ABSTRACT Hubble Space Telescope observations of the site of the supernova (SN) 2008ax obtained in... more ABSTRACT Hubble Space Telescope observations of the site of the supernova (SN) 2008ax obtained in 2011 and 2013 reveal that the possible progenitor object detected in pre-explosion images was in fact multiple. Four point sources are resolved in the new, higher-resolution images. We identify one of the sources with the fading SN. The other three objects are consistent with single supergiant stars. We conclude that their light contaminated the previously identified progenitor candidate. After subtraction of these stars, the progenitor appears to be significantly fainter and bluer than previously measured. Post-explosion photometry at the SN location indicates that the progenitor object has disappeared. If single, the progenitor is compatible with a supergiant star of B to mid-A spectral type, while a Wolf-Rayet (WR) star would be too luminous in the ultraviolet to account for the observations. Moreover, our hydrodynamical modelling shows the pre-explosion mass was $4-5$ $M_\odot$ and the radius was $30-50$ $R_\odot$, which is incompatible with a WR progenitor. We present a possible interacting binary progenitor computed with our evolutionary models that reproduces all the observational evidence. A companion star as luminous as an O9-B0 main-sequence star may have remained after the explosion.
Aims. We present and analyse late-time observations of the type-Ib supernova with possible pre-su... more Aims. We present and analyse late-time observations of the type-Ib supernova with possible pre-supernova progenitor detection, iPTF13bvn, taken at ∼300 days after the explosion, and discuss these in the context of constraints on the supernova's progenitor. Previous studies have proposed two possible natures for the progenitor of the supernova, i.e. a massive Wolf-Rayet star or a lowermass star in close binary system. Methods. Our observations show that the supernova has entered the nebular phase, with the spectrum dominated by Mg I]λλ4571, [O I]λλ6300, 6364, and [Ca II]λλ7291, 7324 emission lines. We measured the emission line fluxes to estimate the core oxygen mass and compare the [O I]/[Ca II] line ratio with other supernovae.
Proceedings of the International Astronomical Union, 2013
ABSTRACT We review emission processes within the supernova (SN) ejecta. Examples of the applicati... more ABSTRACT We review emission processes within the supernova (SN) ejecta. Examples of the application of the theory to observational data are presented. The emission processes and thermal condition within the SN ejecta change as a function of time, and multi-epoch observations are important to obtain comprehensive views. Through the analyses, we can constrain the progenitor radius, compositions as a function of depth, ejecta properties, explosion asymmetry and so on. Multi-frequency follow-up is also important, including radio synchrotron emissions and the inverse Compton effect, γ-ray emissions from radioactive decay of newly synthesized materials. The optical data are essential to make the best use of the multi-frequency data.
Proceedings of the International Astronomical Union, 2011
ABSTRACT A set of hydrodynamical models based on stellar evolutionary progenitors is used to stud... more ABSTRACT A set of hydrodynamical models based on stellar evolutionary progenitors is used to study the nature of SN 2011dh. Our modeling suggests that a large progenitor star - with R ~ 200 R ⊙- is needed to reproduce the early light curve (LC) of SN 2011dh. This is consistent with the suggestion that the progenitor is a yellow super-giant star detected at the location of the SN in deep pre-explosion images. From the main peak of the bolometric light curve (LC) and expansion velocities we constrain the mass of the ejecta to be ~2 M ⊙, the explosion energy to be E = 8 × 1050 erg, and the 56Ni mass to be 0.063 M ⊙. The progenitor star is composed of a helium core of ~4 M ⊙ and a thin hydrogen envelope, and it had a main-sequence mass of ~13 M ⊙. Our models rule out progenitors with helium-core masses larger than 8 M ⊙, which correspond to M ZAMS >~ 25 M ⊙. This suggests that a single evolutionary scenario for SN 2011dh is highly unlikely.
Proceedings of the International Astronomical Union, 2013
ABSTRACT We present a study of the early UV/Optical emission of the stripped-envelope supernovae ... more ABSTRACT We present a study of the early UV/Optical emission of the stripped-envelope supernovae based on a one-dimensional, Lagrangian model that solves the hydrodynamics and radiation transport in an expanding ejecta. The models are compared with observations to constrain the physical properties of the progenitor star, such as radius and mixing of radioactive nickel synthesized during the explosion. In particular, we present models for the early emission of the type IIb SN 2011dh and the Type Ib SN 2008D.
