Study of the Dependence of the Plateau Shape for Type II Supernovae on Metallicity
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y of the Dependence of the Plateau Shape for Type II Supernovae on Metallicity A. A. Goldshtein1* and S. I. Blinnikov2, 3, 4** 1
St. Petersburg State University, Ul’yanovskaya ul. 1, Petrodvoretz, St. Petersburg, 198504 Russia 2 Alikhanov Institute for Theoretical and Experimental Physics, ul. Bol’shaya Cheremushkinskaya 25, Moscow, 117218 Russia 3 Sternberg Astronomical Institute, Moscow State University, Universitetskii pr. 13, Moscow, 119992 Russia 4 Center for Fundamental and Applied Research, Dukhov All-Russia Research Institute of Automatics, ul. Sushchevskaya 22, Moscow, 127055 Russia Received April 21, 2020; revised April 28, 2020; accepted April 28, 2020
Abstract—We consider the effect of a change in the rate of flux decline in the U band for type II-P supernovae (SNe IIP) as a function of metallicity Z. Based on this effect, we propose a new method to determine the photometric redshift from the SN IIP light curve in the U band. Using the STELLA code, we have constructed model light curves in different bands for different redshifts z = 0.0, 0.1, and 0.3 as the metallicity in the models decreases from Z ∼ 10−3 to ∼10−6 . The flux in the U band is shown to reach a plateau at the lowest metallicities. We consider the influence of other parameters as well: the presupernova mass and the mass of radioactive nickel-56. DOI: 10.1134/S1063773720050047 Keywords: supernovae, light curves, photometric redshift.
INTRODUCTION Observations of classical type II plateau supernovae, SNe IIP, show that in the U , R, V , I, and Z bands the fluxes do remain constant for two or three months, i.e., form a “plateau” that gave the name to this type. At the same time, the fluxes in the U band decline steeply linearly (see, e.g., Leonard et al. 2002; Hicken et al. 2017). A less steep decline is observed in the B band. This behavior of the light curves in different bands cannot be described using the “gray” approximation in computations, which is used, for example, in the open source SNEC code (Morozova et al. 2015), where the assumption about blackbody radiation by the photosphere (with bolometric corrections) is applied to construct the light curves in different bands. The light curve constructed in this way for the U band does not reproduce the observations, because the enhanced absorption by metals in the ultraviolet in the cold above-photosphere layers of the SN ejecta is required to be taken into account here. One of the first successful computations of the effect of a linear flux decline in the U band was the * **
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application of the EDDINGTON code for SNe IIP (Eastman et al. 1994). The STELLA code (Blinnikov and Sorokina 2000; Blinnikov et al. 2006), which does not use the gray approximation, but is based on multigroup radiative transfer, allows the observed effect to be described realistically. Depending on the presupernova parameters, the slope of the linear decline in the U band can change. Baklanov et al. (2005) noticed how the metallicity of the presupernova envelope affects
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