Secular light curves of periodic comets observed by SWAN/SOHO

ABSTRACT In this work we study the correlation equation between the water production rate and the relative magnitude for 52 comets observed by SWAN/SOHO, with a great increase in respect to previous works. We studied the secular light curve of the 16 periodic comets, using an envelope polynomial function fit, which allows the determination of the turn-on and turn-off points, the nuclear and coma magnitude, the amplitude of the secular light curve and the relative age. Our analyses indicate that the comets 81P and 96P are the youngest and oldest, respectively. In order to find physical parameters such as the percentage of active region and the orientation of spin axis, we modelled the secular light curve of the periodic comets using a simple cometary sublimation model. We found that 55P and 96P are the comets with the greatest and smallest active regions in our work. Lastly, we studied the correlation between orbital and physical parameters derived through the secular light curves. We found that the relative age of the comets ($P_{\rm AGE}$) has a strong correlation with the inverse of the semimajor axis, the active region, and the albedo, with an intermediate correlation with the diameter. According to these results, dead or extinct comets are not the most probable final states of a comet, as is currently thought. The comets 55P and 96P do not follow the correlation, which could indicate that these objects migrated from the inner to the outer region of the Solar system.