Cometary Science Newsletter

August 2023
Michael S. P. Kelley (

Refereed Articles

Abstracts of articles in press or recently published. Limited to 3000 characters.

A photometric study of centaurs 29P/Schwassmann-Wachmann and (2060) Chiron

  • Betzler, Alberto S. 1
  1. Centro de Ciência e Tecnologia em Energia e Sustentabilidade, Universidade Federal do Recôncavo da Bahia, Feira de Santana 44085-132, Brazil

This study presents the analysis of forced photometry data in the o and c filters of centaurs 29P/Schwassmann-Wachmann and (2060) Chiron obtained by the ATLAS network between 2015 and 2022. Centaur 29P had 24 outbursts with a median peak brightness of -3.0 and a range of -3.7 mag, regardless of spectral band. Some of these outbursts exhibited an asymmetric light curve with respect to peak brightness, with brightness decreases ranging from -0.22 to -7.6 mag h-1 and durations from 2.8 min to 1.4 d. The slope m of the photometric profile of the coma after/before and during an outburst was ≤1 and >1, respectively, reflecting an increase in brightness at the optocenter of the object. Without the outbursts, 29P has an absolute magnitudes H0 of 9.3 ± 0.2 and 9.10 ± 0.01 in the c and o filters, respectively, and activity indices of n = 11.56 ± 0.08 and 2.1 ± 0.1. Using the Lomb-Scargle periodogram, a periodicity of 0.97 d was found in the c magnitudes after perihelion, probably related to nuclear rotation. The absolute magnitude of Chiron in the HG1G2 system in the o filter is nearly constant between 2017 and 2020, with a weighted mean of 5.35 ± 0.03. In 2021, the brightness increases to H = 4.54 ± 0.03 and decreases to 5.04 ± 0.04 in 2022. This increase in 2021 is not due to outbursts that did not occur during the entire observing campaign, but is related to the increase in opposition effect.

Monthly Notices of the Royal Astronomical Society (Published)

DOI: 10.1093/mnras/stad1616 NASA ADS: 2023MNRAS.523.3678B

Photometric BVR observations of comet C/2012 J1 (Catalina) before and after perihelion

  • Betzler, A. S. 1
  • de Sousa, O. F.2
  1. Centro de Ciência e Tecnologia em Energia e Sustentabilidade, Universidade Federal do Recôncavo da Bahia, Feira de Santana, Brazil
  2. Centro de Formação de Professores, Universidade Federal do Recôncavo da Bahia, Amargosa, Brazil

We analyzed the BVR photometry of comet C/2012 J1 (Catalina) taken between March 2013 and May 2014 with telescopes ranging from 0.20 to 2.0 m aperture in Australia, Europe, and the United States. We found an absolute magnitude in the R-band of H0 = 7.2 ± 0.1 measured with a photometric aperture radius ρ of 42.4 arcsec, corresponding to projected distances in the sky of 7.2 × 10^4-1.5 × 10^5 km. Comet C/2012 J1 (Catalina) shows an asymmetric secular light curve, which is typical for comets. The nucleus has a minimum radius of 3.3 km admitting an albedo of 0.04. The inner coma exhibited radial pulsations before perihelion related to the dust rate proxy Afρ. The Afρ parameter was inversely proportional to the photometric aperture radius ρ because the angular diameter of the coma was small compared with the aperture radii used. The comet had three outbursts with brightness variations between 0.2 and 2.99 magnitudes per event. The median normalized reflectivity gradient S' is 4.4 with an amplitude of 22.9%/100 nm in the spectral range between 440 and 647 nm. The dispersion of the gradient S' means that 20% of the measurements are bluer than the solar color.

Astronomische Nachrichten (Published)

DOI: 10.1002/asna.20220084 NASA ADS: 2023AN....34420084B

Splitting of Long-period Comet C/2018 F4 (PANSTARRS)

  • Hui, M.-T. 1
  • Kelley, M. S. P. 2
  • Hung, D. 3
  • Lister, T. 4
  • Chatelain, J. 4
  • Gomez, E. 5
  • Greenstreet, S. 6
  1. Macau University of Science and Technology, Macau
  2. University of Maryland, College Park, USA
  3. University of Hawai‘i, USA
  4. Las Cumbres Observatory, USA
  5. Las Cumbres Observatory, Cardiff University, UK
  6. University of Washington, USA

Long-period comet C/2018 F4 (PANSTARRS) was observed to show duplicity of its inner region in 2020 September, suggestive of a splitting event. We here present analyses of our observations of the comet taken from the LCO Outbursting Objects Key project and the University of Hawaii 2.2 m telescope after the discovery of the splitting. The two fragments Components A and B, estimated to be ~60 m to 4 km in radius, remained highly similar to each other in terms of brightness, color, and dust morphology throughout our observing campaign from 2020 September to 2021 December. Our fragmentation model yielded that the two components split at a relative speed of 3.00 ± 0.18 m s-1 in 2020 late April, implying a specific energy change of (5.3 ± 2.8) × 103 J kg-1, and that Component B was subjected to a stronger nongravitational acceleration than Component A in both the radial and normal directions of the orbit. The obtained splitting time is broadly consistent with the result from the dust morphology analysis, which further suggested that the dominant dust grains were millimeter-sized and ejected at a speed of ~2 m s-1. We postulate that the pre-split nucleus of the comet consisted of two lobes resembling that of 67P, or that the comet used to be a binary system like main-belt comet 288P. Regardless, we highlight the possibility of using observations of split comets as a feasible manner to study the bilobate shape or binarity fraction of cometary nuclei.

The Astronomical Journal (Published)

DOI: 10.3847/1538-3881/acdc9c NASA ADS: 2023AJ....166...47H arXiv: 2306.03635