Searching for the Expelled Hydrogen Envelope in Type I Supernovae via Late-Time Hα Emission

• Published in: The Astrophysical journal Vol. 837; no. 1; p. 62
• Main Authors: Vinko, J., Pooley, D., Silverman, J. M., Wheeler, J. C., Szalai, T., Kelly, P., MacQueen, P., Marion, G. H., Sárneczky, K.
• Format: Journal Article
• Language: English
• Published: Philadelphia IOP Publishing 01-03-2017
• Subjects: Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BALMER LINES; COLLISIONS; Ejecta; EMISSION; EXPLOSIONS; H alpha line; H II regions; HYDROGEN; INTERACTIONS; MASS TRANSFER; Narrowband; Point sources; SHOCK WAVES; Stellar envelopes; STELLAR WINDS; Supernovae; TYPE I SUPERNOVAE; VELOCITY; X RADIATION
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/aa607e

Abstract
We report the first results from our long-term observational survey aimed at discovering late-time interaction between the ejecta of hydrogen-poor Type I supernovae (SNe I) and the hydrogen-rich envelope expelled from the progenitor star several decades/centuries before explosion. The expelled envelope, moving with a velocity of ∼10–100 km s
−1
, is expected to be caught up by the fast-moving SN ejecta several years/decades after explosion, depending on the history of the mass-loss process acting in the progenitor star prior to explosion. The collision between the SN ejecta and the circumstellar envelope results in net emission in the Balmer lines, especially H
α
. We look for signs of late-time H
α
emission in older SNe Ia/Ibc/IIb with hydrogen-poor ejecta via narrowband imaging. Continuum-subtracted H
α
emission has been detected for 13 point sources: 9 SN Ibc, 1 SN IIb, and 3 SN Ia events. Thirty-eight SN sites were observed on at least two epochs, from which three objects (SN 1985F, SN 2005kl, and SN 2012fh) showed significant temporal variation in the strength of their H
α
emission in our Direct Imaging Auxiliary Functions Instrument (DIAFI) data. This suggests that the variable emission is probably not due to nearby H
ii
regions unassociated with the SN and hence is an important additional hint that ejecta–circumstellar medium interaction may take place in these systems. Moreover, we successfully detected the late-time H
α
emission from the Type Ib SN 2014C, which was recently discovered as a strongly interacting SN in various (radio, infrared, optical, and X-ray) bands.