29 research outputs found
iPTF13beo: The Double-Peaked Light Curve of a Type Ibn Supernova Discovered Shortly after Explosion
We present optical photometric and spectroscopic observations of the Type Ibn
(SN 2006jc-like) supernova iPTF13beo. Detected by the intermediate Palomar
Transient Factory ~3 hours after the estimated first light, iPTF13beo is the
youngest and the most distant (~430 Mpc) Type Ibn event ever observed. The
iPTF13beo light curve is consistent with light curves of other Type Ibn SNe and
with light curves of fast Type Ic events, but with a slightly faster rise-time
of two days. In addition, the iPTF13beo R-band light curve exhibits a
double-peak structure separated by ~9 days, not observed before in any Type Ibn
SN. A low-resolution spectrum taken during the iPTF13beo rising stage is
featureless, while a late-time spectrum obtained during the declining stage
exhibits narrow and intermediate-width He I and Si II features with FWHM ~
2000-5000 km/s and is remarkably similar to the prototypical SN Ibn 2006jc
spectrum. We suggest that our observations support a model of a massive star
exploding in a dense He-rich circumstellar medium (CSM). A shock breakout in a
CSM model requires an eruption releasing a total mass of ~0.1 Msun over a time
scale of couple of weeks prior to the SN explosion.Comment: 8 pages, 5 figures, submitted to MNRA
Exploring the spectral diversity of low-redshift Type Ia supernovae using the Palomar Transient Factory
We present an investigation of the optical spectra of 264 low-redshift (z <
0.2) Type Ia supernovae (SNe Ia) discovered by the Palomar Transient Factory,
an untargeted transient survey. We focus on velocity and pseudo-equivalent
width measurements of the Si II 4130, 5972, and 6355 A lines, as well those of
the Ca II near-infrared (NIR) triplet, up to +5 days relative to the SN B-band
maximum light. We find that a high-velocity component of the Ca II NIR triplet
is needed to explain the spectrum in ~95 per cent of SNe Ia observed before -5
days, decreasing to ~80 per cent at maximum. The average velocity of the Ca II
high-velocity component is ~8500 km/s higher than the photospheric component.
We confirm previous results that SNe Ia around maximum light with a larger
contribution from the high-velocity component relative to the photospheric
component in their Ca II NIR feature have, on average, broader light curves and
lower Ca II NIR photospheric velocities. We find that these relations are
driven by both a stronger high-velocity component and a weaker contribution
from the photospheric Ca II NIR component in broader light curve SNe Ia. We
identify the presence of C II in very-early-time SN Ia spectra (before -10
days), finding that >40 per cent of SNe Ia observed at these phases show signs
of unburnt material in their spectra, and that C II features are more likely to
be found in SNe Ia having narrower light curves.Comment: 18 page, 10 figures, accepted for publication in MNRA
Absence of Fast-moving Iron in an Intermediate Type Ia Supernova between Normal and Super-Chandrasekhar
In this paper, we report observations of a peculiar SN Ia iPTF13asv (a.k.a., SN2013cv) from the onset of the explosion to months after its peak. The early-phase spectra of iPTF13asv show an absence of iron absorption, indicating that synthesized iron elements are confined to low-velocity regions of the ejecta, which, in turn, implies a stratified ejecta structure along the line of sight. Our analysis of iPTF13asv's light curves and spectra shows that it is an intermediate case between normal and super-Chandrasekhar events. On the one hand, its light curve shape (B-band Îm_(15) = 1.03 ± 0.01) and overall spectral features resemble those of normal SNe Ia. On the other hand, its large peak optical and UV luminosity (M_B = -19.84 mag, M_(uvm2) = -15.5 mag) and its low but almost constant Si II velocities of about 10,000 km s^(â1) are similar to those in super-Chandrasekhar events, and its persistent carbon signatures in the spectra are weaker than those seen commonly in super-Chandrasekhar events. We estimate a ^(56)Ni mass of 0.81 ± ^(+0.10)_(-0.18) Mâ and a total ejecta mass of 1.59^(+0.45)_(-0.12)Mâ. The large ejecta mass of iPTF13asv and its stratified ejecta structure together seemingly favor a double-degenerate origin
Absence of fast-moving iron in an intermediate type ia supernova between normal and super-chandrasekhar
