Size, shape, density, and atmospheric limit of (50000) Quaoar revealed from 14 years of stellar occultation

@article{margoti2026size,
  title = {{Size, shape, density, and atmospheric limit of (50000) Quaoar revealed from 14 years of stellar occultation}},
  author = {Giuliano Margoti and Felipe Braga-Ribas and José Luis Ortiz and Bruno Sicardy and Josselin Desmars and B. Morgado and Eros de Oliveira Gradovski and Chrystian Luciano Pereira and Pablo Santos-Sanz and Altair Ramos Gomes-Júnior and Julio Ignacio Bueno de Camargo and Marcelo Assafin and Vieira-Martins Roberto and Yucel Kilic and Damya Souami and René Duffard and Gustavo Benedetti-Rossi and Tiago Pinheiro and Maísa Poiani and Eduardo Rondón and Marcelo Emilio and Dave Herald and Rafael Sfair and Nicolas Morales and Francois Colas and Frédéric Vachier and Mónica Vara Lubiano and Rodrigo Boufleur and Mert Acar and Francisco Aceituno and Miguel Alarcon and Sinan Alis and Sergio Alonso and Javier Alonso-Santiago and Flavia Amadio and Laerte Andrade and Pascal André and Jonatã Arcas-Silva and Alper Ateş and David Lafuente Aznar and Michael Backes and Mehmed Naim Bagiran and Nelson Balcar and M. Barry and Khalid Barkaoui and Wolfgang Beisker and Kirk Bender and Zouhair Benkhaldoun and Svetlana Boeva and Eberhard Bredner and Richard Busuttil and Oscar Canales and Javier Zaragoza-Cardiel and V. Casanova and Matheus Leal Castanheira and Peter Ceravolo and Steven Conard and Luciano Negrello Correa and Daniel Cotton and V. Dhillon},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = oct,
  doi = {10.3847/1538-4357/ae907e},
  url = {https://hal.science/hal-05790199v1},
  note = {CC BY 4.0},
}

TY  - JOUR
TI  - Size, shape, density, and atmospheric limit of (50000) Quaoar revealed from 14 years of stellar occultation
AU  - Giuliano Margoti
AU  - Felipe Braga-Ribas
AU  - José Luis Ortiz
AU  - Bruno Sicardy
AU  - Josselin Desmars
AU  - B. Morgado
AU  - Eros de Oliveira Gradovski
AU  - Chrystian Luciano Pereira
AU  - Pablo Santos-Sanz
AU  - Altair Ramos Gomes-Júnior
AU  - Julio Ignacio Bueno de Camargo
AU  - Marcelo Assafin
AU  - Vieira-Martins Roberto
AU  - Yucel Kilic
AU  - Damya Souami
AU  - René Duffard
AU  - Gustavo Benedetti-Rossi
AU  - Tiago Pinheiro
AU  - Maísa Poiani
AU  - Eduardo Rondón
AU  - Marcelo Emilio
AU  - Dave Herald
AU  - Rafael Sfair
AU  - Nicolas Morales
AU  - Francois Colas
AU  - Frédéric Vachier
AU  - Mónica Vara Lubiano
AU  - Rodrigo Boufleur
AU  - Mert Acar
AU  - Francisco Aceituno
AU  - Miguel Alarcon
AU  - Sinan Alis
AU  - Sergio Alonso
AU  - Javier Alonso-Santiago
AU  - Flavia Amadio
AU  - Laerte Andrade
AU  - Pascal André
AU  - Jonatã Arcas-Silva
AU  - Alper Ateş
AU  - David Lafuente Aznar
AU  - Michael Backes
AU  - Mehmed Naim Bagiran
AU  - Nelson Balcar
AU  - M. Barry
AU  - Khalid Barkaoui
AU  - Wolfgang Beisker
AU  - Kirk Bender
AU  - Zouhair Benkhaldoun
AU  - Svetlana Boeva
AU  - Eberhard Bredner
AU  - Richard Busuttil
AU  - Oscar Canales
AU  - Javier Zaragoza-Cardiel
AU  - V. Casanova
AU  - Matheus Leal Castanheira
AU  - Peter Ceravolo
AU  - Steven Conard
AU  - Luciano Negrello Correa
AU  - Daniel Cotton
AU  - V. Dhillon
PY  - 2026
DA  - 2026/10/14
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/ae907e
UR  - https://hal.science/hal-05790199v1
AB  - We present results from 28 stellar occultations by the large Trans-Neptunian Object (50000) Quaoar registered between 2018 and 2025. By performing a joint analysis of this occultation data-set, along with other 9 published events, we were able to fit an oblate ellipsoid shape, with equatorial semi-axes, a and b of 566.1+2.5-2.2 km, and a polar semi-axis, c, of 511.2+3.6-3.7 km. It provides an equivalent volumetric diameter of 1094.4 +/- 4.6 km and polar oblateness of 0.097 +/- 0.011. Considering an absolute magnitude of H = 2.79 +/- 0.35, we derive a geometric albedo of pV = 0.125 +/- 0.038. We have derived new upper limits to the surface pressure of a CH4 atmosphere of 0.15 nbar (1-sigma) and 0.65 nbar (3-sigma). We also provide a table with the 36 new astrometric positions for Quaoar. Using the new system mass derived from Weywot's orbit around Quaoar, we calculated a density of 1.760 +/- 0.109 g/cm3. Moreover, from the derived size and rotation period (8.8394 +/- 0.0002 hours (Ortiz et al. 2003)), we calculate that, if Quaoar is in Maclaurin hydrostatic equilibrium state, it would have a density of 1.859 +/- 0.200 g/cm3. This result, within the error bars, is compatible with the value we found. Therefore, this work shows that Quaoar can be a Maclaurin object, being eligible as a dwarf planet.
SN  - 0004-637X
SN  - 1538-4357
ER  -