# The Rings of (2060) Chiron: Evidence of an Evolving System

C. Pereira, F. Braga-Ribas, B. Sicardy, R. Leiva, M. Assafin, B. Morgado, J. Ortiz, P. Santos-Sanz, J. Camargo, G. Margoti, et al.

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## To cite this version:

C. Pereira, F. Braga-Ribas, B. Sicardy, R. Leiva, M. Assafin, et al. The Rings of (2060) Chiron: Evidence of an Evolving System. The Astrophysical Journal Letters, 2025, 992 (2), pp.L19. 10.3847/2041-8213/ae0b6d. obspm-05360838

HAL Id: obspm-05360838

https://hal-obspm.ccsd.cnrs.fr/obspm-05360838v1

Submitted on 13 Nov 2025

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# The Rings of (2060) Chiron: Evidence of an Evolving System

C. L. Pereira¹,² ID, F. Braga-Ribas³,²,¹ ID, B. Sicardy⁴ ID, R. Leiva⁵ ID, M. Assafin⁶ ID, B. E. Morgado⁶ ID, J. L. Ortiz⁵ ID, P. Santos-Sanz⁵ ID, J. I. B. Camargo¹,² ID, G. Margoti³,²,¹ ID, Y. Kilic⁵ ID, G. Benedetti-Rossi² ID, R. Vieira-Martins¹,² ID, T. F. L. L. Pinheiro¹,⁷ ID, R. Sfair⁷,⁸ ID, F. L. Rommel⁹,²,³ ID, A. R. Gomes-Júnior¹⁰,² ID, R. C. Boufleur² ID, R. Duffard⁵ ID, J. Desmars¹¹,⁴ ID, D. Souami⁸,¹² ID, N. Morales⁵ ID, F. Arrese¹³, K. Barkaoui¹⁴,¹⁵,¹⁶ ID, A. Burdanov¹⁶ ID, C. A. Colazo¹⁷,¹⁸ ID, C. A. Domingues¹⁹, H. Dutra⁶ ID, R. C. Gargalhone²⁰ ID, C. Jacques²¹,²²,²³ ID, F. Jablonski²⁴ ID, L. Liberato²⁵ ID, R. Melia¹⁸, J. C. Oliveira²⁶, M. Sardiña²⁷,²⁸,²⁹ ID, J. Spagnotto²⁷,²⁸,²⁹ ID, T. Speranza³⁰ ID, A. Wilberger³¹,²⁹ ID, M. A. Zorzan³² ID, L. S. Brito⁷ ID, J. P. Cavalcante⁷, T. Q. Costa³³, M. Emilio³⁴,¹ ID, E. Garcia-Migani³⁵, M. Gillon¹⁵ ID, E. Gradovski¹,²,³ ID, E. Jehin³⁶ ID, V. Lattari⁷, M. Malacarne³⁷ ID, L. A. Mammana³⁸,³⁹ ID, M. Melita⁴⁰,³⁹,⁴¹ ID, W. Melo⁴² ID, A. J. Ortiz³³ ID, P. Quitral-Manosalva⁴³ ID, G. Ramon⁷, I. Rodrigues⁴⁴, and L. Vanzi⁴⁵

¹Observatório Nacional/MCTI, R. General José Cristino 77, CEP 20921-400, RJ, Brazil

²Laboratório Interinstitucional de e-Astronomia/LIneA, Av. Pastor Martin Luther King Jr., 126, Torre 3000 / sala 817. CEP 20765-000, RJ, Brazil

³Federal University of Technology—Paraná (UTFPR-Curitiba), Rua Sete de Setembro, 3165, CEP 80230-901, PR, Brazil

⁴Laboratoire Temps Espace (LTE), Observatoire de Paris, Université PSL, CNRS UMR 8255, Sorbonne Université, LNE, 61 Av. de l'Observatoire, F75014 Paris, France

⁵Instituto de Astrofísica de Andalucía, Glorieta de la Astronomía S/N, 18008 Granada, Spain

⁶Universidade Federal do Rio de Janeiro—Observatório do Valongo, Ladeira Pedro Antônio 43, CEP 20080-090, RJ, Brazil

⁷UNESP—São Paulo State University, Grupo de Dinâmica Orbital e Planetologia, CEP 12516-410, SP, Brazil

⁸LIRA, CNRS UMR8254, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université, 92190 Meudon, France

⁹Flórida Space Institute (University of Central Florida), 12354 Research Parkway, Partnership 1, Orlando, FL 32826, USA

¹⁰Institute of Physics, Federal University of Uberlândia, Av. João Naves de Ávila, CEP 38408-100, MG, Brazil

¹¹Institut Polytechnique des Sciences Avancées IPSA, 63 boulevard de Brandebourg, F-94200 Ivry-sur-Seine, France

¹²naXys, Department of Mathematics, University of Namur, Rue de Bruxelles 61, Namur 5000, Belgium

¹³Department of Physics, National University of La Pampa (UNLPAM), Santa Rosa, La Pampa, Argentina

¹⁴Instituto de Astrofísica de Canarias (IAC), Calle Vía Láctea s/n, 38200, La Laguna, Tenerife, Spain

¹⁵Astrobiology Research Unit, Université de Liège, Allée du 6Août 19C, B-4000 Liège, Belgium

¹⁶Department of Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA

¹⁷Observatorio Astronómico El Gato Gris (MPC I19)—Tanti, Córdoba, Argentina

¹⁸Observatorio de Raúl Meliá Carlos Paz, Carlos Paz, Córdoba, Argentina

¹⁹Observatório Estrela do Sul, Estrada Mará, km 05, Gleba Ribeirão Aqidaban, CEP 87112-390, PR, Brazil

²⁰Laboratório Nacional de Astrofísica, Rua dos Estados Unidos, 154, CEP 37504-364, MG, Brazil

²¹SONEAR Observatory, Serra da Piedade, Caeté, MG, Brazil

²²SONEAR2 Observatory, Rua Osório de Morais 22, Bairro Ouro Preto, Belo Horizonte, MG, Brazil

²³SONEAR3 Observatory, Serra da Piedade, Km3, Caeté, MG, Brazil

²⁴Instituto Nacional de Pesquisas Espaciais, Div. de Astrofísica. Av. dos Astronautas, 1758, CEP 12227-010, SP, Brazil

²⁵Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Bd de l'Observatoire, CS 34229, 06304 Nice Cedex 4, France

²⁶Independent Researcher, Secretaria de Estado da Educação do Paraná (SEED-PR), PR, Brazil

²⁷Observatorio El Catalejo (MPC I48), Santa Rosa, La Pampa, Argentina

²⁸Proyecto de Observación Colaborativa y Regional de Ocultaciones Asteroidales (POCROA), Argentina

