C/2025 R2 (SWAN): Possible Fragmentation Observed

ATel #17469; M. Serra-Ricart (Light Bridges, IAC, ULL), J. Licandro (IAC, ULL), M. R. Alarcon (Light Bridges, IAC, ULL)
on 2 Nov 2025; 22:54 UT
Credential Certification: Miquel Serra-Ricart (mserra@iac.es)

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Recent images of comet C/2025 R2 (SWAN) obtained with the 2.0-m TTT3 telescope suggest that the nucleus has undergone fragmentation. Although full confirmation is pending, the data indicate that the nucleus may be splitting into two components or releasing a substantial fragment. The attached figure shows the evolution of the cometary morphology from October 19.83 to November 2.85. On that date, the comet displayed a well-defined, symmetric central condensation. In subsequent nights, the central region became progressively elongated, culminating in the apparent detachment of a distinct secondary condensation. All the images were bias, dark and flat-field corrected in the standard way and aligned-and-staked from the cometary optocenter. Stacked images, shown in figure, include the projected velocity vector of the comet (blue arrow), the antisolar direction (yellow arrow), as well as the image orientation and distance scale. Comet C/2025 R2 (SWAN) has been extensively monitored from 2025 October 19 using the imaging capabilities of both the Two-Meter Twin Telescope (TTT, ttt.iac.es) and the Transient Survey Telescope (TST, tst.iac.es). TTT3 is a 2-meter f/6 Ritchey–Chretien telescope, currently in its commissioning phase. Images were obtained with COLORS, a 2k camera mounted at the Nasmyth 2 focus, equipped with a back-illuminated BEX2-DD CCD sensor, resulting in a field of view of 7.85 x 7.85 arcsec and a plate scale of 0.23 arcsec/pixel. TTT and TST are operated by Light Bridges in Tenerife, Canary Islands (Spain). The observation time rights (DTO) used for this research were consumed in the PEI PLANETIX25. This research used storage and computing capacity in ASTRO POCs EDGE computing center at Tenerife under the form of Indefeasible Computer Rights (ICR).

Evolution of coma morphology of C/2025 R2