Electronic Telegram No. 4120
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  Daniel W. E. Green; Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


SUPERNOVA 2015L
     Subo Dong, Kavli Institute for Astronomy and Astrophysics, Peking
University; B. J. Shappee, Carnegie Observatories; J. L. Prieto, Universidad
Diego Portales; S. W. Jha, Rutgers University; K. Z. Stanek, T. W.-S. Holoien,
C. S. Kochanek, and T. A. Thompson, Ohio State University (OSU); N. Morrell
and I. B. Thompson, Carnegie Observatories; U. Basu and J. F. Beacom, OSU;
D. Bersier, Liverpool John Moores University; J. Brimacombe, Cairns,
Australia; J. S. Brown, OSU; P. Chen, Peking University; E. Conseil,
Association Francaise des Observateurs d'Etoiles Variables; A. B. Danilet,
OSU; E. Falco, Harvard-Smithsonian Center for Astrophysics; D. Grupe,
Morehead Sate University; S. Kiyota, Kamagaya, Japan; G. Masi, Ceccano,
Italy; B. Nicholls, Mt. Vernon Observatory; F. Olivares and G. Pignata,
Universidad Andres Bello; G. Pojmanski, Warsaw University Astronomical
Observatory; G. V. Simonian, OSU; D. M. Szczygiel, Warsaw University
Astronomical Observatory; and P. R. Wozniak, Los Alamos National Laboratory,
report the discovery of an apparent supernova (V magnitude about 17.0) on
images obtained in the course of the "All Sky Automated Survey for SuperNovae
(ASAS-SN)" with the double 14-cm "Cassius" telescope at Cerro Tololo on June
14.25 UT.  The new object is located at R.A. = 22h02m15s.45, Decl. =
-61d39'34".6 (equinox 2000.0), which is approximately 0".41 ast and 0".04
south of the center of the galaxy APMUKS(BJ) B215839.70-615403.9.  Additional
magnitudes for the variable:  May 15.33, [17.3; 18.32, 17.3 (marginal
detection); 22.32, 17.2; 26.31, 17.0; 27.34, 16.9; June 8.36, 16.9; 9.25,
16.8; 11.40, 17.1; 12.22, 17.1; 13.23, 16.9.
     Spectroscopic follow-up was obtained on June 21 UT with the du Pont 2.5-m
telescope (+ WFCCD) at Las Campanas Observatory, on June 30 and July 7 with
the SALT 10-m telescope (+ RSS), on June 24 with the SOAR 4-m telescope (+
Goodman instrument) at Cerro Pachon, and on July 6 with the Clay 6.5-m
telescope (+ MagE) at Las Campanas Observatory.  All of the spectra reveal
a very blue, mostly featureless continuum, except for broad (O II) absorption
features characteristic of hydrogen-poor super-luminous supernovae -- SLSN-I
(prototype supernova 2005ap; see the review by Gal-Yam 2012, Science 337, 927
for the classification).  They also detect narrow Mg II (rest wavelengths
279.5 and 280.2 nm) absorption in the June 30 SALT spectrum with spectral
resolution R = 800, subsequently confirmed by higher-spectral-resolution Clay
telescope spectroscopy on July 6 and SALT spectroscopy (R = 2500) on July 7.0.
They all yield a consistent redshift for the supernova host galaxy of z =
0.2326.  Presence of a very blue, slowly evolving transient is also confirmed
by the ongoing photometric follow-up observations in B, V, R, and I bands
from the LCOGT 1-m robotic telescopes and in optical/ultraviolet with the
SWIFT UVOT/XRT satellite instruments.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2015 CBAT
2015 July 24                     (CBET 4120)              Daniel W. E. Green