²⁹Grupo de Astronomía Pampeano (GAP), La Pampa, Argentina

³⁰Observatorio Astronómico Municipal Reconquista (GORA OMR), Reconquista, Santa Fe, Argentina

³¹Observatorio Astronómico Los Cabezones (MPC X12), Santa Rosa, La Pampa, Argentina

³²Edmond Halley Astronomy Club, Praça Ademar Bornia, PR, Brazil

³³Instituto Federal do Paraná, Campus Ivaiporã, Rua Max Arthur Greipel, 505, 86870-000, PR, Brazil

³⁴Universidade Estadual de Ponta Grossa, Campus Uvaranas, Av. General Carlos Cavalcanti, 4748, CEP 84030-900, PR, Brazil

³⁵Grupo de Ciencias Planetarias, Universidad Nacional de San Juan—CONICET, Argentina

³⁶STAR Institute, Université de Liège, Allée du 6 Août 19C, B-4000 Liège, Belgium

³⁷Federal University of Espírito Santo, Av. Fernando Ferrari, 514, ES, Brazil

³⁸El Leoncito Astronomical Complex (CASLEO), Av. España 1512 Sur J5402DSP, San Juan, Argentina

³⁹Faculty of Astronomical and Geophysical Sciences, National University of La Plata, Paseo del Bosque S/N. La Plata, B1900FWA, Argentina

⁴⁰Instituto de Astronomía y Física del Espacio. (CONICET-UBA). Intendente Güraldes S/N. CABA. C1428ZAA., Argentina

⁴¹Instituto de Tecnología e Ingeniería. UNAHUR. Vergara 2222, Hurlingham, Prov. de Buenos Aires, Argentina

⁴²Instituto de Aeronáutica e Espaço: São José dos Campos, SP, Brazil

⁴³Departamento de Física, Universidad Católica del Norte, Avenida Angamos 0610, Casilla 1280, Antofagasta, Chile

⁴⁴UNIVAP, Universidade do Vale do Paraíba, Av. Shishima Hifumi, 2911, São José dos Campos, 12244-000, SP, Brazil

⁴⁵Department of Electrical Engineering and Center of Astro Engineering, Pontifícia Universidade Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Región Metropolitana, Chile

Received 2025 August 8; revised 2025 September 10; accepted 2025 September 20; published 2025 October 14

## Abstract

The centaur (2060) Chiron has long been a candidate for hosting material in orbit, based on occultation and photometric and spectroscopic data. Here, we present a multichord stellar occultation observed on September 10 UT that reveals new and complex structures surrounding Chiron. High-cadence light curves show

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multiple secondary events that are best explained (when compared with a multishell interpretation) with a system of three confined rings located at average radii of 273, 325, and 438 km, the outermost of which lies beyond Chiron's Roche limit. The rings appear coplanar, with a mean pole orientation of $\lambda = 151^{\circ} \pm 4^{\circ}$ and $\beta = 20^{\circ} \pm 6^{\circ}$. A broader, disklike structure extends from about 200 to 800 km, and a newly detected faint feature is observed at ~1380 km. Chiron thus appears as the fourth small solar system body known for hosting a ring system. Comparisons with previous occultation events that have occurred since 1994 show that these features are not permanent. With these observations, we may witness for the first time the ongoing formation and evolution of a ring system.

*Unified Astronomy Thesaurus concepts: Centaur group (215); Stellar occultation (2135); Planetary rings (1254)*

**1. Introduction**

The discovery of rings around the Centaur (10199) Chariklo (F. Braga-Ribas et al. 2014), the dwarf planet (136108) Haumea (J. L. Ortiz et al. 2017), and the large trans-Neptunian object (50000) Quaoar (B. E. Morgado et al. 2023; C. L. Pereira et al. 2023) has reshaped our understanding of how such structures can form and survive in the outer solar system. These unexpected detections, often involving material located beyond the classical Roche limit, suggest a broader range of dynamical conditions under which rings can persist around small bodies. The diversity found in the rings around small bodies suggests that their formation must have been the result of a combination of factors, such as primordial collisions, catastrophic impacts, or ejection processes (B. Sicardy et al. 2025), combined with a dynamically favorable environment around the central body (S. M. Giuliatti Winter et al. 2023; H. Salo & B. Sicardy 2024; B. Sicardy & H. Salo 2024).

The Centaur (2060) Chiron has long been known for photometric activity attributed to a surrounding coma (S. J. Bus et al. 1989; W. K. Hartmann et al. 1990; K. J. Meech & M. J. S. Belton 1990; R. Duffard et al. 2002). Stellar occultations since the 1990s have revealed transient narrow features (J. L. Elliot et al. 1995; S. J. Bus et al. 1996) and, more recently, ringlike structures consistent across multiple events in 2011, 2018, and 2022 (J. L. Ortiz et al. 2015, 2023; J. D. Ruprecht et al. 2015; A. A. Sickafoose et al. 2020; A. A. Sickafoose et al. 2023). The latter identified two dense features embedded in a broad envelope, with material extending to ~580 km from Chiron's center.

In early 2021, Chiron experienced a sustained ~1 mag brightening (M. M. Dobson et al. 2021; J. L. Ortiz et al. 2023), attributed to dust or ice ejection due to exposure of volatiles or ice phase transitions (M. M. Dobson et al. 2024). This is consistent with increased material inferred from the 2022 occultation. James Webb Space Telescope (JWST)/NIRSpec observations in July 2023 detected gaseous CH$_4$, CO$_2$, and solid CO, suggesting a complex environment comprising a nucleus, a coma, and a debris ring (N. Pinilla-Alonso et al. 2024).

In this Letter, we report a multichord stellar occultation by Chiron on 2023 September 10 UT. High-cadence photometry reveals multiple narrow features consistent with a three-ring system, embedded in a broad disklike structure and accompanied by a newly detected and yet-to-be-confirmed external component. The study of these structures sheds light on the processes governing their formation and long-term evolution. It also broadens our understanding of the dynamics of similar structures on other scales, such as planetary rings and circumplanetary disks.

**2. Observations and Data Analysis**

This work presents a joint analysis of four stellar occultations by Chiron between 2011 and 2023. Predictions and observational details for the 2011, 2018, and 2022 events are available in previous studies (see; J. D. Ruprecht et al. 2015; A. A. Sickafoose et al. 2020, 2023; J. L. Ortiz et al. 2023). The most recent event, on 2023 September 10, was predicted by the *Lucky Star* project$^{46}$ using Gaia Data Release 3 (Gaia Collaboration et al. 2023) stellar position and a high-precision NIMA$^{47}$ (J. Desmars et al. 2015) ephemeris for Chiron (see Table 1 for details). A total of 31 observation sites across South America participated (see Table 2 for observational circumstances), coordinated via the Occultation Portal$^{48}$ (Y. Kilic et al. 2022). The most significant data were obtained from the Perkin-Elmer 1.6 m telescope (hereafter PE160) at the Pico dos Dias Observatory (LNA, Brazil), with high-cadence (10 Hz) imaging.

