Comet 29P/Schwassmann-Wachmann 1 dust environment from photometric observation at the SOAR Telescope

Abstract

We report photometric observations of c omet 29P/Schwassmann-Wachmann 1 made on August 12, 2016 with the b road-band B, V, R a nd I f ilters a nd the SOAR 4 .1-meter telescope (Chile). We f ind the c omet a ctive a t that time. E nhanced i mages obtained i n a ll f ilters reveal three radial f eatures i n the 29P/ Schwassmann-Wachmann 1 c oma, regardless of the i mage-processing a lgorithm. Using a h igh-resolution spectrum of c omet 29P/Schwassmann-Wachmann 1 reported b y I vanova e t a l. (2018) on the same d ate, we e stimate the relative c on-tribution of the g aseous e mission a nd the c ontinuum to the total response measured with our b roadband B a nd V f ilters. The g aseous-emission c ontribution a ppears to b e v ery small, 2.5%. We c ompute the d ust production Afρ in 29P/ Schwassmann-Wachmann 1 f or the f our f ilters a nd f ind i ts g rowth with the wavelength, f rom 3 ,393 ± 93 c m i n the B f ilter to 8,561 ± 236 c m i n the I filter. We model the c olor slope of d ust i n Comet 29P/Schwassmann-Wachmann 1 u sing a gglomerated d ebris particles. S imultaneous a nalysis of the c olor slope in the B-R a nd R-I pairs suggests a single d ominant c hemical species of 29P/Schwassmann-Wachmann 1 d ust particles c onsisting of F e-Mg silicates a nd obeying a power-law size d istribution with i ndex n ≈ 2.55. This c onclusion i s c onsistent with the previous thermal-emission study of 29P/Schwassmann-Wachmann 1.

Resolving color differences of comet 41P/Tuttle-Giacobini-Kresák

“…We used the results of computations at λ = 0.45 and 0.644 µm to model observations in the B and R filters of the Johnson-Cousins photometric system and of the R and I filters. This analysis of multiband photometric observations of Comet 29P/Schwassmann-Wachmann 1 is similar to that of Picazzio et al (2019). The refractive index of the agglomerated debris particles in the model B, R, and I filters is assigned to the values adapted from Dorschner et al (1995) at the closest wavelength, that is, m B = 1.649 + 0.0105i, m R = 1.629 + 0.0032i, and m I = 1.619 + 0.0027i.…”

Imaging polarimetry and photometry of comet 21P/Giacobini-Zinner

“…In addition, we demonstrate their fit (black solid line) that was obtained with a twocomponent model inferred by Zubko et al (2016). Although this particular modeling result cannot be extrapolated for the case of 21P/G-Z, because comet C/1996 B2 (Hyakutake) had a persistent red polarimetric color that does not hold for 21P/G-Z, the two-component framework has proven capable of reproducing the photometric and polarimetric observations of numerous comets (e.g., Zubko et al 2014;2015;Ivanova et al 2017;Picazzio et al 2019;Luk'yanyk et al 2019) and are consistent with in situ findings (e.g., Zubko et al 2012).…”

“…This model may reproduce the vast majority of polarimetric observations of comets by fitting only a single free parameter, the volume ratio of the weakly absorbing component to the highly absorbing component (Zubko et al 2016). It is worth noting that the two-component model can reproduce the phase function and photometric color of dust in comets (Zubko et al 2014;Ivanova et al 2017;Picazzio et al 2019;Luk'yanyk et al 2019), as well as significant spatial variations of linear polarization observed in some comets (Zubko et al 2012;2015). Observations of some rare comets suggest domination of only one type of dust in their coma, at least over short time period (e.g., Picazzio et al 2019).…”

Rapid variations of dust colour in comet 41P/Tuttle–Giacobini–Kresák

“…This was checked, for instance, by integrating high-resolution cometary spectra in visible with and without gaseous-emission lines taken into account. The difference between those two types of spectral integrations exceeds only a few percent (e.g., Jewitt et al 1982;Picazzio et al 2019), suggesting an extremely low contribution of the gaseous emission into the flux measured with wideband filters. Interestingly, this equally holds for longand short-period comets.…”