THE UNIFICATION OF ASYMMETRY SIGNATURES OF TYPE Ia SUPERNOVAE
- Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej, DK-2100 Copenhagen Oe (Denmark)
- Department of Physics, Florida State University, Tallahassee, FL 32306-4350 (United States)
- ESO-European Organisation for Astronomical Research in the Southern Hemisphere, Karl-Schwarzschild-Str. 2, 85748 Garching (Germany)
- Department of Astronomy and McDonald Observatory, University of Texas, 1 University Station C1402, Austin, TX 78712-0259 (United States)
- Departamento de Astronomia y Astrofisica, PUC Casilla 306, Santiago 22 (Chile)
We present a compilation of the geometry measures acquired using optical and IR spectroscopy and optical spectropolarimetry to probe the explosion geometry of Type Ia supernovae (SNe Ia). Polarization measurements are sensitive to asymmetries in the plane of the sky, whereas line profiles in nebular phase spectra are expected to trace asymmetries perpendicular to the plane of the sky. The combination of these two measures can overcome their respective projection effects, completely probing the structures of these events. For nine normal SNe Ia, we find that the polarization of Si II {lambda}6355 at 5 days before maximum (p{sub Si{sub II}}) is well correlated with its velocity evolution (v-dot{sub Si{sub ii}}), implying that v-dot{sub Si{sub ii}} is predominantly due to the asymmetry of the SNe. We find only a weak correlation between the polarization of Si II and the reported velocities (v{sub neb}) for peak emission of optical Fe II and Ni II lines in nebular spectra. Our sample is biased, with polarization measurements being only available for normal SNe that subsequently exhibited positive (i.e., redshifted) v{sub neb}. In unison these indicators are consistent with an explosion in which the outer layers are dominated by a spherical oxygen layer, mixed with an asymmetric distribution of intermediate-mass elements. The combination of spectroscopic and spectropolarimetric indicators suggests a single geometric configuration for normal SNe Ia, with some of the diversity of observed properties arising from orientation effects.
- OSTI ID:
- 21454887
- Journal Information:
- Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2 Vol. 725; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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