These observations revealed both a broad feature and embedded dense, confined structures. Additional secondary flux drops were detected by other stations in this event, aiding the determination of the ring pole orientation and semimajor axis, though they were unresolved. The 2023 occultation led to six effective detections of Chiron's solid body. While a full analysis of the main body's shape and the fitted limb ellipse has been performed, this will be presented in a separate study. In the present work, we focus solely on the detection of secondary features and the center of the projected ellipse, which provides the offset used to model the ring system.

**3. Extended and Confined Ring Structures**

The presence of a coma around Chiron and broad flux drops observed in past occultations motivated an investigation into whether extended material could be detected in the light curves. The 2023 occultation revealed sharp drops of flux embedded in broader, diffuse variations, along with a more distant structure around 1380 km from Chiron's center. To test the possible geometries of the extended material, we considered two simplified hypotheses: (i) a broad equatorial disk sharing the rings' pole orientation and (ii) multiple overlapping spherical shells. The latter were not intended as a physical model of Chiron's dust coma, which is known to exist, but rather as a parametric representation of isotropic, diffuse extinction that could mimic the appearance of cometary comae. This approach allowed us to assess whether an isotropic distribution of dust could explain the data, without introducing the complexity of a full cometary coma model.

<footnote>$^{46}$ https://lesia.obspm.fr/lucky-star</footnote>

<footnote>$^{47}$ Numerical Integration of the Motion of an Asteroid.</footnote>

<footnote>$^{48}$ https://occultationportal.org</footnote>
<figure><img src="image_4.png" /><figcaption>**Figure 1.** Comparison between the equatorial disk and shell models. In the panels, the black curve represents the corresponding model compared to the observed light curve. (a) The time-based light curve is projected in the radial distance on the ring plane considering the preferred mean pole orientation. (b) The normalized flux as a function as the radial distance in the sky plane, compared with the model based in the consecutive spherical shells. The residuals plus 1 for the equatorial disk (c) and shell (d) models.</figcaption></figure>

<table><caption>**Table 1**

Occulted Star and Chiron's Details</caption><thead><tr><th></th><th>Occulted Star</th></tr></thead><tbody><tr><td>Epoch</td><td>2023-09-10 05:09:06.1 UTC</td></tr><tr><td>Source ID</td><td>GDR3 2578194139653336448</td></tr><tr><td>Star position at Epoch<sup>a</sup></td><td>α<sub>°</sub> = 1h06m30s376171 ± 0.124 mas<br>δ<sub>°</sub> = 8°44′41″.750877 ± 0.126 mas</td></tr><tr><td>Magnitudes<sup>b</sup></td><td>G: 13.26, B: 13.87, V: 13.23, R: 13.08,<br>J: 12.03, H: 11.65, K: 11.610</td></tr><tr><td>Star apparent</td><td>0.0208 mas/0.27 km</td></tr><tr><td>Diameter<sup>c</sup></td><td>...</td></tr></tbody><thead><tr><th></th><th>(2060) Chiron</th></tr></thead><tbody><tr><td>Ephemeris</td><td>NIMAv15</td></tr><tr><td>Geocentric distance</td><td>17.891995 au</td></tr><tr><td>Rotation period<sup>d</sup></td><td>5.917813 ± 0.000007 hr</td></tr><tr><td>Equivalent radius<sup>e</sup></td><td>98 ± 17 km</td></tr><tr><td>Mass<sup>e</sup></td><td>(4.8 ± 2.3) × 10<sup>18</sup> kg</td></tr></tbody></table>

**Notes.**

For both models, the broad flux drops were described by Gaussian profiles characterized by their central position $x_0$, width $\sigma$, and apparent opacity $p'$. The free parameters were optimized by minimizing residuals with a Levenberg-Marquardt algorithm, excluding the sharp flux drops of the confined rings by restricting the fit to data within $\pm 2\sigma$ of the median baseline.

The equatorial disk model assumes a flat, circular structure with azimuthally uniform optical depth in Chiron's equatorial plane, with the stellar flux mapped onto radial distance profiles on the ring plane. In contrast, the spherical shell model was constructed from overlapping three-dimensional Gaussian

functions projected onto the sky plane, intended as a parametric test of isotropic extinction rather than a physical model of the coma. The Gaussian models and the residuals are shown in Figure 1, highlighting that only the equatorial disk provides a satisfactory fit to the data.

We modeled Chiron's ring structures with routines based on SORA (A. R. Gomes-Júnior et al. 2022) using square-well profiles, which provide the ingress and egress times and opacities of semitransparent features. To isolate the confined rings, we first subtracted the extinction caused by the broad disk and fit the remaining structures in the residual light curves using $\chi^2$ minimization (Figure 1, panel (c)). Some features required composite models with multiple square boxes to achieve satisfactory fits (see Figure 2). The radial distances of each structure were derived from the midpoints of ingress and egress times projected onto the ring plane, while radial widths were obtained from their separation. Optical properties, including apparent and normal opacities and optical depths, were computed from square-well fits accounting for Fresnel diffraction by the entire ring and Airy diffraction by individual particles (J. N. Cuzzi 1985; F. Roques et al. 1987).

We model Chiron's rings as flattened circular structures centered on the body. For each secondary feature detected in the 2011, 2018, 2022, and 2023 occultations, we calculate its sky-plane position by averaging the disappearance and reappearance times. Associated uncertainties consider timing errors and the duration of each occultation. A projected ellipse is then fitted to these positions, taking into account the opening and position angles of the rings at each event. Assuming a stable pole orientation between 2011 and 2023, we searched for the best-fitting solutions for each ring's radius and pole orientation, identifying three distinct rings. Each ring yields two mirrored solutions, with the preferred one consistent with observed long-term brightness variations.

