From: LARRY KLAES (ljk4_at_msn.com)
Date: Wed Oct 10 2007 - 11:15:34 PDT
>From: "AAS Press Officer Dr. Steve Maran" <Steve.Maran_at_aas.org>
>To: "AAS Press Officer Dr. Steve Maran" <steve.maran_at_aas.org>
>Subject: McD Obs: MOST POWERFUL SUPERNOVA EVER
>Date: Wed, 10 Oct 2007 11:30:03 -0400
>
THE FOLLOWING RELEASE WAS RECEIVED FROM THE McDONALD OBSERVATORY AT THE
UNIVERSITY OF TEXAS, IN AUSTIN, AND IS FORWARDED FOR YOUR INFORMATION.
(FORWARDING DOES NOT IMPLY ENDORSEMENT BY THE AMERICAN ASTRONOMICAL
SOCIETY.) Steve Maran, American Astronomical Society steve.maran_at_aas.org
1-202-328-2010 x116
Contact:
Rebecca Johnson, McDonald Observatory
The University of Texas at Austin
1-512-475-6763; rjohnson_at_astro.as.utexas.edu
Dr. Robert Quimby
California Institute of Technology
1-626-395-5927; quimby_at_astro.caltech.edu
Dr. J. Craig Wheeler
The University of Texas at Austin
1-512-471-6407; wheel_at_astro.as.utexas.edu
FOR IMMEDIATE RELEASE October 10, 2007
MOST POWERFUL SUPERNOVA EVER:
FOUND WITH MINI, MONUMENTAL McDONALD OBSERVATORY TELESCOPES
FORT DAVIS, Texas - Astronomer Robert Quimby has done it
again. Found the most luminous supernova ever, that is.
Quimby discovered the current record holder, supernova
2006gy, last year as part of his Texas Supernova Search
project. Now he announces that a supernova he discovered
earlier in the project is actually twice as luminous. Using
follow-up studies to pinpoint its distance, supernova 2005ap
peaked at more than 100 billion times the brightness of the
Sun. The result has been accepted for publication in the
October 20 edition of The Astrophysical Journal Letters.
This supernova is a Type II, Quimby said, because it
contains hydrogen. Most Type II supernovae are thought to
result when the cores of massive stars, those seven to eight
times or more heavy than the Sun, collapse under their own
weight and trigger an explosion. This particular Type II is
300 times brighter than average, Quimby said, and lies in a
dwarf galaxy in the constellation Coma Berenices, well
behind the famous Coma cluster of galaxies.
"It's clearly not the same as 2006gy," Quimby's colleague
and supernova expert J. Craig Wheeler of The University of
Texas at Austin said. "It's a puzzle."
Quimby completed his Ph.D. under Wheeler's supervision at
Texas in May, and has just begun a post-doctoral appointment
at Caltech. His Texas Supernova Search uses the 18-inch
ROTSE-IIIb robotic telescope on McDonald Observatory's Mount
Fowlkes, a tiny neighbor to the giant 10-meter-class
Hobby-Eberly Telescope (HET).
Quimby studied 2005ap with HET just a few days after its
discovery. The results were intriguing, Quimby said. The
supernova's spectrum hinted at the presence of a highly
shifted absorption line of oxygen III (an oxygen atom that
has lost two of its electrons). Quimby knew that if the
feature was oxygen III, then 2005ap was "possibly very far
away and thus very luminous."
Follow-up observations with the Keck Telescope in Hawaii by
Quimby's colleague Greg Aldering of Lawrence Berkeley
National Lab not only confirmed Quimby's HET detection of
oxygen III, but added another, equally shifted element to
the spectrum: magnesium.
Together, the studies confirmed 2005ap's distance of 4.7
billion light-years. (In astronomical terms, this equates to
a redshift of z = 0.2832.)
It was this distance measurement, combined with measurements
of the supernova's apparent brightness that allowed the
calculation of its intrinsic brightness, or "luminosity,"
and uncovered 2005ap as the most powerful supernova yet.
"Before 2006gy, I thought this should not be plausible,"
Quimby said. "There I was finding my first supernovae ‹ I
was just happy to get anything. It turned out to be the most
luminous supernova ever found."
How is that Quimby has found the brightest supernova yet,
twice in a row? "I've worked too damn hard for this to be
luck," he said.
Quimby explained, "I'm searching a huge volume of space,
comparable to all previous nearby supernova surveys
combined." Also, Quimby will find supernovae that other
studies ignore: he doesn't filter out non-Type Ia
supernovae, which is what many studies do that are searching
for supernovae for cosmology studies, and he does search
dwarf galaxies as well as galaxies with active black holes
at their centers, which other studies avoid. Others also
avoid supernovae near the cores of galaxies.
In fact, 2006gy was found in the core of a galaxy, and that
galaxy has a weakly active central black hole, Wheeler said.
"There's no question that [his results] have gotten
everybody's attention," Wheeler said. The University of
Michigan-run ROTSE collaboration, whose main mission is the
search for gamma-ray bursts, has decided to expand the
supernova search to its entire network. Its robotic
telescopes in Australia, Turkey, and Namibia will soon join
the unit at McDonald Observatory in this search. The Sloan
Digital Sky Survey Supernova Search, for which HET
provides confirming spectra, is also reconsidering its
search filters in response to these discoveries, Wheeler
said.
The Hobby-Eberly Telescope is a joint project of The
University of Texas at Austin, The Pennsylvania State
University, Stanford University,
Ludwig-Maximilians-Universität München, and
Georg-August-Universität Göttingen.
END
Notes: Images to accompany this release are available online:
http://mcdonaldobservatory.org/news/releases/2007/1010.html
Caption:
Left: Sloan Digital Sky Survey (SDSS) image of the field
where supernova 2005ap was found, showing four nearby
galaxies (A, B, C, and D) in December 2004. Right:
Hobby-Eberly Telescope (HET) image of the same field about
2.5 months later, showing supernova 2005ap. The supernova's
host galaxy is too distant to appear in either image.
Credit: SDSS, R. Quimby/McDonald Obs./UT-Austin
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