A deeper search for the progenitor of the Type Ic supernova 2002ap

Abstract

Images of the site of the Type Ic supernova (SN) 2002ap taken before explosion were analysed previously by Smartt et al. We have uncovered new unpublished, archival pre-explosion images from the Canada-France-Hawaii Telescope (CFHT) that are vastly superior in depth and image quality. In this paper we present a further search for the progenitor star of this unusual Type Ic SN. Aligning high-resolution Hubble Space Telescope observations of the SN itself with the archival CFHT images allowed us to pinpoint the location of the progenitor site on the groundbased observations. We find that a source visible in the B-and R-band pre-explosion images close to the position of the SN is (1) not coincident with the SN position within the uncertainties of our relative astrometry and (2) is still visible ∼4.7-yr post-explosion in late-time observations taken with the William Herschel Telescope. We therefore conclude that it is not the progenitor of SN 2002ap. We derived absolute limiting magnitudes for the progenitor of M B −4.2 ± 0.5 and M R −5.1 ± 0.5. These are the deepest limits yet placed on a Type Ic SN progenitor. We rule out all massive stars with initial masses greater than 7-8 M (the lower mass limit for stars to undergo core collapse) that have not evolved to become Wolf-Rayet stars. This is consistent with the prediction that Type Ic SNe should result from the explosions of Wolf-Rayet stars. Comparing our luminosity limits with stellar models of single stars at appropriate metallicity (Z = 0.008) and with standard mass-loss rates, we find no model that produces a Wolf-Rayet star of low enough mass and luminosity to be classed as a viable progenitor. Models with twice the standard mass-loss rates provide possible single star progenitors but all are initially more massive than 30-40 M . We conclude that any single star progenitor must have experienced at least twice the standard mass-loss rates, been initially more massive than 30-40 M and exploded as a Wolf-Rayet star of final mass 10-12 M . Alternatively a progenitor star of lower initial mass may have evolved in an interacting binary system. Mazzali et al. propose such a binary scenario for the progenitor of SN 2002ap in which a star of initial mass 15-20 M is stripped by its binary companion, becoming a 5 M Wolf-Rayet star prior to explosion. We constrain any possible binary companion to a main-sequence star of 20 M , a neutron star or a black hole. By combining the pre-explosion limits with the ejecta mass estimates and constraints from X-ray and radio observations we conclude that any binary interaction most likely occurred as Case B mass transfer, either with or without a subsequent common-envelope evolution phase.

Gemini GMOS spectroscopy of HeII nebulae in M 33

“…Indeed, ground-based photometry from Massey et al (2006) indicates V = 16.14 mag, from which E(B−V) = 0.06 mag (via C Hβ = 0.09) implies M V = −8.7 mag for our assumed distance of 840 kpc. In contrast, absolute magnitudes of WN-type stars in the Large Magellanic Cloud range from -2 to -7.5 mag (Crockett et al 2007), with M V = −4 mag typical for single early-type WN stars. In addition, the stellar He II λ4686 equivalent width is W λ ∼ 3 Å, versus 30-500 Å for LMC single, early-type WN stars (Crowther & Hadfield 2006).…”

Fundamental properties of core-collapse supernova and GRB progenitors: predicting the look of massive stars before death

“…We predict that the limiting magnitudes in the observations should be at least 2 mag fainter than the current best limit in the B band to detect single star progenitors of SN Ic at distances of 10-20 Mpc. For a SN 2002ap-like detection limit (m B = 26.0 mag, Crockett et al 2007), the maximum distance that a SN Ic progenitor would be detected is ∼5.5 Mpc. For typical detection limits (m = 24.5 mag) and low amounts of extinction (0.3 mag), our models suggest that SN Ic progenitors from single stars would be detected up to a maximum distance of ∼2.7 Mpc.…”

“…For typical detection limits (m = 24.5) and low amounts of extinction (0.3 mag in a given band), this implies a maximum distance to SN Ic progenitors of 2.7 Mpc for detection. For a SN 2002ap-like detection limit (m B = 26.0 mag, Crockett et al 2007), the maximum distance would be 5.5 Mpc. Obviously, these are upper limits that would decrease if the progenitor is seen under large extinction.…”

“…Previous works employed empirical calibrations of absolute magnitudes and bolometric corrections (Yoon et al 2012;Maund & Smartt 2005;Maund et al 2005b;Crockett et al 2007). More recently, Eldridge et al (2013) employed atmospheric models of WR stars from the Potsdam group (Hamann et al 2006;Sander et al 2012) that were computed for a range of physical parameters, but not self-consistently with the evolutionary calculations.…”

Massive stars in their death throes

“…The most sensitive pre-explosion observation to date is for supernova 2002ap. The observation rules out a normal Wolf-Rayet star and favours a binary system with a low-mass Wolf-Rayet star with lower mass, M%5M 1 , than a typical Wolf-Rayet star, Mz10M 1 (Crockett et al 2007).…”