526 | |
Published online | 13 November 2020 |
A multi-chord stellar occultation by the large trans-Neptunian object (174567) Varda★
1
LESIA UMR-8109, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité,
5 place Jules Janssen,
92195
Meudon,
France
e-mail: damya.souami@obspm.fr
2
naXys, University of Namur,
Rempart de la Vierge,
Namur 5000,
Belgium
3
Federal University of Technology – Paraná (UTFPR / DAFIS),
Curitiba, Brazil
4
Observatório Nacional/MCTIC,
Rio de Janeiro, Brazil
5
Laboratório Interinstitucional de e-Astronomia – LineA,
Rua Gal. José Cristino 77,
Rio de Janeiro,
RJ
20921-400, Brazil
6
Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n,
18008
Granada, Spain
7
Institut Polytechnique des Sciences Avancées IPSA,
63 boulevard de Brandebourg,
94200
Ivry-sur-Seine, France
8
IMCCE-CNRS UMR8028, Observatoire de Paris, PSL Université, Sorbonne Université,
77 Av. Denfert-Rochereau,
75014
Paris, France
9
Université de la Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, France
10
International Occultation Timing Association (IOTA), PO Box 7152,
WA
98042,
USA
11
College of Southern Idaho,
Idaho, USA
12
NASA Johnson Space Center Astronomical Society,
Houston,
TX, USA
13
Southwest Research Institute,
1050 Walnut St., Suite 300,
Boulder,
CO
80302, USA
14
University of Colorado,
Boulder,
Colorado, USA
15
Observatório do Valongo/UFRJ,
Rio de Janeiro, Brazil
16
UNESP – São Paulo State University, Grupo de Dinâmica Orbital e Planetologia,
Guaratinguetá,
SP
12516-410, Brazil
17
Tangra Observatory (E24),
St. Clair,
Australia
18
California Polytechnic State University,
San Luis Obispo,
CA, USA
19
Calipatria High School,
Calipatria,
CA, USA
20
Euraster,
1 rue du tonnelier,
46100
Faycelles, France
21
Jimginny Observatory (W08),
Naperville,
IL, USA
22
Universidade Estadual de Ponta Grossa (UEPG),
Ponta Grossa,
Brazil
Received:
28
May
2020
Accepted:
22
July
2020
Context. We present results from the first recorded stellar occultation by the large trans-Neptunian object (174567) Varda that was observed on September 10, 2018. Varda belongs to the high-inclination dynamically excited population, and has a satellite, Ilmarë, which is half the size of Varda.
Aims. We determine the size and albedo of Varda and constrain its 3D shape and density.
Methods. Thirteen different sites in the USA monitored the event, five of which detected an occultation by the main body. A best-fitting ellipse to the occultation chords provides the instantaneous limb of the body, from which the geometric albedo is computed. The size and shape of Varda are evaluated, and its bulk density is constrained using Varda’s mass as is known from previous works.
Results. The best-fitting elliptical limb has semi-major (equatorial) axis of (383 ± 3) km and an apparent oblateness of 0.066 ± 0.047, corresponding to an apparent area-equivalent radius R′equiv = (370±7) km and geometric albedo pv = 0.099 ± 0.002 assuming a visual absolute magnitude HV = 3.81 ± 0.01. Using three possible rotational periods for the body (4.76, 5.91, and 7.87 h), we derive corresponding MacLaurin solutions. Furthermore, given the low-amplitude (0.06 ± 0.01) mag of the single-peaked rotational light-curve for the aforementioned periods, we consider the double periods. For the 5.91 h period (the most probable) and its double (11.82 h), we find bulk densities and true oblateness of ρ = (1.78 ± 0.06) g cm−3, ɛ = 0.235 ± 0.050, and ρ = (1.23 ± 0.04) g cm−3, ɛ = 0.080 ± 0.049. However, it must be noted that the other solutions cannot be excluded just yet.
Key words: methods: observational / occultations / Kuiper belt objects: individual: Varda
Astrometric data of Varda acquired between 2013 and 2019 and used for the prediction as well as the photometric data associated with Fig. 3b are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/643/A125
© D. Souami et al. 2020
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.