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A. Melandri,
E. Pian,
P. Ferrero,
V. D'Elia,
E. S. Walker,
G. Ghirlanda,
S. Covino,
L. Amati,
P. D'Avanzo,
P. A. Mazzali, [......],
K. Nomoto,
E. Palazzi,
F. Patat,
S. Piranomonte,
R. Salvaterra,
I. Saviane,
R. L. C. Starling,
G. Tagliaferri,
M. Tanaka,
S. D. Vergani
[show abstract]
[hide abstract]
ABSTRACT: The association of Type Ic SNe with long-duration GRBs is well established.
We endeavor, through accurate ground-based observational campaigns, to
characterize these SNe at increasingly high redshifts. We obtained a series of
optical photometric and spectroscopic observations of the Type Ic SN2012bz
associated with the Swift long-duration GRB120422A (z=0.283) using the 3.6-m
TNG and the 8.2-m VLT telescopes. The peak times of the light curves of
SN2012bz in various optical filters differ, with the B-band and i'-band light
curves reaching maximum at ~9 and ~23 rest-frame days, respectively. The
bolometric light curve has been derived from individual bands photometric
measurements, but no correction for the unknown contribution in the
near-infrared (probably around 10-15%) has been applied. Therefore, the present
light curve should be considered as a lower limit to the actual UV-optical-IR
bolometric light curve. This pseudo-bolometric curve reaches its maximum (Mbol
= -18.56 +/- 0.06) at 13 +/- 1 rest-frame days; it is similar in shape and
luminosity to the bolometric light curves of the SNe associated with z<0.2 GRBs
and more luminous than those of SNe associated with XRFs. A comparison with the
model generated for the bolometric light curve of SN2003dh suggests that
SN2012bz produced only about 15% less 56Ni than SN2003dh, about 0.35 Msol.
Similarly the VLT spectra of SN2012bz, after correction for Galactic extinction
and for the contribution of the host galaxy, suggest comparable explosion
parameters with those observed in SN2003dh (EK~3.5 x 10^52 erg, Mej~7 Msol) and
a similar progenitor mass (~25-40 Msol). GRB120422A is consistent with the
Epeak-Eiso and the EX,iso-Egamma,iso-E_peak relations. GRB120422A/SN2012bz
shows the GRB-SN connection at the highest redshift so far accurately monitored
both photometrically and spectroscopically.
06/2012;
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[show abstract]
[hide abstract]
ABSTRACT: The unusual helium-rich (type Ib) supernova SN 2005E is distinguished from all supernovae hitherto observed by its faint and rapidly fading light curve, prominent calcium lines in late-phase spectra and lack of any mark of recent star formation near the supernova location. These properties are claimed to be explained by a helium detonation in a thin surface layer of an accreting white dwarf. Here we report that the observed properties of SN 2005cz, which appeared in an elliptical galaxy, resemble those of SN 2005E. We argue that these properties are best explained by a core-collapse supernova at the low-mass end (8-12 solar masses) of the range of massive stars that explode. Such a low-mass progenitor lost its hydrogen-rich envelope through binary interaction, had very thin oxygen-rich and silicon-rich layers above the collapsing core, and accordingly ejected a very small amount of radioactive (56)Ni and oxygen. Although the host galaxy NGC 4589 is an elliptical, some studies have revealed evidence of recent star-formation activity, consistent with the core-collapse model.
