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cycloadditions can be achieved with one aryl enone
that can easily be reduced to the corresponding radical
anion and a second b-unsubstituted alkyl enone that
possesses a more negative redox potential but is a less
sterically encumbered Michael acceptor.
28. The absolute configuration of 2c was determined by
x-ray crystallographic analysis of the corresponding
2,4-dinitrophenylhydrazone (S3) using anomalous
dispersion. See supplementary materials for details. The
configurations of other 1,2-trans cycloadducts were
assigned by analogy.
29. A. E. Allen, D. W. MacMillan, Chem. Sci. 2012, 633–658
30. Reactions conducted with ligand 9 at –20 °C proceeded
at prohibitively slow rates and offered little improvement
31. The absolute configuration of 3c was determined by
x-ray crystallographic analysis using anomalous
dispersion. See supplementary materials for details.
The configurations of other 1,2-cis cycloadducts were
assigned by analogy.
32. H. Yamamoto, Lewis Acids in Organic Synthesis (Wiley-VCH,
Weinheim, New York, 2000).
Acknowledgments: We thank B. S. Dolinar and I. A. Guzei for
determining absolute stereochemistry by x-ray crystallography.
Metrical parameters for the structures of 3c and S3 are
available free of charge from the Cambridge Crystallographic
Data Centre under reference numbers CCDC-988977 and
988978, respectively. Funding for this work was provided by
an NIH research grant (GM095666) and a postdoctoral
fellowship to D.M.S. (GM105149).
Materials and Methods
Figs. S1 to S3
Tables S1 to S16
29 January 2014; accepted 10 March 2014
Detection of the Gravitational Lens
Magnifying a Type Ia Supernova
Robert M. Quimby,1 Masamune Oguri,1,2 Anupreeta More,1 Surhud More,1 Takashi J. Moriya,3,4
Marcus C. Werner,1,5 Masayuki Tanaka,6 Gaston Folatelli,1 Melina C. Bersten,1
Keiichi Maeda,7 Ken’ichi Nomoto1
Objects of known brightness, like type Ia supernovae (SNIa), can be used to measure distances.
If a massive object warps spacetime to form multiple images of a background SNIa, a direct
test of cosmic expansion is also possible. However, these lensing events must first be distinguished
from other rare phenomena. Recently, a supernova was found to shine much brighter than
normal for its distance, which resulted in a debate: Was it a new type of superluminous supernova
or a normal SNIa magnified by a hidden gravitational lens? Here, we report that a spectrum
obtained after the supernova faded away shows the presence of a foreground galaxy—the
first found to strongly magnify a SNIa. We discuss how more lensed SNIa can be found than
Apeculiar supernova, PS1-10afx, was discovered by the Panoramic Survey Telescope & Rapid Response System
1 (Pan-STARRS1) on 31 August 2010 (universal
time) (1). The unusually red color of the object
spurred the Pan-STARRS1 team to conduct an
array of follow-up observations, including optical
and near-infrared spectroscopy, which yielded a
redshift of z = 1.39. Combined with relatively
bright photometric detections, this redshift would
imply a peak luminosity of 4 × 1044 erg s−1,
which is 400 times brighter than the typical core-
collapse supernova. A rare class of superluminous
supernovae (SLSN) (2) have shown similarly high
bolometric outputs, but PS1-10afx distinguishes
itself from all other SLSN on two important
counts: PS1-10afx is much redder (cooler) and
evolved much faster than any SLSN. A generic
feature of SLSN models (3–9) is that they em-
ploy high temperatures (T) and/or large photo-
spheric radii (R) to generate high luminosities
(L) (recalling that L º T 4R2). The observations
of PS1-10afx do not fit with these models,
suggesting that if it is a SLSN, it is in a class of
An alternate hypothesis (10) is that PS1-10afx
is actually a regular type Ia supernova (SNIa)
with a normal luminosity, but its apparent brightness has been magnified by a gravitational lens.
Spectra of PS1-10afx are well fit by normal SNIa
templates, as are the colors and light curve shapes.
However, normal SNIa exhibit a tight relation
between the widths of their light curves and their
peak luminosities (11–14), and PS1-10afx appears
30 times brighter than expected, according to this
relation. Such a large magnification of brightness
can only occur naturally from strong gravitational
lensing, whereby the light emanating from the
supernova is bent to form an Einstein-Chwolson
ring, or several discrete magnified images (typically
two or four) if the alignment is not axisymmetric.
Pan-STARRS1 has surveyed sufficient volume
to expect such a chance alignment (15, 16), and
it is possible that the angular extent of the lensed
images was simply too small to be resolved by
the observations available. However, for this hy-
pothesis to be confirmed, we must explain why
the existing observations give such conclusive
photometric and spectroscopic evidence for the
presence of the supernova’s host galaxy, but the
same observations fail to obviously indicate
the presence of a foreground lens.
We used the Keck-I telescope with the Low-Resolution Imaging Spectrograph (LRIS) (17)
with the upgraded red channel (18) to observe
the host galaxy and any foreground objects at the
sky position of PS1-10afx on 7 September 2013
(see fig. S1) (16). As illustrated in Fig. 1, there
are two narrow emission features that persist at
the location of PS1-10afx now that the supernova itself has faded away. The [O II] emission
doublet (ll = 3726.1, 3728.8 Å in the rest
frame) from the host galaxy previously identified (1) is clearly recovered (fig. S2), but we
additionally detected a second emission line at
~7890 Å. Because there are no strong emission
lines expected from the host at this wavelength
(~3300 Å in the host frame), this detection suggests the presence of a second object coincident
The most probable identification for the 7890 Å
feature is [O II] at z = 1.1168 T 0.0001. At this
redshift, other strong emission lines such as H-b
or [O III] would lie outside of our wavelength
coverage. However, as depicted in Fig. 1, we
detected a Mg II absorption doublet (ll = 2795.5,
2802.7 Å in the rest frame) at z = 1.1165 T 0.0001.
Blueshifted absorption outflows are typical of
star-forming galaxies (19), so this estimate is
compatible with that derived from the emission
lines. We also identify possible Mg I (l = 2853.0)
1Kavli Institute for the Physics and Mathematics of the Universe
(WPI), Todai Institutes for Advanced Study, The University of
Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8583,
Japan. 2Department of Physics, The University of Tokyo, Tokyo
113-0033, Japan. 3Argelander Institute for Astronomy, University of Bonn Auf dem Hügel 71, D-53121 Bonn, Germany.
4Research Center for the Early Universe, Graduate School of
Science University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-
0033, Japan. 5Department of Mathematics, Duke University,
Durham, NC 27708, USA. 6National Astronomical Observatory
of Japan 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan.
7Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho Sakyo-ku, Kyoto 606-8502, Japan.
*Corresponding author. E-mail: firstname.lastname@example.org