Color Me Intrigued: The Discovery of iPTF 16fnm, an SN 2002cx-like Object

October 2017 • 2017ApJ...848...59M

Authors • Miller, A. A. • Kasliwal, M. M. • Cao, Y. • Adams, S. M. • Goobar, A. • Knežević, S. • Laher, R. R. • Lunnan, R. • Masci, F. J. • Nugent, P. E. • Perley, D. A. • Petrushevska, T. • Quimby, R. M. • Rebbapragada, U. D. • Sollerman, J. • Taddia, F. • Kulkarni, S. R.

Abstract • Modern wide-field, optical time-domain surveys must solve a basic optimization problem: maximize the number of transient discoveries or minimize the follow-up needed for the new discoveries. Here, we describe the Color Me Intrigued experiment, the first from the intermediate Palomar Transient Factory (iPTF) to search for transients simultaneously in the g _PTF and R _PTF bands. During the course of this experiment, we discovered iPTF 16fnm, a new member of the 02cx-like subclass of Type Ia supernovae (SNe). iPTF 16fnm peaked at {M}_{g{PTF}}=-15.09+/- 0.17 {mag}, making it the second-least-luminous known SN Ia. iPTF 16fnm exhibits all the hallmarks of the 02cx-like class: (I) low luminosity at peak, (II) low ejecta velocities, and (III) a non-nebular spectrum several months after peak. Spectroscopically, iPTF 16fnm exhibits a striking resemblance to two other low-luminosity 02cx-like SNe: SN 2007qd and SN 2010ae. iPTF 16fnm and SN 2005hk decline at nearly the same rate, despite a 3 mag difference in brightness at peak. When considering the full subclass of 02cx-like SNe, we do not find evidence for a tight correlation between peak luminosity and decline rate in either the g‧ or r‧ band. We measure the relative rate of 02cx-like SNe to normal SNe Ia and find {r}_{N02{cx}/{N}_{Ia}}={33}_-25⁺¹⁵⁸ % . We further examine the g‧ - r‧ evolution of 02cx-like SNe and find that their unique color evolution can be used to separate them from 91bg-like and normal SNe Ia. This selection function will be especially important in the spectroscopically incomplete Zwicky Transient Facility/Large Synoptic Survey Telescope (LSST) era. Finally, we close by recommending that LSST periodically evaluate, and possibly update, its observing cadence to maximize transient science.

Links

• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2017ApJ...848...59M
• PDF https://stacks.iop.org/0004-637X/848/59/pdf
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2017ApJ...848...59M
• PREPRINT http://arxiv.org/abs/1703.07449
• ELECTR https://doi.org/10.3847%2F1538-4357%2Faa8c7e