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Chapter 18
Supernovae
J. Craig Wheeler and Stefano Benetti
18.1
Spectral Types . . . . . . . . . . . . . . . . . . . . . . . 451
18.2
Older Population, Type Ia Supernovae . . . . . . . . . 452
18.3
Young Population Supernovae . . . . . . . . . . . . . . 454
18.4
SN 1987A . . . . . . . . . . . . . . . . . . . . . . . . . . 460
18.5
Characteristic Spectral Lines . . . . . . . . . . . . . . . 463
18.6
Radio Supernovae . . . . . . . . . . . . . . . . . . . . . 466
18.7
Polarization . . . . . . . . . . . . . . . . . . . . . . . . . 466
18.8
Supernova Rates . . . . . . . . . . . . . . . . . . . . . . 467
18.9
Old Supernovae, Historical Supernovae,
and Supernova Remnants . . . . . . . . . . . . . . . . . 468
18.10
Radioactive Decay . . . . . . . . . . . . . . . . . . . . . 468
Supernovae represent the catastrophic endpoint of evolution of stars. Study of them provides clues
to the progenitor evolution, to the explosion mechanism, to the origin of heavy elements, and
to their use as distance calibrators. To date around 1200 optical supernova outbursts have been
discovered, the vast majority in external galaxies. A catalog of supernovae is given by Barbon,
Cappellaro, and Turatto [1]. For access to supernova information on the World Wide Web, see
http://cssa.stanford.edu/marcos/sne.html.
18.1
SPECTRAL TYPES
Supernovae are primarily classified by their spectral evolution with complementary consideration of
their light curve morphology [2]. The traditional categories have been defined as Type II for those
451
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S UPERNOVAE
Spectra of SN at maximum
-30
SiII
-32
Ia
HeI
Ib
-34
CaII
OI
-36
CaII
-38
Ic
93J
II
-40
87A
-42
2000
4000
6000
8000
10000
Figure 18.1. Representative spectra near maximum light of Type Ia (SN 1992A [3]), SN 1993J [4], Type II plateau
(SN 1992H [5]), SN 1987A [6], Type Ib (SN 1984L [7, 8]), Type Ic (SN 1987M [9]).
that display conspicuous evidence for hydrogen and Type I for those that do not. Here the current
nomenclature is maintained that defines three categories of Type I, Types Ia, Ib, and Ic, according to the
major aspects of their spectral evolution. An accommodation of the suspected physical characteristics
of these categories is made by separating events that are associated with population I environments,
Type II, Type Ib and Type Ic, from the Type Ia supernovae that are generally associated with older
stellar populations. Figure 18.1 gives a sample of spectra for some recognizable categories near
maximum light. At this phase the spectra are predominantly composed of the blended P-Cygni profiles
of individual lines. In the later, nebular, phase the features are predominantly due to emission lines.
18.2
OLDER POPULATION, TYPE IA SUPERNOVAE
Type Ia supernovae appear in all morphological types of galaxies. In spiral galaxies they are
concentrated in spiral arms only to the extent that the oldest stars are [10, 11]. They show no correlation
with giant H II regions [12, 13]. They do not seem to be strongly associated with the halos or bulges of
spiral galaxies, and their properties may depend on the distance from the galactic center [14]. Type Ia
supernovae show no conspicuous evidence for hydrogen in the spectra at any phase. The majority
of Type Ia supernovae that have been observed to date show very similar light curves and spectral
evolution. Type Ia supernovae are characterized by elements of intermediate mass, O, Mg, S, Si, and
Ca, near maximum, and iron-peak elements, predominantly Fe II, beginning about 20 d after optical
maximum. Near maximum light, the blend of lines of Si II λ “6355” make a prominent P-Cygni
absorption with a minimum near 6150 Å. This feature is often taken as a defining characteristic of
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18.2 O LDER P OPULATION , T YPE I A S UPERNOVAE / 453
-18
-18
-16
-16
0
40
-14
SNIa
SNIb
-12
SN 1994I
SN 1993J
0
50
100
150
200
phase (days)
250
300
350
400
Figure 18.2. Composite V light curves of Type Ia, hydrogen-deficient events like Type Ib SN 1984L [8],
hydrogen- and helium-deficient events with steep late declines like Type Ic SN 1994I [28], and the transition
event SN 1993J [29]. For the Type Ia, b, c events H0 = 75 km s−1 Mpc−1 is assumed.
Type Ia supernovae, but care must be exercised not to confuse it with Hα in unreduced spectra. In the
later, nebular phase, the spectrum is dominated by [Fe II] and [Fe III], but continues to show Ca II in
absorption.
