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A STUDY OF CARBON FEATURES IN TYPE Ia SUPERNOVA SPECTRA

J. ParrentDepartment of Physics and Astronomy, 6127 Wilder Laboratory, Dartmouth College, Hanover, NH 03755, USA#TAB#R. C. ThomasPhysics Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USARobert A. FesenDepartment of Physics and Astronomy, 6127 Wilder Laboratory, Dartmouth College, Hanover, NH 03755, USA#TAB#G. H. MarionHarvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USAPeter ChallisHarvard–Smithsonian Center for Astrophysics, 60 Garden#N# Street, Cambridge, MA 02138, USAP. GarnavichPhysics Department, University of Notre Dame, Notre Dame IN 46556, USAD. MilisavljevicDepartment of Physics and Astronomy, 6127 Wilder Laboratory, Dartmouth College, Hanover, NH 03755, USA#TAB#Jozsef VinkoDepartment of Optics and Quantum Electronics, University of Szeged, Dóm tér 9, Szeged H-6720, HungaryJ. Craig WheelerAstronomy Department, University of Texas at Austin, Austin, TX 78712, USA

2011en

ABI

Annotatsiya

One of the major differences between various explosion scenarios of Type Ia supernovae (SNe Ia) is the remaining amount of unburned (C+O) material and its velocity distribution within the expanding ejecta. While oxygen absorption features are not uncommon in the spectra of SNe Ia before maximum light, the presence of strong carbon absorption has been reported only in a minority of objects, typically during the pre-maximum phase. The reported low frequency of carbon detections may be due to low signal-to-noise data, low abundance of unburned material, line blending between C II 6580 and Si II 6355, ejecta temperature differences, asymmetrical distribution effects, or a combination of these. However, a survey of published pre-maximum spectra reveals that more SNe Ia than previously thought may exhibit C II 6580 absorption features and relics of line blending near 6300 Angstroms. Here we present new SN Ia observations where spectroscopic signatures of C II 6580 are detected, and investigate the presence of C II 6580 in the optical spectra of 19 SNe Ia using the parameterized spectrum synthesis code, SYNOW. Most of the objects in our sample that exhibit C II 6580 absorption features are of the low-velocity gradient subtype. Our study indicates that the morphology of carbon-rich regions is consistent with either a spherical distribution or a hemispheric asymmetry, supporting the recent idea that SN Ia diversity may be a result of off-center ignition coupled with observer line-of-sight effects.

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DOI: 10.1088/0004-637x/732/1/30

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