Campaign plan
* required items
1. Name of Campeign *[ Mysterious circumplanetary environment of trans-Neptunian objects revealed bystellar occultation ]2．Principal Investigator[ Ko Arimatsu (Kyoto University) ]*3. Phenomena *2023-09-30 27:38 JST
Gaia DR3: 12460425975997824 (Gaia RP mag = 11.1) occulted by 2004UX10
2023-10-24 22:01 JST
Gaia DR3: 6897437174926043008 (Gaia RP mag = 15.5) occulted by 2015MQ204
2023-11-09 26:41 JST
Gaia DR3: 941676497387966208 (Gaia RP mag = 12.8) occulted by 2002XW93
2023-12-20 24:15 JST
Gaia DR3: 224719633892722688 (Gaia RP mag = 14.1) occulted by 1995SM55
4. Importance of observation *We propose to monitor stellar occultations of several 100 km-sized trans-Neptunianobjects (TNOs) to search for their circumplanetary ring(s).
These rings (e.g., Braga-Ribas et al. 2014, Nature, 508, 72) are thought to beubiquitous around larger TNOs (with diameters of approximately > several 100 km) andrepresent the formation and dynamical evolution history of the outer Solar System, as
well as the physical properties of TNO bodies.
However, for most TNOs occultation observations with sufficient photometric accuracy toprobe for the rings have never been made.
We propose observations of 4 occultation events by the known 100 km sized TNOs
(2004UX10, 2015MQ204, 2002XW93, and 1995SM55),
which have never been studied in detail.
5. Occult area [Japan] *6. Special note regarding party scale
Since the uncertainties of the occultation is larger (~ 1000 km or larger in projecteddistances),
we request observation positions should be distributed as much as possible.
7. Special note regarding observation
Since the Hill radius of a 100-km sized TNO with a typical comet nucleus volume densityof about 0.5 g cm-3 in the Kuiper Belt region is about 10^5 km, so we will search forpossible flux drops by rings within about 1/10 of the Hill radius (~ 10^4 km) where
they can stably exist.
For this purpose, we plan to conduct continuous photometric observations for about 10
minutes before and after the expected occultation time.
In this campaign, we plan to obtain occultation of possible ring(s) and planet bodywith corresponding spatial resolutions smaller than ~30 km (required, corresponds tohalf width of the Haumea's ring) or ~3 km (optimal, corresponds to half width of theQuaoar's ring).
Since the present observations require higher SNs of the light curves and the target
stars are relatively faint for the 2015MQ204 and 1995SM55 occultation events,
we request the exposure time of each frame to be relatively longer.

We thus request exposure times for each frame to be shorter than 0.18, 3.8, 0.18, and1.3 seconds for the 2023-09-30, 2023-10-24, 2023-11-09, and 2023-12-20 events,
respectively.
8、Special note regarding target body
9. Referebce of papers, books and documents
・Arimatsu, Hashimoto, et al., Evidence for a rapid decrease of Pluto’s atmosphericpressure revealed by a stellar occultation in 2019, Astronomy & Astrophysics, 638, L5,
2020
・Arimatsu, Hashimoto, et al., New Constraint on the Atmosphere of (50000) Quaoar from aStellar Occultation, The Astronomical Journal, 158, 236, 2019
・Arimatsu, et al., A kilometre-sized Kuiper belt object discovered by stellar
occultation using amateur telescopes, Nature Astronomy, 3, 301, 2019
・Arimatsu, et al., Detectability of Optical Transients with Timescales of Subseconds,
The Astronomical Journal, 161, 135, 2021
・Arimatsu, et al., Organized Autotelescopes for Serendipitous Event Survey (OASES):
Design and performance, Publ. Astron. Soc. Japan, 69, 4, 201
10. Necessity for cooperation with other regions
11.Restrictions on publication of observation results *Yes:Two years after the last observation or on the date the paper is published, whichevercomes first.
12. extra documents
・https://www.asteroidoccultation.com/2023_09/0930_144897_82124.htm
・http://hal-astro-lab.com/asteroid/2023_10_24%200%202015%20MQ204.png
・https://www.bedekkingen.vvs.be/predictions/asteroids2023/PDF/B23_11002.pdf
・http://hal-astro-lab.com/asteroid/2023_12_20%2024835%201995%20SM55.png