Nature 05/2010; 465(7296):326-8. · 36.28 Impact Factor
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A Gal-Yam,
P Mazzali,
E O Ofek,
P E Nugent,
S R Kulkarni,
M M Kasliwal,
R M Quimby,
A V Filippenko,
S B Cenko,
R Chornock, [......],
A J Drake,
R C Thomas,
J S Bloom,
D Poznanski,
A A Miller,
R J Foley,
J M Silverman,
I Arcavi,
R S Ellis, J Deng
[show abstract]
[hide abstract]
ABSTRACT: Stars with initial masses such that 10M[symbol: see text] <or= M(initial) <or= 100M[symbol: see text], where M[symbol: see text] is the solar mass, fuse progressively heavier elements in their centres, until the core is inert iron. The core then gravitationally collapses to a neutron star or a black hole, leading to an explosion-an iron-core-collapse supernova. By contrast, extremely massive stars with M(initial) >or= 140M[symbol: see text] (if such exist) develop oxygen cores with masses, M(core), that exceed 50M[symbol: see text], where high temperatures are reached at relatively low densities. Conversion of energetic, pressure-supporting photons into electron-positron pairs occurs before oxygen ignition and leads to a violent contraction which triggers a nuclear explosion that unbinds the star in a pair-instability supernova. Transitional objects with 100M[symbol: see text] < M(initial) < 140M[symbol: see text] may end up as iron-core-collapse supernovae following violent mass ejections, perhaps as a result of brief episodes of pair instability, and may already have been identified. Here we report observations of supernova SN 2007bi, a luminous, slowly evolving object located within a dwarf galaxy. We estimate the exploding core mass to be M(core) approximately 100M[symbol: see text], in which case theory unambiguously predicts a pair-instability supernova. We show that >3M[symbol: see text] of radioactive (56)Ni was synthesized during the explosion and that our observations are well fitted by models of pair-instability supernovae. This indicates that nearby dwarf galaxies probably host extremely massive stars, above the apparent Galactic stellar mass limit, which perhaps result from processes similar to those that created the first stars in the Universe.
Nature 12/2009; 462(7273):624-7. · 36.28 Impact Factor
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K. S. Kawabata,
D. J. Jeffery,
M. Iye,
Y. Ohyama,
G. Kosugi,
N. Kashikawa,
N. Ebizuka,
T. Sasaki,
K. Sekiguchi,
K. Nomoto, [......],
K. Ota,
T. Ozawa,
Y. Shimizu,
H. Taguchi,
Y. Yadoumaru,
T. Misawa,
F. Nakata,
T. Yamada,
I. Tanaka,
and T. Kodama
[show abstract]
[hide abstract]
ABSTRACT: We present spectropolarimetry of the Type Ic supernova SN 2002ap and give a preliminary analysis: the data were taken at two epochs, close to and 1 month later than the visual maximum (2002 February 8). In addition, we present June 9 spectropolarimetry without analysis. The data show the development of linear polarization. Distinct polarization profiles were seen only in the O I λ7773 multiplet/Ca II IR triplet absorption trough at maximum light and in the O I λ7773 multiplet and Ca II IR triplet absorption troughs a month later, with the latter showing a peak polarization as high as ~2%. The intrinsic polarization shows three clear position angles: 80° for the February continuum, 120° for the February line feature, and 150° for the March data. We conclude that there are multiple asymmetric components in the ejecta. We suggest that the supernova has a bulk asymmetry with an axial ratio projected on the sky that is different from 1 by an order of 10%. Furthermore, we suggest very speculatively that a high-velocity ejecta component moving faster than ~0.115c (e.g., a jet) contributes to polarization in the February epoch.
