1 / 14

A SALT Spectropolarimetric Survey of Supernovae (“S 4 ”) K. Nordsieck Univ of Wisconsin

A SALT Spectropolarimetric Survey of Supernovae (“S 4 ”) K. Nordsieck Univ of Wisconsin. Supernova taxonomy Polarization of Supernovae Survey Structure Why SALT? Astrophysical questions SNIa Core Collapse SNe. 1993J (IIb). Supernova Importance.

nuri
Download Presentation

A SALT Spectropolarimetric Survey of Supernovae (“S 4 ”) K. Nordsieck Univ of Wisconsin

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. A SALT Spectropolarimetric Survey of Supernovae (“S4”)K. NordsieckUniv of Wisconsin • Supernova taxonomy • Polarization of Supernovae • Survey Structure • Why SALT? • Astrophysical questions • SNIa • Core Collapse SNe 1993J (IIb) SN Survey - SSII

  2. Supernova Importance • Need to understand explosion process to model • return of heavy elements to ISM • energetic input to ISM • Need to clarify progenitors to couple to star formation/ galaxy models • Both I and II’s used for cosmological distance indicators- are they really standard candles? • Some really fun gas dynamics problems • Non spherical explosions a hot theoretical topic- needs observational input! • Possible relation to γ ray bursts SN Survey - SSII

  3. Classification • Currently classified by 2 criteria • Spectra (I, II; a,b,c..) • Light Curves (P = plateau , L = linear) SN Survey - SSII

  4. Past Polarization of Supernovae SN Survey - SSII

  5. What Causes Polarization? • Two possibilities • Scattering of SN light off ambient dust – No, time dependence is wrong • Electron scattering in ejecta – Yes • Electron scattering pseudo-photosphere is asymmetric ~ 10 – 40%  0.5 – 2% pol • Explosion is homologous (Hubble flow). As it expands, see deeper into ejecta, to lower velocities and asymmetry of inner layers • Eventually, becomes optically thin, polarization vanishes • Line polarization • competition of line opacity with e-scat in photosphere  polarization reduction • P-Cygni lines above photosphere => polarization inverse P-Cygni SN Survey - SSII

  6. Good Spectropolarimetry SN Survey - SSII

  7. Survey • We need more than one example in each bin! • Adding asymmetry to spectra and light curve may clarify classification (eg Seyfert I-II unification) • Need • time coverage (3 -4 epochs) for classification and ISP estimation • to get on as early as possible (I highest pol, II unpol) • low resolution (R < 1000), very high S/N • can be done in poor seeing and bright/ grey moon SN Survey - SSII

  8. Why SALT? • Spectroscopic survey distributed over sky – the best kind for SALT/ HET telescopes • Spectropolarimeter ~2x more sensitive than Keck LRS, VLT FORS1 • Polarimeter always available • 100% queue mode- can get on quickly, schedule epochs optimally SN Survey - SSII

  9. Time estimation • Want to go down ~ 3 mag from peak • Use 900 l/mm VPH (R ~ 1000), binning to lower polarimetric resolution as required • => Faintest peak mag < 16 • Using discovery rate/yr for last 12 yrs, will see 10 – 20/year • Run for 3 years to get statistics • 20/ year x 4 epochs = 80 tracks = 8 nights = 3% of SALT • Soliciting SALT collaborators! SN Survey - SSII

  10. Astrophysical questions - Ia • Ia’s claimed to be a one-parameter family: pk luminosity vs decline rate • Theoretical explanation: as time of deflagration  detonation gets earlier, get incomplete combustion, less Ni, lower lum, faster decline • But there must be a variety of progenitors, from accretion disk to WD mergers: how do these lead to one-parameter family • Clue from asymmetry: mergers should give more • The one low-lum Ia is more polarized than the one hi-lum one! SN Survey - SSII

  11. Astrophysical Questions – Core Collapse • There are a variety of ways to induce asymmetry: • asymmetric explosion (axisymmetric? jet?) • ejecta running into asymmetrical environment (axisymmetric) • burning nonuniformities that make Ni clumps (non-axisymmetric) • Do II’s with different H envelope masses and environments all have the same asymmetry source? • Some are axisymmetric and some are not! SN Survey - SSII

  12. SN 1993J (IIb) Tran et al 1997 PASP 109, 489 SN Survey - SSII

  13. SN 2001el (Ia) Model Flux % Pol Ca jet axis Vector Continuum axis Kasen et al 2003 ApJ 593, 788 SN Survey - SSII

  14. SN 1999em (II-P) Flux Spectral symmetry Time variability Leonard et al 2001 ApJ 553, 861 SN Survey - SSII

More Related