## 4. Results

The 2023 event reveals a broad disklike feature with about 550 km in radial extent, with a median normal optical depth $\tau_N = 0.016$, embedding at least three distinct dense rings: Chi1R, Chi2R, and Chi3R (Figure 3). The observed gradual

<footnote><sup>a</sup> The star position was taken from the Gaia Data Release 3 (GDR3) star catalog (Gaia Collaboration et al. 2023) and is propagated to the event epoch using SORA (A. R. Gomes-Júnior et al. 2022).</footnote>

<footnote><sup>b</sup> *J*, *H*, and *K* from the NOMAD catalog (N. Zacharias et al. 2004).</footnote>

<footnote><sup>c</sup> Estimated using the empirical relations of P. Kervella et al. (2004); the value of 0.27 km corresponds to its projected size at Chiron's geocentric distance.</footnote>

<footnote><sup>d</sup> R. L. Marcialis & B. J. Buratti (1993),</footnote>

<footnote><sup>e</sup> F. Braga-Ribas et al. (2023).</footnote>
<figure><img src="image_5.png" /><figcaption>**Figure 2.** Left: sky-plane projection of the shell model. The color map shows the optical depth $\tau = -\ln(T)/2$ from three Gaussian-distributed spherical shells. The central gray circle (98 km radius) marks Chiron's projected size; black ellipses indicate the confined rings; and red circles denote the Roche limits. Right: sky-plane view of the equatorial disk model. Optical depth $\tau = \tau_N/|\sin(B)|$ is shown. The gray circle (98 km radius) marks Chiron. Black ellipses show the three narrow rings; dashed blue ellipses mark the 1/2 and 1/3 SORs; and red ellipses indicate Roche limits. Inset: zoom-in of the innermost region with rings Chi1R (1), Chi2R (2), and Chi3R (3).</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>**Figure 3.** Occultation profile from the PE160 observation on 2023 September 10 event of the normal optical depth as a function of radial distance in the ring plane shows the extent of the broad ring and the arrangement of the dense rings. The colored regions indicate the boundaries of the SOR 1/2 resonance (green), SOR 1/3 resonance (red), and the Roche limit (blue). The vertical dotted lines indicate the respective ring center.</figcaption></figure>

return of the stellar flux near the central body to its baseline is consistent with a broad disk, rather than with a shell configuration (Figure 2).

The innermost ring, Chi1R, is detected at 273 ± 14 km from Chiron's center. Marginally seen in 2011 (J. D. Ruprecht et al. 2015; A. A. Sickafoose et al. 2020), it now exhibits $\tau_N = 0.045–0.12$ and equivalent width $E_p = 0.2–0.8$ km. Chi2R, located at 325 ± 11 km, consists of two components separated by a gap of 2–9 km (varying with longitude), with $\tau_N$ ranging from 0.1 (2023) to 0.35 (2011) (F. Braga-Ribas et al. 2023). Its equivalent width varies from 0.6 to 0.9 km across events. A third ring, Chi3R, lies at ~438 km and presents characteristics reminiscent of Quaoar's Q1R ring (B. E. Morgado et al. 2023; C. L. Pereira et al. 2023), Saturn's F ring (C. D. Murray & R. S. French 2018), and Neptune's arcs (W. B. Hubbard et al. 1986). Its optical depth varies azimuthally: from $\tau_N = 0.03$ (tenuous, ingress) to 0.3 (dense, egress). The radial width spans from 7 to 44 km. Assuming the dense portion detected at egress is a confined arc, we estimate a minimum azimuthal extent of ~25°, or ~190 km. Combining with 2022 detections, the

inferred extension may reach up to 140°, corresponding to an arc of ~1100 km. An outermost symmetrical feature, Chi4R, is detected at 1380 ± 11 km. It is modeled as a broad Gaussian profile with a radial width of 93 ± 11 km and peak $\tau_N \sim 10^{-3}$.

Fitting all secondary features across events yields three coplanar circular rings centered on Chiron (Figure 4). Each ring's pole is consistent within $1\sigma$ uncertainties with a mean orientation of $\lambda = 151.3 \pm 4.0, \beta = 19.9 \pm 6.0$, in ecliptic coordinates. This solution is preferred because it better accounts for the variations in Chiron's absolute magnitude (J. L. Ortiz et al. 2015). The alternative, mirrored solution is $\lambda = 331.5 \pm 4.2, \beta = -20.1 \pm 5.9$.

Recent estimates suggest that Chiron has a density of $\rho_C = 1119 \pm 4$ kg m$^{-3}$, corresponding to a mass of $M_C = (4.8 \pm 2.3) \times 10^{18}$ kg (F. Braga-Ribas et al. 2023). Based on this mass, we estimate that the synchronous orbit is located at $a_{sync} = 150 \pm 29$ km using a rotation period of $P = 5.917813 \pm 0.000007$ hr (R. L. Marcialis & B. J. Buratti 1993). Within uncertainties, the Chi1R and Chi2R rings align with the 1/2 and 1/3 spin-orbit resonances (SORs), located at
<figure><img src="image_7.png" /><figcaption>**Figure 4.** Sky-plane projection of Chiron and its confined rings. The projected ellipsoid and the occulting chords for each event are plotted in turquoise, with their $1\sigma$ uncertainties represented by the red segments at the chord extremities. The dashed blue lines represent the occulting chords as seen from each site. The red segments mark the projected widths of the ring events plus their respective $1\sigma$ error bars. The labels 1, 2, and 3 refers to the Chi1R, Chi2R, and Chi3R rings, respectively.</figcaption></figure>

$a_{1/2} = 238 \pm 45$ km and $a_{1/3} = 312 \pm 59$ km, respectively (Figure 3). At these radii, orbiting particles complete one revolution around Chiron for every two and three rotations of the body, respectively. The Roche critical density indicates the minimum density a body must have to stay gravitationally bound against the tidal forces of the central body. Classically, if the material's density is lower than this critical value, it tends to disperse and form a ring, whereas if it is higher, its observational circumstances may coalesce into a stable satellite (see B. E. Morgado et al. 2023). Assuming $\gamma = 1.6$ for tidally deformed particles, the Roche critical density $\rho_{\text{Roche}}$ is 413, 245, and $104 \text{ kg m}^{-3}$ for Chi1R, Chi2R, and Chi3R, respectively. If the ring material density is $\sim 400 \text{ kg m}^{-3}$ (comparable to Saturnian moons), the classical Roche limit ranges from 274 to 338 km depending on the ring particle's shape, spin state, and cohesion (B. Sicardy et al. 2025). The dense Chi1R and Chi2R rings may thus lie within the Roche limit, while the more distant Chi3R and Chi4R fall outside it.

## 5. Discussion

The multiyear consistency of detections of confined material strongly argues against interpreting the structures as transient phenomena, such as cometary jets or ephemeral dust shells. On the other hand, observational data indicate that the broad disk was not detected around Chiron in 2011 and 2018. Its inclusion in photometric models (e.g., J. L. Ortiz et al. 2015) would yield absolute magnitudes significantly brighter than observed unless its albedo is anomalously low. This discrepancy suggests that the broad disk formed recently, likely within the last decade. The region with the highest concentration of material (within the broad disk) spans from 258 to 328 km, matching the locations of the SOR 1/2 and SOR 1/3. Models on Chariklo's stability and ring confinement suggest that the region inside the SOR 1/2 would be cleared on short timescales (less than 10 yr) due to the elongation of the central body (B. Sicardy et al. 2019; S. M. Giuliatti Winter et al. 2023). Given Chiron's triaxial shape (F. Braga-Ribas et al. 2023), similar clearing is expected. This suggests that any material that was dispersed around Chiron through some mechanism would be expected to follow the same dynamical evolution.

