Time-series and Phase-curve Photometry of the Episodically Active Asteroid (6478) Gault in a Quiescent State Using APO, GROWTH, P200, and ZTF

Josiah N. Purdum, Zhong Yi Lin, Bryce T. Bolin, Kritti Sharma, Philip I. Choi, Varun Bhalerao, Josef Hanuš, Harsh Kumar, Robert Quimby, Joannes C. Van Roestel, Chengxing Zhai, Yanga R. Fernandez, Carey M. Lisse, Dennis Bodewits, Christoffer Fremling, Nathan Ryan Golovich, Chen Yen Hsu, Wing Huen Ip, Chow Choong Ngeow, Navtej S. SainiMichael Shao, Yuhan Yao, Tomás Ahumada, Shreya Anand, Igor Andreoni, Kevin B. Burdge, Rick Burruss, Chan Kao Chang, Chris M. Copperwheat, Michael Coughlin, Kishalay De, Richard Dekany, Alexandre Delacroix, Andrew Drake, Dmitry Duev, Matthew Graham, David Hale, Erik C. Kool, Mansi M. Kasliwal, Iva S. Kostadinova, Shrinivas R. Kulkarni, Russ R. Laher, Ashish Mahabal, Frank J. Masci, Przemyslaw J. Mróz, James D. Neill, Reed Riddle, Hector Rodriguez, Roger M. Smith, Richard Walters, Lin Yan, Jeffry Zolkower

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10 Scopus citations


We observed the episodically active asteroid (6478) Gault in 2020 with multiple telescopes in Asia and North America and found that it is no longer active after its recent outbursts at the end of 2018 and the start of 2019. The inactivity during this apparition allowed us to measure the absolute magnitude of Gault of H r = 14.63 ± 0.02, G r = 0.21 ± 0.02 from our secular phase-curve observations. In addition, we were able to constrain Gault's rotation period using time-series photometric lightcurves taken over 17 hr on multiple days in 2020 August, September, and October. The photometric lightcurves have a repeating ≲0.05 mag feature suggesting that (6478) Gault has a rotation period of ∼2.5 hr and may have a semispherical or top-like shape, much like the near-Earth asteroids Ryugu and Bennu. The rotation period of ∼2.5 hr is near the expected critical rotation period for an asteroid with the physical properties of (6478) Gault, suggesting that its activity observed over multiple epochs is due to surface mass shedding from its fast rotation spin-up by the Yarkovsky-O'Keefe-Radzievskii-Paddack effect.

Original languageEnglish
Article numberL35
JournalAstrophysical Journal Letters
Issue number2
StatePublished - 1 Apr 2021


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