We present Hubble Space Telescope (HST) observations of the field of the Type IIb supernova (SN) ... more We present Hubble Space Telescope (HST) observations of the field of the Type IIb supernova (SN) 2011dh in M51 performed at ≈1161 rest-frame days after explosion using the Wide Field Camera 3 and near-UV filters F225W and F336W. A star-like object is detected in both bands and the photometry indicates it has negative (F225W − F336W) color. The observed object is compatible with the companion of the now-vanished yellow supergiant progenitor predicted in interacting binary models. We consider it unlikely that the SN is undergoing strong interaction and thus estimate that it makes a small contribution to the observed flux. The possibilities of having detected an unresolved light echo or an unrelated object are briefly discussed and judged unlikely. Adopting a possible range of extinction by dust, we constrain parameters of the proposed binary system. In particular, the efficiency of mass accretion onto the binary companion must be below 50%, if no significant extinction is produced by newly formed dust. Further multiband observations are required in order to confirm the identification of the object as the companion star. If confirmed, the companion star would already be dominant in the UV-optical regime, so it would readily provide a unique opportunity to perform a detailed study of its properties.
The recent detection in archival HST images of an object at the the location of supernova (SN) iP... more The recent detection in archival HST images of an object at the the location of supernova (SN) iPTF 13bvn may represent the first direct evidence of the progenitor of a Type Ib SN. The object's photometry was found to be compatible with a Wolf-Rayet pre-SN star mass of ≈ 11 M ⊙ . However, based on hydrodynamical models we show that the progenitor had a pre-SN mass of ≈ 3.5 M ⊙ and that it could not be larger than ≈ 8 M ⊙ . We propose an interacting binary system as the SN progenitor and perform evolutionary calculations that are able to self-consistently explain the light-curve shape, the absence of hydrogen, and the pre-SN photometry. We further discuss the range of allowed binary systems and predict that the remaining companion is a luminous O-type star of significantly lower flux in the optical than the pre-SN object. A future detection of such star may be possible and would provide the first robust progenitor identification for a Type-Ib SN.
Modeling of Type II‐P Supernova Light Curves. [AIP Conference Proceedings 937, 433 (2007)]. Melin... more Modeling of Type II‐P Supernova Light Curves. [AIP Conference Proceedings 937, 433 (2007)]. Melina C. Bersten, Omar Benvenuto, Mario Hamuy. Abstract. We present progress in light curve models of type II‐P supernovae (SNe ...
We present extensive optical and near-infrared photometric and spectroscopic observations of the ... more We present extensive optical and near-infrared photometric and spectroscopic observations of the stripped-envelope (SE) supernova SN 2010as. Spectroscopic peculiarities, such as initially weak helium features and low expansion velocities with a nearly flat evolution, place this object in the small family of events previously identified as transitional Type Ib/c supernovae (SNe). There is ubiquitous evidence of hydrogen, albeit weak, in this family of SNe, indicating that they are in fact a peculiar kind of Type IIb SNe that we name "flat-velocity Type IIb". The flat velocity evolution-which occurs at different levels between 6000 and 8000 km s −1 for different SNe-suggests the presence of a dense shell in the ejecta. Despite the spectroscopic similarities, these objects show surprisingly diverse luminosities. We discuss the possible physical or geometrical unification picture for such diversity. Using archival HST images we associate SN 2010as with a massive cluster and derive a progenitor age of ≈6 Myr, assuming a single star-formation burst, which is compatible with a Wolf-Rayet progenitor. Our hydrodynamical modelling, on the contrary, indicates the pre-explosion mass was relatively low, of ≈4 M ⊙ . The seeming contradiction between an young age and low pre-SN mass may be solved by a massive interacting binary progenitor.
ABSTRACT We perform binary stellar evolutionary calculations following the simultaneous evolution... more ABSTRACT We perform binary stellar evolutionary calculations following the simultaneous evolution of both stars in the system to study a potential progenitor system for the Type IIb supernova 2011dh. Pre-explosion photometry as well as light-curve modeling have provided constraints on the physical properties of the progenitor system. Here we present a close binary system that is compatible with such constraints. The system is formed by stars of solar composition with 16 Msun + 10 Msun on a circular orbit with an initial period of 125 days. The primary star ends its evolution as a yellow supergiant with a mass of ~4 Msun, a final hydrogen content of ~3-5E-03 Msun and with an effective temperature and luminosity in agreement with the HST pre-explosion observations of SN 2011dh. These results are nearly insensitive to the adopted accretion efficiency factor beta. At the time of explosion, the companion star has an effective temperature of 22 to 40 thousand Kelvin, depending on the value of beta, and lies near the zero age main sequence. Considering the uncertainties in the HST pre-SN photometry the secondary star is only marginally detectable in the bluest observed band. Close binary systems, as opposed to single stars, provide a natural frame to explain the properties of SN 2011dh.
