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GCN Circular 22270

GRB 171205A: SMARTS optical/IR supernova monitoring
2017-12-23T04:25:55Z (6 years ago)
Bethany Cobb at GWU <>
B. E. Cobb (GWU), reports:

Using the ANDICAM instrument on the 1.3m telescope at CTIO, we
obtained additional optical/IR imaging of the error region of
GRB 171205A (GCN 22177, D'Elia et al.). At each epoch,
total summed exposure times amounted to 15 min in V and I
and 12 min in J and K.

Between approximately 1 and 2 days post-burst, the optical/IR
afterglow of GRB 171205A (GCN 22180, Izzo et al.;
GCN 22181, Emery et al.; GCN 22182, Butler et al.;
GCN 22186, Mao et al.; GCN 22188, Choi et al.;
GCN 22189, Melandri et al.; GCN 22190, Steeghs et al.;
GCN 22192, Cobb; GCN 22193, Volnova et al.;
GCN 22195, Mao et al.; GCN 22197, Guidorzi et al.;
GCN 22198, Schmidl & Schady; GCN 22199, Lipunov et al.;
GCN 22202, Siegel et al.; GCN 22205, Volnova et al.;
GCN 22215, Laskar et al.; GCN 22223, Volnova et al.;
GCN 22224, Volnova et al.; GCN 22225, Hentunen & Nissinen;
GCN 22226, Lipunov et al.) is clearly seen to dim. After about 6 days
post-burst, however, a brightening is detected. This brightening is
due to the emergence of the underlying supernova associated with
GRB 171205A, and is consistent with the spectroscopic
detection of this supernova by de Ugarte Postigo et al. (GCN 22204).

Approximate I-band and J-band magnitudes are given below.

post-burst      I mag   J mag
1.02056         17.7    17.6
2.03260         18.1    17.9
4.03747         18.2    18.0
6.01435         18.1    17.6
10.98015        17.7    17.5
17.01212        17.6    17.0

(Optical photometry is calibrated against Landolt standard stars;
and IR photometry is calibrated against 2MASS stars in the
field. The magnitudes include afterglow and host galaxy contributions
and should be considered only highly preliminary values.)
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