316 research outputs found
Abundance stratification in Type Ia supernovae - V. SN 1986G bridging the gap between normal and subluminous SNe Ia
A detailed spectroscopic analysis of SN 1986G has been performed. SN 1986G
`bridges the gap' between normal and sub luminous type Ia supernova (SNe Ia).
The abundance tomography technique is used to determine the abundance
distribution of the elements in the ejecta. SN 1986G was found to be a low
energy Chandrasekhar mass explosion. Its kinetic energy was 70% of the standard
W7 model (0.9x10erg). Oxygen dominates the ejecta from the outermost
layers down to 9000kms , intermediate mass elements (IME) dominate
from 9000kms to 3500kms with Ni and Fe dominating
the inner layers 3500kms. The final masses of the main elements
in the ejecta were found to be, O=0.33M, IME=0.69M, stable NSE=0.21M,
Ni=0.14M. An upper limit of the carbon mass is set at C=0.02M. The
spectra of SN1986G consist of almost exclusively singly ionised species.
SN1986G can be thought of as a low luminosity extension of the main population
of SN Ia, with a large deflagration phase that produced more IMEs than a
standard SN Ia.Comment: Accepted for publication in MNRAS, update
Breaking the color-reddening degeneracy in type Ia supernovae
A new method to study the intrinsic color and luminosity of type Ia
supernovae (SNe Ia) is presented. A metric space built using principal
component analysis (PCA) on spectral series SNe Ia between -12.5 and +17.5 days
from B maximum is used as a set of predictors. This metric space is built to be
insensitive to reddening. Hence, it does not predict the part of color excess
due to dust-extinction. At the same time, the rich variability of SN Ia spectra
is a good predictor of a large fraction of the intrinsic color variability.
Such metric space is a good predictor of the epoch when the maximum in the B-V
color curve is reached. Multivariate Partial Least Square (PLS) regression
predicts the intrinsic B band light-curve and the intrinsic B-V color curve up
to a month after maximum. This allows to study the relation between the light
curves of SNe Ia and their spectra. The total-to-selective extinction ratio RV
in the host-galaxy of SNe Ia is found, on average, to be consistent with
typical Milky-Way values. This analysis shows the importance of collecting
spectra to study SNe Ia, even with large sample publicly available. Future
automated surveys as LSST will provide a large number of light curves. The
analysis shows that observing accompaning spectra for a significative number of
SNe will be important even in the case of "normal" SNe Ia.Comment: 11 pages, 11 figure
Abundance stratification in Type Ia supernovae - V. SN 1986G bridging the gap between normal and subluminous SNe Ia
A detailed spectroscopic analysis of SN 1986G has been performed. SN 1986G `bridges the gap' between normal and sub luminous type Ia supernova (SNe Ia). The abundance tomography technique is used to determine the abundance distribution of the elements in the ejecta. SN 1986G was found to be a low energy Chandrasekhar mass explosion. Its kinetic energy was 70% of the standard W7 model (0.9x10erg). Oxygen dominates the ejecta from the outermost layers down to 9000kms , intermediate mass elements (IME) dominate from 9000kms to 3500kms with Ni and Fe dominating the inner layers 3500kms. The final masses of the main elements in the ejecta were found to be, O=0.33M, IME=0.69M, stable NSE=0.21M, Ni=0.14M. An upper limit of the carbon mass is set at C=0.02M. The spectra of SN1986G consist of almost exclusively singly ionised species. SN1986G can be thought of as a low luminosity extension of the main population of SN Ia, with a large deflagration phase that produced more IMEs than a standard SN Ia
Extracting high-level information from gamma-ray burst supernova spectra
Radiation transport codes are often used in astrophysics to construct spectral models. In this work, we demonstrate how producing thesemodels for a time series of data can provide unique information about supernovae (SNe). Unlike previous work, we specifically concentrate on the method for obtaining the best synthetic spectral fits, and the errors associated with the preferred model parameters.We demonstrate how varying the ejecta mass, bolometric luminosity (Lbol) and photospheric velocity (vph), affects the outcome of the synthetic spectra. As an example we analyse the photospheric phase spectra of the GRB-SN 2016jca. It is found that for most epochs (where the afterglow subtraction is small) the error on Lbol and vph was∼5 per cent. The uncertainty on ejectamass and Ekin was found to be∼20 per cent, although this can be expected to dramatically decrease if models of nebular phase data can be simultaneously produced. We also demonstrate how varying the elemental abundance in the ejecta can produce better synthetic spectral fits. In the case of SN2016jca it is found that a decreasing 56Ni abundance as a function of decreasing velocity produces the best-fitting models. This could be the case if the 56Ni was synthesized at the side of the GRB jet, or dredged up from the centre of the explosion. The work presented here can be used as a guideline for future studies on SNe which use the same or similar radiation transfer code
