In this paper, we present extensive optical and ultraviolet (UV) observations of the type Ia supernova (SN Ia) 2013gs discovered during the Tsinghua-NAOC Transient Survey. The photometric observations in the optical show that the light curves of SN 2013gs is similar to that of normal SNe Ia, with an absolute peak magnitude of MB = −19.25 ± 0.15 mag and a post-maximum decline rate Δm15(B) = 1.00 ± 0.05 mag. \emph{Gehrels Swift} UVOT observations indicate that SN 2013gs shows unusually strong UV emission (especially in the uvw1 band) at around the maximum light (Muvw1∼−18.9 mag). The SN is characterized by relatively weak Fe~{\sc ii} {\sc iii} absorptions at ∼ 5000{\AA} in the early spectra and a larger expansion velocity (vSi∼ 13,000 km s−1 around the maximum light) than the normal-velocity SNe Ia. We discuss the relation between the uvw1−v color and some observables, including Si~{\sc ii} velocity, line strength of Si~{\sc ii} λ6355, Fe~{\sc ii}/{\sc iii} lines and Δm15(B). Compared to other fast-expanding SNe Ia, SN 2013gs exhibits Si and Fe absorption lines with similar strength and bluer uvw1−v color. We briefly discussed the origin of the observed UV dispersion of SNe Ia.
@article{arxiv.1901.01353,
title = {Observations of A Fast-Expanding and UV-Bright Type Ia Supernova SN 2013gs},
author = {Tianmeng Zhang and Xiaofeng Wang and Xulin Zhao and Dong Xu and Andrea Reguitti and Jujia Zhang and Andrea Pastorello and Lina Tomasella and Paolo Ochner and Leonardo Tartaglia and Stefano Benetti and Massimo Turatto and Avet Harutyunyan and Nancy Elias-Rosa and Fang Huang and Kaicheng Zhang and Juncheng Chen and Zhaoji Jiang and Jun Ma and Jundan Nie and Xiyan Peng and Xu Zhou and Zhimin Zhou and Hu Zou},
journal= {arXiv preprint arXiv:1901.01353},
year = {2019}
}