The Carbon-rich Type Ic SN 2007gr: The Photospheric Phase

Valenti, S.; Elias‐Rosa, N.; Taubenberger, S.; Stanishev, V.; Agnoletto, I.; Sauer, Daniel; Cappellaro, E.; Pastorello, A.; Benetti, S.; Riffeser, A.; Hopp, U.; Navasardyan, H.; Tsvetkov, D. Yu.; Lorenzi, V.; Patat, F.; Turatto, M.; Barbon, R.; Ciroi, S.; Mille, F. Di; Frandsen, S.; Fynbo, J. P. U.; Laursen, Peter; Mazzali, P. A.

doi:10.1086/527672

Cited by 111 publications

(138 citation statements)

References 33 publications

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“…3). Comparison SNe Ic presented in this paper have been chosen to span this wide range of properties from the prototypical SN 1994I (Sauer et al 2006;Richmond et al 1996) to the very energetic SN 1998bw (Galama et al 1998;Patat et al 2001) and including intermediate SNe 2007gr (Valenti et al 2008b;Hunter et al 2009), 1997ef (Mazzali et al 2000Iwamoto et al 1998;Nakano et al 1997), 2002ap (Mazzali et al 2002Gal-Yam et al 2002;Foley et al 2003;Yoshii et al 2003;Hendry et al 2005), 2003jd (Valenti et al 2008a) and 2004aw (Taubenberger et al 2006). In both Figs.…”

Section: Light Curvesmentioning

confidence: 99%

Two type Ic supernovae in low-metallicity, dwarf galaxies: diversity of explosions

Young¹,

Smartt²,

Valenti³

et al. 2010

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Aims. The aim of this paper is to discuss the nature of two type Ic supernovae SN 2007bg and SN 2007bi and their host galaxies. Both supernovae were discovered in wide-field, non-targeted surveys and are found to be associated with sub-luminous blue dwarf galaxies identified in SDSS images. Methods. We present BVRI photometry and optical spectroscopy of SN 2007bg and SN 2007bi and their host galaxies. Their lightcurves and spectra are compared to those of other type Ic SNe and analysis of these data provides estimates of the energetics, total ejected masses and synthesised mass of 56 Ni. Detection of the host galaxy emission lines allows for metallicity measurements. Results. Neither SNe 2007bg nor 2007bi were found in association with an observed GRB, but from estimates of the metallicities of their host-galaxies they are found to inhabit similar low-metallicity environments as GRB associated supernovae. The radio-bright SN 2007bg is hosted by an extremely sub-luminous galaxy of magnitude M B = −12.4 ± 0.6 mag and an estimated oxygen abundance of 12 + log(O/H) = 8.18 ± 0.17 (on the Pettini & Pagel 2004 scale). The early lightcurve evolution of SN 2007bg matches the fastpace decline of SN 1994I giving it one of the fastest post-maximum decline rates of all broad-lined type Ic supernovae known to date and, when combined with its high expansion velocities, a high kinetic energy to ejected mass ratio (E K /M ej ∼ 2.7). We also show that SN 2007bi is possibly the most luminous type Ic known, reaching a peak magnitude of M R ∼ −21.3 mag and displays a remarkably slow decline, following the radioactive decay rate of 56 Co to 56 Fe throughout the course of its observed lifetime. SN 2007bi also displays an extreme longevity in its spectral evolution and is still not fully nebular at approximately one year post-maximum brightness. From a simple model of the bolometric light curve of SN 2007bi we estimate a total ejected 56 Ni mass of M Ni = 3.5−4.5 M , the largest 56 Ni mass measured in the ejecta of a supernova to date. There are two models that could explain the high luminosity and large ejected 56 Ni mass. One is a pair-instability supernova (PISN) which has been predicted to occur for massive stars at low metallicities. We measure the host galaxy metallicity of SN 2007bi to be 12 + log(O/H) = 8.15 ± 0.15 (on the McGaugh 1991 scale) which is somewhat high to be consistent with the PISN model. An alternative is the core-collapse of a C+O star of 20−40 M which is the core of a star of originally 50−100 M .