A set of hydrodynamical models based on stellar evolutionary progenitors is used to study the nat... more A set of hydrodynamical models based on stellar evolutionary progenitors is used to study the nature of SN 2011dh. Our modeling suggests that a large progenitor star-with R ∼ 200 R -is needed to reproduce the early light curve (LC) of SN 2011dh. This is consistent with the suggestion that the yellow super-giant star detected at the location of the supernova (SN) in deep pre-explosion images is the progenitor star. From the main peak of the bolometric LC and expansion velocities, we constrain the mass of the ejecta to be ≈2 M , the explosion energy to be E = (6-10) × 10 50 erg, and the 56 Ni mass to be approximately 0.06 M . The progenitor star was composed of a helium core of 3-4 M and a thin hydrogen-rich envelope of ≈0.1M with a main-sequence mass estimated to be in the range of 12-15 M . Our models rule out progenitors with helium-core masses larger than 8 M , which correspond to M ZAMS 25M . This suggests that a single star evolutionary scenario for SN 2011dh is unlikely.
We present bolometric light curves of Type II-plateau supernovae (SNe II-P) obtained using a newl... more We present bolometric light curves of Type II-plateau supernovae (SNe II-P) obtained using a newly developed, one-dimensional Lagrangian hydrodynamic code with flux-limited radiation diffusion. Using our code we calculate the bolometric light curve and photospheric velocities of SN 1999em obtaining a remarkably good agreement with observations despite the simplifications used in our calculation. The physical parameters used in our calculation are E = 1.25 foe, M = 19 M ⊙ , R = 800 R ⊙ and M Ni = 0.056 M ⊙ . We find that an extensive mixing of 56 Ni is needed in order to reproduce a plateau as flat as that shown by the observations. We also study the possibility to fit the observations with lower values of the initial mass consistently with upper limits that have been inferred from pre-supernova imaging of SN 1999em in connection with stellar evolution models. We cannot find a set of physical parameters that reproduce well the observations for models with pre-supernova mass of ≤ 12 M ⊙ , although models with 14 M ⊙ cannot be fully discarded.
In this paper we study the "standardized candle method" using a sample of 37 nearby (redshift z <... more In this paper we study the "standardized candle method" using a sample of 37 nearby (redshift z < 0.06) Type II plateau supernovae having BV RI photometry and optical spectroscopy. An analytic procedure is implemented to fit light curves, color curves, and velocity curves. We find that the V − I color toward the end of the plateau can be used to estimate the host-galaxy reddening with a precision of σ(A V ) = 0.2 mag. The correlation between plateau luminosity and expansion velocity previously reported in the literature is recovered. Using this relation and assuming a standard reddening law (R V = 3.1), we obtain Hubble diagrams in the BV I bands with dispersions of ∼ 0.4 mag. Allowing R V to vary and minimizing the spread in the Hubble diagrams, we obtain a dispersion range of 0.25-0.30 mag, which implies that these objects can deliver relative distances with precisions of 12-14%. The resulting best-fit value of R V is 1.4 ± 0.1.
We propose an alternative explanation for the post-breakout emission of SN 2008D associated with ... more We propose an alternative explanation for the post-breakout emission of SN 2008D associated with the X-ray transient 080109. Observations of this object show a very small contrast of 0.35 dex between the light-curve minimum occurring soon after the breakout, and the main luminosity peak that is due to radioactive heating of the ejecta. Hydrodynamical models show that the cooling of a shocked Wolf-Rayet star leads to a much greater difference ( 0.9 dex). Our proposed scenario is that of a jet produced during the explosion which deposits 56 Ni-rich material in the outer layers of the ejecta. The presence of high-velocity radioactive material allows us to reproduce the complete luminosity evolution of the object. Without outer 56 Ni it could be possible to reproduce the early emission purely from cooling of the shocked envelope by assuming a larger progenitor than a Wolf-Rayet star, but that would require an initial density structure significantly different from what is predicted by stellar evolution models. Analytic models of the cooling phase have been proposed reproduce the early emission of SN 2008D with an extended progenitor. However, we found that the models are valid only until 1.5 days after the explosion where only two data of SN 2008D are available. We also discuss the possibility of the interaction of the ejecta with a binary companion, based on published analytic expressions. However, the binary separation required to fit the early emission should be 3 R ⊙ , which is too small for a system containing two massive stars.