The Astrophysical Journal 12/2008; 580(1):L39. · 6.02 Impact Factor
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K. S. Kawabata, J. Deng,
L. Wang,
P. Mazzali,
K. Nomoto,
K. Maeda,
N. Tominaga,
H. Umeda,
M. Iye,
G. Kosugi, [......],
N. Kobayashi,
Y. Komiyama,
Y. Mizumoto,
J. Noumaru,
R. Ogasawara,
K. Sekiguchi,
Y. Shirasaki,
T. Totani,
J. Watanabe,
and T. Yamada
[show abstract]
[hide abstract]
ABSTRACT: Spectroscopic and spectropolarimetric observations of SN 2003dh/GRB 030329 obtained in 2003 May using the Subaru 8.2 m Telescope are presented. The properties of the supernova (SN) are investigated through a comparison with spectra of the Type Ic hypernovae SN 1997ef and SN 1998bw (hypernovae being a tentatively defined class of SNe with very broad absorption features: these features suggest a large velocity of the ejected material and possibly a large explosion kinetic energy). Comparison with spectra of other hypernovae shows that the spectrum of SN 2003dh obtained on 2003 May 8 and 9, i.e., 34-35 rest-frame days after the gamma-ray burst (GRB; for z = 0.1685), are similar to those of SN 1997ef obtained ~34-42 days after the fiducial time of explosion of that SN. The match with SN 1998bw spectra is not as good (at rest 7300-8000 Å), but again spectra obtained ~33-43 days after GRB 980425 are preferred. This indicates that the SN may have intermediate properties between SNe 1997ef and 1998bw. On the basis of the analogy with the other hypernovae, the time of explosion of SN 2003dh is then constrained to be between -8 and +2 days of the GRB. The Si and O P Cygni lines of SN 2003dh seem comparable to those of SN 1997ef, which suggests that the ejected mass in SN 2003dh may match that in SN 1997ef. Polarization was marginally detected at optical wavelengths. This is consistent with measurements of the late afterglow, implying that it originated mostly in the interstellar medium of the host galaxy.
The Astrophysical Journal 12/2008; 593(1):L19. · 6.02 Impact Factor
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P. A. Mazzali,
K. S. Kawabata,
K Maeda,
R. J. Foley,
K Nomoto, J Deng,
T Suzuki,
M. Iye,
N. Kashikawa,
Y Ohyama,
A. V. Filippenko,
Y Qiu,
J Wei
[show abstract]
[hide abstract]
ABSTRACT: The nebular spectra of the broad-lined, SN 1998bw-like Type Ic SN 2002ap are studied by means of synthetic spectra. Two different modelling techniques are employed. In one technique, the SN ejecta are treated as a single zone, while in the other a density and abundance distribution in velocity is used from an explosion model. In both cases, heating caused by gamma-ray and positron deposition is computed (in the latter case using a Monte Carlo technique to describe the propagation of gamma-rays and positrons), as is cooling via forbidden-line emission. The results are compared, and although general agreement is found, the stratified models are shown to reproduce the observed line profiles much more accurately than the single-zone model. The explosion produced ~ 0.1 Msun of 56Ni. The distribution in velocity of the various elements is in agreement with that obtained from the early-time models, which indicated an ejected mass of ~ 2.5 Msun with a kinetic energy of 4 x 10^{51} erg. Nebular spectroscopy confirms that most of the ejected mass (~ 1.2 Msun) was oxygen. The presence of an oxygen-rich inner core, combined with that of 56Ni at high velocities as deduced from early-time models, suggests that the explosion was asymmetric, especially in the inner part. Comment: 24 pages, 6 figures, 2 Tables. Accepted by the Astrophysical Journal
08/2007;
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A Pastorello,
S J Smartt,
S Mattila,
J J Eldridge,
D Young,
K Itagaki,
H Yamaoka,
H Navasardyan,
S Valenti,
F Patat, [......],
V Lorenzi,
P A Mazzali,
X Meng,
S Nakano,
T B Nielsen,
J V Smoker,
V Stanishev,
M Turatto,
D Xu,
L Zampieri
[show abstract]
[hide abstract]
ABSTRACT: The death of massive stars produces a variety of supernovae, which are linked to the structure of the exploding stars. The detection of several precursor stars of type II supernovae has been reported (see, for example, ref. 3), but we do not yet have direct information on the progenitors of the hydrogen-deficient type Ib and Ic supernovae. Here we report that the peculiar type Ib supernova SN 2006jc is spatially coincident with a bright optical transient that occurred in 2004. Spectroscopic and photometric monitoring of the supernova leads us to suggest that the progenitor was a carbon-oxygen Wolf-Rayet star embedded within a helium-rich circumstellar medium. There are different possible explanations for this pre-explosion transient. It appears similar to the giant outbursts of luminous blue variable stars (LBVs) of 60-100 solar masses, but the progenitor of SN 2006jc was helium- and hydrogen-deficient (unlike LBVs). An LBV-like outburst of a Wolf-Rayet star could be invoked, but this would be the first observational evidence of such a phenomenon. Alternatively, a massive binary system composed of an LBV that erupted in 2004, and a Wolf-Rayet star exploding as SN 2006jc, could explain the observations.
