# Presentation: 415703

## SciDACComputational Astrophysics Consortium Supernovae & GRB’sWhere Theory Meets Observation

- Peter Nugent
- Lawrence Berkeley National Laboratory

## Why Bother Studying Supernovae? 

**The DoE is very interested in them:**
**Supernovae are responsible for almost all the elements in the universe beyond Helium **
**They comprise the largest explosions in the universe of both the thermonuclear and core-collapse variety**
**Fundamental in the study of particle physics (neutrinos, cosmic rays, etc.)**
**Can be used to determine distances to 7% across the visible universe, thus key to measuring the acceleration history of the universe and dark energy!**
**DoE is now involved in four major experiments in the next decade to study dark energy via supernovae: SN Factory, SNAP, LSST, DES....and btw we still don’t know exactly how they explode or what their progenitors are.**

## Introduction to Spectrum Synthesis 

**Spectrum synthesis is the computation of a theoretical spectrum of a model atmosphere based upon the *****known laws of physics*****. The differences seen between various methods can be boiled down to two points:**
**Which laws of physics you use,  approximate or disregard **
**What was the underlying model atmosphere**
**The goals of spectrum synthesis for supernovae are three-fold:**
**Calculate the spectra of detailed explosion models, compare with observations and falsify or validate the models**
**Calculate various “toy models” in order to predict or explain a set of observations**
**Parameterize a model atmosphere and calculate the subsequent spectra, compare these directly to observation in order to measure nucleosynthesis products and luminosities (and hence the distance to the supernova). **
***At the end of the day spectrum synthesis is a high-end Vis product....***

## Supernovae Physics

**Fundamentally there are two types of supernovae:**
**Thermonuclear - Type Ia**
**Core Collapse - Type II (P,L,n)  & I b/c**

## Supernovae Classification

**Supernovae Classification**

**They are primarily classified based on spectroscopy near peak brightness and subsequently on their photometric evolution.  **
**Hydrogen (Type II) / No Hydrogen (Type I)**

- Type IIP - Plateau lightcurve
- Type IIL - Linear lightcurve
- Type IIn - narrow H lines

- Type Ia - Strong Si II and S II lines
- Type Ib - Weak Si II and He I lines
- Type Ic - Weak Si II (GRB-SNe)

## Supernova Spectra

**Supernovae explode at velocities that are a significant fraction of the speed of light (0.05 - 0.20 c).**
**Their spectra are dominated by P-cygni line profiles, often complicated by the fact that many profiles lie on top of each other.**

## The Codes

**We employ 3 different codes to study the spectra. Each has its advantages and disadvantages in the understanding of these objects. Most of the time it is a trade-off between dimensions+physics versus speed.**
***SYNOW/MADSYN*****  - 1-D, Simplified Physics, Model Atmospheres**
**(very quick line identification & velocity determination)**
***SEDONA***** - 3-D, Simplified Physics, Model Atmospheres**
**(what effects geometry has on determining distances to SNe)**
***PHOENIX****** - *****1-D, Full Physics, Spectrum Synthesis**
**(can we make SNe better for distances/cosmology)**

## PHOENIX

***PHOENIX***** is a state-of-the-art spectrum synthesis code which is currently in 1-D. It treats all the applicable micro-physics appropriately and has been used to model supernovae of all types, the sun, novae, cool stars, red-giants, quasars and active galactic nuclei.**
**Input: Luminosity, Abundances, Density and Velocity Profiles and Non-Thermal Ionization from radioactive Ni, Co, etc.**
**Each of the above inputs range by an order of magnitude for SNe. 100 spatial zones, 300k wavelength points, energy conservation and non-LTE for 50 ionic species.**

## General Model Assumptions

**Full treatment of special relativistic radiative transfer in spherical geometry for all lines and continua,**
**Radiative equilibrium in the Lagrangian frame (including all velocity terms),**
**Full non-LTE treatment of most ions.**
**Detailed profiles for the lines, fluorescence effects are included in the NLTE treatment**
**Equation of state used includes up to 26 ionization stages of 40 elements as well as up to 206 molecules.**

## Atomic Data

**Atomic Data**

**Example Grotrian diagram for Fe II: **
**617 Levels - 1.2 million total lines**
**The level populations off all species are solved simultaneously as a very large set of linear equations, in **
***256-bit precision*****! **
**This is due to the fact that there is a very large dynamic range in the level populations across ionization stages throughout the atmosphere.**
**Population **

**In order to implement this we have employed Super-LU + the quad-double packages developed by other members of CRD. Full runs on NERSC’s IBM SP take ~ 1000 hrs.**

**All relevant b-f and f-f transitions are included - atomic line blanketing: about 2*10****6**** lines dynamically selected from the Kurucz line list.**