Type Ia supernovae are intrinsically the brightest class of supernovae. The peak blue magnitude
of a canonical Type Ia supernova is estimated to be −18.4 ± 0.3 + 5 log10 h where h is the Hubble
constant in units of 100 km s−1 Mpc−1 . The light curve consists of a peak about 30 d wide followed
by an exponential decline with a slope of 0.012–0.015 mag. d−1 . Type Ia supernovae are characterized
by a secondary maximum or inflection that extends from the V band to at least 2 µm about 20 d after
peak light [15]. No radio or X-ray emission has been detected from a Type Ia supernova. Type Ia
supernovae are apparently not strongly polarized in the continuum, but may show polarized spectral
features (see Table 18.3). A composite V light curve for Type Ia supernovae is given in Figure 18.2. A
composite spectral evolution of a typical Type Ia supernova is illustrated in Figure 18.3.
Definite departures from the canonical behavior of Type Ia supernovae have also been observed.
One extreme is represented by SN 1991T [16, 17] which was perhaps 0.6 mag. brighter in V at
maximum than a typical Type Ia supernova with a broader peak, bluer color, and slower decline from
maximum. SN 1991T showed Fe III features at maximum, but not the classical Si II λ6355 blend nor S
or Ca. The Si II feature was observed weaker than normal after maximum, as was Ca II. The secondary
infrared peak occurred later and dimmer than the average event. The other extreme is represented by
SN 1991bg [18, 19], which was dimmer by about 1.4 mag. in V at maximum than a typical Type Ia
supernova with a redder, narrower light curve peak and no evidence for a secondary infrared peak.
SN 1991bg had a distinct Ti II absorption trough at 4200 Å, a paucity of Fe features, and other spectral
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S UPERNOVAE
Spectral evolution of SNIa
-30
iron peak
elements
SiII
CaII MgII
SiII
SII SiII
SiII
OI
CaII
-32
-34
-36
-38
-40
-42
[FeIII]
[FeII]
-44
iron peak
elements
[FeII]
CaII
[CoIII]
-46
-48
2000
4000
6000
8000
10000
Figure 18.3. Composite spectral evolution of a typical Type Ia supernova. The data are a composite of SN 1992A
in the UV and optical [3] and SN 1989B [25] in the optical.
anomolies. It is not known at this time whether or not most Type Ia supernovae are intrinsically of the
canonical type with relatively small dispersion in properties and the exceptions are relatively rare, or
whether or not the distribution of Type Ia supernova is more uniformly populated between the extremes
of SN 1991bg and SN 1991T and the perception of a canonical type is due to selection effects.
The spectra and light curves of Type Ia supernovae are generally thought to be consistent with
a thermonuclear explosion of a white dwarf that leaves no compact remnant. The light curve is
thought to be powered by radioactive decay of 56 Ni and 56 Co (Table 18.7) produced in the explosion.
The progenitor evolution is thought to involve binary mass transfer onto a white dwarf, but no selfconsistent evolutionary scheme has been devised and no direct evidence for duplicity exists.
Prototype events are SN 1937C [20, 21], SN 1972E [22], SN 1981B [23], SN 1989B [24, 25],
SN 1992A [3, 26], SN 1991T [16, 17], SN 1991bg [18, 19], and SN 1994D [27].
18.3
18.3.1
YOUNG POPULATION SUPERNOVAE
Type II Supernovae
Type II supernovae are characterized by the evidence for hydrogen in their spectra. The Hα line
is prominent. In some cases the very early spectrum is principally a continuum and the Hα line
strengthens with time. For canonical Type II supernovae, the later, nebular phase is very different
from that of Type Ia supernovae, being dominated by Hα, Na D, [O I ] λλ 6300, 6364, [Ca II] λλ7291,
7323, and the Ca II IR triplet. Type II supernovae are associated with spiral arms and H II regions in
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-18
-17
-16
-15
0
-14
40
-12
SN II-P
SN II-L
SN 1987A
SN 1993J
-10
-8
0
100
200
300
phase (days)
400
500
600
Figure 18.4. Composite V light curves (assuming H0 = 75 km s−1 Mpc−1 ) for Type II plateau and linear
supernovae along with SN 1987A [36] and SN 1993J [29].
spiral galaxies and hence with population I stellar environments [12, 13]. None has yet been observed
in an elliptical galaxy. A number have been observed in radio (see Table 18.2) and X-rays, the emission
of which is attributed to interaction of the ejecta with circumstellar matter. Type II supernovae may
typically be polarized at the 1% level (see Table 18.3). Type II supernovae show a large range in
peak brightness from nearly as bright as a Type Ia supernova to considerably fainter. Typical Type II
supernovae are about 1.5 mag. dimmer than typical Type Ia. Type II supernovae have been subdivided
according to light curve and spectral behavior.
Plateau Type II supernovae are characterized by broad Hα and a light curve that shows a prominent
plateau. A characteristic light curve of a typical Type II plateau supernova is shown in Figure 18.4. The
Hα line generally shows a blue-shifted absorption with net emission in the strong emission component.