Nature 07/2007; 447(7146):829-32. · 36.28 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: RESUMEN Las Supernovas de tipo Ic asociadas con Destellos de Rayos Gama muestran líneas anchas en absorción en sus etapas tempranas. Otras SNs Ic exhiben esta propiedad pero sin estar asociadas a un DRG. Con espectros sintéticos tanto en las primeras etapas como en las más avanzadas se pueden determinar las propiedades de estas SNs, que indican que las explosiones no ocurren en forma esférica, y dan así una conexión natural entre las Hipernovas y los Destellos de Rayos Gama. ABSTRACT The Type Ic Supernovae associated with Gamma Ray Bursts show very broad absorption lines in the early phase. Other SNe Ic share this property but are not apparently linked to a GRB. Synthetic spectra in both the early and the late phase can be used to constrain the properties of these SNe and bear indications that the explosions are aspherical, providing a natural link between Hypernovae and Gamma Ray Bursts.
01/2007; 27:251-257.
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E Pian,
P A Mazzali,
N Masetti,
P Ferrero,
S Klose,
E Palazzi,
E Ramirez-Ruiz,
S E Woosley,
C Kouveliotou, J Deng, [......],
F Frontera,
A S Fruchter,
J Greiner,
K Kawabata,
C Ledoux,
K Maeda,
P Møller,
L Nicastro,
E Rol,
R Starling
[show abstract]
[hide abstract]
ABSTRACT: Long-duration gamma-ray bursts (GRBs) are associated with type Ic supernovae that are more luminous than average and that eject material at very high velocities. Less-luminous supernovae were not hitherto known to be associated with GRBs, and therefore GRB-supernovae were thought to be rare events. Whether X-ray flashes--analogues of GRBs, but with lower luminosities and fewer gamma-rays--can also be associated with supernovae, and whether they are intrinsically 'weak' events or typical GRBs viewed off the axis of the burst, is unclear. Here we report the optical discovery and follow-up observations of the type Ic supernova SN 2006aj associated with X-ray flash XRF 060218. Supernova 2006aj is intrinsically less luminous than the GRB-supernovae, but more luminous than many supernovae not accompanied by a GRB. The ejecta velocities derived from our spectra are intermediate between these two groups, which is consistent with the weakness of both the GRB output and the supernova radio flux. Our data, combined with radio and X-ray observations, suggest that XRF 060218 is an intrinsically weak and soft event, rather than a classical GRB observed off-axis. This extends the GRB-supernova connection to X-ray flashes and fainter supernovae, implying a common origin. Events such as XRF 060218 are probably more numerous than GRB-supernovae.
