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

Martino, S. and Tancredi, G. and Banda-Huarca, M. and Rondón, E. and Camargo, J.I.B. and Licandro, J. and Aguena, M. and Andrade-Oliveira, F. and Arcoverde, P. and Bernardinelli, P.H. and Brooks, D. and Rosell, A.C. and Carretero, J. and da Costa, L.N. and Davis, T.M. and De Vicente, J. and Diehl, H.T. and Doel, P. and Evangelista-Santana, M. and Everett, S. and Frieman, J. and García-Bellido, J. and Gaztanaga, E. and Gruen, D. and Gruendl, R.A. and Hinton, S.R. and Hollowood, D.L. and James, D.J. and Kuehn, K. and Lahav, O. and Marshall, J.L. and Medeiros, H. and Mena-Fernández, J. and Mesquita, F.W. and Michimani, J. and Miquel, R. and Monteiro, F. and Pereira, J.W. and Pieres, A. and Malagón, A.A.P. and Samuroff, S. and Sanchez, E. and Cid, D.S. and Sevilla-Noarbe, I. and Smith, M. and Suchyta, E. and Tarle, G. and Weaverdyck, N. (2025) Monitoring of asteroids in cometary orbits and activated asteroids through archival images and new observations. Astronomy and Astrophysics, 698: A117. ISSN 1432-0746

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.