A representative spectral evolution is given in Figure 18.5. The plateau is reproduced in models in
which the explosion occurs in a red supergiant envelope. The plateau represents the phase when
a recombination wave moves inward in mass at nearly constant temperature, releasing the energy
deposited by the shock. The general interpretation is that these supernovae result from the explosion of
a red supergiant of moderately large mass, in excess of about 10M which retains a substantial portion
of its original mass in the hydrogen envelope. Prototype events are SN 1969L [30], SN 1986I [31],
SN 1988A [32], SN 1990E [33, 34], and SN 1992H [5].
Type II linear supernovae are characterized by broad hydrogen lines and an exponential decline by
about 5 magnitudes in 100 d after maximum with little or no evidence of a plateau. These events may
be distinct from the plateau events or the extremum of a continuous distribution of properties. In some
linear Type II supernovae, SN 1979C and SN 1980K, the Hα line shows no blue-shifted absorption.
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S UPERNOVAE
Spectral evolution of SNII
HeI
CaII
FeII
TiII
-35
FeII
FeII
NaI
CaII
-40
MgI]
[FeII]
[OI]
CaII]
[OII]
CaII
FeII [FeII]
NaI
[FeII]
-45
4000
6000
8000
10000
Figure 18.5. Spectral evolution of a typical Type II plateau, SN 1992H [5]. The first spectrum is from SN 1988A
(McDonald Observatory, unpublished).
The Hα flux in SN 1980K showed an exponential decline for 2 to 3 years after outburst, but then leveled
out. It has been constant for years [35]. There is some evidence that the peak luminosity of most linear
events is rather homogeneous with SN 1979C being an especially bright exception [37]. Most of these
events are about 1.5 mag. dimmer than a typical Type Ia supernova, but SN 1979C was comparable
in brightness. A characteristic light curve for the more common, dimmer Type II linear supernova is
given in Figure 18.4. The statistics are poor, especially on the tail, so this composite light curve must
be regarded as provisional. The lack of a distinct plateau in the linear events is generally interpreted as
evidence for a rather small hydrogen envelope, perhaps a few M . There is no accepted interpretation
for the origin of the implied mass loss. There is some evidence from the modeling of light curves that
the outer envelopes of linear events are helium rich. SN 1990K [38] shows evidence for a substantial
helium mantle. Prototype events are SN 1979C [39], SN 1980K [40], and SN 1990K [38].
Some Type II supernovae are characterized by narrow emission lines superposed on the normal
broad Balmer lines, especially Hα. The narrow component is interpreted as emission from a
surrounding circumstellar nebula. An example is SN 1987F [41]. Some events with narrow lines
also show a very slow decay. An example is SN 1988Z [42, 43]. Such events are thought to derive a
substantial portion of their optical emission from circumstellar interaction.
Despite its historically bright apparent magnitude, SN 1987A (see Section 18.4) established that
there is a class of Type II supernovae that are intrinsically subluminous. This is interpreted as requiring
a relatively compact structure, e.g., a blue supergiant, so that the initial shock energy is dissipated
in adiabatic expansion. The resulting light curve displays a peak that is delayed from the time of
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Spectral evolution of SN 1993J
-28
HeI
CaII
CaII
-30
-32
HeI [OI]
FeII
HeI
HeI HeI
HeI
OI
-34
OI
-36
-38
-40
-42
MgI]
[FeII]
[OI]
-44
NaI
CaII]
[FeII] [OII]
CaII
OI
-46
4000
6000
8000
10000
Figure 18.6. Spectral evolution of SN 1993J [4].
explosion by months and that is powered entirely by radioactive decay. In practice, it is somewhat
difficult to identify such events because intrinsically low luminosity must be differentiated from
galactic extinction.
A number of supernovae, e.g., SN 1987K [44] and SN 1993J [4, 29] (also SN 1996B and
SN 1996cb), have been observed to make a transition from an early photospheric phase that shows
strong evidence of the Balmer lines of hydrogen but little evidence of helium to a later phase that
shows evidence for He I as well. In the nebular phase there is little or no evidence for spectral features
of either H or He in SN 1987K, although SN 1993J continued to show a shell of Hα in emission.
SN 1954A showed evidence for both Balmer lines and He I lines near maximum and hence might be
a candidate for this category [45]. The fading of the high-excitation He I lines may be predominantly
an excitation effect, but the early appearance of He I lines and the fading of the Balmer lines in the
nebular phase are interpreted as requiring a relatively small hydrogen envelope, perhaps a few tenths
of M , compared to the canonical Type II supernova. The spectral evolution of SN 1993J is shown
in Figure 18.6. Both SN 1987K and SN 1993J had light curves with relatively narrow peaks. The
V magnitude light curve of SN 1993J is shown in Figures 18.2 and 18.4 in contrast to canonical
Type I and Type II supernovae, respectively. Note that SN 1993J showed an early spike due to shock
breakout followed by a primary maximum about 30 days later. Spectropolarimetry and line profiles for
SN 1993J suggest spatial asymmetries in the explosion. Theoretical models suggest an origin in the
evolved primary in a binary system, but there is no firm evidence for duplicity at this writing.
