Supernovae double-peaked light curves from double-nickel distribution

Fil: Bersten, Melina C. Instituto de Astrofísica de La Plata, CONICET-UNLP; Argentina.Fil: Orellana, Mariana D. Universidad Nacional de Río Negro. Río Negro; Argentina.Fil: Orellana, Mariana D. CONICET; Argentina.Among supernovae (SNe) of different luminosities, many double-peaked light curves (LCs) have been observed, representing a broad morphological variety. In this work, we investigate which of these can be modelled by assuming a double-peaked distribution of their radioactive material, as originally proposed for SN2005bf. The inner zone corresponds to the regular explosive nucleosynthesis and extends outwards, according to the usual scenario of mixing. The outer 56Ni-rich shell may be related to the effect of jet-like outflows that have interacted with more distant portions of the star before the arrival of the SN shock. As the outer layer is covered by matter that is optically less thick, its energy emerges earlier and generates a first peak of radiation. To investigate this scenario in more detail, we have applied our hydrodynamic code that follows the shock propagation through the progenitor star and takes into account the effect of the gamma-ray photons produced by the decay of the radioactive isotopes. We present a simple parametric model for the 56Ni abundance profile and explore the consequences on the LC of individually varying the quantities that define this distribution, setting our focus onto the stripped-envelope progenitors. In this first study, we are interested in the applicability of this model to SNe that have not been classified as superluminous, thus, we have selected our parameter space accordingly. Then, within the same mathematical prescription for the 56Ni-profile, we revisited the modelling process for a series of objects: SN2005bf, PTF2011mnb, SN2019cad, and SN2008D. In some cases, a decrease in the gamma ray opacity is required to fit the late time observations. We also discuss the other cases in which this scenario might be likely to explain the LC morphology.Entre las supernovas (SNe) de diferentes luminosidades, se han observado muchas curvas de luz (LC) de doble pico, que representan una amplia variedad morfológica. En este trabajo, investigamos cuáles de estos pueden modelarse asumiendo una distribución de doble pico de su material radiactivo, como se propuso originalmente para SN2005bf. La zona interior corresponde a la nucleosíntesis explosiva regular y se extiende hacia el exterior, según el escenario habitual de mezcla. La capa exterior rica en 56Ni puede estar relacionada con el efecto de flujos de salida similares a chorros que han interactuado con porciones más distantes de la estrella antes de la llegada del choque de la SN. Como la capa exterior está cubierta por materia ópticamente menos gruesa, su energía emerge antes y genera un primer pico de radiación. Para investigar este escenario con más detalle, hemos aplicado nuestro código hidrodinámico que sigue la propagación del choque a través de la estrella progenitora y tiene en cuenta el efecto de los fotones de rayos gamma producidos por la desintegración de los isótopos radiactivos. Presentamos un modelo paramétrico simple para el perfil de abundancia de 56Ni y exploramos las consecuencias en la LC de variar individualmente las cantidades que definen esta distribución, centrándonos en los progenitores despojados de envoltura. En este primer estudio, estamos interesados ​​en la aplicabilidad de este modelo a SNe que no han sido clasificados como superluminosos, por lo que hemos seleccionado nuestro espacio de parámetros en consecuencia. Luego, dentro de la misma prescripción matemática para el perfil de 56Ni, revisamos el proceso de modelado para una serie de objetos: SN2005bf, PTF2011mnb, SN2019cad y SN2008D. En algunos casos, se requiere una disminución en la opacidad de los rayos gamma para adaptarse a las observaciones tardías. También discutimos los otros casos en los que este escenario podría explicar la morfología de LC

