UNBURNED MATERIAL IN THE EJECTA OF TYPE Ia SUPERNOVAE
Author
- Folatelli, Gastón;
- Phillips, M. M.;
- Morrell, Nidia;
- Tanaka, Masaomi;
- Maeda, Keiichi;
- Nomoto, Ken’ichi;
- Stritzinger, Maximilian;
- Burns, Christopher R.;
- Hamuy Wackenhut, Mario;
- Mazzali, Paolo;
- Boldt, Luis;
- Campillay, Abdo;
- Contreras, Carlos;
- González Tagle, Sergio;
- Roth, Miguel;
- Salgado, Francisco;
- Freedman, W. L.;
- Madore, Barry F.;
- Persson, S. E.;
- Suntzeff, Nicholas B.;
Abstract
The presence of unburned material in the ejecta of normal Type Ia supernovae (SNe Ia) is investigated using
early-time spectroscopy obtained by the Carnegie Supernova Project. The tell-tale signature of pristine material
from a C+O white dwarf progenitor star is the presence of carbon, as oxygen is also a product of carbon burning.
The most prominent carbon lines in optical spectra of SNe Ia are expected to arise from Cii. We find that at least
30% of the objects in the sample show an absorption at ≈6300Å which is attributed to C ii λ6580. An alternative
identification of this absorption as Hα is considered to be unlikely. These findings imply a larger incidence of
carbon in SNe Ia ejecta than previously noted. We show how observational biases and physical conditions may
hide the presence of weak Cii lines, and account for the scarcity of previous carbon detections in the literature.
This relatively large frequency of carbon detections has crucial implications on our understanding of the explosive
process. Furthermore, the identification of the 6300Å absorptions as carbon would imply that unburned material is
present at very low expansion velocities, merely ≈1000 km s−1 above the bulk of Si ii. Based on spectral modeling,
it is found that the detections are consistent with a mass of carbon of 10−3 to 10−2M . The presence of this
material so deep in the ejecta would imply substantial mixing, which may be related to asymmetries of the flame
propagation. Another possible explanation for the carbon absorptions may be the existence of clumps of unburned
material along the line of sight. However, the uniformity of the relation between C ii and Si ii velocities is not
consistent with such small-scale asymmetries. The spectroscopic and photometric properties of SNe Ia with and
without carbon signatures are compared. A trend toward bluer color and lower luminosity at maximum light is
found for objects which show carbon.
General note
Artículo de publicación ISI
Identifier
URI: https://repositorio.uchile.cl/handle/2250/125628
DOI: doi:10.1088/0004-637X/745/1/74
Quote Item
The Astrophysical Journal, 745:74 (17pp), 2012 January 20
Collections