Recently, Chornock and co-workers announced the Pan-STARRS discovery of a transient source reachi... more Recently, Chornock and co-workers announced the Pan-STARRS discovery of a transient source reaching an apparent peak luminosity of ∼4 × 10 44 erg s −1 . We show that the spectra of this transient source are well fit by normal Type Ia supernova (SNIa) templates. The multi-band colors and lightcurve shapes are also consistent with normal SNeIa at the spectroscopically determined redshift of z = 1.3883; however, the observed flux is a constant factor of ∼30 times too bright in each band over time as compared to the templates. At minimum, this shows that the peak luminosities inferred from the light-curve widths of some SNeIa will deviate significantly from the established, empirical relation used by cosmologists. We argue on physical grounds that the observed fluxes do not reflect an intrinsically luminous SNIa, but rather PS1-10afx is a normal SNIa whose flux has been magnified by an external source. The only known astrophysical source capable of such magnification is a gravitational lens. Given the lack of obvious lens candidates, such as galaxy clusters, in the vicinity, we further argue that the lens is a supermassive black hole or a comparatively low-mass dark matter halo. In this case, the lens continues to magnify the underlying host galaxy light. If confirmed, this discovery could impact a broad range of topics including cosmology, gamma-ray bursts, and dark matter halos.
Presentamos los progresos en el modelado de curvas de luz de supernovas de tipo II plateau (SNe I... more Presentamos los progresos en el modelado de curvas de luz de supernovas de tipo II plateau (SNe II-P) obtenidos a partir de un código hidrodinámico unidimensional que recientemente hemos desarrollado. Usando modelos iniciales simples (polítropas) reprodujimos el comportamiento global de las curvas de luz observadas y analizamos la sensibilidad de la curva de luz a la variación de los parámetros libres.
ABSTRACT Hubble Space Telescope observations of the site of the supernova (SN) 2008ax obtained in... more ABSTRACT Hubble Space Telescope observations of the site of the supernova (SN) 2008ax obtained in 2011 and 2013 reveal that the possible progenitor object detected in pre-explosion images was in fact multiple. Four point sources are resolved in the new, higher-resolution images. We identify one of the sources with the fading SN. The other three objects are consistent with single supergiant stars. We conclude that their light contaminated the previously identified progenitor candidate. After subtraction of these stars, the progenitor appears to be significantly fainter and bluer than previously measured. Post-explosion photometry at the SN location indicates that the progenitor object has disappeared. If single, the progenitor is compatible with a supergiant star of B to mid-A spectral type, while a Wolf-Rayet (WR) star would be too luminous in the ultraviolet to account for the observations. Moreover, our hydrodynamical modelling shows the pre-explosion mass was $4-5$ $M_\odot$ and the radius was $30-50$ $R_\odot$, which is incompatible with a WR progenitor. We present a possible interacting binary progenitor computed with our evolutionary models that reproduces all the observational evidence. A companion star as luminous as an O9-B0 main-sequence star may have remained after the explosion.
Aims. We present and analyse late-time observations of the type-Ib supernova with possible pre-su... more Aims. We present and analyse late-time observations of the type-Ib supernova with possible pre-supernova progenitor detection, iPTF13bvn, taken at ∼300 days after the explosion, and discuss these in the context of constraints on the supernova's progenitor. Previous studies have proposed two possible natures for the progenitor of the supernova, i.e. a massive Wolf-Rayet star or a lowermass star in close binary system. Methods. Our observations show that the supernova has entered the nebular phase, with the spectrum dominated by Mg I]λλ4571, [O I]λλ6300, 6364, and [Ca II]λλ7291, 7324 emission lines. We measured the emission line fluxes to estimate the core oxygen mass and compare the [O I]/[Ca II] line ratio with other supernovae.
