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First Discovery of a Small Near Earth Asteroid with ZTF (2018 CL)

ATel #11274; Quan-Zhi Ye (Caltech/IPAC) on behalf of the ZTF and GROWTH teams
on 8 Feb 2018; 02:15 UT
Credential Certification: Matthew Graham (mjg@caltech.edu)

Subjects: Optical, Asteroid, Near-Earth Object

Quan-Zhi Ye (Caltech/IPAC) on behalf of the Zwicky Transient Facility (ZTF) and the Global Relay of Observatories Watching Transients Happen (GROWTH) announces the first detection and follow-up of a Near Earth Asteroid (NEA) detected by the new small NEA detection pipeline of the ZTF/GROWTH projects (developed and running at IPAC).

ZTF has recently begun preliminary science observations and includes a dedicated pipeline for detecting small (< 150 meter) trailed NEAs. Once a detection is made and submitted to the Minor Planet Center (MPC), follow-up can be initiated at observatories around the world, including those involved with the GROWTH project. Same night or next night observations are highly advantageous as trailed asteroids have high angular rates, on order of 1"/second or larger, and therefore are only observable for a few days.

On the first night of operation (5 Feb 2018) the ZTF fast response small NEA pipeline detected a bright trailed object in 4 r-band images taken over ~2 hours. This yielded 8 endpoint observations of the object, which were submitted to the MPC. Follow-up observations were made by other observatories (MPC circular: MPEC 2018-C23) and the object was designated as 2018 CL by the MPC. 2018 CL was first detected at a distance of about 3 times the Earth-Moon distance and had a closest approach of about 2.4 Earth-Moon distances on Feb 6 4:09 UTC. The NEA had a measured H magnitude of 25.5, and a V magnitude at closest approach of brighter than 15. The size of the asteroid is nominally 50 meters assuming an albedo of 5%. Fifty-six observations of the object were made worldwide in less than 20 hours, providing a well determined orbit. It is a probable Aten asteroid. Low-resolution spectroscopic observations were made the night following the initial detection, 6 Feb 2018, with the robotic Palomar 60” telescope using the SEDM instrument (resolution R~100).

We acknowledge the valuable and timely follow-up observations of 2018 CL by astronomers around the world. Additional follow-up observations with higher spectral resolution are encouraged before the asteroid is too far away from the earth.

ZTF is a project led by PI S. R. Kulkarni at the California Institute of Technology, (see ATEL #11266). GROWTH is led by PI Mansi Kasliwal at the California Institute of Technology. This work was supported by the GROWTH project funded by the National Science Foundation under PIRE Grant No 1545949. ZTF acknowledges the generous support of the National Science Foundation under AST MSIP Grant No 1440341.