Electronic Telegram No. 3506
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 2013by IN ESO 138-G10 = PSN J16590243-6011418
     Stuart Parker, Canterbury, New Zealand, reports the discovery of an
apparent supernova (red mag 13.5) on a unfiltered CCD images (limiting mag
19) taken by himself on Apr. 23.542 and 24.320 UT with a 30-cm Astro-Tech
AT12RC Ritchey-Chretien astrograph (+ ST10 camera) at the Parkdale Observatory
in the course of the Backyard Observatory Supernova Search (BOSS).  The new
object is located at R.A. = 16h59m02s.43, Decl. -60d11'41".8 (equinox 2000.0;
reference stars from USNO-B and UCAC3 catalogues), which is 3" west and 76"
north of the nucleus of the galaxy ESO 138-G10.  Nothing is visible at this
position on Digitized Sky Survey red and infrared images (limiting red mag >
19).  Parker has posted an image at website URL http://tinyurl.com/acvf9dl.
The variable was designated PSN J16590243-6011418 when it was posted at the
Central Bureau's TOCP webpage and is here designated SN 2013by based on the
spectroscopic confirmation reported below.  Additional CCD magnitudes for
2013by:  Apr. 1.554 UT, [18.5 (Parker); 24.568, 14.0 (Joseph Brimacombe,
Cairns, Australia; 41-cm RCOS telescope + STL6K camera + infrared filter;
bandpass > 700 nm; position end figures 02s.55, 40".7; image posted at URL
http://www.flickr.com/photos/43846774@N02/8682304315/); 24.600, V = 13.69
and I_c = 13.67 (S. Kiyota, Tsukuba, Japan; remotely with an iTelescope.net
0.50-m astrograph + FLI-PL6303E camera at Siding Spring, NSW; image posted
at URL http://meineko.sakura.ne.jp/ccd/PSN_J16590243-6011418-130424.jpg).

     N. Morrell, E. Hsiao, C. Contreras, C. Gonzalez, and A. Campillay, on
behalf of the Carnegie Supernova Project, report on spectroscopic and
photometric observations of PSN J16590243-6011418 = 2013by obtained at Las
Campanas Observatory.  A near-infrared spectrum (range 800-2400 nm) of 2013by
was obtained by M. Gromadzki (University of Valparaiso) and M. T. Ruiz
(University of Chile) on Apr. 24.4 UT with the Magellan I Baade 6.5-m
telescope (+ FIRE).  Inspection of the data reveals a blue featureless
continuum, compatible with a type-II supernova shortly after explosion.
Optical photometry obtained with the 1-m Swope telescope shows that 2013by
has brightened since discovery, reaching V magnitude 13.26 on Apr. 29.42
and probably still rising in the V band.

     D. Milisavljevic, Harvard-Smithsonian Center for Astrophysics (CfA); R.
Fesen, Dartmouth College; T. Pickering and P. Vaisanen, South African
Astronomical Observatory; G. H. Marion, CfA; J. Parrent, Dartmouth College
and Las Cumbres Observatory; and R. Margutti and A. Soderberg, CfA, report
that low-dispersion spectra (range 320-900 nm) obtained on Apr. 25.0, 25.9,
27.9, and 30.0 UT with the 10-m SALT telescope (+ RSS) of PSN
J16590243-6011418 = 2013by show it to be a young and luminous type-II
supernova.  All spectra are dominated by a strong blue continuum and weak,
yet broad, P-Cyg absorptions associated with H Balmer, Na I, Fe II, and
potentially Si II lines that have been slowly increasing in strength between
epochs.  After correcting for a redshift of z = 0.0035, measured from narrow
H_alpha and H_beta lines and consistent with the redshift of the host galaxy,
ESO 138-G10 (Koribalski et al. 2004), the velocities of these P-Cyg
absorptions are on the order of 6000-8000 km/s.  They note that the narrow
(FWHM < 250 km/s) H_alpha profile exhibits a blue-to-red asymmetry that
suggests association with the supernova.  These data currently indicate 2013by
to possibly be a type-IIL/IIn intermediate object, although further
observations are encouraged to verify this classification.


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

                         (C) Copyright 2013 CBAT
2013 May 6                       (CBET 3506)              Daniel W. E. Green