AstroNote 2020-199

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DRAFT
2020-10-21 18:58:06
Type: Object/s-Data/Analysis
Observations of ZTF20acigmel / AT2020xnd, a distant fast optical transient similar to AT2018cow
Authors: Daniel A. Perley (LJMU), Anna Ho (UC Berkeley), Christoffer Fremling (Caltech), Yuhan Yao (Caltech)
Source Group: ZTF
Abstract:
We report on the fast-fading, moderate-redshift AT2018cow-like transient AT2020xnd, discovered by ZTF on Oct 12. The magnitude of the transient is currently r~21.3 mag.

During the night of 2020 Oct 12 (UT), the Zwicky Transient Facility (ZTF; Kulkarni et al., ATEL #11266; Bellm et al. 2019a, PASP, 131, 18002) detected the new optical transient ZTF20acigmel / AT2020xnd.  The ZTF light curve rose to a peak and then began a rapid decline within 4 days of discovery.  Follow-up observations with the Liverpool Telescope showed evidence for a very blue color (u-g = -0.4 mag AB) during the decline phase.  Spectroscopy at Keck Observatory confirmed the source to be a featureless and extremely luminous transient at intermediate redshift (z=0.244, peak absolute magnitude -20.9).  A summary of these initial observations is presented in ATEL #14105.

We report here further follow-up photometry with the Palomar 60-inch telescope (using the Rainbow Camera on the SED Machine) showing a continued rapid decay in flux.   As of JD 2459143.6030 we measure r = 21.29 +/- 0.14 mag.

Follow-up is continuing but is hampered by poor weather at La Palma and the rapid fading of the source.  Deep optical imaging over the coming 1-2 weeks would be useful to confirm or rule out the presence of a radioactively-powered underlying supernova, which was not observed in AT2018cow (Perley et al. 2019, MNRAS, 484, 1031).

ZTF is a project led by PI S. R. Kulkarni at Caltech, and includes IPAC; WIS, Israel; OKC, Sweden; JSI/UMd, USA; UW,USA; DESY, Germany; NRC, Taiwan; UW Milwaukee, USA and LANL USA. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. Alert distribution service provided by DIRAC@UW. Alert filtering is being undertaken by the GROWTH marshal system, supported by NSF PIRE grant 1545949.  The SED Machine is based upon work supported by the NSF under grant 1106171.

Show current TNS values
CatalogNameReported RAReported DECReported Obj-TypeReported RedshiftHost NameHost RedshiftRemarksTNS RATNS DECTNS Obj-TypeTNS Redshift
TNS2020xnd [ZTF20acigmel]22:20:02.030-02:50:25.30Other0.244222:20:02.030-02:50:25.30
TNS2018cow [ATLAS18qqn]16:16:00.220+22:16:04.9116:16:00.220+22:16:04.91SN Ic-BL