SN 2002bo Research Articles

Probabilistic Reconstruction of Type Ia Supernova SN 2002bo

Abstract Manual fits to spectral times series of Type Ia supernovae have provided a method of reconstructing the explosion from a parametric model but due to lack of information about model uncertainties or parameter degeneracies direct comparison between theory and observation is difficult. In order to mitigate this important problem we present a new way to probabilistically reconstruct the outer ejecta of the normal Type Ia supernova SN 2002bo. A single epoch spectrum, taken 10 days before maximum light, is fit by a 13-parameter model describing the elemental composition of the ejecta and the explosion physics (density, temperature, velocity, and explosion epoch). Model evaluation is performed through the application of a novel rapid spectral synthesis technique in which the radiative transfer code, TARDIS, is accelerated by a machine-learning framework. Analysis of the posterior distribution reveals a complex and degenerate parameter space and allows direct comparison to various hydrodynamic models. Our analysis favors detonation over deflagration scenarios and we find that our technique offers a novel way to compare simulation to observation.

Supernova 2010ev: A reddened high velocity gradient type Ia supernova

Aims. We present and study the spectroscopic and photometric evolution of the type Ia supernova (SN Ia) 2010ev. Methods. We obtain and analyze multi-band optical light curves and optical-near-infrared spectroscopy at low and medium resolution spanning from -7 days to +300 days from the B-band maximum. Results. A photometric analysis shows that SN 2010ev is a SN Ia of normal brightness with a light curve shape of $\Delta m_{15}(B)=1.12 \pm 0.02$ and a stretch s = $0.94 \pm 0.01$ suffering significant reddening. From photometric and spectroscopic analysis, we deduce a color excess of $E(B - V) = 0.25 \pm 0.05$ and a reddening law of $R_v = 1.54 \pm 0.65$. Spectroscopically, SN 2010ev belongs to the broad-line SN Ia group, showing stronger than average Si II {\lambda}6355 absorption features. We also find that SN 2010ev is a high-velocity gradient SN, with a value of $164 \pm 7$ km s$^{-1}$ d$^{-1}$. The photometric and spectral comparison with other supernovae shows that SN 2010ev has similar colors and velocities to SN 2002bo and SN 2002dj. The analysis of the nebular spectra indicates that the [Fe II] {\lambda}7155 and [Ni II] {\lambda}7378 lines are redshifted, as expected for a high velocity gradient supernova. All these common intrinsic and extrinsic properties of the high velocity gradient (HVG) group are different from the low velocity gradient (LVG) normal SN Ia population and suggest significant variety in SN Ia explosions.

DETERMINING TYPE Ia SUPERNOVA HOST GALAXY EXTINCTION PROBABILITIES AND A STATISTICAL APPROACH TO ESTIMATING THE ABSORPTION-TO-REDDENING RATIO RV

ABSTRACT We investigate limits on the extinction values of Type Ia supernovae (SNe Ia) to statistically determine the most probable color excess, E(B – V), with galactocentric distance, and use these statistics to determine the absorption-to-reddening ratio, R V , for dust in the host galaxies. We determined pixel-based dust mass surface density maps for 59 galaxies from the Key Insight on Nearby Galaxies: a Far-infrared Survey with Herschel (KINGFISH). We use SN Ia spectral templates to develop a Monte Carlo simulation of color excess E(B – V) with R V = 3.1 and investigate the color excess probabilities E(B – V) with projected radial galaxy center distance. Additionally, we tested our model using observed spectra of SN 1989B, SN 2002bo, and SN 2006X, which occurred in three KINGFISH galaxies. Finally, we determined the most probable reddening for Sa–Sap, Sab–Sbp, Sbc–Scp, Scd–Sdm, S0, and irregular galaxy classes as a function of R/R 25. We find that the largest expected reddening probabilities are in Sab–Sb and Sbc–Sc galaxies, while S0 and irregular galaxies are very dust poor. We present a new approach for determining the absorption-to-reddening ratio R V using color excess probability functions and find values of R V = 2.71 ± 1.58 for 21 SNe Ia observed in Sab–Sbp galaxies, and R V = 1.70 ± 0.38, for 34 SNe Ia observed in Sbc–Scp galaxies.