Luminosity distributions of Type Ia Supernovae
We have assembled a dataset of 165 low redshift, 0.06, publicly available type Ia supernovae (SNe Ia). We produce maximum light magnitude ( and ) distributions of SNe Ia to explore the diversity of parameter space that they can fill. Before correction for host galaxy extinction we find that the mean and of SNe Ia are mag and mag respectively. Host galaxy extinction is corrected using a new method based on the SN spectrum. After correction, the mean values of and of SNe Ia are and mag respectively. After correction for host galaxy extinction, `normal' SNeIa (mag) fill a larger parameter space in the Width-Luminosity Relation (WLR) than previously suggested, and there is evidence for luminous SNe Ia with large . We find a bimodal distribution in , with a pronounced lack of transitional events at =1.6 mag. We confirm that faster, low-luminosity SNe tend to come from passive galaxies. Dividing the sample by host galaxy type, SNe Ia from star-forming (S-F) galaxies have a mean mag, while SNe Ia from passive galaxies have a mean mag. Even excluding fast declining SNe, `normal' ( mag) SNe Ia from S-F and passive galaxies are distinct. In the -band, there is a difference of 0.40.13 mag between the median () values of the `normal' SN Ia population from passive and S-F galaxies. This is consistent with (10)% of `normal' SNe Ia from S-F galaxies coming from an old stellar population
Breaking the color-reddening degeneracy in type Ia supernovae
A new method to study the intrinsic color and luminosity of type Ia supernovae (SNe Ia) is presented. A metric space built using principal component analysis (PCA) on spectral series SNe Ia between -12.5 and +17.5 days from B maximum is used as a set of predictors. This metric space is built to be insensitive to reddening. Hence, it does not predict the part of color excess due to dust-extinction. At the same time, the rich variability of SN Ia spectra is a good predictor of a large fraction of the intrinsic color variability. Such metric space is a good predictor of the epoch when the maximum in the B-V color curve is reached. Multivariate Partial Least Square (PLS) regression predicts the intrinsic B band light-curve and the intrinsic B-V color curve up to a month after maximum. This allows to study the relation between the light curves of SNe Ia and their spectra. The total-to-selective extinction ratio RV in the host-galaxy of SNe Ia is found, on average, to be consistent with typical Milky-Way values. This analysis shows the importance of collecting spectra to study SNe Ia, even with large sample publicly available. Future automated surveys as LSST will provide a large number of light curves. The analysis shows that observing accompaning spectra for a significative number of SNe will be important even in the case of "normal" SNe Ia
The nebular spectra of the transitional Type Ia Supernovae 2007on and 2011iv: Broad, multiple components indicate aspherical explosion cores
The nebular-epoch spectrum of the rapidly declining, 'transitional' Type Ia supernova (SN) 2007on showed double emission peaks, which have been interpreted as indicating that the SN was the result of the direct collision of two white dwarfs. The spectrum can be reproduced using two distinct emission components, one redshifted and one blueshifted. These components are similar in mass but have slightly different degrees of ionization. They recede from one another at a line-of-sight speed larger than the sum of the combined expansion velocities of their emitting cores, thereby acting as two independent nebulae. While this configuration appears to be consistent with the scenario of two white dwarfs colliding, it may also indicate an off-centre delayed detonation explosion of a near-Chandrasekhar-mass white dwarf. In either case, broad emission line widths and a rapidly evolving light curve can be expected for the bolometric luminosity of the SN. This is the case for both SNe 2007on and 2011iv, also a transitional SN Ia that exploded in the same elliptical galaxy, NGC1404. Although SN 2011iv does not show double-peaked emission line profiles, the width of its emission lines is such that a two-component model yields somewhat better results than a single-component model. Most of the mass ejected is in one component, however, which suggests that SN 2011iv was the result of the off-centre ignition of a Chandrasekhar-mass white dwarf. © 2017 The Authors
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