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S UPERNOVAE
Spectral evolution of SNIb
CaII
FeII
FeII
-32
HeI
SiII HeI
-34
HeI
HeI
-36
-38
[OI]
-40
[OI]
MgI]
[FeII]
NaI
CaII]
[OII]
-42
-44
3000
4000
5000
6000
7000
8000
Figure 18.7. Spectral evolution of the prototype Type Ib, SN 1984L [8]. The last spectrum is from SN 1983N [47].
18.3.2
Hydrogen- and Helium-Deficient Supernovae
Some supernovae associated with young population environments are characterized as Type I in
terms of the most obvious aspect of their spectral evolution, the absence of conspicuous evidence
for hydrogen, but in many ways are generically related to Type II events.
Supernovae classified as Type Ib are characterized by the absence of conspicuous Balmer lines near
maximum but the presence of strong absorption lines of He I in the month or so after maximum. Some
weak, broad Hα may be present [46]. The late emission line phase is very reminiscent of canonical
Type II supernovae, but with no detectable optical evidence for either H or He. The nebular spectrum
shows strong lines of [Mg I] λ4571, Na D, [O I] λλ 6300, 6364, [Ca II] λλ 7291, 7323, and the Ca II
IR triplet. Only a few cases of Type Ib are known that can be identified by the presence of strong He I
lines in the optical spectrum. Among these are SN 1983N and SN 1984L. SN 1985F is often put in this
class because of the shape of its optical light curve and the nature of its late-time spectrum, but there
were no spectral observations near maximum so an ambiguity remains. SN 1990W is another possible
candidate. The spectral evolution of SN 1984L is shown in Figure 18.7. Radio emission was detected
from SN 1983N and SN 1984L, suggesting the presence of a rather substantial circumstellar medium
(see Table 18.2), but no radio emission was observed from SN 1985F.
The light curves of these helium-rich events tend to be dimmer and redder than Type Ia at maximum
and show some dispersion in the width of the peak of the light curve and the slope of the tail. These
events do not show the secondary maximum in the IR that characterizes Type Ia supernovae. On the
tail, SN 1984L and SN 1985F showed a flat decline of 0.01 mag. d−1 , near that expected for the decay
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Spectral evolution of SN 1987M
-32
CaII
FeII
FeII
NaI
SiII
OI
CaII
-34
-36
-38
MgI]
-40
[OI]
CaII]
NaI
CaII
[OII]
-42
4000
6000
8000
10000
Figure 18.8. Spectral evolution of a well-studied Type Ic supernova, SN 1987M [9].
of 56 Co as shown in the composite V light curve given in Figure 18.2. SN 1983N showed a somewhat
steeper decline of 0.013 mag. d−1 very similar to that of SN 1993J. This steeper decay may represent
in part a smaller ejecta mass to trap γ -rays, but other factors may be involved.
The association of Type Ib with spiral arms and H II regions [12, 13] suggest that these heliumrich events arise from relatively massive stars of population I and that they undergo explosion by core
collapse. There is no direct evidence for the latter. Association of the helium-rich events with Wolf–
Rayet and other helium star progenitors has been discussed, but not proven. Binary mass transfer
and stellar winds are thought to play a role in the loss of the hydrogen envelope. There is no direct
evidence for duplicity. The weak or absent evidence for H near maximum suggests that these events
had substantially less remaining H than even the transition events like SN 1993J.
Prototype events are SN 1983N [7] and SN 1984L [8].
Helium-deficient events spectrally classified as Type Ic are characterized by the absence of evidence
for both H and He in optical spectra both near maximum and in the month or two after maximum when
H is strong in the transition events like SN 1993J and He I is strong in the helium-rich events like
SN 1984L. High velocity He I λ10830 was observed near maximum in SN 1994I, so Type Ic cannot
be completely helium deficient [48, 49]. Near maximum the spectrum is characterized by a strong
absorption of O I λ7774, absorption of Si II λ6355 that is considerably weaker than that for Type Ia,
and otherwise by features that are mostly blends of Fe II. In the nebular emission line phase, the spectra
resemble those of the helium-rich events. The spectral evolution of Type Ic SN 1987M is shown in
Figure 18.8.
The light curves of the helium-deficient events are similar to the helium-rich events in magnitude
and color near maximum, but essentially all well-studied events initially decline more rapidly from
maximum than either Type Ia or Type Ib supernovae. Some Type Ic supernovae have relatively shallow
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S UPERNOVAE
Figure 18.9. Spectral evolution of SN 1987A [53].
late-time decay very similar to SN 1993J and the Type Ib events in this light curve category. Other
spectrally identified Type Ic events show late-time light curves with some dispersion but with declines
even steeper than Type Ia supernovae. There are perceptible differences in spectral details, but spectral
characteristics are as yet inadequate to categorize the light curve behavior. An example of a Type Ic
with rapid decline, SN 1994I [28], is given in Figure 18.2.
