TRAPPIST production rates of comets 161P/Hartley-IRAS, 10P/Tempel 2 and 220P/McNaught
ATel #18116; E. Jehin, S. Hmiddouch, J. Manfroid, K. Aravind, E. Blond Hanten (STAR Institute, University of Liege)
on 22 Oct 2026; 09:33 UT
Credential Certification: Emmanuel Jehin (ejehin@uliege.be)
The author reports that they obtained, using the TRAPPIST-North (Z53) telescope located in Morocco, observations of comets 161P, 10P and 220P on the nights of October 19 and 20. They used broadband and cometary HB narrow-band filters (Farnham et al. 2000, Jehin et al. 2011) and computed preliminary production rates from extracted profiles at 10.000 km using a Haser Model (Vp=Vd=1.0 km/s) (Haser 1957). Zero Points were determined on close nights using standard stars. The proxy to the dust production rate A(0)f(rho) was estimated by profile fitting at 10.000 km (A'Hearn et al. 1984) and corrected for the phase angle (Schleicher 2007).
161P/Hartley-IRAS
Date UT=2026-10-20, rh= 1.37 au, Delta= 0.71 au, DT= -37 d
Q(OH)= 2.49 +/- 0.94 E27 s-1
Q(CN)= 5.81 +/- 0.57 E24 s-1
Q(C2)= 6.25 +/- 1.08 E24 s-1
Q(C3)= 1.59 +/- 0.49 E24 s-1
A(0)fp(BC)= 52.70 +/- 16.69 cm
A(0)fp(RC)= 61.38 +/- 10.99 cm
A(0)fp(R)= 90.21 +/- 14.49 cm
161P is now about one month from perihelion and all the species are detected but the comet activity is still rather low. 161P has a typical composition log[Q(C2)/Q(CN)] = +0.03 +/- 0.09 and dust/gas ratio of -22.8 (A'Hearn et al. 1995).
10P/Tempel 2
Date UT=2026-10-20, rh= 1.64 au, Delta= 0.84 au, DT= +80 d
Q(CN)= 9.63 +/- 1.09 E24 s-1
Q(C2)= 1.01 +/- 0.17 E25 s-1
A(0)fp(BC)= 188.18 +/- 2.61 cm
A(0)fp(RC)= 236.42 +/- 1.10 cm
A(0)fp(R)= 222.11 +/- 2.40 cm
The comet is pretty low on the horizon from Morocco with an airmass always higher than 2.0. About 3 months after perihelion we do not detect anymore OH. 10P has a typical composition log[Q(C2)/Q(CN)] = +0.02 +/- 0.09 and it is on the dust rich side, with a dust/gas ratio of -22.6 (A'Hearn et al. 1995).
220P/McNaught
Date UT=2026-10-20, rh= 1.96 au, Delta= 1.02 au, DT= +128 d
Q(CN)= 1.33 +/- 0.37 E24 s-1
Q(C2)= 2.50 +/- 0.71 E24 s-1
A(0)fp(BC)= 52.65 +/- 9.52 cm
A(0)fp(RC)= 85.44 +/- 7.39 cm
A(0)fp(R)= 56.36 +/- 1.76 cm
The comet displays in R band a short and bright linear dust tail since the first outburst. The comet is crossing rich star fields and the C2 and RC images have been somewhat contaminated by a star.
Notations: rh= heliocentric distance (in au), Delta=geocentric distance (in au), DT= Time to perihelion. OH, NH, C3, CN, and C2 are the HB gaseous narrowband filters for the corresponding species, and BC, GC, and RC are the blue, green and red dust continuum filters (Farnham et al. 2000).
Acknowledgments: TRAPPIST is a project funded by the Belgian F.R.S.-FNRS under grant PDR T.0120.21 and the University of Liege. Observations were carried out from the ESO La Silla Paranal and Oukaimeden Observatory. We thank NASA, David Schleicher, and the Lowell Observatory for the loan of the HB comet filters. https://www.trappist.uliege.be/