Nature 09/2006; 442(7106):1011-3. · 36.28 Impact Factor
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S. Taubenberger,
A. Pastorello,
P. A. Mazzali,
S. Valenti,
G. Pignata,
D. N. Sauer,
A. Arbey,
O. Bärnbantner,
S. Benetti,
A. Della Valle, [......],
P. Meikle,
J. Mendez,
F. Patat,
E. Pian,
C. Ries,
P. Ruiz-Lapuente,
M. Salvo,
V. Stanishev,
M. Turatto,
W. Hillebrandt
[show abstract]
[hide abstract]
ABSTRACT: Optical and near-infrared observations of the Type Ic supernova (SN) 2004aw are presented, obtained from day -3 to day +413 with respect to the B-band maximum. The photometric evolution is characterised by a comparatively slow post-maximum decline of the light curves. The peaks in redder bands are significantly delayed relative to the bluer bands, the I-band maximum occurring 8.4 days later than that in B. With an absolute peak magnitude of -18.02 in the V band the SN can be considered fairly bright, but not exceptional. This also holds for the U through I bolometric light curve, where SN 2004aw has a position intermediate between SNe 2002ap and 1998bw. Spectroscopically SN 2004aw provides a link between a normal Type Ic supernova like SN 1994I and the group of broad-lined SNe Ic. The spectral evolution is rather slow, with a spectrum at day +64 being still predominantly photospheric. The shape of the nebular [O I] 6300,6364 line indicates a highly aspherical explosion. Helium cannot be unambiguously identified in the spectra, even in the near-infrared. Using an analytical description of the light curve peak we find that the total mass of the ejecta in SN 2004aw is 3.5-8.0 M_Sun, significantly larger than in SN 1994I, although not as large as in SN 1998bw. The same model suggests that about 0.3 M_Sun of {56}Ni has been synthesised in the explosion. No connection to a GRB can be firmly established.
08/2006;
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[show abstract]
[hide abstract]
ABSTRACT: The properties of the type Ic supernova SN 1994I are re-investigated. This object is often referred to as a "standard SN Ic" although it exhibited an extremely fast light curve and unusually blue early-time spectra. In addition, the observations were affected by significant dust extinction. A series of spectral models are computed based on the explosion model CO21 (Iwamoto et al. 1994) using a Monte Carlo transport spectral synthesis code. Overall the density structure and abundances of the explosion model are able to reproduce the photospheric spectra well. Reddening is estimated to be E(B-V)=0.30 mag, a lower value than previously proposed. A model of the nebular spectrum of SN 1994I points toward a slightly larger ejecta mass than that of CO21. The photospheric spectra show a large abundance of iron-group elements at early epochs, indicating that mixing within the ejecta must have been significant. We present an improved light curve model which also requires the presence of 56Ni in the outer layers of the ejecta.
05/2006;
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P. Ferrero,
D. A. Kann,
A. Zeh,
S. Klose,
E. Pian,
E. Palazzi,
N. Masetti,
D. H. Hartmann,
J. Sollerman, J Deng,
A. V. Filippenko,
J. Greiner,
M. A. Hughes,
P. Mazzali,
W Li,
E. Rol,
R. J. Smith,
N. R. Tanvir
[show abstract]
[hide abstract]
ABSTRACT: The supernova SN 2006aj associated with GRB 060218 is the second-closest GRB-SN observed to date (z=0.033). We present Very Large Telescope, Liverpool Telescope, and Katzman Automatic Imaging Telescope multi-color photometry of SN 2006aj. This supernova is found to be subluminous and rapidly evolving. Its early light curve includes an additional wavelength-dependent component, which can be interpreted as shock break-out. We compare the photometric evolution of multi-band light curves with the corresponding properties of the present sample of more than 10 GRB-SNe with precisely known redshifts. Using host-galaxy extinction measurements, we derive extinction-corrected GRB-SN luminosities and place SN 2006aj in the context of this GRB-selected supernova sample as well as in the context of local stripped-envelope supernovae. Comment: accepted for publication in A&A, updated references
05/2006;
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[show abstract]
[hide abstract]
ABSTRACT: The available observational data on the GRB-connected, energetic Type Ic
Supernovae (Hypernovae) are reviewed and analysed, with particular
emphasis on the indications that the explosions are aspherical,
providing a natural link between Hypernovae and Gamma Ray Bursts.
11/2005; 342:366.