Proceedings of the International Astronomical Union, 2013
ABSTRACT We review emission processes within the supernova (SN) ejecta. Examples of the applicati... more ABSTRACT We review emission processes within the supernova (SN) ejecta. Examples of the application of the theory to observational data are presented. The emission processes and thermal condition within the SN ejecta change as a function of time, and multi-epoch observations are important to obtain comprehensive views. Through the analyses, we can constrain the progenitor radius, compositions as a function of depth, ejecta properties, explosion asymmetry and so on. Multi-frequency follow-up is also important, including radio synchrotron emissions and the inverse Compton effect, γ-ray emissions from radioactive decay of newly synthesized materials. The optical data are essential to make the best use of the multi-frequency data.
Proceedings of the International Astronomical Union, 2011
ABSTRACT A set of hydrodynamical models based on stellar evolutionary progenitors is used to stud... more ABSTRACT A set of hydrodynamical models based on stellar evolutionary progenitors is used to study the nature of SN 2011dh. Our modeling suggests that a large progenitor star - with R ~ 200 R ⊙- is needed to reproduce the early light curve (LC) of SN 2011dh. This is consistent with the suggestion that the progenitor is a yellow super-giant star detected at the location of the SN in deep pre-explosion images. From the main peak of the bolometric light curve (LC) and expansion velocities we constrain the mass of the ejecta to be ~2 M ⊙, the explosion energy to be E = 8 × 1050 erg, and the 56Ni mass to be 0.063 M ⊙. The progenitor star is composed of a helium core of ~4 M ⊙ and a thin hydrogen envelope, and it had a main-sequence mass of ~13 M ⊙. Our models rule out progenitors with helium-core masses larger than 8 M ⊙, which correspond to M ZAMS &gt;~ 25 M ⊙. This suggests that a single evolutionary scenario for SN 2011dh is highly unlikely.
Proceedings of the International Astronomical Union, 2013
ABSTRACT We present a study of the early UV/Optical emission of the stripped-envelope supernovae ... more ABSTRACT We present a study of the early UV/Optical emission of the stripped-envelope supernovae based on a one-dimensional, Lagrangian model that solves the hydrodynamics and radiation transport in an expanding ejecta. The models are compared with observations to constrain the physical properties of the progenitor star, such as radius and mixing of radioactive nickel synthesized during the explosion. In particular, we present models for the early emission of the type IIb SN 2011dh and the Type Ib SN 2008D.
We present Hubble Space Telescope (HST) observations of the field of the Type IIb supernova (SN) ... more We present Hubble Space Telescope (HST) observations of the field of the Type IIb supernova (SN) 2011dh in M51 performed at ≈1161 rest-frame days after explosion using the Wide Field Camera 3 and near-UV filters F225W and F336W. A star-like object is detected in both bands and the photometry indicates it has negative (F225W − F336W) color. The observed object is compatible with the companion of the now-vanished yellow supergiant progenitor predicted in interacting binary models. We consider it unlikely that the SN is undergoing strong interaction and thus estimate that it makes a small contribution to the observed flux. The possibilities of having detected an unresolved light echo or an unrelated object are briefly discussed and judged unlikely. Adopting a possible range of extinction by dust, we constrain parameters of the proposed binary system. In particular, the efficiency of mass accretion onto the binary companion must be below 50%, if no significant extinction is produced by newly formed dust. Further multiband observations are required in order to confirm the identification of the object as the companion star. If confirmed, the companion star would already be dominant in the UV-optical regime, so it would readily provide a unique opportunity to perform a detailed study of its properties.
The recent detection in archival HST images of an object at the the location of supernova (SN) iP... more The recent detection in archival HST images of an object at the the location of supernova (SN) iPTF 13bvn may represent the first direct evidence of the progenitor of a Type Ib SN. The object's photometry was found to be compatible with a Wolf-Rayet pre-SN star mass of ≈ 11 M ⊙ . However, based on hydrodynamical models we show that the progenitor had a pre-SN mass of ≈ 3.5 M ⊙ and that it could not be larger than ≈ 8 M ⊙ . We propose an interacting binary system as the SN progenitor and perform evolutionary calculations that are able to self-consistently explain the light-curve shape, the absence of hydrogen, and the pre-SN photometry. We further discuss the range of allowed binary systems and predict that the remaining companion is a luminous O-type star of significantly lower flux in the optical than the pre-SN object. A future detection of such star may be possible and would provide the first robust progenitor identification for a Type-Ib SN.
