The nearby Type Ibn supernova 2015G: signatures of asymmetry and progenitor constraints

November 2017 • 2017MNRAS.471.4381S

Authors • Shivvers, Isaac • Zheng, WeiKang • Van Dyk, Schuyler D. • Mauerhan, Jon • Filippenko, Alexei V. • Smith, Nathan • Foley, Ryan J. • Mazzali, Paolo • Kamble, Atish • Kilpatrick, Charles D. • Margutti, Raffaella • Yuk, Heechan • Graham, Melissa L. • Kelly, Patrick L. • Andrews, Jennifer • Matheson, Thomas • Wood-Vasey, W. Michael • Ponder, Kara A. • Brown, Peter J. • Chevalier, Roger • Milisavljevic, Dan • Drout, Maria • Parrent, Jerod • Soderberg, Alicia • Ashall, Chris • Piascik, Andrzej • Prentice, Simon

Abstract • We present the results of an extensive observational campaign on the nearby Type Ibn SN 2015G, including data from radio through ultraviolet wavelengths. SN 2015G was asymmetric, showing late-time nebular lines redshifted by ∼1000 km s-1. It shared many features with the prototypical SN Ibn 2006jc, including extremely strong He I emission lines and a late-time blue pseudo-continuum. The young SN 2015G showed narrow P-Cygni profiles of He I, but never in its evolution did it show any signature of hydrogen - arguing for a dense, ionized and hydrogen-free circumstellar medium moving outward with a velocity of ∼1000 km s-1 and created by relatively recent mass-loss from the progenitor star. Ultraviolet through infrared observations show that the fading SN 2015G (which was probably discovered some 20 d post-peak) had a spectral energy distribution that was well described by a simple, single-component blackbody. Archival HST images provide upper limits on the luminosity of SN 2015G's progenitor, while non-detections of any luminous radio afterglow and optical non-detections of outbursts over the past two decades provide constraints upon its mass-loss history.


IPAC Authors

Schuyler Van Dyk

Senior Scientist