Monitoring of asteroids in cometary orbits and activated asteroids through archival images and new observations^★

¹ Departamento de Astronomía, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay
² Observatório Nacional, R. Gen. José Cristino 77 - São Cristóvão, Rio de Janeiro, RJ - 20921-400 Brazil
³ Laboratório Interinstitucional de e-Astronomia - LIneA, Av. Pastor Martin Luther King Jr, 126, Rio de Janeiro - RJ - 20765-000 Brazil
⁴ Instituto de Astrofísica de Canarias, C/ Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
⁵ Department of Physics, University of Michigan, Ann Arbor, MI48109, USA
⁶ Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195, USA
⁷ Department of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT, UK
⁸ Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Campus UAB, 08193 Bellaterra (Barcelona) Spain
⁹ School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072, Australia
¹⁰ Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Madrid, Spain
¹¹ Fermi National Accelerator Laboratory, PO Box 500, Batavia, IL 60510, USA
¹² California Institute of Technology, 1200 East California Blvd, MC 249-17, Pasadena, CA 91125, USA
¹³ Instituto de Fisica Teorica UAM/CSIC, Universidad Autonoma de Madrid, 28049 Madrid, Spain
¹⁴ Institut d’Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain
¹⁵ Institute of Cosmology and Gravitation, University of Portsmouth, PO1 3FX, UK
¹⁶ University Observatory, Faculty of Physics, Ludwig-MaximiliansUniversität, Scheinerstr. 1, 81679 Munich, Germany
¹⁷ Center for Astrophysical Surveys, National Center for Supercomputing Applications, Urbana, IL 61801, USA
¹⁸ Santa Cruz Institute for Particle Physics, Santa Cruz, CA 95064, USA
¹⁹ Center for Astrophysics | Harvard & Smithsonian, Cambridge, MA 02138, USA
²⁰ Australian Astronomical Optics, Macquarie University, North Ryde, NSW 2113, Australia
²¹ Department of Physics and Astronomy, Texas A&M University, College Station, TX 77843, USA
²² LPSC Grenoble - 53, Avenue des Martyrs 38026 Grenoble, France
²³ Kavli Institute for Particle Astrophysics & Cosmology, Stanford University, Stanford, CA 94305, USA
²⁴ SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
²⁵ Department of Physics, Northeastern University, Boston, MA 02115, USA
²⁶ Physics Department, Lancaster University, Lancaster, LA1 4YB, UK
²⁷ Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
²⁸ Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA
²⁹ Department of Astronomy, University of California, Berkeley, CA 94720, USA
³⁰ Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA

^★★ Corresponding author.

Received: 13 February 2025
Accepted: 2 April 2025

Abstract

Context. Transitional objects are minor bodies that share some characteristics with asteroids and others with comets. These objects include asteroids in cometary orbits (ACOs), which behave dynamically like comets, but lack observed activity, while activated asteroids (AAs) follow typical asteroidal orbits, but have shown dust ejections.

Aims. The monitoring of a set of these objects carried out in 2015 and 2016 is continued using archival images from various observatories and new data from the IMPACTON telescope in Brazil.

Methods. Two techniques were applied to detect activity: (i) surface brightness profiles were compared with those of field stars to identify widening, and (ii) the magnitudes reported in the Minor Planet Center, combined with our observations, were reduced and analyzed to identify abrupt brightness increases as a function of heliocentric distance.

Results. We analyzed the surface brightness profiles of 133 ACOs and 7 AAs. To study the reduced magnitude, we obtained data from the 705 ACOs that were known at the time of the analysis. Together with the data from our previous work, our analysis covered 23% of the total known ACOs; 8 deviated slightly in the surface brightness profile, 6 brightened in the reduced magnitude, and one object is in common in both samples. A very low percentage of objects might show activity (4% of the sample with brightness profiles and <1% in the reduced magnitudes). These results would rule out a slow transition from active to inert. Regarding AAs, 4 showed activity, and 3 of them matched previously reported periods, while the data we analyzed for P/2015 X₆ were obtained 19 days before the first existing activity report. The activity episodes of these objects are very restricted in time and do not always occur in the same region of the orbit.