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[show abstract]
[hide abstract]
ABSTRACT: We present BVRI photometry and optical spectroscopy of SN 2005bf near light maximum. The maximum phase is broad and occurred around 2005 May 7, about forty days after the shock breakout. SN 2005bf has a peak bolometric magnitude M_{bol}=-18.0\pm 0.2: while this is not particularly bright, it occurred at an epoch significantly later than other SNe Ibc, indicating that the SN possibly ejected ~0.31 M_{sun} of 56Ni, which is more than the typical amount. The spectra of SN 2005bf around maximum are very similar to those of the Type Ib SNe 1999ex and 1984L about 25-35 days after explosion, displaying prominent He I, Fe II, Ca II H & K and the near-IR triplet P Cygni lines. Except for the strongest lines, He I absorptions are blueshifted by <~6500 km/s, and Fe II by \~7500-8000 km/s. No other SNe Ib have been reported to have their Fe II absorptions blueshifted more than their He I absorptions. Relatively weak H-alpha and very weak H-beta may also exist, blueshifted by ~15,000 km/s. We suggest that SN 2005bf was the explosion of a massive He star, possibly with a trace of a hydrogen envelope. Comment: 13 pages, 4 figures. Accepted for publication in ApJ (Letters)
09/2005;
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[show abstract]
[hide abstract]
ABSTRACT: Recent studies of core-collapse supernovae have revealed the existence of two distinct classes of massive supernovae (SNe): 1) very energetic SNe (Hypernovae), whose kinetic energy (KE) exceeds $10^{52}$ erg, about 10 times the KE of normal core-collapse SNe, and 2) very faint and low energy SNe (E < 0.5 $\times$ $10^{51}$ erg; Faint supernovae). These two classes of supernovae are likely to be "black-hole-forming" supernovae with rotating or non-rotating black holes. We compare their nucleosynthesis yields with the abundances of extremely metal-poor (EMP) stars to identify the Pop III (or first) supernovae. We show that the EMP stars, especially the C-rich type, are likely to be enriched by black-hole-forming supernovae.
07/2005;
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P. A. Mazzali,
K. S. Kawabata,
K Maeda,
K Nomoto,
A. V. Filippenko,
E. Ramirez-Ruiz,
S. Benetti,
E. Pian, J Deng,
N Tominaga,
Y Ohyama,
M. Iye,
R. J. Foley,
T. Matheson,
L Wang,
A. Gal-Yam
[show abstract]
[hide abstract]
ABSTRACT: Type Ic supernovae, the explosions following the core collapse of massive stars that have previously lost their hydrogen and helium envelopes, are particularly interesting because of the link with long-duration gamma-ray bursts. Although indications exist that these explosions are aspherical, direct evidence has still been missing. Late-time observations of SN 2003jd, a luminous Type Ic supernova, provide such evidence. Recent Subaru and Keck spectra reveal double-peaked profiles in the nebular lines of neutral oxygen and magnesium. These profiles are different from those of known Type Ic supernovae, with or without a gamma-ray burst, and they can be understood if SN 2003jd was an aspherical, axisymmetric explosion viewed from near the equatorial plane. If SN 2003jd was associated with a gamma-ray burst, we missed the burst as it was pointing away from us. Comment: To be published in Science on 27 May 2005. 14 pages, 4 figures
05/2005;
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[show abstract]
[hide abstract]
ABSTRACT: Stars more massive than ∼ 20 − 25 M⨀ form a black hole at the end of their evolution. Stars with non-rotating black holes are likely to collapse “quietly” ejecting
a small amount of heavy elements (faint supernovae). In contrast, stars with rotating black holes are likely to give rise
to very energetic supernovae (hypernovae). We present distinct nucleosynthesis features of these two types of “black-hole-forming”
supernovae. Nucleosynthesis in hypernovae is characterized by larger abundance ratios (Zn,Co,V,Ti)/Fe and smaller (Mn,Cr)/Fe
than normal supernovae, which can explain the observed trend of these ratios in extremely metal-poor stars. Nucleosynthesis
in faint supernovae is characterized by a large amount of fall-back. We show that the abundance pattern of the recently discovered
most Fe-poor star, HE0107-5240, and other extremely metal-poor carbon-rich stars are in good accord with those of black-hole-forming
supernovae, but not pair-instability supernovae. This suggests that black-hole-forming supernovae made important contributions
to the early Galactic (and cosmic) chemical evolution. Finally we discuss the nature of first (Pop III) Stars.
