GCN Circular 29321
Subject
ZTF21aaeyldq CAHA 2.2m detection and power-law decay
Event
Date
2021-01-18T18:06:36Z (5 years ago)
From
Alexander Kann at IAA-CSIC <kann@iaa.es>
D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC,
DARK/NBI), C. C. Thoene (HETH), M. Blazek, J. F. Agui Fernandez (both
HETH/IAA-CSIC), and J. I. Vico Linares (CAHA) report:
We observed the position of the GRB-less afterglow ZTF21aaeyldq (Ho et
al., GCN #29305; de Ugarte Postigo et al., GCN #29307) with CAFOS at the
2.2m telescope at Calar Alto, Almeria, Spain, in the Rc band. We
obtained 10 x 360 s exposures, centered at 1.74430 days after the
transient discovery, under fair conditions but mediocre seeing.
The afterglow (Kumar et al., GCNs #29308; Ahumada et al., GCN #29309;
Zhu et al., GCN #29310; Hu et al., GCN #29312) is clearly detected. We
measure Rc = 22.89 +/- 0.12 mag. (AB mag, vs. the same SDSS star as in
our GTC observation, GCN #29307 converted to Rc following the Lupton
transformations, then transformed back to AB mag).
We take data from Ho et al., GCN #29305; de Ugarte Postigo et al., GCN
#29307; and Zhu et al., GCN #29310 (all in r'), and here assume a
trigger time 22 minutes before the discovery (at the last
non-detection). We find this data is fit well with a single power-law, a
straight decay slope alpha ~ 0.91 +/- 0.02. The magnitude we report now
lies slightly (0.3 mag) below the extrapolation of the afterglow decay.
Further observations are needed to determine whether this represents a
jet break.