Three Outbursts of Comet C/2020 R4 (ATLAS)
ATel #14618; Michael S. P. Kelley (U. Maryland), Tim Lister (Las Cumbres Observatory), Kritti Sharma (IITB), Harsh Kumar (IITB), Varun Bhalerao (IITB), G. C. Anupama (IIA), Sudhanshu Barway (IIA) on behalf of the Zwicky Transient Facility Collaboration, LCO Outbursting Objects Key Project, and GROWTH India Collaboration
on 10 May 2021; 18:45 UT
Credential Certification: Tim Lister (tlister@lco.global)
We report three apparent outbursts of comet C/2020 R4 (ATLAS) in Zwicky Transient Facility (ZTF; Bellm et al. 2019, PASP, 131, a8002), GROWTH India Telescope, and Las Cumbres Observatory (1-m telescope at McDonald Observatory) data. Photometry within 5,000 km radius apertures starting on 2021 April 18 (UTC) are given below, along with heliocentric distance (rh), and observer-comet distance (Delta). The aperture size, 14" at Delta=0.5 au, is chosen to reduce the effects of comet trailing during the 30-s sidereally-tracked ZTF exposures (peak trail length is 5.6"). We find three apparent outbursts occurring between 2021 April 20.384 and 24.299 UTC (Δg = 1.00 +/- 0.03 mag, Δr = -1.03 +/- 0.03 mag), April 25.357 and 27.466 (Δg = -1.14 +/- 0.05 mag), and May 05.313 and 06.206 (Δg = -0.50 +/- 0.04 mag, Δr = -0.60 +/- 0.05 mag). All events are confirmed by inspection of the coma morphology. The light curve of the third event faded rapidly, returning to nominal brightness in 1 day. This suggests an ejecta expansion speed of >=60 m/s, and that the first event may have been much larger.
Continued study of this comet is encouraged in case of more outbursts, development of fragments, or disintegration.
Based on observations obtained with the Samuel Oschin Telescope 48-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-2034437 and a collaboration including Caltech, IPAC, Weizmann Institute for Science, Oskar Klein Center at Stockholm University, University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, TANGO Consortium of Taiwan, University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, and IN2P3, France. Operations are conducted by COO, IPAC, and UW.
This work makes use of observations from the Las Cumbres Observatory global telescope network.
The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7 degree field of view, set up by the Indian Institute of Astrophysics and the Indian Institute of Technology Bombay with support from the Indo-US Science and Technology Forum (IUSSTF) and the Science and Engineering Research Board (SERB) of the Department of Science and Technology (DST), Government of India (https://sites.google.com/view/growthindia/). It is located at the Indian Astronomical Observatory (Hanle), operated by the Indian Institute of Astrophysics (IIA).
Date Tel rh Delta m m unc
-------------- --- ----- ----- ----- -----
-- r --
2021-04-18.436 ZTF 1.293 0.498 13.50 0.02
2021-04-20.384 ZTF 1.312 0.477 13.42 0.02
2021-04-24.349 ZTF 1.352 0.465 12.42 0.02
2021-04-25.357 ZTF 1.362 0.469 12.58 0.03
2021-04-27.466 ZTF 1.384 0.486 11.44 0.04
2021-04-30.208 ZTF 1.413 0.526 12.70 0.02
2021-05-01.271 ZTF 1.424 0.545 13.03 0.03
2021-05-04.326 ZTF 1.457 0.613 13.60 0.04
2021-05-05.238 ZTF 1.467 0.635 13.75 0.03
2021-05-06.226 ZTF 1.478 0.661 13.25 0.02
2021-05-07.302 ZTF 1.489 0.690 13.84 0.03
-- g --
2021-04-18.467 ZTF 1.294 0.498 13.20 0.02
2021-04-20.342 ZTF 1.312 0.477 13.11 0.02
2021-04-24.299 ZTF 1.351 0.465 12.08 0.02
2021-04-25.277 ZTF 1.361 0.468 12.21 0.02
2021-04-30.277 ZTF 1.413 0.527 12.27 0.03
2021-05-01.837 GIT 1.430 0.557 12.79 0.02
2021-05-02.711 GIT 1.439 0.575 12.88 0.03
2021-05-02.835 GIT 1.441 0.578 12.92 0.02
2021-05-03.368 LCO 1.447 0.590 13.06 0.03
2021-05-04.287 ZTF 1.456 0.612 13.31 0.02
2021-05-05.276 LCO 1.467 0.636 13.25 0.06
2021-05-05.313 ZTF 1.468 0.637 13.30 0.03
2021-05-06.206 LCO 1.477 0.660 12.70 0.04
2021-05-06.301 ZTF 1.478 0.663 12.89 0.02
2021-05-06.608 GIT 1.482 0.671 13.06 0.02
2021-05-06.734 GIT 1.483 0.674 13.11 0.02
2021-05-06.787 GIT 1.484 0.676 13.12 0.04
2021-05-07.212 ZTF 1.488 0.687 13.37 0.02