12/2004: pages 287-296;
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[show abstract]
[hide abstract]
ABSTRACT: The two peculiar Type Ic supernovae (SNe) 1997ef and 1997dq are shown to have very similar photometric and spectral evolution in the epochs when both SNe are observed (i.e. beyond $\sim 80$ days after the explosion). The early light curves and spectra of SN 1997ef suggested that this was a ``hypernova,'' or ``SN 1998bw-like Type Ic supernova.'' The fact that the two SNe are very similar allows us to extend the time coverage of this type of event, since SN 1997dq, unlike SN 1997ef, was observed well into the nebular phase. In contrast to SN 1998bw, the spectra of these two SNe did not become fully nebular until almost one year after the explosion. During a long transition phase, lasting at least 6 months, the SNe developed nebular emission in lines of [\OI] and [\CaII], but at the same time they retained an underlying, photospheric-type spectrum, originating at very low velocities. Spectral synthesis techniques are used to model the spectrum of SN 1997dq, suggesting that it produced $\sim 0.16 \Msun$ of \Nifs, and that a significant fraction of this is located in a dense, low-velocity inner region. Comment: 19 pages, 6 figures. To appear in the Astrophysical Journal (October 20, 2004)
09/2004;
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[show abstract]
[hide abstract]
ABSTRACT: XRF 030723 is the first X-ray flash (XRF) to show in its optical light curve (LC) a bump that has been interpreted as the signature of a supernova (SN). After subtracting the afterglow component from the observed optical LC of the XRF counterpart, the properties of the putative SN are constrained by means of synthetic LCs of core-collapse SNe. For the redshift range $z \sim 0.3$ -- 1, all possible models require a rather small mass of synthesized \Nifs, i.e. $M$(\Nifs) $\sim$ 0.01 -- 0.3 $\Msun$. The models used to describe the energetic SNe Ic associated with gamma-ray bursts (SNe 1998bw and 2003dh) are too massive for the observed LC. If the relation between ejected \Nifs mass and total ejecta mass established from models of various Type Ic SNe also holds for the putative SN in XRF 030723, the ejecta mass is constrained to be $\sim$ 1 -- 3 $\Msun$ and the kinetic energy $\lsim 1\times 10^{52}$ erg. This corresponds to a progenitor with $15\Msun \lesssim M_{\rm MS}\lesssim 25\Msun$. The SN therefore appears to have properties intermediate between a normal SN Ic like SN 1994I and a more energetic object like SN 2002ap.
06/2004;
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[show abstract]
[hide abstract]
ABSTRACT: Optical spectroscopy of the Type Ia supernova SN 2002ic obtained on 2003 June 27.6 UT, i.e., about 222 rest-frame days after explosion, is presented. Strong H emission indicates an interaction between the expanding SN ejecta and an H-rich circumstellar medium (CSM). The spectrum of SN 2002ic resembles those of SNe 1997cy and 1999E. The three SNe also have similar luminosities, suggesting that they are the same phenomenon and that the CSM is also similar. We propose a new classification, Type IIa SNe, for these events. The observed line profiles and line ratios are measured and discussed within the ejecta-CSM interaction scenario. The emission in H Balmer, [O III], and He I lines, and in permitted Fe II blends, resembles the spectra of the Type IIn SN 1987F and of Seyfert 1 galaxies. A high-density, clumpy CSM is inferred. Strong, very broad [Ca II]/Ca II and [O I]/O I missions imply that not all the outer SN ejecta were decelerated in the interaction, suggesting that the CSM is aspherical. Comment: 13 pages including 4 figures, aastex preprint style. Minor changes. Accepted by ApJL
11/2003;
