Dust Properties of distant comet C/2013 V4 (Catalina) at heliocentric distances beyond 5 au

Comets are considered to be important remnants of the early Solar System. According to prevailing theories, a substantial fraction of planetesimals was scattered into the Oort cloud during the epoch of giant planet formation. Subsequent gravitational perturbations, including stellar encounters and Galactic tides, can alter their orbits, injecting them into the inner Solar System or, in some cases, placing them on hyperbolic trajectories. Hyperbolic comets and dynamically new Oort cloud objects are of particular interest, especially during their inbound phase, when their surfaces are expected to be minimally processed by solar radiation. Such distant comets represent valuable analogues of pristine material and are considered prime targets for future space missions, including Comet Interceptor. Since these objects are observable only for a limited time and often at large heliocentric distances, it is essential to obtain comprehensive observational datasets already at early stages of activity. In this study, we present spectroscopic, polarimetric, and photometric observations of the hyperbolic comet C/2013 V4 (LINEAR) (hereafter 2013V4). The comet follows a hyperbolic orbit with eccentricity e = 1.0026, perihelion distance q = 5.19 au, and inclination i = 67.85°, providing a valuable opportunity to investigate the physical properties and activity of distant comets that may preserve relatively unprocessed material.

We observed comet 2013V4 on two observing runs, on November 6, 2015, and April 6, 2016, using the 6-m BTA telescope SAO. The comet was located at heliocentric distances of 5.19–5.36 au and geocentric distances of 4.61–5.62 au, with phase angles of 9.4°–10.1°. Photometric imaging was obtained during both runs using g-sdss and r-sdss filters. Long-slit spectroscopic observations were carried out with the VPHG1200@540 grism, covering the spectral range 3600–7070 Å.  Spectroscopy post-monitoring shows no significant gas emissions, allowing a focus on the dust environment. Polarimetric observations were performed on November 6, 2015, using the R filter. The phase angle during the polarimetric measurements was 9.4°. Using our photometric and polarimetric observations of this comet, we attempted to model the physical characteristics of its dust environment. We utilized the state-of-the-art modeling tools such as Fast superposition T-matrix method [1] and Radiative transfer with reciprocal transactions [2], in combination with a dynamical dust model, to characterize dust properties and their evolution in the coma. Morphological analysis of the images showed a compact dust coma with a slight asymmetry and a long tail. No prominent jet-like structures are clearly detected. The average dust activity level Afρ is more than 1000 cm, consistent with other distant comets.

 [1] Markkanen J., Yuffa A. “Fast superposition T-matrix solution for clusters with arbitrarily-shaped constituent particles”, JQSRT 189, pp. 181-188 (2017)

[2] Muinonen et al. “Multiple scattering of light in discrete random media using incoherent interactions”, Opt. Lett. 43, pp.683-686 (2018)

 Acknowledgments

 The research of Leonid Shakun and Oleksandra Ivanova is supported by the Slovak Research and Development Agency under Contract No. APVV-24-0076 and the grant of the Slovak Academy of Sciences (grant Vega No. 2/0067/26); Oleksandra Ivanova and Johannes Markkanen are supported by grants for projects under the Mobility Program DAAD-SAS-2024-02 no. 57752921. The research of Igor Luk’yanyk was supported by the projects of the Ministry of Education and Science of Ukraine No. 0125U002319.