We can estimate the broad ring mass from its surface density $\Sigma = (4/3)\tau_N r\rho_{\text{part}}$, where $r = 10^{-2}$ m is the assumed particle radius, $\rho_{\text{part}} = 400 \text{ kg m}^{-3}$ is the bulk density of the particles, and $\tau_N = 0.016$ is the median of the normal optical

depth in the ring region. We adopt $r = 10^{-2}$ m as this value lies at the lower end of the size range observed in Saturn's main rings (J. N. Cuzzi et al. 2018) and provides a conservative estimate in the absence of constraints for Chiron. For a ring with radius $a_{\text{ring}} = 485$ km and radial width $W_r \approx 600$ km, we found $m_{\text{ring}} \sim 10^{11}$ kg and a ring-to-Chiron mass ratio of $\mu \approx 3.5 \times 10^{-8}$. If released at a cometary mass-loss rate of $5000 \text{ kg s}^{-1}$, as estimated for comet 29P/Schwassmann-Wachmann-1 (D. Jewitt 2009), this mass could be produced in under 1 yr, comparable to the timescale of Chiron's 2021 outburst (M. M. Dobson et al. 2024). It is important to note that the comet 29P orbits much closer to the Sun than Chiron, which was near aphelion during the 2021 outburst event. This implies that the same level of mass loss at Chiron's distance would require more efficient energy deposition or a different activity mechanism.

The formation of an equatorial dust disk as a by-product from an outburst was observed in the comet C/2014 B1 (Schwartz), which exhibits a stable, disk-shaped coma (D. Jewitt et al. 2019). The morphology of the structure is consistent with dust grain ejection with a speed similar to the escape velocity, assisted by the centripetal forces that favor equatorial ejections (D. Jewitt et al. 2019). A similar mechanism may operate on Chiron, particularly as a new hemisphere has been progressively illuminated since 2000. This exposure could trigger localized sublimation, leading to episodic dust ejection.

Alternatively, Chiron's activity may result from impacts with debris generated by the fragmentation of another object. This hypothesis is supported by the temporal coincidence between Chiron's activity episodes and its passages through descending nodes (J. L. Ortiz et al. 2023). The object 2015 RD277 has been proposed as a potential progenitor of such a debris swarm (R. Gil-Hutton 2024), though the statistical likelihood of this scenario remains unconstrained.

Another plausible source of dispersed material is the gradual fragmentation of a small satellite orbiting Chiron. Long-term deviations in Chiron's absolute magnitude since 2010 suggest the presence of additional reflective material in its environment (R. Duffard et al. 2002; M. M. Dobson et al. 2024). Supporting this interpretation, JWST/NIRSpec observations in 2023 detected gas-phase CH$_4$ and CO$_2$ but no CO (N. Pinilla-Alonso et al. 2024). Given CO's lower sublimation temperature, its absence indicates that activity is not driven by continuous solar heating of surface or near-surface layers. Instead, CO likely
remains sequestered in amorphous ices or buried deeper in the subsurface, inaccessible to insolation. This points to episodic exposure of volatile-rich material, such as might occur through satellite disruption, as a more viable driver of recent activity.

Assuming that all the dispersed material originated from the catastrophic breakup of a single spherical satellite with a density of $\rho_{\text{part}} = 400 \text{ kg m}^{-3}$, the equivalent radius of that progenitor body would be approximately 0.5 km. Alternatively, adopting the bulk density of Chiron ($\rho_{\text{Chiron}} = 1119 \text{ kg m}^{-3}$; F. Braga-Ribas et al. 2023), the disrupted satellite would have a radius of approximately 0.3 km. However, attributing Chiron's recent brightening solely to the disruption of a satellite poses a challenge when considering its long history of recurrent outbursts over the past 70 yr (S. J. Bus et al. 2001; R. Duffard et al. 2002; J. L. Ortiz et al. 2015; M. M. Dobson et al. 2024). This discrepancy suggests that either multiple fragmentation events have occurred or that additional mechanisms such as internal pressure buildup of subsurface volatiles may be periodically driving activity on Chiron. Thus, we may be observing the result of different sources of dust material feeding Chiron's vicinity.

In the context of recent ring formation around Chiron, the presence of material resulting from a sudden event can lead to particles rapidly settling into the equatorial plane of the central body. This process is driven by gravitational perturbations caused by Chiron's dynamical oblateness $J_2$, the influence of radiation pressure, and mutual collisions between particles (P. Goldreich & S. Tremaine 1982; F. Marzari 2020). These collisions dissipate energy, promoting the alignment of particle orbits and contributing to the formation of a flattened equatorial ring structure. The collisional damping process can occur over short timescales, within fewer than 10 orbital periods of a particle located near the central body's Roche limit (S. Ida et al. 1997; E. Kokubo et al. 2000).

An important implication of our findings is that we may be witnessing the ongoing formation of a ring system around a small body. The current features observed around Chiron, including the presence of dust, gas-phase volatiles, and confined ring material, could represent a transitional stage of a circumobject environment. This stage may bridge the gap between an initially chaotic distribution of debris (possibly generated by satellite fragmentation, transient outgassing events, or collisional processes) and the eventual development of a narrow, dense, and highly flattened ring system. Chiron may thus represent a rare observational window into an intermediate evolutionary phase, offering a potential missing link in the formation pathway of ring systems around small solar system bodies.

## Acknowledgments

We thank the anonymous referee for helpful comments that improved the Letter. C.L.P. thanks the FAPERJ/DSC-10 E-26/204.141/2022, FAPERJ/PDR-10 E-26/200.107/2025, and FAPERJ 200.108/2025. This work was carried out within the Lucky Star umbrella that agglomerates the efforts of the Paris, Granada, and Rio teams, which is funded by the European Research Council under the European Community H2020 (ERC grant Agreement No. 669416). This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES)—Finance Code 001 and the National Institute of Science and Technology of the e-Universe project (INCT do e-Universo, CNPq grant 465376/2014-2). The

