* Astronomy

Title: 500 Days of SN 2013dy: spectra and photometry from the ultraviolet to the infrared
Author: Y.-C. Pan, R. J. Foley, P. Challis, K. I. Clubb, A. V. Filippenko, G. Folatelli, O. D. Fox, M. L. Graham, W. Hillebrandt, R. P. Kirshner, M. Kromer, W. H. Lee, R. Pakmor, F. Patat, M. M. Phillips, G. Pignata, F. Roepke, I. Seitenzahl, J. M. Silverman, J. D. Simon, A. Sternberg, M. D. Stritzinger, S. Taubenberger, J. Vinko, J. C. Wheeler, W. Zheng

SN 2013dy is a relatively normal SN Ia for which we have compiled an extraordinary dataset spanning from 0.1 to ~ 500 days after explosion. We present 10 epochs of ultraviolet (UV) through near-infrared (NIR) spectra with HST/STIS, 48 epochs of optical spectra (15 of them having high resolution), and more than 500 photometric observations in the BVrRiIZYJH bands. SN 2013dy has a somewhat broad and slowly declining light curve (delta m(B) = 0.92 mag), shallow Si II 6355 absorption, and a low velocity gradient. We detect strong C II in our earliest spectra, probing unburned progenitor material in the outermost layers of the SN ejecta, but this feature fades within a few days. The UV continuum of SN 2013dy, which is strongly affected by the metal abundance of the progenitor star, indicates that SN 2013dy had a relatively high-metallicity progenitor. Examining the largest single set of high-resolution spectra for a SN Ia, we find no evidence of variable absorption from circumstellar material. Combining our UV spectra, NIR photometry, and high-cadence optical photometry, we construct a bolometric light curve, showing that SN 2013dy had a maximum luminosity of 1.0 x10⁴³ erg/s. We compare the synthetic light curves and spectra of several models to SN 2013dy, finding that SN 2013dy is most consistent with a solar-metallicity W7 model.

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Ed ~ Supernova 2013dy in NGC 7250 (Lacerta) = PSN J22181760+4034096.