Search Correlation rotation period versus diameter C/2020 F3 NEOWISE .

Based in next telegram :

ATEL #13945                                                          ATEL #13945

Title:  Rotation of Comet C/2020 F3 (NEOWISE)
Author: Michal Drahus (Jagiellonian University in Krakow), Piotr Guzik
                (Jagiellonian University in Krakow), Andrew Stephens (Gemini Observatory),
                Steve B. Howell (NASA Ames Research Center), Stanislaw Zola (Jagiellonian
                University in Krakow), Mikolaj Sabat (Jagiellonian University in Krakow),

                Daniel E. Reichart (University of North Carolina at Chapel Hill)The observed morphological evolution implies a rotation period of 7.58 +/- 0.03 hr with no obvious temporal changes or deviations from a simple rotation state over the reported time interval. This result is consistent with an earlier value of 7.5 +/- 2.3 hr reported by Masi 2020 (CBET 4816). 

I decided to establish a correlation period of rotation - diameter of the nucleus, it is known that the greater the diameter the rotation of the comet nucleus is slower, and the smaller the diameter the rotation is faster, the average rotation period of many comets is approximately about 15 hours, based on Whipple's work.

In the case of comet C / 2020 F3 NEOWISE the P (rot) = 7.5 hours, analyzing other comets such as 6 P / D'Arrest, P (rot) = 7.2 h (Lowry, Weissman 2007), and a D (km) = 1.6 km (Ferrin 2009), results in a nuclear radius of Rn = 0.8 kms, another comet similar in the period of rotation to F3 NEOWISE is comet 46 P / Wirtanen, with D (km) = 0.9 kms (Fink V. et at. 1997), with a P (rot) = 7.6 h (Ferrin 2009), looking for articles with references, the most interesting is that of Sosa / Fernandez, who establish the following equation 1.0:

log D (km) = 1.5 - 0.13 * H ........... (Sosa & Fdez)

Checking this formula 1.0 I applied it to the previous results, and it was not a good fit, so I decided to apply a new personal adjustment, which is the following 1.1:

log D (km) = 1.3 - 0.13 * H ............... (Navarro)

finding a comet diameter of 0.94 kms, a value that is more in line with reality.

Another new formula that relates the activity index with the gas production rates is the following 1.2:

log Q (C2) / log Q (H2O) = - n ............... (Navarro)

Coefficient of variation of the rate of increase in brightness 1.3:

K = d (n) / d (r)

r heliocentric distance

n rate of increase in brightnes

Update Light Visual Curve C/2020 F3 NEOWISE

New update of the visual light curve of comet NEOWISE, based on 798 observations of the comet, from the COBS database, my analysis includes the calculation of the photometric parameters of the comet before and after perihelion. The first conclusion shows, based on the activity index n, that the comet has been more active at the gas / dust level in the pre-perihelion, with an index of R ^ (- 5.45), in the post-perihelion the comet, has a much lower index or rate of increase in brightness than R ^ (- 4.20), this gives a coefficient of variation of n, based on my personal formula: [Navarro Formula .... K = R ^ (n1- n 2) , K = R ^ (-1.25)] where n1 is the pre-perihelion index and n2 is the post-perihelion index. The post-perihelion adjustment is quite close to the average line that I have calculated, but there is an overestimation of 0.5 to 1.0 magnitudes in the measurements on the general curve. The general formula of the comet is m0 = 7.0 and n = 12.1, later in this blog I hope to refine the final diameter of the NEOWISE comet, as well as the rates of production of water gas and compare them with the real ones.