The Unusual Super-Luminous Supernovae SN 2011kl and ASASSN-15lh

Two recently discovered very luminous supernovae (SNe) present stimulating cases to explore the extents of the available theoretical models. SN 2011kl represents the first detection of a supernova explosion associated with an ultra-long duration gamma ray burst. ASASSN-15lh was even claimed as the most luminous SN ever discovered, challenging the scenarios so far proposed for stellar explosions. Here we use our radiation hydrodynamics code in order to simulate magnetar powered SNe. To avoid explicitly assuming neutron star properties we adopt the magnetar luminosity and spin-down timescale as free parameters of the model. We find that the light curve (LC) of SN 2011kl is consistent with a magnetar power source, as previously proposed, but we note that some amount of 56^Ni (> 0.08 M_sun) is necessary to explain the low contrast between the LC peak and tail. For the case of ASASSN-15lh we find physically plausible magnetar parameters that reproduce the overall shape of the LC provided the progenitor mass is relatively large (a mass of the ejecta approx 6 M_sun). The ejecta hydrodynamics of this event is dominated by the magnetar input, while the effect is more moderate for SN 2011kl. We conclude that a magnetar model may be used for the interpretation of these events and that the hydrodynamic modeling is necessary to derive the properties of powerful magnetars and their progenitors.Comment: Accepted by Astrophysical Journal Letters, 5 pages, 5 figure

Double-peaked SuperNovae

Fil: Bersten, M. CCT-CONICET-UNLP. Instituto de Astrofísica de La Plata (IALP), La Plata, Argentina.Fil: Orellana, Mariana. CONICET; Argentina.Fil: Orellana, Mariana. Universidad Nacional de Río Negro. Río Negro, Argentina.Se adjunta versión aceptada para su publicaciónThrough hydrodynamical 1D simulations we explore two of the more promissing physical scenarios invoked to explain peculiar double-peaked supenovae. One consists of a double radioactive nickel distribution formed when some of this material is pushed out by a putative jet that is related to the supernova explosion. The other scenario has only outer nickel, but the main peak is powered by a newly born magnetar. We present the whole evolution of the bolometric light curve for a helium-rich progenitor. The main goal is to compare the resulting bolometric light curves (LCs) and to confirm the fact that, for some parameters, the two peaks are clearly departed, being the latter a brigther and broader main peak.A través de simulaciones hidrodinámicas 1D, exploramos dos de los escenarios físicos más prometedores invocados para explicar las peculiares supernovas de doble pico. Uno consiste en una doble distribución de níquel radiactivo que se forma cuando parte de este material es expulsado por un supuesto chorro que está relacionado con la explosión de la supernova. El otro escenario solo tiene níquel exterior, pero el pico principal es impulsado por una magnetar recientemente formado. Presentamos toda la evolución de la curva de luz bolométrica para un progenitor rico en helio. El objetivo principal es comparar las curvas de luz bolométricas resultantes y confirmar el hecho de que, para algunos parámetros, los dos picos están claramente separados, siendo este último un pico principal más ancho y brillante

Early UV/Optical Emission of The Type Ib SN 2008D

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 56Ni-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 56Ni 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 Rsun which is too small for a system containing two massive stars.Comment: 10 pages, 10 figures, Accepted for publication in Ap

The Progenitor of the Type IIb SN 2008ax Revisited

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.Comment: ApJ accepted, 14 pages, 7 figure

Curvas de luz de supernovas superluminosas: modelos hidrodinámicos

Fil: Orellana, Mariana. Universidad Nacional de Río Negro. Río Negro, Argentina.Fil: Orellana, Mariana. Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Argentina.Fil: Bersten, Melina. Instituto de Astrofísica de La Plata, CONICET-UNLP; Argentina.Fil: Benvenuto, Omar G. Instituto de Astrofísica de La Plata, CONICET-UNLP; Argentina.Fil: Benvenuto, Omar G. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires, Argentina.Superluminous supernovae (SLSNe) have only recently been detected. The physical origins of their extreme luminosity, a factor 10 to 100 times brighter than normal SNe, remains speculative. One popular mechanism invoked to explain SLSNe is that a magnetar is formed by the collapse of a massive star. The magnetar is a strongly-magnetized, rapidly-rotating neutron star that loses rotational energy via magnetic dipole radiation. That energy provides the extra kick and luminosity for the SLSN. We study the effect of the shock wave propagation through the envelope with the spindown of the magnetar as the central engine. First we reproduce the analytic simplified treatment that is popular in the literature and then compare the results from our radiative hydrodynamic code. The magnetar properties can be constrained through fitting of the observed light curve. As an illustration, we apply this method to SN 2011kg.Las supernovas superluminosas (SLSNe) se han detectado recientemente. Los orígenes físicos de su extrema luminosidad, un factor de 10 a 100 veces más brillante que el SNe normal, siguen siendo especulaciones. Un mecanismo popular invocado para explicar SLSNe es que una magnetar se forma por el colapso de una estrella masiva. El magnetar es una estrella de neutrones fuertemente magnetizada y de rotación rápida que pierde energía de rotación a través de la radiación del dipolo magnético. Esa energía proporciona la patada extra y la luminosidad para el SLSN. Estudiamos el efecto de la propagación de la onda de choque a través de la envolvente con el spindown de la magnetar como motor central. Primero reproducimos el tratamiento analítico simplificado que es popular en la literatura y luego comparamos los resultados de nuestro código hidrodinámico radiativo. Las propiedades del magnetar se pueden restringir mediante el ajuste de la curva de luz observada. Como ilustración, aplicamos este método a SN 2011kg