Circumstantial evidence suggests that Type Ic supernovae explode by core collapse, but again there
is no firm evidence. The spectral evolution is qualitatively consistent with a progenitor that has lost
both its hydrogen and helium envelopes. Again duplicity may play a role and there may be a connection
with Wolf–Rayet or other helium stars, but neither has been confirmed.
Prototype events are SN 1983I [50], SN 1983V [50], SN 1987M [9], and SN 1994I [28, 46, 48, 49].
18.4
SN 1987A
Supernova 1987A in the Large Magellanic Cloud was observed throughout the electromagnetic
spectrum and was a detected source of neutrinos. Reviews are given by Arnett et al. [36], Hillebrandt
and Höflich [51], Imshennik and Nadyozhin [52], McCray [53], and Phillips and Suntzeff [54].
Figure 18.9 shows the spectral evolution from the UV to the far infrared. Line profiles in the
early phase indicate velocities up to 25 000 km s−1 , and the emission during the nebular phase is
characterized by velocities 2500 km s−1 . The optical spectrum was comparable to other Type II
supernovae (Figure 18.1). The spectrum gives evidence for mixing of hydrogen and helium at the
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UVOIR Light Curve of SN 1987A
42
41
40
39
38
Crab Nebula Limit
37
36
0
200
400
600
800
1000
1200
days since outburst
1400
1600
1800
Figure 18.10. Bolometric light curve of SN 1987A. (Courtesy of N. Suntzeff.)
core/envelope interface and for outward mixing of 56 Ni. This mixing may be macroscopic rather
than microscopically homogeneous. The IR spectra showed evidence for molecules, especially carbon
monoxide and silicon monoxide.
There was evidence for dust formation beginning at about 450 days after the explosion. The dust
appears to have two components, small grains distributed diffusely that affect short wavelengths and
clumps of very optically thick grains the effect of which is wavelength independent. The rate of
decline of the light curve decreased after 1000 days, which may be explained by time-dependent
recombination. The V light curve is given in Figure 18.4 and the bolometric light curve in Figure 18.10.
Figure 18.11 gives the B − V color evolution for SN 1987A in comparison with canonical Type Ia,
Type II supernovae, and SN 1993J. The precursor star, Sk–69◦ 202, was identified but not especially
well studied. The fact that the precursor was a blue supergiant accounted for the unorthodox light
curve, although the physical reasons for its explosion in this state are still uncertain. The detection of
neutrinos confirmed the basic process of core collapse. The information content was not sufficient
to usefully constrain the explosion mechanism. At this writing, there is no direct evidence for a
compact object. Such a compact remnant, if it exists, must have a bolometric luminosity less than a few
times 1036 erg s−1 , less than about 10% that of the Crab Nebula. The extended neutrino (antielectron
neutrino) signal demands that a neutron star remained for about 10 s, but the eventual collapse to form
a black hole cannot be precluded.
SN 1987A also provided the first unambiguous test of the theoretically predicted production of
56 Ni, and its radioactive decay into 56 Co and then 56 Fe (Table 18.7). The evidence for this decay was
contained in the bolometric light curve, the slope of which closely matched that expected for the Co
decay from 125 to 450 d after the explosion, in the detection of the infrared lines of [Co II] at 1.547 µm
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S UPERNOVAE
B-V curves for different SN types
SN 1987A
SN 1993J
SN Ia
SN IIP
1.5
1
.5
0
0
100
200
300
days after explosion
400
500
Figure 18.11. The evolution of B − V color for SN 1987A and SN 1993J in comparison with mean curves
representing Type Ia and plateau Type II events.
and 10.52 µm and in the direct detection of γ -ray lines of 56 Co and 57 Co. The 56 Co was first detected
at about 160 d after outburst and 57 Co was detected at 1500 d. The ratio of these lines implies a ratio
of the final stable decay products of about 1.5 times the solar value.
Based on the known distance of the Large Magellanic Cloud, the bolometric luminosity of the
progenitor is computed to be about 100 000L . Invoking structural models, this luminosity implies
a helium core mass of about 6M . Standard evolutionary models predict that such a star would
have a mass of about 20M on the main sequence, but some mixing theories give this core mass
for lower initial masses, so the total initial mass is somewhat uncertain. Fits to the light curve
and spectral evolution suggest a hydrogen envelope mass of ∼ 10M at the time of the explosion.
Various arguments suggest that the envelope was helium-enriched with a mass fraction Y ∼ 0.4. The
helium enrichment, enhancement of barium, an s-process element, and the circumstellar rings raise the
possibility that the precursor accreted mass from a binary companion, but there is no definite evidence
for present or past duplicity.
Early radio emission is interpreted as evidence for interaction of the ejecta with circumstellar
matter. Radio flux was first detected on day 2 and reached a peak flux of Sν (2 GHz) ≈ 130 mJy
on day 3. Renewed detection occurred 1200 d after the explosion, reached Sν (4.8 GHz) ≈ 11 mJy by
day 2050 and continued to rise at about 15% per year a decade after the explosion.
