Two Apparent Outbursts of Comet 24P/Schaumasse
ATel #17799; Michael S. P. Kelley (Univ. Maryland), Zhong-Yi Lin (National Central Univ. Taiwan), Carrie Holt (Las Cumbres Observatory), on behalf of the Zwicky Transient Facility Collaboration, and the LCO Outbursting Objects Key Project
on 13 May 2026; 18:49 UT
Credential Certification: Carrie Holt (cholt@lco.global)
We report the discovery and follow-up of two small (-0.7 and -1.1 mag) apparent outbursts of comet 24P/Schaumasse. The first event occurred between two Zwicky Transient Facility (ZTF; Bellm et al. 2019, PASP 131, a8002) images taken 2026 Mar 19 11:29 and Mar 20 10:22 UTC, and the second between 2026 May 10 10:59 and May 11 06:25 UTC. The comet was 1.50 and 1.92 au from the Sun, respectively, and 0.66 and 0.94 au from the Earth. Follow-up observations with the Las Cumbres Observatory global network of 1-m telescopes were used to confirm each event. Photometry is reported in the table below. As a consequence of the presence of strong and variable emission from gas and differences in the filters used, calibration to the PS1 magnitude system was not sufficient enough to make the photometry uniform. Regardless, we provide scale factors to make a consistent r-band lightcurve: zg-zr = 0.49 mag, zr-zi = 0.18 mag, and g'-zr = 0.42 mag, r'-zr = -0.05 mag, zr-i' = 0.27 mag, where zg, zr, and zi are the ZTF g, r, and i-band filters, and g', r', and i' are the SDSS g', r', and i' filters used at LCO.
Following the discovery, we reviewed Lulin Observatory photometry around the time of the second outburst taken with a 0.4-m telescope equipped with a CCD and R-band filter. The data narrow the second outburst's timing to no earlier than 2026 May 10 16:38 UTC. Photometry measured in a 5" radius aperture and calibrated to PS1 r-band are included below. No offset is needed in comparison to the ZTF r-band photometry.
Date (UTC) Source Filter m unc
---------------- ------ ------ ----- ----
2026-03-18 10:08 ZTF zr 15.20 0.02
2026-03-18 10:46 ZTF zi 15.02 0.02
2026-03-18 11:56 ZTF zg 15.74 0.03
2026-03-18 11:57 ZTF zg 15.73 0.03
2026-03-19 10:19 ZTF zi 15.03 0.02
2026-03-19 10:47 ZTF zg 15.67 0.03
2026-03-19 10:56 ZTF zi 15.06 0.02
2026-03-19 11:29 ZTF zr 15.19 0.02
2026-03-20 10:22 ZTF zg 14.88 0.03
2026-03-20 11:29 ZTF zr 14.48 0.02
2026-03-20 12:12 ZTF zi 14.32 0.02
2026-03-21 06:01 LCO g' 15.28 0.02
2026-03-21 06:01 LCO r' 14.85 0.02
2026-03-21 06:02 LCO i' 14.65 0.03
2026-03-21 09:45 ZTF zg 15.37 0.03
2026-03-21 11:26 ZTF zr 14.91 0.02
2026-03-21 11:30 ZTF zr 14.91 0.02
2026-05-09 07:08 ZTF zr 16.50 0.03
2026-05-09 08:00 ZTF zi 16.34 0.03
2026-05-09 08:35 ZTF zg 17.02 0.03
2026-05-10 07:05 ZTF zg 17.05 0.03
2026-05-10 08:38 ZTF zi 16.37 0.03
2026-05-10 10:59 ZTF zr 16.55 0.03
2026-05-10 16:27 Lulin R 16.54 0.02
2026-05-10 16:32 Lulin R 16.57 0.02
2026-05-10 16:38 Lulin R 16.59 0.02
2026-05-11 06:25 ZTF zi 15.29 0.02
2026-05-11 09:52 ZTF zg 16.11 0.03
2026-05-11 16:39 Lulin R 15.75 0.02
2026-05-11 16:45 Lulin R 15.74 0.02
2026-05-11 16:50 Lulin R 19.38 0.10
2026-05-11 22:13 LCO r' 15.91 0.02
2026-05-11 22:13 LCO g' 16.43 0.02
-----------------------------------------
filter: observed filter
m : PS1 g/r/i apparent magnitude
unc : uncertainty on m
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.
