A Spectroscopic Analysis of the Energetic Type Ic Hypernova SN 1997ef

By P. Mazzali, K. Iwamoto, Ken’ichi Nomoto. 2000

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The properties of the bright and energetic Type Ic SN 1997ef are investigated using a Monte Carlo spectrum synthesis code. Analysis of the earliest spectra is used to determine the time of outburst. The changing features of the spectrum and the light curve are used to probe the ejecta and to determine their composition, verifying the results of explosion calculations. Since synthetic spectra computed using our best explosion model, CO100, are only moderately good reproductions of the observations, the inverse approach is adopted, and a density structure is derived by demanding that it gives the best possible fit to the observed spectrum at every epoch analyzed. It is found that the density structure of model CO100 is adequate at intermediate velocities (5000-25,000 km s-1), but that a slower density decline (ρ ∝ r-4) is required to obtain the extensive line blending at high velocities (25,000-50,000 km s-1) that is the characterizing feature of this and other energetic Type Ic Supernovae. Also, the inner "hole" in the density predicted by the model is found not to be compatible with the observed evolution of the spectrum, which reaches very low photospheric velocities at epochs of about 2 months. The "best-fit" density distribution results in somewhat different parameters for the SN, namely an ejecta mass of 9.6 M☉ (vs. 7.6 M☉ in CO100) and an explosion kinetic energy of 1.75 × 1052 ergs (vs. 8 × 1051 ergs in CO100). This revised value of the kinetic energy brings SN 1997ef closer to the value for the "prototypical" Type Ic hypernova SN 1998bw. The abundance distribution of model CO100 is found to hold well. The modified density structure is used to compute a synthetic light curve, which is found to agree very well with the observed bolometric light curve around maximum. The amount of radioactive 56Ni produced by the SN is confirmed at 0.13 M☉. In the context of an axisymmetric explosion, a somewhat smaller kinetic energy than that of SN 1998bw may have resulted from the nonalignment of the symmetry axis of the SN and the line of sight. This might also explain the lack of evidence for a gamma-ray burst correlated with SN 1997ef.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/7585cc186b051139476acaf505f5a2c9625a7eb7

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Citations in the corpus

The Type Ic Hypernova SN 2002ap (2002, methodology): “It will therefore be interesting to see whether the photosphere persists to very low velocities, as it did in SN 1997ef, in apparent contradiction with onedimensional explosion models (Mazzali et al. 2000).”
The Type Ic Hypernova SN 2003dh/GRB 030329 (2003, methodology): “The model used for SN 1997ef (model CO100E18; Mazzali et al. 2000; Table 1), on the other hand, has much too little mass at high velocities, and it does not yield a broad-lined spectrum similar to the observed one.”
Supernova Nucleosynthesis in Population III 13-50 M☉ Stars and Abundance Patterns of Extremely Metal-poor Stars (2007, background): “…core-collapse SNewere thought to explode with E51 1, as SN1987A (Blinnikov et al. 2000), SN 1993J (Nomoto et al. 1993), and SN 1994I (Nomoto et al. 1994), before the discoveries of HNe SN 1997ef ( Iwamoto et al. 2000; Mazzali et al. 2000) and SN 1998bw (Patat et al. 2001; Nakamura et al. 2001a).”
Light Curve and Spectral Models for the Hypernova SN 1998bw Associated with GRB 980425 (2000, background): “Such a flat density distribution at high velocities is also required to fit the spectrum of another hypernova, SN 1997ef (Mazzali et al. 2000a).”
Bolometric light curves and explosion parameters of 38 stripped-envelope core-collapse supernovae (2014, methodology): “…et al. 2011), 0.06 (Maeda et al. 2003; Valenti et al. 2008), 0.07 (Cano 2013; Taddia et al. 2015) and 0.08 cm2 g−1 (Pignata et al. 2011), largely driven by the values of κopt near peak from results of spectroscopic modelling (Chugai 2000; Mazzali et al. 2000, 2013; Mazzali et al., in preparation).”
SN 2003du: 480 days in the life of a normal type Ia supernova (2007, methodology): “In Mazzali et al. (2000) the Monte Carlo code was compared with the results from the radiation hydrodynamics code of Iwamoto et al. (2000), finding very good agreement.”
Nebular emission-line profiles of Type Ib/c supernovae - Probing the ejecta asphericity (2009, background): “Note that the presence of dense cores has been suggested for several SNe to explain their line profiles and late-time light-curve slopes (Iwamoto et al. 2000; Mazzali et al. 2000; Maeda et al. 2003; Mazzali et al. 2007a,b).”
Circumstellar Emission from Type Ib and Ic Supernovae (2006, background): “However, Mazzali et al. (2000) find that the spectroscopic modeling of the broadline Type Ic SN 1997ef is improved by having a relatively flat density profile ( / r 4) over the velocity range 25,000Y 50,000 km s 1.”
A Two-Component Model for the Light Curves of Hypernovae (2003, methodology): “Although, in reality, opt changes with time and position in the ejecta as it depends on composition and temperature, Mazzali et al. (2000) found that for a reasonable choice of a constant opt, the code can reproduce the earlyphase light curve of SN 1997ef.”
SN 2004aw: confirming diversity of Type Ic supernovae (2006, background): “…extensive data sets were obtained, but their publication took some time and coincided with the new boom in SN Ic research, which set in with the discovery of SN 1997ef (Garnavich et al. 1997a,b,c; Iwamoto et al. 2000; Mazzali et al. 2000) and SN 1998bw (Galama et al. 1998; Patat et al. 2001).”
The Rates of Hypernovae and Gamma-Ray Bursts: Implications for Their Progenitors (2004, background): “…from the very bright and energetic SNe 1998bw (Iwamoto et al. 1998) and 2003dh (Mazzali et al. 2003), the moderately bright but very energetic SNe 1997ef (Mazzali et al. 2000) and 1997dq (Mazzali et al., in preparation), and the normally bright but over-energetic SN 2002ap (Mazzali et al. 2002).”