## Results: Spectral Templates

***K*****-corrections - How we compare supernovae at different redshifts. Especially in the UV...**

**The spectral templates were created by homogenizing IUE and HST observations + modeling to fill in the gaps. **

## Spectral Templates for Type Ia Cosmology...

**Spectral Templates for Type Ia Cosmology...**

**Aphrodite (z~1.3) from the Riess *****et al.***** GOODs Very High-Z SN Search**

**Precision measurements from Knop *****et al.***** HST data**

**SN 1997ff, still the highest redshift SN Ia observed to date from Riess, Nugent, *****et al.***

## Type Ia Systematics - Metallicity

**Synthetic spectra from Lentz *****et al*****., based on explosion models by Höflich *****et al.***** **
**Metallicity effects the UV.**

## Observed Metallicity....

**Nugent et al. HST/STIS studies of the UV...**

## Metallicity and Cosmology

**Understanding the UV has large implications for cosmology.**
**Intrinsic color and corrections for dust get intertwined. **

- Ω

- ΩM

**UV - suppressed**
** **
**UV - enhanced**

## Type IIP Supernovae and Cosmology

**Type IIP Supernovae and Cosmology**

**Detailed spectrum synthesis modeling has allowed us to determine a way to make the first Hubble diagram of Type IIP supernovae at high-redshift. These supernovae are found for “free” in rolling searches and provide a completely independent method for measuring the cosmological parameters.**

## SEDONA & 3-D Effects

**SEDONA is a relatively simple code from the physics standpoint. A Monte Carlo code (follow the photons out) incorporating  LTE and a 2-level atom. It iteratively solves for the temperature structure and calculates the polarization due to electron scattering  and scattering off of lines.**
**Developed to model the output of the previous SciDAC Supernova Programs.**
**Input: Luminosity, Abundances, Density and Velocity Profiles**
**300x300x300 spatial zones, 2-4k wavelength points, energy **
**conservation and an atomic linelist of ~500k transitions. **
**10****10**** photons to converge in energy **
**10****14**** photons for spectropolarimetry**
**Full runs calculated on NERSC’s IBM SP take ~50,000 hrs.**

## SEDONA for SN 2001el

**We need the large number of photons since:**
**Polarization is low < 1%**
**Atmosphere changes quickly on short scales (both in time and space)**
**Many lines to interact with...**

## A Hole in Type Ia Supernovae?

**A White Dwarf accretes material from a companion star, either a main sequence Star or a Red Giant.**

** ****The companion subtends an angle ~40****o****.**
** ****After explosion, the SN ejecta runs over the companion star in a few minutes to hours.**
** ****This may leave a ~40****o ****hole in the SN ejecta . (Marietta *****et. al.***** 2000; c.f. Livne *****et. al.***** 1996)**

## A Hole in Type Ia Supernovae?

## SEDONA Model of SN Ia

## Effect on Cosmology?

## INCITE & Gravitationally Confined SN Ia Detonations

**INCITE & Gravitationally Confined SN Ia Detonations**

**The spectrum synthesis of the Incite model compares favorably to observations and may be the first explosion model which “naturally” explains the transition from deflagration to detonation in thermonuclear supernovae.**

## SYNOW/MADSYN

**Input for the photosphere:**
** ****Temperature**
** ****Velocity**
** ****Density (exp or pwr law)**
**Input for the lines:**
** ****Optical depth**
** ****Min and Max velocity**
** ****T****eff**

**SYNOW employs the Sobolev approximation for the line transfer, as well as a “hard” photosphere and equivalent 2-level atoms in LTE.**
**Highly parameterized and very fast.**
**Runs in < 10 sec, almost all time is spent reading Kurucz linelist.**

## Real-Time Assessment of Data for SN Factory/SNAP 

**Real-Time Assessment of Data for SN Factory/SNAP **

**Joins the expertise in optimization research with that of spectrum synthesis. **
**Makes it possible to”objectively” fit a spectrum and determine the parameters of the model atmosphere and their uncertainties.**

## Conclusions

-  **Many great nearby & high-redshift programs underway now**
** ****--- All will rely on computational modeling to improve our understanding of supernovae and to constrain systematics.**
** ****The CAC is exploring the explosion mechanisms of supernovae --- 3-D spectrum synthesis will be the only way to confront these calculations with observation. **
** ****Understanding/Constraining 3-D effects will be important for ****	****“precision” cosmology --- all future SNe experiments**
** ****We need much better methods than the Chi-by-eye used now to compare and contrast models with observation via spectrum synthesis **

## Conclusions (continued...)

- The data coming from both the observations and the models are quite large...
- Tb’s for the hydro explosion models, which are input for the spectrum synthesis models, which then produce Mb’s of data at each time-step for 100 days.