DRAFT
2026-07-30 17:52:52
Type: Object/s-Discovery/Classification
Bibcode: 2026TNSAN.232....1F
ZTF discovery of a fast and red transient AT2026wki/ZTF26abkoycd
Authors: James Freeburn, Anirudh Salgundi, Igor Andreoni (UNC), Thomas Culino (Caltech), Sushant Sharma Chaudhary, Michael W. Coughlin, Tyler Barna (UMN), K-Ryan Hinds (Caltech), Marion Pillas, Sarah Antier (IJCLAB)
Source Group: ZTF
Keywords: Transient
Abstract:
We report observations of the red and fast fading transient AT2026wki/ZTF26abkoycd, identified in the ZTF alert stream. The transient faded by ~1.1 mag/day in g-band and its color is red (g-r~0.2 mag after correcting for Galactic extinction). The nature of AT2026wki/ZTF26abkoycd is uncertain: its light curve properties are consistent with an extragalactic afterglow, although the transient has been found at an intermediate Galactic latitude of b=17.7 deg, thus we cannot exclude that it is a Cataclysmic Variable. There is no credible high energy crossmatch reported on the General Coordinates Network between the last upper limit and the first detection.

AT2026wki/ZTF26abkoycd was detected by the Zwicky Transient Facility, identified with two fast transient filters independently via SkyPortal (Coughlin et al., 2023) running with the BOOM broker (du Laz et al., 2025) at RA = 19:41:08.17, Dec = +60:49:17.80 (J2000). The source was first detected at 2026-07-29 05:48:58 UT (MJD 61250.242).

Available detections and the last non-detection, which are corrected for Galactic extinction (E(B-V) = 0.0585) using the Gordon et al. (2023) extinction law with R_v = 3.1), are summarized below:

Epoch (MJD)FilterAB MagnitudeAB Magnitude (corrected)
61249.333ZTF-r>19.2>19.1
61250.242ZTF-r18.40 ± 0.0918.25 ± 0.09
61250.448ZTF-g18.68 ± 0.1118.46 ± 0.11
61251.241ZTF-r18.90 ± 0.1018.75 ± 0.10
61251.312ZTF-g19.62 ± 0.1819.40 ± 0.18

The source has a fade rate of 1.1 ± 0.2 magnitudes per day in g-band and a red color of (g−r) = 0.21 ± 0.14 mag (corrected for Galactic extinction) at the first epoch.  While there is no catalogued source coincident with AT2026wki, we note the presence of a faint, sub-threshold source coincident with the transient in archival imaging from the DESI Legacy Imaging Surveys (DR11) (Dey et al., 2019).  Compared to field sources, the LS object is blue in colour, which may indicate star formation.

Given the rapid fading and red color, we consider AT2026wki a strong afterglow candidate. There is no credible high energy crossmatch reported on the General Coordinates Network  between the last upper limit and the first detection.  It is at an intermediate Galactic latitude of b=17.7 degrees and therefore cannot rule out that this transient is a Cataclysmic variable. We encourage photometric and spectroscopic follow-up.  

Show current TNS values
Catalog Name Reported RA Reported DEC Reported Obj-Type Reported Redshift Host Name Host Redshift Remarks TNS RA TNS DEC TNS Obj-Type TNS Redshift
TNS 2026wki [ZTF26abkoycd] 19:41:08.176 +60:49:17.78 19:41:08.176 +60:49:17.78

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