Hard X-ray emission was observed beginning about 130 d after explosion, reaching a peak about
day 320. This is interpreted as resulting from Compton down scattering of γ -rays within the ejecta.
The maximum flux in lines of 56 Co at 0.847 and 1.238 MeV also peaked about the same time. Transient
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soft X-ray emission was also reported, the origin of which is not well explained, but thought to arise
from collision of the ejecta with circumstellar clumps. Soft X-ray emission began to rise again along
with the radio about 1200 days after the explosion, reached a luminosity of L X ∼ 3 × 1034 erg s−1 a
decade after the explosion, and continued to increase.
SN 1987A was surrounded by a complex circumstellar environment. The principal feature is the
ring of matter that fluoresces as a result of excitation by the UV emission from the supernova at shock
breakout and emits strongly in UV and optical emission lines. Two fainter rings and more complex
structures are also present.
There is a significant population of both red and blue supergiants in the Large Magellanic Cloud.
The evolutionary state of the blue supergiants is not well established. The nitrogen-rich, narrow
fluorescent emission line spectrum from the circumstellar ring around SN 1987A is widely regarded
as evidence for the collision of a blue supergiant wind with a previous, slower red supergiant wind
and hence evidence that the progenitor was once a red supergiant. The unexplained origin of the ring
geometry and the possibility of mixing in early evolutionary phases leave some room for question.
Some models propose that the ring is a protostellar remnant or an unbound excretion disk.
Here are summarized some of the properties deduced for SN 1987A:
Progenitor: SK −69◦ 202 spectral type B3 I.
MV = 12.29 ± 0.04; M B = 12.32 ± 0.06.
R = (3 ± 1) × 1012 cm; Teff = 16 500 ± 1500 K.
L = (4.5 ± 1.5) × 1038 erg s−1 .
Main sequence mass = (15–20)M .
Helium core mass = (6 ± 1) M .
Hydrogen envelope mass at explosion ∼ 10M .
Explosion:
Kinetic energy = (1.3 ± 0.2) × 1051 erg.
Total neutrino energy = (2 ± 1) × 1053 erg.
Neutrino temperature = (4 ± 1) MeV.
Mean neutrino energy = 12.5 ± 3.0 MeV.
Mass of 56 Ni = (0.069 ± 0.003)M .
Detected γ -ray lines: 56 Co 0.847, 1.238, 2.599, 3.250 MeV; 57 Co 122, 136 keV.
Polarization:
Position angle ∼ 120◦ .
Percent polarization = 0.6 (V band, day 40).
Circumstellar ring:
Semimajor axis = 0.858 ± 0.011 arcsec = 6.4 × 1017 cm at 50 pc.
Width = 0.122 ± 0.022 arcsec = (9.0 ± 1.6) × 1016 cm at 50 kpc.
Tilt angle = 44 ± 1◦ .
Position angle major axis = 89◦ ± 3◦ .
Expansion velocity 10.3 km s−1 .
18.5
CHARACTERISTIC SPECTRAL LINES
Table 18.1 gives the wavelength in nanometers of characteristic lines observed in the early photospheric
and later nebular phases of various types of supernovae.
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S UPERNOVAE
Table 18.1. Characteristic spectral features of various supernova types.
Photospheric phase
Nebular phase
Type Ia
UV: blends of Fe II, Ni II, Ti II, V II, Co II, Cr II [1]
Mg II 279.8
Si III 385.9
Ca II H&K 393.4, 396.8
Si II 413.0
Fe II “422.0”
Fe II 435.2
Mg II 448.1
Si III 456.0
Fe I “456.8”
Fe III “440.4”
Fe II “455.5”
Fe II 492.4, 501.8
Si II “505.1”
Fe III “512.9”
Fe II 516.9
Fe II “521.5”
Fe II 553.5
S II “546.8,” “561.2,” “565.4”
Na I 589.0, 589.6
UV: blends of [Fe II, III, IV], [Co III](?), [Ni II](?) [2]
Ca II H&K 393.4, 396.8
blends of [Fe III] 450–480
Na I 589.0, 589.6(?)
[Co III] 589.0, 590.8
Si II “597.2”
Si II “635.5”
O I 777.4
Ca II 849.8, 854.2, 866.2
OI 926.1, 926.3, 926.6
Type Ib and Ic
UV: blends of iron peak elements
Ca II H&K 393.4, 396.8
Mg II 448.1a
Fe II “440.4”
Fe II “455.5”
Fe II 492.4, 501.8, 516.9
He I 447.1, 501.5, 587.6, 667.8, 706.5, 728.3, 1083a
Na I 589.0, 589.6
[Mg I] 457.1
Fe II 492.4, 501.8, 516.9
Na I 589.0, 589.6
[O I ] 557.7
[O I] 630.0, 636.4
Si II 635.5
C II 658.0
O I 777.4
Ca˙II 849.8, 854.2, 866.2
[Ca II] 729.1, 732.3
[O II] 732.0, 733.0
O I 777.4
O I 844.6
Ca II 849.8, 854.2, 866.2
[C I] 873.0(?)