Modeling of Type II‐P Supernova Light Curves. [AIP Conference Proceedings 937, 433 (2007)]. Melin... more Modeling of Type II‐P Supernova Light Curves. [AIP Conference Proceedings 937, 433 (2007)]. Melina C. Bersten, Omar Benvenuto, Mario Hamuy. Abstract. We present progress in light curve models of type II‐P supernovae (SNe ...
We present extensive optical and near-infrared photometric and spectroscopic observations of the ... more We present extensive optical and near-infrared photometric and spectroscopic observations of the stripped-envelope (SE) supernova SN 2010as. Spectroscopic peculiarities, such as initially weak helium features and low expansion velocities with a nearly flat evolution, place this object in the small family of events previously identified as transitional Type Ib/c supernovae (SNe). There is ubiquitous evidence of hydrogen, albeit weak, in this family of SNe, indicating that they are in fact a peculiar kind of Type IIb SNe that we name "flat-velocity Type IIb". The flat velocity evolution-which occurs at different levels between 6000 and 8000 km s −1 for different SNe-suggests the presence of a dense shell in the ejecta. Despite the spectroscopic similarities, these objects show surprisingly diverse luminosities. We discuss the possible physical or geometrical unification picture for such diversity. Using archival HST images we associate SN 2010as with a massive cluster and derive a progenitor age of ≈6 Myr, assuming a single star-formation burst, which is compatible with a Wolf-Rayet progenitor. Our hydrodynamical modelling, on the contrary, indicates the pre-explosion mass was relatively low, of ≈4 M ⊙ . The seeming contradiction between an young age and low pre-SN mass may be solved by a massive interacting binary progenitor.
ABSTRACT We perform binary stellar evolutionary calculations following the simultaneous evolution... more ABSTRACT We perform binary stellar evolutionary calculations following the simultaneous evolution of both stars in the system to study a potential progenitor system for the Type IIb supernova 2011dh. Pre-explosion photometry as well as light-curve modeling have provided constraints on the physical properties of the progenitor system. Here we present a close binary system that is compatible with such constraints. The system is formed by stars of solar composition with 16 Msun + 10 Msun on a circular orbit with an initial period of 125 days. The primary star ends its evolution as a yellow supergiant with a mass of ~4 Msun, a final hydrogen content of ~3-5E-03 Msun and with an effective temperature and luminosity in agreement with the HST pre-explosion observations of SN 2011dh. These results are nearly insensitive to the adopted accretion efficiency factor beta. At the time of explosion, the companion star has an effective temperature of 22 to 40 thousand Kelvin, depending on the value of beta, and lies near the zero age main sequence. Considering the uncertainties in the HST pre-SN photometry the secondary star is only marginally detectable in the bluest observed band. Close binary systems, as opposed to single stars, provide a natural frame to explain the properties of SN 2011dh.
A set of hydrodynamical models based on stellar evolutionary progenitors is used to study the nat... more A set of hydrodynamical models based on stellar evolutionary progenitors is used to study the nature of SN 2011dh. Our modeling suggests that a large progenitor star-with R ∼ 200 R -is needed to reproduce the early light curve (LC) of SN 2011dh. This is consistent with the suggestion that the yellow super-giant star detected at the location of the supernova (SN) in deep pre-explosion images is the progenitor star. From the main peak of the bolometric LC and expansion velocities, we constrain the mass of the ejecta to be ≈2 M , the explosion energy to be E = (6-10) × 10 50 erg, and the 56 Ni mass to be approximately 0.06 M . The progenitor star was composed of a helium core of 3-4 M and a thin hydrogen-rich envelope of ≈0.1M with a main-sequence mass estimated to be in the range of 12-15 M . Our models rule out progenitors with helium-core masses larger than 8 M , which correspond to M ZAMS 25M . This suggests that a single star evolutionary scenario for SN 2011dh is unlikely.
We present bolometric light curves of Type II-plateau supernovae (SNe II-P) obtained using a newl... more We present bolometric light curves of Type II-plateau supernovae (SNe II-P) obtained using a newly developed, one-dimensional Lagrangian hydrodynamic code with flux-limited radiation diffusion. Using our code we calculate the bolometric light curve and photospheric velocities of SN 1999em obtaining a remarkably good agreement with observations despite the simplifications used in our calculation. The physical parameters used in our calculation are E = 1.25 foe, M = 19 M ⊙ , R = 800 R ⊙ and M Ni = 0.056 M ⊙ . We find that an extensive mixing of 56 Ni is needed in order to reproduce a plateau as flat as that shown by the observations. We also study the possibility to fit the observations with lower values of the initial mass consistently with upper limits that have been inferred from pre-supernova imaging of SN 1999em in connection with stellar evolution models. We cannot find a set of physical parameters that reproduce well the observations for models with pre-supernova mass of ≤ 12 M ⊙ , although models with 14 M ⊙ cannot be fully discarded.