A one-dimensional Chandrasekhar-mass delayed-detonation model for the broad-lined Type Ia supernova 2002bo

We present 1D non-local thermodynamic equilibrium (non-LTE) time-dependent radiative-transfer simulations of a Chandrasekhar-mass delayed-detonation model which synthesizes 0.51 Msun of 56Ni, and confront our results to the Type Ia supernova (SN Ia) 2002bo over the first 100 days of its evolution. Assuming only homologous expansion, this same model reproduces the bolometric and multi-band light curves, the secondary near-infrared (NIR) maxima, and the optical and NIR spectra. The chemical stratification of our model qualitatively agrees with previous inferences by Stehle et al., but reveals significant quantitative differences for both iron-group and intermediate-mass elements. We show that +/-0.1 Msun (i.e., +/-20 per cent) variations in 56Ni mass have a modest impact on the bolometric and colour evolution of our model. One notable exception is the U-band, where a larger abundance of iron-group elements results in less opaque ejecta through ionization effects, our model with more 56Ni displaying a higher near-UV flux level. In the NIR range, such variations in 56Ni mass affect the timing of the secondary maxima but not their magnitude, in agreement with observational results. Moreover, the variation in the I, J, and K_s magnitudes is less than 0.1 mag within ~10 days from bolometric maximum, confirming the potential of NIR photometry of SNe Ia for cosmology. Overall, the delayed-detonation mechanism in single Chandrasekhar-mass white dwarf progenitors seems well suited for SN 2002bo and similar SNe Ia displaying a broad Si II 6355 A line. Whatever multidimensional processes are at play during the explosion leading to these events, they must conspire to produce an ejecta comparable to our spherically-symmetric model.

Near-infrared light curves of type Ia supernovae

Aims. With our time-dependent model atmosphere code PHOENIX, our goal is to simulate light curves and spectra of hydrodynamical models of all types of supernovae. In this work, we simulate near-infrared light curves of SNe Ia and confirm the cause of the secondary maximum. Methods. We apply a simple energy solver to compute the evolution of an SN Ia envelope during the free expansion phase. Included in the solver are energy changes due to expansion, the energy deposition of {\gamma}-rays and interaction of radiation with the material. Results. We computed theoretical light curves of several SN Ia hydrodynamical models in the I, J, H, and K bands and compared them to the observed SN Ia light curves of SN 1999ee and SN 2002bo. By changing a line scattering parameter in time, we obtained quite reasonable fits to the observed near-infrared light curves. This is a strong hint that detailed NLTE effects in IR lines have to be modeled, which will be a future focus of our work. Conclusions. We found that IR line scattering is very important for the near-infrared SN Ia light curve modeling. In addition, the recombination of Fe III to Fe II and of Co III to Co II is responsible for the secondary maximum in the near-infrared bands. For future work the consideration of NLTE for all lines (including the IR subordinate lines) will be crucial.

Theoretical light curves of type Ia supernovae

Aims. We present the first theoretical SN Ia light curves calculated with the time-dependent version of the general purpose model atmosphere code PHOENIX. Our goal is to produce light curves and spectra of hydro models of all types of supernovae. Methods. We extend our model atmosphere code PHOENIX to calculate type Ia supernovae light curves. A simple solver was imple- mented which keeps track of energy conservation in the atmosphere during the free expansion phase. Results. The correct operation of the new additions to PHOENIX were verified in test calculations. Furthermore, we calculated theo- retical light curves and compared them to the observed SN Ia light curves of SN 1999ee and SN 2002bo. We obtained LTE as well as NLTE model light curves. Conclusions. We have verified the correct operation of our extension into the time domain. We have calculated the first SN Ia model light curves using PHOENIX in both LTE and NLTE. For future work the infrared model light curves need to be further investigated.

Optical and infrared observations of SN 2002dj: some possible common properties of fast-expanding Type Ia supernovae

As part of the European Supernova Collaboration, we obtained extensive photometry and spectroscopy of the Type Ia supernova (SN Ia) SN 2002dj covering epochs from 11 d before to nearly two years after maximum. Detailed optical and near-infrared observations show that this object belongs to the class of the high-velocity gradient events as indicated by Si, S and Ca lines. The light curve shape and velocity evolution of SN 2002dj appear to be nearly identical to SN 2002bo. The only significant difference is observed in the optical to near-infrared colours and a reduced spectral emission beyond 6500 Å. For high-velocity gradient SNe Ia, we tentatively identify a faster rise to maximum, a more pronounced inflection in the V and R light curves after maximum and a brighter, slower declining late-time B light curve as common photometric properties of this class of objects. They also seem to be characterized by a different colour and colour evolution with respect to ‘normal’ SNe Ia. The usual light curve shape parameters do not distinguish these events. Stronger, more blueshifted absorption features of intermediate-mass elements and lower temperatures are the most prominent spectroscopic features of SNe Ia displaying high-velocity gradients. It appears that these events burn more intermediate-mass elements in the outer layers. Possible connections to the metallicity of the progenitor star are explored.

