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GCN Circular 33229

ZTF23aabmzlp/AT2023azs: Zwicky Transient Facility discovery of a fast optical transient
2023-01-28T18:10:55Z (a year ago)
Igor Andreoni at JSI <>
Igor Andreoni (JSI), Harsh Kumar (IITB), Michael Coughlin (UMN), Gaurav
Waratkar (IITB), Eric Burns (LSU), Daniel Perley (LJMU)

We report the discovery of the very fast optical transient
ZTF23aabmzlp/AT2023azs with the Zwicky Transient Facility (ZTF, Bellm et
al. 2019, Graham et al. 2019) at coordinates:

RA = 11:30:16.49 (172.5687149d)
Dec = +65:51:10.01 (65.8527808d)

ZTF23aabmzlp was first detected on 2023-01-28 06:14 UT at r = 17.42 �� 0.04
mag. ZTF23aabmzlp faded by 2.3 magnitudes in 6.2 hours in the r-band. The
last ZTF upper limit before the first detection was measured on 2023-01-28
05:55 UT in g-band, which is about 19 minutes before the first detection.
There is no pre-detection at the transient location in 1,736 images of the
field previously acquired by the ZTF survey. ZTF photometry is reported in
the following table:

     MJD       |     mag AB
59972.24688660 | g > 19.7
59972.25979170 | r = 17.42 +- 0.04
59972.36381940 | g = 19.20 +- 0.11
59972.43465280 | g = 19.60 +- 0.15
59972.51854170 | r = 19.72 +- 0.20

Extinction on the line of sight is negligible, with E(B-V)=0.01 mag. The
transient is located at high Galactic latitude b=49.2 deg. There is no
cataloged source at the transient location in deep Legacy Survey DR9 and
Pan-STARRS (Chambers et al., 2016) archival images.

No gamma-ray triggers have been reported so far in the time window between
the last ZTF upper limit and the first detection. However, it is possible
that ZTF23aabmzlp/AT2023azs is a relativistic afterglow.

Follow-up observations are strongly encouraged.

ZTF23aabmzlp was discovered by the ������ZTF Realtime Search and Triggering������
project (ZTFReST; Andreoni & Coughlin et al., 2021) within the ZTF

Based on observations obtained with the Samuel Oschin Telescope 48-inch and
the 60-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.
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