Two Outbursts of Comet 29P/Schwassmann-Wachmann 1
ATel #14543; Michael S. P. Kelley (U. Maryland), Kritti Sharma (IITB), Harsh Kumar (IITB), Varun Bhalerao (IITB), G. C. Anupama (IIA), Sudhanshu Barway (IIA) on behalf of the Zwicky Transient Facility and GROWTH India Collaborations
on 12 Apr 2021; 23:12 UT
Distributed as an Instant Email Notice Comets
Credential Certification: Bryce Bolin (bolin.astro@gmail.com)
Subjects: Optical, Comet, Planet (minor)
We report on observations of two outbursts of comet 29P/Schwassmann-Wachmann 1 based on SDSS r'- and ZTF r-band images using the GROWTH India Telescope (GIT) and Zwicky Transient Facility (ZTF; Bellm et al. 2019, PASP, 131, a8002). Nightly averaged photometry of comet 29P was measured within circular apertures of radius 5.7" and calibrated to the PS1 magnitude system. The data are tabulated below along with heliocentric distance (rh), observer-comet distance (delta), and point-to-point variation in magnitude (dm).
The first event is small, observed as a change in apparent brightness from r=17.00 +/- 0.03 to 16.80 +/- 0.03 mag between 2021-03-23.128 and 25.129 UTC, indicating an outburst strength of -0.20 +/- 0.04 mag. The outburst is clearly seen as a compact source in images on Mar 25 and 29, after subtracting the image taken on Mar 23.
The second outburst was observed with GIT and ZTF. The combined photometry show the coma near quiescence with a brightness of r=16.98 +/- 0.06 and 17.17 +/- 0.07 mag on 2021 Mar 31.148 and 31.602 UTC, respectively. By our next epoch of photometry, on Apr 01.604 UTC, the comet had brightened to r=15.70 +/- 0.05 mag, indicating an outburst strength of -1.38 +/- 0.07 mag.
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, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, and IN2P3, France. Operations are conducted by COO, IPAC, and UW.
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 dm
UTC au au mag mag mag
-------------- --- ----- ----- ----- ----- -----
2021-03-23.128 ZTF 5.866 6.526 17.00 0.03 0.00
2021-03-25.129 ZTF 5.867 6.549 16.80 0.03 -0.20
2021-03-27.596 GIT 5.868 6.576 16.82 0.04 0.02
2021-03-29.131 ZTF 5.868 6.592 16.83 0.03 0.01
2021-03-30.131 ZTF 5.868 6.603 16.88 0.02 0.05
2021-03-31.148 ZTF 5.868 6.613 16.98 0.06 0.11
2021-03-31.602 GIT 5.869 6.618 17.17 0.07 0.19
2021-04-01.604 GIT 5.869 6.628 15.70 0.05 -1.47
2021-04-02.133 ZTF 5.869 6.633 15.66 0.02 -0.04
2021-04-02.595 GIT 5.869 6.638 15.75 0.01 0.09
2021-04-03.596 GIT 5.869 6.648 15.77 0.01 0.02
2021-04-04.134 ZTF 5.869 6.653 15.77 0.02 0.00
2021-04-05.135 ZTF 5.870 6.662 15.94 0.03 0.17
2021-04-06.135 ZTF 5.870 6.672 16.06 0.02 0.12
2021-04-06.598 GIT 5.870 6.676 16.22 0.06 0.16
2021-04-07.597 GIT 5.870 6.685 16.32 0.07 0.10
