Supernova SN 2013bl Discovered April 7, 2013

Above: A positive (left) and negative (right) image of supernova SN2013bl in Galaxy UGC 4578. Image courtesy of Doug Rich.

Above: A positive (left) and negative (right) image of supernova SN2013bl in Galaxy UGC 4578. Image courtesy of Doug Rich.

Discovery overview

Discovering party: Eagle Hill Supernova Search Project: Doug Rich, Joseph Rosebush, and Charles Sawyer
Official CBAT name: SN 2013bl
Category: Supernova
Subcategory: Type llb
Location: Galaxy UGC 4578 in the Constellation Lynx
Distance: Approximately 400 million light-years from Earth

Coordinates and location in the sky

RA 8h 46m 14s
Dec.+41o 34’ 47”

Discovery credit

Supernova SN 2013bl was discovered by the Eagle Hill Supernova Search Project led by Doug Rich. Team members Charlie Sawyer and Joe Rosebush conducted the blink comparison that resulted in the discovery.

The reference image of galaxy UGC 4578 was taken by Doug Rich from his home observatory in Hampden, Maine on January 30, 2012. The image indicating the existence of an emergent supernova was taken by Rich on April 7, 2013 UT with a confirmation image taken on April 8, 2013 UT by Paul Burke from his observatory in Pittsfield, Maine.


Spectroscopic analysis of the supernova was conducted by astronomer Andrea Pastorello and his team with the Italian National Institute for Astrophysics in Asiago, Italy. The supernova was then designated SN 2013bl by the Central Bureau for Astronomical Telegrams in Cambridge, Massachusetts.

Discovery Notes

  • Initial spectroscopic analysis of the supernova indicated that it might be a a type lbc supernova. However, additional analysis led to the confirmation of the supernova as a type llb, which is one of the rarer types of supernovae.
  • SN2013bl was the 64th Supernova discovered in 2013.

Official CBAT Report

SUPERNOVA 2013bl IN UGC 4578 = PSN J08461506+4134400
    D. Rich, J. Rosebush, and C. Sawyer report their discovery of an apparent
supernova (mag about 18.0) on unfiltered CCD frames (limiting mag 19.2) taken
with a 0.41-m reflector on Apr. 7.077 UT in Hampden, ME, U.S.A., in the course
of the Eagle Hill Supernova Search Project.  The new object is located at R.A.
= 8h46m15s.06, Decl. = +41o34’40″.0 (equinox 2000.0), which is about 10″.8
east and 7″.2 south of the center of UGC 4578.  Nothing is visible at this
location on Palomar Digital Sky Survey images from 1989 Mar. 9 (limiting red
mag about 20.3) and 1994 Jan. 11 (limiting blue mag about 21.0).  The variable
was designated PSN J08461506+4134400 when it was posted at the Central
Bureau’s TOCP webpage and is here designated SN 2013bl based on the
spectroscopic confirmation reported below.  Additional CCD magnitudes for
2013bl:  2013 Mar. 25.130, [19.0 (Rich); Apr. 8.043, 17.8 (P. Burke,
Pittsfield, ME, U.S.A.; 0.35-m reflector; limiting mag 18.6; via Rich); 8.318,
19.4 (Joseph Brimacombe, Cairns, Australia; remotely using a 51-cm RCOS
telescope + STL11K camera + luminance filter at the New Mexico Skies
observatory near Mayhill, NM, U.S.A.; position end figures 15s.02, 41″.1;
image posted at URL;
14.009, 18.4 (Federica Luppi and Luca Buzzi, Varese, Italy; 0.38-m f/6.8
reflector; position end figures 14s.99, 40″.7; reference stars from CMC-14
catalogue; image posted at

    L. Tomasella, S. Benetti, A. Pastorello, E. Cappellaro, M. Turatto, and
P. Ochner, Osservatorio Astronomico di Padova, Istituto Nazionale di
Astrofisica, report that optical spectroscopy (range 340-820 nm; resolution
1.3 nm), obtained on Apr. 17.82 UT with the Asiago 1.82-m Copernico Telescope
(+ AFOSC), shows that PSN J08461506+4134400 = SN 2013bl is a stipped-envelope
supernova, in agreement with Pecontal et al. 2013 (as posted at website URL  However, adopting a redshift
of z about 0.030 for the host galaxy, UGC 4578 (Sloan Digital Sky Survey Data
Release 2, 2004), the best match has been found with several type-IIb
supernovae a few weeks after maximum light.  Together with He I and Fe II
lines, H_alpha is clearly detected.  The expansion velocity of the ejected
material, as deduced from the position of the strong He-I 587.6-nm absorption,
is about 8000 km/s.  The Asiago classification spectra are posted at website
URL; classification was made via GELATO
(Harutyunyan et al. 2008, A.Ap. 488, 383) and SNID (Blondin and Tonry 2007,
Ap.J. 666, 1024).

Spectral Graph

Above: A graph comparing the spectral report of SN2013bl (black) with the spectral report of of SN200H (blue) which is also a type llb supernova.

Above: A graph comparing the spectral report of SN2013bl (black) with the spectral report of of SN200H (blue) which is also a type llb supernova.

Locating the Constellation Lynx in the Night Sky

Image courtesy of Sky & Telescope Media.

© Sky Publishing Corporation. Used with Permission. All rights reserved.


Location of UGC 4578 Within the Constellation Lynx

Image Courtesy of Sky & Telescope Media.

© Sky Publishing Company. Used with Permission. All rights reserved.


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