Bibcode
Licandro, J.; de la Fuente Marcos, C.; de la Fuente Marcos, R.; de León, J.; Serra-Ricart, M.; Cabrera-Lavers, A.
Bibliographical reference
Astronomy and Astrophysics, Volume 625, id.A133, 6 pp.
Advertised on:
5
2019
Journal
Citations
16
Refereed citations
11
Description
Context. The population of comets hosted by the Oort cloud is
heterogeneous. Most studies in this area have focused on highly active
objects, those with small perihelion distances or examples of objects
with peculiar physical properties and/or unusual chemical compositions.
This may have produced a biased sample of Oort cloud comets in which the
most common objects may be rare, particularly those with perihelia well
beyond the orbit of the Earth. Within this context, the known Oort cloud
comets may not be representative of the full sample meaning that our
current knowledge of the appearance of the average Oort cloud comet may
not be accurate. Comet C/2018 F4 (PANSTARRS) is an object of interest in
this regard. Aims: Here, we study the spectral properties in the
visible region and the cometary activity of C/2018 F4, and we also
explore its orbital evolution with the aim of understanding its origin
within the context of known minor bodies moving along nearly parabolic
or hyperbolic paths. Methods: We present observations obtained
with the 10.4 m Gran Telescopio Canarias (GTC) that we use to derive the
spectral class and visible slope of C/2018 F4 as well as to characterise
its level of cometary activity. Direct N-body simulations are carried
out to explore its orbital evolution. Results: The absolute
magnitude of C/2018 F4 is Hr > 13.62 ± 0.04 which
puts a strong limit on its diameter, D < 10.4 km, assuming a
pV = 0.04 cometary-like value of the albedo. The object
presents a conspicuous coma, with a level of activity comparable to
those of other comets observed at similar heliocentric distances. Comet
C/2018 F4 has a visible spectrum consistent with that of an X-type
asteroid, and has a spectral slope S' = 4.0 ± 1.0%/1000 Å
and no evidence of hydration. The spectrum matches those of well-studied
primitive asteroids and comets. The analysis of its dynamical evolution
prior to discovery suggests that C/2018 F4 is not of extrasolar origin.
Conclusions: Although the present-day heliocentric orbit of
C/2018 F4 is slightly hyperbolic, both its observational properties and
past orbital evolution are consistent with those of a typical
dynamically old comet with an origin in the Oort cloud.
Based on observations made with the GTC telescope, in the Spanish
Observatorio del Roque de los Muchachos of the Instituto de
Astrofísica de Canarias, under Director's Discretionary Time
(program ID GTC2018-096).
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Minor Bodies of the Solar System
This project studies the physical and compositional properties of the so-called minor bodies of the Solar System, that includes asteroids, icy objects, and comets. Of special interest are the trans-neptunian objects (TNOs), including those considered the most distant objects detected so far (Extreme-TNOs or ETNOs); the comets and the comet-asteroid
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