In this paper we study the "standardized candle method" using a sample of 37 nearby (redshift z <... more In this paper we study the "standardized candle method" using a sample of 37 nearby (redshift z < 0.06) Type II plateau supernovae having BV RI photometry and optical spectroscopy. An analytic procedure is implemented to fit light curves, color curves, and velocity curves. We find that the V − I color toward the end of the plateau can be used to estimate the host-galaxy reddening with a precision of σ(A V ) = 0.2 mag. The correlation between plateau luminosity and expansion velocity previously reported in the literature is recovered. Using this relation and assuming a standard reddening law (R V = 3.1), we obtain Hubble diagrams in the BV I bands with dispersions of ∼ 0.4 mag. Allowing R V to vary and minimizing the spread in the Hubble diagrams, we obtain a dispersion range of 0.25-0.30 mag, which implies that these objects can deliver relative distances with precisions of 12-14%. The resulting best-fit value of R V is 1.4 ± 0.1.
We propose an alternative explanation for the post-breakout emission of SN 2008D associated with ... more We propose an alternative explanation for the post-breakout emission of SN 2008D associated with the X-ray transient 080109. Observations of this object show a very small contrast of 0.35 dex between the light-curve minimum occurring soon after the breakout, and the main luminosity peak that is due to radioactive heating of the ejecta. Hydrodynamical models show that the cooling of a shocked Wolf-Rayet star leads to a much greater difference ( 0.9 dex). Our proposed scenario is that of a jet produced during the explosion which deposits 56 Ni-rich material in the outer layers of the ejecta. The presence of high-velocity radioactive material allows us to reproduce the complete luminosity evolution of the object. Without outer 56 Ni it could be possible to reproduce the early emission purely from cooling of the shocked envelope by assuming a larger progenitor than a Wolf-Rayet star, but that would require an initial density structure significantly different from what is predicted by stellar evolution models. Analytic models of the cooling phase have been proposed reproduce the early emission of SN 2008D with an extended progenitor. However, we found that the models are valid only until 1.5 days after the explosion where only two data of SN 2008D are available. We also discuss the possibility of the interaction of the ejecta with a binary companion, based on published analytic expressions. However, the binary separation required to fit the early emission should be 3 R ⊙ , which is too small for a system containing two massive stars.
Recently, Chornock and co-workers announced the Pan-STARRS discovery of a transient source reachi... more Recently, Chornock and co-workers announced the Pan-STARRS discovery of a transient source reaching an apparent peak luminosity of ∼4 × 10 44 erg s −1 . We show that the spectra of this transient source are well fit by normal Type Ia supernova (SNIa) templates. The multi-band colors and lightcurve shapes are also consistent with normal SNeIa at the spectroscopically determined redshift of z = 1.3883; however, the observed flux is a constant factor of ∼30 times too bright in each band over time as compared to the templates. At minimum, this shows that the peak luminosities inferred from the light-curve widths of some SNeIa will deviate significantly from the established, empirical relation used by cosmologists. We argue on physical grounds that the observed fluxes do not reflect an intrinsically luminous SNIa, but rather PS1-10afx is a normal SNIa whose flux has been magnified by an external source. The only known astrophysical source capable of such magnification is a gravitational lens. Given the lack of obvious lens candidates, such as galaxy clusters, in the vicinity, we further argue that the lens is a supermassive black hole or a comparatively low-mass dark matter halo. In this case, the lens continues to magnify the underlying host galaxy light. If confirmed, this discovery could impact a broad range of topics including cosmology, gamma-ray bursts, and dark matter halos.
Presentamos los progresos en el modelado de curvas de luz de supernovas de tipo II plateau (SNe I... more Presentamos los progresos en el modelado de curvas de luz de supernovas de tipo II plateau (SNe II-P) obtenidos a partir de un código hidrodinámico unidimensional que recientemente hemos desarrollado. Usando modelos iniciales simples (polítropas) reprodujimos el comportamiento global de las curvas de luz observadas y analizamos la sensibilidad de la curva de luz a la variación de los parámetros libres.
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Papers by Melina Bersten