following authors acknowledge the respective grants: F.B.-R.: CNPq 316604/2023-2; B.S. acknowledges support by the French ANR project Roche, number ANR-23-CE49-0012; M.A.: CNPq 427700/2018-3, 310683/2017-3, and 473002/2013-2, and FAPERJ E-26/210.705/2024; J.I.B.C.: CNPq 305917/2019-6 and 306691/2022-1, and FAPERJ 201.681/2019; R.V.-M.: CNPq 307368/2021-1; G.M.: CAPES PhD scholarship 88887.015375/2024-00; F.L.R.: CNPq 103096/2023-0, Florida Space Institute's Space Research Initiative, and the University of Central Florida's Preeminent Postdoctoral Program (P3); ARG-Jr: FAPEMIG APQ-02987-24; I.R.: CNPq 314267/2021-2; G.R.: FAPESP 2024/20150-1; R.L. acknowledges the support of Instituto de Estudios Astrofísicos, Universidad Diego Portales, for providing telescopes and logistical assistance. Part of this work was supported by the Spanish projects PID2020-112789GB-I00 from AEI and Proyecto de Excelencia de la Junta de Andalucía PY20-01309; Authors J.L.O., P.S.-S., N.M., and R.D. acknowledge financial support from the Severo Ochoa grant CEX2021-001131-S funded by MCIN/AEI/ 10.13039/501100011033; P.S.-S. and Y.K. acknowledge financial support from the Spanish I+D+i project PID2022-139555NB-I00 (TNO-JWST). Funding for K.B. was provided by the European Union (ERC AdG SUBSTELLAR, GA 101054354). We thank observers L. A. Pereira, O. M. Ribas, O. Margoti, R. Gil-Hutton, J. Rodrigues, E. F. Morato, A. J. L. Pereira, C. Andreolla, N. Castro, M. Fidêncio Neto, E. Miglioranza, F. Ruzza, A. Stechina, and E. Townsend for their efforts in collecting data. Some results were based on observations taken at the 1.6 m telescope on Pico dos Dias Observatory of the National Laboratory of Astrophysics (LNA/Brazil). Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere under ESO program 111.24SV.002. This research made use of SORA, a Python package for stellar occultations reduction and analysis, developed with the support of ERC Lucky Star and LIneA/Brazil. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (D.P.A.C., https://www.cosmos.esa.int/web/gaia/dpac/consortium). TRAPPIST is funded by the University of Liège and the Belgian Fund for Scientific Research (Fond National de la Recherche Scientifique, FNRS) under the grant PDR T.0120.21. E.J. G is F.R.S.-FNRS Research Director. The ULiege's contribution to SPECULOOS has received funding from the European Research Council under the European Union's Seventh Framework Program (FP/2007–2013; grant Agreement No. 336480/SPECULOOS), from the Balzan Prize and Francqui Foundations, from the Belgian Scientific Research Foundation (F.R.S.-FNRS; grant No. T.0109.20), from the University of Liège, and from the ARC grant for Concerted Research Actions financed by the Wallonia-Brussels Federation. We thank Chalé e Camping Luz (Sapopema, Paraná, Brazil) for kindly providing the site for our observation.

## Author Contributions

C.L.P. wrote the Letter and designed the figures, with major contributions from F.B.-R., B.S., and B.E.M. F.B.-R., R.L., J.L.O., P.S.-S., and R.D. organized the stellar occultation observational campaigns, with the collaboration of Y.K. and N.M. C.L.P. analyzed the data and derived the physical parameters presented in the Letter, with inputs from M.A.,
G.M., B.E.M., F.B.-R., and J.I.B.C. C.L.P., A.R.G.-J., R.C.B., G.B.-R., F.L.R., G.M., M.A., Y.K., and J.D. were the main developers of the data analysis software used in this project. F. B.-R., M.A., B.E.M., P.S.-S., J.I.B.C., R.V.-M., T.F.L.L.P., and D.S. contributed to the interpretation and review of the results. All remaining authors participated in the observation of the occultation event. They are listed in alphabetical order— first those who reported positive and negative results, followed by those who experienced overcast conditions or technical failures. All authors had the opportunity to review the results and comment on the manuscript.

Facility: LNA:1.6m.

Software: SORA (https://github.com/riogroup/SORA); PRAIA (https://ov.ufrj.br/en/PRAIA/), ASTROPY (Astropy Collaboration et al. 2013, 2018, 2022).

