AT2023avj
GCN Circular 33238
Subject
AT2023avj: X-ray Detection with Swift/XRT
Date
2023-01-30T22:36:51Z (3 years ago)
Edited On
2025-09-09T18:37:58Z (a month ago)
From
Anna Ho at UC Berkeley <annayqho@berkeley.edu>
Edited By
courey.elliott@gmail.com
Anna Y. Q. Ho (Cornell) reports on behalf of a larger collaboration:
We observed the fast optical transient AT2023avj (Wang et al., GCN Circ.
33226 and AstroNote 2023-17) with Swift/XRT beginning at 2023-01-27 14:46
UT, or 5.3d after the first ZTF detection. In a 4.6ks exposure, we detect
X-ray emission with a count rate of 0.003 +/- 0.001 ct/s. Using WebPIMMS
[1] we estimate [2] that this corresponds to an unabsorbed 0.3-10 keV flux
density of 1.1E-13 ergs/cm2/s, similar to the flux density of GRB
afterglows at this phase.
No GRB counterpart has been reported.
We thank the Swift staff for rapidly approving and scheduling our
observations.
[1] https://heasarc.gsfc.nasa.gov/cgi-bin/Tools/w3pimms/w3pimms.pl [2]
Using a hydrogen column density of 1.6E20/cm2 (Willingale, R., et al. 2013,
MNRAS, 431, 394) and a power-law index of 2
GCN Circular 33227
Subject
AT2023avj ZTF Candidate: Assy optical observations
Date
2023-01-28T14:06:56Z (3 years ago)
Edited On
2025-09-09T18:37:56Z (a month ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
Edited By
courey.elliott@gmail.com
N. Pankov (HSE, IKI), V. Kim (FAI, Pulkovo Observatory), A. Pozanenko
(IKI), M. Krugov (FAI), S. Belkin (IKI) report on behalf of GRB IKI FuN:
We observed the Candidate Optical Afterglow ZTF23aaarlti (AT2023avj)
(Wang et al., GCN 33226) with AZT-20 telescope of Assy-Turgen
observatory starting on 2023-01-277 (UT) 19:03:41.
We clearly detect the optical source (Wang et al., GCN 33226).
Preliminary photometry of the optical afterglow in a stacked image is
following
Date UT start MJD Exp. Filter OT Err. UL(3sigma)
(mid, days) (s)
2023-01-27 19:03:41 59971.80069 75*60 r'(AB) 22.67 0.12 23.9
The photometry is based on nearby PS1 stars.
GCN Circular 33226
Subject
ZTF and LT Observations of AT2023avj, a Candidate Optical Afterglow
Date
2023-01-27T02:10:08Z (3 years ago)
Edited On
2025-09-09T18:37:55Z (a month ago)
From
Anna Ho at UC Berkeley <annayqho@berkeley.edu>
Edited By
courey.elliott@gmail.com
Kailai Wang (Cornell), Anna Y. Q. Ho (Cornell), Daniel Perley (LJMU) on
behalf of the Zwicky Transient Facility (ZTF) collaboration:
We report the discovery of a fast-evolving red transient in Zwicky
Transient Facility (ZTF) partnership data and Liverpool Telescope (LT) data.
ZTF23aaarlti (AT2023avj) was discovered at the position (J2000) of:
RA = 09:39:20.82 (144.83673 deg)
Dec = +58:08:12.52 (58.13681 deg)
on 2023 January 22 by ZTF at i = 19.27 +/- 0.27 (MJD=59966.29) and g =
20.02 +/- 0.20 (MJD=59966.32). Forced photometry on P48 images revealed
an additional r-band detection (r=20.14+/-0.19; MJD 59966.39) as well as
limits the previous night of g > 20.18 mag (MJD 59965.37) and r > 21.14 mag
(MJD 59965.35). The rise rate (>1 mag/day in r-band) of AT2023avj was
therefore very fast.
The Galactic latitude of AT2023avj is 45 degrees, and the Galactic
extinction towards the direction of AT2023avj is low: E(B-V)=0.01 from
Schlafly & Finkbeiner (2011). There is no counterpart within several
arcseconds in Legacy Survey DR9 imaging.
The red color, fast rise rate, and lack of a stellar counterpart or bright
host galaxy motivated us to trigger follow-up observations.
LT griz imaging at 4.7 days after the first ZTF detection confirmed the red
colors. With a detection at r=23.08 +/- 0.25 (MJD=59971.05), the implied
average fading rate is 0.46 mag/day in r-band.
The fast rise, fast decay, red color, and lack of archival optical
counterpart of AT2023avj make it a strong candidate afterglow. However, we
did not identify any GRBs coincident with this position during the time
window between the last non-detection and the first detection.
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.