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.
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.
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 ...
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.
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.
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.
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 ...
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.
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Papers by Melina Bersten