## Appendix
### Observation Circumstances

The observational circumstances for each site involved in the stellar occultation campaign presented in this work are listed in Table 2.
<table><caption>**Table 2**
Observation Circumstances for All the Observatories Involved in the 2023 September 10 Event</caption><thead><tr><th>Site</th><th>Latitude<br>(°′′)</th><th>Longitude<br>(°′′′)</th><th>Altitude (m)</th><th>Telescope<br>(mm)</th><th>Camera</th><th>Filter</th><th>Exposure (s)</th><th>Cycle (s)</th><th>Status</th><th>Observer</th></tr></thead><tbody><tr><td>OPD PE<br>Minas Gerais<br>Brazil</td><td>-22.32<br>05.886</td><td>-45.34<br>59.222</td><td>1864.0</td><td>1600</td><td>IXon</td><td>Clear</td><td>0.120</td><td>0.133</td><td>Positive</td><td>...</td></tr><tr><td>OPD B&C/IAG<br>Minas Gerais<br>Brazil</td><td>-22.32<br>04.428</td><td>-45.34<br>57.692</td><td>1864.0</td><td>600</td><td>IXon</td><td>Clear</td><td>0.670</td><td>0.683</td><td>Positive</td><td>G. Benedetti-Rossi<br>...</td></tr><tr><td>OPD T40<br>Minas Gerais<br>Brazil</td><td>-22.32<br>06.910</td><td>-45.34<br>59.691</td><td>1864.0</td><td>400</td><td>Andor Zyla 4.2</td><td>Clear</td><td>1.000</td><td>1.110</td><td>Positive</td><td>L. Liberato<br>H. Dutra<br>...</td></tr><tr><td>OAMR<br>Reconquista<br>Argentina</td><td>-29.09<br>17.809</td><td>-59.38<br>45.762</td><td>50.0</td><td>254</td><td>Player One Ceres-M</td><td>Clear</td><td>0.800</td><td>2.000</td><td>Positive</td><td>F. Jablonski<br>R. C. Gargalhone<br>...</td></tr><tr><td>OAMR<br>Reconquista<br>Argentina</td><td>-29.08<br>25.183</td><td>-59.38<br>36.609</td><td>50.0</td><td>305</td><td>QHY174GPS</td><td>Clear</td><td>0.600</td><td>0.600</td><td>Positive</td><td>T. Speranza<br>...</td></tr><tr><td>OES<br>Sarandi<br>Brazil</td><td>-23.30<br>49.164</td><td>-51.51<br>33.270</td><td>469.0</td><td>200</td><td>Raptor</td><td>Clear</td><td>0.500</td><td>0.500</td><td>Positive</td><td>F. Braga-Ribas<br>C. A. Domingues<br>...</td></tr><tr><td>OES - eVscope 1<br>Sarandi<br>Brazil</td><td>-23.30<br>49.164</td><td>-51.51<br>33.270</td><td>469.0</td><td>114</td><td>Sony IMX224LQR</td><td>Clear</td><td>1.000</td><td>1.000</td><td>Positive</td><td>F. Braga-Ribas<br>M. Zorzan<br>...</td></tr><tr><td>Mobile<br>La Rioja<br>Argentina</td><td>-30.55<br>08.300</td><td>-66.07<br>55.500</td><td>455.0</td><td>200</td><td>QHY174M GPS</td><td>Clear</td><td>0.750</td><td>0.750</td><td>Positive</td><td>J. Spagnotto<br>M. Sardiña<br>...</td></tr><tr><td>Mobile<br>La Rioja<br>Argentina</td><td>-31.34<br>15.426</td><td>-66.14<br>11.256</td><td>405.0</td><td>200</td><td>QHY174M GPS</td><td>Clear</td><td>0.750</td><td>0.750</td><td>Positive</td><td>A. Wilberger<br>F. Arrese<br>...</td></tr><tr><td>SONEAR3<br>Minas Gerais<br>Brazil</td><td>-19.49<br>27.263</td><td>-43.41<br>24.025</td><td>1830.0</td><td>450</td><td>QHY600</td><td>Clear</td><td>2.000</td><td>4.240</td><td>Positive</td><td>C. Jacques<br>...</td></tr></tbody></table>
<table><caption>**Table 2**
(Continued)</caption><thead><tr><th>Site</th><th>Latitude (°′″)</th><th>Longitude (°′′′)</th><th>Altitude (m)</th><th>Telescope (mm)</th><th>Camera</th><th>Filter</th><th>Exposure (s)</th><th>Cycle (s)</th><th>Status</th><th>Observer</th></tr></thead><tbody><tr><td>Villa Carlos Paz<br>Córdoba<br>Argentina</td><td>-31.24<br>48.499</td><td>-64.30<br>21.499</td><td>708.4</td><td>254</td><td>QHY174M GPS</td><td>Clear</td><td>1.000</td><td>1.000</td><td>Positive</td><td>R. Meliá<br>C. A. Colazo<br>...</td></tr><tr><td>SONEAR2<br>Minas Gerais<br>Brazil</td><td>-19.52<br>55.082</td><td>-43.49<br>03.120</td><td>885.0</td><td>280</td><td>QHY600</td><td>Clear</td><td>3.000</td><td>5.740</td><td>Negative</td><td>...</td></tr><tr><td>VLT UT4<br>Cerro Paranal<br>Chile</td><td>-24.37<br>37.301</td><td>-70.24<br>14.062</td><td>2637.0</td><td>8400</td><td>HAWKI</td><td>J</td><td>0.100</td><td>N/A</td><td>Negative</td><td>...</td></tr><tr><td>SPECULOOS-S<br>Cerro Paranal<br>Chile</td><td>-24.36<br>57.917</td><td>-70.23<br>26.016</td><td>2479.2</td><td>1000</td><td>Andor iKon-L</td><td>g' and r'</td><td>0.500</td><td>N/A</td><td>Negative</td><td>...</td></tr><tr><td>OUC<br>Santiago<br>Chile</td><td>-33.16<br>08.936</td><td>-70.32<br>04.135</td><td>1475.2</td><td>500</td><td>Raptor Merlin</td><td>Clear</td><td>1.000</td><td>1.000</td><td>Overcast</td><td>N. Castro<br>L. Vanzi<br>R. Leiva</td></tr><tr><td>CASLEO<br>San Juan<br>Argentina</td><td>-31.47<br>55.018</td><td>-69.17<br>44.236</td><td>2485.0</td><td>2153</td><td>CCD Directo</td><td>Clear</td><td>2.000</td><td>N/A</td><td>Overcast</td><td>R. Gil-Hutton<br>E. Garcia-Migani<br>L. Mammana</td></tr><tr><td>NTT<br>La Silla<br>Chile</td><td>-29.15<br>32.054</td><td>-70.44<br>01.637</td><td>2345.4</td><td>3580</td><td>ULTRACAM</td><td>u', g', r'</td><td>0.100</td><td>N/A</td><td>Overcast</td><td>ULTRACAM team<br>R. Leiva<br>...</td></tr><tr><td>Alianza S4<br>San Juan<br>Argentina</td><td>-31.47<br>12.401</td><td>-69.18<br>24.480</td><td>2664.0</td><td>450</td><td>SBIG STX11000</td><td>Clear</td><td>N/A</td><td>N/A</td><td>Overcast</td><td>J. L. Ortiz, N. Morales<br>P. Santos-Sanz<br>R. Duffard</td></tr><tr><td>Dois Vizinhos<br>Paraná<br>Brazil</td><td>-25.42<br>16.592</td><td>-53.05<br>51.360</td><td>550.0</td><td>203</td><td>Raptor Merlin</td><td>Clear</td><td>N/A</td><td>N/A</td><td>Overcast</td><td>F.Rommel, F.Ruzza<br>E. Miglioranza<br>C. Andreolla<br>E. Townsend</td></tr></tbody></table>
<table><caption>**Table 2**
(Continued)</caption><thead><tr><th>Site</th><th>Latitude (°/′′)</th><th>Longitude (°/′′)</th><th>Altitude (m)</th><th>Telescope (mm)</th><th>Camera</th><th>Filter</th><th>Exposure (s)</th><th>Cycle (s)</th><th>Status</th><th>Observer</th></tr></thead><tbody><tr><td>Obser. UEPG<br>Paraná<br>Brazil</td><td>-25.05<br>22.671</td><td>-50.05<br>56.790</td><td>923.0</td><td>406</td><td>Raptor Merlin</td><td>Clear</td><td>N/A</td><td>N/A</td><td>Overcast</td><td>...</td></tr><tr><td>Sapopema<br>Paraná<br>Brazil</td><td>-23.51<br>09.024</td><td>-50.39<br>29.794</td><td>759.0</td><td>305</td><td>QHY174M GPS</td><td>Clear</td><td>N/A</td><td>N/A</td><td>Overcast</td><td>...</td></tr><tr><td>UNIVAP<br>São Paulo<br>Brazil</td><td>-23.12<br>30.022</td><td>-45.57<br>49.407</td><td>600.0</td><td>300</td><td>Raptor Merlin</td><td>Clear</td><td>N/A</td><td>N/A</td><td>Overcast</td><td>L. Brito, V. Lattari<br>W. Melo<br>I. Rodrigues</td></tr><tr><td>Gemini South<br>Cerro Pachón<br>Chile</td><td>-30.14<br>26.308</td><td>-70.44<br>11.580</td><td>2715.4</td><td>8000</td><td>Zorro</td><td>Clear</td><td>N/A</td><td>N/A</td><td>Overcast</td><td>...</td></tr><tr><td>OACEP<br>Paraná<br>Brazil</td><td>-25.20<br>57.494</td><td>-49.21<br>55.050</td><td>1055.0</td><td>305</td><td>WATEC 910HX</td><td>Clear</td><td>0.08</td><td>N/A</td><td>Overcast</td><td>E. Gradovski<br>J. Antunes<br>E. Fonseca, J. Carlos</td></tr><tr><td>OAM-IAG/USP<br>São Paulo<br>Brazil</td><td>-23.00<br>13.680</td><td>-46.57<br>52.920</td><td>870.0</td><td>406</td><td>U9000 APOGEE</td><td>Clear</td><td>N/A</td><td>N/A</td><td>Overcast</td><td>...</td></tr><tr><td>CASLEO<br>San Juan<br>Argentina</td><td>-31<br>47.13.2</td><td>-69<br>18.24.12</td><td>2591.0</td><td>600</td><td>SBig</td><td>Clear</td><td>N/A</td><td>N/A</td><td>Overcast</td><td>M. Melita<br>L. Mammana<br>...</td></tr><tr><td>Mobile<br>La Mostaza<br>Chile</td><td>-31.52 2.1</td><td>-71.26 25.1</td><td>55.0</td><td>203</td><td>QHY174M GPS</td><td>Clear</td><td>N/A</td><td>N/A</td><td>Overcast</td><td>R. Leiva<br>P. Quitral-<br>Manosalva</td></tr><tr><td>TRAPPIST-S<br>La Silla<br>Chile</td><td>-29<br>15.16.56</td><td>-70<br>44.21.84</td><td>2315.0</td><td>600</td><td>PL3041-BB</td><td>Clear</td><td>0.500</td><td>N/A</td><td>Overcast</td><td>...</td></tr><tr><td>OPD Zeiss<br>Minas Gerais<br>Brazil</td><td>-22.32<br>06.664</td><td>-45<br>35.0.329</td><td>1864.0</td><td>600</td><td>iKon</td><td>Clear</td><td>N/A</td><td>N/A</td><td>Tech.<br>Failure</td><td>T.F.L.L. Pinheiro<br>J. P. Cavalcante<br>G. Ramon</td></tr></tbody></table>
<table><caption>**Table 2**
(Continued)</caption><thead><tr><th>Site</th><th>Latitude (°′″)</th><th>Longitude (°′′′)</th><th>Altitude (m)</th><th>Telescope (mm)</th><th>Camera</th><th>Filter</th><th>Exposure (s)</th><th>Cycle (s)</th><th>Status</th><th>Observer</th></tr></thead><tbody><tr><td>GOA<br>Espirito Santo<br>Brazil</td><td>-20<br>18 02.0</td><td>-40 19 02.0</td><td>24.0</td><td>304</td><td>ASI1600MMPro</td><td>Clear</td><td>N/A</td><td>N/A</td><td>Tech.<br>Failure</td><td>...</td></tr><tr><td>IFPR Ivaiporã<br>Paraná<br>Brazil</td><td>-24<br>15 3.874</td><td>-51.42<br>47.354</td><td>1200.0</td><td>254</td><td>QHY174M GPS</td><td>Clear</td><td>N/A</td><td>N/A</td><td>Tech.<br>Failure</td><td>G. Margorti<br>O. Margorti<br>A. J. Ortiz</td></tr></tbody></table>