The American Astronomical Society. All rights reserved.In this paper, we report observations of a peculiar SN Ia iPTF13asv (a.k.A., SN2013cv) from the onset of the explosion to months after its peak. The early-phase spectra of iPTF13asv show an absence of iron absorption, indicating that synthesized iron elements are confined to low-velocity regions of the ejecta, which, in turn, implies a stratified ejecta structure along the line of sight. Our analysis of iPTF13asv's light curves and spectra shows that it is an intermediate case between normal and super-Chandrasekhar events. On the one hand, its light curve shape (B-band ) and overall spectral features resemble those of normal SNe Ia. On the other hand, its large peak optical and UV luminosity (, ) and its low but almost constant Si ii velocities of about 10,000 km s-1 are similar to those in super-Chandrasekhar events, and its persistent carbon signatures in the spectra are weaker than those seen commonly in super-Chandrasekhar events. We estimate a 56Ni mass of and a total ejecta mass of . The large ejecta mass of iPTF13asv and its stratified ejecta structure together seemingly favor a double-degenerate origin. © 2016
Ătude de la variabilitĂ© des Supernovae de type Ia observĂ©es par la collaboration Nearby Supernova Factory
One of the current limitations of type Ia supernovae used as distance indicators is themixing of their different sources of variabilitiy during the empirical standardization of their distance modulus. Using the nearby SNe Ia spectral sample observed by the Nearby Supernovae Collaboration with the instrument SNIFS (Supernovae Intergral Field Sperctrograph), this thesis mainly focuses on this problematic using spectral indicators measurements. The first part of the thesis presents the scientific context as well as the sample used in the analysis. The second part focus on the spectral indicators measurement and their properties in the presence of interstellar dust extinction. The third part is a study of spectral indicators correlations and their use as standardization parameters. In the last part, we use these spectral indicators to construct a mean extinction law for type Ia supernovaeVers la fin des annĂ©es 1990, lâutilisation des supernovae de type Ia (SNe Ia) comme indicateurs de distance a permis de mettre en Ă©vidence lâexpansion accĂ©lĂ©rĂ©e de lâunivers. Depuis lors, des campagnes dâobservations de grandes envergures ont permis dâaugmenter de façon significative le nombre de SNe Ia observĂ©es, mais les incertitudes systĂ©matiques liĂ©es Ă la qualitĂ© des Ă©chantillons de SNe Ia proches restent un facteur limitant sur la prĂ©cision des mesures actuelles. Câest dans le but de rĂ©duire ces incertitudes que le projet the Nearby Supernova Factory (SNfactory), Ă lâaide dâun instrument spectro-photomĂ©trique dĂ©diĂ© Ă lâobservation des SNe Ia (the Supernova Integral Field Spectrograph), a collectĂ© depuis 2004 plus de 3000 spectres de prĂšs de 200 SNe Ia proches. Une des limitations actuelles de leur utilisation, outre les aspects liĂ©s aux problĂšmes dâinter-calibration entre les diffĂ©rentes expĂ©riences, est celle du mĂ©lange des diffĂ©rentes composantes de leurs variabilitĂ©s lors de la standardisation empirique de leur module de distance. Une meilleure sĂ©paration de ces composantes, ainsi que la dĂ©couverte de nouveaux indicateurs de distance, font partie des amĂ©liorations que peut apporter un Ă©chantillon spectral de SNe Ia proches tel que celui de la collaboration SNfactory. Cette thĂšse de doctorat, effectuĂ©e Ă lâInstitut de Physique NuclĂ©aire de Lyon et au Lawrence Berkeley National Laboratory, sâinscrit directement dans cette problĂ©matique, en se concentrant sur la mesure dâindicateurs spectraux sur lâĂ©chantillon spectral de la collaboration Snfactory. Le plan de cette thĂšse est le suivant : La premiĂšre partie prĂ©sente le contexte scientifique ainsi que lâĂ©chantillon de SNe Ia de la collaboration SNfactory utilisĂ© dans les analyses. La deuxiĂšme partie se concentre sur la mĂ©thode de mesure dâindicateurs spectraux appliquĂ©e Ă lâĂ©chantillon spectrale prĂ©sentĂ©, ainsi que sur une Ă©tude de leur sensibilitĂ© Ă lâextinction par le milieu interstellaire. La troisiĂšme partie est une Ă©tude des corrĂ©lations des indicateurs spectraux et de leur utilisation pour la standardisation des Sne Ia. Dans la derniĂšre partie, une utilisation de ces indicateurs spectraux pour la dĂ©termination dâune loi dâextinction moyenne est prĂ©sentĂ©
Study of the type Ia Supernovae variability observed by the Nearby Supernova Factory collaboration