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Section: Light Curvesmentioning

confidence: 99%

Two type Ic supernovae in low-metallicity, dwarf galaxies: diversity of explosions

Young¹,

Smartt²,

Valenti³

et al. 2010

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“…Chornock et al (2007) classified SN 2007gr to be of type Ib/c from a spectrum taken soon after explosion. The classification was later refined to type Ic as the presence of He could not be confirmed in subsequent spectra (Valenti et al 2008a).…”

Section: Sn 2007grmentioning

confidence: 99%

“…We adopt a galactic extinction of E(B − V) = 0.062 (Schlegel et al 1998), and a host galaxy extinction of E(B − V) = 0.03 which was estimated using the equivalent widths of Na I D absorption lines in a medium-resolution spectrum (Valenti et al 2008a). We assume a total uncertainty of 20% for our estimate of the total extinction E(B − V) tot = 0.092 ± 0.018 mag.…”

Section: Sn 2007grmentioning

confidence: 99%

“…For comparison, we have also included the bolometric light curves of the SNe Ic sample. Following Valenti et al (2008a), we applied a toy-model to the bolometric light curve of SN 2007gr in order to constrain the physical parameters of the explosion (see Table 2). These include the ejected mass (M ej ), the nickel mass (M56 Ni ), and the kinetic energy (E kin ).…”

Section: The Bolometric (Uvoir) Light Curves and Physical Parametersmentioning

confidence: 99%

“…Consequently, SN 2007gr was classified as a type Ic. Valenti et al (2008a) studied the feature at 6450 Å, which may be misidentified as 6678 Å He I in early-time spectra, and suggest that a more plausible identification is C II 6580 Å at a velocity of ∼11 000 km s −1 . Indeed this feature disappears around maximum together with another feature at 7000 Å attributable to C II 7235 Å, thereby providing support for the Ic classification.…”

Section: Optical Spectramentioning

confidence: 99%

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Extensive optical and near-infrared observations of the nearby, narrow-lined type Ic SN 2007gr: days 5 to 415

Hunter

Valenti

Kotak

et al. 2009

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We present photometric and spectroscopic observations at optical and near-infrared wavelengths of the nearby type Ic supernova 2007gr. These represent the most extensive data-set to date of any supernova of this sub-type, with frequent coverage from shortly after discovery to more than one year post-explosion. We deduce a rise time to B-band maximum of 11.5 ± 2.7 d. We find a peak B-band magnitude of M B = −16.8, and light curves which are remarkably similar to the so-called "hypernova" SN 2002ap. In contrast, the spectra of SNe 2007gr and 2002ap show marked differences, not least in their respective expansion velocities. We attribute these differences primarily to the density profiles of their progenitor stars at the time of explosion i.e. a more compact star for SN 2007gr compared to SN 2002ap. From the quasi-bolometric light curve of SN 2007gr, we estimate that 0.076 ± 0.010 M of 56 Ni was produced in the explosion. Our near-infrared (IR) spectra clearly show the onset and disappearance of the first overtone of carbon monoxide (CO) between ∼70 to 175 d relative to B-band maximum. The detection of the CO molecule implies that ionised He was not microscopically mixed within the carbon/oxygen layers. From the optical spectra, near-IR light curves, and colour evolution, we find no evidence for dust condensation in the ejecta out to about +400 d. Given the combination of unprecedented temporal coverage, and high signal-to-noise data, we suggest that SN 2007gr could be used as a template object for supernovae of this sub-class.

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Observational and Physical Classification of Supernovae

Gal‐Yam¹

2016

Handbook of Supernovae

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This chapter describes the current classification scheme of supernovae (SNe). This scheme has evolved over many decades and now includes numerous SN Types and sub-types. Many of these are universally recognized, while there are controversies regarding the definitions, membership and even the names of some sub-classes; we will try to review here the commonly-used nomenclature, noting the main variants when possible. SN Types are defined according to observational properties; mostly visible-light spectra near maximum light, as well as according to their photometric properties. However, a long-term goal of SN classification is to associate observationally-defined classes with specific physical explosive phenomena. We show here that this aspiration is now finally coming to fruition, and we establish the SN classification scheme upon direct observational evidence connecting SN groups with specific progenitor stars. Observationally, the broad class of Type II SNe contains objects showing strong spectroscopic signatures of hydrogen, while objects lacking such signatures are of Type I, which is further divided to numerous subclasses. Recently a class of super-luminous SNe (SLSNe, typically 10 times more luminous than standard events) has been identified, and it is discussed. We end this chapter by briefly describing a proposed alternative classification scheme that is inspired by the stellar classification system. This system presents our emerging physical understanding of SN explosions, while clearly separating robust observational properties from physical inferences that can be debated. This new system is quantitative, and naturally deals with events distributed along a continuum, rather than being strictly divided into discrete classes. Thus, it may be more suitable to the coming era where SN numbers will quickly expand from a few thousands to millions of events.Comment: Extended final draft of a chapter in the "SN Handbook". Comments most welcom

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The Carbon-rich Type Ic SN 2007gr: The Photospheric Phase

Cited by 111 publications

References 33 publications

Two type Ic supernovae in low-metallicity, dwarf galaxies: diversity of explosions

Two type Ic supernovae in low-metallicity, dwarf galaxies: diversity of explosions

Extensive optical and near-infrared observations of the nearby, narrow-lined type Ic SN 2007gr: days 5 to 415

Observational and Physical Classification of Supernovae

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