[O I] 926.1, 926.3, 926.6
[C I] 982.4, 985.0
[Fe II], Si I 1.644 µm
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18.5 C HARACTERISTIC S PECTRAL L INES / 465
Table 18.1. (Continued.)
Photospheric phase
Nebular phase
Type II and SN 1987A
UV: blends of iron peak elements
blends of [Fe II] 240–570 [3]b
Mg II 279.5, 280.2
Mg I 285.2b
[O II] 372.6, 372.8b
Mg II 448.1
Ca II H&K 393.4, 396.8
Sr II 407.7, 421.5b
Ca I 422.6b
Ba II 455.4, 493.4b
Mg I] 457.1
Sc II 467.0b
Fe II 492.4, 501.8, 516.9
Fe I 526.9
Sc II 552.7, 565.8b
Ba I 553.5b
[O I] 557.7
Ba II 585.4b
He I 587.6, 1083.0
Na I 589.0, 589.6
Ba II 614.2b
Sc II 624.5
Hα, Hβ, Hγ , Hδ, H
Ca II 849.8, 854.2, 866.2
Sr II 1.033 µm
Notes
a Especially in Type Ib.
b Especially in SN 1987A.
References
1. Kirshner, R.P. et al. 1993, ApJ, 415, 589
2. Ruiz-Lapuente, P. et al. 1995, ApJ, 439, 60
3. Wang, L. et al. 1996, ApJ, 466, 998
Na I 589.0, 589.6
[O I] 630.0, 636.4
Hα, Hβ, Hγ
[Fe II] 700.0–950.0 blends
[Fe II] 715.5
Ca II] 729.1, 732.3
[O II] 732.0, 733.0
Ca II 849.8, 854.2, 866.2
[C I] 873.0
[C I] 982.4, 985.0
Paα, Paβ, Paγ , Paδ, Pa
Brα, Brβ, Brγ
Pfγ , Pfδ
O I 1.129 µm
[Fe II] 1.257 µmb
[Fe II] 1.533 µmb
[Co II] 1.547 µmb
[Fe II] Si I 1.644 µmb
[Ni] 3.119 µmb
[Ni II] 6.634 µmb
[Ar II] 6.983 µmb
[Co II] 10.52 µmb
[Fe II] 17.93 µmb
SiOb
COb
Dustb
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18.6
S UPERNOVAE
RADIO SUPERNOVAE
Table 18.2 gives supernovae that have been observed in the radio range [55].
Table 18.2. Radio supernovae.
18.7
Supernova
Type
Galaxy
1923A
1950B
1957D
1961V
1968D
1970G
1978K
1979C
1980K
1981K
1982aa
1983N
1984L
1985L
1986E
1986J
1987A
1988Z
1990B
1992ad
1993J
1994I
1995N
1996N
1996cb
1997X
II plateau
II ?
Unknown
II peculiar
II
II linear?
II
II linear
II linear
II
II
Ib
Ib
II linear
II linear
II
II peculiar
II narrow line
Ic
II
II transition
Ic
II
Ib
II transition
Ic
NGC 5236
NGC 5236
NGC 5236 (M83)
NGC 1058
NGC 6946
NGC 5457 (M101)
NGC 1313
NGC 4321 (M100)
NGC 6946
NGC 4258
NGC 6464
NGC 5236 (M83)
NGC 991
NGC 5033
NGC 4302
NGC 891
LMC
MCG 03-28-022
NGC 4568
NGC 4411B
NGC 3031 (M81)
NGC 5194
MCG-2-38-017
NGC 1398
NGC 3510
NGC 4691
POLARIZATION
Table 18.3 gives data on supernovae for which polarization information has been obtained.
Table 18.3. Polarization of supernovae [1, 2].
Supernova
Type
Polarization (%)
1968L
1970G
1972E
1975N
1981B
1983G
1983N
1986G
1987A
1992A
1993J
1994D
1994Y
1994ae
1995D
II
II
Ia
Ia
Ia
Ia
Ib
Ia
II peculiar
Ia
II transition
Ia
II narrow line
Ia
Ia
Undetermined
0.5
Undetermined
< 0.3
Undetermined
< 0.5
Detected
< 0.1
0.6
< 0.3
1.0 [3]
< 0.3
1.5
< 0.3
< 0.2
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18.8 S UPERNOVA R ATES / 467
Table 18.3. (Continued.)