**Notes.** OPD: Observatório do Pico dos Dias; PE: Perkin-Elmer; B&C: Boller & Chivens; OAMR: Observatorio Astronômico Municipal de Reconquista; OES: Observatório Estrela do Sul; SONEAR: Southern Observatory for Near Earth Asteroids Research; VLT: Very Large Telescope; SPECULOOS-S: Search for habitable Planets Eclipsing Ultra-cool Stars—South; OUC: Observatory of the Catholic University; CASLEO: Complejo Astronómico El Leoncito; NTT: New Technology Telescope; UEPG: Universidade Estadual de Ponta Grossa; UNIVAP: Universidade do Vale do Paraíba; OACEP: Observatório Astronômico do Colégio Estadual do Paraná; OAM-IAG/USP: Observatório Abrahão de Moraes, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo; TRAPPIST-S: Transiting Planets and Planetesimals Small Telescope—South; GOA: Gaturamo Observatório Astronômico; IFPR: Instituto Federal do Paraná.
ORCID iDs

C. L. Pereira https://orcid.org/0000-0003-1000-8113

F. Braga-Ribas https://orcid.org/0000-0003-2311-2438

B. Sicardy https://orcid.org/0000-0003-1995-0842

R. Leiva https://orcid.org/0000-0002-6477-1360

M. Assafin https://orcid.org/0000-0002-8211-0777

B. E. Morgado https://orcid.org/0000-0003-0088-1808

J. L. Ortiz https://orcid.org/0000-0002-8690-2413

P. Santos-Sanz https://orcid.org/0000-0002-1123-983X

J. I. B. Camargo https://orcid.org/0000-0002-1642-4065

G. Margoti https://orcid.org/0000-0002-2103-4408

Y. Kilic https://orcid.org/0000-0001-8641-0796

G. Benedetti-Rossi https://orcid.org/0000-0002-4106-476X

R. Vieira-Martins https://orcid.org/0000-0003-1690-5704

T. F. L. L. Pinheiro https://orcid.org/0000-0001-7126-4562

R. Sfair https://orcid.org/0000-0002-4939-013X

F. L. Rommel https://orcid.org/0000-0002-6085-3182

A. R. Gomes-Júnior https://orcid.org/0000-0002-3362-2127

R. C. Boufleur https://orcid.org/0000-0003-3452-1114

R. Duffard https://orcid.org/0000-0001-5963-5850

J. Desmars https://orcid.org/0000-0002-2193-8204

D. Souami https://orcid.org/0000-0003-4058-0815

N. Morales https://orcid.org/0000-0003-0419-1599

K. Barkaoui https://orcid.org/0000-0003-1464-9276

A. Burdanov https://orcid.org/0000-0001-9892-2406

H. Dutra https://orcid.org/0009-0002-5390-5703

R. C. Gargalhone https://orcid.org/0009-0000-2300-2891

F. Jablonski https://orcid.org/0000-0002-0386-2306

L. Liberato https://orcid.org/0000-0003-3433-6269

T. Speranza https://orcid.org/0009-0004-8376-5857

M. A. Zorzan https://orcid.org/0009-0004-2504-7670

L. S. Brito https://orcid.org/0000-0001-7446-5212

M. Emilio https://orcid.org/0000-0001-5589-9015

M. Gillon https://orcid.org/0000-0003-1462-7739

E. Jehin https://orcid.org/0000-0001-8923-488X

M. Malacarne https://orcid.org/0000-0002-0866-1802

M. Melita https://orcid.org/0000-0001-8128-0312

W. Melo https://orcid.org/0009-0006-8255-6441

A. J. Ortiz https://orcid.org/0000-0002-2222-2603

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