Interpretation of observed type Ia supernova spectra with radiative transfer models

The different nucleosynthetic yields in type Ia supernovae lead to variation in the observed properties of those objects. Complementary to extensive numerical simulations of the explosion physics the detailed analysis of well observed objects can provide constraints on the explosion mechanism. Using radiative transfer models for a time series of observed spectra the depth-dependent composition of the ejecta can be traced. Here we present this method as applied to the type Ia supernova SN 2004eo, which was observed by the European Supernova Collaboration. We compare the results to the previously analyzed SN 2002bo.

Abundance Tomography of Type Ia Supernovae

Many uncertainties about the physics of Type Ia Supernovae have been revealed in the recent past, and numerous pieces are puzzled together to achieve a complete description of the phenomenon of thermonuclear explosions in the sky. However, very important parts are still missing. In particular, the concept lacks a proper connection between the various evolutionary steps, namely the progenitor scenario, explosion theory, nucleosynthesis from the burning, and the observations. Early time spectra of Type Ia Supernovae naturally contain information about all of these processes and are at the centre of the entire scenario. Appropriate models of that phase can provide the missing link and improve our understanding of this field enormously. The goal of this thesis is to advance new methods to calculate synthetic spectra in order to extract the information contained in the observations more efficiently. Based on a well established radiation transfer code, a new technique called Abundance Tomography is developed to derive the abundance distribution of Type Ia Supernovae ejecta. While previous approaches were limited to the determination of the abundances of specific species in restricted regions of the supernova envelope, here a complete stratified distribution of all major elements is obtained. This method is applied to the very well observed normal SN 2002bo. Combining the early spectra with those of the nebular phase leads to a coverage of the entire ejecta from the centre out to the highest velocities. The abundances derived are used to compute a synthetic bolometric light curve to test the radial distribution of Fe group and intermediate-mass elements. The sampling procedure of the incident radiation field at the lower boundary is modified to obtain a better description of the real situation in Type Ia Supernovae. This improves the overall flux distribution significantly, especially in the red part of the spectrum, where almost no real line opacity is found. Synthetic spectra with this new procedure reproduce the observations much more accurately, as is shown by models of SN 2002er. Hydrogen lines have never been detected convincingly in Type Ia Supernovae spectra. However, using spectra that were observed more than 10 days before maximum light, it is shown that small amounts of hydrogen in the outer parts of the ejecta can explain high velocity line absorptions, seen rather frequently in various objects, e.g. SN 2002dj, SN 2003du, and SN 1999ee. The hydrogen is not claimed to be primordial to the white dwarf but it is rather the effect of the supernova ejecta interacting with circumstellar material, namely the white dwarf's accretion disk build up prior to the explosion. Finally, UV spectra of Type Ia Supernovae are discussed. The ability of the Monte Carlo technique to deal naturally with this wavelength region is proven. Applications are presented by modelling spectra of SN 2001ep and SN 2001eh obtained with the Hubble Space Telescope. The results are discussed in the broader context of Type Ia Supernovae physics: What causes the diversity in the nearby sample? What are the progenitors and how does the explosion work? What is the influence on cosmological models? A detailed knowledge of the abundances, their distribution in the Supernova ejecta, and their ultimate causes delivers the key to these fundamental issues.

Abundance stratification in Type Ia supernovae - I. The case of SN 2002bo

The abundance stratification in the ejecta of the normal Type Ia supernova 2002bo is derived by fitting a series of spectra obtained at close time intervals. A Monte Carlo code, modified to include abundance stratification, is used to compute synthetic spectra at 13 epochs in the photospheric phase, starting 13 d before B maximum. A description of the abundance distribution above 7600 km s −1 is thus obtained. Abundances in deeper layers, down to zero velocity, are derived from models of two nebular-phase spectra. Elements synthesized in different stages of burning are significantly, but not completely, mixed in the ejecta. A total 56 Ni mass of 0.52 M� is derived. Evidence for intermediate-mass elements at high velocities (18 000 km s −1 )i s found, most clearly in Si II 6355 A, in Ca II H&K ,and in the Ca II infrared triplet. Carbon lines are not seen at any velocity, with possible implications for the progenitor/explosion scenario. A synthetic bolometric light curve computed using the inferred abundance distribution is in very good agreement with the observed one, providing an independent check. In particular, the fast rise of the light curve is reproduced very well. This is due to outward mixing of 56 Ni, which is clearly well determined by the spectroscopic modelling. Ke yw ords: supernovae: general ‐ supernovae: individual: SN 2002bo.