Vers la fin des annĂ©es 1990, lâutilisation des supernovae de type Ia (SNe Ia) comme indicateurs de distance a permis de mettre en Ă©vidence lâexpansion accĂ©lĂ©rĂ©e de lâunivers. Depuis lors, des campagnes dâobservations de grandes envergures ont permis dâaugmenter de façon significative le nombre de SNe Ia observĂ©es, mais les incertitudes systĂ©matiques liĂ©es Ă la qualitĂ© des Ă©chantillons de SNe Ia proches restent un facteur limitant sur la prĂ©cision des mesures actuelles. Câest dans le but de rĂ©duire ces incertitudes que le projet the Nearby Supernova Factory (SNfactory), Ă lâaide dâun instrument spectro-photomĂ©trique dĂ©diĂ© Ă lâobservation des SNe Ia (the Supernova Integral Field Spectrograph), a collectĂ© depuis 2004 plus de 3000 spectres de prĂšs de 200 SNe Ia proches. Une des limitations actuelles de leur utilisation, outre les aspects liĂ©s aux problĂšmes dâinter-calibration entre les diffĂ©rentes expĂ©riences, est celle du mĂ©lange des diffĂ©rentes composantes de leurs variabilitĂ©s lors de la standardisation empirique de leur module de distance. Une meilleure sĂ©paration de ces composantes, ainsi que la dĂ©couverte de nouveaux indicateurs de distance, font partie des amĂ©liorations que peut apporter un Ă©chantillon spectral de SNe Ia proches tel que celui de la collaboration SNfactory. Cette thĂšse de doctorat, effectuĂ©e Ă lâInstitut de Physique NuclĂ©aire de Lyon et au Lawrence Berkeley National Laboratory, sâinscrit directement dans cette problĂ©matique, en se concentrant sur la mesure dâindicateurs spectraux sur lâĂ©chantillon spectral de la collaboration Snfactory. Le plan de cette thĂšse est le suivant : La premiĂšre partie prĂ©sente le contexte scientifique ainsi que lâĂ©chantillon de SNe Ia de la collaboration SNfactory utilisĂ© dans les analyses. La deuxiĂšme partie se concentre sur la mĂ©thode de mesure dâindicateurs spectraux appliquĂ©e Ă lâĂ©chantillon spectrale prĂ©sentĂ©, ainsi que sur une Ă©tude de leur sensibilitĂ© Ă lâextinction par le milieu interstellaire. La troisiĂšme partie est une Ă©tude des corrĂ©lations des indicateurs spectraux et de leur utilisation pour la standardisation des Sne Ia. Dans la derniĂšre partie, une utilisation de ces indicateurs spectraux pour la dĂ©termination dâune loi dâextinction moyenne est prĂ©sentĂ©eOne of the current limitations of type Ia supernovae used as distance indicators is themixing of their different sources of variabilitiy during the empirical standardization of their distance modulus. Using the nearby SNe Ia spectral sample observed by the Nearby Supernovae Collaboration with the instrument SNIFS (Supernovae Intergral Field Sperctrograph), this thesis mainly focuses on this problematic using spectral indicators measurements. The first part of the thesis presents the scientific context as well as the sample used in the analysis. The second part focus on the spectral indicators measurement and their properties in the presence of interstellar dust extinction. The third part is a study of spectral indicators correlations and their use as standardization parameters. In the last part, we use these spectral indicators to construct a mean extinction law for type Ia supernova
Mechanical properties of refractories: Multiâscale composite approach from grains to material level
International audienceRefractory materials exhibit a heterogeneous microstructure consisting in coarse aggregates surrounded by fine grains that form an aggregate/matrix composite. This heterogeneous microstructure often leads to a complex mechanical behaviour during loading. This paper is devoted to the study of thermomechanical properties of several industrial and model refractory materials in relation with the evolution of their microstructure during thermal treatments. The aim is, in particular, to highlight the role of thermal expansion mismatches existing between the different phases which can induce damage at local scale. The resulting network of microcracks is well known to decrease elastic properties. Moreover, this network of microcracks can also strongly affect the thermal expansion at low temperature and the stress-strain behaviour in tension. Indeed, the occurrence of a large quantity of small precracks during the cooling stage after sintering, which enhances the development of a fracture process zone while loading, allows the decrease of the brittleness of the material which becomes in this case flexible. The large increase in strain to rupture, which results from this flexibility, is thus of a great interest for the enhancement of thermal shock resistance
Influence of sintering parameters of aluminum titanate (TiAl2O5) on microstructure and on thermomechanical properties
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Preparation and characterization of thermomechanical properties of aluminum titanate (TiAl2O5)
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Investigation of the damage behaviour of refractory model materials at high temperature by combined pulse echography and acoustic emission techniques
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