Supernova
Type
Polarization (%)
1995H
1995V
1996W
1996X
1997cb
1997X
1997Y
1997bp
1997bq
1997br
II
II
II
Ia
II transition
Ic
Ia
Ia
Ia
Ia
1.0
1.5
0.7
0.3
1.5
1.5
< 0.3
0.6
< 0.3
< 0.3
References
1. Wang, L., Wheeler, J.C., Li, Z., & Clocchiatti, A. 1996, ApJ, 467, 435
2. Wang, L., Wheeler, J.C., & Höflich, P. 1997, ApJ, 476, L27
3. Tran, H.D. et al. 1997, PASP, 109, 489
18.8
SUPERNOVA RATES
The deduced rate of explosion of supernovae of different types in galaxies of different morphological
type must allow for varying visibility due to absolute brightness and light curve width in estimating the
probability of detection. Poor statistics make these estimates uncertain. Because of the large variation
of supernova rates among galaxies of differing morphological type, some normalizing procedure must
be adopted. Table 18.4 gives the estimated rates of supernovae of various spectral types normalized
to the blue luminosity of the host galaxy in units of 1010 L as a function of the morphological type
of the galaxy. Other estimates are given by van den Bergh and Tammann [56] and van den Bergh and
McClure [57]. Assuming that the Galaxy is an Sb with a blue luminosity of 2.0 ± 0.6 × 1010 L , the
number of supernovae per century are estimated to be: Type Ia—0.3 ± 0.2; Type Ib/Ic—0.2 ± 0.2;
Type II—1.7 ± 0.9 [58].
Table 18.4. Supernova rates per 100 yrs per 1010 L B luminosity [1, 2].a
Galaxy Type
Ia
Ib and Ic
II
E
S0
S0a, Sa
Sab, Sb
Sbc
Sc
Scd, Sc
Sdm-Im
0.11
0.15
0.30
0.12
0.22
0.50
0.48
0.20
0.15
0.12
0.10
0.54
0.09
0.30
0.19
0.36
1.19
1.45
1.87
0.40
E, S0
S0a-Sb
Sbc-Sd
0.15 ± 0.06
0.20 ± 0.07
0.24 ± 0.09
< 0.3
0.11 ± 0.06
0.16 ± 0.08
< 0.3
0.40 ± 0.19
0.88 ± 0.37
Notes
a All rates are proportional to (H /75 km s−1 Mpc−1 )2 .
0
References
1. Cappellaro, E., Turatto, M., Benetti, S., Tsvetkov, D.Yu., Bartunov,
O.S., & Makarova, L.N. 1993, A&A, 273, 383
2. Cappellaro, E., Turatto, M., Tsvetkov, D.Yu., Bartunov, O.S., Pollas,
C., Evans, R., & Hamuy, M. 1997, A&A, 322, 431
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S UPERNOVAE
18.9 OLD SUPERNOVAE, HISTORICAL SUPERNOVAE,
AND SUPERNOVA REMNANTS
Table 18.5 gives supernovae that have been observed over 5 years after explosion. These may be
regarded as supernovae very late in the nebular phase or as very young supernova remnants.
Over 175 high-surface-brightness supernova remnants have been observed in the optical, radio,
and X-ray spectra in the Galaxy. A few dozen have been observed in other galaxies, especially
the Magellanic Clouds, Andromeda, M33, and M82. A catalog of supernova remnants is given by
Green [59]. Table 18.6 gives information on supernovae observed in the historical past.
Table 18.5. Long-lived supernovae.
Supernova
Type
Galaxy
1885A
1957D
1968D
1961V
1970G
1978K
1979C
1980K
1986J
1987A
1988Z
I?
II?
II
II peculiar
II linear(?)
II
II linear
II linear
Unknown
II peculiar
II narrow line
M31
NGC 5236 (M83)
NGC 6946
NGC 1058
NGC 5457 (M101)
NGC 1313
NGC 4321 (M100)
NGC 6946
NGC 891
LMC
MCG-03-28-022
Table 18.6. Historical supernovae.
18.10
Event
Extended remnant
Compact remnant
185
1006
1054 (Crab Nebula)
1572 (Tycho)
1604 (Kepler)
∼ 1670 (Cas A)
Shell, Balmer dominated
Filled, helium-rich
Shell, Balmer dominated
Shell, Balmer dominated
Oxygen rich knots, He, N-rich, quasistationary flocculi
33 msec pulsar
RADIOACTIVE DECAY
A principal source of power of the light curve peak and especially the late-time tail of many supernovae
is the decay of radioactive 56 Ni and its daughter 56 Co. Other radioactive species that may contribute
late-time power are 57 Co and 44 Ti. The decay rates for these species are given in Table 18.7.
Table 18.7. Radioactive decay time scales in supernovae.
Element
Half-life
e-Fold
Per magnitude
56 Ni [1]
6.10 d
77.12 d
271.8 d
54.2 yr
8.80 d
111.3 d
392.1 d
78.2 yr
8.11 d
102.3 d
361.2 d
72.0 yr
56 Co [1]
57 Co [2]
44 Ti [3]
References
1. Huo, J. et al. 1987, Nuclear Data Sheets, 51, 1
2. Burrows, T.W., & Bhat, M.R. 1986, Nuclear Data Sheets, 47, 1
3. Frekers, D. et al. 1983, Phys. Rev. C, 28, 1756
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