No Arabic abstract
Supernova (SN) iPTF13bvn in NGC 5806 was the first Type Ib SN to have been tentatively associated with a progenitor candidate in pre-explosion images. We performed deep ultraviolet (UV) and optical Hubble Space Telescope (HST) observations of the SN site 740 days after explosion. We detect an object in the optical bands that is fainter than the pre-explosion object. This dimming is likely not produced by dust absorption in the ejecta; thus, our finding confirms the connection of the progenitor candidate with the SN. The object in our data is likely dominated by the fading SN, which implies that the pre-SN flux is mostly due to the progenitor. We compare our revised pre-SN photometry with previously proposed progenitor models. Although binary progenitors are favored, models need to be refined. In particular, to comply with our deep UV detection limit, any companion star must be less luminous than a late-O star or substantially obscured by newly formed dust. A definitive progenitor characterization will require further observations to disentangle the contribution of a much fainter SN and its environment.
The intermediate Palomar Transient Factory reports our discovery of a young supernova, iPTF13bvn, in the nearby galaxy, NGC5806 (22.5Mpc). Our spectral sequence in the optical and infrared suggests a likely Type Ib classification. We identify a single, blue progenitor candidate in deep pre-explosion imaging within a 2{sigma} error circle of 80 mas (8.7 pc). The candidate has a MB luminosity of -5.2 +/- 0.4 mag and a B-I color of 0.1+/-0.3 mag. If confirmed by future observations, this would be the first direct detection for a progenitor of a Type Ib. Fitting a power law to the early light curve, we find an extrapolated explosion date around 1.1 days before our first detection. We see no evidence of shock cooling. The pre-explosion detection limits constrain the radius of the progenitor to be smaller than a few solar radii. iPTF13bvn is also detected in cm and mm-wavelengths. Fitting a synchrotron self-absorption model to our radio data, we find a mass loading parameter of 1.3*10^12 g/cm. Assuming a wind velocity of 10^3km/s, we derive a progenitor mass loss rate of 3*10^-5Msun/yr. Our observations, taken as a whole, are consistent with a Wolf Rayet progenitor of the supernova iPTF13bvn.
Aims. We present and analyse late-time observations of the type-Ib supernova with possible pre-supernova progenitor detection, iPTF13bvn, taken at $sim$300 days after the explosion, and discuss these in the context of constraints on the supernovas progenitor. Previous studies have proposed two possible natures for the progenitor of the supernova, i.e. a massive Wolf-Rayet star or a lower-mass star in close binary system. Methods. Our observations show that the supernova has entered the nebular phase, with the spectrum dominated by Mg~I]$lambdalambda$4571, [O~I]$lambdalambda$6300, 6364, and [Ca~II]$lambdalambda$7291, 7324 emission lines. We measured the emission line fluxes to estimate the core oxygen mass and compare the [O~I]/[Ca~II] line ratio with other supernovae. Results. The core oxygen mass of the supernova progenitor was estimated to be $lesssim$0.7 M$_odot$, which implies initial progenitor mass not exceeding $sim$15 -- 17 M$_odot$. Since the derived mass is too small for a single star to become a Wolf-Rayet star, this result lends more support to the binary nature of the progenitor star of iPTF13bvn. The comparison of [O~I]/[Ca~II] line ratio with other supernovae also shows that iPTF13bvn appears to be in close association with the lower-mass progenitors of stripped-envelope and type-II supernovae.
We present new late-time near-infrared imaging of the site of the nearby core-collapse supernova SN 2012aw, confirming the disappearance of the point source identified by Fraser et al. (2012) and Van Dyk et al. (2012) as a candidate progenitor in both J and Ks filters. We re-measure the progenitor photometry, and find that both the J and Ks magnitudes of the source are consistent with those quoted in the literature. We also recover a marginal detection of the progenitor in H-band, for which we measure H=19.67+/-0.40 mag. Comparing the luminosity of the progenitor to stellar evolutionary models, SN 2012aw appears to have resulted from the explosion of a 12.5+/-1.5 Msun red supergiant.
We report the first detection of a credible progenitor system for a Type Ic supernova (SN Ic), SN 2017ein. We present spectra and photometry of the SN, finding it to be similar to carbon-rich, low-luminosity SNe Ic. Using a post-explosion Keck adaptive optics image, we precisely determine the position of SN 2017ein in pre-explosion hst images, finding a single source coincident with the SN position. This source is marginally extended, and is consistent with being a stellar cluster. However, under the assumption that the emission of this source is dominated by a single point source, we perform point-spread function photometry, and correcting for line-of-sight reddening, we find it to have $M_{rm F555W} = -7.5pm0.2$ mag and $m_{rm F555W}-m_{rm F814W}$=$-0.67pm0.14$ mag. This source is bluer than the main sequence and brighter than almost all Wolf-Rayet stars, however it is similar to some WC+O- and B-star binary systems. Under the assumption that the source is dominated by a single star, we find that it had an initial mass of $55substack{+20-15} M_{odot}$. We also examined binary star models to look for systems that match the overall photometry of the pre-explosion source and found that the best-fitting model is a $80$+$48 M_{odot}$ close binary system in which the $80 M_{odot}$ star is stripped and explodes as a lower mass star. Late-time photometry after the SN has faded will be necessary to cleanly separate the progenitor star emission from the additional coincident emission.
The dominant radioactive energy source powering Type Ia supernova light curves is expected to switch from the decay of $^{56}$Co to $^{57}$Co at very late epochs. We use archival HST images of SN1992A obtained more than 900 days after explosion to constrain its cobalt isotopic abundance ratio and compare it to the well-studied event SN2011fe. We confirm the $^{57}$Co / $^{56}$Co ratio for SN2011fe of $0.026pm 0.004$ found by arXiv:1608.01155, consistent with a double degenerate progenitor scenario. For SN1992A, we find a ratio of $0.034pm 0.010$, but the large uncertainty does not allow us to differentiate between progenitor models