Supernovas superluminosas de Tipo II Plateau

Fil: Orellana, Mariana D. Universidad Nacional de Río Negro; ArgentinaFil: Orellana, Mariana D. CONICET; ArgentinaFil: Bersten, Melina C. Universidad Nacional de La Plata. Instituto de Astrofísica de La Plata (IALP), CCT-CONICET; ArgentinaFil: Bersten, Melina C. CONICET; ArgentinaCorresponde a una presentación oral en la reunión anual de la AAA.We have incorporated the effect of the energy injection provided by a magnetar as an additional source to power the light curve of superlumine supernovae, that is, supernovae that shine between ten and one hundred times more than usual. We study in greater detail the case of hydrogen-rich progenitor stars. We present results of our exploration of the space of physical parameters that lead to different morphologies of the light curves. We identified cases that develop a quasi-constant luminosity phase, and would preserve the plateau classification defined for normal supernovae.Hemos incorporado el efecto de la inyección de energía proporcionada por un magnetar como fuente adicional para alimentar la curva de luz de las supernovas superluminas, es decir, las supernovas que brillan entre diez y cien veces más de lo habitual. Estudiamos con mayor detalle el caso de las estrellas progenitoras ricas en hidrógeno. Presentamos los resultados de nuestra exploración del espacio de parámetros físicos que conducen a diferentes morfologías de las curvas de luz. Identificamos casos que desarrollan una fase de luminosidad casi constante y preservarían la clasificación de meseta definida para supernovas normales

Magnetares como fuentes para potenciar supernovas peculiares

Fil: Bersten, Melina C. CONICET; ArgentinaFil: Orellana, Mariana D. CONICET; ArgentinaFil: Bersten, Melina C. Universidad Nacional de La Plata. Instituto de Astrofísica de La Plata (IALP), CCT-CONICET; ArgentinaFil: Orellana, Mariana D. Universidad Nacional de Río Negro. Laboratorio de Procesamiento de Señales Aplicado y Computación de Alto Rendimiento; ArgentinaAdjunto la versión que ha sido aceptada, está en prensa a la fecha (18/4)Hemos incorporado el efecto de la inyección de energía sostenida por un magnetar en las simulaciones hidrodinámicas de supernovas (SNe) de Bersten et al. (2011). La variación de las propiedades de la eyecta y del magnetar introducen cambios en la curva de luz (tiempo de aumento, luminosidad máxima, ancho). Mostramos los rasgos más importantes de las morfologías encontradas para las curvas de luz de una población sintética de SNe con y sin hidrógeno. Como parte del trabajo en curso, buscamos los parámetros que expliquen los datos observacionales de SN2018cow que es una SN brillante que a diferencia del general de las SNe superluminosas, fue muy cercana (60 Mpc). Ha llamado la atención dada la rápida evolución de su curva de luz. Ha sido objeto de numerosas campañas multifrecuencia y de debatidas ideas teóricas para explicarla. La propuesta de un magnetar no es nueva en este caso, pero sí el cálculo hidrodinámico, como mejora a propuestas más simplificadoras que se presentan en la literatura

iPTF13bvn: The First Evidence of a Binary Progenitor for a Type Ib Supernova

The recent detection in archival HST images of an object at the the location of supernova (SN) iPTF13bvn 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 Msun. However, based on hydrodynamical models we show that the progenitor had a pre-SN mass of ~3.5 Msun and that it could not be larger than ~8 Msun. 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 identification of a progenitor system for a Type Ib SN.Comment: Accepted to AJ on July 26. Slight changes from original, however delayed by slow refereeing proces