SN 2016gkg - Unusual Type-II Supernova in NGC 613 (Scl)

PTS

AAVSO Special Notice #421

September 22, 2016
SN 2016gkg - Unusual Type-II Supernova in NGC 613 (Scl)


SN 2016gkg (announced as AT2016gkg) was discovered by Victor Buso
(Rosario, Argentina) on 2016 September 20.2484 UT at CCD magnitude
(clear filter) 17.6 +/-0.5, rising to 14.5 +/-0.02 on Sep. 21.1398.
His discovery was reported to the Transient Name Server by
Sebastian Otero (Buenos Aires, Argentina). It was confirmed by
ASAS-SN on Sep. 21.29 UT (B. Nicholls (Mt. Vernon Obs., New
Zealand) et al., ATel #9521) and by ATLAS on Sep. 20.54 UT (J.
Tonry (IfA, University of Hawaii) et al., ATel #9526).

SN 2016gkg was spectroscopically confirmed as a Type-II supernova
by S. W. Jha (Rutgers), V. van Wyk, and P. Vaisanen (SALT/SAAO)
from observations made on 2016 September 21.9 UT (ATel #9528).

Its optical behavior has been very unusual, with more than a
magnitude decline in 24-48 hours, which is highly atypical for
a Type-II supernova. It is for this reason that observations are
requested as the supernova evolves. The most recent magnitude
available is 15.73 V +/- 0.05 on 2016 Sep. 22.3 UT, using ASAS-SN
data (Ping Che (KIAA-PKU) et al., ATel #9529).

V observations are requested; other bands may be added as time and
inclination permit. As this supernova appears to be changing so
quickly, multiple observations per night would be valuable.

Coordinates for SN 2016gkg: R.A. 01 34 14.40  Dec. -29 26 24.2 (2000.0)
This position is 78.4" South and 49.1" West of the center of NGC
613 (ATel #9521).

Charts with comparison stars for SN 2016gkg may be created using
the AAVSO Variable Star Plotter (VSP,http://www.aavso.org/vsp).
Observers may find choosing the 'display DSS chart' when creating
their charts very helpful, as the DSS image of the galaxy will be
supraimposed on the star positions and magnitude labels. Also, be
sure to tick the boxes requesting Rc and Ic comparison stars in
addition to the V and B-V which are supplied by default.

Please report observations to the AAVSO International Database
using the name SN 2016gkg.

ATel links:
ATel #9521 - http://www.astronomerstelegram.org/?read=9521
ATel #9526 - http://www.astronomerstelegram.org/?read=9526
ATel #9528 - http://www.astronomerstelegram.org/?read=9528
ATel #9529 - http://www.astronomerstelegram.org/?read=9529

Congratulations to Victor on his discovery!


This AAVSO Special Notice was compiled by Elizabeth O. Waagen.

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