Astrometric and Photometric Monitoring of Comet 240P and its fragment 240P-B
ATel #17665; M. Mugrauer (AIU Jena), M. Belger (AIU Jena), Z. Jamil (AIU Jena), K.-U. Michel (AIU Jena), B. Dincel (AIU Jena)
on 10 Feb 2026; 13:48 UT
Credential Certification: Markus Mugrauer (markus@astro.uni-jena.de)
Between 30 October 2025 and 21 January 2026, we conducted follow-up imaging observations of comet 240P and its fragment 240P-B in 19 observation epochs, using the Schmidt-Teleskop-Kamera (STK), which is operated in the Schmidt focus of the 90 cm reflector telescope at the University Observatory Jena. In each epoch, we took at least ten images with the instrument in the R-band with a detector integration time of 60 s. We measured the astrometry of the comet and its fragment. The projected separation of the fragment from 240P was 99500 ± 1200 km, on average, and decreased by 3000 ± 600 km during our monitoring campaign. The fragment was located southwest of the comet, and its position angle decreased from 236.3 ± 0.4° to 228.5 ± 0.4°. In addition, we determined the brightness of both objects in the R-band using aperture photometry. We derived the absolute brightness of 240P and its fragment under the assumption that only sunlight is reflected. As previously reported (ATel #17537), the fragment brightened significantly between 30 October and 3 December 2025. While the absolute R-band magnitude of the fragment increased by 2.20 ± 0.14 mag, the absolute brightness of 240P did not change significantly during the same period. Afterwards, both objects faded until the end of our observation campaign. Between 3 December 2025 and 21 January 2026, the absolute R-band brightness of the fragment decreased by 1.35 ± 0.14 mag, while the absolute brightness of comet 240P only dimmed by 0.87 ± 0.14 mag.
Astrometric and Photometric Monitoring of Comet 240P and its fragment 240P-B - Online Data
