Extensive Spectroscopy and Photometry of the Type IIP Supernova 2013ej

Dhungana, G. and Biró, B. I. and Borkovits, T. and Hegedűs, T. and Kelemen, J. and Molnár, L. and Nagy, A. P. (2016) Extensive Spectroscopy and Photometry of the Type IIP Supernova 2013ej. The Astrophysical Journal, 822. p. 6. ISSN 2041-8205

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Abstract

We present extensive optical (UBVRI, g′r′i′z′, and open CCD) and near-infrared (ZYJH) photometry for the very nearby Type IIP SN ~2013ej extending from +1 to +461 days after shock breakout, estimated to be MJD 56496.9±0.3. Substantial time series ultraviolet and optical spectroscopy obtained from +8 to +135 days are also presented. Considering well-observed SNe IIP from the literature, we derive UBVRIJHK bolometric calibrations from UBVRI and unfiltered measurements that potentially reach 2\% precision with a B−V color-dependent correction. We observe moderately strong Si II λ6355 as early as +8 days. The photospheric velocity (vph) is determined by modeling the spectra in the vicinity of Fe II λ5169 whenever observed, and interpolating at photometric epochs based on a semianalytic method. This gives vph=4500±500 km s−1 at +50 days. We also observe spectral homogeneity of ultraviolet spectra at +10--12 days for SNe IIP, while variations are evident a week after explosion. Using the expanding photosphere method, from combined analysis of SN 2013ej and SN 2002ap, we estimate the distance to the host galaxy to be 9.0+0.4−0.6 Mpc, consistent with distance estimates from other methods. Photometric and spectroscopic analysis during the plateau phase, which we estimated to be 94±7 days long, yields an explosion energy of 0.9±0.3×1051 ergs, a final pre-explosion progenitor mass of 15.2±4.2~M⊙ and a radius of 250±70~R⊙. We observe a broken exponential profile beyond +120 days, with a break point at +183±16 days. Measurements beyond this break time yield a 56Ni mass of 0.013±0.001~M⊙.

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