Detection of a cometary object near C/2017 O1 (ASAS-SN) in HST images
ATel #16264; Federico Manzini; Virginio Oldani (Stazione Astronomica di Sozzago, Italy); Paolo Ochner (Padova University, Italy); Luigi R. Bedin (INAF-OAPd, National Institute of Astrophysics - Padova Astronomical Observatory, Italy); Andrea Reguitti (INAF-OAB, Brera Astronomical Observatory, Italy)
on 1 Oct 2023; 16:15 UT
Credential Certification: Andrea Reguitti (andreareguitti@gmail.com)
During an analytical review program of all comet images taken by the Hubble Space Telescope (HST),
F. Manzini found the presence of a second cometary object on seven images of Dec 12.01, 2017 (one orbit)
covering the field of comet C/2017 O1 (ASASSN), taken with the F110W and F350LP filters (Figure 1 and 2)
in the context of proposal 15406 (P.I. K. Meech - University of Hawaii).
The object appears to show a motion compatible and almost similar to that of the main nucleus of C/2017
O1, maintaining an average distance of 35.90+/-0.04 arcsec. Deeper analyses are in progress to observe
whether there is a differential movement between the two bodies.
It is likely that this second cometary body is directly linked to the main nucleus and due to a splitting
or ejection following a previous outburst.
Images taken by HST in two orbits on Feb 13 and 19, 2018 with the same filters do not show other
cometary objects in the field, except C/2017 O1.
C/2017 O1 (ASASSN) was first discovered by the 'All Sky Automated Survey for SuperNovae' (ASAS-SN) at
Cerro Tololo, Chile on July 19.32, 2017.
In the discovery images, C/2017 O1 had a V band magnitude of 15.3.
ASAS-SN North unit re-observed the comet 3 days after discovery and found that C/2017 O1 brightened
to V band 11.9 magnitude. (ATel #10597).
The comet experienced an increase of >1 magnitude between July 28 and 29.
In the same period the Af(rho) value almost doubled from 218 cm to 417 cm, at a radius of 10.000 km
(https://astronomie.be/erik.bryssinck/c2017o1_20170728.html).
Starting from mid-November 2017 the comet's brightness decreased rapidly, reaching mag 13.5-14.0 at the
end of January 2018.
Figures and extra material are available at:
Figures and animations
