Discovery and Follow-up Observations of the Young Type Ia Supernova 2016coj

May 2017 • 2017ApJ...841...64Z

Authors • Zheng, WeiKang • Filippenko, Alexei V. • Mauerhan, Jon • Graham, Melissa L. • Yuk, Heechan • Hosseinzadeh, Griffin • Silverman, Jeffrey M. • Rui, Liming • Arbour, Ron • Foley, Ryan J. • Abolfathi, Bela • Abramson, Louis E. • Arcavi, Iair • Barth, Aaron J. • Bennert, Vardha N. • Brandel, Andrew P. • Cooper, Michael C. • Cosens, Maren • Fillingham, Sean P. • Fulton, Benjamin J. • Halevi, Goni • Howell, D. Andrew • Hsyu, Tiffany • Kelly, Patrick L. • Kumar, Sahana • Li, Linyi • Li, Wenxiong • Malkan, Matthew A. • Manzano-King, Christina • McCully, Curtis • Nugent, Peter E. • Pan, Yen-Chen • Pei, Liuyi • Scott, Bryan • Sexton, Remington Oliver • Shivvers, Isaac • Stahl, Benjamin • Treu, Tommaso • Valenti, Stefano • Vogler, H. Alexander • Walsh, Jonelle L. • Wang, Xiaofeng

Abstract • The Type Ia supernova (SN Ia) 2016coj in NGC 4125 (redshift z = 0.00452 ± 0.00006) was discovered by the Lick Observatory Supernova Search 4.9 days after the fitted first-light time (FFLT; 11.1 days before B-band maximum). Our first detection (prediscovery) is merely 0.6 ± 0.5 days after the FFLT, making SN 2016coj one of the earliest known detections of an SN Ia. A spectrum was taken only 3.7 hr after discovery (5.0 days after the FFLT) and classified as a normal SN Ia. We performed high-quality photometry, low- and high-resolution spectroscopy, and spectropolarimetry, finding that SN 2016coj is a spectroscopically normal SN Ia, but the velocity of Si II λ6355 around peak brightness (∼12,600 {km} {{{s}}}-1) is a bit higher than that of typical normal SNe. The Si II λ6355 velocity evolution can be well fit by a broken-power-law function for up to a month after the FFLT. SN 2016coj has a normal peak luminosity ({M}B≈ -18.9+/- 0.2 mag), and it reaches a B-band maximum ∼16.0 days after the FFLT. We estimate there to be low host-galaxy extinction based on the absence of Na I D absorption lines in our low- and high-resolution spectra. The spectropolarimetric data exhibit weak polarization in the continuum, but the Si II line polarization is quite strong (∼0.9% ± 0.1%) at peak brightness.


IPAC Authors


Benjamin Fulton

Assistant Scientist