Synthetic Spectra of the Type Ia SN 2002bo

SummarySN 2002bo, a type Ia supernova in NGC 3190, is the first object of the European Supernova Collaboration (ESC). It was discovered on 09 March 2002 and is one of the earliest observed SNe. An almost complete set of spectra and photometry is available from 13 days before maximum B light until a few days after. An analysis using synthetic spectra is presented, focusing on the controversial issue of the reddening of SN 2002bo.

Optical and Infrared Photometry of the Type Ia Supernovae 1991T, 1991bg, 1999ek, 2001bt, 2001cn, 2001cz, and 2002bo

We present optical and/or infrared photometry of the Type Ia supernovae SN 1991T, SN 1991bg, SN 1999ek, SN 2001bt, SN 2001cn, SN 2001cz, and SN 2002bo. All but one of these supernovae have decline rate parameters, Δm15(B), close to the median value of 1.1 for the whole class of Type Ia supernovae. The addition of these supernovae to the relationship between the near-infrared absolute magnitudes and Δm15(B) strengthens the previous relationships we have found in that the maximum light absolute magnitudes are essentially independent of the decline rate parameter. (SN 1991bg, the prototype of the subclass of fast-declining Type Ia supernovae, is a special case.) The dispersion in the Hubble diagram in JHK is only ~0.15 mag. The near-infrared properties of Type Ia supernovae continue to be excellent measures of the luminosity distances to the supernova host galaxies because of the need for only small corrections from the epoch of observation to maximum light, low dispersion in absolute magnitudes at maximum light, and the minimal reddening effects in the near-infrared.

Supernova 2002bo: inadequacy of the single parameter description

We present optical/near-infrared photometry and spectra of the type Ia SN 2002bo spanning epochs from -13 days before maximum B-band light to +102 days after. The pre-maximum optical coverage is particularly complete. In some respects, SN 2002bo behaves as a typical Branch type Ia supernova (SN Ia) at optical and IR wavelengths. We find a B-band risetime of 17.9+-0.5 days, a Dm_{15}(B) of 1.13+-0.05, and a M_B=-19.41+-0.42. However, comparison with other type Ia supernovae having similar Delta m_{15}(B) values indicates that in other respects SN 2002bo is unusual. While the optical spectra of SN 2002bo are very similar to those of SN 1984A, lower velocities and a generally more structured appearance are found in SNe 1990N, 1994D and 1998bu. For supernovae having Dm_(15)(B) > 1.2, we confirm the variation of R(SiII) (Nugent et al. 1995) with Dm_(15)(B). However, for supernovae such as SN2002bo, with lower values of Dm_(15)(B) the relation breaks down. Moreover, the evolution of R(SiII) for SN 2002bo is strikingly different from that shown by other type Ia supernovae. The velocities of SN 2002bo and 1984A derived from SII 5640A, SiII 6355A and CaII H&K lines are either much higher and/or evolve differently from those seen in other normal SNe Ia events. We suggest that the unusually low temperature, the presence of high-velocity intermediate-mass elements and the low abundance of carbon at early times indicates that burning to Si penetrated to much higher layers than in more normal type Ia supernovae. This may be indicative of a delayed-detonation explosion.

Photometry of SN 2002bo with template image subtraction

VRI photometry of the type Ia supernova 2002bo is presented. This SN exploded in a dusty region of the host galaxy NGC 3190, thus, subtraction of a template frame was necessary to obtain reliable photometry. We used a template frame of NGC 3190 taken during the course of our galaxy imaging project, fortunately, just a few days before SN 2002bo was discovered. The aim of this project is to collect template frames of nearby galaxies that are potential hosts of bright SNe. Subtraction of pre-SN images helped us to exclude the background light contamination of the host galaxy. The maximum occurred at JD 2452346, with maximal V brightness of 13.58. MLCS analysis led to T0(B)=JD 2452346.1 pm 0.8 (fiducial B-maximum), E(B-V)=0.24 pm 0.02, mu0=32.46 pm 0.06, Delta=-0.14 pm 0.04. E(B-V)=0.24(2) indicates a significant extinction in the host galaxy as the galactic reddening is negligible toward NGC 3190. The accepted value of Delta indicates that SN 2002bo was a slightly overluminous SN by about 0.14 relative to fiducial SN Type Ia. The distance turned out to be 31.0 pm 3 Mpc. In addition, the heavily obscured SN 2002cv was also detected on the I frame taken on JD 2452434 (June 8, 2002), and a variable star is found in the field, very close to the host galaxy.