Issue |
A&A
Volume 688, August 2024
|
|
---|---|---|
Article Number | L11 | |
Number of page(s) | 8 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/202450288 | |
Published online | 05 August 2024 |
Letter to the Editor
ASASSN-21js: A multi-year transit of a ringed disc
1
Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands
e-mail: kenworthy@strw.leidenuniv.nl
2
Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
Received:
8
April
2024
Accepted:
4
July
2024
Aims. The early-type star ASASSN-21js started to fade in 2021, as was detected by the All Sky Automated Survey for Supernovae, undergoing a multi-year eclipse that is still underway. We interpret this event as being due to a structured disc of material transiting in front of the star. The disc is in orbit around a substellar object with the mass and luminosity of a brown dwarf or smaller. We want to determine the expected duration and ending date of the eclipse.
Methods. We modelled a tilted and inclined azimuthally symmetric ring system around an unseen companion and calculated the resulting time-varying light curve as the object transited in front of the star. We made an initial estimate of the ring parameters and used these as inputs to an MCMC algorithm to determine the geometric properties of the rings with associated uncertainties.
Results. The model most consistent with the light curve to date is a two-ring system at high inclination with respect to the line of sight that has a semi-major axis of 71.6 stellar radii. With an estimate of the stellar radius, the transverse velocity is around 0.7 km s−1, which if bound to the star is an orbit with a semi-major axis of around 13 000 au, placing it in the Oort cloud of the parent star. The transit is ongoing and will finish around MJD 61526 (May 1 2027). We encourage the community to continue observing this object in order to understand its properties.
Key words: Oort Cloud / planets and satellites: formation / planets and satellites: rings
© The Authors 2024
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.
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