C/2025 K1 (ATLAS): Multiple Fragmentation Observed

ATel #17487; M. Serra-Ricart (Light Bridges, IAC, ULL), J. Licandro (IAC, ULL), M. R. Alarcon (Light Bridges, IAC, ULL)
on 10 Nov 2025; 13:55 UT
Credential Certification: Miquel Serra-Ricart (mserra@iac.es)

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In response to the outburst alert of Comet C/2025 K1 (ATLAS) (telegram #17482), the TTT3 telescope initiated a monitoring campaign of the comet. On 2025 November 10, between 04:42 and 05:13 UT, a total of 70 individual 8-s exposures were obtained in the Luminance band, co-added along the cometary apparent motion and centered on its optocenter. Staked images are shown in attached figure. For each frame, the observation date and the start and end times in UTC are shown above the panels, together with the total number of sidereal-tracking exposures and the cumulative integration time. The projected velocity vector (red arrow) and the antisolar direction (yellow arrow) are marked, as well as the image scale and orientation. Red crosshairs mark the cometary optocenter. Isophotal contours of the original (non-filtered) images are overplotted using ten logarithmically spaced levels between the 10th and 80th percentiles of pixel intensity in each frame. The original non-filtered (sky) image (left panel) clearly shows two components, corresponding to the comet’s main nucleus (red crosshairs) and a detached fragment. A Laplace-filtered image of the inner coma (right panel), processed following Serra-Ricart & Licandro (2015, ApJ, 814, 49), further reveals a second, fainter fragment, confirming the presence of two distinct fragments in the central region of C/2025 K1 (ATLAS). 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 (Two-meter Twin Telescope) is 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).

Combined images showing fragments